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Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
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We encourage you to perform a real-time search of NLEBeta
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1

Effects of turbulence on power generation for variable-speed wind turbines  

DOE Green Energy (OSTI)

One of the primary advantages of variable-speed wind turbines over fixed-speed turbines should be improved aerodynamic efficiency. With variable-speed generation, in order to maintain a constant ratio of wind speed to tip speed, the wind turbine changes rotor speed as the wind speed changes. In this paper we compare a stall-controlled, variable-speed wind turbine to a fixed-speed turbine. The focus of this paper is to investigate the effects of variable speed on energy capture and its ability to control peak power. We also show the impact of turbulence on energy capture in moderate winds. In this report, we use a dynamic simulator to apply different winds to a wind turbine model. This model incorporates typical inertial and aerodynamic performance characteristics. From this study we found a control strategy that makes it possible to operate a stall-controlled turbine using variable speed to optimize energy capture and to control peak power. We also found that turbulence does not have a significant impact on energy capture.

Muljadi, E.; Butterfield, C.P.; Buhl, M.L. Jr.

1996-11-01T23:59:59.000Z

2

Supercomputers Capture Turbulence in the Solar Wind  

NLE Websites -- All DOE Office Websites (Extended Search)

Supercomputers Capture Turbulence in the Solar Wind Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space...

3

Wind turbulence characterization for wind energy development  

DOE Green Energy (OSTI)

As part of its support of the US Department of Energy's (DOE's) Federal Wind Energy Program, the Pacific Northwest Laboratory (PNL) has initiated an effort to work jointly with the wind energy community to characterize wind turbulence in a variety of complex terrains at existing or potential sites of wind turbine installation. Five turbulence characterization systems were assembled and installed at four sites in the Tehachapi Pass in California, and one in the Green Mountains near Manchester, Vermont. Data processing and analyses techniques were developed to allow observational analyses of the turbulent structure; this analysis complements the more traditional statistical and spectral analyses. Preliminary results of the observational analyses, in the rotating framework or a wind turbine blade, show that the turbulence at a site can have two major components: (1) engulfing eddies larger than the rotor, and (2) fluctuating shear due to eddies smaller than the rotor disk. Comparison of the time series depicting these quantities at two sites showed that the turbulence intensity (the commonly used descriptor of turbulence) did not adequately characterize the turbulence at these sites. 9 refs., 10 figs.,

Wendell, L.L.; Gower, G.L.; Morris, V.R.; Tomich, S.D.

1991-09-01T23:59:59.000Z

4

Supercomputers Capture Turbulence in the Solar Wind  

NLE Websites -- All DOE Office Websites (Extended Search)

Provide Web Site Feedback: info@es.net Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space...

5

Effects of wind shear and turbulence on wind turbine power curves  

DOE Green Energy (OSTI)

It is a common practice to use wind speeds at hub height in determining wind turbine power curves. Although the possible influence of other variables (sub as turbulence and wind shear) is generally neglected in power curve measurements, we discovered the importance of other variables in an analysis of power curves for three 2.5 MW wind turbines. When the power curves were stratified by turbulence intensity. Such a large sensitivity to turbulence was not expected, and further analyses were conducted to determine if other factors accompanying the change in turbulence level could cause or contribute to the observed sensitivity of the power curves to turbulence. In summary, the sensitivity of the observed power curves was largely due to two factors: (1) an actual sensitivity to turbulence in determining the power curve and (2) the deviation of the disk-averaged velocity from the hub-height velocity under low turbulence conditions that were most prevalent at the site. An examination of the wind shear profiles over the height of the rotor disk revealed that low turbulence conditions were characterized by strong shear in the lower half of the rotor disk and weak or negative shear in the upper half. Implications of this analysis are that significant errors in power curve measurements can result if the effects of wind shear and turbulence are ignored. 7 refs., 6 figs.

Elliott, D.L. (Pacific Northwest Lab., Richland, WA (USA)); Cadogan, J.B. (USDOE, Washington, DC (USA))

1990-09-01T23:59:59.000Z

6

Solar Wind Turbulence A Study of Corotating Interaction Regions at 1 AU  

E-Print Network (OSTI)

Solar Wind Turbulence A Study of Corotating Interaction Regions at 1 AU Je rey A. Tessein Department of Physics University of New Hampshire Durham, NH 03824 May 15, 2009 #12;Abstract The solar wind's rotation and the variability in the source of the solar wind, fast moving wind can crash into slow wind

New Hampshire, University of

7

k-? turbulence modeling for a wind turbine.  

E-Print Network (OSTI)

?? In this report we discuss the use of k-? RANS (Reynolds-averaged Navier-Stokes equations) turbulence model for wind turbine applications. This model has been implemented… (more)

EREK, ERMAN

2011-01-01T23:59:59.000Z

8

Supercomputers Capture Turbulence in the Solar Wind  

NLE Websites -- All DOE Office Websites (Extended Search)

Supercomputers Supercomputers Capture Turbulence in the Solar Wind Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space weather December 16, 2013 Linda Vu, +1 510 495 2402, lvu@lbl.gov eddies1.jpg This visualization zooms in on current sheets revealing the "cascade of turbulence" in the solar wind occurring down to electron scales. This is a phenomenon common in fluid dynamics-turbulent energy injected at large eddies is transported to successively smaller scales until it is dissipated as heat. (Image by Burlen Loring, Berkeley Lab) As inhabitants of Earth, our lives are dominated by weather. Not just in the form of rain and snow from atmospheric clouds, but also a sea of charged particles and magnetic fields generated by a star sitting 93

9

Turbulent Spectra in the Solar Wind Plasma  

E-Print Network (OSTI)

Observations of interstellar scintillations at radio wavelengths reveal a Kolmogorov-like scaling of the electron density spectrum with a spectral slope of -5/3 over six decades in wavenumber space. A similar turbulent density spectrum in the solar wind plasma has been reported. The energy transfer process in the magnetized solar wind plasma over such extended length-scales remains an unresolved paradox of modern turbulence theories raising the especially intriguing question of how a compressible magnetized solar wind exhibits a turbulent spectrum that is a characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfv\\'enic, supersonic and strongly magnetized plasma. It is shown that the observed Kolmogorov-like (-5/3) spectrum can develop in the solar wind plasma by supersonic plasma motions that dissipate into highly subsonic motion that passively ...

Shaikh, Dastgeer

2009-01-01T23:59:59.000Z

10

Inflow Turbulence Energy and its Spatial Distribution on a Wind Turbine  

E-Print Network (OSTI)

Inflow Turbulence Energy and its Spatial Distribution on a Wind Turbine Christopher Wright Dr caused the most variability of turbulence energy while high wind shear exponents caused the least........................................................................................................................ 18 #12;Completion report on our project to empirically evaluate energy distribution in unique spatial

Manuel, Lance

11

Measurement of turbulent wind velocities using a rotating boom apparatus  

DOE Green Energy (OSTI)

The present report covers both the development of a rotating-boom facility and the evaluation of the spectral energy of the turbulence measured relative to the rotating boom. The rotating boom is composed of a helicopter blade driven through a pulley speed reducer by a variable speed motor. The boom is mounted on a semiportable tower that can be raised to provide various ratios of hub height to rotor diameter. The boom can be mounted to rotate in either the vertical or horizontal plane. Probes that measure the three components of turbulence can be mounted at any location along the radius of the boom. Special hot-film sensors measured two components of the turbulence at a point directly in front of the rotating blade. By using the probe rotated 90/sup 0/ about its axis, the third turbulent velocity component was measured. Evaluation of the spectral energy distributions for the three components of velocity indicates a large concentration of energy at the rotational frequency. At frequencies slightly below the rotational frequency, the spectral energy is greatly reduced over that measured for the nonrotating case measurements. Peaks in the energy at frequencies that are multiples of the rotation frequency were also observed. We conclude that the rotating boom apparatus is suitable and ready to be used in experiments for developing and testing sensors for rotational measurement of wind velocity from wind turbine rotors. It also can be used to accurately measure turbulent wind for testing theories of rotationally sampled wind velocity.

Sandborn, V.A.; Connell, J.R.

1984-04-01T23:59:59.000Z

12

Supercomputers Capture Turbulence in the Solar Wind  

NLE Websites -- All DOE Office Websites (Extended Search)

Supercomputers Capture Supercomputers Capture Turbulence in the Solar Wind News & Publications ESnet in the News ESnet News Media & Press Publications and Presentations Galleries ESnet Awards and Honors Contact Us Technical Assistance: 1 800-33-ESnet (Inside the US) 1 800-333-7638 (Inside the US) 1 510-486-7600 (Globally) 1 510-486-7607 (Globally) Report Network Problems: trouble@es.net Provide Web Site Feedback: info@es.net Supercomputers Capture Turbulence in the Solar Wind Berkeley Lab visualizations could help scientists forecast destructive space weather December 16, 2013 | Tags: ESnet News, National Energy Research Scientific Computing Linda Vu, +1 510 495 2402, lvu@lbl.gov eddies1.jpg This visualization zooms in on current sheets revealing the "cascade of turbulence" in the solar wind occurring down to electron scales. This is

13

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind  

E-Print Network (OSTI)

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind C. S. Ng Center for Magnetic (MHD) turbulence Observations in ISM and solar wind · Anisotropy due to magnetic field · Electron MHD turbulence #12;Interstellar turbulence From Cordes (1999) Observation: power law relation between electron

Ng, Chung-Sang

14

Turbulent Density Spectrum in Solar Wind Plasma  

E-Print Network (OSTI)

The density fluctuation spectrum in the solar wind reveals a Kolmogorov-like scaling with a spectral slope of -5/3 in wavenumber space. The energy transfer process in the magnetized solar wind, characterized typically by MHD turbulence, over extended length-scales remains an unresolved paradox of modern turbulence theories, raising the question of how a compressible magnetofluid exhibits a turbulent spectrum that is characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfv\\'enic, supersonic and strongly magnetized plasma fluid. It is shown that a Kolmogorov-like density spectrum can develop by plasma motions that are dominated by Alfv\\'enic cascades whereas compressive modes are dissipated.

Shaikh, Dastgeer

2009-01-01T23:59:59.000Z

15

Can Wind Lidars Measure Turbulence?  

Science Conference Proceedings (OSTI)

Modeling of the systematic errors in the second-order moments of wind speeds measured by continuous-wave (ZephIR) and pulsed (WindCube) lidars is presented. These lidars use the conical scanning technique to measure the velocity field. The model ...

A. Sathe; J. Mann; J. Gottschall; M. S. Courtney

2011-07-01T23:59:59.000Z

16

Surface Wind Direction Variability  

Science Conference Proceedings (OSTI)

Common large shifts of wind direction in the weak-wind nocturnal boundary layer are poorly understood and are not adequately captured by numerical models and statistical parameterizations. The current study examines 15 datasets representing a ...

Larry Mahrt

2011-01-01T23:59:59.000Z

17

Effects of Wind Turbulence on Coherent Doppler Lidar Performance  

Science Conference Proceedings (OSTI)

The effects of wind turbulence on pulsed coherent Doppler lidar performance are investigated theoretically and with computer simulations. The performance of velocity estimators is determined for the case of a single realization of a wind field ...

Rod Frehlich

1997-02-01T23:59:59.000Z

18

Numerical simulations to study solar wind turbulence  

Science Conference Proceedings (OSTI)

Numerical simulation of coupled equations of kinetic Alfven wave (KAW) and ion acoustic wave is presented in the solar wind. The nonlinear dynamical equations satisfy the modified Zakharov system of equations by taking the nonadiabatic response of the background density. The ponderomotive nonlinearity is incorporated in the wave dynamics. The effect of Landau damping of KAW is taken into account. Localization of magnetic field intensity and the wavenumber spectra (perpendicular and parallel) of magnetic fluctuations are studied in solar plasmas around 1 a.u. Our results reveal the formation of damped localized structures and the steeper spectra that are in good agreement with the observations. These damped structures and steeper turbulent spectra can be responsible for plasma heating and particle acceleration in solar wind.

Sharma, R. P.; Sharma, Nidhi; Kumar, Sanjay [Centre for Energy Studies, Indian Institute of Technology Delhi, Delhi 110016 (India); Kumar, Sachin [Department of Applied Sciences and Humanities, Ajay Kumar Garg Engineering College, Ghaziabad 201009 (India); Singh, H. D. [Department of Physical Sciences, School of Physical and Chemical Sciences, Sikkim University, Sikkim 737102 (India)

2011-02-15T23:59:59.000Z

19

Identification of Wind Turbine Response to Turbulent Inflow Structures: Preprint  

DOE Green Energy (OSTI)

The National Renewable Energy Laboratory conducted an experiment to obtain detailed wind measurements and corresponding wind turbine measurements in order to establish a causal relationship between coherent turbulent structures and wind turbine blade fatigue loads. Data were collected for one entire wind season from October 2000 to May 2001. During this period, the wind turbine operated under atmospheric conditions that support the formation of coherent turbulent structures 31% of the time. Using the equivalent fatigue load parameter as a measure of wind turbine blade fatigue and using statistical measures of the turbulent fluctuations of the wind, general correlation between the turbulence and the wind turbine response is shown. Direct correlation cannot be resolved with 10-minute statistics for several reasons. Multiple turbulent structures can exist within a 10-minute record, and the equivalent fatigue load parameter is essentially a 10-minute statistic that cannot estimate turbine response to individual turbulent structures. Large-magnitude turbulent fluctuations in the form of instantaneous Reynolds stresses do not necessarily correspond directly to large-magnitude blade root moment amplitudes. Thus, additional work must be done to quantify the negative turbine response and to correlate this response to turbulent inflow parameters over time scales less than 10 minutes.

Hand, M. M.; Kelley, N. D.; Balas, M. J.

2003-06-01T23:59:59.000Z

20

Wind Scanner: A full-scale Laser Facility for Wind and Turbulence Measurements around large Wind Turbines  

E-Print Network (OSTI)

Wind Scanner: A full-scale Laser Facility for Wind and Turbulence Measurements around large Wind Turbines Torben Mikkelsen, Jakob Mann and Michael Courtney Wind Energy Department, Risø National Laboratory:Torben.Mikkelsen@Risoe.dk Summary RIS� DTU has started to build a newly designed laser-based lidar scanning facility for remote wind

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

COLLISIONLESS DAMPING AT ELECTRON SCALES IN SOLAR WIND TURBULENCE  

SciTech Connect

The dissipation of turbulence in the weakly collisional solar wind plasma is governed by unknown kinetic mechanisms. Two candidates have been suggested to play an important role in the dissipation, collisionless damping via wave-particle interactions and dissipation in small-scale current sheets. High resolution spacecraft measurements of the turbulent magnetic energy spectrum provide important constraints on the dissipation mechanism. The limitations of popular fluid and hybrid numerical schemes for simulation of the dissipation of solar wind turbulence are discussed, and instead a three-dimensional kinetic approach is recommended. We present a three-dimensional nonlinear gyrokinetic simulation of solar wind turbulence at electron scales that quantitatively reproduces the exponential form of the turbulent magnetic energy spectrum measured in the solar wind. A weakened cascade model that accounts for nonlocal interactions and collisionless Landau damping also quantitatively agrees with the observed exponential form. These results establish that a turbulent cascade of kinetic Alfven waves that is terminated by collisionless Landau damping is sufficient to explain the observed magnetic energy spectrum in the dissipation range of solar wind turbulence.

TenBarge, J. M.; Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Dorland, W., E-mail: jason-tenbarge@uiowa.edu [Department of Physics, University of Maryland, College Park, MA 20742-3511 (United States)

2013-09-10T23:59:59.000Z

22

Generalized similarity in finite range solar wind magnetohydrodynamic turbulence  

E-Print Network (OSTI)

Extended or generalized similarity is a ubiquitous but not well understood feature of turbulence that is realized over a finite range of scales. ULYSSES spacecraft solar polar passes at solar minimum provide \\textit{in situ} observations of evolving anisotropic magnetohydrodynamic turbulence in the solar wind under ideal conditions of fast quiet flow. We find a single generalized scaling function characterises this finite range turbulence and is insensitive to plasma conditions. The recent unusually inactive solar minimum -with turbulent fluctuations down by a factor of $\\sim 2$ in power- provides a test of this invariance.

Chapman, S C

2009-01-01T23:59:59.000Z

23

Long-Term Wind Power Variability  

DOE Green Energy (OSTI)

The National Renewable Energy Laboratory started collecting wind power data from large commercial wind power plants (WPPs) in southwest Minnesota with dedicated dataloggers and communication links in the spring of 2000. Over the years, additional WPPs in other areas were added to and removed from the data collection effort. The longest data stream of actual wind plant output is more than 10 years. The resulting data have been used to analyze wind power fluctuations, frequency distribution of changes, the effects of spatial diversity, and wind power ancillary services. This report uses the multi-year wind power data to examine long-term wind power variability.

Wan, Y. H.

2012-01-01T23:59:59.000Z

24

Generation of residual energy in the turbulent solar wind  

SciTech Connect

In situ observations of the fluctuating solar wind flow show that the energy of magnetic field fluctuations always exceeds that of the kinetic energy, and therefore the difference between the kinetic and magnetic energies, known as the residual energy, is always negative. The same behaviour is found in numerical simulations of magnetohydrodynamic turbulence. We study the dynamics of the residual energy for strong, anisotropic, critically balanced magnetohydrodynamic turbulence using the eddy damped quasi-normal Markovian approximation. Our analysis shows that for stationary critically balanced magnetohydrodynamic turbulence, negative residual energy will always be generated by nonlinear interacting Alfven waves. This offers a general explanation for the observation of negative residual energy in solar wind turbulence and in the numerical simulations.

Gogoberidze, G. [Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom); Institute of Theoretical Physics, Ilia State University, 3/5 Cholokashvili Ave., 0162 Tbilisi (Georgia); Chapman, S. C.; Hnat, B. [Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom)

2012-10-15T23:59:59.000Z

25

A Tree Swaying in a Turbulent Wind: A Scaling Analysis  

E-Print Network (OSTI)

A tentative scaling theory is presented of a tree swaying in a turbulent wind. It is argued that the turbulence of the air within the crown is in the inertial regime, An eddy causes a dynamic bending response of the branches according to a time criterion. The resulting expression for the penetration depth of the wind yields an exponent which is in agreement with that pertaining to the morphology of the tree branches. An energy criterion shows that the dynamics of the branches is basically passive. The possibility of hydrodynamic screening by the leaves is discussed.

Theo Odijk

2013-05-29T23:59:59.000Z

26

Estimation of turbulence level and scale for wind turbine applications  

DOE Green Energy (OSTI)

A simplified method is presented for estimating onsite turbulence variance within the wind turbine layer for horizontal wind speed. The method is based principally on estimating the probability distribution of wind speed and assigning a variance to each mean wind speed based on surface roughness estimates. The model is not proposed as an alternative to onsite measurement and analysis, but rather as an adjunct to such a program. A revision of the Kaimal neutral u-component spectrum is suggested to apply to the mix of the stabilities occurring during operational winds. Values of integral length scale calculated from data analysis are shown to contradict the length scale model implicit in turbulence power spectra. Also, these calculated values are shown to be extremely sensitive to the length of the time series and the detrending method used. The analysis and modeling are extended to the rotational frame of reference for a horizontal-axis wind turbine by modeling the ratios of harmonic spike variances (1P, 2P, etc.) in the rotational spectrum to the Eulerian turbulence variance. 15 refs., 11 figs., 3 tabs.

Powell, D.C.

1988-11-01T23:59:59.000Z

27

Using a new characterization of turbulent wind for accurate correlation of wind turbine response with wind speed  

SciTech Connect

The turbulence encountered by a point on a rotating wind turbine blade has characteristics that in some important respects are different from those measured by a stationary anemometer. The conventional one-peaked continuous spectrum becomes, broadly, a two-peaked spectrum that in addition contains a set of narrow-band spikes of turbulence energy, one centered on the frequency of rotor rotation and the others centered on multiples of that frequency. The rotational sampling effect on wind spectra is quantified using measurements of wind velocity by anemometers on stationary crosswind circular arrays. Characteristics of fluctuating wind are compared to measured fluctuations of bending moments of the rotor blades and power output fluctuations of a horizontal-axis wind turbine at the same site. The wind characteristics and the correlations between wind fluctuations and wind turbine fluctuations provide a basis for improving turbine design, siting, and control. 6 refs., 11 figs., 1 tab.

Connell, J.R.; George, R.L.

1987-09-01T23:59:59.000Z

28

Turbulent heating of the corona and solar wind: the heliospheric  

E-Print Network (OSTI)

of telegraph services - Once per 500 years (ice cores) - Solar-terrestrial connection - Interplanetary space of radiators - Dust environment - Cp/Cg problems - Solar panels and power #12;Solar Probe Plus 2018 launch 35Turbulent heating of the corona and solar wind: the heliospheric dark energy problem Stuart D. Bale

29

Residual energy in magnetohydrodynamic turbulence and in the solar wind  

E-Print Network (OSTI)

Recent observations indicate that kinetic and magnetic energies are not in equipartition in the solar wind turbulence. Rather, magnetic fluctuations are more energetic and have somewhat steeper energy spectrum compared to the velocity fluctuations. This leads to the presence of the so-called residual energy E_r=E_v-E_b in the inertial interval of turbulence. This puzzling effect is addressed in the present paper in the framework of weak turbulence theory. Using a simple model of weakly colliding Alfv\\'en waves, we demonstrate that the kinetic-magnetic equipartition indeed gets broken as a result of nonlinear interaction of Alfv\\'en waves. We establish that magnetic energy is indeed generated more efficiently as a result of these interactions, which proposes an explanation for the solar wind observations.

Stanislav Boldyrev; Jean Carlos Perez; Vladimir Zhdankin

2011-08-30T23:59:59.000Z

30

The Probability Distribution of Sea Surface Wind Speeds: Effects of Variable Surface Stratification and Boundary Layer Thickness  

Science Conference Proceedings (OSTI)

Air–sea exchanges of momentum, energy, and material substances of fundamental importance to the variability of the climate system are mediated by the character of the turbulence in the atmospheric and oceanic boundary layers. Sea surface winds ...

Adam Hugh Monahan

2010-10-01T23:59:59.000Z

31

Modelling the Vertical Wind Speed and Turbulence Intensity Profiles at Prospective Offshore Wind Farm Sites  

E-Print Network (OSTI)

Monin-Obukhov theory predicts the well-known log-linear form of the vertical wind speed profile. A turbulence intensity profile can be estimated from this by assuming that the standard deviation of the wind speed is proportional to the friction velocity. Two parameters, namely the aerodynamic surface roughness length and the MoninObukhov length, are than needed to predict the vertical wind speed and turbulence intensity profiles from a measurement at one height. Different models to estimate these parameters for conditions important for offshore wind energy utilisation are compared and tested: Four models for the surface roughness and three methods to derive the Monin-Obukov-length from measurements. They have been tested with data from the offshore field measurement Rdsand by extrapolating the measured 10 m wind speed to 50 m height and comparing it with the measured 50 m wind speed.

Bernhard Lange; Sřren Larsen; Jřrgen Hřjstrup; Rebecca Barthelmie; Ulrich Focken

2002-01-01T23:59:59.000Z

32

Measurements of Wind and Turbulence Profiles with Scanning Doppler Lidar for Wind Energy Applications  

SciTech Connect

High-quality profiles of mean and turbulent statistics of the wind field upstream of a wind farm can be produced using a scanning Doppler lidar. Careful corrections for the spatial filtering of the wind field by the lidar pulse produce turbulence estimates equivalent to point sensors but with the added advantage of a larger sampling volume to increase the statistical accuracy of the estimates. For a well-designed lidar system, this permits accurate estimates of the key turbulent statistics over various subdomains and with sufficiently short observation times to monitor rapid changes in conditions. These features may be ideally suited for optimal operation of wind farms and also for improved resource assessment of potential sites.

Frehlich, R.; Kelley, N.

2008-03-01T23:59:59.000Z

33

Remote Measurement of Turbulent Wind Spectra by Heterodyne DopplerLidar Technique  

Science Conference Proceedings (OSTI)

Heterodyne Doppler lidars (HDLs) are used to monitor atmospheric wind field and wind turbulence at remote distance. This last application calls for the derivation of wind spectra, which can be characterized by the dissipation rate and the ?-...

Philippe Drobinski; Alain M. Dabas; Pierre H. Flamant

2000-12-01T23:59:59.000Z

34

Mesoscale Time and Space Wind Variability  

Science Conference Proceedings (OSTI)

The results of a program to study the time and space variability of the wind field below 5 km are presented. Wind data were collected using pilot balloons tracked with the METRAC positioning system. Balloons were launched at 10-30 min intervals ...

W. H. Jasperson

1982-06-01T23:59:59.000Z

35

Global Variability of the Wavenumber Spectrum of Oceanic Mesoscale Turbulence  

Science Conference Proceedings (OSTI)

The wavenumber spectra of sea surface height from satellite altimeter observations have revealed complex spatial variability that cannot be explained by a universal theory of mesoscale turbulence. Near the edge of the core regions of high eddy ...

Yongsheng Xu; Lee-Lueng Fu

2011-04-01T23:59:59.000Z

36

Parallel Electric Field Spectrum of Solar Wind Turbulence  

E-Print Network (OSTI)

By searching through more than 10 satellite-years of THEMIS and Cluster data, three reliable examples of parallel electric field turbulence in the undisturbed solar wind have been found. The perpendicular and parallel electric field spectra in these examples have similar shapes and amplitudes, even at large scales (frequencies below the ion gyroscale) where Alfvenic turbulence with no parallel electric field component is thought to dominate. The spectra of the parallel electric field fluctuations are power laws with exponents near -5/3 below the ion scales (~ 0.1 Hz), and with a flattening of the spectrum in the vicinity of this frequency. At small scales (above a few Hz), the spectra are steeper than -5/3 with values in the range of -2.1 to -2.8. These steeper slopes are consistent with expectations for kinetic Alfven turbulence, although their amplitude relative to the perpendicular fluctuations is larger than expected.

Mozer, F S

2013-01-01T23:59:59.000Z

37

Wind Shear and Turbulence Profiles at Elevated Heights: Great Lakes and Midwest Sites (Poster)  

DOE Green Energy (OSTI)

Analyzed wind resource characteristics at elevated heights (50 m-200+m) incuding shear and turbulence profiles for some areas of the Great Lakes and M idwest sites.

Elliott, D.; Schwartz, M.; Scott, G.

2009-05-01T23:59:59.000Z

38

Velocity-Space Proton Diffusion in the Solar Wind Turbulence  

E-Print Network (OSTI)

We study a velocity-space quasilinear diffusion of the solar wind protons driven by oblique Alfven turbulence at proton kinetic scales. Turbulent fluctuations at these scales possess properties of kinetic Alfven waves (KAWs) that are efficient in Cherenkov resonant interactions. The proton diffusion proceeds via Cherenkov kicks and forms a quasilinear plateau - nonthermal proton tail in the velocity distribution function (VDF). The tails extend in velocity space along the mean magnetic field from 1 to (1.5-3) VA, depending on the spectral break position, turbulence amplitude at the spectral break, and spectral slope after the break. The most favorable conditions for the tail generation occur in the regions where the proton thermal and Alfven velocities are about the same, VTp/VA = 1. The estimated formation times are within 1-2 h for typical tails at 1 AU, which is much shorter than the solar wind expansion time. Our results suggest that the nonthermal proton tails, observed in-situ at all heliocentric distan...

Voitenko, Yuriy

2013-01-01T23:59:59.000Z

39

Multi-winding Homopolar Electric Machine Offers Variable Voltage ...  

Wind Energy Industrial Technologies Multi-winding Homopolar Electric Machine Offers Variable Voltage at Low Rotational Speed Oak Ridge National Laboratory. Contact ...

40

Comparison of Mean Wind Speeds and Turbulence at a Coastal Site and Offshore Location  

Science Conference Proceedings (OSTI)

Observations of mean wind speed and longitudinal turbulence at a height of 8 m over the Atlantic ocean, 5 km off Long Island, New York, were compared with simultaneous observations at the beach. Results were grouped into wind direction classes ...

S. SethuRaman; G. S. Raynor

1980-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Study of Radiative and Turbulent Processes in the Stable Boundary Layer under Weak Wind Conditions  

Science Conference Proceedings (OSTI)

The role of radiation and turbulence was studied in a weak wind nocturnal inversion layer using a one-dimensional model. In contrast to a strong wind stable boundary layer where cooling within the surface inversion layer is dominated by ...

S. G. Gopalakrishnan; Maithili Sharan; R. T. McNider; M. P. Singh

1998-03-01T23:59:59.000Z

42

User's guide for a personal computer model of turbulence at a wind turbine rotor  

DOE Green Energy (OSTI)

This document is primarily (1) a user's guide for the personal computer (PC) version of the code for the PNL computational model of the rotationally sampled wind speed (RODASIM11) and (2) a brief guide to the growing literature on the subject of rotationally sampled turbulence, from which the model is derived. The model generates values of turbulence experienced by single points fixed in the rotating frame of reference of an arbitrary wind turbine blade. The character of the turbulence depends on the specification of mean wind speed, the variance of turbulence, the crosswind and along-wind integral scales of turbulence, mean wind shear, and the hub height, radius, and angular speed of rotation of any point at which wind fluctuation is to be calculated. 13 refs., 4 figs., 4 tabs.

Connell, J.R.; Powell, D.C.; Gower, G.L.

1989-08-01T23:59:59.000Z

43

THREE-DIMENSIONAL STRUCTURE OF SOLAR WIND TURBULENCE  

SciTech Connect

We present a measurement of the scale-dependent, three-dimensional structure of the magnetic field fluctuations in inertial range solar wind turbulence with respect to a local, physically motivated coordinate system. The Alfvenic fluctuations are three-dimensionally anisotropic, with the sense of this anisotropy varying from large to small scales. At the outer scale, the magnetic field correlations are longest in the local fluctuation direction, consistent with Alfven waves. At the proton gyroscale, they are longest along the local mean field direction and shortest in the direction perpendicular to the local mean field and the local field fluctuation. The compressive fluctuations are highly elongated along the local mean field direction, although axially symmetric perpendicular to it. Their large anisotropy may explain why they are not heavily damped in the solar wind.

Chen, C. H. K.; Bale, S. D. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Mallet, A.; Schekochihin, A. A. [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP (United Kingdom); Horbury, T. S. [Blackett Laboratory, Imperial College London, London SW7 2AZ (United Kingdom); Wicks, R. T., E-mail: chen@ssl.berkeley.edu [Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-10-20T23:59:59.000Z

44

Modeling the Variability of Sydney Harbor Wind Measurements  

Science Conference Proceedings (OSTI)

The time-dependent behavior in the variability of wind measurements is investigated using bivariate generalized autoregressive conditional heteroscedastic models. These models express the current level of short-timescale wind variability in terms ...

Edward Cripps; William T. M. Dunsmuir

2003-08-01T23:59:59.000Z

45

Variable energy flux in quasi-static magnetohydrodynamic turbulence  

E-Print Network (OSTI)

Experiments and numerical simulations show that the energy spectrum of the magnetohydrodynamic turbulence in the quasi-static limit deviates from Kolmogorov's $k^{-5/3}$ spectrum as the external magnetic field, or equivalently the interaction parameter, is increased. To explain this phenomena, we construct an analytical turbulence model with variable energy flux that arises due to the Lorentz-force induced dissipation. The energy spectra computed using our model for various interaction parameters are in qualitative agreement with earlier experimental and numerical results.

Mahendra K. Verma

2013-04-25T23:59:59.000Z

46

THREE-DIMENSIONAL MAGNETOHYDRODYNAMIC MODELING OF THE SOLAR WIND INCLUDING PICKUP PROTONS AND TURBULENCE TRANSPORT  

Science Conference Proceedings (OSTI)

To study the effects of interstellar pickup protons and turbulence on the structure and dynamics of the solar wind, we have developed a fully three-dimensional magnetohydrodynamic solar wind model that treats interstellar pickup protons as a separate fluid and incorporates the transport of turbulence and turbulent heating. The governing system of equations combines the mean-field equations for the solar wind plasma, magnetic field, and pickup protons and the turbulence transport equations for the turbulent energy, normalized cross-helicity, and correlation length. The model equations account for photoionization of interstellar hydrogen atoms and their charge exchange with solar wind protons, energy transfer from pickup protons to solar wind protons, and plasma heating by turbulent dissipation. Separate mass and energy equations are used for the solar wind and pickup protons, though a single momentum equation is employed under the assumption that the pickup protons are comoving with the solar wind protons. We compute the global structure of the solar wind plasma, magnetic field, and turbulence in the region from 0.3 to 100 AU for a source magnetic dipole on the Sun tilted by 0 Degree-Sign -90 Degree-Sign and compare our results with Voyager 2 observations. The results computed with and without pickup protons are superposed to evaluate quantitatively the deceleration and heating effects of pickup protons, the overall compression of the magnetic field in the outer heliosphere caused by deceleration, and the weakening of corotating interaction regions by the thermal pressure of pickup protons.

Usmanov, Arcadi V.; Matthaeus, William H. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Goldstein, Melvyn L., E-mail: arcadi.usmanov@nasa.gov [Code 673, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-07-20T23:59:59.000Z

47

An examination of loads and responses of a wind turbine undergoing variable-speed operation  

DOE Green Energy (OSTI)

The National Renewable Energy Laboratory has recently developed the ability to predict turbine loads and responses for machines undergoing variable-speed operation. The wind industry has debated the potential benefits of operating wind turbine sat variable speeds for some time. Turbine system dynamic responses (structural response, resonance, and component interactions) are an important consideration for variable-speed operation of wind turbines. The authors have implemented simple, variable-speed control algorithms for both the FAST and ADAMS dynamics codes. The control algorithm is a simple one, allowing the turbine to track the optimum power coefficient (C{sub p}). The objective of this paper is to show turbine loads and responses for a particular two-bladed, teetering-hub, downwind turbine undergoing variable-speed operation. The authors examined the response of the machine to various turbulent wind inflow conditions. In addition, they compare the structural responses under fixed-speed and variable-speed operation. For this paper, they restrict their comparisons to those wind-speed ranges for which limiting power by some additional control strategy (blade pitch or aileron control, for example) is not necessary. The objective here is to develop a basic understanding of the differences in loads and responses between the fixed-speed and variable-speed operation of this wind turbine configuration.

Wright, A.D.; Buhl, M.L. Jr.; Bir, G.S.

1996-11-01T23:59:59.000Z

48

Variables Affecting Economic Development of Wind Energy  

DOE Green Energy (OSTI)

NREL's JEDI Wind model performed an analysis of wind-power-related economic development drivers. Economic development benefits for wind and coal were estimated using NREL's JEDI Wind and JEDI Coal models.

Lantz, E.; Tegen, S.

2008-07-01T23:59:59.000Z

49

Variables Affecting Economic Development of Wind Energy  

SciTech Connect

NREL's JEDI Wind model performed an analysis of wind-power-related economic development drivers. Economic development benefits for wind and coal were estimated using NREL's JEDI Wind and JEDI Coal models.

Lantz, E.; Tegen, S.

2008-07-01T23:59:59.000Z

50

Sliding mode control law for a variable speed wind turbine  

Science Conference Proceedings (OSTI)

Modern wind turbines are designed in order to work in variable speed operations. To perform this task, wind turbines are provided with adjustable speed generators, like the double feed induction generator. One of the main advantage of adjustable speed ... Keywords: modeling and simulation, variable structure control, wind turbine control

Oscar Barambones; Jose Maria Gonzalez De Durana; Patxi Alkorta; Jose Antonio Ramos; Manuel De La Sen

2011-02-01T23:59:59.000Z

51

Variables Affecting Economic Development of Wind Energy  

NLE Websites -- All DOE Office Websites (Extended Search)

Variables Affecting Economic Variables Affecting Economic Development of Wind Energy E. Lantz and S. Tegen National Renewable Energy Laboratory Presented at WINDPOWER 2008 Houston, Texas June 1-4, 2008 Conference Paper NREL/CP-500-43506 July 2008 NREL is operated by Midwest Research Institute â—Ź Battelle Contract No. DE-AC36-99-GO10337 NOTICE The submitted manuscript has been offered by an employee of the Midwest Research Institute (MRI), a contractor of the US Government under Contract No. DE-AC36-99GO10337. Accordingly, the US Government and MRI retain a nonexclusive royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for US Government purposes. This report was prepared as an account of work sponsored by an agency of the United States government.

52

Sliding mode control strategy for variable speed wind turbine  

Science Conference Proceedings (OSTI)

The efficiency of the wind power conversions systems can be greatly improved using an appropriate control algorithm. In this work, a robust control for variable speed wind power generation that incorporates a doubly feed induction generator is described. ...

Oscar Barambones; Jose Maria Gonzalez De Durana

2009-09-01T23:59:59.000Z

53

Transient Evolution of Langmuir Turbulence in Ocean Boundary Layers Driven by Hurricane Winds and Waves  

Science Conference Proceedings (OSTI)

A large-eddy simulation (LES) model, which adopts wave-averaged equations with vortex force, is used to investigate Langmuir turbulence and ocean boundary layer (OBL) dynamics in high-wind hurricane conditions. The temporally evolving spatially ...

Peter P. Sullivan; Leonel Romero; James C. McWilliams; W. Kendall Melville

2012-11-01T23:59:59.000Z

54

Large-Eddy Simulation of Langmuir Turbulence in Pure Wind Seas  

Science Conference Proceedings (OSTI)

The scaling of turbulent kinetic energy (TKE) and its vertical component (VKE) in the upper ocean boundary layer, forced by realistic wind stress and surface waves including the effects of Langmuir circulations, is investigated using large-eddy ...

Ramsey R. Harcourt; Eric A. D’Asaro

2008-07-01T23:59:59.000Z

55

Spaced-Antenna Interferometry to Measure Crossbeam Wind, Shear, and Turbulence: Theory and Formulation  

Science Conference Proceedings (OSTI)

The theory of measuring crossbeam wind, shear, and turbulence within the radar’s resolution volume V6 is described. Spaced-antenna weather radar interferometry is formulated for such measurements using phased-array weather radar. The formulation ...

Guifu Zhang; Richard J. Doviak

2007-05-01T23:59:59.000Z

56

A Volume-Imaging Radar Wind Profiler for Atmospheric Boundary Layer Turbulence Studies  

Science Conference Proceedings (OSTI)

This paper describes the turbulent eddy profiler (TEP), a volume-imaging, UHF radar wind profiler designed for clear-air measurements in the atmospheric boundary layer on scales comparable to grid cell sizes of large eddy simulation models. TEP ...

James B. Mead; Geoffrey Hopcraft; Stephen J. Frasier; Brian D. Pollard; Christopher D. Cherry; Daniel H. Schaubert; Robert E. McIntosh

1998-08-01T23:59:59.000Z

57

The Relationships among Wind, Horizontal Pressure Gradient, and Turbulent Momentum Transport during CASES-99  

Science Conference Proceedings (OSTI)

Relationships among the horizontal pressure gradient, the Coriolis force, and the vertical momentum transport by turbulent fluxes are investigated using data collected from the Cooperative Atmosphere-Surface Exchange Study in 1999 (CASES99). Wind ...

Jielun Sun; Donald H. Lenschow; Larry Mahrt; Carmen Nappo

58

Prediction of the Proton-to-Total Turbulent Heating in the Solar Wind  

E-Print Network (OSTI)

This paper employs a recent turbulent heating prescription to predict the ratio of proton-to-total heating due to the kinetic dissipation of Alfvenic turbulence as a function of heliocentric distance. Comparing to a recent empirical estimate for this turbulent heating ratio in the high-speed solar wind, the prediction shows good agreement with the empirical estimate for R >~ 0.8 AU, but predicts less ion heating than the empirical estimate at smaller heliocentric radii. At these smaller radii, the turbulent heating prescription, calculated in the gyrokinetic limit, fails because the turbulent cascade is predicted to reach the proton cyclotron frequency before Landau damping terminates the cascade. These findings suggest that the turbulent cascade can reach the proton cyclotron frequency at R ~ 0.8 AU, this turbulent heating prescription contains all of the necessary physical mechanisms needed to reproduce the empirically estimated proton-to-total heating ratio.

Howes, G G

2011-01-01T23:59:59.000Z

59

On the Loss of Wind-Induced Near-Inertial Energy to Turbulent Mixing in the Upper Ocean  

E-Print Network (OSTI)

On the Loss of Wind-Induced Near-Inertial Energy to Turbulent Mixing in the Upper Ocean XIAOMING received 27 March 2009, in final form 23 June 2009) ABSTRACT Wind-induced near-inertial energy has been find that nearly 70% of the wind-induced near-inertial energy at the sea surface is lost to turbulent

Miami, University of

60

A Case for Including Atmospheric Thermodynamic Variables in Wind Turbine Fatigue Loading Parameter Identification  

DOE Green Energy (OSTI)

This paper makes the case for establishing efficient predictor variables for atmospheric thermodynamics that can be used to statistically correlate the fatigue accumulation seen on wind turbines. Recently, two approaches to this issue have been reported. One uses multiple linear-regression analysis to establish the relative causality between a number of predictors related to the turbulent inflow and turbine loads. The other approach, using many of the same predictors, applies the technique of principal component analysis. An examination of the ensemble of predictor variables revealed that they were all kinematic in nature; i.e., they were only related to the description of the velocity field. Boundary-layer turbulence dynamics depends upon a description of the thermal field and its interaction with the velocity distribution. We used a series of measurements taken within a multi-row wind farm to demonstrate the need to include atmospheric thermodynamic variables as well as velocity-related ones in the search for efficient turbulence loading predictors in various turbine-operating environments. Our results show that a combination of vertical stability and hub-height mean shearing stress variables meet this need over a period of 10 minutes.

