Full Scale and Wind Tunnel Testing of a Photovoltaic Panel Mounted on Residential Roofs

Abstract

Reliable wind loading information on solar panels is essential for the large-scale deployment of solar technologies in the United States. However, only a limited amount of published wind tunnel and computational fluid dynamics (CFD) research is available to address aerodynamic loading information for photovoltaic (PV) panels and solar water heaters. Because of this knowledge gap, no provisions exist in the current building codes and standards for the design of PV mounting systems in areas that are vulnerable to extreme winds. This study presents aerodynamic data based on experimental testing of a residential roof-mounted PV panel. The goal of the study was to develop a test-based dataset of aerodynamic loading effects for the test cases considered. Full-scale testing of a single PV panel mounted on residential building models was conducted with the 6-fan Wall of Wind (WoW) hurricane simulator. During the full-scale tests, multi-axial load cells measured the aerodynamic reaction forces at four locations where the PV racking system was attached to the roof. Net aero-dynamic force coefficients were obtained directly from the reaction forces measured. Model scale testing of similar configurations was conducted in a boundary layer wind tunnel (BLWT) at a scale of 1:12. During the wind tunnel tests, the PV panel model was equipped with 28 pressure taps to measure the overall pressure distribution on the panel. Net aerodynamic force coefficients were determined from the simultaneous wind tunnel pressure time histories measured from upper and lower solar panel surfaces using the pressure integration method. A systematic comparison between the aerodynamic force coefficients derived from full scale and wind tunnel testing is in progress. Noteworthy fluctuations of the glass panel were observed during the full-scale tests for cases when the PV panel was mounted parallel to a flat roof. This phenomenon is seen in the uplift force time histories, indicating PV panels may experience across-wind loading effects under certain mounting configurations. Overall, good agreement was observed between the large- and small-scale measurements for critical PV inclination angles.