The role of corner vortices in dictating peak wind loads on tilted flat solar panels mounted on large, flat roofs

Uplift wind loads on tilted flat PV panels mounted on the roofs of wide, rectangular, low-rise flat-roofed building were measured in an atmospheric boundary layer wind tunnel. The results indicate that for panels aligned with the building axes, the bubble separation that occurs for winds normal to a building face does not significantly increase these loads. Conversely, wind loads associated with the corner vortices are significantly higher than in the absence of the vortex. The direction of panel tilt relative to the vortex swirl, the position of the panel relative to the vortex reattachment, and the proximity of the panel to the vortex-originating corner together control the peak uplift. It is through changes to the vortices that the parapets affect wind loads. Vortex-related winds loads so dominate the uplift patterns on the roof that they need to be the primary consideration in any method designed to calculate these loads. This includes both experiments designed to study wind loads on this kind of PV racking system, and any calculation methods currently being codified in standards around the world.