Kelley, N. D.

1999-08-02T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Variable selection for wind power prediction using particle swarm optimization  

Science Conference Proceedings (OSTI)

Wind energy has an increasing influence on the energy supply in many countries, but in contrast to conventional power plants it is a fluctuating energy source. For its integration in the electricity supply structure it is necessary to predict the wind ... Keywords: nearest neighbour search, neural network, particle swarm optimization, variable selection, wind power prediction

René Jursa

2007-07-01T23:59:59.000Z

62

LQG Controller for a Variable Speed Pitch Regulated Wind Turbine  

Science Conference Proceedings (OSTI)

This paper deals with the design of LQG controllers for pitch regulated, variable speed wind turbines where the controller is used primarily for controlling the pitch angle through a collective pitch angle in the high wind speed in order to guarantee ... Keywords: LQG controller, Pitch control, Wind Trubine

Xingjia Yao; Shu Liu; Guangkun Shan; Zuoxia Xing; Changchun Guo; Chuanbao Yi

2009-08-01T23:59:59.000Z

63

ENHANCED DISSIPATION RATE OF MAGNETIC FIELD IN STRIPED PULSAR WINDS BY THE EFFECT OF TURBULENCE  

SciTech Connect

In this paper, we report on turbulent acceleration of the dissipation of the magnetic field in the post-shock region of a Poynting flux-dominated flow, such as the Crab pulsar wind nebula. We have performed two-dimensional resistive relativistic magnetohydrodynamics simulations of subsonic turbulence driven by the Richtmyer-Meshkov instability at the shock fronts of the Poynting flux-dominated flows in pulsar winds. We find that turbulence stretches current sheets which substantially enhances the dissipation of the magnetic field, and that most of the initial magnetic field energy is dissipated within a few eddy-turnover times. We also develop a simple analytical model for turbulent dissipation of the magnetic field that agrees well with our simulations. The analytical model indicates that the dissipation rate does not depend on resistivity even in the small resistivity limit. Our findings can possibly alleviate the {sigma}-problem in the Crab pulsar wind nebulae.

Takamoto, Makoto [Department of Physics, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502 (Japan); Inoue, Tsuyoshi [Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe, Chuou-ku, Sagamihara 252-5258 (Japan); Inutsuka, Shu-ichiro, E-mail: takamoto@tap.scphys.kyoto-u.ac.jp, E-mail: inouety@phys.aoyama.ac.jp, E-mail: inutsuka@nagoya-u.jp [Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan)

2012-08-10T23:59:59.000Z

64

Analysis of Wind and Turbulence Fields in a Region with Complex Orography  

Science Conference Proceedings (OSTI)

In a region of about 1000 km2 with complex orography, 1-h averages of wind and turbulence fields were analyzed over a period of 1 yr. It was shown that spatial homogeneity and temporal stationarity of the wind fields as well as the degree of ...

Waldemar Feller; Fritz Gassmann

1997-09-01T23:59:59.000Z

65

Lidar Measurement of Turbulence Encountered by Horizontal-Axis Wind Turbines  

Science Conference Proceedings (OSTI)

We used a continuous-wave (CW) Doppler lidar to measure wind velocity turbulence from a moving frame of reference. By directing the lidar beam to trace the perimeters of vertical-plane disks about horizontal axes parallel to the mean wind ...

R. M. Hardesty; B. F. Weber

1987-03-01T23:59:59.000Z

66

Propagation of Wind Energy into the Deep Ocean through a Fully Turbulent Mesoscale Eddy Field  

Science Conference Proceedings (OSTI)

The authors analyze the 3D propagation of wind-forced near-inertial motions in a fully turbulent mesoscale eddy field with a primitive equation numerical model. Although the wind stress is uniform, the near-inertial motion field quickly becomes ...

Eric Danioux; Patrice Klein; Pascal Rivičre

2008-10-01T23:59:59.000Z

67

DISTRIBUTION OF MAGNETIC DISCONTINUITIES IN THE SOLAR WIND AND IN MAGNETOHYDRODYNAMIC TURBULENCE  

Science Conference Proceedings (OSTI)

The statistical properties of magnetic discontinuities in the solar wind are investigated by measuring fluctuations in the magnetic field direction, given by the rotation {Delta}{theta} that the magnetic field vector undergoes during time interval {Delta}t. We show that the probability density function, P({Delta}{theta}), can be described by a simple model in which the magnetic field vector purely rotates with a relative increment {Delta}B/B that is lognormally distributed. We find that the probability density function of increments, P({Delta}B/B), has a remarkable scaling property: the normalized variable x = ({Delta}B/B) {center_dot} ({Delta}t/{Delta}t{sub 0}){sup -{alpha}} has a universal lognormal distribution for all time intervals {Delta}t. We then compare measurements from the solar wind with those from direct numerical simulations of magnetohydrodynamic (MHD) turbulence. We find good agreement for P({Delta}{theta}) obtained in the two cases when the magnetic guide field to fluctuations ratio B{sub 0}/b{sub rms} is chosen accordingly. However, the scale invariance of P({Delta}B/B) is broken in the MHD simulations with relatively limited inertial interval, which causes P({Delta}{theta}) to scale with measurement interval differently than in the solar wind.

Zhdankin, Vladimir; Boldyrev, Stanislav [Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706 (United States); Mason, Joanne [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)

2012-12-01T23:59:59.000Z

68

Distribution of Magnetic Discontinuities in the Solar Wind and in MHD Turbulence  

E-Print Network (OSTI)

The statistical properties of magnetic discontinuities in the solar wind are investigated by measuring fluctuations in the magnetic field direction, given by the rotation Delta theta that the magnetic field vector undergoes during time interval Delta t. We show that the probability density function for rotations, P(Delta theta), can be described by a simple model in which the magnetic field vector rotates with a relative increment (Delta B)/B that is lognormally distributed. We find that the probability density function of increments, P((Delta B)/B), has a remarkable scaling property: the normalized variable x=[(Delta B)/B]*[(Delta t)/(Delta t_0)]^-a has a universal lognormal distribution for all time intervals Delta t. We then compare measurements from the solar wind with those from direct numerical simulations of magnetohydrodynamic (MHD) turbulence. We find good agreement for P(Delta theta) obtained in the two cases when the magnetic guide-field to fluctuations ratio B_0/b_rms is chosen accordingly. However, the scale invariance of P((Delta B)/B) is broken in the MHD simulations with relatively limited inertial interval, which causes P(Delta theta) to scale with measurement interval differently than in the solar wind.

Vladimir Zhdankin; Stanislav Boldyrev; Joanne Mason

2012-10-12T23:59:59.000Z

69

Adaptive variable structure control law for a variable speed wind turbine  

Science Conference Proceedings (OSTI)

The efficiency of the wind power conversions systems can be greatly improved using an appropriate control algorithm. In this work, an adaptive robust control for a doubly feed induction generator drive for variable speed wind power generation is described. ... Keywords: modeling and simulation, variable structure control, wind turbine control

Oscar Barambones; Jose Maria Gonzalez De Durana; Patxi Alkorta; Jose Antonio Ramos; Manuel De La Sen

2011-05-01T23:59:59.000Z

70

Impact of Coherent Turbulence on Wind Turbine Aeroelastic Response and Its Simulation: Preprint  

DOE Green Energy (OSTI)

In this paper, we present a brief overview of our recent research results regarding the impact of organized or coherent inflow turbulence on the dynamic response of operating wind turbines. Previous field experimentation has demonstrated that the greatest structural fatigue damage tends to occur during the nighttime hours from coherent turbulence that develops in the stable, nocturnal atmospheric boundary layer. We have found that under such conditions, intense vertical wind shear and temperature gradients create resonant flow fields that are capable of imparting short-period loading and vibrational energy as wind turbine rotor blades pass through regions of organized or coherent turbulence. This energy is subsequently propagated throughout the remainder of the structure, where it is often locally dissipated. We also briefly discuss our recent progress in developing a numerical simulation that includes such coherent inflow conditions that can be used to excite wind turbine design codes.

Kelley, N. D.; Jonkman, B. J.; Scott, G. N.; Bialasiewicz, J. T.; Redmond, L. S.

2005-08-01T23:59:59.000Z

71

Remote Determination of Winds, Turbulence Spectra and Energy Dissipation Rates in the Boundary Layer from Lidar Measurements  

Science Conference Proceedings (OSTI)

Procedures are described for the analysis of lidar data to remotely measure 1) spectra of aerosol density fluctuations, 2) radial and transverse components of the mean wind and turbulent fluctuations of the transverse component of the wind ...

K. E. Kunkel; E. W. Eloranta; J. A. Weinman

1980-05-01T23:59:59.000Z

72

Scaling Laws of Turbulence and Heating of Fast SolarWind: The Role of Density Fluctuations  

E-Print Network (OSTI)

Incompressible and isotropic magnetohydrodynamic turbulence in plasms can be described by an exact relation for the energy flux through the scales. This Yaglom-like scaling law has been recently observed in the solar wind above the solar poles observed by the Ulysses spacecraft, where the turbulence is in an Alfv\\'enic state. An analogous phenomenological scaling law, suitably modified to take into account compressible fluctuations, is observed more frequently in the same dataset. Large scale density fluctuations, despite their low amplitude, play thus a crucial role in the basic scaling properties of turbulence. The turbulent cascade rate in the compressive case can moreover supply the energy dissipation needed to account for the local heating of the non-adiabatic solar wind.

Carbone, V; Sorriso-Valvo, L; Noullez, A; Bruno, R

2010-01-01T23:59:59.000Z

73

Processing of turbulence-layer wind speed with Generalized SCIDAR through wavelet analysis  

E-Print Network (OSTI)

We describe a new method involving wavelet transforms for deriving the wind velocity associated with atmospheric turbulence layers from Generalized SCIDAR measurements. The algorithm analyses the cross-correlation of a series of scintillation patterns separated by lapses of Dt, 2Dt, 3Dt, 4Dt and 5Dt using wavelet transforms. Wavelet analysis provides the position, direction and altitude of the different turbulence layers detected in each cross-correlation. The comparison and consistency of the turbulent layer displacements in consecutive cross-correlations allow the determination of their velocities and avoid misidentifications associated with noise and/or overlapping layers. To validate the algorithm, we have compared the velocity of turbulence layers derived on four nights with the wind vertical profile provided by balloon measurements. The software is fully automated and is able to analyse huge amounts of Generalized SCIDAR measurements.

B. Garcia-Lorenzo; J. J. Fuensalida

2006-08-28T23:59:59.000Z

74

Modification of Proton Velocity Distributions by Alfvenic Turbulence in the Solar Wind  

E-Print Network (OSTI)

In the present paper, the proton velocity distribution function (VDF)in the solar wind is determined by solving numerically the kinetic evolution equation. We compare the results obtained when considering the effects of ex- ternal forces and Coulomb collisions with those obtained by adding effects of Alfven wave turbulence. We use Fokker-Planck diffusion terms due to Alfvenic turbulence, which take into account observed turbulence spectra and kinetic effects of finite proton gyroradius. Assuming a displaced Maxwellian for the proton VDF at the simulation boundary at 14 solar radii, we show that the turbulence leads to a fast (within several solar radii) development of the anti-sunward tail in the proton VDF. Our results provide a natural explanation for the nonthermal tails in the proton VDFs, which are often observed in-situ in the solar wind beyond 0.3 AU.

Pierrard, Viviane

2013-01-01T23:59:59.000Z

75

The turbulent cascade and proton heating in the solar wind during solar minimum  

Science Conference Proceedings (OSTI)

Solar wind measurements at 1 AU during the recent solar minimum and previous studies of solar maximum provide an opportunity to study the effects of the changing solar cycle on in situ heating. Our interest is to compare the levels of activity associated with turbulence and proton heating. Large-scale shears in the flow caused by transient activity are a source that drives turbulence that heats the solar wind, but as the solar cycle progresses the dynamics that drive the turbulence and heat the medium are likely to change. The application of third-moment theory to Advanced Composition Explorer (ACE) data gives the turbulent energy cascade rate which is not seen to vary with the solar cycle. Likewise, an empirical heating rate shows no significan changes in proton heating over the cycle.

Coburn, Jesse T.; Smith, Charles W.; Vasquez, Bernard J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire (United States); Stawarz, Joshua E. [Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, Boulder, Colorado (United States); Forman, Miriam A. [Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, New York (United States)

2013-06-13T23:59:59.000Z

76

Lidar measurement of wind velocity turbulence spectra encountered by a rotating turbine blade  

DOE Green Energy (OSTI)

A homodyne CO/sub 2/ lidar system beam was conically scanned around a horizontal axis to measure the wind speed and turbulence characteristics encountered by a rotating turbine blade. Turbulence spectra obtained from the scanning lidar differed considerably from those calculated from fixed-point anemometer measurements, showing a redistribution of energy from lower to higher frequencies. The differences appeared more pronounced during periods when the atmosphere was stable.

Hardesty, R.M.; Korrell, J.A.; Hall, F.F. Jr.

1982-01-01T23:59:59.000Z

77

THE TURBULENT CASCADE AND PROTON HEATING IN THE SOLAR WIND DURING SOLAR MINIMUM  

Science Conference Proceedings (OSTI)

The recently protracted solar minimum provided years of interplanetary data that were largely absent in any association with observed large-scale transient behavior on the Sun. With large-scale shear at 1 AU generally isolated to corotating interaction regions, it is reasonable to ask whether the solar wind is significantly turbulent at this time. We perform a series of third-moment analyses using data from the Advanced Composition Explorer. We show that the solar wind at 1 AU is just as turbulent as at any other time in the solar cycle. Specifically, the turbulent cascade of energy scales in the same manner proportional to the product of wind speed and temperature. Energy cascade rates during solar minimum average a factor of 2-4 higher than during solar maximum, but we contend that this is likely the result of having a different admixture of high-latitude sources.

Coburn, Jesse T.; Smith, Charles W.; Vasquez, Bernard J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH (United States); Stawarz, Joshua E. [Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, Boulder, CA (United States); Forman, Miriam A., E-mail: jtu46@wildcats.unh.edu, E-mail: Charles.Smith@unh.edu, E-mail: Bernie.Vasquez@unh.edu, E-mail: Joshua.Stawarz@Colorado.edu, E-mail: Miriam.Forman@sunysb.edu [Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY (United States)

2012-08-01T23:59:59.000Z

78

Electron and proton heating by solar wind turbulence  

E-Print Network (OSTI)

Previous formulations of heating and transport associated with strong magnetohydrodynamic (MHD) turbulence are generalized to incorporate separate internal energy equations for electrons and protons. Electron heat conduction is included. Energy is supplied by turbulent heating that affects both electrons and protons, and is exchanged between them via collisions. Comparison to available Ulysses data shows that a reasonable accounting for the data is provided when (i) the energy exchange timescale is very long and (ii) the deposition of heat due to turbulence is divided, with 60% going to proton heating and 40% into electron heating. Heat conduction, determined here by an empirical fit, plays a major role in describing the electron data.

Breech, B; Cranmer, S R; Kasper, J C; Oughton, S

2009-01-01T23:59:59.000Z

79

Decadal Variability in a Simplified Wind-Driven Ocean Model  

Science Conference Proceedings (OSTI)

The impact of an unsteady wind forcing on oceanic low-frequency variability is conceptually studied using a reduced-gravity shallow-water model. A time-averaged wind forcing and a simple ocean–atmosphere coupling is completed by a stochastic ...

Philip Sura; Frank Lunkeit; Klaus Fraedrich

2000-08-01T23:59:59.000Z

80

Trends and Interannual Variability of Wind Speed Distributions in Minnesota  

Science Conference Proceedings (OSTI)

Near-surface wind speed variability is investigated at seven stations in and surrounding Minnesota for recent climate records of 22–35 yr in length. Analyses focus on mean annual wind speeds and on the 10th, 25th, 50th, 75th, and 90th percentiles ...

Katherine Klink

2002-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Petascale Simulations of Inhomogeneous Alfven Turbulence in the Solar Wind  

NLE Websites -- All DOE Office Websites (Extended Search)

A snapshot of turbulent magnetic field lines (red) inside a coronal hole that expands from a small patch on the solar surface to 5 solar radii A snapshot of turbulent magnetic field lines (red) inside a coronal hole that expands from a small patch on the solar surface to 5 solar radii A snapshot of turbulent magnetic field lines (red) inside a coronal hole that expands from a small patch on the solar surface to 5 solar radii. Alfven waves (AW), launched by convective motions on the photosphere, propagate in the inhomogeneous Solar atmosphere producing primary reflected waves that interact non-linearly with the outward waves, driving a turbulent cascade. This cascade continues with secondary reflections in a very complex interplay between wave reflections and nonlinear interactions. Selected slices across the simulation domain show contours of plasma current, indicating the generation of small scale structures where the

82

PREDICTION OF THE PROTON-TO-TOTAL TURBULENT HEATING IN THE SOLAR WIND  

SciTech Connect

This paper employs a recent turbulent heating prescription to predict the ratio of proton-to-total heating due to the kinetic dissipation of Alfvenic turbulence as a function of heliocentric distance. Comparing to a recent empirical estimate for this turbulent heating ratio in the high-speed solar wind, the prediction shows good agreement with the empirical estimate for R {approx}> 0.8 AU, but predicts less ion heating than the empirical estimate at smaller heliocentric radii. At these smaller radii, the turbulent heating prescription, calculated in the gyrokinetic limit, fails because the turbulent cascade is predicted to reach the proton cyclotron frequency before Landau damping terminates the cascade. These findings suggest that the turbulent cascade can reach the proton cyclotron frequency at R {approx}< 0.8 AU, leading to a higher level of proton heating than predicted by the turbulent heating prescription in the gyrokinetic limit. At larger heliocentric radii, R {approx}> 0.8 AU, this turbulent heating prescription contains all of the necessary physical mechanisms needed to reproduce the empirically estimated proton-to-total heating ratio.

Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States)

2011-09-01T23:59:59.000Z

83

Quasilinear Evolution of Kinetic Alfven Wave Turbulence and Perpendicular Ion Heating in the Solar Wind  

E-Print Network (OSTI)

It is shown that the quasi-linear evolution of ion and electron distribution functions as result of wave-particle interaction of Kinetic Alfven Waves in the turbulent solar wind plasma leads to instability of long wavelength electromagnetic cyclotron waves and to an increase of the ion temperature perpendicular to the magnetic field.

Rudakov, L; Ganguli, G; Mithaiwala, M

2010-01-01T23:59:59.000Z

84

Turbulence Anisotropy Determined by Wind Profiler Radar and Its Correlation with Rain Events in Montreal, Canada  

Science Conference Proceedings (OSTI)

Turbulence inhomogeneities at 3-m scales can be either isotropic or anisotropic, and the degree of anisotropy can be measured with VHF wind profiler radars. Studies over a period of two years in Montreal, Quebec, Canada, have shown that for this ...

Anna Hocking; Wayne K. Hocking

2007-01-01T23:59:59.000Z

85

Atmospheric and Wake Turbulence Impacts on Wind Turbine Fatigue Loading: Preprint  

DOE Green Energy (OSTI)

Large-eddy simulations of atmospheric boundary layers under various stability and surface roughness conditions are performed to investigate the turbulence impact on wind turbines. In particular, the aeroelastic responses of the turbines are studied to characterize the fatigue loading of the turbulence present in the boundary layer and in the wake of the turbines. Two utility-scale 5 MW turbines that are separated by seven rotor diameters are placed in a 3 km by 3 km by 1 km domain. They are subjected to atmospheric turbulent boundary layer flow and data is collected on the structural response of the turbine components. The surface roughness was found to increase the fatigue loads while the atmospheric instability had a small influence. Furthermore, the downstream turbines yielded higher fatigue loads indicating that the turbulent wakes generated from the upstream turbines have significant impact.

Lee, S.; Churchfield, M.; Moriarty, P.; Jonkman, J.; Michalakes, J.

2011-12-01T23:59:59.000Z

86

Covariance statistics of turbulence velocity components for wind-energy-conversion system design-homogeneous, isotropic case  

DOE Green Energy (OSTI)

When designing a wind energy converison system (WECS), it may be necessary to take into account the distribution of wind across the disc of rotation. The specific engineering applications include structural strength, fatigue, and control. This wind distribution consists of two parts, namely that associated with the mean wind profile and that associated with the turbulence velocity fluctuation field. The work reported herein is aimed at the latter, namely the distribution of turbulence velocity fluctuations across the WECS disk of rotation. A theory is developed for the two-time covariance matrix for turbulence velocity vector components for wind energy conversion system (WECS) design. The theory is developed for homogeneous and iotropic turbulance with the assumption that Taylor's hypothesis is valid. The Eulerian turbulence velocity vector field is expanded about the hub of the WECS. Formulae are developed for the turbulence velocity vector component covariance matrix following the WECS blade elements. It is shown that upon specification of the turbulence energy spectrum function and the WECS rotation rate, the two-point, two-time covariance matrix of the turbulent flow relative to the WECS bladed elements is determined. This covariance matrix is represented as the sum of nonstationary and stationary contributions. Generalized power spectral methods are used to obtain two-point, double frequency power spectral density functions for the turbulent flow following the blade elements. The Dryden turbulence model is used to demonstrate the theory. A discussion of linear system response analysis is provided to show how the double frequency turbulence spectra might be used to calculate response spectra of a WECS to turbulent flow. Finally the spectrum of the component of turbulence normal to the WECS disc of rotation, following the blade elements, is compared with experimental results.

Fichtl, G.H.

1983-09-01T23:59:59.000Z

87

Radar Wind Profiler Radial Velocity: A Comparison with Doppler Lidar  

Science Conference Proceedings (OSTI)

The accuracy of the radial wind velocity measured with a radar wind profiler will depend on turbulent variability and instrumental noise. Radial velocity estimates of a boundary layer wind profiler are compared with those estimated by a Doppler ...

Stephen A. Cohn; R. Kent Goodrich

2002-12-01T23:59:59.000Z

88

Oceanic Quasi-geostrophic Turbulence Forced by Stochastic Wind Fluctuations  

Science Conference Proceedings (OSTI)

The quasi-geostrophic response to stochastic wind fluctuations is calculated using a doubly periodic nonlinear model, with a vertical resolution of three modes in most cases. The influence of various parameters on the response is investigated: ...

Anne Marie Treguier; Bach Lien Hua

1987-03-01T23:59:59.000Z

89

Turbulent Heating in the Solar Wind and in the Solar Corona  

E-Print Network (OSTI)

In this paper we calculate the turbulent heating rates in the solar wind using the Kolmogorov-like MHD turbulence phenomenology with Kolmogorov's constants calculated by {\\it Verma and Bhattacharjee }[1995b,c]. We find that the turbulent heating can not account for the total heating of the nonAlfv\\'enic streams in the solar wind. We show that dissipation due to thermal conduction is also a potential heating source. Regarding the Alfv\\'enic streams, the predicted turbulent heating rates using the constants of {\\it Verma and Bhattacharjee }[1995c] are higher than the observed heating rates; the predicted dissipation rates are probably overestimates because Alfv\\'enic streams have not reached steady-state. We also compare the predicted turbulent heating rates in the solar corona with the observations; the Kolmogorov-like phenomenology predicts dissipation rates comparable to the observed heating rates in the corona [{\\it Hollweg, }% 1984], but Dobrowoly et al.'s generalized Kraichnan model yields heating rates much less than that required.

Mahendra K. Verma

1995-09-05T23:59:59.000Z

90

Turbulent Heating in the Solar Wind and in the Solar Corona  

E-Print Network (OSTI)

In this paper we calculate the turbulent heating rates in the solar wind using the Kolmogorov-like MHD turbulence phenomenology with Kolmogorov’s constants calculated by Verma and Bhattacharjee [1995b,c]. We find that the turbulent heating can not account for the total heating of the nonAlfvénic streams in the solar wind. We show that dissipation due to thermal conduction is also a potential heating source. Regarding the Alfvénic streams, the predicted turbulent heating rates using the constants of Verma and Bhattacharjee [1995c] are higher than the observed heating rates; the predicted dissipation rates are probably overestimates because Alfvénic streams have not reached steady-state. We also compare the predicted turbulent heating rates in the solar corona with the observations; the Kolmogorov-like phenomenology predicts dissipation rates comparable to the observed heating rates in the corona [Hollweg, 1984], but Dobrowoly et al.’s generalized Kraichnan model yields heating rates much less than that required. 1 1

Mahendra K. Verma

2008-01-01T23:59:59.000Z

91

Stratified Turbulence and the Mesoscale Variability of the Atmosphere  

Science Conference Proceedings (OSTI)

An analysis is made of Gage's proposal that the horizontal energy spectrum at mesoscale wavelengths is produced by upscale energy transfer through quasi-two-dimensional turbulence. It is suggested that principal sources of such energy can be ...

D. K. Lilly

1983-03-01T23:59:59.000Z

92

Turbulence process domination under the combined forcings of wind stress, the Langmuir vortex force, and surface cooling  

Science Conference Proceedings (OSTI)

Turbulence in the ocean surface layer is generated by time-varying combinations of destabilizing surface buoyancy flux, wind stress forcing, and wave forcing through a vortex force associated with the surface wave field. Observations of time- and ...

A. E. Gargett; C. E. Grosch

93

Impact of Breaking Wave Form Drag on Near-Surface Turbulence and Drag Coefficient over Young Seas at High Winds  

Science Conference Proceedings (OSTI)

The effects of breaking waves on near-surface wind turbulence and drag coefficient are investigated using large-eddy simulation. The impact of intermittent and transient wave breaking events (over a range of scales) is modeled as localized form ...

Nobuhiro Suzuki; Tetsu Hara; Peter P. Sullivan

2013-02-01T23:59:59.000Z

94

A Free-Floating PIV System: Measurements of Small-Scale Turbulence under the Wind Wave Surface  

Science Conference Proceedings (OSTI)

An in situ free-floating underwater miniature particle image velocimetry (UWMPIV) system is developed and applied to measure the structure of turbulence in the aqueous side of the wind wave surface boundary layer. The UWMPIV system provides a ...

Binbin Wang; Qian Liao; Jianen Xiao; Harvey A. Bootsma

2013-07-01T23:59:59.000Z

95

Wind and Turbulence in a Sparse but Regular Plant Canopy  

Science Conference Proceedings (OSTI)

Wind velocity statistics from several points within a regular but sparse array of clumped corn plants are analyzed, with each clump consisting of 12 plants, having a mean height of 1.6 m and a collective leaf area of about 2.75 m2 and occupying ...

Andree Tuzet; John D. Wilson

2002-05-01T23:59:59.000Z

96

Variability of Load and Net Load in Case of Large Scale Distributed Wind Power  

Science Conference Proceedings (OSTI)

Large scale wind power production and its variability is one of the major inputs to wind integration studies. This paper analyses measured data from large scale wind power production. Comparisons of variability are made across several variables: time scale (10-60 minute ramp rates), number of wind farms, and simulated vs. modeled data. Ramp rates for Wind power production, Load (total system load) and Net load (load minus wind power production) demonstrate how wind power increases the net load variability. Wind power will also change the timing of daily ramps.

Holttinen, H.; Kiviluoma, J.; Estanqueiro, A.; Gomez-Lazaro, E.; Rawn, B.; Dobschinski, J.; Meibom, P.; Lannoye, E.; Aigner, T.; Wan, Y. H.; Milligan, M.

2011-01-01T23:59:59.000Z

97

Energy Storage on the Grid and the Short-term Variability of Wind.  

E-Print Network (OSTI)

??Wind generation presents variability on every time scale, which must be accommodated by the electric grid. Limited quantities of wind power can be successfully integrated… (more)

Hittinger, Eric Stephen

2012-01-01T23:59:59.000Z

98

THE SLOW-MODE NATURE OF COMPRESSIBLE WAVE POWER IN SOLAR WIND TURBULENCE  

Science Conference Proceedings (OSTI)

We use a large, statistical set of measurements from the Wind spacecraft at 1 AU, and supporting synthetic spacecraft data based on kinetic plasma theory, to show that the compressible component of inertial range solar wind turbulence is primarily in the kinetic slow mode. The zero-lag cross-correlation C({delta}n, {delta}B{sub ||}) between proton density fluctuations {delta}n and the field-aligned (compressible) component of the magnetic field {delta}B{sub ||} is negative and close to -1. The typical dependence of C({delta}n, {delta}B{sub ||}) on the ion plasma beta {beta}{sub i} is consistent with a spectrum of compressible wave energy that is almost entirely in the kinetic slow mode. This has important implications for both the nature of the density fluctuation spectrum and for the cascade of kinetic turbulence to short wavelengths, favoring evolution to the kinetic Alfven wave mode rather than the (fast) whistler mode.

Howes, G. G.; Klein, K. G.; TenBarge, J. M. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Bale, S. D.; Chen, C. H. K.; Salem, C. S. [Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States)

2012-07-01T23:59:59.000Z

99

INVESTIGATION OF INTERMITTENCY IN MAGNETOHYDRODYNAMICS AND SOLAR WIND TURBULENCE: SCALE-DEPENDENT KURTOSIS  

SciTech Connect

The behavior of scale-dependent (or filtered) kurtosis is studied in the solar wind using magnetic field measurements from the ACE and Cluster spacecraft at 1 AU. It is also analyzed numerically with high-resolution magnetohydrodynamic spectral simulations. In each case the filtered kurtosis increases with wavenumber, implying the presence of coherent structures at the smallest scales. This phase coupling is related to intermittency in solar wind turbulence and the emergence of non-Gaussian statistics. However, it is inhibited by the presence of upstream waves and other phase-randomizing structures, which act to reduce the growth of kurtosis.

Wan Minping; Osman, Kareem T.; Matthaeus, William H. [Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Oughton, Sean, E-mail: mpwan@bartol.udel.edu [Department of Mathematics, University of Waikato, Hamilton 3240 (New Zealand)

2012-01-10T23:59:59.000Z

100

Wind reversals in turbulent Rayleigh-Benard convection  

E-Print Network (OSTI)

The phenomenon of irregular cessation and subsequent reversal of the large-scale circulation in turbulent Rayleigh-B\\'enard convection is theoretically analysed. The force and thermal balance on a single plume detached from the thermal boundary layer yields a set of coupled nonlinear equations, whose dynamics is related to the Lorenz equations. For Prandtl and Rayleigh numbers in the range $10^{-2} \\leq \\Pr \\leq 10^{3}$ and $10^{7} \\leq \\Ra \\leq 10^{12}$, the model has the following features: (i) chaotic reversals may be exhibited at Ra $\\geq 10^{7}$; (ii) the Reynolds number based on the root mean square velocity scales as $\\Re_{rms} \\sim \\Ra^{[0.41 ... 0.47]}$ (depending on Pr), and as $\\Re_{rms} \\sim \\Pr^{-[0.66 ... 0.76]}$ (depending on Ra); and (iii) the mean reversal frequency follows an effective scaling law $\\omega / (\

Francisco Fontenele Araujo; S. Grossmann; D. Lohse

2004-07-13T23:59:59.000Z

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101

Variable-Speed Wind System Design : Final Report.  

SciTech Connect

Almost from the onset of the development of wind energy conversion systems (WECS), it was known that variable-speed operation of the turbine would maximize energy capture. This study was commissioned to assess the cost, efficiency gain, reduction of the cost of energy (COE), and other operating implications of converting the existing hardware of a modern fixed-speed wind energy conversion system to variable-speed operation. The purpose of this study was to develop a preliminary design for the hardware required to allow variable-speed operation using a doubly-fed generator with an existing fixed-speed wind turbine design. The turbine selected for this study is the AWT-26 designed and built by Advanced Wind Turbines Inc. of Redmond, Washington. The lowest projected COE using this variable-speed generation system is projected to be $0.0499/kWh, compared to the lowest possible COE with fixed-speed generation which is projected to be $0.0546/kWh. This translates into a 8.6% reduction of the COE using this variable-speed generation option. The preliminary system design has advanced to where the printed circuit boards can be physically laid out based on the schematics and the system software can be written based on the control flow-charts. The core of hardware and software has been proven to be successful in earlier versions of VSG systems. The body of this report presents the results of the VSWG system development. Operation under normal and fault conditions is described in detail, the system performance for variable-speed operation is estimated and compared to the original fixed-speed system performance, and specifications for all system components (generator, power electronic converter, and system controller) are given. Costs for all components are estimated, and incremental system cost is compared to incremental energy production. Finally, operational features of the VSWG which are not available in the existing FSWG system are outlined.

Lauw, Hinan K.; Weigand, Claus H.; Marckx, Dallas A.; Electronic Power Conditioning, Inc.

1993-10-01T23:59:59.000Z

102

FRAME DEPENDENCE OF THE ELECTRIC FIELD SPECTRUM OF SOLAR WIND TURBULENCE  

Science Conference Proceedings (OSTI)

We present the first survey of electric field data using the ARTEMIS spacecraft in the solar wind to study inertial range turbulence. It was found that the average perpendicular spectral index of the electric field depends on the frame of measurement. In the spacecraft frame it is -5/3, which matches the magnetic field due to the large solar wind speed in Lorentz transformation. In the mean solar wind frame, the electric field is primarily due to the perpendicular velocity fluctuations and has a spectral index slightly shallower than -3/2, which is close to the scaling of the velocity. These results are an independent confirmation of the difference in scaling between the velocity and magnetic field, which is not currently well understood. The spectral index of the compressive fluctuations was also measured and found to be close to -5/3, suggesting that they are not only passive to the velocity but may also interact nonlinearly with the magnetic field.

Chen, C. H. K.; Bale, S. D.; Salem, C.; Mozer, F. S., E-mail: chen@ssl.berkeley.edu [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)

2011-08-20T23:59:59.000Z

103

EFFECT OF PITCH CONTROL AND POWER CONDITIONING ON POWER QUALITY OF VARIABLE SPEED WIND TURBINE GENERATORS  

E-Print Network (OSTI)

Wind energy is considered as the most viable renewable energy options. In a renewable energy system more energy from the wind. One of the options is to use the variable speed wind turbine-speed wind turbine system for transient studies are discussed in this paper. The performance of wind energy

104

Numerical Study of the Effects of Atmospheric and Wake Turbulence on Wind Turbine Dynamics  

SciTech Connect

Although the atmospheric sciences community has been studying the effects of atmospheric stability and surface roughness on the planetary boundary layer for some time, their effects on wind turbine dynamics have not been well studied. In this study, we performed numerical experiments to explore some of the effects of atmospheric stability and surface roughness on wind turbine dynamics. We used large-eddy simulation to create atmospheric winds and compute the wind turbine flows, and we modeled the wind turbines as revolving and flexible actuator lines coupled to a wind turbine structural and system dynamic model. We examined the structural moments about the wind turbine blade, low-speed shaft, and nacelle; power production; and wake evolution when large 5-MW turbines are subjected to winds generated from low- and high-surface roughness levels representative of offshore and onshore conditions, respectively, and also neutral and unstable atmospheric conditions. In addition, we placed a second turbine 7 rotor diameters downwind of the first one so that we could explore wake effects under these different conditions. The results show that the turbulent structures generated within the atmospheric boundary layer wind simulations cause isolated loading events at least as significant as when a turbine is waked by an upwind turbine. The root-mean-square (RMS) turbine loads are consistently larger when the surface roughness is higher. The RMS blade-root out-of-plane bending moment and low-speed shaft torque are higher when the atmospheric boundary layer is unstable as compared with when it is neutral. However, the RMS yaw moments are either equal or reduced in the unstable case as compared with the neutral case. For a given surface roughness, the ratio of power produced by the downwind turbine relative to that of the upwind turbine is 15-20% higher when the conditions are unstable as compared with neutral. For a given atmospheric stability, this power ratio is 10% higher with the onshore roughness value versus the offshore one. The main conclusion is that various coherent turbulent structures that form under different levels of atmospheric stability and surface roughness have important effects on wind turbine structural response, power production, and wake evolution.

Churchfield, M. J.; Lee, S.; Michalakes, J.; Moriarty, P. J.

2012-01-01T23:59:59.000Z

105

A neural network control strategy for improved energy capture on a variable-speed wind turbine  

Science Conference Proceedings (OSTI)

Pitch control has so far been the dominating method for power control in modern variable speed wind turbines. This paper proposes an improved control technique for pitching the blades of a variable speed wind turbine, using Artificial Neural Networks ... Keywords: artificial neural networks, control trajectories, pitch control, variable-speed wind turbines

António F. Silva; Fernando A. Castro; José N. Fidalgo

2005-06-01T23:59:59.000Z

106

Full vector (3-D) inflow simulation in natural and wind farm environments using an expanded version of the SNLWIND (Veers) turbulence code  

DOE Green Energy (OSTI)

We have recently expanded the numerical turbulence simulation (SNLWIND) developed by Veers [1] to include all three components of the turbulent wind vector. We have also configured the code to simulate the characteristics of turbulent wind fields upwind and downwind of a large wind farm, as well as over uniform, flat terrain. Veers`s original method only simulates the longitudinal component of the wind in neutral flow. This paper overviews the development of spectral distribution, spatial coherence, and cross correlation models used to expired the SNLWIND code to include the three components of the turbulent wind over a range of atmospheric stabilities. These models are based on extensive measurements of the turbulence characteristics immediately upwind and downwind of a large wind farm in San Gorgonio Pass, California.

Kelley, N.D.

1992-11-01T23:59:59.000Z

107

Full vector (3-D) inflow simulation in natural and wind farm environments using an expanded version of the SNLWIND (Veers) turbulence code  

DOE Green Energy (OSTI)

We have recently expanded the numerical turbulence simulation (SNLWIND) developed by Veers [1] to include all three components of the turbulent wind vector. We have also configured the code to simulate the characteristics of turbulent wind fields upwind and downwind of a large wind farm, as well as over uniform, flat terrain. Veers's original method only simulates the longitudinal component of the wind in neutral flow. This paper overviews the development of spectral distribution, spatial coherence, and cross correlation models used to expired the SNLWIND code to include the three components of the turbulent wind over a range of atmospheric stabilities. These models are based on extensive measurements of the turbulence characteristics immediately upwind and downwind of a large wind farm in San Gorgonio Pass, California.

Kelley, N.D.

1992-11-01T23:59:59.000Z

108

Cascade and Damping of Alfvén-Cyclotron Fluctuations: Application to Solar Wind Turbulence Spectrum  

E-Print Network (OSTI)

With the diffusion approximation, we study the cascade and damping of Alfv\\'{e}n-cyclotron fluctuations in solar plasmas numerically. Motivated by wave-wave couplings and nonlinear effects, we test several forms of the diffusion tensor. For a general locally anisotropic and inhomogeneous diffusion tensor in the wave vector space, the turbulence spectrum in the inertial range can be fitted with power-laws with the power-law index varying with the wave propagation direction. For several locally isotropic but inhomogeneous diffusion coefficients, the steady-state turbulence spectra are nearly isotropic in the absence of damping and can be fitted by a single power-law function. However, the energy flux is strongly polarized due to the inhomogeneity that leads to an anisotropic cascade. Including the anisotropic thermal damping, the turbulence spectrum cuts off at the wave numbers, where the damping rates become comparable to the cascade rates. The combined anisotropic effects of cascade and damping make this cutoff wave number dependent on the wave propagation direction, and the propagation direction integrated turbulence spectrum resembles a broken power-law, which cuts off at the maximum of the cutoff wave numbers or the $^4$He cyclotron frequency. Taking into account the Doppler effects, the model can naturally reproduce the broken power-law wave spectra observed in the solar wind and predicts that a higher break frequency is aways accompanied with a greater spectral index change that may be caused by the increase of the Alfv\\'{e}n Mach number, the reciprocal of the plasma beta, and/or the angle between the solar wind velocity and the mean magnetic field. These predictions can be tested by future observations.

Yan Wei Jiang; Siming Liu; Vahé Petrosian; Christopher L. Fryer

2008-02-07T23:59:59.000Z

109

Chaotic mean wind in turbulent thermal convection and long-term correlations in solar activity  

E-Print Network (OSTI)

It is shown that correlation function of the mean wind velocity in a turbulent thermal convection (Rayleigh number $Ra \\sim 10^{11}$) exhibits exponential decay with a very long correlation time, while corresponding largest Lyapunov exponent is certainly positive. These results together with the reconstructed phase portrait indicate presence of a chaotic component in the examined mean wind. Telegraph approximation is also used to study relative contribution of the chaotic and stochastic components to the mean wind fluctuations and an equilibrium between these components has been studied. Since solar activity is based on the thermal convection processes, it is reasoned that the observed solar activity long-term correlations can be an imprint of the mean wind chaotic properties. In particular, correlation function of the daily sunspots number exhibits exponential decay with a very long correlation time and corresponding largest Lyapunov exponent is certainly positive, also relative contribution of the chaotic and stochastic components follows the same pattern as for the convection mean wind.

