e-type rough wall turbulent boundary layers: Considerations for solar PV arrays

Renewable energy sources, such as solar photovoltaic (PV) technologies, provide a promising pathway to replace fossil fuels as the world’s primary source of energy. The introduction of these technologies is known to affect the atmospheric boundary layer (ABL), but further investigation is necessary to characterize these effects. Researchers have explored ABL development by conceptualizing natural and industrial environments as rough surfaces, many of which fall into the well-established categories of k-type and d-type roughness. For both types, roughness elements are blunt objects attached to the ground. When conceptualizing a solar array as a rough surface, it is clear that the roughness elements (PV modules) are elevated, introducing a new elevated roughness type, called e-type roughness.

To explore e-type roughness, stereoscopic particle image velocimetry (PIV) measurements were taken on an experimentally scaled solar array in the Portland State University wind tunnel. Experimental cases were chosen to mimic the potential system-level changes of a solar array. These include system yaw, inter-panel spacing, panel height and inclination angle. The classical law of the wall is applied to gain insight into the boundary layer development over a solar array. Results prove that the boundary layer development is dictated by system-level changes. This fundamental approach to the solar array boundary layer informs the design of PV systems, in addition to providing a model that may be applied more broadly to understand the environmental consequences of natural and industrial environments.