skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Influence of street setbacks on solar reflection and air cooling by reflective streets in urban canyons

Authors:
; ; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1417098
Grant/Contract Number:
AC02-05CH11231
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Solar Energy
Additional Journal Information:
Journal Volume: 144; Journal Issue: C; Related Information: CHORUS Timestamp: 2018-01-16 12:45:23; Journal ID: ISSN 0038-092X
Publisher:
Elsevier
Country of Publication:
United States
Language:
English

Citation Formats

Rosado, Pablo J., Ban-Weiss, George, Mohegh, Arash, and Levinson, Ronnen M. Influence of street setbacks on solar reflection and air cooling by reflective streets in urban canyons. United States: N. p., 2017. Web. doi:10.1016/j.solener.2016.12.026.
Rosado, Pablo J., Ban-Weiss, George, Mohegh, Arash, & Levinson, Ronnen M. Influence of street setbacks on solar reflection and air cooling by reflective streets in urban canyons. United States. doi:10.1016/j.solener.2016.12.026.
Rosado, Pablo J., Ban-Weiss, George, Mohegh, Arash, and Levinson, Ronnen M. Wed . "Influence of street setbacks on solar reflection and air cooling by reflective streets in urban canyons". United States. doi:10.1016/j.solener.2016.12.026.
@article{osti_1417098,
title = {Influence of street setbacks on solar reflection and air cooling by reflective streets in urban canyons},
author = {Rosado, Pablo J. and Ban-Weiss, George and Mohegh, Arash and Levinson, Ronnen M.},
abstractNote = {},
doi = {10.1016/j.solener.2016.12.026},
journal = {Solar Energy},
number = C,
volume = 144,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.solener.2016.12.026

Citation Metrics:
Cited by: 2works
Citation information provided by
Web of Science

Save / Share:
  • The applicability of four simple dispersion mathematical models, namely APRAC, GZE, CALINE4, and PWILG were assessed by comparing the predicted CO and NO{sub x} concentrations with the measured values in street canyons in Guangzhou. These simple models were comparatively accurate in predicting maximum ground concentration. The accuracy of CO prediction was much influenced by the assumption of vehicular composition. The uncertainty of emission sources other than vehicle emissions was an important error source in predicting NO{sub x} concentrations.
  • Steady state mean concentrations of tracer gas were measured in a 400:1 scale model of an idealized city with variable geometry placed within a wind tunnel at various orientations to the mean flow for a free stream velocity of 6.8 ft/sec. The tracer gas was released from two parallel line sources to simulate lanes of traffic in an effort to quantify the persistence of pollution as well as the mean values realized at street levels. An aerodynamically rough turbulent boundary layer of neutral thermal stratification was employed to simulate the atmosphere. Velues of concentration measured in the model city weremore » converted to prototype concentrations in ppM and compared to National Ambient Air Quality Standards. It was shown that single isolated structures may cause favorable mixing of pollution downwind but very high concentrations exist in the immediate leeward vicinity of the building. Two favorable geometrics for city blocks tested were found to reduce pedestrian exposure to pollution both near heavy traffic congestion and downwind. It was concluded that the pollutant dilution was controlled by the mean flow rather than by turbulent diffusion and that the lateral spread of the plume was slight as one proceeded downwind of the line source. The combination of favorable geometry and higher dilution velocities may bring pollution levels down to existing Air Quality Standards. The body of information presented in this paper should interest city planners and air quality monitoring personnel, as well as those researchers attempting to study and model flow in city street canyons. It provides order of magnitude estimates on pedestrian and office worker exposure to pollutants under a wide range of conditions.« less
  • Three computational fluid dynamics (CFD) methods with different levels of flow-physics modelling are comprehensively evaluated against high-spatial-resolution wind-tunnel velocity data from step-down street canyons (i.e., a short building downwind of a tall building). The first method is a semi-empirical fast-response approach using the Quick Urban Industrial Complex (QUIC-URB) model. The second method solves the Reynolds-averaged Navier–Stokes (RANS) equations, and the third one utilizes a fully-coupled fluid-structure interaction large-eddy simulation (LES) model with a grid-turbulence inflow generator. Unlike typical point-by-point evaluation comparisons, here the entire two-dimensional wind-tunnel dataset is used to evaluate the dynamics of dominant flow topological features in themore » street canyon. Each CFD method is scrutinized for several geometric configurations by varying the downwind-to-upwind building-height ratio (H d/H u) and street canyon-width to building-width aspect ratio (S / W) for inflow winds perpendicular to the upwind building front face. Disparities between the numerical results and experimental data are quantified in terms of their ability to capture flow topological features for different geometric configurations. Ultimately, all three methods qualitatively predict the primary flow topological features, including a saddle point and a primary vortex. But, the secondary flow topological features, namely an in-canyon separation point and secondary vortices, are only well represented by the LES method despite its failure for taller downwind building cases. Misrepresentation of flow-regime transitions, exaggeration of the coherence of recirculation zones and wake fields, and overestimation of downwards vertical velocity into the canyon are the main defects in QUIC-URB, RANS and LES results, respectively. All three methods underestimate the updrafts and, surprisingly, QUIC-URB outperforms RANS for the streamwise velocity component, while RANS is superior to QUIC-URB for the vertical velocity component in the street canyon.« less
  • Part of the urban heat island effect can be attributed to dark pavements that are commonly used on streets and parking lots. In this paper we consider two light colored, hence cooler, alternative paving materials that are in actual use in cities today. These are Portland cement concrete (PCC) pavements and chip seals. We report measurements of the albedos of some PCC and chip sealed pavements in the San Francisco Bay Area. The albedos of the PCC pavements ranged from about 0.18 to 0.35. The temperatures of some PCC pavements are also measured and calculated. We then consider how themore » albedos of the constituent materials of the PCC (stone, sand and cement) contribute to the albedos of the resulting finished concrete. The albedos of a set of chip sealed pavements in San Jose, CA, were measured and correlated with the times of their placement. It is found that the albedos decrease with age (and use) but remain higher than that of standard asphalt concrete (AC) for about five years. After t hat, the albedos of the chip seals are about 0.12, similar to aged AC. The fact that many PCC pavements have albedos at least twice as high as aged AC suggests that it is possible to have pavement albedos that remain high for many years.« less
  • A series of arguments are made for using plants as air pollution abatement devices in urban areas. A series of recommendations are made. They are: that appropriate Federal agencies undertake studies to assess the potentials for reducing air pollution in the urban environment by plantings of vegetation, that information and technical assistance be made available by a designated Federal agency to local communities on the uses of vegetation to control air pollution, and that an appropriate Federal agency be designated to draw up and execute a plan of economic assistance to metropolitan areas chosen as demonstration areas for exploring andmore » developing plantings as a means for controlling air pollution.« less