A. Bershadskii

2009-08-27T23:59:59.000Z

110

Synoptic Variability of Ocean–Atmosphere Turbulent Fluxes Associated with Atmospheric Cyclones  

Science Conference Proceedings (OSTI)

Synoptic-scale variability in the air–sea turbulent fluxes in the areas of midlatitudinal western boundary currents is analyzed. In the Gulf Stream area, ocean–atmosphere fluxes on synoptic time- and space scales are clearly coordinated with the ...

Olga Zolina; Sergey K. Gulev

2003-08-01T23:59:59.000Z

111

TURBULENCE-DRIVEN POLAR WINDS FROM T TAURI STARS ENERGIZED BY MAGNETOSPHERIC ACCRETION  

E-Print Network (OSTI)

Pre-main-sequence stars are observed to be surrounded by both accretion flows and some kind of wind or jetlike outflow. Recent work by Matt and Pudritz has suggested that if classical T Tauri stars exhibit stellar winds with massloss rates about 0.1 times their accretion rates, the wind can carry away enough angular momentum to keep the stars from being spun up unrealistically by accretion. This paper presents a preliminary set of theoretical models of accretiondriven winds from the polar regions of T Tauri stars. These models are based on recently published self-consistent simulations of the Sun’s coronal heating and wind acceleration. In addition to the convection-driven MHD turbulence (which dominates in the solar case), we add another source of wave energy at the photosphere that is driven by the impact of plasma in neighboring flux tubes undergoing magnetospheric accretion. This added energy, determined quantitatively from the far-field theory of MHD wave generation, is sufficient to produce T TauriYlike mass-loss rates of at least 0.01 times the accretion rate. While still about an order of magnitude below the level required for efficient angular momentum removal, these are the first self-consistent models of T Tauri winds that agree reasonably well with a range of observational mass-loss constraints. The youngest modeled stellar winds are supported by Alfvén wave pressure, they have low temperatures (‘‘extended chromospheres’’), and they are likely to be unstable to the formation of counterpropagating shocks and clumps far from the star.

Steven R. Cranmer

2008-01-01T23:59:59.000Z

112

Variable speed wind turbine generator with zero-sequence filter  

DOE Patents (OSTI)

A variable speed wind turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator windings of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator windings. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility. 14 figs.

Muljadi, E.

1998-08-25T23:59:59.000Z

113

Variable Speed Wind Turbine Generator with Zero-sequence Filter  

DOE Patents (OSTI)

A variable speed wind turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator windings of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator windings. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility.

Muljadi, Eduard (Golden, CO)

1998-08-25T23:59:59.000Z

114

Variable speed wind turbine generator with zero-sequence filter  

DOE Patents (OSTI)

A variable speed wind turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator windings of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator windings. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility.

Muljadi, Eduard (Golden, CO)

1998-01-01T23:59:59.000Z

115

Flow visualization using momentum and energy transport tubes and applications to turbulent flow in wind farms  

E-Print Network (OSTI)

As a generalization of the mass-flux based classical stream-tube, the concept of momentum and energy transport tubes is discussed as a flow visualization tool. These transport tubes have the property, respectively, that no fluxes of momentum or energy exist over their respective tube mantles. As an example application using data from large-eddy simulation, such tubes are visualized for the mean-flow structure of turbulent flow in large wind farms, in fully developed wind-turbine-array boundary layers. The three-dimensional organization of energy transport tubes changes considerably when turbine spacings are varied, enabling the visualization of the path taken by the kinetic energy flux that is ultimately available at any given turbine within the array.

Meyers, Johan

2012-01-01T23:59:59.000Z

116

Self-consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence  

E-Print Network (OSTI)

We present a series of models for the plasma properties along open magnetic flux tubes rooted in solar coronal holes, streamers, and active regions. These models represent the first self-consistent solutions that combine: (1) chromospheric heating driven by an empirically guided acoustic wave spectrum, (2) coronal heating from Alfven waves that have been partially reflected, then damped by anisotropic turbulent cascade, and (3) solar wind acceleration from gradients of gas pressure, acoustic wave pressure, and Alfven wave pressure. The only input parameters are the photospheric lower boundary conditions for the waves and the radial dependence of the background magnetic field along the flux tube. For a single choice for the photospheric wave properties, our models produce a realistic range of slow and fast solar wind conditions by varying only the coronal magnetic field. Specifically, a 2D model of coronal holes and streamers at solar minimum reproduces the latitudinal bifurcation of slow and fast streams seen by Ulysses. The radial gradient of the Alfven speed affects where the waves are reflected and damped, and thus whether energy is deposited below or above the Parker critical point. As predicted by earlier studies, a larger coronal ``expansion factor'' gives rise to a slower and denser wind, higher temperature at the coronal base, less intense Alfven waves at 1 AU, and correlative trends for commonly measured ratios of ion charge states and FIP-sensitive abundances that are in general agreement with observations. These models offer supporting evidence for the idea that coronal heating and solar wind acceleration (in open magnetic flux tubes) can occur as a result of wave dissipation and turbulent cascade. (abridged abstract)

Steven R. Cranmer; Adriaan A. van Ballegooijen; Richard J. Edgar

2007-03-13T23:59:59.000Z

117

Turbulence in the sub-Alfv\\'enic solar wind driven by reflection of low-frequency Alfv\\'en waves  

E-Print Network (OSTI)

We study the formation and evolution of a turbulent spectrum of Alfv\\'en waves driven by reflection off the solar wind density gradients, starting from the coronal base up to 17 solar radii, well beyond the Alfv\\'enic critical point. The background solar wind is assigned and 2D shell models are used to describe nonlinear interactions. We find that the turbulent spectra are influenced by the nature of reflected waves. Close to the base, these give rise to a flatter and steeper spectrum for the outgoing and reflected waves respectively. At higher heliocentric distance both spectra evolve toward an asymptotic Kolmogorov spectrum. The turbulent dissipation is found to account for at least half of the heating required to sustain the background imposed solar wind and its shape is found to be determined by the reflection-determined turbulent heating below 1.5 solar radii. Therefore reflection and reflection-driven turbulence are shown to play a key role in the accelerationof the fast solar wind and origin of the tur...

Verdini, A; Buchlin, E

2009-01-01T23:59:59.000Z

118

Numerical simulation to determine the effects of incident wind shear and turbulence level on the flow around a building  

Science Conference Proceedings (OSTI)

The effects of incident shear and turbulence on flow around a cubical building are being investigated by a turbulent kinetic energy/dissipation model (TEMPEST). The numerical simulations demonstrate significant effects due to the differences in the incident flow. The addition of upstream turbulence and shear results in a reduced size of the cavity directly behind the building. The accuracy of numerical simulations is verified by comparing the predicted mean flow fields with the available wind-tunnel measurements of Castro and Robins (1977). Comparing the authors' results with experimental data, the authors show that the TEMPEST model can reasonably simulate the mean flow.

Zhang, Y.Q.; Huber, A.H.; Arya, S.P.S.; Snyder, W.H.

1992-01-01T23:59:59.000Z

119

A variable speed wind generator maximum power tracking based on adaptative neuro-fuzzy inference system  

Science Conference Proceedings (OSTI)

The power from wind varies depending on the environmental factors. Many methods have been proposed to locate and track the maximum power point (MPPT) of the wind, such as the fuzzy logic (FL), artificial neural network (ANN) and neuro-fuzzy. In this ... Keywords: ANFIS, MPPT, Power generation, Variable speed wind generator, Wind energy

A. Meharrar; M. Tioursi; M. Hatti; A. Boudghčne Stambouli

2011-06-01T23:59:59.000Z

120

Estimators for the Standard Deviation of Horizontal Wind Direction  

Science Conference Proceedings (OSTI)

The standard deviation of horizontal wind direction is a central quantity in the description of atmospheric turbulence and of great practical use in dispersion models. As horizontal wind direction is a circular variable, its standard deviation ...

Rudolf O. Weber

1997-10-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Sliding Mode Power Control of Variable Speed Wind Energy Conversion Systems  

E-Print Network (OSTI)

Sliding Mode Power Control of Variable Speed Wind Energy Conversion Systems B. Beltran, T. Ahmed power generation in variable speed wind energy conversion systems (VS-WECS). These systems have two (National Renewable Energy Laboratory) wind turbine simulator FAST (Fatigue, Aerodynamics, Structures

Brest, Université de

122

Co-existence of whistler waves with kinetic Alfven wave turbulence for the high-beta solar wind plasma  

SciTech Connect

It is shown that the dispersion relation for whistler waves is identical for a high or low beta plasma. Furthermore, in the high-beta solar wind plasma, whistler waves meet the Landau resonance with electrons for velocities less than the thermal speed, and consequently, the electric force is small compared to the mirror force. As whistlers propagate through the inhomogeneous solar wind, the perpendicular wave number increases through refraction, increasing the Landau damping rate. However, the whistlers can survive because the background kinetic Alfven wave (KAW) turbulence creates a plateau by quasilinear (QL) diffusion in the solar wind electron distribution at small velocities. It is found that for whistler energy density of only {approx}10{sup -3} that of the kinetic Alfven waves, the quasilinear diffusion rate due to whistlers is comparable to KAW. Thus, very small amplitude whistler turbulence can have a significant consequence on the evolution of the solar wind electron distribution function.

Mithaiwala, Manish; Crabtree, Chris; Ganguli, Gurudas [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375-5346 (United States); Rudakov, Leonid [Icarus Research Inc., P.O. Box 30780, Bethesda, Maryland 20824-0780 (United States)

2012-10-15T23:59:59.000Z

123

Probability density function method for variable-density pressure-gradient-driven turbulence and mixing  

SciTech Connect

Probability density function (PDF) methods are extended to variable-density pressure-gradient-driven turbulence. We apply the new method to compute the joint PDF of density and velocity in a non-premixed binary mixture of different-density molecularly mixing fluids under gravity. The full time-evolution of the joint PDF is captured in the highly non-equilibrium flow: starting from a quiescent state, transitioning to fully developed turbulence and finally dissipated by molecular diffusion. High-Atwood-number effects (as distinguished from the Boussinesq case) are accounted for: both hydrodynamic turbulence and material mixing are treated at arbitrary density ratios, with the specific volume, mass flux and all their correlations in closed form. An extension of the generalized Langevin model, originally developed for the Lagrangian fluid particle velocity in constant-density shear-driven turbulence, is constructed for variable-density pressure-gradient-driven flows. The persistent small-scale anisotropy, a fundamentally 'non-Kolmogorovian' feature of flows under external acceleration forces, is captured by a tensorial diffusion term based on the external body force. The material mixing model for the fluid density, an active scalar, is developed based on the beta distribution. The beta-PDF is shown to be capable of capturing the mixing asymmetry and that it can accurately represent the density through transition, in fully developed turbulence and in the decay process. The joint model for hydrodynamics and active material mixing yields a time-accurate evolution of the turbulent kinetic energy and Reynolds stress anisotropy without resorting to gradient diffusion hypotheses, and represents the mixing state by the density PDF itself, eliminating the need for dubious mixing measures. Direct numerical simulations of the homogeneous Rayleigh-Taylor instability are used for model validation.

Bakosi, Jozsef [Los Alamos National Laboratory; Ristorcelli, Raymond J [Los Alamos National Laboratory

2010-01-01T23:59:59.000Z

124

Measurement in a wind tunnel of the modification of mean wind and turbulence characteristics due to induction effects near wind turbine rotors  

DOE Green Energy (OSTI)

It is the purpose of this report to provide experimental data on the wind field surrounding a single model wind turbine rotor disk. These data should provide an improved physical insight into the induction effects of the air flow as it approaches the wind turbine. This insight should in turn improve an analytical model's predictive capabilities. A scaled model of a horizontal-axis wind turbine (a two-bladed rotor of diameter 53 cm) was placed into the Meteorological Wind Tunnel (MWT) facility at Colorado State University (cross-section width of 183 cm). Four different approach flow conditions were studied: low and moderate turbulence levels (0.1% and 1.5% intensity) at both 6 and 7.6 m/s freestream air velocities. For each of these flow conditions the rotor power coefficient versus tip speed ratio was obtained, and the 3-dimensional velocity field from 3 rotor diameters upwind to 0.5 diameter downwind was tabulated. The power output of the rotor was obtained via a simple prony brake friction device that imparts a torque (measured by the deflection of a spring) to the spinning shaft of the wind turbine. The rotor speed, measured by a strobe light, was observed to vary with load from 900 rpm up to 2100 rpm for the flow conditions described above. The 3-dimensional velocity field was measured via a three-hot-film probe. Details of the measurement techniques are provided. The test program and data results are also given. A short discussion of the implications of this data set is included. 12 refs., 19 figs., 11 tabs.

Neff, D.E.; Meroney, R.N.

1987-08-01T23:59:59.000Z

125

Wave-Turbulence interactions in the Upper Ocean. Part I: The Energy Balance of the Interacting Fields of Surface Wind Waves and Wind-Induced Three-Dimensional Turbulence  

Science Conference Proceedings (OSTI)

We analyze in detail the budget of total and fluctuating energy in the surface layer of the ocean. We suggest a rational scheme for separating the budget of turbulence from that of random wind-generated surface waves, and suggest in particular a ...

S. A. Kitaigorodskii; J. L. Lumley

1983-11-01T23:59:59.000Z

126

Pitch-Controlled Variable-Speed Wind Turbine Generation  

NLE Websites -- All DOE Office Websites (Extended Search)

Pitch-Controlled Variable-Speed Pitch-Controlled Variable-Speed Wind Turbine Generation February 2000 * NREL/CP-500-27143 E. Muljadi and C.P. Butterfield Presented at the 1999 IEEE Industry Applications Society Annual Meeting Phoenix, Arizona October 3-7, 1999 National Renewable Energy Laboratory 1617 Cole Boulevard Golden, Colorado 80401-3393 NREL is a U.S. Department of Energy Laboratory Operated by Midwest Research Institute * * * * Battelle * * * * Bechtel Contract No. DE-AC36-99-GO10337 NOTICE The submitted manuscript has been offered by an employee of the Midwest Research Institute (MRI), a contractor of the US Government under Contract No. DE-AC36-99GO10337. Accordingly, the US Government and MRI retain a nonexclusive royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for US Government purposes.

127

Low-Frequency Variability and Remote Forcing of Gap Winds over the East Pacific Warm Pool  

Science Conference Proceedings (OSTI)

The low-frequency variability of gap winds at the Isthmuses of Tehuantepec and Papagayo is investigated using a 17-yr wind stress dataset merging the remotely sensed observations of Special Sensor Microwave Imager (SSM/I) and Quick Scatterometer (...

Kristopher B. Karnauskas; Antonio J. Busalacchi; Raghu Murtugudde

2008-10-01T23:59:59.000Z

128

Wind Shear Enhancement of Entrainment and Refractive Index Structure Parameter at the Top of a Turbulent Mixed Layer  

Science Conference Proceedings (OSTI)

A model for inversion layer turbulence properties of a cloud-free entraining mixed-layer with wind shear at the top is developed. Using the approach of Wyngaard and LeMone (1980), expressions for the average values of ? and ?w2 in the entrainment ...

C. W. Fairall

1984-12-01T23:59:59.000Z

129

Power law burst and inter-burst interval distributions in the solar wind: turbulence or dissipative SOC ?  

E-Print Network (OSTI)

We calculate for the first time the probability density functions (PDFs) P of burst energy e, duration T and inter-burst interval tau for a known turbulent system in nature. Bursts in the earth-sun component of the Poynting flux at 1 AU in the solar wind were measured using the MFI and SWE experiments on the NASA WIND spacecraft. We find P(e) and P(T) to be power laws, consistent with self-organised criticality (SOC). We find also a power law form for P(tau) that distinguishes this turbulent cascade from the exponential P(tau) of ideal SOC, but not from some other SOC-like sandpile models. We discuss the implications for the relation between SOC and turbulence.

M. P. Freeman; N. W. Watkins; D. J. Riley

2000-03-08T23:59:59.000Z

130

Variations of Winds and Turbulence Seen by the 50-MHz Radar at White Sands Missile Range, New Mexico  

Science Conference Proceedings (OSTI)

The mean vertical profiles of the winds from about 5 to 20 km at White Sands Missile Range, New Mexico, are described. The variability of wind speed, spectral width, volume reflectivity calibrated as CN2, and vertical wind shear are documented as ...

G. D. Nastrom; F. D. Eaton

1995-10-01T23:59:59.000Z

131

Wake Turbulence of Two NREL 5-MW Wind Turbines Immersed in a Neutral Atmospheric Boundary-Layer Flow  

E-Print Network (OSTI)

The fluid dynamics video considers an array of two NREL 5-MW turbines separated by seven rotor diameters in a neutral atmospheric boundary layer (ABL). The neutral atmospheric boundary-layer flow data were obtained from a precursor ABL simulation using a Large-Eddy Simulation (LES) framework within OpenFOAM. The mean wind speed at hub height is 8m/s, and the surface roughness is 0.2m. The actuator line method (ALM) is used to model the wind turbine blades by means of body forces added to the momentum equation. The fluid dynamics video shows the root and tip vortices emanating from the blades from various viewpoints. The vortices become unstable and break down into large-scale turbulent structures. As the wakes of the wind turbines advect further downstream, smaller-scale turbulence is generated. It is apparent that vortices generated by the blades of the downstream wind turbine break down faster due to increased turbulence levels generated by the wake of the upstream wind turbine.

Bashioum, Jessica L; Schmitz, Sven; Duque, Earl P N

2013-01-01T23:59:59.000Z

132

ON THE LOW-FREQUENCY BOUNDARY OF SUN-GENERATED MAGNETOHYDRODYNAMIC TURBULENCE IN THE SLOW SOLAR WIND  

Science Conference Proceedings (OSTI)

New aspects of the slow solar wind turbulent heating and acceleration are investigated. A physical meaning of the lower boundary of the Alfven wave turbulent spectra in the solar atmosphere and the solar wind is studied and the significance of this natural parameter is demonstrated. Via an analytical and quantitative treatment of the problem we show that a truncation of the wave spectra from the lower frequency side, which is a consequence of the solar magnetic field structure and its cyclic changes, results in a significant reduction of the heat production and acceleration rates. An appropriate analysis is presented regarding the link of the considered problem with existing observational data and slow solar wind initiation scenarios.

Shergelashvili, Bidzina M.; Fichtner, Horst [Institut fuer Theoretische Physik IV, Weltraum- und Astrophysik, Ruhr-Universitaet Bochum, 44780 Bochum (Germany)

2012-06-20T23:59:59.000Z

133

New Report: Integrating Variable Wind Energy into the Grid | Department of  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Report: Integrating Variable Wind Energy into the Grid Report: Integrating Variable Wind Energy into the Grid New Report: Integrating Variable Wind Energy into the Grid December 19, 2011 - 2:00pm Addthis The Energy Department and Alstom Grid announce the availability of a new report on integrating wind energy into the electrical grid. | Image source: The Strategies and Decision Support Systems for Integrating Variable Energy Resources in Control Centers for Reliable Grid Operations Report. The Energy Department and Alstom Grid announce the availability of a new report on integrating wind energy into the electrical grid. | Image source: The Strategies and Decision Support Systems for Integrating Variable Energy Resources in Control Centers for Reliable Grid Operations Report. Charlton I. Clark Integration Team Lead, Wind and Water Power Program

134

Systematic Controller Design Methodology for Variable-Speed Wind Turbines  

DOE Green Energy (OSTI)

Variable-speed, horizontal axis wind turbines use blade-pitch control to meet specified objectives for three operational regions. This paper provides a guide for controller design for the constant power production regime. A simple, rigid, non-linear turbine model was used to systematically perform trade-off studies between two performance metrics. Minimization of both the deviation of the rotor speed from the desired speed and the motion of the actuator is desired. The robust nature of the proportional-integral-derivative controller is illustrated, and optimal operating conditions are determined. Because numerous simulation runs may be completed in a short time, the relationship between the two opposing metrics is easily visualized.

Hand, M. M.; Balas, M. J.

2002-02-01T23:59:59.000Z

135

Grid Impacts of Wind Power Variability: Recent Assessments from a Variety of Utilities in the United States (Presentation)  

DOE Green Energy (OSTI)

Presentation for the European Wind Energy Conference held February 27--March 2, 2006, in Athens, Greece, showing grid impacts of wind power variability.

Parsons, B.

2006-03-01T23:59:59.000Z

136

Modelling and Analysis of Variable Speed Wind Turbines with Induction Generator during Grid  

E-Print Network (OSTI)

Modelling and Analysis of Variable Speed Wind Turbines with Induction Generator during Grid Fault Wind Turbines with Induction Generator during Grid Fault by Sigrid M. Bolik Institute of Energy turbine technology has undergone rapid developments. Growth in size and the optimization of wind turbines

Hansen, René Rydhof

137

The Association of Large-Scale Climate Variability and Teleconnections on Wind Energy Resource  

E-Print Network (OSTI)

The Association of Large-Scale Climate Variability and Teleconnections on Wind Energy Resource over on Wind Energy Resource over Europe and its Intermittency Pascal Kriesche* and Adam Schlosser* Abstract In times of increasing importance of wind power in the world's energy mix, this study focuses on a better

138

1980–2010 Variability in U.K. Surface Wind Climate  

Science Conference Proceedings (OSTI)

The climate of the northeast Atlantic region comprises substantial decadal variability in storminess. It also exhibits strong inter- and intra-annual variability in extreme high and low wind speed episodes. Here the authors quantify and discuss ...

Nick Earl; Steve Dorling; Richard Hewston; Roland von Glasow

2013-02-01T23:59:59.000Z

139

May 2013 PSERC Webinar: Managing Wind Variability with Self-Reserves and  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

May 2013 PSERC Webinar: Managing Wind Variability with May 2013 PSERC Webinar: Managing Wind Variability with Self-Reserves and Responsive Demand May 2013 PSERC Webinar: Managing Wind Variability with Self-Reserves and Responsive Demand April 9, 2013 - 10:40am Addthis The DOE-funded Power Systems Engineering Research Center (PSERC) is offering a free public webinar on managing wind variability in energy production. The webinar will be held Tuesday, May 7, 2013 from 2-3 p.m. No pre-registration is necessary. Using wind power to supply up to 20%, or more, of electrical demand is increasingly popular in policy mandates, yet is relatively untested in terms of actual system and market operations. This presentation will investigate the concept of self-reserves, wherein wind generators withhold a portion of forecasted energy production, via their hour-ahead schedule,

140

Modeling and design of control system for variable speed wind turbine in all operating region  

Science Conference Proceedings (OSTI)

In order to get the maximum power from the wind, the variable-speed wind turbine should run at different speed when wind speed changes. In this paper a control system is introduced to get this purpose base on establishing the three-mass model of the ... Keywords: doubly-fed induction generator (DFIG), feed-forward compensator, loop-shaping, pitch controller, speed controller, three-mass model, wind turbine

Wu Dingguo; Wang Zhixin

2008-05-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Seasonal variability of wind electric potential in the United States  

DOE Green Energy (OSTI)

Seasonal wind electric potential has been estimated for the contiguous United States based on the methods previously used to estimate the annual average wind electric potential. National maps show estimates of the seasonal wind electric potential averaged over the state as a whole, and gridded maps show the distribution of the seasonal wind electric potential within a state. The seasons of winter and spring have highest wind electric potential for most windy areas in the United States. Summer is the season with the least potential for most of the contiguous United States. Wind electric potential patterns in autumn generally resemble the annual average potential map. Excellent matches between seasonal wind electric potential and electric energy use occur during winter for the northern parts of the nation. California has a good match between summer wind potential and electric use.

Schwartz, M.N.; Elliott, D.L.; Gower, G.L.

1993-07-01T23:59:59.000Z

142

DIRECT NUMERICAL SIMULATION OF RADIATION PRESSURE-DRIVEN TURBULENCE AND WINDS IN STAR CLUSTERS AND GALACTIC DISKS  

SciTech Connect

The pressure exerted by the radiation of young stars may be an important feedback mechanism that drives turbulence and winds in forming star clusters and the disks of starburst galaxies. However, there is great uncertainty in how efficiently radiation couples to matter in these high optical depth environments. In particular, it is unclear what levels of turbulence the radiation can produce, and whether the infrared radiation trapped by the dust opacity can give rise to heavily mass-loaded winds. In this paper, we report a series of two-dimensional flux-limited diffusion radiation-hydrodynamics calculations performed with the code ORION in which we drive strong radiation fluxes through columns of dusty matter confined by gravity in order to answer these questions. We consider both systems where the radiation flux is sub-Eddington throughout the gas column, and those where it is super-Eddington at the midplane but sub-Eddington in the atmosphere. In the latter, we find that the radiation-matter interaction gives rise to radiation-driven Rayleigh-Taylor instability, which drives supersonic turbulence at a level sufficient to fully explain the turbulence seen in Galactic protocluster gas clouds, and to make a non-trivial contribution to the turbulence observed in starburst galaxy disks. However, the instability also produces a channel structure in which the radiation-matter interaction is reduced compared to time-steady analytic models because the radiation field is not fully trapped. For astrophysical parameters relevant to forming star clusters and starburst galaxies, we find that this effect reduces the net momentum deposition rate in the dusty gas by a factor of {approx}2-6 compared to simple analytic estimates, and that in steady state the Eddington ratio reaches unity and there are no strong winds. We provide an approximation formula, appropriate for implementation in analytic models and non-radiative simulations, for the force exerted by the infrared radiation field in this regime.

Krumholz, Mark R. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Thompson, Todd A., E-mail: krumholz@ucolick.org, E-mail: thompson@astronomy.ohio-state.edu [Department of Astronomy and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210-1173 (United States)

2012-12-01T23:59:59.000Z

143

Low-Order Modelling of Blade-Induced Turbulence for RANS Actuator Disk Computations of Wind and Tidal Turbines  

E-Print Network (OSTI)

Modelling of turbine blade-induced turbulence (BIT) is discussed within the framework of three-dimensional Reynolds-averaged Navier-Stokes (RANS) actuator disk computations. We first propose a generic (baseline) BIT model, which is applied only to the actuator disk surface, does not include any model coefficients (other than those used in the original RANS turbulence model) and is expected to be valid in the limiting case where BIT is fully isotropic and in energy equilibrium. The baseline model is then combined with correction functions applied to the region behind the disk to account for the effect of rotor tip vortices causing a mismatch of Reynolds shear stress between short- and long-time averaged flow fields. Results are compared with wake measurements of a two-bladed wind turbine model of Medici and Alfredsson [Wind Energy, Vol. 9, 2006, pp. 219-236] to demonstrate the capability of the new model.

Nishino, Takafumi

2012-01-01T23:59:59.000Z

144

Turbulence  

NLE Websites -- All DOE Office Websites (Extended Search)

Turbulence Turbulence in Alcator C-Mod and Wendelstein 7-AS plasmas during controlled confinement transitions N.P.Basse, E.M.Edlund, C.L.Fiore, M.J.Greenwald, A.E.Hubbard, J.W.Hughes, J.H.Irby, G.J.Kramer 1 , L.Lin, Y.Lin, A.G.Lynn 2 , E.S.Marmar, D.R.Mikkelsen 1 , D.Mossessian, P.E.Phillips 2 , M.Porkolab, J.E.Rice, W.L.Rowan 2 , J.A.Snipes, J.L.Terry, S.M.Wolfe, S.J.Wukitch, K.Zhurovich, S.Zoletnik 3 and the C-Mod and W7-AS 4 Teams MIT Plasma Science and Fusion Center, Cambridge, USA 1 Princeton Plasma Physics Laboratory, Princeton, USA 2 University of Texas at Austin, Austin, USA 3 KFKI-RMKI, EURATOM Association, Budapest, Hungary 4 Max-Planck-Institut f¨ ur Plasmaphysik, EURATOM Association, Greifswald, Germany At certain values of the edge rotational transform, ι a = 1/q a , the confinement time of plasmas in the Wendelstein 7-AS (W7-AS) stellarator was found to

145

A comparison of predicted and observed turbulent wind fields present in natural and internal wind park environments  

DOE Green Energy (OSTI)

This paper assesses the accuracy of simulated wind fields for both the natural flow and that within a wind park environment. The simulated fields are compared with the observed ones in both the time and frequency domains. Actual measurements of the wind fields and the derived kinematic scaling parameters upwind and downwind of a large San Gorgonio Pass wind park are used. The deviations in the modeled wind field from the observed are discussed. 10 refs., 6 figs., 2 tabs.

Kelly, N D; Wright, A D

1991-10-01T23:59:59.000Z

146

Atmospheric Circulation Effects on Wind Speed Variability at Turbine Height  

Science Conference Proceedings (OSTI)

Mean monthly wind speed at 70 m above ground level is investigated for 11 sites in Minnesota for the period 1995–2003. Wind speeds at these sites show significant spatial and temporal coherence, with prolonged periods of above- and below-normal ...

Katherine Klink

2007-04-01T23:59:59.000Z

147

Fixed-Speed and Variable-Slip Wind Turbines Providing Spinning Reserves to the Grid: Preprint  

DOE Green Energy (OSTI)

As the level of wind penetration increases, wind turbine technology must move from merely generating power from wind to taking a role in supporting the bulk power system. Wind turbines should have the capability to provide inertial response and primary frequency (governor) response so they can support the frequency stability of the grid. To provide governor response, wind turbines should be able to generate less power than the available wind power and hold the rest in reserve, ready to be accessed as needed. This paper explores several ways to control wind turbine output to enable reserve-holding capability. This paper focuses on fixed-speed (also known as Type 1) and variable-slip (also known as Type 2) turbines.

Muljadi, E.; Singh, M.; Gevorgian, V.

2012-11-01T23:59:59.000Z

148

Annual and Nonseasonal Variability of Monthly Low-Level Wind Fields over the Southeastern Tropical Pacific  

Science Conference Proceedings (OSTI)

The time and space variability of low-level winds over the Southeast Tropical Pacific (SETP) region is described for the 6-year period 1974–80. The data set consists of monthly averaged low-level cloud-motion vector winds supplemented by coastal ...

David B. Enfield

1981-10-01T23:59:59.000Z

149

Observed Interannual Variability of the Florida Current: Wind Forcing and the North Atlantic Oscillation  

Science Conference Proceedings (OSTI)

The role of wind stress curl (WSC) forcing in the observed interannual variability of the Florida Current (FC) transport is investigated. Evidence is provided for baroclinic adjustment as a physical mechanism linking interannual changes in WSC ...

Pedro N. DiNezio; Lewis J. Gramer; William E. Johns; Christopher S. Meinen; Molly O. Baringer

2009-03-01T23:59:59.000Z

150

May 2013 PSERC Webinar: Managing Wind Variability with Self-Reserves...  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

and Responsive Demand May 2013 PSERC Webinar: Managing Wind Variability with Self-Reserves and Responsive Demand April 9, 2013 - 10:40am Addthis The DOE-funded Power...

151

Sea Surface Temperature and Wind Stress Curl Variability near a Cape  

Science Conference Proceedings (OSTI)

The coupling between sea surface temperature (SST), SST gradients, and wind stress curl variability near a cape off Brazil is investigated using satellite observations and several different SST high-resolution analyses. The cape is characterized ...

Renato M. Castelao

2012-11-01T23:59:59.000Z

152

A fuzzy logic controller to increase fault ride-through capability of variable speed wind turbines  

Science Conference Proceedings (OSTI)

A fuzzy controller for improving Fault Ride-Through (FRT) capability of Variable Speed Wind Turbines (WTs) equipped with Doubly Fed Induction Generator (DFIG) is presented. The controller is designed in order to compensate the voltage at the Point of ...

Geev Mokryani, Pierluigi Siano, Antonio Piccolo, Vito Calderaro

2012-01-01T23:59:59.000Z

153

An Airborne and Wind Tunnel Evaluation of a Wind Turbulence Measurement System for Aircraft-Based Flux Measurements  

Science Conference Proceedings (OSTI)

Although the ability to measure vertical eddy fluxes of gases from aircraft platforms represents an important capability to obtain spatially resolved data, accurate and reliable determination of the turbulent vertical velocity presents a great ...

K. E. Garman; K. A. Hill; P. Wyss; M. Carlsen; J. R. Zimmerman; B. H. Stirm; T. Q. Carney; R. Santini; P. B. Shepson

2006-12-01T23:59:59.000Z

154

Relationships between Tornado Intensity and Various Wind and Thermodynamic Variables  

Science Conference Proceedings (OSTI)

Statistical relationships between tornado intensity and various stability and wind-related parameters are determined from a dataset of more than 200 tornado proximity soundings. Soundings were obtained from two sources: the University of Missouri ...

John R. Colquhoun; Philip A. Riley

1996-09-01T23:59:59.000Z

155

Variability of wind power near Oklahoma City and implications for siting of wind turbines  

SciTech Connect

Data from five sites near Oklahoma City were examined to assess wind power availability. Wind turbines of identical manufacture were operated at three of the sites, one of which was also equipped with anemometers on a 100-ft tower. Comprehensive anemometric data were available from the other two sites. The study indicates that the average wind speed varies substantially over Oklahoma's rolling plains, which have often been nominally regarded as flat for purposes of wind power generation. Average wind differences may be as much as 5 mph at 20 ft above ground level, and 7 mph at 100 ft above ground level for elevation differences of about 200 ft above mean sea level, even in the absence of substantial features of local terrain. Local altitude above mean sea level seems to be as influential as the shape of local terrain in determining the average wind speed. The wind turbine used at a meteorologically instrumented site in the study produced the power expected from it for the wind regime in which it was situated. The observed variations of local wind imply variations in annual kWh of as much as a factor of four between identical turbines located at similar heights above ground level in shallow valleys and on hilltops or elevated extended flat areas. 17 refs., 39 figs., 11 tabs.

Kessler, E.; Eyster, R.

1987-09-01T23:59:59.000Z

156

Adaptive pitch control for variable speed wind turbines  

DOE Patents (OSTI)

An adaptive method for adjusting blade pitch angle, and controllers implementing such a method, for achieving higher power coefficients. Average power coefficients are determined for first and second periods of operation for the wind turbine. When the average power coefficient for the second time period is larger than for the first, a pitch increment, which may be generated based on the power coefficients, is added (or the sign is retained) to the nominal pitch angle value for the wind turbine. When the average power coefficient for the second time period is less than for the first, the pitch increment is subtracted (or the sign is changed). A control signal is generated based on the adapted pitch angle value and sent to blade pitch actuators that act to change the pitch angle of the wind turbine to the new or modified pitch angle setting, and this process is iteratively performed.

Johnson, Kathryn E. (Boulder, CO); Fingersh, Lee Jay (Westminster, CO)

2012-05-08T23:59:59.000Z

157

Solar-wind turbulence and shear: a superposed-epoch analysis of corotating interaction regions at 1 AU  

Science Conference Proceedings (OSTI)

A superposed-epoch analysis of ACE and OMNI2 measurements is performed on 27 corotating interaction regions (CIRs) in 2003-2008, with the zero epoch taken to be the stream interface as determined by the maximum of the plasma vorticity. The structure of CIRs is investigated. When the flow measurements are rotated into the local-Parker-spiral coordinate system the shear is seen to be abrupt and intense, with vorticities on the order of 10{sup -5}-10{sup -4} sec{sup -1}. Converging flows perpendicular to the stream interface are seen in the local-Parker-spiral coordinate system and about half of the CIRs show a layer of divergent rebound flow away from the stream interface. Arguments indicate that any spreading of turbulence away from the region where it is produced is limited to about 10{sup 6} km, which is very small compared with the thickness of a CrR. Analysis of the turbulence across the CrRs is performed. When possible, the effects of discontinuities are removed from the data. Fluctuation amplitudes, the Alfvenicity, and the level of Alfvenic correlations all vary smoothly across the CrR. The Alfven ratio exhibits a decrease at the shear zone of the stream interface. Fourier analysis of 4.5-hr subintervals of ACE data is performed and the results are superposed averaged as an ensemble of realizations. The spectral slopes of the velocity, magnetic-field, and total-energy fluctuations vary smoothly across the CIR. The total-energy spectral slope is {approx} 3/2 in the slow and fast wind and in the CrRs. Analysis of the Elsasser inward-outward fluctuations shows a smooth transition across the CrR from an inward-outward balance in the slow wind to an outward dominance in the fast wind. A number of signatures of turbulence driving at the shear zone are sought (entropy change, turbulence amplitude, Alfvenicity, Alfven ratio, spectral slopes, in-out nature): none show evidence of driving of turbulence by shear.

Borovsky, Joseph E [Los Alamos National Laboratory; Denton, Michael H [LANCASTER UNIV.

2009-01-01T23:59:59.000Z

158

Wind Levelized Cost of Energy: A Comparison of Technical and Financing Input Variables  

DOE Green Energy (OSTI)

The expansion of wind power capacity in the United States has increased the demand for project development capital. In response, innovative approaches to financing wind projects have emerged and are proliferating in the U.S. renewable energy marketplace. Wind power developers and financiers have become more efficient and creative in structuring their financial relationships, and often tailor them to different investor types and objectives. As a result, two similar projects may use very different cash flows and financing arrangements, which can significantly vary the economic competitiveness of wind projects. This report assesses the relative impact of numerous financing, technical, and operating variables on the levelized cost of energy (LCOE) associated with a wind project under various financing structures in the U.S. marketplace. Under this analysis, the impacts of several financial and technical variables on the cost of wind electricity generation are first examined individually to better understand the relative importance of each. Then, analysts examine a low-cost and a high-cost financing scenario, where multiple variables are modified simultaneously. Lastly, the analysis also considers the impact of a suite of financial variables versus a suite of technical variables.

Cory, K.; Schwabe, P.

2009-10-01T23:59:59.000Z

159

Time and Space Variability of Tropical Pacific Wind Stress  

Science Conference Proceedings (OSTI)

The results of a spectral analysis of a new, subjectively analyzed data set of tropical Pacific wind stress are presented. The monthly data for the 10-year period, 1961–70, allow a detailed inspection of the distributions of frequency and zonal ...

Stanley B. Goldenberg; James J. O'Brien

1981-06-01T23:59:59.000Z

160

Advances in Fluid Modeling of the Solar Wind. Part 1: Electron and Anisotropic Proton Temperatures from the Collisionless Dissipation of Alfven Wave Turbulence  

E-Print Network (OSTI)

We develop a 1D solar-wind model that includes separate energy equations for the electrons and protons, proton temperature anisotropy, collisional and collisionless heat flux, and an analytical treatment of low-frequency, reflection-driven, Alfven-wave turbulence. To partition the turbulent heating between electron heating, parallel proton heating, and perpendicular proton heating, we employ results from the theories of linear wave damping and nonlinear stochastic heating. We account for mirror and oblique firehose instabilities by increasing the proton pitch-angle scattering rate when the proton temperature anisotropy exceeds the threshold for either instability. We numerically integrate the equations of the model forward in time until a steady state is reached, focusing on two fast-solar-wind-like solutions. These solutions are consistent with a number of observations, supporting the idea that Alfven-wave turbulence plays an important role in the origin of the solar wind.

Chandran, Benjamin D G; Quataert, Eliot; Bale, Stuart D

2011-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

INCORPORATING KINETIC PHYSICS INTO A TWO-FLUID SOLAR-WIND MODEL WITH TEMPERATURE ANISOTROPY AND LOW-FREQUENCY ALFVEN-WAVE TURBULENCE  

Science Conference Proceedings (OSTI)

We develop a one-dimensional solar-wind model that includes separate energy equations for the electrons and protons, proton temperature anisotropy, collisional and collisionless heat flux, and an analytical treatment of low-frequency, reflection-driven, Alfven-wave (AW) turbulence. To partition the turbulent heating between electron heating, parallel proton heating, and perpendicular proton heating, we employ results from the theories of linear wave damping and nonlinear stochastic heating. We account for mirror and oblique firehose instabilities by increasing the proton pitch-angle scattering rate when the proton temperature anisotropy exceeds the threshold for either instability. We numerically integrate the equations of the model forward in time until a steady state is reached, focusing on two fast-solar-wind-like solutions. These solutions are consistent with a number of observations, supporting the idea that AW turbulence plays an important role in the origin of the solar wind.

Chandran, Benjamin D. G.; Dennis, Timothy J. [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States); Quataert, Eliot [Astronomy Department and Theoretical Astrophysics Center, 601 Campbell Hall, University of California, Berkeley, CA 94720 (United States); Bale, Stuart D., E-mail: benjamin.chandran@unh.edu, E-mail: tim.dennis@unh.edu, E-mail: eliot@astro.berkeley.edu, E-mail: bale@ssl.berkeley.edu [Physics Department and Space Sciences Laboratory, 311 Old LeConte Hall, University of California, Berkeley, CA 94720 (United States)

2011-12-20T23:59:59.000Z

162

Controlled operation of variable speed driven permanent magnet synchronous generator for wind energy conversion systems  

Science Conference Proceedings (OSTI)

The introduction of distributed generation through renewable sources of energy has opened a challenging area for power engineers. As these sources are intermittent in nature, variable speed electric generators are employed for harnessing electrical energy ... Keywords: permanent magnet synchronous generator, power conditioners, power quality, variable speed generators, wind energy

Rajveer Mittal; K. S. Sandhu; D. K. Jain

2009-02-01T23:59:59.000Z

163

The Association of Large-Scale Climate Variability and Teleconnections on Wind Energy Resource over Europe and its Intermittency  

E-Print Network (OSTI)

In times of increasing importance of wind power in the world’s energy mix, this study focuses on a better understanding of the influences of large-scale climate variability on wind power resource over Europe. The impact ...

