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Title: Wind loads on flat plate photovoltaic array fields. Phase III, final report

Abstract

The results of an experimental analysis (boundary layer wind tunnel test) of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays are presented. Local pressure coefficient distributions and normal force coefficients on the arrays are shown and compared to theoretical results. Parameters that were varied when determining the aerodynamic forces included tilt angle, array separation, ground clearance, protective wind barriers, and the effect of the wind velocity profile. Recommended design wind forces and pressures are presented, which envelop the test results for winds perpendicular to the array's longitudinal axis. This wind direction produces the maximum wind loads on the arrays except at the array edge where oblique winds produce larger edge pressure loads.

Authors:
;
Publication Date:
Research Org.:
Boeing Engineering and Construction Co., Seattle, WA (USA)
OSTI Identifier:
6782774
Alternate Identifier(s):
OSTI ID: 6782774
Report Number(s):
DOE/JPL/954833-81/3
DOE Contract Number:
NAS-7-100-954833
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; SOLAR CELL ARRAYS; WIND LOADS; AERODYNAMICS; BOUNDARY LAYERS; DESIGN; INCLINATION; PRESSURE GRADIENTS; PRESSURE MEASUREMENT; RECOMMENDATIONS; VELOCITY; WIND; WIND TUNNELS; DYNAMIC LOADS; EQUIPMENT; FLUID MECHANICS; LAYERS; MECHANICS; SOLAR EQUIPMENT; TUNNELS 140501* -- Solar Energy Conversion-- Photovoltaic Conversion

Citation Formats

Miller, R.D., and Zimmerman, D.K. Wind loads on flat plate photovoltaic array fields. Phase III, final report. United States: N. p., 1981. Web. doi:10.2172/6782774.
Miller, R.D., & Zimmerman, D.K. Wind loads on flat plate photovoltaic array fields. Phase III, final report. United States. doi:10.2172/6782774.
Miller, R.D., and Zimmerman, D.K. Wed . "Wind loads on flat plate photovoltaic array fields. Phase III, final report". United States. doi:10.2172/6782774. https://www.osti.gov/servlets/purl/6782774.
@article{osti_6782774,
title = {Wind loads on flat plate photovoltaic array fields. Phase III, final report},
author = {Miller, R.D. and Zimmerman, D.K.},
abstractNote = {The results of an experimental analysis (boundary layer wind tunnel test) of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays are presented. Local pressure coefficient distributions and normal force coefficients on the arrays are shown and compared to theoretical results. Parameters that were varied when determining the aerodynamic forces included tilt angle, array separation, ground clearance, protective wind barriers, and the effect of the wind velocity profile. Recommended design wind forces and pressures are presented, which envelop the test results for winds perpendicular to the array's longitudinal axis. This wind direction produces the maximum wind loads on the arrays except at the array edge where oblique winds produce larger edge pressure loads.},
doi = {10.2172/6782774},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Apr 01 00:00:00 EST 1981},
month = {Wed Apr 01 00:00:00 EST 1981}
}

Technical Report:

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  • 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 velocitymore » 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.« less
  • Results are presented of a combined experimental (wind tunnel test results) and theoretical analysis utilizing random harmonic analysis techniques to predict the dynamic response and the structural dynamic loads of flat plate photovoltaic arrays due to wind turbulence. Guidelines for use in predicting the turbulent portion of the wind loading on future similar arrays using the results of this study are presented. The dynamic response and the loads dynamic magnification factor of the two array configuration (a four post array and a two post array) are similar. In general, the largest response and dynamic magnification factor occur at a midmore » chord location on an array and near the trailing edge. A technique employing these magnification factors and the wind tunnel test rms fluctuating pressure coefficients to calculate design pressure loads due to wind turbulence is presented.« less
  • The objective of Phase III for the establishment of the practicality of a process producing semiconductor-grade silicon by a two-step process, the preparation of silane and the subsequent pyrolysis of silane to yield high-purity silicon, was (1) the detailed engineering design, fabrication, installation, checkout, and operation of an Experimental Process System Development Unit (EPSDU), (2) the performance of a supporting research and development program to provide an information and quality control base usable for the EPSDU and for technological design and economic analyses for potential scale-up of the process, and (3) the performance of iterative economic analyses of the estimatedmore » product cost and of large-scale plant cost for production of semiconductor-grade silicon in a EPSDU capable of 100 metric tons of silicon per year.« less
  • A study has been conducted to identify and develop module safety requirements for photovoltaic module and panel designs and configurations likely to be used in residential, intermediate, and large-scale applications. The National Electrical Code and Building Codes were reviewed with respect to present provisions which may be considered to affect the design of photovoltaic modules. Limited testing, primarily in the roof fire resistance field was conducted. The generation of engineering safety requirements included a safety workshop which encompassed a broad cross-section of the photovoltaic community. Comments from the workshop resulted in additional studies and further investigations which led to themore » development of a UL Proposed Standard for Safety - Flat-Plate Photovoltaic Modules and Panels. Additional work covered the initial investigation of conceptual approaches and temporary deployment, for concept verification purposes, of a differential dc ground-fault detection circuit suitable as a part of a photovoltaic array safety system.« less
  • Bechtel National, Inc., has conducted a study of feasible low-cost structures for solar photovoltaic central power plants. Wind load magnitudes for these arrays significantly influence structural costs. Wind load prediction is hampered by the lack of specific information for these unique structures. Accordingly, a wind-tunnel test program was completed at the Fluid Dynamics Laboratory of Colorado State University, Fort Collins, Colorado. This testing gave wind force coefficients for single or large-field photovoltaic arrays and the resulting design criteria are reported. The test program was a limited effort to advance the state of the art and further work is recommended.