Effects of tilt angle on secondary motions over solar installation of E-type roughness*

For renewable energy to replace fossil fuels as the primary source of energy to fulfill the world's ever-increasing energy needs, the design of large-scale solar farms must reduce cost and undesirable changes to the atmospheric boundary layer (ABL). Photovoltaic (PV) technology can move towards cost parity by reducing efficiency losses due to working conditions; it has been shown the solar panel inclination greatly affects the convective heat transfer near the panels, allowing for thermal management of the PV modules. However, the effects of tilt angle on the secondary motions above the solar farm, which can affect the ABL, have yet to be investigated. The PV canopy is modeled as a novel type of roughness, referred to as elevated (or E-type) roughness. E-type roughness expands on other blunt roughness types (e.g. K-type or D-type) to include additional system variations known to affect local turbulence. This study utilizes Portland State University's wind tunnel to model an infinitely long solar farm with 4 tilt angles at variable wind speeds. Stereoscopic particle image velocimetry data will show the secondary and tertiary vortices extending into the ABL for each tilt angle. Results both inform the design of future PV systems and introduce E-type roughness as a model applicable to natural and industrial environments.