Kriesche, Pascal

164

Multi-winding Homopolar Electric Machine Offers Variable ...  

The device can be used as either a motor or a generator. Advantages • Variable voltage and speed design • Internal mechanism allowing for low speed, high

165

Measurement of Clear-Air Gradients and Turbulence Properties with Radar Wind Profilers  

Science Conference Proceedings (OSTI)

An experiment comparing balloon and profiler observations was carried out to evaluate the capability of Doppler radar wind profilers to remotely measure useful meteorological quantities other than wind. The site chosen was in Southern California ...

E. E. Gossard; D. E. Wolfe; K. P. Moran; R. A. Paulus; K. D. Anderson; L. T. Rogers

1998-04-01T23:59:59.000Z

166

Maximizing Energy Capture of Fixed-Pitch Variable-Speed Wind Turbines  

DOE Green Energy (OSTI)

Field tests of a variable-speed, stall-regulated wind turbine were conducted at a US Department of Energy Laboratory. A variable-speed generating system, comprising a doubly-fed generator and series-resonant power converter, was installed on a 275-kW, downwind, two-blade wind turbine. Gearbox, generator, and converter efficiency were measured in the laboratory so that rotor aerodynamic efficiency could be determined from field measurement of generator power. The turbine was operated at several discrete rotational speeds to develop power curves for use in formulating variable-speed control strategies. Test results for fixed-speed and variable-speed operation are presented along with discussion and comparison of the variable-speed control methodologies. Where possible, comparisons between fixed-speed and variable-speed operation are shown.

Pierce, K.; Migliore, P.

2000-08-01T23:59:59.000Z

167

Grid Impacts of Wind Power Variability: Recent Assessments from a Variety of Utilities in the United States; Preprint  

SciTech Connect

Because of wind power's unique characteristics, many concerns are based on the increased variability that wind contributes to the grid, and most U.S. studies have focused on this aspect of wind generation. Grid operators are also concerned about the ability to predict wind generation over several time scales. In this report, we quantify the physical impacts and costs of wind generation on grid operations and the associated costs.

Parsons, B.; Milligan, M.; Smith, J. C.; DeMeo, E.; Oakleaf, B.; Wolf, K.; Schuerger, M.; Zavadil, R.; Ahlstrom, M.; Nakafuji, D. Y.

2006-07-01T23:59:59.000Z

168

Grid Impacts of Wind Power Variability: Recent Assessments from a Variety of Utilities in the United States; Preprint  

DOE Green Energy (OSTI)

Because of wind power's unique characteristics, many concerns are based on the increased variability that wind contributes to the grid, and most U.S. studies have focused on this aspect of wind generation. Grid operators are also concerned about the ability to predict wind generation over several time scales. In this report, we quantify the physical impacts and costs of wind generation on grid operations and the associated costs.

Parsons, B.; Milligan, M.; Smith, J. C.; DeMeo, E.; Oakleaf, B.; Wolf, K.; Schuerger, M.; Zavadil, R.; Ahlstrom, M.; Nakafuji, D. Y.

2006-07-01T23:59:59.000Z

169

Petascale Simulations of Inhomogeneous AlfvĂ©n Turbulence in the Solar Wind  

NLE Websites -- All DOE Office Websites (Extended Search)

A snapshot of turbulent magnetic field lines (red) inside a coronal hole that expands from a small patch on the solar surface to 5 solar radii A snapshot of turbulent magnetic field lines (red) inside a coronal hole that expands from a small patch on the solar surface to 5 solar radii A snapshot of turbulent magnetic field lines (red) inside a coronal hole that expands from a small patch on the solar surface to 5 solar radii. Alfven waves (AW), launched by convective motions on the photosphere, propagate in the inhomogeneous Solar atmosphere producing primary reflected waves that interact non-linearly with the outward waves, driving a turbulent cascade. This cascade continues with secondary reflections in a very complex interplay between wave reflections and nonlinear interactions. Selected slices across the simulation domain show contours of plasma current, indicating the generation of small scale structures where the

170

Wind Mixing In a Turbulent Surface Layer in the Presence of a Horizontal Density Gradient  

Science Conference Proceedings (OSTI)

The effect of a horizontal density gradient of buoyancy on the turbulent kinetic energy budget of the surface mixed layer in the ocean is discussed. The combination of a horizontal buoyancy gradient and a vertical shear of the horizontal velocity ...

Johan Rodhe

1991-07-01T23:59:59.000Z

171

Lagrangian Coherent Structure Analysis of Terminal Winds Detected by Lidar. Part I: Turbulence Structures  

Science Conference Proceedings (OSTI)

The accurate real-time detection of turbulent airflow patterns near airports is important for safety and comfort in commercial aviation. In this paper, a method is developed to identify Lagrangian coherent structures (LCS) from horizontal lidar ...

Wenbo Tang; Pak Wai Chan; George Haller

2011-02-01T23:59:59.000Z

172

Near-Surface Turbulence and Thermal Structure in a Wind-Driven Sea  

Science Conference Proceedings (OSTI)

Ocean surface turbulence at high sea states is evaluated using heat as a naturally occurring passive tracer. A freely drifting instrument with a mechanically driven temperature profiler, fixed depth thermistors, and conductivity cells was used to ...

Johannes R. Gemmrich; David M. Farmer

1999-03-01T23:59:59.000Z

173

A Wind Tunnel Study of Turbulence Effects on the Scavenging of Aerosol Particles by Water Drops  

Science Conference Proceedings (OSTI)

Laboratory experiments are described where the effects of turbulence on the impaction scavenging of aerosol particles by water drops were investigated. During the experiments the drops were freely suspended at their terminal velocities in the ...

O. Vohl; S. K. Mitra; K. Diehl; G. Huber; S. C. Wurzler; K-L. Kratz; H. R. Pruppacher

2001-10-01T23:59:59.000Z

174

Power-Electronic, Variable-Speed Wind Turbine Development: 1988-1993  

Science Conference Proceedings (OSTI)

A five-year development program culminated in the 33M-VS power-electronic, variable-speed turbine, used in a number of wind power plants to offer competitively priced electricity. This report describes turbine development activities from conception through field testing, highlights design decisions that led to the new technology, and provides an overview of the turbine's electrical and mechanical design. An appendix describes technical issues relevant to building a wind power plant using 33M-VS turbines.

1995-11-16T23:59:59.000Z

175

Optimal Self Tuned Variable Structure Sliding Mode for Coordinated Wind-FC-Diesel Utilization Scheme  

Science Conference Proceedings (OSTI)

The modeling and coordinated control strategy based on self tuned variable structure sliding mode dynamic controller for a wind–diesel-fuel cell renewable generation system with battery backup are discussed in this paper. The proposed hybrid scheme ... Keywords: Diesel-driven generator, Wind induction generator, PMDC motor drives, fuel cell, Backup Battery, Dynamic Filter Compensator, Green Power Filter, Multi Objective Particle Swarm Optimization MOPSO

Adel M. Sharaf; Adel A. A. El-Gammal

2010-05-01T23:59:59.000Z

176

Effects of variable wind stress on ocean heat content  

E-Print Network (OSTI)

Ocean heat content change (ocean heat uptake) has an important role in variability of the Earth's heat balance. The understanding of which methods and physical processes control ocean heat uptake needs improvement in order ...

Klima, Kelly

2008-01-01T23:59:59.000Z

177

Low-Frequency Variability in the Wind-Driven Circulation  

Science Conference Proceedings (OSTI)

The origins of low-frequency variability in a simple homogenous ocean model, forced by a double gyre Ekman suction, are examined numerically. It is found that irregular, large amplitude vacillations in the structure of the circulation typify the ...

S. P. Meacham

2000-02-01T23:59:59.000Z

178

Stability analysis of a variable-speed wind turbine  

DOE Green Energy (OSTI)

This paper examines the elastomechanical stability of a four-bladed wind turbine over a specific rotor speed range. Stability modes, frequencies, and dampings are extracted using a specialized modal processor developed at NREL that post-processes the response data generated by the ADAMS simulation code. The processor can analyze a turbine with an arbitrary number of rotor blades and offers a novel capability of isolating stability modes that become locked at a single frequency. Results indicate that over a certain rotor speed range, the tower lateral mode and the rotor regressive in-plane mode coalesce, resulting in a self-excited instability. Additional results show the effect of tower and nacelle parameters on the stability boundaries.

Bir, G.S.; Wright, A.D.; Butterfield, C.P.

1996-10-01T23:59:59.000Z

179

Analysis of Variability and Uncertainty in Wind Power Forecasting: An International Comparison: Preprint  

DOE Green Energy (OSTI)

One of the critical challenges of wind power integration is the variable and uncertain nature of the resource. This paper investigates the variability and uncertainty in wind forecasting for multiple power systems in six countries. An extensive comparison of wind forecasting is performed among the six power systems by analyzing the following scenarios: (i) wind forecast errors throughout a year; (ii) forecast errors at a specific time of day throughout a year; (iii) forecast errors at peak and off-peak hours of a day; (iv) forecast errors in different seasons; (v) extreme forecasts with large overforecast or underforecast errors; and (vi) forecast errors when wind power generation is at different percentages of the total wind capacity. The kernel density estimation method is adopted to characterize the distribution of forecast errors. The results show that the level of uncertainty and the forecast error distribution vary among different power systems and scenarios. In addition, for most power systems, (i) there is a tendency to underforecast in winter; and (ii) the forecasts in winter generally have more uncertainty than the forecasts in summer.

Zhang, J.; Hodge, B. M.; Gomez-Lazaro, E.; Lovholm, A. L.; Berge, E.; Miettinen, J.; Holttinen, H.; Cutululis, N.; Litong-Palima, M.; Sorensen, P.; Dobschinski, J.

2013-10-01T23:59:59.000Z

180

Predicting the Energy Output of Wind Farms Based on Weather Data: Important Variables and their Correlation  

E-Print Network (OSTI)

Wind energy plays an increasing role in the supply of energy world-wide. The energy output of a wind farm is highly dependent on the weather condition present at the wind farm. If the output can be predicted more accurately, energy suppliers can coordinate the collaborative production of different energy sources more efficiently to avoid costly overproductions. With this paper, we take a computer science perspective on energy prediction based on weather data and analyze the important parameters as well as their correlation on the energy output. To deal with the interaction of the different parameters we use symbolic regression based on the genetic programming tool DataModeler. Our studies are carried out on publicly available weather and energy data for a wind farm in Australia. We reveal the correlation of the different variables for the energy output. The model obtained for energy prediction gives a very reliable prediction of the energy output for newly given weather data.

Vladislavleva, Katya; Neumann, Frank; Wagner, Markus

2011-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Tomographic Simulations of Accretion Disks in Cataclysmic Variables - Flickering and Wind  

E-Print Network (OSTI)

Both continuum and emission line flickering are phenomena directly associated with the mass accretion process. In this work we simulate accretion disk Doppler maps including the effects of winds and flickering flares. Synthetic flickering Doppler maps are calculated and the effect of the flickering parameters on the maps is explored. Jets and winds occur in many astrophysical objects where accretion disks are present. Jets are generally absent among the cataclysmic variables (CVs), but there is evidence of mass loss by wind in many objects. CVs are ideal objects to study accretion disks and consequently to study the wind associated with these disks. We also present simulations of accretion disks including the presence of a wind with orbital phase resolution. Synthetic H-alpha line profiles in the optical region are obtained and their corresponding Doppler maps are calculated. The effect of the wind simulation parameters on the wind line profiles is also explored. From this study we verified that optically thick lines and/or emission by diffuse material into the primary Roche lobe are necessary to generate single peaked line profiles, often seen in CVs. The future accounting of these effects is suggested for interpreting Doppler tomography reconstructions.

Fabiola M. A. Ribeiro; Marcos P. Diaz

2007-11-22T23:59:59.000Z

182

The winds of Luminous Blue Variables and the Mass of AG Car  

E-Print Network (OSTI)

We present radiation-driven wind models for Luminous Blue Variables (LBVs) and predict their mass-loss rates. A comparison between our predictions and the observations of AG Car shows that the variable mass loss behaviour of LBVs is due the recombination/ionisation of Fe IV/III and Fe III/II. We also derive a present-day mass of 35 Msun for AG Car.

Jorick S. Vink; Alex de Koter

2002-07-15T23:59:59.000Z

183

Modeling and Model Validation for Variable Generation Technologies: Focus on Wind Generation  

Science Conference Proceedings (OSTI)

The influx of variable-generation technologies, particularly wind generation, into the bulk transmission grid has been tremendous over the past decade. This trend will likely continue, in light of national and state renewable portfolio standards. Thus, there is a need for generic, standard, and publicly available models for variable-generation technologies for power system planning studies. The Electric Power Research Institute (EPRI), in collaboration with the Western Electricity Coordinating Council (...

2010-12-14T23:59:59.000Z

184

Variable Frequency Operations of an Offshore Wind Power Plant with HVDC-VSC: Preprint  

DOE Green Energy (OSTI)

In this paper, a constant Volt/Hz operation applied to the Type 1 wind turbine generator. Various control aspects of Type 1 generators at the plant level and at the turbine level will be investigated. Based on DOE study, wind power generation may reach 330 GW by 2030 at the level of penetration of 20% of the total energy production. From this amount of wind power, 54 GW of wind power will be generated at offshore wind power plants. The deployment of offshore wind power plants requires power transmission from the plant to the load center inland. Since this power transmission requires submarine cable, there is a need to use High-Voltage Direct Current (HVDC) transmission. Otherwise, if the power is transmitted via alternating current, the reactive power generated by the cable capacitance may cause an excessive over voltage in the middle of the transmission distance which requires unnecessary oversized cable voltage breakdown capability. The use of HVDC is usually required for transmission distance longer than 50 kilometers of submarine cables to be economical. The use of HVDC brings another advantage; it is capable of operating at variable frequency. The inland substation will be operated to 60 Hz synched with the grid, the offshore substation can be operated at variable frequency, thus allowing the wind power plant to be operated at constant Volt/Hz. In this paper, a constant Volt/Hz operation applied to the Type 1 wind turbine generator. Various control aspects of Type 1 generators at the plant level and at the turbine level will be investigated.

Gevorgian, V.; Singh, M.; Muljadi, E.

2011-12-01T23:59:59.000Z

185

The Minimum Wind Speed for Sustainable Turbulence in the Nocturnal Boundary Layer  

Science Conference Proceedings (OSTI)

The collapse of turbulence in the nocturnal boundary layer is studied by means of a simple bulk model that describes the basic physical interactions in the surface energy balance. It is shown that for a given mechanical forcing, the amount of ...

B. J. H. Van de Wiel; A. F. Moene; H. J. J. Jonker; P. Baas; S. Basu; J. M. M. Donda; J. Sun; A. A. M. Holtslag

2012-11-01T23:59:59.000Z

186

Eddy Heat Flux in the Southern Ocean: Response to Variable Wind Forcing  

Science Conference Proceedings (OSTI)

The authors assess the role of time-dependent eddy variability in the Antarctic Circumpolar Current (ACC) in influencing warming of the Southern Ocean. For this, an eddy-resolving quasigeostrophic model of the wind-driven circulation is used, and ...

Andrew Mc C. Hogg; Michael P. Meredith; Jeffrey R. Blundell; Chris Wilson

2008-02-01T23:59:59.000Z

187

On the Structure of Variability of the Observed Tropospheric and Stratospheric Zonal-Mean Zonal Wind  

Science Conference Proceedings (OSTI)

The latitude-height structure of variability of the monthly-mean zonally-averaged zonal wind (?) is objectively documented for the 9-year period (1980–88) during which both ECMWF and NMC global analyses are available. Modes, resulting from a ...

Sumant Nigam

1990-07-01T23:59:59.000Z

188

Wind Variability—An Indicator for a Mesoclimatic Change in Israel  

Science Conference Proceedings (OSTI)

It is shown that the normalized diurnal and interdiurnal surface wind variabilities have a clear decreasing trend in central-southern Israel for the last three decades. This trend is found in the surface data of the independent time series of ...

Pinhas Alpert; Moshe Mandel

1986-11-01T23:59:59.000Z

189

Abstract--The variability and non-dispatchable nature of wind and solar energy production presents  

E-Print Network (OSTI)

storage (for over several hours or for a day) are generally pumped hydro or compressed air energy storage1 Abstract--The variability and non-dispatchable nature of wind and solar energy production, energy storage can be a viable solution to balance energy production against its consumption. This paper

190

Model of variable speed constant frequency double fed wind power generation system and analysis of its operating performance  

Science Conference Proceedings (OSTI)

Structure of variable speed constant frequency double fed wind power generation system (WPGS) was analyzed, and its model was established. Maximum power point tracking (MPPT) control, constant power control and vector control for WPGS were discussed. ... Keywords: operating performance, variable speed constant frequency, vector control, wind power generation system

Pan Tinglong; Ji Zhicheng

2009-06-01T23:59:59.000Z

191

Wind Direction Dependence of Atmospheric Boundary Layer Turbulence Parameters in the Urban Roughness Sublayer  

Science Conference Proceedings (OSTI)

A variety of atmospheric boundary layer parameters are examined as a function of wind direction in both urban and suburban settings in Oklahoma City, Oklahoma, derived from measurements during the Joint Urban 2003 field campaign. Heterogeneous ...

Cheryl Klipp

2007-12-01T23:59:59.000Z

192

Turbulence Spectra and Dissipation Rates in a Wind Tunnel Model of the Atmospheric Convective Boundary Layer  

Science Conference Proceedings (OSTI)

A model of the atmospheric convective boundary layer (CBL) is realized in the thermally stratified wind tunnel of the Institute of Hydrology and Water Resources, University of Karlsruhe. Further experimental results from this model are presented. ...

Rolf Kaiser; Evgeni Fedorovich

1998-02-01T23:59:59.000Z

193

Variable speed operation of generators with rotor-speed feedback in wind power applications  

SciTech Connect

The use of induction generators in wind power applications has been common since the early development of the wind industry. Most of these generators operate at fixed frequency and are connected directly to the utility grid. Unfortunately, this mode of operation limits the rotor speed to a specific rpm. Variable-speed operation is preferred in order to facilitate maximum energy capture over a wide range of wind speeds. This paper explores variable-speed operating strategies for wind turbine applications. The objectives are to maximize energy production, provide controlled start-up and reduce torque loading. This paper focuses on optimizing the energy captured by operating at maximum aerodynamic efficiency at any wind speed. The control strategy we analyze uses rotor speed and generator power as the feedback signals. In the normal operating region, rotor speed is used to compute a target power that corresponds to optimum operation. With power as the control objective, the power converter and generator are controlled to track the target power at any rpm. Thus, the torque-speed characteristic of the generator is shaped to optimize the energy capture. The target power is continuously updated at any rpm. in extreme areas of the operating envelope, during start-up, shutdown, generator overload, or overspeed, different strategies driven by other system considerations must be used.

Muljadi, E.; Butterfield, C.P.; Migliore, P.

1995-11-01T23:59:59.000Z

194

Perpendicular Ion Heating by Low-Frequency Alfven-Wave Turbulence in the Solar Wind  

E-Print Network (OSTI)

We consider ion heating by turbulent Alfven waves (AWs) and kinetic Alfven waves (KAWs) with perpendicular wavelengths comparable to the ion gyroradius and frequencies smaller than the ion cyclotron frequency. When the turbulence amplitude exceeds a certain threshold, an ion's orbit becomes chaotic. The ion then interacts stochastically with the time-varying electrostatic potential, and the ion's energy undergoes a random walk. Using phenomenological arguments, we derive an analytic expression for the rates at which different ion species are heated, which we test by simulating test particles interacting with a spectrum of randomly phased AWs and KAWs. We find that the stochastic heating rate depends sensitively on the quantity epsilon = dv/vperp, where vperp is the component of the ion velocity perpendicular to the background magnetic field B0, and dv (dB) is the rms amplitude of the velocity (magnetic-field) fluctuations at the gyroradius scale. In the case of thermal protons, when epsilon eps1, the proton ...

Chandran, Benjamin D G; Rogers, Barrett N; Quataert, Eliot; Germaschewski, Kai

2010-01-01T23:59:59.000Z

195

Modelling the asymmetric wind of the luminous blue variable binary MWC 314  

E-Print Network (OSTI)

We present a spectroscopic analysis of MWC 314, a luminous blue variable (LBV) candidate with an extended bipolar nebula. The detailed spectroscopic variability is investigated to determine if MWC 314 is a massive binary system with a supersonically accelerating wind or a low-mass B[e] star. We compare the spectrum and spectral energy distribution to other LBVs (such as P Cyg) and find very similar physical wind properties, indicating strong kinship. We combined long-term high-resolution optical spectroscopic monitoring and V-band photometric observations to determine the orbital elements and stellar parameters and to investigate the spectral variability with the orbital phases. We developed an advanced model of the large-scale wind-velocity and wind-density structure with 3-D radiative transfer calculations that fit the orbitally modulated P Cyg profile of He I lam5876, showing outflow velocities above 1000 km/s. We find that MWC 314 is a massive semi-detached binary system of ~1.22 AU, observed at an inclin...

Lobel, A; Martayan, C; Frémat, Y; Dozinel, K Torres; Raskin, G; Van Winckel, H; Prins, S; Pessemier, W; Waelkens, C; Hensberge, H; Dummortier, L; Jorissen, A; Van Eck, S; Lehmann, H

2013-01-01T23:59:59.000Z

196

The effects of variable speed and drive train component efficiencies on wind turbine energy capture  

SciTech Connect

A wind turbine rotor achieves optimal aerodynamic efficiency at a single tip-speed ratio (TSR). To maintain that optimal TSR and maximize energy capture in the stochastic wind environment, it is necessary to employ variable-speed operation. Conventional constant-speed wind turbines have, in the past, been converted into variable-speed turbines by attaching power electronics to the conventional induction generator and gearbox drive train. Such turbines have shown marginal, if any, improvement in energy capture over their constant-speed counterparts. These discrepancies have been shown to be the result of drive train components that are not optimized for variable-speed operation. Traditional drive trains and power electronic converters are designed to achieve maximum efficiency at full load and speed. However, the main energy producing winds operate the turbine at light load for long periods of time. Because of this, significant losses to efficiency occur. This investigation employs a quasi-static model to demonstrate the dramatic effect that component efficiency curves can have on overall annual energy capture.

Fingersh, L.J.; Robinson, M.C.

1998-05-01T23:59:59.000Z

197

Proton, Electron, and Ion Heating in the Fast Solar Wind from Nonlinear Coupling Between Alfvenic and Fast-Mode Turbulence  

E-Print Network (OSTI)

In the parts of the solar corona and solar wind that experience the fewest Coulomb collisions, the component proton, electron, and heavy ion populations are not in thermal equilibrium with one another. Observed differences in temperatures, outflow speeds, and velocity distribution anisotropies are useful constraints on proposed explanations for how the plasma is heated and accelerated. This paper presents new predictions of the rates of collisionless heating for each particle species, in which the energy input is assumed to come from magnetohydrodynamic (MHD) turbulence. We first created an empirical description of the radial evolution of Alfven, fast-mode, and slow-mode MHD waves. This model provides the total wave power in each mode as a function of distance along an expanding flux tube in the high-speed solar wind. Next we solved a set of cascade advection-diffusion equations that give the time-steady wavenumber spectra at each distance. An approximate term for nonlinear coupling between the Alfven and fas...

Cranmer, Steven R

2012-01-01T23:59:59.000Z

198

Analysis of CASES-99 Lidar and Turbulence Data in Support of Wind Turbine Effects: April 1, 2001 to Januay 31, 2003  

DOE Green Energy (OSTI)

The nocturnal low-level jet (LLJ) of the Great Plains of the central United States has been identified as a promising source of high-momentum wind flow for wind energy. The acceleration of the winds after sunset above the surface produces a jet profile in the wind velocity, with maximum speeds that often exceed 10 m s-1 or more at heights near 100 m or more. These high wind speeds are advantageous for wind energy generation. The high speeds aloft, however, also produce a region of high shear between the LLJ and the earth's surface, where the nocturnal flow is often calm or nearly so. This shear zone below the LLJ generates atmospheric waves and turbulence that can cause strong vibration in the turbine rotors. It has been suggested that these vibrations contribute to premature failures in large wind turbines, which, of course, would be a considerable disadvantage for wind energy applications. In October 1999, a field project called the Cooperative Atmosphere-Surface Exchange Study 1999 campaign, or CASES-99, was conducted in southeastern Kansas to study the nocturnal stable boundary layer. One of the instruments deployed during CASES-99 was the High-Resolution Doppler Lidar, a new scanning, remote-sensing, wind-mapping instrument.

Banta, R. M.

2003-06-01T23:59:59.000Z

199

Great Plains Turbulence Environment: Its Origins, Impact, and Simulation  

SciTech Connect

This paper summarizes the known impacts of nocturnal turbulence on wind turbine performance and operations.

Kelley, N. D.; Jonkman, B. J.; Scott, G. N.

2006-12-01T23:59:59.000Z

200

A Bulk Turbulent Air–Sea Flux Algorithm for High-Wind, Spray Conditions  

Science Conference Proceedings (OSTI)

Sensible and latent heat can cross the air–sea interface by two routes: as interfacial fluxes controlled by molecular processes right at the interface, and as spray fluxes from the surface of sea spray droplets. Once the 10-m wind speed over the ...

Edgar L. Andreas; P. Ola G. Persson; Jeffrey E. Hare

2008-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Wind Levelized Cost of Energy: A Comparison of Technical and Financing Input Variables  

NLE Websites -- All DOE Office Websites (Extended Search)

1 1 October 2009 Wind Levelized Cost of Energy: A Comparison of Technical and Financing Input Variables Karlynn Cory and Paul Schwabe National Renewable Energy Laboratory 1617 Cole Boulevard, Golden, Colorado 80401-3393 303-275-3000 * www.nrel.gov NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Operated by the Alliance for Sustainable Energy, LLC Contract No. DE-AC36-08-GO28308 Technical Report NREL/TP-6A2-46671 October 2009 Wind Levelized Cost of Energy: A Comparison of Technical and Financing Input Variables Karlynn Cory and Paul Schwabe Prepared under Task No. WER9.3550 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government.

202

PROTON, ELECTRON, AND ION HEATING IN THE FAST SOLAR WIND FROM NONLINEAR COUPLING BETWEEN ALFVENIC AND FAST-MODE TURBULENCE  

Science Conference Proceedings (OSTI)

In the parts of the solar corona and solar wind that experience the fewest Coulomb collisions, the component proton, electron, and heavy ion populations are not in thermal equilibrium with one another. Observed differences in temperatures, outflow speeds, and velocity distribution anisotropies are useful constraints on proposed explanations for how the plasma is heated and accelerated. This paper presents new predictions of the rates of collisionless heating for each particle species, in which the energy input is assumed to come from magnetohydrodynamic (MHD) turbulence. We first created an empirical description of the radial evolution of Alfven, fast-mode, and slow-mode MHD waves. This model provides the total wave power in each mode as a function of distance along an expanding flux tube in the high-speed solar wind. Next, we solved a set of cascade advection-diffusion equations that give the time-steady wavenumber spectra at each distance. An approximate term for nonlinear coupling between the Alfven and fast-mode fluctuations is included. For reasonable choices of the parameters, our model contains enough energy transfer from the fast mode to the Alfven mode to excite the high-frequency ion cyclotron resonance. This resonance is efficient at heating protons and other ions in the direction perpendicular to the background magnetic field, and our model predicts heating rates for these species that agree well with both spectroscopic and in situ measurements. Nonetheless, the high-frequency waves comprise only a small part of the total Alfvenic fluctuation spectrum, which remains highly two dimensional as is observed in interplanetary space.

Cranmer, Steven R.; Van Ballegooijen, Adriaan A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2012-08-01T23:59:59.000Z

203

Dynamical Response of the Oceanic Circulation and Temperature to Interdecadal Variability in the Surface Winds over the Indian Ocean  

Science Conference Proceedings (OSTI)

A global ocean general circulation model (OGCM) is used to investigate the sensitivity of the circulation and temperature fields to observed interdecadal variability in Indian Ocean winds for the austral summer (January, February, March). Focus ...

C. J. C. Reason; R. J. Allan; J. A. Lindesay

1996-01-01T23:59:59.000Z

204

Nonlinear Dual-Mode Control of Variable-Speed Wind Turbines with Doubly Fed Induction Generators  

E-Print Network (OSTI)

This paper presents a feedback/feedforward nonlinear controller for variable-speed wind turbines with doubly fed induction generators. By appropriately adjusting the rotor voltages and the blade pitch angle, the controller simultaneously enables: (a) control of the active power in both the maximum power tracking and power regulation modes, (b) seamless switching between the two modes, and (c) control of the reactive power so that a desirable power factor is maintained. Unlike many existing designs, the controller is developed based on original, nonlinear, electromechanically-coupled models of wind turbines, without attempting approximate linearization. Its development consists of three steps: (i) employ feedback linearization to exactly cancel some of the nonlinearities and perform arbitrary pole placement, (ii) design a speed controller that makes the rotor angular velocity track a desired reference whenever possible, and (iii) introduce a Lyapunov-like function and present a gradient-based approach for mini...

Tang, Choon Yik; Jiang, John N

2010-01-01T23:59:59.000Z

205

Distrubance Tracking and Blade Load Control of Wind Turbines in Variable-Speed Operation: Preprint  

DOE Green Energy (OSTI)

A composite state-space controller was developed for a multi-objective problem in the variable-speed operation of wind turbines. Disturbance Tracking Control theory was applied to the design of a torque controller to optimize energy capture under the influence of persistent wind disturbances. A limitation in the theory for common multi-state models is described, which led to the design of a complementary pitch controller. The goal of the independent blade pitch design was to minimize blade root fatigue loads. Simulation results indicate an 11% reduction in fatigue damage using the proposed controllers, compared to a conventional torque-only design. Meanwhile, energy capture is almost identical, partly because of nonlinear effects.

Stol, K. A.

2003-01-01T23:59:59.000Z

206

The effects of energy storage properties and forecast accuracy on mitigating variability in wind power generation  

E-Print Network (OSTI)

Electricity generation from wind power is increasing worldwide. Wind power can offset traditional fossil fuel generators which is beneficial to the environment. However, wind generation is unpredictable. Wind speeds have ...

Jaworsky, Christina A

2013-01-01T23:59:59.000Z

207

Impacts of Spatial and Temporal Windspeed Variability on Wind Energy Output  

Science Conference Proceedings (OSTI)

Modern applications of wind energy include water pumping and, for supply of electricity, grid-connected wind turbines and wind/direct stand-alone systems. In Britain, wind energy has been found to be particularly suited to isolated communities ...

J. P. Palutikof; P. M. Kelly; T. D. Davies; J. A. Halliday

1987-09-01T23:59:59.000Z

208

Turbulence Regimes and Turbulence Intermittency in the Stable Boundary Layer during CASES-99  

Science Conference Proceedings (OSTI)

An investigation of nocturnal intermittent turbulence during the Cooperative Atmosphere–Surface Exchange Study in 1999 (CASES-99) revealed three turbulence regimes at each observation height: 1) regime 1, a weak turbulence regime when the wind ...

Jielun Sun; Larry Mahrt; Robert M. Banta; Yelena L. Pichugina

2012-01-01T23:59:59.000Z

209

Turbulent Velocity-Variance Profiles in the Stable Boundary Layer Generated by a Nocturnal Low-Level Jet  

Science Conference Proceedings (OSTI)

Profiles of mean winds and turbulence were measured by the High Resolution Doppler lidar in the strong-wind stable boundary layer (SBL) with continuous turbulence. The turbulence quantity measured was the variance of the streamwise wind velocity ...

Robert M. Banta; Yelena L. Pichugina; W. Alan Brewer

2006-11-01T23:59:59.000Z

210

Novel sensorless generator control and grid fault ride-through strategies for variable-speed wind turbines and implementation on a new real-time simulation platform.  

E-Print Network (OSTI)

??The usage of MW-size variable-speed wind turbines as sources of energy has increased significantly during the last decade. Advantages over fixed-speed wind turbines include more… (more)

Yang, Sheng

2010-01-01T23:59:59.000Z

211

Variability of the Winter Wind Waves and Swell in the North Atlantic and North Pacific as Revealed by the Voluntary Observing Ship Data  

Science Conference Proceedings (OSTI)

This paper analyses secular changes and interannual variability in the wind wave, swell, and significant wave height (SWH) characteristics over the North Atlantic and North Pacific on the basis of wind wave climatology derived from the visual ...

Sergey K. Gulev; Vika Grigorieva

2006-11-01T23:59:59.000Z

212

Wind Power Variability, Its Cost, and Effect on Power Plant Emissions  

E-Print Network (OSTI)

no additional emissions. Pairing multiple turbines with a wind plant achieves ~77 to 95% of the emissions.4 DATA 9 2.5 METHODS 13 2.5.1 INTERCONNECTING WIND PLANTS 13 2.5.2 MISSING DATA 14 2.5.3 SCALING WIND. .................................................................................... 32 FIGURE 2-11 ­ NORMALIZED PREDICTED ANNUAL WIND ENERGY PRODUCTION FROM 16 WIND TURBINES LOCATED

213

Neuroadaptive speed assistance control of wind turbine with variable ratio gearbox (VRG)  

Science Conference Proceedings (OSTI)

Wind power as a renewable energy source is irregular in occurrence. It is interesting yet challenging to maximize the energy capture from wind. Most existing control methods for wind power generation are traditionally based on wind turbine with fixed ... Keywords: PMSM, neuroadaptive control, speed regulation, wind turbine

Xue-fei Wang; Yong-duan Song; Dan-yong Li; Kai Zhang; Shan Xue; Ming Qin

2012-07-01T23:59:59.000Z

214

Examining the Variability of Wind Power Output in the Regulation Time Frame: Preprint  

DOE Green Energy (OSTI)

This work examines the distribution of changes in wind power for different time scales in the regulation time frame as well as the correlation of changes in power output for individual wind turbines in a wind plant.

Hodge, B. M.; Shedd, S.; Florita, A.

2012-08-01T23:59:59.000Z

215

Development and Validation of WECC Variable Speed Wind Turbine Dynamic Models for Grid Integration Studies  

DOE Green Energy (OSTI)

This paper describes reduced-order, simplified wind turbine models for analyzing the stability impact of large arrays of wind turbines with a single point of network interconnection.

Behnke, M.; Ellis, A.; Kazachkov, Y.; McCoy, T.; Muljadi, E.; Price, W.; Sanchez-Gasca, J.

2007-09-01T23:59:59.000Z

216

Radiosonde measurements of turbulence  

NLE Websites -- All DOE Office Websites (Extended Search)

at Cranwell, Lincolnshire, W. H. Pick and G. A. Bull, 1926. 3 Talk structure * Geomagnetic sensors to measure orientation * Orientation variability as a turbulence measure *...

217

Atmospheric Stability Impacts on Power Curves of Tall Wind Turbines - An Analysis of a West Coast North American Wind Farm  

SciTech Connect

Tall wind turbines, with hub heights at 80 m or above, can extract large amounts of energy from the atmosphere because they are likely to encounter higher wind speeds, but they face challenges given the complex nature of wind flow and turbulence at these heights in the boundary layer. Depending on whether the boundary layer is stable, neutral, or convective, the mean wind speed, direction, and turbulence properties may vary greatly across the tall turbine swept area (40 to 120 m AGL). This variability can cause tall turbines to produce difference amounts of power during time periods with identical hub height wind speeds. Using meteorological and power generation data from a West Coast North American wind farm over a one-year period, our study synthesizes standard wind park observations, such as wind speed from turbine nacelles and sparse meteorological tower observations, with high-resolution profiles of wind speed and turbulence from a remote sensing platform, to quantify the impact of atmospheric stability on power output. We first compare approaches to defining atmospheric stability. The standard, limited, wind farm operations enable the calculation only of a wind shear exponent ({alpha}) or turbulence intensity (I{sub U}) from cup anemometers, while the presence at this wind farm of a SODAR enables the direct observation of turbulent kinetic energy (TKE) throughout the turbine rotor disk. Additionally, a nearby research meteorological station provided observations of the Obukhov length, L, a direct measure of atmospheric stability. In general, the stability parameters {alpha}, I{sub U}, and TKE are in high agreement with the more physically-robust L, with TKE exhibiting the best agreement with L. Using these metrics, data periods are segregated by stability class to investigate power performance dependencies. Power output at this wind farm is highly correlated with atmospheric stability during the spring and summer months, while atmospheric stability exerts little impact on power output during the winter and autumn periods. During the spring and summer seasons, power output for a given wind speed was significantly higher during stable conditions and significantly lower during strongly convective conditions: power output differences approached 20% between stable and convective regimes. The dependency of stability on power output was apparent only when both turbulence and the shape of the wind speed profile were considered. Turbulence is one of the mechanisms by which atmospheric stability affects a turbine's power curve at this particular site, and measurements of turbulence can yield actionable insights into wind turbine behavior.

Wharton, S; Lundquist, J K

2010-02-22T23:59:59.000Z

218

Atmospheric Stability Impacts on Power Curves of Tall Wind Turbines - An Analysis of a West Coast North American Wind Farm  

SciTech Connect

Tall wind turbines, with hub heights at 80 m or above, can extract large amounts of energy from the atmosphere because they are likely to encounter higher wind speeds, but they face challenges given the complex nature of wind flow and turbulence at these heights in the boundary layer. Depending on whether the boundary layer is stable, neutral, or convective, the mean wind speed, direction, and turbulence properties may vary greatly across the tall turbine swept area (40 to 120 m AGL). This variability can cause tall turbines to produce difference amounts of power during time periods with identical hub height wind speeds. Using meteorological and power generation data from a West Coast North American wind farm over a one-year period, our study synthesizes standard wind park observations, such as wind speed from turbine nacelles and sparse meteorological tower observations, with high-resolution profiles of wind speed and turbulence from a remote sensing platform, to quantify the impact of atmospheric stability on power output. We first compare approaches to defining atmospheric stability. The standard, limited, wind farm operations enable the calculation only of a wind shear exponent ({alpha}) or turbulence intensity (I{sub U}) from cup anemometers, while the presence at this wind farm of a SODAR enables the direct observation of turbulent kinetic energy (TKE) throughout the turbine rotor disk. Additionally, a nearby research meteorological station provided observations of the Obukhov length, L, a direct measure of atmospheric stability. In general, the stability parameters {alpha}, I{sub U}, and TKE are in high agreement with the more physically-robust L, with TKE exhibiting the best agreement with L. Using these metrics, data periods are segregated by stability class to investigate power performance dependencies. Power output at this wind farm is highly correlated with atmospheric stability during the spring and summer months, while atmospheric stability exerts little impact on power output during the winter and autumn periods. During the spring and summer seasons, power output for a given wind speed was significantly higher during stable conditions and significantly lower during strongly convective conditions: power output differences approached 20% between stable and convective regimes. The dependency of stability on power output was apparent only when both turbulence and the shape of the wind speed profile were considered. Turbulence is one of the mechanisms by which atmospheric stability affects a turbine's power curve at this particular site, and measurements of turbulence can yield actionable insights into wind turbine behavior.

Wharton, S; Lundquist, J K

2010-02-22T23:59:59.000Z

219

Testing requirements for variable-speed generating technology for wind turbine applications. Final report  

Science Conference Proceedings (OSTI)

Guidelines for evaluating the impacts of integrating variable-speed, constant-frequency (VSCF) wind turbines into electric utility systems have been proposed based upon prior test experiences with the NASA VSCF system and the expected performance of the Westinghouse and OMNION VSCF systems. The NASA and Westinghouse VSCF generating systems use a wound rotor induction generator and a cycloconverter, while the OMNION system uses a wound rotor induction generator and a dc-current link converter. The design of VSCF/utility system interface requirements and test plans is based on utility system electrical issues such as utility system control and operation, protection, voltage/reactive power management, power quality, and reliability. A framework for testing VSCF concepts is proposed which includes a three stage process: modeling of the system to analyze design alternatives and simulate disturbances that could be harmful to the actual system; laboratory testing which involves the use of the system under controlled conditions; and field testing to collect data under actual conditions to validate models and analyze the wind turbine behavior.

Herrera, J.I.

1986-05-01T23:59:59.000Z

220

Systematic approach for PID controller design for pitch-regulated, variable-speed wind turbines  

DOE Green Energy (OSTI)

Variable-speed, horizontal axis wind turbines use blade-pitch control to meet specified objectives for three regions of operation. This paper focuses on controller design for the constant power production regime. A simple, rigid, non-linear turbine model was used to systematically perform trade-off studies between two performance metrics. Minimization of both the deviation of the rotor speed from the desired speed and the motion of the actuator is desired. The robust nature of the proportional-integral-derivative (PID) controller is illustrated, and optimal operating conditions are determined. Because numerous simulation runs may be completed in a short time, the relationship of the two opposing metrics is easily visualized. 2 refs., 9 figs.

