CFD Analysis of Wind Loading on Rooftop Solar PV Arrays
Rooftop solar wind CFD comparing building layouts and array sizes, giving pressure data on both panel faces for structural design.
Project brief
A client designing large rooftop solar installations needed dependable wind loads on its PV panels. Code coefficients give a general answer, but the actual load depends on how the buildings sit beside each other and how large the array is.
Shirsh Technosolutions ran 3D CFD in ANSYS Fluent to find the pressure on the top and bottom faces of the panels for each layout, and gave the results to the client's structural designer.
What was at risk
Wind passing over a roof separates at the edges and parapets, and the panels sit inside that disturbed flow. The client wanted to compare two building arrangements, separate buildings and a common building, each with small, medium and large arrays.
For every case the pressure on both faces of the panels had to be known, because the net load on a panel is the difference between them. The study also had to show which combination gives the critical load for design.
Solution offered
We built 3D models of both building arrangements with each array layout and refined the mesh around the panels and their supports, where the flow changes fastest. A power-law wind profile was applied at the inlet, with a pressure outlet and no-slip walls.
The flow was solved as steady and pressure-based with the SST k-ω turbulence model. For each case we plotted velocity and pressure contours and streamlines, and extracted the area-weighted average pressure on the top and bottom surfaces of the panels. With every case set up the same way, the comparison pointed clearly to the critical one.
Common questions
Why look at both faces of the panel? A panel is loaded by the pressure difference between its top and bottom surfaces. Suction under the panel can add as much load as pressure on top, so either face alone can mislead the design.
Why does the building layout change the load on the panels? The building shapes the wind before it reaches the array. Gaps between separate buildings, roof edges and parapets cause separation and recirculation, and these change the local pressure on the panels.
Challenges we overcame
Comparing pressure and velocity fields across building configurations and spacing conditions.
Predicting pressure distribution on the top and bottom surfaces of the PV panels.
Analyzing flow separation and recirculation zones around the PV panels and support structures.
Identifying the critical wind loading case for structural design.
How we executed
- 1
Built 3D models of the separate and common building arrangements with each array layout
- 2
Refined the mesh around the panels and support structures
- 3
Applied a power-law wind profile at the inlet, a pressure outlet and no-slip walls
- 4
Solved steady, pressure-based flow with the SST k-ω turbulence model
- 5
Plotted velocity and pressure contours and streamlines for every case
- 6
Extracted area-weighted average pressure on the top and bottom panel surfaces
- 7
Compared all cases to identify the critical wind loading condition
Project outcome
Identified the critical wind case across building configurations and array sizes.
Gave area-weighted pressures on the top and bottom panel surfaces for structural design.
Showed where flow separation and recirculation around the arrays raise the load.
Gave the structural designer CFD-based loads in place of generic code coefficients.
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