Hand, M.M. [National Renewable Energy Lab., Golden, CO (United States); Balas, M.J. [Univ. of Colorado, Boulder, CO (United States). Dept. of Aerospace Engineering Sciences

1997-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Analysis of the electrical harmonic characteristics of a slip recovery variable speed generating system for wind turbine applications  

SciTech Connect

Variable speed electric generating technology can enhance the general use of wind energy in electric utility applications. This enhancement results from two characteristic properties of variable speed wind turbine generators: an improvement in drive train damping characteristics, which results in reduced structural loading on the entire wind turbine system, and an improvement in the overall efficiency by using a more sophisticated electrical generator. Electronic converter systems are the focus of this investigation -- in particular, the properties of a wound-rotor induction generator with the slip recovery system and direct-current link converter. Experience with solid-state converter systems in large wind turbines is extremely limited. This report presents measurements of electrical performances of the slip recovery system and is limited to the terminal characteristics of the system. Variable speed generating systems working effectively in utility applications will require a satisfactory interface between the turbine/generator pair and the utility network. The electrical testing described herein focuses largely on the interface characteristics of the generating system. A MOD-O wind turbine was connected to a very strong system; thus, the voltage distortion was low and the total harmonic distortion in the utility voltage was less than 3% (within the 5% limit required by most utilities). The largest voltage component of a frequency below 60 Hz was 40 dB down from the 60-Hz< component. 8 refs., 14 figs., 8 tabs.

Herrera, J.I.; Reddoch, T.W.

1988-02-01T23:59:59.000Z

222

Pitch Angle Control of Variable Low Rated Speed Wind Turbine Using Fuzzy Logic Control  

E-Print Network (OSTI)

Abstract — Pitch angle control of wind turbine has been used widely to reduce torque and output power variation in high rated wind speed areas. It is a challenge to maximize available energy in the low rated wind speed areas. In this paper, a wind turbine prototype with a pitch angle control based on fuzzy logic to maximize the output power is built and demonstrated. In the varying low rated wind speed of 4-6 m/s, the use of fuzzy logic controller can maximize the average output power of 14.5 watt compared to 14.0 watt at a fixed pitch angle of the blade. Implementation of pitch angle fuzzy logic-based control to the wind turbine is suitable for the low rated wind speed areas. Index Terms — low rated wind speed areas, pitch angle control, fuzzy logic, wind turbine. T I.

A. Musyafa; A. Harika; I. M. Y. Negara; I. Rob

2010-01-01T23:59:59.000Z

223

Free and Forced Variability of the Tropical Atlantic Ocean: Role of the Wind–Evaporation–Sea Surface Temperature Feedback  

Science Conference Proceedings (OSTI)

The role of the wind–evaporation–sea surface temperature (WES) feedback in the low-frequency natural variability of the tropical Atlantic is studied using an atmospheric global climate model—the NCAR Community Climate Model, version 3 (CCM3)—...

Salil Mahajan; R. Saravanan; Ping Chang

2010-11-01T23:59:59.000Z

224

Fluctuating wind power penetration as limited by frequency standard.  

E-Print Network (OSTI)

??Fluctuating wind power is due to wind turbulence and is the part which should be filtered out leaving behind the more predictable mean wind power… (more)

Luo, Changling, 1980-

2005-01-01T23:59:59.000Z

225

Vertical Wind Variability Observed by VHF Radar in the Lee of the Colorado Rockies  

Science Conference Proceedings (OSTI)

During March 1981 the Sunset and Platteville VHF clear-air radars located in Colorado to the east of the continental divide observed vertical winds continuously over a three-week period. The vertical winds at these locations contain fluctuations ...

W. L. Ecklund; K. S. Gage; B. B. Balsley; R. G. Strauch; J. L. Green

1982-10-01T23:59:59.000Z

226

The study of multimode power control system for MW variable-speed wind turbine  

Science Conference Proceedings (OSTI)

Wind energy is a viable option to complement other types of pollution-free generation. In the past constant-speed wind turbine is used for the limitation of the control technology and manufacturing technology. But this kind wind turbine has low efficiency ... Keywords: feed-forward compensator, loop-shaping, multimode power control system, pitch controller, speed controller, the shaft system model, wind turbine

Dingguo Wu; Zhixin Wang

2008-10-01T23:59:59.000Z

227

Analysis of Variability and Uncertainty in Wind Power Forecasting: An International Comparison (Presentation)  

Science Conference Proceedings (OSTI)

This presentation summarizes the work to investigate the uncertainty in wind forecasting at different times of year and compare wind forecast errors in different power systems using large-scale wind power prediction data from six countries: the United States, Finland, Spain, Denmark, Norway, and Germany.

Zhang, J.; Hodge, B.; Miettinen, J.; Holttinen, H.; Gomez-Lozaro, E.; Cutululis, N.; Litong-Palima, M.; Sorensen, P.; Lovholm, A.; Berge, E.; Dobschinski, J.

2013-10-01T23:59:59.000Z

228

Revealing the Impact of Climate Variability on the Wind Resource Using Data Mining Techniques (Poster)  

DOE Green Energy (OSTI)

A data mining technique called 'k-means clustering' can be used to group winds at the NWTC into 4 major clusters. The frequency of some winds in the clusters is correlated with regional pressure gradients and climate indices. The technique could also be applied to wind resource assessment and selecting scenarios for flow modeling.

Clifton, A.; Lundquist, J.

2011-12-01T23:59:59.000Z

229

Effects of Atmospheric Turbulence on Ballistic Testing  

Science Conference Proceedings (OSTI)

The effects of atmospheric turbulence on munition target scatter are determined from numerical simulations of ballistic trajectories through many realizations of realistic simulated turbulent wind fields. A technique is evaluated for correcting ...

Rod Frehlich; Robert Sharman; Charles Clough; Michael Padovani; Kelly Fling; Ward Boughers; W. Scott Walton

2008-05-01T23:59:59.000Z

230

Climatic Variability of Near-Surface Turbulent Kinetic Energy over the United States: Implications for Fire-Weather Predictions  

Science Conference Proceedings (OSTI)

Recent research suggests that high levels of ambient near-surface atmospheric turbulence are often associated with rapid and sometimes erratic wildland fire spread that may eventually lead to large burn areas. Previous research has also examined ...

Warren E. Heilman; Xindi Bian

2013-04-01T23:59:59.000Z

231

turbulence | OpenEI  

Open Energy Info (EERE)

turbulence turbulence Dataset Summary Description This raw data reflects readings from instruments mounted on or near a 82 meter meteorological tower located at the National Wind Technology Center (NWTC), approximately 5 miles south of Boulder, CO (specifically: 39.9107 N, 105.2348 W, datum WGS84). Source NREL Date Released Unknown Date Updated Unknown Keywords DOE irradiance NREL NWTC temperature turbulence wind wind direction wind speed Data text/plain icon Raw data (txt, 82 KiB) application/vnd.openxmlformats-officedocument.spreadsheetml.sheet icon Raw data field descriptions (xlsx, 52.5 KiB) Quality Metrics Level of Review Some Review Comment Data have not been reviewed for accuracy or completeness; disclaimer available (http://www.nrel.gov/disclaimer.html). Temporal and Spatial Coverage

232

Quasi-Periodic Releases of Streamer Blobs and Velocity Variability of the Slow Solar Wind near the Sun  

E-Print Network (OSTI)

We search for persistent and quasi-periodic release events of streamer blobs during 2007 with the Large Angle Spectrometric Coronagraph on the \\textit{Solar and Heliospheric Observatory} and assess the velocity of the slow solar wind along the plasma sheet above the corresponding streamer by measuring the dynamic parameters of blobs. We find 10 quasi-periodic release events of streamer blobs lasting for three to four days. In each day of these events, we observe three-five blobs. The results are in line with previous studies using data observed near the last solar minimum. Using the measured blob velocity as a proxy for that of the mean flow, we suggest that the velocity of the background slow solar wind near the Sun can vary significantly within a few hours. This provides an observational manifestation of the large velocity variability of the slow solar wind near the Sun.

Song, H Q; Liu, K; Feng, S W; Xia, L D

2009-01-01T23:59:59.000Z

233

Variable accretion and emission from the stellar winds in the Galactic centre  

E-Print Network (OSTI)

We present numerical simulations of stellar wind dynamics in the central parsec of the Galactic centre, studying in particular the accretion of gas on to Sgr A*, the super-massive black hole. Unlike our previous work, here we use state-of-the-art observational data on orbits and wind properties of individual wind-producing stars. Since wind velocities were revised upwards and non-zero eccentricities were considered, our new simulations show fewer clumps of cold gas and no conspicuous disc-like structure. The accretion rate is dominated by a few close `slow wind stars' v_w Integral observations, but we argue that the accretion of a cold clump with a small impact parameter could have caused it. Finally, we show the possibility of constraining the total mass-loss rate of the `slow wind stars' using near infra-red observations of gas in the central few arcseconds.

Jorge Cuadra; Sergei Nayakshin; Fabrice Martins

2007-05-05T23:59:59.000Z

234

Wind Tunnel Study of Turbulent Flow Structure in the Convective Boundary Layer Capped by a Temperature Inversion  

Science Conference Proceedings (OSTI)

Experiments on simulating the atmospheric convective boundary layer (CBL), capped by a temperature inversion and affected by surface shear, were carried out in the thermally stratified wind tunnel of the Institute of Hydrology and Water Resources,...

Evgeni Fedorovich; Rolf Kaiser; Matthias Rau; Erich Plate

1996-05-01T23:59:59.000Z

235

The evaluation of a turbulent loads characterization system  

DOE Green Energy (OSTI)

In this paper we discuss an on-line turbulent load characterization system that has been designed to acquire loading spectra from turbines of the same design operating in several different environments and from different turbine designs operating in the same environment. This System simultaneously measures the rainflow-counted alternating and mean loading spectra and the hub-height turbulent mean shearing stress and atmospheric stability associated with the turbulent inflow. We discuss the theory behind the measurement configuration and the results of proof-of-concept testing recently performed at the National Wind Technology Center (NWTC) using a Bergey EXCEL-S 10-kW wind turbine. The on-line approach to characterizing the load spectra and the inflow turbulent scaling parameter produces results that are consistent with other measurements. The on-line approximation of the turbulent shear stress or friction velocity u* also is considered adequate. The system can be used to characterize turbulence loads during turbine deployment in a wide variety of environments. Using the WISPER protocol, we found that a wide-range, variable-speed turbine will accumulate a larger number of stress cycles in the low-cycle, high-amplitude (LCHA) region when compared with a constant speed rotor under similar inflow conditions.

Kelley, N.D.; McKenna, H.E. [National Renewable Energy Lab., Golden, CO (United States)

1996-01-01T23:59:59.000Z

236

Enhancement of Wind-Driven Upwelling and Downwelling by Alongshore Bathymetric Variability  

Science Conference Proceedings (OSTI)

Steady wind-driven flow along a shelf of changing width is described with a frictional barotropic model valid in the limit of small Rossby and Burger number. In these limits, an alongshore wind drives enhanced onshelf transport in a coastal ocean ...

James M. Pringle

2002-11-01T23:59:59.000Z

237

Control algorithms for effective operation of variable-speed wind turbines  

DOE Green Energy (OSTI)

This report describes a computer code, called ASYM and provides results from its application in simulating the control of the 34-m Test Bed vertical-axis wind turbine (VAWT) in Bushland, Texas. The code synthesizes dynamic wind speeds on a second-by-second basis in the time domain. The wind speeds conform to a predetermined spectral content governed by the hourly average wind speed that prevails at each hour of the simulation. The hourly average values are selected in a probabilistic sense through the application of Markov chains, but their cumulative frequency of occurrence conforms to a Rayleigh distribution that is governed by the mean annual wind speed of the site selected. The simulated wind speeds then drive a series of control algorithms that enable the code to predict key operational parameters such as number of annual starts and stops, annual energy production, and annual fatigue damage at a critically stressed joint on the wind turbine. This report also presents results from the application of ASYM that pertain to low wind speed cut-in and cut-out conditions and controlled operation near critical speed ranges that excite structural vibrations that can lead to accelerated fatigue damage.

Not Available

1993-10-01T23:59:59.000Z

238

Low Wind Speed Technology Phase II: Investigation of the Application of Medium-Voltage Variable-Speed Drive Technology to Improve the Cost of Energy from Low Wind Speed Turbines; Behnke, Erdman and Whitaker Engineering, Inc.  

SciTech Connect

This fact sheet describes a subcontract with Behnke, Erdman & Whitaker Engineering, Inc. to test the feasibility of applying medium-voltage variable-speed drive technology to low wind speed turbines.

2006-03-01T23:59:59.000Z

239

Comparison on control strategies of the grid-side converter of variable speed constant frequency doubly-fed wind power generation system  

Science Conference Proceedings (OSTI)

Direct power control, vector control based on d-q synchronous rotating reference frame and ?-? static reference frame for the grid-side converter of variable speed constant frequency doubly-fed wind turbines are analyzed. System simulation ... Keywords: ?-? static reference frame, d-q rotating reference frame, direct power control, doubly-fed wind power generation system, grid-side converter

Xian-Ming Zhou; Ting-Long Pan; Zhi-Cheng Ji

2009-06-01T23:59:59.000Z

240

On the Loss of Wind-Induced Near-Inertial Energy to Turbulent Mixing in the Upper Ocean  

Science Conference Proceedings (OSTI)

Wind-induced near-inertial energy has been believed to be an important source for generating the ocean mixing required to maintain the global meridional overturning circulation. In the present study, the near-inertial energy budget in a realistic ...

Xiaoming Zhai; Richard J. Greatbatch; Carsten Eden; Toshiyuki Hibiya

2009-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Provisionally Corrected Surface Wind Data, Worldwide Ocean-Atmosphere Surface Fields, and Sahellan Rainfall Variability  

Science Conference Proceedings (OSTI)

Worldwide ship datasets of sea surface temperature (SST), sea level pressure (SLP), and surface vector wind are analyzed for a July-September composite of five Sabelian wet years (1950, 1952, 1953, 1954, 1958) minus five Sahelian dry years (1972, ...

M. Neil Ward

1992-05-01T23:59:59.000Z

242

Modeling the Wind-Driven Variability of the South Indian Ocean  

Science Conference Proceedings (OSTI)

This article describes the results of numerical experiments carried out with a general circulation ocean model to investigate the effect of the seasonal cycle of the wind forcing on the Agulhas transport. Two cases are described. The first was ...

R. P. Matano; C. G. Simionato; P. T. Strub

1999-02-01T23:59:59.000Z

243

Wind-driven sea level variability on the California coast: an adjoint sensitivity analysis  

Science Conference Proceedings (OSTI)

Effects of atmospheric forcing on coastal sea surface height near Port San Luis, central California, are investigated using a regional state estimate and its adjoint. The physical pathways for the propagation of non-local ((100) km) wind stress ...

Ariane Verdy; Matthew R. Mazloff; Bruce D. Cornuelle; Sung Yong Kim

244

Control of wind turbine output power via a variable rotor resistance.  

E-Print Network (OSTI)

??Many utility-scale wind turbine generators use wound-rotor induction machines. By adding an external rotor resistance to the rotor circuit it is possible to control the… (more)

Burnham, David James

2009-01-01T23:59:59.000Z

245

Structure of SST and Surface Wind Variability during Indian Ocean Dipole Mode Events: COADS Observations  

Science Conference Proceedings (OSTI)

A study of the detailed spatiotemporal characteristics of the Indian Ocean dipole (IOD) mode in SST and surface winds using available observations from 1958 till 1997 is reported. The analysis is used to address several of the controversial ...

N. H. Saji; T. Yamagata

2003-08-01T23:59:59.000Z

246

Wind-Forced Sea Level Variability Along the West Florida Shelf (Winter, 1978)  

Science Conference Proceedings (OSTI)

Coastal tide gage and meteorological records from Pensacola to Key West for the period January–April 1978 have been examined for low-frequency fluctuations. The dominant 6-day period signals in sea level, alongshore wind stress, and atmospheric ...

G. O. Marmorino

1982-05-01T23:59:59.000Z

247

Modeling of Trade Wind Cumuli with a Low-Order Turbulence Model: Toward a Unified Description of Cu and Se Clouds in Meteorological Models  

Science Conference Proceedings (OSTI)

A simple method is proposed to extend a low-order turbulence scheme including a subgrid-scale cloudiness scheme to represent not only nonconvective (stratiform) cloudiness and turbulence but also shallow, nonprecipitating cumulus convection by ...

P. Bechtold; J. W. M. Cuijpers; P. Mascart; P. Trouilhet

1995-02-01T23:59:59.000Z

248

Evaporation-Wind Feedback and Low-Frequency Variability in the Tropical Atmosphere  

Science Conference Proceedings (OSTI)

A mechanism by which feedback between zonal wind perturbations and evaporation can create unstable, low-frequency modes in a simple two-layer model of the tropical troposphere is presented. The modes resemble the 30–50 day oscillation. A series ...

J. David Neelin; Isaac M. Held; Kerry H. Cook

1987-08-01T23:59:59.000Z

249

Individual Pitch Control for Mitigation of Power Fluctuation of Variable Speed Wind Turbines  

E-Print Network (OSTI)

, China mcheng@seu.edu.cn Abstract-- Grid connected wind turbines are the sources of power fluctuations and the individual pitch controller is designed. The simulations are performed on the NREL (National Renewable Energy shortage, great efforts have been taken around the world to implement renewable energy projects

Chen, Zhe

250

A Global View on the Wind Sea and Swell Climate and Variability from ERA-40  

Science Conference Proceedings (OSTI)

In this paper a detailed global climatology of wind-sea and swell parameters, based on the 45-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40) wave reanalysis is presented. The spatial pattern of the swell dominance of ...

Alvaro Semedo; Kay Sušelj; Anna Rutgersson; Andreas Sterl

2011-03-01T23:59:59.000Z

251

Transition to Aperiodic Variability in a Wind-Driven Double-Gyre Circulation Model  

Science Conference Proceedings (OSTI)

Multiple equilibria as well as periodic and aperiodic solution regimes are obtained in a barotropic model of the midlatitude ocean’s double-gyre circulation. The model circulation is driven by a steady zonal wind profile that is symmetric with ...

Kyung-Il Chang; Michael Ghil; Kayo Ide; Chung-Chieng Aaron Lai

2001-05-01T23:59:59.000Z

252

Controlling hour-long power of wind farms.  

E-Print Network (OSTI)

??In attempting to control the power output of a wind farm, it is first necessary to smooth the power fluctuations due to wind turbulence. This… (more)

Li, Pei, 1981-

2007-01-01T23:59:59.000Z

253

Optimization of the Regional Spatial Distribution of Wind Power Plants to Minimize the Variability of Wind Energy Input into Power Supply Systems  

Science Conference Proceedings (OSTI)

In contrast to conventional power generation, wind energy is not a controllable resource because of its stochastic nature, and the cumulative energy input of several wind power plants into the electric grid may cause undesired fluctuations in the ...

Federico Cassola; Massimiliano Burlando; Marta Antonelli; Corrado F. Ratto

2008-12-01T23:59:59.000Z

254

Analysis of a teetered, variable-speed rotor: final report  

DOE Green Energy (OSTI)

A computer model of a horizontal axis wind turbine (HOOT) with four structural degrees of freedom has been derived and verified. The four degrees of freedom include flapwise motion of the blades, teeter motion, and variable rotor speed. Options for the variable rotor speed include synchronous, induction, and constant-tip speed generator models with either start, stop, or normal operations. Verification is made by comparison with analytical solutions and mean and cyclic ESI-80 data. The Veers full-field turbulence model is used as a wind input for a synchronous and induction generator test case during normal operation. As a result of the comparison, it is concluded that the computer model can be used to predict accurately mean and cyclic loads with a turbulent wind input. 47 refs., 19 figs.

Weber, T.L.; Wilson, R.E.; Walker, S.N. (Oregon State Univ., Corvallis, OR (USA). Dept. of Mechanical Engineering) [Oregon State Univ., Corvallis, OR (USA). Dept. of Mechanical Engineering

1991-06-01T23:59:59.000Z

255

Use of Solar and Wind as a Physical Hedge against Price Variability within a Generation Portfolio  

DOE Green Energy (OSTI)

This study provides a framework to explore the potential use and incremental value of small- to large-scale penetration of solar and wind technologies as a physical hedge against the risk and uncertainty of electricity cost on multi-year to multi-decade timescales. Earlier studies characterizing the impacts of adding renewable energy (RE) to portfolios of electricity generators often used a levelized cost of energy or simplified net cash flow approach. In this study, we expand on previous work by demonstrating the use of an 8760 hourly production cost model (PLEXOS) to analyze the incremental impact of solar and wind penetration under a wide range of penetration scenarios for a region in the Western U.S. We do not attempt to 'optimize' the portfolio in any of these cases. Rather we consider different RE penetration scenarios, that might for example result from the implementation of a Renewable Portfolio Standard (RPS) to explore the dynamics, risk mitigation characteristics and incremental value that RE might add to the system. We also compare the use of RE to alternative mechanisms, such as the use of financial or physical supply contracts to mitigate risk and uncertainty, including consideration of their effectiveness and availability over a variety of timeframes.

Jenkin, T.; Diakov, V.; Drury, E.; Bush, B.; Denholm, P.; Milford, J.; Arent, D.; Margolis, R.; Byrne, R.

2013-08-01T23:59:59.000Z

256

Modeling and Analysis of the Wind-Waves Field Variability in the Indian Ocean During 1998-2009 Years  

E-Print Network (OSTI)

To calculate the wind-waves in the Indian Ocean (IO), the wind field for the period from 1998 to 2009 was used, obtained from the NCEP/NOAA archive, and numerical model WAM (Cycle-4) was applied, modified by the new source function proposed in Polnikov (2005). Based on buoy data for the Indian Ocean, the fitting of the modified model WAM was done, which provides the win in accuracy of calculations on 35%, in comparison with the original model. All the further calculations of the wave fields in IO were made for these model settings. At the first stage, the analysis of the simulation results involves a) mapping the fields of the significant wave height and the wave energy , calculated with different scales of averaging in time T and space R; b) estimating the fields of seasonal, annual and long-term variability; and c) determining the 12-year trend of the annually averaged fields. The analysis was carried out taking into account the previously introduced zoning the ocean area, provided by the spatial inhomogen...

Polnikov, V G; Sannasiraj, S A; Sundar, V

2011-01-01T23:59:59.000Z

257

Wind-Driven Thermocline Variability in the Pacific: A Model–Data Comparison  

Science Conference Proceedings (OSTI)

The spatial and temporal patterns of interannual temperature variability within the main thermocline (200–400-m depth) of the Pacific (30°S–60°N) during 1968–97 are documented in two observational datasets and an ocean general circulation model ...

Jo Ann Lysne; Clara Deser

2002-04-01T23:59:59.000Z

258

On the Fluid Dynamical Theory of Turbulent Gas Transfer Across an Air-Sea Interface in the Presence of Breaking Wind-Waves  

Science Conference Proceedings (OSTI)

It is shown that in order to describe the transfer of gases in the liquid near the air-sea interface, the vertical structure of three-dimensional small-scale turbulence in turbulent patches generated by breaking waves must be considered. The ...

S. A. Kitaigorodskii

1984-05-01T23:59:59.000Z

259

Low-Frequency Variability, Coherence Resonance, and Phase Selection in a Low-Order Model of the Wind-Driven Ocean Circulation  

Science Conference Proceedings (OSTI)

In this paper, a low-order spectral quasigeostrophic (QG) model of the wind-driven ocean circulation is derived and used to analyze the low-order character of the intrinsic low-frequency variability of the midlatitude double-gyre ocean circulation ...

Stefano Pierini

2011-09-01T23:59:59.000Z

260

Turbulence Kinetic Energy Budget Profiles Derived from Doppler Sodar Measurements  

Science Conference Proceedings (OSTI)

Doppler sodar wind measurements made in light wind conditions in September 1979 near a power plant in Turbigo, Italy, are used to derive terms in the turbulence kinetic energy (TKE) budget. Measurements on five days are grouped into two classes: ...

Gary K. Greenhut; Giangiuseppe Mastrantonio

1989-02-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Investigation of Flow, Turbulence, and Dispersion within Built Environments  

E-Print Network (OSTI)

Properties of the wind field within the Oklahoma City ParkProperties of the wind field within the Oklahoma City Parkwinds, turbulence, and dispersion in built-up downtown areas of Oklahoma

Pan, Hansheng

2011-01-01T23:59:59.000Z

262

Large Scale, Low Frequency Variability of the 1979 FGGE Surface Buoy Drifts and Winds over the Southern Hemisphere  

Science Conference Proceedings (OSTI)

The surface response of the Southern Hemisphere's oceans to the large spatial scale, interseasonal changes in wind forcing during the FGGE year of 1979 is investigated. The primary data are the analyzed daily wind fields, and the trajectories of ...

W. G. Large; H. Van Loon

1989-02-01T23:59:59.000Z

263

Prediction of extinction and reignition in nonpremixed turbulent flames using a flamelet/progress variable model. 2. Application in LES of Sandia flames D and E  

SciTech Connect

An extension of the flamelet/progress variable (FPV) model for the prediction of extinction and reignition is applied in large-eddy simulation (LES) of flames D and E of the Sandia piloted turbulent jet flame series. This model employs a presumed probability density function (PDF), in which the marginal PDF of a reactive scalar is modeled by a statistically most likely distribution. This provides two advantages. First of all, the shape of the distribution depends on chemical and mixing time-scale information, and second, an arbitrary number of moments can be enforced. This model was analyzed in an a priori study in the first part of this work. In the present LES application, the first two moments of mixture fraction and reaction progress variable are used to constrain the shape of the presumed PDF. Transport equations for these quantities are solved, and models for the residual scalar dissipation rates, which appear as unclosed terms in the equations for the scalar variances, are provided. Statistical flow field quantities for axial velocity, mixture fraction, and temperature, obtained from the extended FPV model, are in good agreement with experimental data. Mixture-fraction-conditioned data, conditional PDFs, and burning indices are computed and compared with the delta-function flamelet closure model, which employs a Dirac distribution as a model for the marginal PDF of the reaction progress parameter. The latter model considerably underpredicts the amount of local extinction, which shows that the consideration of second-moment information in the presumed PDF of the reaction progress parameter is important for the accurate prediction of extinction and reignition. Mixture-fraction-conditioned results obtained from the extended FPV model are in good agreement with experimental data; however, the overprediction of the consumption of fuel and oxidizer on the fuel-rich side results in an overprediction of minor species. The predictions for the conditional PDFs and burning indices are in good agreement with measurements. (author)

Ihme, Matthias; Pitsch, Heinz [Department of Mechanical Engineering, Stanford University, Stanford, CA 94305 (United States)

2008-10-15T23:59:59.000Z

264

Mesoscale Influences of Wind Farms throughout a Diurnal Cycle  

Science Conference Proceedings (OSTI)

Large wind farms are expected to influence local and regional atmospheric circulations. Using a mesoscale parameterization of the effects of wind farms that includes a momentum sink and a wind speed–dependent source of turbulent kinetic energy, ...

Anna C. Fitch; Julie K. Lundquist; Joseph B. Olson

2013-07-01T23:59:59.000Z

265

Example of Reduced Turbulence during Thunderstorm Outflow  

Science Conference Proceedings (OSTI)

The vertical structures of turbulence, winds, and temperatures are analyzed from a 92-m instrumented tower and a collocated acoustic sodar during an outflow episode from a weak thunderstorm over sloping terrain in northern New Mexico. Prior to ...

Brent M. Bowen

1996-06-01T23:59:59.000Z

266

Wind characteristics for agricultural wind energy applications  

SciTech Connect

Wind energy utilization in agriculture can provide a potentially significant savings in fuel oil consumption and ultimately a cost savings to the farmer. A knowledge of the wind characteristics within a region and at a location can contribute greatly to a more efficient and cost-effective use of this resource. Current research indicates that the important wind characteristics include mean annual wind speed and the frequency distribution of the wind, seasonal and diurnal variations in wind speed and direction, and the turbulent and gustiness characteristics of the wind. Further research is underway to provide a better definition of the total wind resource available, improved methods for siting WECS and an improved understanding of the environment to which the WECS respond.

Renne, D. S.

1979-01-01T23:59:59.000Z

267

Crop Wind Energy Experiment (CWEX): Observations of Surface-Layer, Boundary Layer, and Mesoscale Interactions with a Wind Farm  

Science Conference Proceedings (OSTI)

Perturbations of mean and turbulent wind characteristics by large wind turbines modify fluxes between the vegetated surface and the lower boundary layer. While simulations have suggested that wind farms could significantly change surface fluxes of heat, ...

Daniel A. Rajewski; Eugene S. Takle; Julie K. Lundquist; Steven Oncley; John H. Prueger; Thomas W. Horst; Michael E. Rhodes; Richard Pfeiffer; Jerry L. Hatfield; Kristopher K. Spoth; Russell K. Doorenbos

2013-05-01T23:59:59.000Z

268

The Turbulence Structure of Nocturnal Slope Flow  

Science Conference Proceedings (OSTI)

Measurements of the turbulence structure of nocturnal slope flow are used to test the hypothesis that slope flow turbulence in the region above the low-level wind maximum is decoupled from the surface and has a local structure similar to that ...

T. W. Horst; J. C. Doran

1988-02-01T23:59:59.000Z

269

Low Wind Speed Turbine Project Phase II: The Application of Medium-Voltage Electrical Apparatus to the Class of Variable Speed Multi-Megawatt Low Wind Speed Turbines; 15 June 2004--30 April 2005  

DOE Green Energy (OSTI)

Kilowatt ratings of modern wind turbines have progressed rapidly from 50 kW to 1,800 kW over the past 25 years, with 3.0- to 7.5-MW turbines expected in the next 5 years. The premise of this study is simple: The rapid growth of wind turbine power ratings and the corresponding growth in turbine electrical generation systems and associated controls are quickly making low-voltage (LV) electrical design approaches cost-ineffective. This report provides design detail and compares the cost of energy (COE) between commercial LV-class wind power machines and emerging medium-voltage (MV)-class multi-megawatt wind technology. The key finding is that a 2.5% reduction in the COE can be achieved by moving from LV to MV systems. This is a conservative estimate, with a 3% to 3.5% reduction believed to be attainable once purchase orders to support a 250-turbine/year production level are placed. This evaluation considers capital costs as well as installation, maintenance, and training requirements for wind turbine maintenance personnel. Subsystems investigated include the generator, pendant cables, variable-speed converter, and padmount transformer with switchgear. Both current-source and voltage-source converter/inverter MV topologies are compared against their low-voltage, voltage-source counterparts at the 3.0-, 5.0-, and 7.5-MW levels.

Erdman, W.; Behnke, M.

2005-11-01T23:59:59.000Z

270

WIND DATA REPORT Gardner NCCI  

E-Print Network (OSTI)

/RERL_Fact_Sheet_6_Wind_resource_interpretation.pdf * 1 m/s = 2.237 mph. SECTION 1 January 30, 2008 Renewable Energy, and wind roses are included in APPENDIX B. January 30, 2008 Renewable Energy Research Laboratory Page 8 ­ Turbulent Intensity vs. Wind Speed, March 1, 2007 ­ May 31, 2007 January 30, 2008 Renewable Energy Research

Massachusetts at Amherst, University of

271

Improving the reliability of wind power through spatially distributed wind generation.  

E-Print Network (OSTI)

??Wind power is a fast-growing, sustainable energy source. However, the problem of wind variability as it relates to wind power reliability is an obstacle to… (more)

Fisher, Samuel Martin

2012-01-01T23:59:59.000Z

272

Comparison of Wind Profiler and Aircraft Wind Measurements at Chebogue Point, Nova Scotia  

Science Conference Proceedings (OSTI)

In August 1993, a 915-MHz boundary layer wind-profiling radar was deployed at Chebogue Point, Nova Scotia, to provide wind, turbulence, and boundary layer structure information for the North Atlantic Regional Experiment summer 1993 intensive ...

Wayne M. Angevine; J. Ian Macpherson

1995-04-01T23:59:59.000Z

273

Emergence of Jets from Turbulence in the Shallow-Water Equations on an Equatorial Beta Plane  

Science Conference Proceedings (OSTI)

Coherent jets, such as the Jovian banded winds, are a prominent feature of rotating turbulence. Shallow-water turbulence models capture the essential mechanism of jet formation, which is systematic eddy momentum flux directed up the mean velocity ...

Brian F. Farrell; Petros J. Ioannou

2009-10-01T23:59:59.000Z

274

Numerical Simulation of ANATEX Tracer Data Using a Turbulence Closure Model for Long-Range Dispersion  

Science Conference Proceedings (OSTI)

A long-range transport model based on turbulence closure concepts is described. The model extends the description of planetary boundary layer turbulent diffusion to the larger scales and uses statistical wind information to predict contaminant ...

R. I. Sykes; S. F. Parker; D. S. Henn; W. S. Lewellen

1993-05-01T23:59:59.000Z

275

Turbulence Structure of the Hurricane Boundary Layer between the Outer Rainbands  

Science Conference Proceedings (OSTI)

As part of the Coupled Boundary Layers Air–Sea Transfer (CBLAST)-Hurricane program, flights were conducted to directly measure turbulent fluxes and turbulence properties in the high-wind boundary layer of hurricanes between the outer rainbands. ...

Jun A. Zhang; William M. Drennan; Peter G. Black; Jeffrey R. French

2009-08-01T23:59:59.000Z

276

Calculation of Surface Fluxes under Convective Conditions by Turbulence Closure Models  

Science Conference Proceedings (OSTI)

A method of deriving new relationships between near-surface turbulent fluxes and vertical differences of wind speed and potential temperature between two levels in the atmospheric surface layer from simplified second-order turbulence closure ...

Lech ?obocki

2001-03-01T23:59:59.000Z

277

NREL: Learning - Wind Energy Basics: How Wind Turbines Work  

NLE Websites -- All DOE Office Websites (Extended Search)

Wind Energy Basics: How Wind Turbines Work Wind Energy Basics: How Wind Turbines Work We have been harnessing the wind's energy for hundreds of years. From old Holland to farms in the United States, windmills have been used for pumping water or grinding grain. Today, the windmill's modern equivalent-a wind turbine-can use the wind's energy to generate electricity. Wind turbines, like windmills, are mounted on a tower to capture the most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and less turbulent wind. Turbines catch the wind's energy with their propeller-like blades. Usually, two or three blades are mounted on a shaft to form a rotor. A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure

278

Variability of the Outer Wind Profiles of Western North Pacific Typhoons: Classifications and Techniques for Analysis and Forecasting  

Science Conference Proceedings (OSTI)

The hazard posed by tropical cyclones (TCs) is often quantified in terms of the minimum central pressure (MCP) or maximum wind speed. While significant, these qualities must be balanced against considerations for the strength and spatial extent ...

Stephen B. Cocks; William M. Gray

2002-08-01T23:59:59.000Z

279

LIDAR Wind Speed Measurements of Evolving Wind Fields  

DOE Green Energy (OSTI)

Light Detection and Ranging (LIDAR) systems are able to measure the speed of incoming wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feedforward control systems designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurately the incoming wind field can be measured. Past studies have assumed Taylor's frozen turbulence hypothesis, which implies that turbulence remains unchanged as it advects downwind at the mean wind speed. With Taylor's hypothesis applied, the only source of wind speed measurement error is distortion caused by the LIDAR. This study introduces wind evolution, characterized by the longitudinal coherence of the wind, to LIDAR measurement simulations to create a more realistic measurement model. A simple model of wind evolution is applied to a frozen wind field used in previous studies to investigate the effects of varying the intensity of wind evolution. LIDAR measurements are also evaluated with a large eddy simulation of a stable boundary layer provided by the National Center for Atmospheric Research. Simulation results show the combined effects of LIDAR errors and wind evolution for realistic turbine-mounted LIDAR measurement scenarios.

Simley, E.; Pao, L. Y.

2012-07-01T23:59:59.000Z

280

LIDAR Wind Speed Measurements of Evolving Wind Fields  

SciTech Connect

Light Detection and Ranging (LIDAR) systems are able to measure the speed of incoming wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feedforward control systems designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurately the incoming wind field can be measured. Past studies have assumed Taylor's frozen turbulence hypothesis, which implies that turbulence remains unchanged as it advects downwind at the mean wind speed. With Taylor's hypothesis applied, the only source of wind speed measurement error is distortion caused by the LIDAR. This study introduces wind evolution, characterized by the longitudinal coherence of the wind, to LIDAR measurement simulations to create a more realistic measurement model. A simple model of wind evolution is applied to a frozen wind field used in previous studies to investigate the effects of varying the intensity of wind evolution. LIDAR measurements are also evaluated with a large eddy simulation of a stable boundary layer provided by the National Center for Atmospheric Research. Simulation results show the combined effects of LIDAR errors and wind evolution for realistic turbine-mounted LIDAR measurement scenarios.

Simley, E.; Pao, L. Y.

2012-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Wind Energy Assessment Study for Nevada -- Tall Tower Deployment (Stone Cabin): 26 June 2005 - 31 December 2007  

DOE Green Energy (OSTI)

The objective of this work effort was to characterize wind shear and turbulence for representative wind-developable areas in Nevada.

Koracin, D.; Reinhardt, R.; McCurdy, G.; Liddle, M.; McCord, T.; Vellore, R.; Minor, T.; Lyles, B.; Miller, D.; Ronchetti, L.

2009-12-01T23:59:59.000Z

282

Velcro Measurement of Turbulence Kinetic Energy Dissipation Rate ?  

Science Conference Proceedings (OSTI)

Turbulence in the ocean results from many different processes operating over a wide range of space scales and timescales, with spatial and temporal variability particularly extreme in coastal oceans. If the origins and effects of turbulent ...

Ann E. Gargett

1999-12-01T23:59:59.000Z

283

Boils and Turbulence in a Weakly Stratified Shallow Tidal Sea  

Science Conference Proceedings (OSTI)

Measurements of turbulence are made in a weakly but variably stratified region of tidal straining in the eastern Irish Sea using turbulence sensors profiling vertically through the water column on the Fast Light Yo-yo (FLY) profiler and ...

S. A. Thorpe; J. A. M. Green; J. H. Simpson; T. R. Osborn; W. A. M. Nimmo Smith

2008-08-01T23:59:59.000Z

284

RESEARCH ARTICLE Dynamic wind loads and wake characteristics of a wind turbine  

E-Print Network (OSTI)

RESEARCH ARTICLE Dynamic wind loads and wake characteristics of a wind turbine model of the unsteady vortex and turbulent flow structures in the near wake of a horizontal axis wind turbine model.e., aerodynamic forces and bending moments) acting on the wind turbine model by using a high-sensitive force

Hu, Hui

285

Geographical Variations of the Influence of Low-Frequency Variability on Lower-Tropospheric Extreme Westerly Wind Events  

Science Conference Proceedings (OSTI)

A conceptual framework is developed for quantifying the relationship between low-frequency variability and extreme events. In this framework, variability is decomposed into low-frequency and synoptic components using complementary 10-day low-pass ...

Jeffrey H. Yin; Grant W. Branstator

2008-09-01T23:59:59.000Z

286

Towns across Massachusetts are considering wind power, not only because it is one of the cleanest,  

E-Print Network (OSTI)

of energy captured from the wind and electricity produced. The quality of a wind site depends on may things of the wind and create turbulence. Turbulence reduces the amount of energy that can be captured and can Power: Siting in Communities Wind Power on the Community Scale Renewable Energy Research Laboratory

Massachusetts at Amherst, University of

287

A comparison of measured wind park load histories with the WISPER and WISPERX load spectra  

DOE Green Energy (OSTI)

The blade-loading histories from two adjacent Micon 65/13 wind turbines are compared with the variable-amplitude test-loading histories known as the WISPER and WISPERX spectra. These standardized loading sequences were developed from blade flapwise load histories taken from nine different horizontal-axis wind turbines operating under a wide range of conditions in Europe. The subject turbines covered a broad spectrum of rotor diameters, materials, and operating environments. The final loading sequences were developed as a joint effort of thirteen different European organizations. The goal was to develop a meaningful loading standard for horizontal-axis wind turbine blades that represents common interaction effects seen in service. In 1990, NREL made extensive load measurements on two adjacent Micon 65/13 wind turbines in simultaneous operation in the very turbulent environment of a large wind park. Further, before and during the collection of the loads data, comprehensive measurements of the statistics of the turbulent environment were obtained at both the turbines under test and at two other locations within the park. The trend to larger but lighter wind turbine structures has made an understanding of the expected lifetime loading history of paramount importance. Experience in the US has shown that the turbulence-induced loads associated with multi-row wind parks in general are much more severe than for turbines operating individually or within widely spaced environments. Multi-row wind parks are much more common in the US than in Europe. In this paper we report on our results in applying the methodology utilized to develop the WISPER and WISPERX standardized loading sequences using the available data from the Micon turbines. While the intended purpose of the WISPER sequences were not to represent a specific operating environment, we believe the exercise is useful, especially when a turbine design is likely to be installed in a multi-row wind park.

Kelley, N.D.

1995-01-01T23:59:59.000Z

288

NREL Develops Simulations for Wind Plant Power and Turbine Loads...  

NLE Websites -- All DOE Office Websites (Extended Search)

loading due to wake turbulence. The current state of knowledge concerning wind turbine wakes and how they interact with other turbines and the atmospheric boundary layer is...

289

3D Simulation of a 5MW Wind Turbine.  

E-Print Network (OSTI)

??In the present work, the influence of turbulence and gravity forces on the tower and the rotor of a 5MW onshore wind turbine has been… (more)

Namiranian, Abtin

2011-01-01T23:59:59.000Z

290

Managing Wind Power Forecast Uncertainty in Electric Grids.  

E-Print Network (OSTI)

??Electricity generated from wind power is both variable and uncertain. Wind forecasts provide valuable information for wind farm management, but they are not perfect. Chapter… (more)

Mauch, Brandon Keith

2012-01-01T23:59:59.000Z

291

Transilient Turbulence Theory. Part II: Turbulent Adjustment  

Science Conference Proceedings (OSTI)

Turbulent adjustment is a scheme where dynamic instabilities in the flow are eliminated by turbulence. It is a form of first-order turbulence closure that is applicable to numerical forecast models of the atmosphere. The responsive form of ...

Roland B. Stull; Takehiko Hasegawa

1984-12-01T23:59:59.000Z

292

An Objective Clear-Air Turbulence Forecasting Technique: Verification and Operational Use  

Science Conference Proceedings (OSTI)

An objective technique for forecasting clear-air turbulence (CAT) is described. An index is calculated based on the product of horizontal deformation and vertical wind shear derived from numerical model forecast winds aloft. The forecast ...

Gary P. Ellrod; David I. Knapp

1992-03-01T23:59:59.000Z

293

The InterHourly-Variability (IHV) Index of Geomagnetic Activity and its Use in Deriving the Long-term Variation of Solar Wind Speed  

E-Print Network (OSTI)

We describe the derivation of the InterHourly Variability (IHV) index of geomagnetic activity. The IHV-index for a geomagnetic element is mechanically derived from hourly values as the sum of the unsigned differences between adjacent hours over a seven-hour interval centered on local midnight. The index is derived separately for stations in both hemispheres within six longitude sectors using only local night hours. It is intended as a long-term index. Available data allows derivation of the index back well into the 19th century. On a time scale of a 27-day Bartels rotation, IHV averages for stations with corrected geomagnetic latitude less than 55 degrees are strongly correlated with midlatitude range indices. Assuming a constant calibration of the aa-index we find that observed yearly values of aa before the year 1957 are 2.9 nT too small compared to values calculated from IHV using the regression constants based on 1980-2004. We interpret this discrepancy as an indication that the calibration of the aa index is in error before 1957. There is no such problem with the ap index. Rotation averages of IHV are also strongly correlated with solar wind parameters (BV^2). On a time scale of a year combining the IHV-index and the recently-developed Inter-Diurnal Variability (IDV) index (giving B) allows determination of solar wind speed, V, from 1890-present. Over the ~120-year series, the yearly mean solar wind speed varied from a low of 303 km/s in 1902 to a high value of 545 km/s in 2003. The calculated yearly values of the product BV using B and V separately derived from IDV and IHV agree quantitatively with (completely independent) BV derived from the amplitude of the diurnal variation of the H component in the polar caps since 1926 and sporadically beyond.

Leif Svalgaard; Edward W. Cliver

2007-06-07T23:59:59.000Z

294

IEEE TRANSACTIONS ON ENERGY CONVERSION, VOL. 23, NO. 2, JUNE 2008 551 Sliding Mode Power Control of Variable-Speed Wind  

E-Print Network (OSTI)

based on the wind farm single phase equivalent circuit. The stability analysis is carried out, phase margin, and vector gain margin calculated for different number of wind turbines in operation. The interaction between the wind turbine control system and the wind farm structure in wind farms is deeply

Paris-Sud XI, Université de

295

NREL Studies Wind Farm Aerodynamics to Improve Siting (Fact Sheet)  

DOE Green Energy (OSTI)

NREL researchers have used high-tech instruments and high-performance computing to understand atmospheric turbulence and turbine wake behavior in order to improve wind turbine design and siting within wind farms.

Not Available

2012-04-01T23:59:59.000Z

296

Comparison of Wind Monitoring Systems. Pad II: Doppley. Sodars  

Science Conference Proceedings (OSTI)

Measurements of wind speed, wind direction, and the vertical component of turbulence, from four different commercially available Doppler sodars, are compared with similar measurements from in situ sensors on a 300 m instrumented tower. Results ...

P. L. Finkelstein; J. C. Kaimal; J. E. Gaynor; M. E. Graves; T. J. Lockhart

1986-12-01T23:59:59.000Z

297

Large-Eddy Simulation of Wind-Plant Aerodynamics: Preprint  

DOE Green Energy (OSTI)

In this work, we present results of a large-eddy simulation of the 48 multi-megawatt turbines composing the Lillgrund wind plant. Turbulent inflow wind is created by performing an atmospheric boundary layer precursor simulation and turbines are modeled using a rotating, variable-speed actuator line representation. The motivation for this work is that few others have done wind plant large-eddy simulations with a substantial number of turbines, and the methods for carrying out the simulations are varied. We wish to draw upon the strengths of the existing simulations and our growing atmospheric large-eddy simulation capability to create a sound methodology for performing this type of simulation. We have used the OpenFOAM CFD toolbox to create our solver.

Churchfield, M. J.; Lee, S.; Moriarty, P. J.; Martinez, L. A.; Leonardi, S.; Vijayakumar, G.; Brasseur, J. G.

2012-01-01T23:59:59.000Z

298

LIDAR wind speed measurements of evolving wind fields  

E-Print Network (OSTI)

Light Detection and Ranging (LIDAR) systems are able to measure the speed of incoming wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feedforward control systems designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurately the incoming wind field can be measured. Past studies have assumed Taylor’s frozen turbulence hypothesis, which implies that turbulence remains unchanged as it advects downwind at the mean wind speed. With Taylor’s hypothesis applied, the only source of wind speed measurement error is distortion caused by the LIDAR. This study introduces wind evolution, characterized by the longitudinal coherence of the wind, to LIDAR measurement simulations to create a more realistic measurement model. A simple model of wind evolution is applied to a frozen wind field used in previous studies to investigate the effects of varying the intensity of wind evolution. Simulation results show the combined effects of LIDAR errors and wind evolution for realistic turbine-mounted LIDAR measurement scenarios. Nomenclature a decay parameter for exponential coherence al decrement parameter for transverse coherence (l ? {u, v, w}) bl offset parameter for transverse coherence (l ? {u, v, w}) D longitudinal distance between two points or measurement preview distance F focal distance f frequency (Hz) ? LIDAR measurement angle off of longitudinal direction k wind velocity wavenumber (m?1) ? wavelength (m) R range along LIDAR beam r scan radius for spinning LIDAR scenario ri,j distance between two points in the yz plane U mean wind speed (m/s) ?i,j average mean wind speed between two points in the yz plane ? azimuth angle in the rotor plane ?2 xy(f) Coherence between signals x and y

Eric Simley; Lucy Y. Pao; Neil Kelley; Bonnie Jonkman; Rod Frehlich

2012-01-01T23:59:59.000Z

299

WIND DATA REPORT Ragged Mt Maine  

E-Print Network (OSTI)

Energy Research Laboratory (RERL) at the University of Massachusetts, Amherst. This report covers wind Average Wind Speeds, September 1, 2007 ­ November 30, 2007. January 22, 2008 Renewable Energy Research ­ Turbulence Intensity vs. Wind Speed, September 1, 2007 ­ November 30, 2007. January 22, 2008 Renewable Energy

Massachusetts at Amherst, University of

300

Resolved turbulence characteristics in large-eddy simulations nested within mesoscale simulations using the Weather Research and Forecasting model  

Science Conference Proceedings (OSTI)

One-way concurrent nesting within the Weather Research and Forecasting (WRF) model is examined for conducting large-eddy simulations (LES) nested within mesoscale simulations. Wind speed, spectra, and resolved turbulent stresses and turbulence ...

Jeff Mirocha; Branko Kosovi?; Gokhan Kirkil

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Drag Anemometer Measurements of Turbulence over a Vegetated Surface  

Science Conference Proceedings (OSTI)

Turbulent fluctuations of vertical wind and fluxes of momentum, sensible heat and latent heat measured with a drag anemometer are compared to like data measured with other instruments. Means of the measured parameters agreed well with energy ...

T. Grayson Redford Jr.; Shashi B. Verma; Norman J. Rosenberg

1981-10-01T23:59:59.000Z

302

A Climatology of Turbulent Dispersion in the Troposphere  

Science Conference Proceedings (OSTI)

The authors present properties of turbulent, meridional mixing along isentropic surfaces within the troposphere. Twice-daily wind fields analyses from the European Centre for Medium-Range Weather Forecasts numerical weather prediction model for ...

Matthew Huber; James C. McWilliams; Michael Ghil

2001-08-01T23:59:59.000Z

303

Beyond Thermal Interaction between Ocean and Atmosphere: On the Extratropical Climate Variability due to the Wind-Induced SST  

Science Conference Proceedings (OSTI)

Prescribing sea surface temperature (SST) for the atmospheric general circulation models (GCM) may not lead to underestimation of the coupled variability. In this study, a set of SST-driven atmospheric GCM experiments, starting from slightly ...

Dong Eun Lee; Zhengyu Liu; Yun Liu

2008-05-01T23:59:59.000Z

304

Large-Eddy Simulation of Wind-Plant Aerodynamics  

DOE Green Energy (OSTI)

In this work, we present results of a large-eddy simulation of the 48 multi-megawatt turbines composing the Lillgrund wind plant. Turbulent inflow wind is created by performing an atmospheric boundary layer precursor simulation, and turbines are modeled using a rotating, variable-speed actuator line representation. The motivation for this work is that few others have done large-eddy simulations of wind plants with a substantial number of turbines, and the methods for carrying out the simulations are varied. We wish to draw upon the strengths of the existing simulations and our growing atmospheric large-eddy simulation capability to create a sound methodology for performing this type of simulation. We used the OpenFOAM CFD toolbox to create our solver. The simulated time-averaged power production of the turbines in the plant agrees well with field observations, except with the sixth turbine and beyond in each wind-aligned. The power produced by each of those turbines is overpredicted by 25-40%. A direct comparison between simulated and field data is difficult because we simulate one wind direction with a speed and turbulence intensity characteristic of Lillgrund, but the field observations were taken over a year of varying conditions. The simulation shows the significant 60-70% decrease in the performance of the turbines behind the front row in this plant that has a spacing of 4.3 rotor diameters in this direction. The overall plant efficiency is well predicted. This work shows the importance of using local grid refinement to simultaneously capture the meter-scale details of the turbine wake and the kilometer-scale turbulent atmospheric structures. Although this work illustrates the power of large-eddy simulation in producing a time-accurate solution, it required about one million processor-hours, showing the significant cost of large-eddy simulation.

Churchfield, M. J.; Lee, S.; Moriarty, P. J.; Martinez, L. A.; Leonardi, S.; Vijayakumar, G.; Brasseur, J. G.

2012-01-01T23:59:59.000Z

305

Quantifying Turbulence for Tidal Power Applications  

SciTech Connect

Using newly collected data from a tidal power site in Puget Sound, WA, metrics for turbulence quantification are assessed and discussed. The quality of raw ping Acoustic Doppler Current Profiler (ADCP) data for turbulence studies is evaluated against Acoustic Doppler Velocimeter (ADV) data at a point. Removal of Doppler noise from the raw ping data is shown to be a crucial step in turbulence quantification. Excluding periods of slack tide, the turbulent intensity estimates at a height of 4.6 m above the seabed are 8% and 11% from the ADCP and ADV, respectively. Estimates of the turbulent dissipation rate are more variable, from 10e-3 to 10e-1 W/m^3. An example analysis of coherent Turbulent Kinetic Energy (TKE) is presented.

Thomson, Jim; Richmond, Marshall C.; Polagye, Brian; Durgesh, Vibhav

2010-08-01T23:59:59.000Z

306

Wind resource assessment with a mesoscale non-hydrostatic model  

E-Print Network (OSTI)

Wind resource assessment with a mesoscale non- hydrostatic model Vincent Guénard, Center for Energy is developed for assessing the wind resource and its uncertainty. The work focuses on an existing wind farm mast measurements. The wind speed and turbulence fields are discussed. It is shown that the k

Paris-Sud XI, Université de

307

Active control for turbulent premixed flame simulations  

Science Conference Proceedings (OSTI)

Many turbulent premixed flames of practical interest are statistically stationary. They occur in combustors that have anchoring mechanisms to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. As a result, typical detailed simulations are performed in simplified model configurations such as decaying isotropic turbulence or inflowing turbulence. In these configurations, the turbulence seen by the flame either decays or, in the latter case, increases as the flame accelerates toward the turbulent inflow. This limits the duration of the eddy evolutions experienced by the flame at a given level of turbulent intensity, so that statistically valid observations cannot be made. In this paper, we apply a feedback control to computationally stabilize an otherwise unstable turbulent premixed flame in two dimensions. For the simulations, we specify turbulent in flow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm. We use the simulations to study the propagation and the local chemical variability of turbulent flame chemistry.

Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Lijewski, Michael J.

2004-03-26T23:59:59.000Z

308

Dynamic valuation model For wind development in regard to land value, proximity to transmission lines, and capacity factor  

E-Print Network (OSTI)

Developing a wind farm involves many variables that can make or break the success of a potential wind farm project. Some variables such as wind data (capacity factor, wind rose, wind speed, etc.) are readily available in ...

Nikandrou, Paul

2009-01-01T23:59:59.000Z

309

Extreme learning machine based wind speed estimation and sensorless control for wind turbine power generation system  

Science Conference Proceedings (OSTI)

This paper proposes a precise real-time wind speed estimation method and sensorless control for variable-speed variable-pitch wind turbine power generation system (WTPGS). The wind speed estimation is realized by a nonlinear input-output mapping extreme ... Keywords: Extreme learning machine, Sensorless control, Wind speed estimation, Wind turbine power generation system

Si Wu; Youyi Wang; Shijie Cheng

2013-02-01T23:59:59.000Z

310

Wind Stress and Heat Flux over the Ocean in Gale Force Winds  

Science Conference Proceedings (OSTI)

An offshore stable platform has been instrumented with wind turbulence, temperature and wave height sensors. Data from this platform have been analyzed by the eddy correlation method to obtain wind stress and heat flux at wind speeds from 6 to 22 ...

Stuart D. Smith

1980-05-01T23:59:59.000Z

311

October 11, 2011 Wind Generation  

E-Print Network (OSTI)

(CC) Power Plant #12;Wind Investors Face These Costs #12;Fixed Costs #12;Variable Costs #12;BottomESRP 285 October 11, 2011 Wind Generation · Videos · Power Point Lecture #12;Wind Videos Wind by the end of 2010 and at current rates of growth, it could double by 2014 to reach 400 GW 120 GW #12

Ford, Andrew

312

Yaglom law in the expanding solar wind  

E-Print Network (OSTI)

We study the Yaglom law, which relates the mixed third order structure function to the average dissipation rate of turbulence, in a uniformly expanding solar wind by using the two scales expansion model of magnetohydrodynamic (MHD) turbulence. We show that due to the expansion of the solar wind two new terms appear in the Yaglom law. The first term is related to the decay of the turbulent energy by nonlinear interactions, whereas the second term is related to the non-zero cross-correlation of the Els\\"asser fields. Using magnetic field and plasma data from WIND and Helios 2 spacecrafts, we show that at lower frequencies in the inertial range of MHD turbulence the new terms become comparable to Yaglom's third order mixed moment, and therefore they cannot be neglected in the evaluation of the energy cascade rate in the solar wind.

Gogoberidze, G; Carbone, V

2013-01-01T23:59:59.000Z

313

A Stochastic Model for Wind Occurrence  

Science Conference Proceedings (OSTI)

Knowledge of wind occurrence in any location is a valuable input in most agricultural studies. A bivariate stochastic process is proposed here as a model of daily wind occurrence. Two wind variables have been considered: 1) horizontal direction, ...

Jose Roldan-Cańas; Adela Garcia-Guzman; Alberto Losada-Villasante

1982-05-01T23:59:59.000Z

314

WindLogics Inc | Open Energy Information  

Open Energy Info (EERE)

Product WindLogics provides wind resource analysis and long-period variability forecasting services. References WindLogics Inc1 LinkedIn Connections CrunchBase Profile No...

315

Formation of Jets by Baroclinic Turbulence  

Science Conference Proceedings (OSTI)

Turbulent fluids are frequently observed to spontaneously self-organize into large spatial-scale jets; geophysical examples of this phenomenon include the Jovian banded winds and the earth’s polar-front jet. These relatively steady large-scale ...

Brian F. Farrell; Petros J. Ioannou

2008-11-01T23:59:59.000Z

316

Horizontal Variability in 10 m Wind Velocities as Observed at Two Prairie Sites Separated by a Distance of 7.5 km  

Science Conference Proceedings (OSTI)

It is important to assess the representativeness of mesoscale wind data because most short range pollution models assume that wind velocity will remain constant over distances in the order of 10 km. Previous observational studies have shown that ...

D. M. Leahey; M. C. Hansen; M. B. Schroeder

1989-11-01T23:59:59.000Z

317

ENERGETIC PARTICLE DIFFUSION IN STRUCTURED TURBULENCE  

Science Conference Proceedings (OSTI)

In the full-orbit particle simulations of energetic particle transport in plasmas, the plasma turbulence is typically described as a homogeneous superposition of linear Fourier modes. The turbulence evolution is, however, typically a nonlinear process, and, particularly in the heliospheric context, the solar wind plasma is inhomogeneous due to the transient structures, as observed by remote and in situ measurements. In this work, we study the effects of the inhomogeneities on energetic particle transport by using spatially distributed, superposed turbulence envelopes. We find that the cross-field transport is significantly reduced, when compared to the results obtained with homogeneous turbulence. The reduction can reach an order of magnitude when the enveloping breaks the wave phase coherence along the mean magnetic field direction.

Laitinen, T.; Dalla, S.; Kelly, J. [Jeremiah Horrocks Institute, University of Central Lancashire, PR1 2HE Preston (United Kingdom)

2012-04-20T23:59:59.000Z

318

TURBULENT FRBRNNING MVK130 Turbulent Combustion  

E-Print Network (OSTI)

TURBULENT F�RBR�NNING MVK130 Turbulent Combustion Poäng: 3.0 Betygskala: TH Valfri för: M4 to combustion, McGraw-Hill 1996. #12;

319

Rotationally sampled wind characteristics and correlations with MOD-OA wind turbine response  

SciTech Connect

This report presents results of a comprehensive wind and wind turbine measurement program: the Clayton, New Mexico, vertical plane array/MOD-OA project. In this experiment, the turbulent wind was measured for a large array of fixed anemometers located two blade diameters upwind of a 200-kW horizontal-axis wind turbine (HAWT). Simultaneously, key wind turbine response parameters were also measured. The first of two major objectives of this experiment was to determine the turbulent wind, rotationally sampled to emulate the motion of the wind turbine blade, for the range of different wind speeds and stability classes actually experienced by the wind turbine. The second major objective was to correlate this rotationally sampled wind with the wind turbine blade stress and power, in order to assess the usefulness of the wind measurements for wind turbine loads testing a prediction. Time series of rotationally sampled winds and wind turbine blade bending moments and power were converted to frequency spectra using Fourier transform techniques. These spectra were used as the basis for both qualitative and quantitative comparisons among the various cases. A quantitative comparison between the rotationally sampled wind input and blade bending response was made, using the Fourier spectra to estimate the blade transfer function. These transfer functions were then used to calculate an approximate damping coefficient for the MOD-OA fiberglass blade.

George, R.L.; Connell, J.R.

1984-09-01T23:59:59.000Z

320

Surface Wind Regionalization in Complex Terrain  

Science Conference Proceedings (OSTI)

Daily wind variability in the Comunidad Foral de Navarra in northern Spain was studied using wind observations at 35 locations to derive subregions with homogeneous temporal variability. Two different methodologies based on principal component ...

P. A. Jiménez; E. García-Bustamante; J. F. González-Rouco; F. Valero; J. P. Montávez; J. Navarro

2008-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

NREL: Wind Research - Grid Integration of Offshore Wind  

NLE Websites -- All DOE Office Websites (Extended Search)

Grid Integration of Offshore Wind Grid Integration of Offshore Wind Photograph of a wind turbine in the ocean. Located about 10 kilometers off the coast of Arklow, Ireland, the Arklow Bank offshore wind park consists of seven GE Wind 3.6-MW wind turbines. Much can be learned from the existing land-based integration research for handling the variability and uncertainty of the wind resource. Integration and Transmission One comprehensive grid integration study is the Eastern Wind Integration and Transmission Study (EWITS), in which offshore wind scenarios were analyzed. Nearly 80 GW of offshore wind was studied in the highest penetration scenario. Specific offshore grid distribution and transmission solutions were identified, including cost estimates. With the Atlantic coast likely to lead the way in offshore wind power deployment, EWITS is a benchmark for

322

Modeling wind forcing in phase resolving simulation of nonlinear wind waves  

E-Print Network (OSTI)

Wind waves in the ocean are a product of complex interaction of turbulent air flow with gravity driven water surface. The coupling is strong and the waves are non-stationary, irregular and highly nonlinear, which restricts ...

Kalmikov, Alexander G

2010-01-01T23:59:59.000Z

323

Influence of Shallow Cumuli on Subcloud Turbulence Fluxes Analyzed from Aircraft Data  

Science Conference Proceedings (OSTI)

The purpose of this study is to improve understanding of shallow cumuli in the planetary boundary layer (PBL) by quantitatively analysing subcloud turbulence variables. Aircraft turbulence data for three flights from the 1986 Hydrologic–...

Zekai Otles; John A. Young

1996-03-01T23:59:59.000Z

324

NREL: Wind Research - NREL's Wind Technology Patents Boost Efficiency and  

NLE Websites -- All DOE Office Websites (Extended Search)

NREL's Wind Technology Patents Boost Efficiency and Lower Costs NREL's Wind Technology Patents Boost Efficiency and Lower Costs March 22, 2013 Wind energy research conducted at the National Wind Technology Center (NWTC) at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) during the last decade has earned the lab two patents, one for adaptive pitch control and one for a resonance blade test system that will ultimately help its industry partners increase the efficiency of wind technologies and reduce the cost of wind energy. The most recent patent for adaptive pitch control for variable-speed wind turbines was granted in May 2012. Variable-speed wind turbines use rotor blade pitch control to regulate rotor speed at the high wind speed limit. Although manufacturers and operators have been interested in developing a nominal pitch to improve

325

Effects of Changing Atmospheric Conditions on Wind Turbine Performance (Poster)  

SciTech Connect

Multi-megawatt, utility-scale wind turbines operate in turbulent and dynamic winds that impact turbine performance in ways that are gradually becoming better understood. This poster presents a study made using a turbulent flow field simulator (TurbSim) and a Turbine aeroelastic simulator (FAST) of the response of a generic 1.5 MW wind turbine to changing inflow. The turbine power output is found to be most sensitive to wind speed and turbulence intensity, but the relationship depends on the wind speed with respect to the turbine's rated wind speed. Shear is found to be poorly correlated to power. A machine learning method called 'regression trees' is used to create a simple model of turbine performance that could be used as part of the wind resource assessment process. This study has used simple flow fields and should be extended to more complex flows, and validated with field observations.

Clifton, A.

2012-12-01T23:59:59.000Z

326

Real-Time Ocean Wind Vector Retrieval from Marine Radar Image Sequences Acquired at Grazing Angle  

Science Conference Proceedings (OSTI)

This paper proposes a novel algorithm for retrieving the ocean wind vector from marine radar image sequences in real time. It is presented as an alternative to mitigate anemometer problems, such as blockage, shadowing, and turbulence. Since wind ...

Raul Vicen-Bueno; Jochen Horstmann; Eric Terril; Tony de Paolo; Jens Dannenberg

2013-01-01T23:59:59.000Z

327

Model-Simulated Influences of Shelterbelt Shape on Wind-Sheltering Efficiency  

Science Conference Proceedings (OSTI)

The authors report results of a numerical model used to simulate wind and turbulence fields for porous, living shelterbelts with seven different cross-sectional shapes. The simulations are consistent with results of Woodruff and Zingg whose wind-...

Hao Wang; E. S. Takle

1997-06-01T23:59:59.000Z

328

Modeling of wind and radar for simulation in four-dimensional navigation environment  

E-Print Network (OSTI)

Disturbances affecting time control precision in four-dimension navigation are modeled. Several models of wind and turbulence from the ground to ten thousand feet are developed. A distinction is made between wind mean and ...

Malherbe, Gerard Andre

1976-01-01T23:59:59.000Z

329

NREL researchers are the first to use a high-performance com-puting tool for a large-eddy simulation of an entire wind plant.  

E-Print Network (OSTI)

an existing wind plant, augmenting previous studies of wind plant subsets. Wind turbines extract energy from the wind's flow, and as a byproduct they create a wake that trails behind them. If wind turbines mechanical loading due to wake turbulence.The current state of knowledge concerning wind turbine wakes

330

Linear Wind Farm Layout Optimization through Computational Intelligence  

Science Conference Proceedings (OSTI)

The optimal positioning of wind turbines, even in one dimension, is a problem with no analytical solution. This article describes the application of computational intelligence techniques to solve this problem. A systematic analysis of the optimal positioning ... Keywords: Far Wake Effects, Genetic Algorithms, Optimization, Simulated Annealing, Sitting, Turbulence and Roughness Length, Wind Farm Layout, Wind Turbines

José-Francisco Herbert-Acero; Jorge-Rodolfo Franco-Acevedo; Manuel Valenzuela-Rendón; Oliver Probst-Oleszewski

2009-11-01T23:59:59.000Z

331

WIND DATA REPORT Scituate Waste Water Treatment Plant, MA  

E-Print Network (OSTI)

Distributions Figure 3 ­ Wind Speed Distribution, March 1, 2007 ­ May 31, 2007 July 16, 2007 Renewable Energy Figure 5 ­ Diurnal Wind Speeds, March 1, 2007 ­ May 31, 2007 July 16, 2007 Renewable Energy Research ­ Turbulence Intensity vs. Wind Speed, March 1, 2007 ­ May 31, 2007 July 16, 2007 Renewable Energy Research

Massachusetts at Amherst, University of

332

Resolving Difficult Issues Of Wind Power Micrositing In Complex  

E-Print Network (OSTI)

Micrositing of wind turbines in complex terrain is tricky game, and many of the current siting methods and tools, while useful and improving, remain inadequate to the task in extreme terrain. As a consequence, there are numerous wind turbine installations that are buffeted by damaging turbulence or are faced with suboptimal wind energy performance.

Terrain Session Resource; Russell G. Derickson A; Michael Mcdiarmid B; Brad C. Cochran C; Jon A. Peterka D; Russell G. Derickson A; Michael Mcdiarmid B; Brad C. Cochran C; Jon A. Peterka D

2004-01-01T23:59:59.000Z

333

Ris-R-1239(EN) Wind Energy Department  

E-Print Network (OSTI)

Risø-R-1239(EN) Wind Energy Department: Scientific and Technical Progress 1999 - 2000 Birthe The activities of the Wind Energy Department fall within boundary layer meteorology, atmospheric turbulence-R-1239(EN) 3 Contents 1 Introduction 5 2 The Department of Wind Energy and Atmospheric Physics 5 3

334

Analysis of Wind Speed Measurements using Continuous Wave LIDAR for Wind Turbine Control ?†  

E-Print Network (OSTI)

Light Detection and Ranging (LIDAR) systems are able to measure the speed of incoming wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feedforward control systems designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurate the incoming wind field can be measured. This study examines the accuracy of different measurement scenarios that rely on coherent continuouswave Doppler LIDAR systems to determine their applicability to feedforward control. In particular, the impacts of measurement range and angular offset from the wind direction are studied for various wind conditions. A realistic case involving a scanning LIDAR unit mounted in the spinner of a wind turbine is studied in depth, with emphasis on choices for scan radius and preview distance. The effects of turbulence parameters on measurement accuracy are studied as well. Nomenclature d measurement preview distance F focal distance k wind velocity wavenumber (m?1) r scan radius for spinning LIDAR RMS root mean square ?u standard deviation of u component of wind velocity TI turbulence intensity ? LIDAR measurement angle ? mean u wind speed u ? friction velocity U ? D average friction velocity over rotor disk ? angle between laser and wind velocity vector ? angle in the rotor plane ? rotational rate of spinning LIDAR

Eric Simley; Lucy Y. Pao; Rod Frehlich; Bonnie Jonkman; Neil Kelley

2011-01-01T23:59:59.000Z

335

Simulation of winds as seen by a rotating vertical axis wind turbine blade  

DOE Green Energy (OSTI)

The objective of this report is to provide turbulent wind analyses relevant to the design and testing of Vertical Axis Wind Turbines (VAWT). A technique was developed for utilizing high-speed turbulence wind data from a line of seven anemometers at a single level to simulate the wind seen by a rotating VAWT blade. Twelve data cases, representing a range of wind speeds and stability classes, were selected from the large volume of data available from the Clayton, New Mexico, Vertical Plane Array (VPA) project. Simulations were run of the rotationally sampled wind speed relative to the earth, as well as the tangential and radial wind speeds, which are relative to the rotating wind turbine blade. Spectral analysis is used to compare and assess wind simulations from the different wind regimes, as well as from alternate wind measurement techniques. The variance in the wind speed at frequencies at or above the blade rotation rate is computed for all cases, and is used to quantitatively compare the VAWT simulations with Horizontal Axis Wind Turbine (HAWT) simulations. Qualitative comparisons are also made with direct wind measurements from a VAWT blade.

George, R.L.

1984-02-01T23:59:59.000Z

336

LIDAR Wind Speed Measurements of Evolving Wind Fields  

Science Conference Proceedings (OSTI)

Light Detection and Ranging (LIDAR) systems are able to measure the speed of incoming wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feedforward control systems that are designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurately the incoming wind field can be measured. Past studies have assumed the validity of physicist G.I. Taylor's 1938 frozen turbulence hypothesis, which implies that turbulence remains unchanged as it advects downwind at the mean wind speed. With Taylor's hypothesis applied, the only source of wind speed measurement error is distortion caused by the LIDAR. This study introduces wind evolution, characterized by the longitudinal coherence of the wind, to LIDAR measurement simulations using the National Renewable Energy Laboratory's (NREL's) 5-megawatt turbine model to create a more realistic measurement model. A simple model of wind evolution was applied to a frozen wind field that was used in previous studies to investigate the effects of varying the intensity of wind evolution. LIDAR measurements were also evaluated using a large eddy simulation (LES) of a stable boundary layer that was provided by the National Center for Atmospheric Research. The LIDAR measurement scenario investigated consists of a hub-mounted LIDAR that scans a circle of points upwind of the turbine in order to estimate the wind speed component in the mean wind direction. Different combinations of the preview distance that is located upwind of the rotor and the radius of the scan circle were analyzed. It was found that the dominant source of measurement error for short preview distances is the detection of transverse and vertical wind speeds from the line-of-sight LIDAR measurement. It was discovered in previous studies that, in the absence of wind evolution, the dominant source of error for large preview distances is the spatial averaging caused by the LIDAR's sampling volume. However, by introducing wind evolution, the dominant source of error for large preview distances was found to be the coherence loss caused by evolving turbulence. Different measurement geometries were compared using the bandwidth for which the measurement coherence remained above 0.5 and also the area under the measurement coherence curve. Results showed that, by increasing the intensity of wind evolution, the measurement coherence decreases. Using the coherence bandwidth metric, the optimal preview distance for a fixed-scan radius remained almost constant for low and moderate amounts of wind evolution. For the wind field with the simple wind evolution model introduced, the optimal preview distance for a scan radius of 75% blade span (47.25 meters) was found to be 80 meters. Using the LES wind field, the optimal preview distance was 65 meters. When comparing scan geometries using the area under the coherence curve, results showed that, as the intensity of wind evolution increases, the optimal preview distance decreases.

Simley, E.; Pao, L. Y.; Kelley, N.; Jonkman, B.; Frehlich, R.

2012-01-01T23:59:59.000Z

337

Small Wind Guidebook/What are the Basic Parts of a Small Wind...  

Open Energy Info (EERE)

the kinetic energy of the wind and converts it into rotary motion to drive the generator, which produces either AC or wild AC (variable frequency, variable voltage), which...

338

Turbulent flow in graphene  

E-Print Network (OSTI)

We demonstrate the possibility of a turbulent flow of electrons in graphene in the hydrodynamic region, by calculating the corresponding turbulent probability density function. This is used to calculate the contribution of the turbulent flow to the conductivity within a quantum Boltzmann approach. The dependence of the conductivity on the system parameters arising from the turbulent flow is very different from that due to scattering.

Kumar S. Gupta; Siddhartha Sen

2009-11-03T23:59:59.000Z

339

Extreme Winds and Wind Effects on Structures  

Science Conference Proceedings (OSTI)

Extreme Winds and Wind Effects on Structures. The Engineering ... section. I. Extreme Winds: ... II. Wind Effects on Buildings. Database ...

2013-01-17T23:59:59.000Z

340

TURBULENT FRBRNNING MVK 130 Turbulent Combustion  

E-Print Network (OSTI)

TURBULENT F�RBR�NNING MVK 130 Turbulent Combustion Antal poäng: 3.0. Valfri för: M4. Kursansvarig program med hänsyn till de modeller som används. Litteratur S.R. Turns: An introduction to combustion, Mc

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

Gyrokinetic turbulence: a nonlinear route to dissipation through phase space  

E-Print Network (OSTI)

This paper describes a conceptual framework for understanding kinetic plasma turbulence as a generalized form of energy cascade in phase space. It is emphasized that conversion of turbulent energy into thermodynamic heat is only achievable in the presence of some (however small) degree of collisionality. The smallness of the collision rate is compensated by the emergence of small-scale structure in the velocity space. For gyrokinetic turbulence, a nonlinear perpendicular phase mixing mechanism is identified and described as a turbulent cascade of entropy fluctuations simultaneously occurring at spatial scales smaller than the ion gyroscale and in velocity space. Scaling relations for the resulting fluctuation spectra are derived. An estimate for the collisional cutoff is provided. The importance of adequately modeling and resolving collisions in gyrokinetic simulations is biefly discussed, as well as the relevance of these results to understanding the dissipation-range turbulence in the solar wind and the electrostatic microturbulence in fusion plasmas.

A. A. Schekochihin; S. C. Cowley; W. Dorland; G. W. Hammett; G. G. Howes; G. G. Plunk; E. Quataert; T. Tatsuno

2008-06-05T23:59:59.000Z

342

Quantum Gravity and Turbulence  

E-Print Network (OSTI)

We apply recent advances in quantum gravity to the problem of turbulence. Adopting the AdS/CFT approach we propose a string theory of turbulence that explains the Kolmogorov scaling in 3+1 dimensions and the Kraichnan and Kolmogorov scalings in 2+1 dimensions. In the gravitational context, turbulence is intimately related to the properties of spacetime, or quantum, foam.

Vishnu Jejjala; Djordje Minic; Y. Jack Ng; Chia-Hsiung Tze

2010-05-18T23:59:59.000Z

343

Northerly surface wind events over the eastern North Pacific Ocean : spatial distribution, seasonality, atmospheric circulation, and forcing  

E-Print Network (OSTI)

D. (2005), California Wind Resources, CEC publication # CEC-level inversions with surface wind and temperature at PointD. W. Stuart (1986), Mesoscale wind variability near Point

Taylor, Stephen V.

2006-01-01T23:59:59.000Z

344

On apparent temperature in low-frequency Alfvenic turbulence  

SciTech Connect

Low-frequency, parallel propagating Alfvenic turbulence in collisionless plasmas is theoretically studied. Alfvenic turbulence is derived as an equilibrium state (Beltrami field) in the magnetohydrodynamic equations with the pressure anisotropy and multi-species of ions. It is shown that the conservation of the total 'apparent temperature' corresponds to the Bernoulli law. A simple model of the radially expanding solar wind including Alfvenic turbulence is also discussed. The conversion of the wave energy in the 'apparent temperature' into the 'real temperature' is facilitated with increasing radial distance.

Nariyuki, Yasuhiro [Faculty of Human Development, University of Toyama, 3190, Toyama City, Toyama 930-8555 (Japan)

2012-08-15T23:59:59.000Z

345

Low-Frequency Variability in Shallow-Water Models of the Wind-Driven Ocean Circulation. Part I: Steady-State Solution  

Science Conference Proceedings (OSTI)

Successive bifurcations—from steady states through periodic to aperiodic solutions—are studied in a shallow-water, reduced-gravity, 2˝-layer model of the midlatitude ocean circulation subject to time-independent wind stress. The bifurcation ...

Eric Simonnet; Michael Ghil; Kayo Ide; Roger Temam; Shouhong Wang

2003-04-01T23:59:59.000Z

346

Economic and technical impacts of wind variability and intermittency on long-term generation expansion planning in the U.S  

E-Print Network (OSTI)

Electricity power systems are a major source of carbon dioxide emissions and are thus required to change dramatically under climate policy. Large-scale deployment of wind power has emerged as one key driver of the shift ...

Brun, Caroline Elisabeth Hénia

2011-01-01T23:59:59.000Z

347

Interdecadal Sea Surface Temperature Variability in the Equatorial Pacific Ocean. Part II: The Role of Equatorial/Off-Equatorial Wind Stresses in a Hybrid Coupled Model  

Science Conference Proceedings (OSTI)

Many modeling studies have been carried out to investigate the role of oceanic Rossby waves linking the off-equatorial and equatorial Pacific Ocean. Although the equatorial ocean response to off-equatorial wind stress forcing alone tends to be ...

Shayne McGregor; Neil J. Holbrook; Scott B. Power

2008-09-01T23:59:59.000Z

348

Design and Test of DC Voltage Link Conversion System and Brushless Doubly-Fed Induction Generator for Variable-Speed Wind Energy Applications: August 1999--May 2003  

SciTech Connect

This report describes four low-cost alternative power converters for processing the power developed by a doubly fed wound-rotor induction generator for wind energy conversion systems.

Lipo, T.A.; Panda, D.; Zarko, D.

2005-11-01T23:59:59.000Z

349

Design and Test of a Variable Speed Wind Turbine System Employing a Direct Drive Axial Flux Synchronization Generator: 29 October 2002 - 31 December 2005  

SciTech Connect

The goal of this funded research project is the definition, analytical investigation, modeling, and prototype realization of a current-source conversion topology tailored to high-power wind turbines.

Lipo, T. A.; Tenca, P.

2006-07-01T23:59:59.000Z

350

Observation of 3–6-Day Meridional Wind Oscillations over the Tropical Pacific, 1973–1992: Vertical Structure and Interannual Variability  

Science Conference Proceedings (OSTI)

Rawinsonde data from tropical Pacific stations were examined for westward-propagating 3–6-day meridional wind oscillations in the troposphere and lower stratosphere, 1973–1992. Four types were identified from cross- spectrum and principal ...

Timothy J. Dunkerton

1993-10-01T23:59:59.000Z

351

Influence of a New Turbulence Regime on the Global Air–Sea Heat Fluxes  

Science Conference Proceedings (OSTI)

Recent research has found that boundary layer turbulence changes its organization as the stratification approaches neutral from the unstable side. When the thermal forcing weakens in combination with wind speed above approximately 10 m s?1, ...

Erik Sahlée; Ann-Sofi Smedman; Anna Rutgersson; Ulf Högström

2008-11-01T23:59:59.000Z

352

The Influence of Whitecapping Waves on the Vertical Structure of Turbulence in a Shallow Estuarine Embayment  

Science Conference Proceedings (OSTI)

The vertical distribution of the turbulent kinetic energy dissipation rate was measured using an array of four acoustic Doppler velocimeters in the shallow embayment of Grizzly Bay, San Francisco Bay, California. Owing to the combination of wind ...

Nicole L. Jones; Stephen G. Monismith

2008-07-01T23:59:59.000Z

353

Turbulent Fluxes in the Hurricane Boundary Layer. Part II: Latent Heat Flux  

Science Conference Proceedings (OSTI)

As part of the recent ONR-sponsored Coupled Boundary Layer Air–Sea Transfer (CBLAST) Departmental Research Initiative, an aircraft was instrumented to carry out direct turbulent flux measurements in the high wind boundary layer of a hurricane. ...

William M. Drennan; Jun A. Zhang; Jeffrey R. French; Cyril McCormick; Peter G. Black

2007-04-01T23:59:59.000Z

354

Equilibrium Geostrophic Turbulence I: A Reference Solution in a ?-Plane Channel  

Science Conference Proceedings (OSTI)

A numerical solution is calculated for quasi-geostrophic, adiabatic, baroclinic, wind-driven flow in a ? channel. The rates of driving and dissipation are such that the solution is turbulent in equilibrium. The equilibrium state is characterized ...

James C. McWilliams; Julianna H. S. Chow

1981-07-01T23:59:59.000Z

355

Doppler Lidar Measurements of Turbulent Structure Function over an Urban Area  

Science Conference Proceedings (OSTI)

Analysis of radial wind velocity data from the Salford pulsed Doppler infrared lidar is used to calculate turbulent spectral statistics over the city of Salford in the United Kingdom. The results presented here, first, outline the error ...

F. Davies; C. G. Collier; G. N. Pearson; K. E. Bozier

2004-05-01T23:59:59.000Z

356

An Algorithm for Forecasting Mountain Wave–Related Turbulence in the Stratosphere  

Science Conference Proceedings (OSTI)

A global mountain wave parameterization for prediction of wave-related displacements and turbulence is described. The parameterization is used with input from National Meteorological Center analyses of wind and temperature to examine small-scale ...

Julio T. Bacmeister; Paul A. Newman; Bruce L. Gary; K. Roland Chan

1994-06-01T23:59:59.000Z

357

NERC Presentation: Accommodating High Levels of Variable Generation...  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

high levels of variable electricity eneration. Variable resources are types of electric power generation that rely on an uncontrolled, "variable" fuel (e.g. wind, sunlight,...

358

Wind loads on flat plate photovoltaic array fields. Phase II. Final report  

SciTech Connect

This report describes a theoretical study of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays. Local pressure distributions and total aerodynamic forces on the arrays are shown. Design loads are presented to cover the conditions of array angles relative to the ground from 20/sup 0/ to 60/sup 0/, variable array spacings, a ground clearance gap up to 1.2 m (4 ft) and array slant heights of 2.4 m (8 ft) and 4.8 m (16 ft). Several means of alleviating the wind loads on the arrays are detailed. The expected reduction of the steady state wind velocity with the use of fences as a load alleviation device are indicated to be in excess of a factor of three for some conditions. This yields steady state wind load reductions as much as a factor of ten compared to the load incurred if no fence is used to protect the arrays. This steady state wind load reduction is offset by the increase in turbulence due to the fence but still an overall load reduction of 2.5 can be realized. Other load alleviation devices suggested are the installation of air gaps in the arrays, blocking the flow under the arrays and rounding the edges of the array. Included is an outline of a wind tunnel test plan to supplement the theoretical study and to evaluate the load alleviation devices.

Miller, R.; Zimmerman, D.

1979-09-01T23:59:59.000Z

359

Development of Wind Speed Forecasting Model Based on the Weibull Probability Distribution  

Science Conference Proceedings (OSTI)

Wind is a variable energy source. The power output of a wind turbine generator (WTG) unit, therefore, fluctuates with wind speed variations. Accurate models reflecting the variability of wind speed is hence required in both reliability evaluation of ... Keywords: Wind Energy, Wind Speed Forecasting Model, Weibull Distribution, Maximum Likelihood Method, Time Series Model

Ruigang Wang; Wenyi Li; B. Bagen

2011-02-01T23:59:59.000Z

360

Wave Breaking Dissipation in a Young Wind Sea  

Science Conference Proceedings (OSTI)

Coupled in situ and remote sensing measurements of young, strongly-forced, wind waves are applied to assess the role of breaking in an evolving wavefield. In situ measurements of turbulent energy dissipation from wave-following “SWIFT” drifters ...

Michael Schwendeman; Jim Thomson; Johannes R. Gemmrich

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Modeling Compressed Turbulence  

Science Conference Proceedings (OSTI)

From ICE to ICF, the effect of mean compression or expansion is important for predicting the state of the turbulence. When developing combustion models, we would like to know the mix state of the reacting species. This involves density and concentration fluctuations. To date, research has focused on the effect of compression on the turbulent kinetic energy. The current work provides constraints to help development and calibration for models of species mixing effects in compressed turbulence. The Cambon, et al., re-scaling has been extended to buoyancy driven turbulence, including the fluctuating density, concentration, and temperature equations. The new scalings give us helpful constraints for developing and validating RANS turbulence models.

Israel, Daniel M. [Los Alamos National Laboratory

2012-07-13T23:59:59.000Z

362

MHD Turbulence Revisited  

E-Print Network (OSTI)

Kraichnan (1965) proposed that MHD turbulence occurs as a result of collisions between oppositely directed Alfvén wave packets. Recent work has generated some controversy over the nature of non linear couplings between colliding Alfvén waves. We find that the resolution to much of the confusion lies in the existence of a new type of turbulence, intermediate turbulence, in which the cascade of energy in the inertial range exhibits properties intermediate between those of weak and strong turbulent cascades. Some properties of intermediate MHD turbulence are: (i) in common with weak turbulent cascades, wave packets belonging to the inertial range are long lived; (ii) however, components of the strain tensor are so large that, similar to the situation in strong turbulence, perturbation theory is not applicable; (iii) the breakdown of perturbation theory results from the divergence of neighboring field lines due to wave packets whose perturbations in velocity and magnetic fields are localized, but whose perturba...

Goldreich, P

1996-01-01T23:59:59.000Z

363

Comparing Decision Rules for Siting Interconnected Wind Farms  

Science Conference Proceedings (OSTI)

The variability and non-dispatchability of wind power creates many challenges for the operators of electric transmission systems. Current U.S. wind energy policies are focused on encouraging quantities of wind power without much attention paid to quality ...

Paras Choudhary; Seth Blumsack; George Young

2011-01-01T23:59:59.000Z

364

Spatial Variation in Turbulent Heat Fluxes in Drake Passage  

Science Conference Proceedings (OSTI)

High-resolution underway shipboard atmospheric and oceanic observations collected in Drake Passage from 2000 to 2009 are used to examine the spatial scales of turbulent heat fluxes and flux-related state variables. The magnitude of the seasonal ...

ChuanLi Jiang; Sarah T. Gille; Janet Sprintall; Kei Yoshimura; Masao Kanamitsu

2012-03-01T23:59:59.000Z

365

Wind shear for large wind turbine generators at selected tall tower sites  

DOE Green Energy (OSTI)

The objective of the study described in this report is to examine the nature of wind shear profiles and their variability over the height of large horizontal-axis wind turbines and to provide information on wind shear relevant to the design and opertion of large wind turbines. Wind turbine fatigue life and power quality are related through the forcing functions on the blade to the shapes of the wind shear profiles and their fluctuations over the disk of rotation.

Elliott, D.L.

1984-04-01T23:59:59.000Z

366

Effects of Temporal Wind Patterns on the Value of Wind-Generated Electricity in California and the Northwest  

E-Print Network (OSTI)

Modeling Utility-Scale Wind Power Plants Part 2: Capac- ityNakafuji, "Grid Im- pacts of Wind Power Variability: RecentParsons, and M. Milligan, "Wind Power Impacts on Electric-

Wiser, Ryan H

2008-01-01T23:59:59.000Z

367

Estimates of Turbulence from Numerical Weather Prediction Model Output with Applications to Turbulence Diagnosis and Data Assimilation  

Science Conference Proceedings (OSTI)

Estimates of small-scale turbulence from numerical model output are produced from local estimates of the spatial structure functions of model variables such as the velocity and temperature. The key assumptions used are the existence of a ...

Rod Frehlich; Robert Sharman

2004-10-01T23:59:59.000Z

368

EERE: Wind  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

EERE: Buildings The U.S. Department of Energy funds R&D to develop wind energy. Learn about the DOE Wind Program, how to use wind energy and get financial incentives, and access...

369

WIND ENERGY Wind Energ. (2012)  

E-Print Network (OSTI)

WIND ENERGY Wind Energ. (2012) Published online in Wiley Online Library (wileyonlinelibrary since energy production depends non-linearly on wind speed (U ), and wind speed observa- tions for the assessment of future long-term wind supply A. M. R. Bakker1 , B. J. J. M. Van den Hurk1 and J. P. Coelingh2 1

Haak, Hein

370

Low-Frequency Variability in Shallow-Water Models of the Wind-Driven Ocean Circulation. Part II: Time-Dependent Solutions  

Science Conference Proceedings (OSTI)

The time-dependent wind-driven ocean circulation is investigated for both a rectangular and a North Atlantic–shaped basin. Multiple steady states in a 2˝-layer shallow-water model and their dependence on various parameters and other model ...

Eric Simonnet; Michael Ghil; Kayo Ide; Roger Temam; Shouhong Wang

2003-04-01T23:59:59.000Z

371

Observations of Vertical Wind Shear Heterogeneity in Convective Boundary Layers  

Science Conference Proceedings (OSTI)

Dual-Doppler wind syntheses from mobile radar observations obtained during the International H2O Project document some of the spatial variability of vertical wind profiles in convective boundary layers. Much of the variability of popular ...

Paul Markowski; Yvette Richardson

2007-03-01T23:59:59.000Z

372

Spectral Wave–Turbulence Decomposition  

Science Conference Proceedings (OSTI)

A new method of wave–turbulence decomposition is introduced, for which the only instrument required is one high-frequency pointwise velocity sensor. This is a spectral method that assumes equilibrium turbulence and no wave–turbulence interaction. ...

Jeremy D. Bricker; Stephen G. Monismith

2007-08-01T23:59:59.000Z

373

An Analysis of Low-Frequency Maritime Atmospheric Turbulence  

Science Conference Proceedings (OSTI)

New data are presented for the spectrum of turbulent wind energy under maritime conditions in the frequency region 1.0–0.03 mHz. The corresponding measurements were made at five levels on a mast 46 m high on a small islet off the coast of central ...

Johannes Gjerstad; Svein Erik Aasen; Helge I. Andersson; Iver Brevik; Jřrgen Lřvseth

1995-08-01T23:59:59.000Z

374

Kinematics of Turbulence Convected by a Random Wave Field  

Science Conference Proceedings (OSTI)

Turbulent velocity spectra measured beneath wind waves show a large enhancement about the central wave frequency. A “5/3" frequency dependence can be seen both above and below the central peak, but with an apparent increase in spectral density at ...

J. L. Lumley; E. A. Terray

1983-11-01T23:59:59.000Z

375

Viscous Dissipation of Turbulence Kinetic Energy in Storms  

Science Conference Proceedings (OSTI)

In this note the magnitude of the viscous dissipation of turbulence kinetic energy in the surface layer of storms is investigated. It is shown that the layer-integrated dissipative heating is a cubic function of the wind speed. The magnitude of ...

Steven Businger; Joost A. Businger

2001-12-01T23:59:59.000Z

376

Near-Surface Turbulence in the Presence of Breaking Waves  

Science Conference Proceedings (OSTI)

Observations with a three-axis pulse-to-pulse coherent acoustic Doppler profiler and acoustic resonators reveal the turbulence and bubble field beneath breaking waves in the open ocean at wind speeds up to 14 m s?1. About 55%–80% of velocity ...

Johannes R. Gemmrich; David M. Farmer

2004-05-01T23:59:59.000Z

377

Near-Neutral Surface Layer Turbulence at the Boulder Atmospheric Observatory Tower: Evidence of Increasing Vertical Turbulence with Height  

Science Conference Proceedings (OSTI)

Wind and turbulence profiles were analyzed during breezy, near-neutral conditions at the Boulder Atmospheric Observatory tower to quantify the effects of an abrupt 20- to 30-m increase in terrain located 3–5 km west of the tower. Results indicate ...

Brent M. Bowen

2000-05-01T23:59:59.000Z

378

Section 1: Interfacial Turbulence and AirWater Scalar Transfer Turbulence and wave dynamics across gasliquid interfaces 1  

E-Print Network (OSTI)

The calculation of the gas transfer between the ocean and atmosphere13 S.A. Kitaigorodskii The influence of wind relationship to airwater gas transfer rates51 D. Turney, S. Banerjee Turbulent gas flux measurements near the airwater interface in an oscillating-grid tank 65 J.G. Janzen, H.E. Schulz, G.H. Jirka Sensible and latent

Takada, Shoji

379

Fossil turbulence and fossil turbulence waves can be dangerous  

E-Print Network (OSTI)

Turbulence is defined as an eddy-like state of fluid motion where the inertial-vortex forces of the eddies are larger than any other forces that tend to damp the eddies out. By this definition, turbulence always cascades from small scales where vorticity is created to larger scales where turbulence fossilizes. Fossil turbulence is any perturbation in a hydrophysical field produced by turbulence that persists after the fluid is no longer turbulent at the scale of the perturbation. Fossil turbulence patterns and fossil turbulence waves preserve and propagate energy and information about previous turbulence. Ignorance of fossil turbulence properties can be dangerous. Examples include the Osama bin Laden helicopter crash and the Air France 447 Airbus crash, both unfairly blamed on the pilots. Observations support the proposed definitions, and suggest even direct numerical simulations of turbulence require caution.

Carl H Gibson

2012-11-25T23:59:59.000Z

380

NREL Develops New Controls that Proactively Adapt to the Wind (Fact Sheet)  

Science Conference Proceedings (OSTI)

Until now, wind turbine controls that reduce the impacts of wind gusts and turbulence were always reactive -- responding to the wind rather than anticipating it. But with today's laser-based sensors that measure wind speed ahead of the turbine, researchers at the National Renewable Energy Laboratory (NREL) and their industry partners are developing more intelligent controls. The world's first field tests of these controls are currently underway at the National Wind Technology Center (NWTC) at NREL, with plans for future commercialization.

Not Available

2012-10-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

NREL Develops New Controls that Proactively Adapt to the Wind (Fact Sheet)  

Science Conference Proceedings (OSTI)

Until now, wind turbine controls that reduce the impacts of wind gusts and turbulence were always reactive-responding to the wind rather than anticipating it. But with today's laser-based sensors that measure wind speed ahead of the turbine, researchers at the National Renewable Energy Laboratory (NREL) and their industry partners are developing more intelligent controls. The world's first field tests of these controls are currently underway at the National Wind Technology Center (NWTC) at NREL, with plans for future commercialization.

Not Available

2012-11-01T23:59:59.000Z

382

Pitch angle control in wind turbines above the rated wind speed by multi-layer perceptron and radial basis function neural networks  

Science Conference Proceedings (OSTI)

In wind energy conversion systems, one of the operational problems is the changeability and discontinuity of wind. In most cases, wind speed can fluctuate rapidly. Hence, quality of produced energy becomes an important problem in wind energy conversion ... Keywords: Neural network-based controller, Pitch control, Variable-speed wind turbine, Wind energy conversion systems

Ahmet Serdar Yilmaz; Zafer Özer

2009-08-01T23:59:59.000Z

383

ASYMMETRIC SOLAR WIND ELECTRON DISTRIBUTIONS  

Science Conference Proceedings (OSTI)

The present paper provides a possible explanation for the solar wind electron velocity distribution functions possessing asymmetric energetic tails. By numerically solving the electrostatic weak turbulence equations that involve nonlinear interactions among electrons, Langmuir waves, and ion-sound waves, it is shown that different ratios of ion-to-electron temperatures lead to the generation of varying degrees of asymmetric tails. The present finding may be applicable to observations in the solar wind near 1 AU and in other regions of the heliosphere and interplanetary space.

Yoon, Peter H.; Kim, Sunjung; Lee, Junggi; Lee, Junhyun; Park, Jongsun; Park, Kyungsun; Seough, Jungjoon [School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701 (Korea, Republic of); Hong, Jinhy [Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of)

2012-08-20T23:59:59.000Z

384

Upstream Measurements of Wind Profiles with Doppler Lidar for Improved Wind Energy Integration  

DOE Green Energy (OSTI)

New upstream measurements of wind profiles over the altitude range of wind turbines will be produced using a scanning Doppler lidar. These long range high quality measurements will provide improved wind power forecasts for wind energy integration into the power grid. The main goal of the project is to develop the optimal Doppler lidar operating parameters and data processing algorithms for improved wind energy integration by enhancing the wind power forecasts in the 30 to 60 minute time frame, especially for the large wind power ramps. Currently, there is very little upstream data at large wind farms, especially accurate wind profiles over the full height of the turbine blades. The potential of scanning Doppler lidar will be determined by rigorous computer modeling and evaluation of actual Doppler lidar data from the WindTracer system produced by Lockheed Martin Coherent Technologies, Inc. of Louisville, Colorado. Various data products will be investigated for input into numerical weather prediction models and statistically based nowcasting algorithms. Successful implementation of the proposed research will provide the required information for a full cost benefit analysis of the improved forecasts of wind power for energy integration as well as the added benefit of high quality wind and turbulence information for optimal control of the wind turbines at large wind farms.

Rodney Frehlich

2012-10-30T23:59:59.000Z

385

Passively cooled direct drive wind turbine  

SciTech Connect

A wind turbine is provided that passively cools an electrical generator. The wind turbine includes a plurality of fins arranged peripherally around a generator house. Each of the fins being oriented at an angle greater than zero degrees to allow parallel flow of air over the fin. The fin is further tapered to allow a constant portion of the fin to extend beyond the air stream boundary layer. Turbulence initiators on the nose cone further enhance heat transfer at the fins.

Costin, Daniel P. (Chelsea, VT)

2008-03-18T23:59:59.000Z

386

Improvement Of The Wind Farm Model Flap For Offshore Applications  

E-Print Network (OSTI)

The wind farm program FLaP (Farm Layout Program), developed at the University of Oldenburg, has been extended to improve the description of wake development in offshore conditions, especially the low ambient turbulence and the effect of atmospheric stability. Model results have been compared with measurements from the Danish offshore wind farm Vindeby. Vertical wake profiles and mean turbulence intensities in the wake were compared for 32 scenarios of single, double and quintuple wake cases with different mean wind speed, turbulence intensity and atmospheric stability. It was found that within the measurement uncertainties the results of the wake model compares well with the measurements for the most important ambient conditions. The effect of the low turbulence intensity offshore on the wake development was modelled well. Deviations have been found when atmospheric stability deviates from near-neutral conditions. Especially for stable atmospheric conditions both the free flow model and the wake model do not give satisfying results.

Bernhard Lange; Hans-peter Waldl; Rebecca Barthelmie; Algert Gil Guerrero; Detlev Heinemann

2002-01-01T23:59:59.000Z

387

Analysis of the Performance Benefits of Short-Term Energy Storage in Wind-Diesel Hybrid Power Systems  

Science Conference Proceedings (OSTI)

A variety of prototype high penetration wind-diesel hybrid power systems have been implemented with different amounts of energy storage. They range from systems with no energy storage to those with many hours worth of energy storage. There has been little consensus among wind-diesel system developers as to the appropriate role and amount of energy storage in such systems. Some researchers advocate providing only enough storage capacity to supply power during the time it takes the diesel genset to start. Others install large battery banks to allow the diesel(s) to operate at full load and/or to time-shift the availability of wind-generated electricity to match the demand. Prior studies indicate that for high penetration wind-diesel systems, short-term energy storage provides the largest operational and economic benefit. This study uses data collected in Deering, Alaska, a small diesel-powered village, and the hybrid systems modeling software Hybrid2 to determine the optimum amount of short-term storage for a particular high penetration wind-diesel system. These findings were then generalized by determining how wind penetration, turbulence intensity, and load variability affect the value of short term energy storage as measured in terms of fuel savings, total diesel run time, and the number of diesel starts.

Shirazi, M.; Drouilhet, S.

1997-04-01T23:59:59.000Z

388

The Economic Optimization of Wind Turbine Design .  

E-Print Network (OSTI)

??This thesis studies the optimization of a variable speed, three blade, horizontal-axis wind turbine. The design parameters considered are the rotor diameter, hub height and… (more)

Schmidt, Michael Frank

2007-01-01T23:59:59.000Z

389

IMPROVEMENT OF THE WIND FARM MODEL FLAP FOR OFFSHORE APPLICATIONS Bernhard Lange(1), Hans-Peter Waldl(1)(2), Rebecca Barthelmie(3), Algert Gil Guerrero(1)(4), Detlev Heinemann(1)  

E-Print Network (OSTI)

Vindeby. Vertical wake profiles and mean turbulence intensities in the wake were compared for 32 scenarios. Additionally, an estimation of turbulence intensity in the wind farm is essential for the load assumptions used in the description of the ambient vertical wind speed profile, but most importantly it leads to a low and wind speed

390

Chemical turbulence equivalent to Nikolavskii turbulence  

E-Print Network (OSTI)

We find evidence that a certain class of reaction-diffusion systems can exhibit chemical turbulence equivalent to Nikolaevskii turbulence. The distinctive characteristic of this type of turbulence is that it results from the interaction of weakly stable long-wavelength modes and unstable short-wavelength modes. We indirectly study this class of reaction-diffusion systems by considering an extended complex Ginzburg-Landau (CGL) equation that was previously derived from this class of reaction-diffusion systems. First, we show numerically that the power spectrum of this CGL equation in a particular regime is qualitatively quite similar to that of the Nikolaevskii equation. Then, we demonstrate that the Nikolaevskii equation can in fact be obtained from this CGL equation through a phase reduction procedure applied in the neighborhood of a codimension-two Turing--Benjamin-Feir point.

Dan Tanaka

2004-03-09T23:59:59.000Z

391

Wind Energy  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

FUPWG Meeting FUPWG Meeting NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Robi Robichaud November 18, 2009 Topics Introduction Review of the Current Wind Market Drivers for Wind Development Siting g Issues Wind Resource Assessment Wind Characteristics Wind Power Potential Basic Wind Turbine Theory Basic Wind Turbine Theory Types of Wind Turbines Facts About Wind Siting Facts About Wind Siting Wind Performance 1. United States: MW 1 9 8 2 1 9 8 3 1 9 8 4 1 9 8 5 1 9 8 6 1 9 8 7 1 9 8 8 1 9 8 9 1 9 9 0 1 9 9 1 1 9 9 2 1 9 9 3 1 9 9 4 1 9 9 5 1 9 9 6 1 9 9 7 1 9 9 8 1 9 9 9 2 0 0 0 2 0 0 1 2 0 0 2 2 0 0 3 2 0 0 4 2 0 0 5 2 0 0 6 2 0 0 7 2 0 0 8 Current Status of the Wind Industry Total Global Installed Wind Capacity Total Global Installed Wind Capacity Total Global Installed Wind Capacity

392

NREL: Wind Research - Computer-Aided Engineering Tools  

NLE Websites -- All DOE Office Websites (Extended Search)

Computer-Aided Engineering Tools Computer-Aided Engineering Tools Illustration of an offshore wind turbine on a barge with an illustration of how the moorings would work. A simulation of a 5-MW wind turbine on an offshore semi-submersible with catenary moorings. The National Wind Technology Center (NWTC) at NREL develops advanced computer-aided engineering (CAE) tools to support the wind and water power industries with state-of-the-art design and analysis capabilities. We have developed many software tools that produce realistic models that simulate the behavior of wind and water power technologies in complex environments-storm winds, waves offshore, earthquake loading, and extreme turbulence-and model the effects of turbulent inflow, unsteady aerodynamic forces, structural dynamics, drivetrain response, control

393

Wind: wind speed and wind power density GIS data at 50m above ground and  

Open Energy Info (EERE)

Kenya from RisoeDTU Kenya from RisoeDTU Dataset Summary Description (Abstract): These data are results from the KAMM/WASP studies for Kenya. The KAMM/WAsP methodology uses a set of wind classes to represent wind conditions for the mapped region. A mesoscale simulation for each wind class, using KAMM (Karlsruhe Mesoscale Model), is performed and statistics performed on the model output. The results are a summary of the simulated wind climate, and ii. a wind atlas, a summary of the wind climate standardized to flat, uniform roughness terrain. (Purpose): The product is intended to be used to estimate the wind resource potential in the country including the the spatial variability. This map covers regions where long term measurements are not available. In a sense this is the point of the

394

Methods for Increasing Region 2 Power Capture on a Variable Speed HAWT: Preprint  

DOE Green Energy (OSTI)

The standard region 2 control scheme for a variable speed wind turbine, tc= kw2, has several shortcomings that can result in significant power loss. The first of these is that there is no accurate way to determine the gain k; modeling programs are not accurate enough to represent all of the complex aerodynamics, and these aerodynamics change over time. Furthermore, it is not certain whether the value of k used in the standard control even provides for the maximum energy capture under real-world turbulent conditions. New control ideas are introduced to address these issues. First, it is shown in simulation that using smaller values of k than the standard can result in increased power capture. Second, an optimally tracking rotor control scheme improves upon the standard scheme by assisting the rotor speed in tracking wind speed fluctuations more rapidly. Finally, an adaptive control scheme is proposed that allows for maximum power capture despite parameter uncertainty.

Johnson, K. E.; Fingersh, L. J.; Balas, M. J.; Pao, L. Y.

2003-11-01T23:59:59.000Z

395

Four Lectures on Turbulent Combustion  

E-Print Network (OSTI)

Four Lectures on Turbulent Combustion N. Peters Institut f¨ur Technische Mechanik RWTH Aachen Turbulent Combustion: Introduction and Overview 1 1.1 Moment Methods in Modeling Turbulence with Combustion and Velocity Scales . . . . . . . . . . . 11 1.4 Regimes in Premixed Turbulent Combustion

Peters, Norbert

396

NREL: Wind Research - Utility Grid Integration  

NLE Websites -- All DOE Office Websites (Extended Search)

Utility Grid Integration Utility Grid Integration Photo of a wind farm in Lawton, Oklahoma where NREL researchers studied the impact of wind energy on farming system operations. NREL researchers analyzed research data collected from this wind farm in Lawton, Oklahoma, to determine the impacts of wind energy on systems operations. NREL researchers analyzed research data collected from this wind farm in Lawton, Oklahoma, to determine the impacts of wind energy on systems operations. The integration of wind energy into the electric generation industry's supply mix is one of the issues industry grapples with. The natural variability of the wind resource raises concerns about how wind can be integrated into routine grid operations, particularly with regard to the effects of wind on regulation, load following, scheduling, line voltage,

397

A Model of Strongly Forced Wind Waves  

Science Conference Proceedings (OSTI)

A model of surface waves generated on deep water by strong winds is proposed. A two-layer approximation is adopted, in which a shallow turbulent layer overlies the lower, infinitely deep layer. The dynamics of the upper layer, which is directly ...

Alexey V. Fedorov; W. Kendall Melville

2009-10-01T23:59:59.000Z

398

Density Spectrum in the Solar Wind Plasma  

E-Print Network (OSTI)

The density fluctuation spectrum in the solar wind reveals a Kolmogorov-like scaling with a spectral slope of -5/3 in wavenumber space. The energy transfer process in the magnetized solar wind, characterized typically by MHD turbulence, over extended length-scales remains an unresolved paradox of modern turbulence theories, raising the question of how a compressible magnetofluid exhibits a turbulent spectrum that is characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfv\\'enic, supersonic and strongly magnetized plasma fluid. It is shown that a Kolmogorov-like density spectrum can develop by plasma motions that are dominated by Alfv\\'enic cascades whereas compressive modes are dissipated.

Shaikh, Dastgeer

2009-01-01T23:59:59.000Z

399

The first turbulent combustion  

E-Print Network (OSTI)

The first turbulent combustion arises in a hot big bang cosmological model Gibson (2004) where nonlinear exothermic turbulence permitted by quantum mechanics, general relativity, multidimensional superstring theory, and fluid mechanics cascades from Planck to strong force freeze out scales with gravity balancing turbulent inertial-vortex forces. Interactions between Planck scale spinning and non-spinning black holes produce high Reynolds number turbulence and temperature mixing with huge Reynolds stresses driving the rapid inflation of space. Kolmogorovian turbulent temperature patterns are fossilized as strong-force exponential inflation stretches them beyond the scale of causal connection ct where c is light speed and t is time. Fossil temperature turbulence patterns seed nucleosynthesis, and then hydro-gravitational structure formation in the plasma epoch, Gibson (1996, 2000). Evidence about formation mechanisms is preserved by cosmic microwave background temperature anisotropies. CMB spectra indicate hydro-gravitational fragmentation at supercluster to galaxy masses in the primordial plasma with space stretched by \\~10^50. Bershadskii and Sreenivasan (2002, 2003) CMB multi-scaling coefficients support a strong turbulence origin for the anisotropies prior to the plasma epoch.

Carl H. Gibson

2005-01-19T23:59:59.000Z

400

SPECTRUM OF KINETIC-ALFVEN TURBULENCE  

Science Conference Proceedings (OSTI)

A numerical study of strong kinetic-Alfven turbulence at scales smaller than the ion gyroscale is presented, and a phenomenological model is proposed that argues that magnetic and density fluctuations are concentrated mostly in two-dimensional structures, which leads to their Fourier energy spectra E(k ){proportional_to}k {sup -8/3} , where k is the wavevector component normal to the strong background magnetic field. The results may provide an explanation for recent observations of magnetic and density fluctuations in the solar wind at sub-proton scales.

Boldyrev, Stanislav; Perez, Jean Carlos [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)

2012-10-20T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Synoptic and local influences on boundary layer processes, with an application to California wind power  

E-Print Network (OSTI)

Makarov, Y. , 2007: Wind Integration Issues and So- lutionsexpectations, and integration strategy for any wind powerwind climate and variability. Site design and operation, as well as market integration

Mansbach, David K

2010-01-01T23:59:59.000Z

402

The effect of high penetration of wind power on primary frequency control of power systems.  

E-Print Network (OSTI)

??In this work, a power system with wind power units and hydro power units are considered. The hydro power unit and variable speed wind turbine… (more)

Motamed, Bardia

2013-01-01T23:59:59.000Z

403

How Do High Levels of Wind and Solar Impact the Grid? The Western...  

NLE Websites -- All DOE Office Websites (Extended Search)

displaced, which leaves coal to accommodate the variability of the wind and solar. Wind, Solar and Load Data 3TIER Group employed a mesoscale Numerical Weather Prediction (NWP)...

404

Edge Turbulence Velocity Changes with Lithium Coating on NSTX  

SciTech Connect

Lithium coating improves energy confinement and eliminates edge localized modes in NSTX, but the mechanism of this improvement is not yet well understood. We used the gas-puff-imaging (GPI) diagnostic on NSTX to measure the changes in edge turbulence which occurred during a scan with variable lithium wall coating, in order to help understand the reason for the confinement improvement with lithium. There was a small increase in the edge turbulence poloidal velocity and a decrease in the poloidal velocity fluctuation level with increased lithium. The possible effect of varying edge neutral density on turbulence damping was evaluated for these cases in NSTX. __________________________________________________

A. Cao, S.J. Zweben, D.P. Stotler, M. Bell, A. Diallo, S.M. Kaye and B. LeBlanc

2012-08-10T23:59:59.000Z

405

Wind loading on solar collectors  

DOE Green Energy (OSTI)

The present design methodology for the determination of wind loading on the various solar collectors has been reviewed and assessed. The total force coefficients of flat plates of aspect ratios 1.0 and 3.0, respectively, at various angles of attack obtained by using the guidelines of the ANSI A58.1-1982, have been compared with those obtained by using the methodology of the ASCE Task Committee, 1961, and the experimental results of the full-scale test of heliostats by Peglow. The turbulent energy spectra, currently employed in the building code, are compared with those of Kaimal et al., Lumley, and Ponofsky for wind velocities of 20.0 m/s and 40.24 m/s at an elevation of 9.15 m. The longitudinal spectra of the building code overestimates the Kaimal spectra in the frequency range of 0.007 Hz to 0.08 Hz and underestimates beyond the frequency of 0.08 Hz. The peak angles of attack, on the heliostat, stowed in horizontal position, due to turbulent vertical and lateral components of wind velocity, have been estimated by using Daniel's methodology for three wind velocities and compared with the value suggested by the code. The experimental results of a simple test in the laboratory indicate the feasibility of decreasing the drag forces of the flat plate by reducing the solidity ratio.

Bhaduri, S.; Murphy, L.M.

1985-06-01T23:59:59.000Z

406

New England Wind Forum: Technical Challenges  

Wind Powering America (EERE)

Technical Challenges Technical Challenges Wind power is by its nature variable, and as a result, it differs from the majority of generation supplying the electric grid. Aspects of this variability are often cited as shortcomings. For instance, the fact that wind power will not be as regularly and reliably available at system peak times as most other generators is sometimes used to argue that wind power requires additional backup resources by other generation on a one-to-one basis. And wind's relatively low capacity factor (a ratio of the total energy output relative to the theoretical sustained peak output) is sometimes used to characterize wind generators as inefficient. It's been stated that other generation will have to be operated in such an inefficient manner to react to wind that it will not reduce fossil fuel usage or emissions. Here we address concerns that wind power's variability will eradicate any expected benefit.

407

A Case Study to Evaluate the Reliability Impact of Large-Scale Wind Generation: Incorporating Variable Generation and Loads into Rel iability-based Transmission Planning  

Science Conference Proceedings (OSTI)

This report describes a case study using a probabilistic framework to capture variations in output of variable generation connected to the transmission system along with system loads. The research in 2010, 2011, and some part of 2012 focused on developing the probabilistic model framework. The focus of the 2012 work was to use this model on a real-world (as opposed to a test system) transmission planning case along with data for all the variable generation and system loads modeled in the case to ...

2013-08-29T23:59:59.000Z

408

Distributed Wind Energy in Idaho  

SciTech Connect

Project Objective: This project is a research and development program aimed at furthering distributed wind technology. In particular, this project addresses some of the barriers to distributed wind energy utilization in Idaho. Background: At its core, the technological challenge inherent in Wind Energy is the transformation of a highly variable form of energy to one which is compatible with the commercial power grid or another useful application. A major economic barrier to the success of distributed wind technology is the relatively high capital investment (and related long payback periods) associated with wind turbines. This project will carry out fundamental research and technology development to address both the technological and economic barriers. � Active drive train control holds the potential to improve the overall efficiency of a turbine system by allowing variable speed turbine operation while ensuring a tight control of generator shaft speed, thus greatly simplifying power conditioning. � Recent blade aerodynamic advancements have been focused on large, utility-scale wind turbine generators (WTGs) as opposed to smaller WTGs designed for distributed generation. Because of Reynolds Number considerations, blade designs do not scale well. Blades which are aerodynamically optimized for distributed-scale WTGs can potentially reduce the cost of electricity by increasing shaft-torque in a given wind speed. � Grid-connected electric generators typically operate at a fixed speed. If a generator were able to economically operate at multiple speeds, it could potentially convert more of the wind�s energy to electricity, thus reducing the cost of electricity. This research directly supports the stated goal of the Wind and Hydropower Technologies Program for Distributed Wind Energy Technology: By 2007, reduce the cost of electricity from distributed wind systems to 10 to 15 cents/kWh in Class 3 wind resources, the same level that is currently achievable in Class 5 winds.

Gardner, John; Ferguson, James; Ahmed-Zaid, Said; Johnson, Kathryn; Haynes, Todd; Bennett, Keith

2009-01-31T23:59:59.000Z

409

Observations of Edge Turbulence  

NLE Websites -- All DOE Office Websites (Extended Search)

Edge Turbulence Edge Turbulence near the X-point of Alcator C-Mod APS-2007 (1) J.L. Terry, S.J. Zweben*, B. LaBombard, I. Cziegler, O. Grulke + , D.P. Stotler* MIT - Plasma Science and Fusion Center *Princeton Plasma Physics Laboratory + MPI for Plasma Physics, EURATOM Assoc., Greifswald, Germany American Physical Society - Div. of Plasma Physics Orlando, FL Nov. 12 - Nov. 16, 2007 APS-2007 (2) Background and Motivation for "Xpt-region" View Strong edge turbulence has been observed in nearly all magnetic confinement devices. Desire predictive capability Most previous measurements made near outboard midplane where the turbulence has the following main features: - generation is ballooning-like (absent at inboard midplane, etc.) - filaments/blobs moves radially outward with some poloidal motion

410

ARM - Measurement - Atmospheric turbulence  

NLE Websites -- All DOE Office Websites (Extended Search)

turbulence turbulence ARM Data Discovery Browse Data Comments? We would love to hear from you! Send us a note below or call us at 1-888-ARM-DATA. Send Measurement : Atmospheric turbulence High frequency velocity fluctuations that lead to turbulent transport of momentum, heat, mositure, and passive scalars, and often expressed in terms of variances and covariances. Categories Atmospheric State, Surface Properties Instruments The above measurement is considered scientifically relevant for the following instruments. Refer to the datastream (netcdf) file headers of each instrument for a list of all available measurements, including those recorded for diagnostic or quality assurance purposes. ARM Instruments CO2FLX : Carbon Dioxide Flux Measurement Systems ECOR : Eddy Correlation Flux Measurement System

411

EIA: Wind  

U.S. Energy Information Administration (EIA)

Technical information and data on the wind energy industry from the U.S. Energy Information Administration (EIA).

412

Performance of twist-coupled blades on variable speed rotors  

DOE Green Energy (OSTI)

The load mitigation and energy capture characteristics of twist-coupled HAWT blades that are mounted on a variable speed rotor are investigated in this paper. These blades are designed to twist toward feather as they bend with pretwist set to achieve a desirable twist distribution at rated power. For this investigation, the ADAMS-WT software has been modified to include blade models with bending-twist coupling. Using twist-coupled and uncoupled models, the ADAMS software is exercised for steady wind environments to generate C{sub p} curves at a number of operating speeds to compare the efficiencies of the two models. The ADAMS software is also used to generate the response of a twist-coupled variable speed rotor to a spectrum of stochastic wind time series. This spectrum contains time series with two mean wind speeds at two turbulence levels. Power control is achieved by imposing a reactive torque on the low speed shaft proportional to the RPM squared with the coefficient specified so that the rotor operates at peak efficiency in the linear aerodynamic range, and by limiting the maximum RPM to take advantage of the stall controlled nature of the rotor. Fatigue calculations are done for the generated load histories using a range of material exponents that represent materials from welded steel to aluminum to composites, and results are compared with the damage computed for the rotor without twist-coupling. Results indicate that significant reductions in damage are achieved across the spectrum of applied wind loading without any degradation in power production.

Lobitz, D.W.; Veers, P.S.; Laino, D.J.

1999-12-07T23:59:59.000Z

413

A Brief Climatology of Vertical Wind Variability in the Troposphere and Stratosphere as Seen by the Poker Flat, Alaska, MST Radar  

Science Conference Proceedings (OSTI)

A statistical analysis of vertical air motion has been performed for data taken in the 3-20 km altitude range by the Poker Flat MST radar during the period September 1979-January 1982. The variability of vertical velocities is analyzed as a ...

G. D. Nastrom; K. S. Gage

1984-03-01T23:59:59.000Z

414

MHD Turbulence Revisited  

E-Print Network (OSTI)

Kraichnan (1965) proposed that MHD turbulence occurs as a result of collisions between oppositely directed Alfv\\'en wave packets. Recent work has generated some controversy over the nature of non linear couplings between colliding Alfv\\'en waves. We find that the resolution to much of the confusion lies in the existence of a new type of turbulence, intermediate turbulence, in which the cascade of energy in the inertial range exhibits properties intermediate between those of weak and strong turbulent cascades. Some properties of intermediate MHD turbulence are: (i) in common with weak turbulent cascades, wave packets belonging to the inertial range are long lived; (ii) however, components of the strain tensor are so large that, similar to the situation in strong turbulence, perturbation theory is not applicable; (iii) the breakdown of perturbation theory results from the divergence of neighboring field lines due to wave packets whose perturbations in velocity and magnetic fields are localized, but whose perturbations in displacement are not; (iv) 3--wave interactions dominate individual collisions between wave packets, but interactions of all orders $n\\geq 3$ make comparable contributions to the intermediate turbulent energy cascade; (v) successive collisions are correlated since wave packets are distorted as they follow diverging field lines; (vi) in common with the weak MHD cascade, there is no parallel cascade of energy, and the cascade to small perpendicular scales strengthens as it reaches higher wave numbers; (vii) For an appropriate weak excitation, there is a natural progression from a weak, through an intermediate, to a strong cascade.

P. Goldreich; S. Sridhar

1996-12-31T23:59:59.000Z

415

Wind shear climatology for large wind turbine generators  

DOE Green Energy (OSTI)

Climatological wind shear analyses relevant to the design and operation of multimegawatt wind turbines are provided. Insight is provided for relating the wind experienced by a rotating blade in a shear flow to the analysis results. A simple analysis of the wind experienced by a rotating blade for three types of wind shear profiles under steady-state conditions is presented in graphical form. Comparisons of the magnitude and frequency of the variations in 1) the wind sensed by a single blade element, 2) the sum, and 3) the difference of the winds sensed by opposite blade elements show strong sensitivity to profile shape. These three items represent forcing functions that can be related to 1) flatwise bending moment, 2) torque on the shaft, and 3) teeter angle. A computer model was constructed to simulate rotational sampling of 10-s sampled winds from a tall tower for three different types of large wind turbines. Time series produced by the model indicated that the forcing functions on a rotating blade vary according to the shear profile encountered during each revolution as opposed to a profile derived from average wind conditions, e.g., hourly average winds. An analysis scheme was developed to establish a climatology of wind shear profiles derived from 10-s sampled winds and hourly average winds measured over a one-year period at several levels on a tall tower. Because of the sensitivity of the forcing function variability to profile shape, the analyses performed and presented are in the form of joint frequency distributions of velocity differences of the the top-to-hub versus the hub-to-bottom portion of disks of rotation for the three turbine configurations.

Elliott, D.L.; Wendell, L.L.; Heflick, S.K.

1982-10-01T23:59:59.000Z

416

The Influence of Stratification and Nonlocal Turbulent Production on Estuarine Turbulence: An Assessment of Turbulence Closure with Field Observations  

Science Conference Proceedings (OSTI)

Field observations of turbulent kinetic energy (TKE), dissipation rate ?, and turbulent length scale demonstrate the impact of both density stratification and nonlocal turbulent production on turbulent momentum flux. The data were collected in a ...

Malcolm E. Scully; W. Rocky Geyer; John H. Trowbridge

2011-01-01T23:59:59.000Z

417

NREL: Transmission Grid Integration - Variability of Renewable...  

NLE Websites -- All DOE Office Websites (Extended Search)

as variable generation sources because their electricity production varies based on the availability of wind and sun. However, they are not the only source of variation in a...

418

THE INTERNAL-COLLISION-INDUCED MAGNETIC RECONNECTION AND TURBULENCE (ICMART) MODEL OF GAMMA-RAY BURSTS  

Science Conference Proceedings (OSTI)

The recent Fermi observation of GRB 080916C shows that the bright photosphere emission associated with a putative fireball is missing, which suggests that the central engine likely launches a Poynting-flux-dominated (PFD) outflow. We propose a model of gamma-ray burst (GRB) prompt emission in the PFD regime, namely, the Internal-Collision-induced MAgnetic Reconnection and Turbulence (ICMART) model. It is envisaged that the GRB central engine launches an intermittent, magnetically dominated wind, and that in the GRB emission region, the ejecta is still moderately magnetized (e.g., 1 {approx}lines entrained in the ejecta. At a certain point, the distortion of magnetic field configuration reaches the critical condition to allow fast reconnection seeds to occur, which induce relativistic MHD turbulence in the interaction regions. The turbulence further distorts field lines easing additional magnetic reconnections, resulting in a runway release of the stored magnetic field energy (an ICMART event). Particles are accelerated either directly in the reconnection zone, or stochastically in the turbulent regions, which radiate synchrotron photons that power the observed gamma rays. Each ICMART event corresponds to a broad pulse in the GRB light curve, and a GRB is composed of multiple ICMART events. This model retains the merits of IS and other models, but may overcome several difficulties/issues faced by the IS model (e.g., low efficiency, fast cooling, electron number excess, Amati/Yonetoku relation inconsistency, and missing bright photosphere). Within this model, the observed GRB variability timescales could have two components, one slow component associated with the central engine time history, and another fast component associated with relativistic magnetic turbulence in the emission region. The model predicts a decrease of gamma-ray polarization degree and E{sub p} in each ICMART event (broad pulse) during the prompt GRB phase, as well as a moderately magnetized external reverse shock. The model may be applied to the GRBs that have time-resolved, featureless Band-function spectra, such as GRB 080916C and most GRBs detected by Fermi LAT.

Zhang Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States); Yan Huirong [Kavli Institute of Astronomy and Astrophysics, Peking University, Beijing 100871 (China)

2011-01-10T23:59:59.000Z

419

Dependence of Wind Turbine Curves on Atmospheric Stability Regimes - An Analysis of a West Coast North American Tall Wind Farm  

DOE Green Energy (OSTI)

Tall wind turbines, with hub heights at 80 m or above, can extract large amounts of energy from the atmosphere because they are likely to encounter higher wind speeds, but they face challenges given the complex nature of wind flow in the boundary layer. Depending on whether the boundary layer is stable, convective or neutral, mean wind speed (U) and turbulence ({sigma}{sub U}) may vary greatly across the tall turbine swept area (40 m to 120 m). This variation can cause a single turbine to produce difference amounts of power during time periods of identical hub height wind speeds. The study examines the influence that atmospheric mixing or stability has on power output at a West Coast North American wind farm. They first examine the accuracy and applicability of two, relatively simple stability parameters, the wind shear-exponent, {alpha}, and the turbulence intensity, I{sub u}, against the physically-based, Obukhov length, L, to describe the wind speed and turbulence profiles in the rotor area. In general, the on-site stability parameters {alpha} and I{sub u} are in high agreement with the off-site, L stability scale parameter. Next, they divide the measurement period into five stability classes (strongly stable, stable, neutral, convective, and strongly convective) to discern stability-effects on power output. When only the mean wind speed profile is taken into account, the dependency of power output on boundary layer stability is only subtly apparent. When turbulence intensity I{sub u} is considered, the power generated for a given wind speed is twenty percent higher during strongly stable conditions than during strongly convective conditions as observed in the spring and summer seasons at this North American wind farm.

Wharton, S; Lundquist, J K; Sharp, J; Zulauf, M

2009-08-24T23:59:59.000Z

420

Nonlinear Control of a Wind Turbine Sven Creutz Thomsen  

E-Print Network (OSTI)

Nonlinear Control of a Wind Turbine Sven Creutz Thomsen Kongens Lyngby 2006 #12; Technical describes analysis of various nonlinear control methods for controlling a wind turbine. High speed wind Modeling and analysis 5 2 Model descriptions 7 2.1 Variable speed wind turbine

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Wind Blog  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

wind-blog Office of Energy Efficiency & Renewable wind-blog Office of Energy Efficiency & Renewable Energy Forrestal Building 1000 Independence Avenue, SW Washington, DC 20585 en Two Facilities, One Goal: Advancing America's Wind Industry http://energy.gov/eere/articles/two-facilities-one-goal-advancing-america-s-wind-industry wind-industry" class="title-link">Two Facilities, One Goal: Advancing America's Wind Industry

422

Self Consistent Models of the Solar Wind  

E-Print Network (OSTI)

The origins of the hot solar corona and the supersonically expanding solar wind are still the subject of much debate. This paper summarizes some of the essential ingredients of realistic and self-consistent models of solar wind acceleration. It also outlines the major issues in the recent debate over what physical processes dominate the mass, momentum, and energy balance in the accelerating wind. A key obstacle in the way of producing realistic simulations of the Sun-heliosphere system is the lack of a physically motivated way of specifying the coronal heating rate. Recent models that assume the energy comes from Alfven waves that are partially reflected, and then dissipated by magnetohydrodynamic turbulence, have been found to reproduce many of the observed features of the solar wind. This paper discusses results from these models, including detailed comparisons with measured plasma properties as a function of solar wind speed. Some suggestions are also given for future work that could answer the many remain...

Cranmer, Steven R

2010-01-01T23:59:59.000Z

423

Heat release effects on decaying homogeneous compressible turbulence  

E-Print Network (OSTI)

High Mach-number compressible flows with heat release are inherently more complicated than incompressible flows due to, among other reasons, the activation of the thermal energy mode. Such flow fields can experience significant fluctuations in density, temperature, viscosity, conductivity and specific heat, which affect velocity and pressure fluctuations. Furthermore, the flow field cannot be assumed to be dilatation-free in high Mach numbers and even in low Mach-number flows involving combustion, or in boundary layers on heated walls. The main issue in these high-speed and highly-compressible flows is the effect of thermal gradients and fluctuations on turbulence. The thermal field has various routes through which it affects flow structures of compressible turbulence. First, it has direct influence through pressure, which affects turbulence via pressure-strain correlation. The indirect effects of thermal fields on compressible turbulence are through the changes in flow properties. The high temperature gradients alter the transport coefficient and compressibility of the flow. The objective of this work is to answer the following questions: How do temperature fluctuations change the compressible flow structure and energetics? How does compressibility in the flow affect the non-linear pressure redistribution process? What is the main effect of spatial transport-coefficient variation? We perform direct numerical simulations (DNS) to answer the above questions. The investigations are categorized into four parts: 1) Turbulent energy cascade and kinetic-internal energy interactions under the influence of temperature fluctuations; 2) Return-to-isotropy of anisotropic turbulence under the influence of large temperature fluctuations; 3) The effect of turbulent Mach number and dilatation level on small-scale (velocity-gradient) dynamics; 4) The effect of variable transport-coefficients (viscosity and diffusivity) on cascade and dissipation processes of turbulence. The findings lead to a better understanding of temperature fluctuation effects on non-linear processes in compressible turbulence. This improved understanding is expected to provide direction for improving second-order closure models of compressible turbulence.

Lee, Kurn Chul

2008-05-01T23:59:59.000Z

424

Wind stress measurements from the QuikSCAT-SeaWinds scatterometer tandem mission and the impact on an ocean model  

E-Print Network (OSTI)

Wind stress measurements from the QuikSCAT-SeaWinds scatterometer tandem mission and the impact by the QuikSCAT-SeaWinds scatterometer tandem mission (April­October 2003) and their impact on ocean model simulation. The diurnal variability captured by twice-daily scatterometer wind from the tandem mission

Talley, Lynne D.

425

Turbine Inflow Characterization at the National Wind Technology Center  

Science Conference Proceedings (OSTI)

Utility-scale wind turbines operate in dynamic flows that can vary significantly over timescales from less than a second to several years. To better understand the inflow to utility-scale turbines, two inflow towers were installed and commissioned at the National Renewable Energy Laboratory's (NREL) National Wind Technology Center near Boulder, Colorado, in 2011. These towers are 135 m tall and instrumented with a combination of sonic anemometers, cup anemometers, wind vanes, and temperature measurements to characterize the inflow wind speed and direction, turbulence, stability and thermal stratification to two utility-scale turbines. Herein, we present variations in mean and turbulent wind parameters with height, atmospheric stability, and as a function of wind direction that could be important for turbine operation as well as persistence of turbine wakes. Wind speed, turbulence intensity, and dissipation are all factors that affect turbine performance. Our results show that these all vary with height across the rotor disk, demonstrating the importance of measuring atmospheric conditions that influence wind turbine performance at multiple heights in the rotor disk, rather than relying on extrapolation from lower levels.

Clifton, A.; Schreck, S.; Scott, G.; Kelley, N.; Lundquist, J. K.

2012-01-01T23:59:59.000Z

426

Turbine Inflow Characterization at the National Wind Technology Center: Preprint  

DOE Green Energy (OSTI)

Utility-scale wind turbines operate in dynamic flows that can vary significantly over timescales from less than a second to several years. To better understand the inflow to utility-scale turbines, two inflow towers were installed and commissioned at the National Renewable Energy Laboratory's (NREL) National Wind Technology Center near Boulder, Colorado, in 2011. These towers are 135 m tall and instrumented with a combination of sonic anemometers, cup anemometers, wind vanes, and temperature measurements to characterize the inflow wind speed and direction, turbulence, stability and thermal stratification to two utility-scale turbines. Herein, we present variations in mean and turbulent wind parameters with height, atmospheric stability, and as a function of wind direction that could be important for turbine operation as well as persistence of turbine wakes. Wind speed, turbulence intensity, and dissipation are all factors that affect turbine performance. Our results shown that these all vary with height across the rotor disk, demonstrating the importance of measuring atmospheric conditions that influence wind turbine performance at multiple heights in the rotor disk, rather than relying on extrapolation from lower levels.

Clifton, A.; Schreck, S.; Scott, G.; Kelley, N.; Lundquist, J.

2012-01-01T23:59:59.000Z

427

Fallacies of the Enthalpy Transfer Coefficient over the Ocean in High Winds  

Science Conference Proceedings (OSTI)

Mesoscale and large-scale atmospheric models use a bulk surface flux algorithm to compute the turbulent flux boundary conditions at the bottom of the atmosphere from modeled mean meteorological quantities such as wind speed, temperature, and ...

Edgar L Andreas

2011-07-01T23:59:59.000Z

428

A Phenomenological Model for Wind Speed and Shear Stress Profiles in Vegetation Cover Layers  

Science Conference Proceedings (OSTI)

A phenomenological model for the mean wind speed and Reynolds shear stress profiles with height in a vegetation cover layer is derived from forms suggested by truncation of the equations of turbulent fluid motion at second order in fluctuating ...

F. A. Albini

1981-11-01T23:59:59.000Z

429

Use of a Large Crane for Wind and Tracer Profiles in an Urban Setting  

Science Conference Proceedings (OSTI)

Although measured vertical profiles of wind, turbulence, and tracer concentrations are critical for understanding the urban boundary layer, it is problematic to field a sounding system or a tall structure to support anemometers in a densely ...

Frank J. Gouveia; Martin J. Leach; Joseph H. Shinn; William E. Ralph

2007-10-01T23:59:59.000Z

430

The Variational Assimilation Method for the Retrieval of Humidity Profiles with the Wind-Profiling Radar  

Science Conference Proceedings (OSTI)

Recently, a humidity estimation technique was developed by using the turbulence echo characteristics detected with a wind-profiling radar. This study is concerned with improvement of the retrieval algorithm for delineating a humidity profile from ...

Jun-ichi Furumoto; Shingo Imura; Toshitaka Tsuda; Hiromu Seko; Tadashi Tsuyuki; Kazuo Saito

2007-09-01T23:59:59.000Z

431

First- and Second-Order Closure Models for Wind in a Plant Canopy  

Science Conference Proceedings (OSTI)

Katul and Chang recently compared the performance of two second-order closure models with observations of wind and turbulence in the Duke Forest canopy, noting that such models “alleviate some of the theoretical objections to first-order closure.”...

J. D. Jean-Paul Pinard; John D. Wilson

2001-10-01T23:59:59.000Z

432

A Numerical Model Study of Nocturnal Drainage Flows with Strong Wind and Temperature Gradients  

Science Conference Proceedings (OSTI)

A second-moment turbulence-closure model described in Yamada and Bunker is used to simulate nocturnal drainage flows observed during the 1984 ASCOT field expedition in Brush Creek, Colorado. In order to simulate the observed strong wind ...

T. Yamada; S. Bunker

1989-07-01T23:59:59.000Z

433

E – ? model of spray-laden near-sea atmospheric layer in high wind conditions  

Science Conference Proceedings (OSTI)

In-depth understanding and accurate modelling of the interaction between ocean spray and a turbulent flow under high-wind conditions is essential for improving intensity forecasts of hurricanes and severe storms. Here we consider the E – ? closure ...

Yevgenii Rastigejev; Sergey A. Suslov

434

Enhancement of Crosswind Pollutant Dispersion by Steadily Veering Winds in Sea Breezes  

Science Conference Proceedings (OSTI)

An estimate is given of the relative importance of wind veering and turbulent diffusion in the mean horizontal spread of pollutant plumes in the atmosphere. Documented veering rates in sea breezes are used to illustrate the effect, and it is ...

D. G. Steyn; M. Segal

1990-05-01T23:59:59.000Z

435

Uncertainty of Boundary Layer Heat Budgets Computed from Wind Profiler—RASS Networks  

Science Conference Proceedings (OSTI)

Uncertainties in the evaluation of the atmospheric heat budget, in which the turbulent heat flux divergence term is calculated as a residual, are investigated for a triangular array of 915-MHz wind profilers—radio acoustic sounding systems (RASS) ...

Markus Furger; C. David Whiteman; James M. Wilczak

1995-03-01T23:59:59.000Z

436

Effects of Wind Field Inhomogeneities on Doppler Beam Swinging Revealed by an Imaging Radar  

Science Conference Proceedings (OSTI)

In this work, the accuracy of the Doppler beam-swinging (DBS) technique for wind measurements is studied using an imaging radar—the turbulent eddy profiler (TEP) developed by the University of Massachusetts, with data collected in summer 2003. ...

B. L. Cheong; R. D. Palmer; T-Y. Yu; K-F. Yang; M. W. Hoffman; S. J. Frasier; F. J. Lopez-Dekker

2008-08-01T23:59:59.000Z

437

Abstract--Pitch angle control is the most common means for adjusting the aerodynamic torque of the wind turbine when wind  

E-Print Network (OSTI)

of the wind turbine when wind speed is above rated speed and various controlling variables may be chosen Terms--Blade aerodynamic, Fatigue load, Fuzzy logic control, Pitch angle, Wind turbine I. INTRODUCTION of 40 GW. Pitch-adjusting variable-speed wind turbines have become the dominating type of yearly

Hansen, René Rydhof

438

Wind Tunnel Aeroacoustic Tests of Six Airfoils for Use on Small Wind Turbines: Preprint  

DOE Green Energy (OSTI)

Aeroacoustic tests of seven airfoils were performed in an open jet anechoic wind tunnel. Six of the airfoils are candidates for use on small wind turbines operating at low Reynolds number. One airfoil was tested for comparison to benchmark data. Tests were conducted with and without boundary layer tripping. In some cases a turbulence grid was placed upstream in the test section to investigate inflow turbulence noise. An array of 48 microphones was used to locate noise sources and separate airfoil noise from extraneous tunnel noise. Trailing edge noise was dominant for all airfoils in clean tunnel flow. With the boundary layer untripped, several airfoils exhibited pure tones that disappeared after proper tripping was applied. In the presence of inflow turbulence, leading edge noise was dominant for all airfoils.

Migliore, P.; Oerlemans, S.

2003-12-01T23:59:59.000Z

439

Standards for Municipal Small Wind Regulations and Small Wind...  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Standards for Municipal Small Wind Regulations and Small Wind Model Wind Ordinance Standards for Municipal Small Wind Regulations and Small Wind Model Wind Ordinance Eligibility...

440

Operational behavior of a double-fed permanent magnet generator for wind turbines  

E-Print Network (OSTI)

Greater efficiency in wind turbine systems is achieved by allowing the rotor to change its rate of rotation as the wind speed changes. The wind turbine system is decoupled from the utility grid and a variable speed operation ...

Reddy, Sivananda Kumjula

2005-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

Feasibility analysis of coordinated offshore wind project development in the U.S.  

E-Print Network (OSTI)

Wind energy is one of the cleanest and most available resources in the world, and advancements in wind technology are making it more cost effective. Though wind power is rapidly developing in many regions, its variable ...

Zhang, Mimi Q

2008-01-01T23:59:59.000Z

442

Energy Basics: Wind Turbines  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

Energy Basics Renewable Energy Printable Version Share this resource Biomass Geothermal Hydrogen Hydropower Ocean Solar Wind Wind Turbines Wind Resources Wind Turbines...

443

A Theory of Baroclinic Turbulence  

Science Conference Proceedings (OSTI)

Understanding the physical mechanism maintaining fluid turbulence remains a fundamental theoretical problem. The two-layer model is an analytically and computationally simple system in which the dynamics of turbulence can be conveniently studied; ...

Brian F. Farrell; Petros J. Ioannou

2009-08-01T23:59:59.000Z

444

Statistical Predictability of Decaying Turbulence  

Science Conference Proceedings (OSTI)

We use statistical models of turbulence with “eddy damping” (EDQNM) in order to study the problem of predictability of freely evolving two- and three-dimensional isotropic turbulent flows.

Olivier Métais; Marcel Lesieur

1986-05-01T23:59:59.000Z

445

Supersaturation Intermittency in Turbulent Clouds  

Science Conference Proceedings (OSTI)

It is hypothesized that bursts of high supersaturation are produced in turbulent, convective clouds through interactions between cloud droplets and the small-scale structure of atmospheric turbulence. This hypothesis is based on the observation ...

Raymond A. Shaw

2000-10-01T23:59:59.000Z

446

The Decay of Convective Turbulence  

Science Conference Proceedings (OSTI)

Using simulations with a large-eddy model we have studied the decay of convective turbulence in the atmospheric boundary layer when the upward surface sensible heat flux is suddenly stopped. The decay of turbulent kinetic energy and temperature ...

F. T. M. Nieuwstadt; R. A. Brost

1986-03-01T23:59:59.000Z

447

On Sub-ENSO Variability  

Science Conference Proceedings (OSTI)

Multichannel singular spectrum analysis (MSSA) of surface zonal wind, sea surface temperature (SST), 20° isotherm depth, and surface zonal current observations (between 1990 and 2004) identifies three coupled ocean–atmosphere modes of variability ...

Noel S. Keenlyside; Mojib Latif; Anke Dürkop

2007-07-01T23:59:59.000Z

448

Risř–I–1206(EN) Wind Power Meteorology  

E-Print Network (OSTI)

Abstract Wind power meteorology has evolved as an applied science, firmly founded on boundary-layer meteorology, but with strong links to climatology and geography. It concerns itself with three main areas: siting of wind turbines, regional wind resource assessment, and short-term prediction of the wind resource. The history, status and perspectives of wind power meteorology are presented, with emphasis on physical considerations and on its practical application. Following a global view of the wind resource, the elements of boundary layer meteorology which are most important for wind energy are reviewed: wind profiles and shear, turbulence and gust, and extreme winds. The data used in wind power meteorology stem mainly from three sources: onsite wind measurements, the synoptic networks, and the re-analysis projects. Wind climate analysis, wind resource estimation and siting further require a detailed description of the topography of the terrain – with respect to the roughness of the surface, near-by obstacles, and orographical features. Finally, the meteorological models used for estimation and prediction of the wind are described; their classification,

Erik L. Petersen; Niels G. Mortensen; Lars L; Jřrgen Hřjstrup; Helmut P. Frank

1997-01-01T23:59:59.000Z

449

Predicting aerodynamic characteristic of typical wind turbine airfoils using CFD  

DOE Green Energy (OSTI)

An investigation was conducted into the capabilities and accuracy of a representative computational fluid dynamics code to predict the flow field and aerodynamic characteristics of typical wind-turbine airfoils. Comparisons of the computed pressure and aerodynamic coefficients were made with wind tunnel data. This work highlights two areas in CFD that require further investigation and development in order to enable accurate numerical simulations of flow about current generation wind-turbine airfoils: transition prediction and turbulence modeling. The results show that the laminar-to turbulent transition point must be modeled correctly to get accurate simulations for attached flow. Calculations also show that the standard turbulence model used in most commercial CFD codes, the k-e model, is not appropriate at angles of attack with flow separation. 14 refs., 28 figs., 4 tabs.

Wolfe, W.P. [Sandia National Labs., Albuquerque, NM (United States); Ochs, S.S. [Iowa State Univ., Ames, IA (United States). Aerospace Engineering Dept.

1997-09-01T23:59:59.000Z

450

NREL: Energy Analysis - Wind Technology Analysis  

NLE Websites -- All DOE Office Websites (Extended Search)

Wind and Hydropower Technology Analysis Wind and Hydropower Technology Analysis Wind and hydropower analysis supports advanced technologies that convert more of the nation's wind into electricity. Grid Operational Impact Analysis The wind program will address the variable, normally uncontrollable nature of wind power plant output, and the additional needs that its operation imposes on the overall grid. At present, the generation and transmission operational impacts that occur due to wind variability are not well quantified. This research will include efforts to quantify and fairly allocate impacts in both an engineering and cost sense. Methods of analysis are at an early stage of development. Without realistic analysis and cost allocation, utilities tend to overestimate imposed operational costs,

451

Revealing the Winds Under the Rain. Part I. Passive Microwave Rain Retrievals Using a New, Observations-Based, Parameterization of Sub-Satellite Rain Variability and Intensity: Algorithm Description.  

Science Conference Proceedings (OSTI)

Scatterometer ocean surface winds have been providing very valuable information to researchers and operational weather forecasters for over ten years. However, the scatterometer wind retrievals are compromised when rain is present. Merely flagging ...

S. M. Hristova-Veleva; P. S. Callahan; R. S. Dunbar; B. W. Stiles; S. H. Yueh; J. N. Huddleston; S. V. Hsiao; G. Neumann; M. H. Freilich; B. A. Vanhoff; R. W. Gaston; E. Rodriguez; D. E. Weissman

452

Adaptive Control of a Utility-Scale Wind Turbine Operating in Region 3  

Science Conference Proceedings (OSTI)

Many challenges exist for the efficient and safe operation of wind turbines due to the difficulty in creating accurate models of their dynamic characteristics and the turbulent conditions in which they operate. A promising new area of wind turbine research is the application of adaptive control techniques, which are well suited to problems where the plant model is not well known and the plant operating conditions are unpredictable. In this paper, we design an adaptive collective pitch controller for a high-fidelity simulation of a utility scale, variable-speed horizontal axis wind turbine operating in Region 3. The objective of the adaptive pitch controller is to regulate generator speed and reject step disturbances, which model the uniform wind disturbance across the wind turbine rotor. The control objective is accomplished by collectively pitching the turbine blades. To improve controller performance, we use an extension of the Direct Model Reference Adaptive Control (DMRAC) approach to regulate turbine rotational speed and to accommodate step disturbances. The turbine simulation models the Controls Advanced Research Turbine (CART) of the National Renewable Energy Laboratory in Golden, Colorado. The CART is a utility-scale wind turbine that has a well-developed and extensively verified simulator. The adaptive collective pitch controller for Region 3 was compared in simulations with a baseline classical Proportional Integrator (PI) collective pitch controller. In the simulations, the adaptive pitch controller showed improved generator speed regulation in Region 3 when compared with the baseline PI pitch controller. The adaptive controller demonstrated robustness to modeling errors and changes in system parameters.

Frost, S. A.; Balas, M. J.; Wright, A. D.

2009-01-01T23:59:59.000Z

453

NREL: Wind Research - Large Wind Turbine Research  

NLE Websites -- All DOE Office Websites (Extended Search)

Wind Research Search More Search Options Site Map Printable Version Large Wind Turbine Research NREL's utility scale wind system research addresses performance and...

454

VARIABLE TIME DELAY MEANS  

DOE Patents (OSTI)

An electrically variable time delay line is described which may be readily controlled simuitaneously with variable impedance matching means coupied thereto such that reflections are prevented. Broadly, the delay line includes a signal winding about a magnetic core whose permeability is electrically variable. Inasmuch as the inductance of the line varies directly with the permeability, the time delay and characteristic impedance of the line both vary as the square root of the permeability. Consequently, impedance matching means may be varied similariy and simultaneously w:th the electrically variable permeability to match the line impedance over the entire range of time delay whereby reflections are prevented.

Clemensen, R.E.

1959-11-01T23:59:59.000Z

455

Thermocline Variability in Different Dynamic Regions  

Science Conference Proceedings (OSTI)

The response of thermocline circulation to a variable wind forcing is investigated with quasigeostrophic models. The physical mechanism responsible for the different variability features in various dynamic regions has been highlighted. Special ...

Zhengye Liu

1996-08-01T23:59:59.000Z

456

A non-hybrid method for the PDF equations of turbulent flows on unstructured grids  

Science Conference Proceedings (OSTI)

In probability density function (PDF) methods of turbulent flows, the joint PDF of several flow variables is computed by numerically integrating a system of stochastic differential equations for Lagrangian particles. A set of parallel algorithms is proposed ... Keywords: Finite element method, Langevin equation, Monte-Carlo method, Particle tracking, Particle-in-cell method, Probability density function method, Scalar dispersion, Turbulent flow, Unstructured grids

J. Bakosi; P. Franzese; Z. Boybeyi

2008-05-01T23:59:59.000Z

457

Dissipation and Heating in Supersonic Hydrodynamic and MHD Turbulence  

E-Print Network (OSTI)

We study energy dissipation and heating by supersonic MHD turbulence in molecular clouds using Athena, a new higher-order Godunov code. We analyze the dependence of the saturation amplitude, energy dissipation characteristics, power spectra, sonic scaling, and indicators of intermittency in the turbulence on factors such as the magnetic field strength, driving scale, energy injection rate, and numerical resolution. While convergence in the energies is reached at moderate resolutions, we find that the power spectra require much higher resolutions that are difficult to obtain. In a 1024^3 hydro run, we find a power law relationship between the velocity dispersion and the spatial scale on which it is measured, while for an MHD run at the same resolution we find no such power law. The time-variability and temperature intermittency in the turbulence both show a dependence on the driving scale, indicating that numerically driving turbulence by an arbitrary mechanism may not allow a realistic representation of these...

Lemaster, M Nicole

2008-01-01T23:59:59.000Z

458

Wind Turbines  

Energy.gov (U.S. Department of Energy (DOE))

Although all wind turbines operate on similar principles, several varieties are in use today. These include horizontal axis turbines and vertical axis turbines.

459

A simulation-based planning system for wind turbine construction  

Science Conference Proceedings (OSTI)

Wind turbine construction is a challenging undertaking due to the need to lift heavy loads to high locations in conditions of high and variable wind speeds. These conditions create great risks to contractors during the turbine assembly process. This ...

Dina Atef; Hesham Osman; Moheeb Ibrahim; Khaled Nassar

2010-12-01T23:59:59.000Z

460

Buoy-Calibrated Winds over the Gulf of Mexico  

Science Conference Proceedings (OSTI)

The large variability of the Gulf of Mexico wind field indicates that high-resolution wind data will be required to represent the weather systems affecting ocean circulation. This report presents methods and results of the calculation of a ...

Robert C. Rhodes; J. Dana Thompson; Alan J. Wallcraft

1989-08-01T23:59:59.000Z

Note: This page contains sample records for the topic "turbulence wind variability" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


461

Beyond the Betz Theory - Blockage, Wake Mixing and Turbulence  

E-Print Network (OSTI)

Recent analytical models concerning the limiting efficiency of marine hydrokinetic (MHK) devices are reviewed with an emphasis on the significance of blockages (of local as well as global flow passages) and wake mixing. Also discussed is the efficiency of power generation from fully developed turbulent open channel flows. These issues are primarily concerned with the design/optimization of tidal turbine arrays; however, some of them are relevant to wind turbines as well.

Nishino, Takafumi

2013-01-01T23:59:59.000Z

462

Western Wind Strategy: Addressing Critical Issues for Wind Deployment  

DOE Green Energy (OSTI)

The goal of the Western Wind Strategy project was to help remove critical barriers to wind development in the Western Interconnection. The four stated objectives of this project were to: (1) identify the barriers, particularly barriers to the operational integration of renewables and barriers identified by load-serving entities (LSEs) that will be buying wind generation, (2) communicate the barriers to state officials, (3) create a collaborative process to address those barriers with the Western states, utilities and the renewable industry, and (4) provide a role model for other regions. The project has been on the forefront of identifying and informing state policy makers and utility regulators of critical issues related to wind energy and the integration of variable generation. The project has been a critical component in the efforts of states to push forward important reforms and innovations that will enable states to meet their renewable energy goals and lower the cost to consumers of integrating variable generation.

Douglas Larson; Thomas Carr

2012-03-30T23:59:59.000Z

463

Origins of Aircraft-Damaging Clear-Air Turbulence during the 9 December 1992 Colorado Downslope Windstorm: Numerical Simulations and Comparison with Observations  

Science Conference Proceedings (OSTI)

Results from numerical simulations of the Colorado Front Range downslope windstorm of 9 December 1992 are presented. Although this case was not characterized by severe surface winds, the event caused extreme clear-air turbulence (CAT) aloft, as ...

Terry L. Clark; William D. Hall; Robert M. Kerr; Don Middleton; Larry Radke; F. Martin Ralph; Paul J. Neiman; David Levinson

2000-04-01T23:59:59.000Z

464

High-Resolution In Situ Profiling through the Stable Boundary Layer: Examination of the SBL Top in Terms of Minimum Shear, Maximum Stratification, and Turbulence Decrease  

Science Conference Proceedings (OSTI)

Some 50 separate high-resolution profiles of small-scale turbulence defined by the energy dissipation rate (?), horizontal wind speed, and temperature from near the surface, through the nighttime stable boundary layer (SBL), and well into the ...

B. B. Balsley; R. G. Frehlich; M. L. Jensen; Y. Meillier

2006-04-01T23:59:59.000Z

465

NREL: Wind Research - Abundant Renewable Energy's ARE 442 Wind Turbine  

NLE Websites -- All DOE Office Websites (Extended Search)

Abundant Renewable Energy's ARE 442 Wind Turbine Testing and Results Abundant Renewable Energy's ARE 442 Wind Turbine Testing and Results Get the Adobe Flash Player to see this video. A video of Abundant Renewable Energy's ARE 442 wind turbine. Text Version As part of the National Renewable Energy Laboratory and U.S. Department of Energy (NREL/DOE) Independent Testing project, NREL tested Abundant Renewable Energy's ARE 442 turbine at the National Wind Technology Center (NWTC). The ARE 442 is a 10-kilowatt (kW), three-bladed, horizontal-axis upwind small wind turbine. It has a hub height of 30.9 meters and a rotor diameter of 7.2 meters. The turbine has a single-phase permanent-magnet generator that operates at variable voltages up to 410 volts AC. Testing Summary The summary of the tests is below with the final reports.

466

Wind Powering America: Wind Events  

Wind Powering America (EERE)

calendar.asp Lists upcoming wind calendar.asp Lists upcoming wind power-related events. en-us julie.jones@nrel.gov (Julie Jones) http://www.windpoweringamerica.gov/images/wpa_logo_sm.jpg Wind Powering America: Wind Events http://www.windpoweringamerica.gov/calendar.asp Pennsylvania Wind for Schools Educator Workshop https://www.regonline.com/builder/site/Default.aspx?EventID=1352684 http://www.windpoweringamerica.gov/filter_detail.asp?itemid=4068 Wed, 4 Dec 2013 00:00:00 MST 2014 Joint Action Workshop http://www.windpoweringamerica.gov/filter_detail.asp?itemid=3996 http://www.windpoweringamerica.gov/filter_detail.asp?itemid=3996 Mon, 21 Oct 2013 00:00:00 MST AWEA Wind Project Operations and Maintenance and Safety Seminar http://www.windpoweringamerica.gov/filter_detail.asp?itemid=4009 http://www.windpoweringamerica.gov/filter_detail.asp?itemid=4009 Mon, 21

467

Research on Control System of High Power DFIG Wind Power System  

Science Conference Proceedings (OSTI)

Compared with constant speed constant frequency wind turbine, variable speed constant frequency wind turbine has many advantages: higher efficiency of wind energy converting to electric power, absorbing gust energy, smoothly cutting into the network ... Keywords: wind power, DFIG, high power, LQR, variable speed constant frequency, constant power control

Li Jianlin; Xu Honghua

2008-12-01T23:59:59.000Z

468

Effects of Variable Droplet Growth Histories on Droplet Size Distributions. Part I: Theory  

Science Conference Proceedings (OSTI)

A theoretical framework is developed that permits estimation of the effects of fluctuating supersaturation on the development of cloud droplet size spectra. The studies focus on the role of turbulent fluctuations in vertical wind and in the ...

William A. Cooper

1989-05-01T23:59:59.000Z

469

Causality detection and turbulence in fusion plasmas  

E-Print Network (OSTI)

This work explores the potential of an information-theoretical causality detection method for unraveling the relation between fluctuating variables in complex nonlinear systems. The method is tested on some simple though nonlinear models, and guidelines for the choice of analysis parameters are established. Then, measurements from magnetically confined fusion plasmas are analyzed. The selected data bear relevance to the all-important spontaneous confinement transitions often observed in fusion plasmas, fundamental for the design of an economically attractive fusion reactor. It is shown how the present method is capable of clarifying the interaction between fluctuating quantities such as the turbulence amplitude, turbulent flux, and Zonal Flow amplitude, and uncovers several interactions that were missed by traditional methods.

van Milligen, B Ph; Ramisch, M; Estrada, T; Hidalgo, C; Alonso, A

2013-01-01T23:59:59.000Z

470

Bias Correction and Bayesian Model Averaging for Ensemble Forecasts of Surface Wind Direction  

Science Conference Proceedings (OSTI)

Wind direction is an angular variable, as opposed to weather quantities such as temperature, quantitative precipitation, or wind speed, which are linear variables. Consequently, traditional model output statistics and ensemble postprocessing ...

Le Bao; Tilmann Gneiting; Eric P. Grimit; Peter Guttorp; Adrian E. Raftery

2010-05-01T23:59:59.000Z

471

Definition of a 5-MW Reference Wind Turbine for Offshore System Development  

SciTech Connect

This report describes a three-bladed, upwind, variable-speed, variable blade-pitch-to-feather-controlled multimegawatt wind turbine model developed by NREL to support concept studies aimed at assessing offshore wind technology.

Jonkman, J.; Butterfield, S.; Musial, W.; Scott, G.

2009-02-01T23:59:59.000Z

472

Extreme Winds and Wind Effects on Structures  

Science Conference Proceedings (OSTI)

Extreme Winds and Wind Effects on Structures. Description/Summary: The Building and Fire Research Laboratory has an ...

2010-10-04T23:59:59.000Z

473

Mesoscale and Large-Eddy Simulations for Wind Energy  

Science Conference Proceedings (OSTI)

Operational wind power forecasting, turbine micrositing, and turbine design require high-resolution simulations of atmospheric flow over complex terrain. The use of both Reynolds-Averaged Navier Stokes (RANS) and large-eddy (LES) simulations is explored for wind energy applications using the Weather Research and Forecasting (WRF) model. To adequately resolve terrain and turbulence in the atmospheric boundary layer, grid nesting is used to refine the grid from mesoscale to finer scales. This paper examines the performance of the grid nesting configuration, turbulence closures, and resolution (up to as fine as 100 m horizontal spacing) for simulations of synoptically and locally driven wind ramping events at a West Coast North American wind farm. Interestingly, little improvement is found when using higher resolution simulations or better resolved turbulence closures in comparison to observation data available for this particular site. This is true for week-long simulations as well, where finer resolution runs show only small changes in the distribution of wind speeds or turbulence intensities. It appears that the relatively simple topography of this site is adequately resolved by all model grids (even as coarse as 2.7 km) so that all resolutions are able to model the physics at similar accuracy. The accuracy of the results is shown in this paper to be more dependent on the parameterization of the land-surface characteristics such as soil moisture rather than on grid resolution.

Marjanovic, N

2011-02-22T23:59:59.000Z

474

Wind Energy Leasing Handbook  

E-Print Network (OSTI)

Wind Energy Leasing Handbook Wind Energy Leasing Handbook E-1033 Oklahoma Cooperative Extension?..................................................................................................................... 31 What do wind developers consider in locating wind energy projects?............................................................................................ 37 How do companies and individuals invest in wind energy projects?....................................................................

Balasundaram, Balabhaskar "Baski"

475

Toward a Better Determination of Turbulent Air–Sea Fluxes from Several Experiments  

Science Conference Proceedings (OSTI)

An accurate determination of turbulent exchanges between the ocean and the atmosphere is a prerequisite to identify and assess the mechanisms of interaction that control part of the variability in the two media over a wide range of spatial and ...

A. Weill; L. Eymard; G. Caniaux; D. Hauser; S. Planton; H. Dupuis; A. Brut; C. Guerin; P. Nacass; A. Butet; S. Cloché; R. Pedreros; P. Durand; D. Bourras; H. Giordani; G. Lachaud; G. Bouhours

2003-02-01T23:59:59.000Z

476

Near-Surface Characteristics of the Turbulence Structure during a Mountain-Wave Event  

Science Conference Proceedings (OSTI)

A case study of mountain-wave-induced turbulence observed during the Terrain-Induced Rotor Experiment (T-REX) in Owens Valley, California, is presented. During this case study, large spatial and temporal variability in aerosol backscatter ...

Željko Ve?enaj; Stephan F. J. De Wekker; Vanda Grubiši?

2011-05-01T23:59:59.000Z

477

Microstructure Observations of Turbulent Mixing in a Partially Mixed Estuary. Part I: Dissipation Rate  

Science Conference Proceedings (OSTI)

Variations of turbulent mixing in the water column and in the benthic boundary layer were observed with a microstructure profiler in the Hudson River estuary during two cruises in summer and fall of 1995. Variability patterns of stratification, ...

Hartmut Peters; Reinoud Bokhorst

2000-06-01T23:59:59.000Z

478

Estimating Averaging Times for Point and Path-Averaged Measurements of Turbulence Spectra  

Science Conference Proceedings (OSTI)

Uncertainty over how long to average turbulence variables to achieve some desired level of statistical stability is a common concern in boundary-layer meteorology. Several models exist that predict averaging times for measurements of variances ...

Edgar L. Andreas

1988-03-01T23:59:59.000Z

479

Characterization of Turbulent Latent and Sensible Heat Flux Exchange between the Atmosphere and Ocean in MERRA  

Science Conference Proceedings (OSTI)

Turbulent fluxes of heat and moisture across the atmosphere–ocean interface are fundamental components of the earth’s energy and water balance. Characterizing both the spatiotemporal variability and the fidelity of these exchanges of heat and ...

J. Brent Roberts; Franklin R. Robertson; Carol A. Clayson; Michael G. Bosilovich

2012-02-01T23:59:59.000Z

480

Synoptic and local influences on boundary layer processes, with an application to California wind power  

E-Print Network (OSTI)

wind climate and variability. Site design and operation, as well as market integration mechanisms and energy policy

Mansbach, David K

2010-01-01T23:59:59.000Z

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481

Wind Powering America: New England Wind Forum  

Wind Powering America (EERE)

About the New England Wind Forum About the New England Wind Forum New England Wind Energy Education Project Historic Wind Development in New England State Activities Projects in New England Building Wind Energy in New England Wind Resource Wind Power Technology Economics Markets Siting Policy Technical Challenges Issues Small Wind Large Wind Newsletter Perspectives Events Quick Links to States CT MA ME NH RI VT Bookmark and Share The New England Wind Forum was conceived in 2005 as a platform to provide a single, comprehensive and objective source of up-to