Impacts of system yaw on secondary and tertiary flow structures generated over E-type roughness elements.

Growing demand for photovoltaic (PV) solar energy has caused many open landscape surfaces to change with the adoption of PV systems. It is known that flow over natural and manmade objects, such as mountains and urban centers, create secondary vortices which can extend to the atmospheric boundary layer (ABL). These vortices are widely studied over blunt roughness types labelled only by height and separation (e.g. K-type or D-type). However, elevated profiles of PV systems are unique, even from vegetative canopies, since common variations such as spacing, angle, and flow direction are known to greatly effect local turbulence. This study proposes PV canopies as a novel type of elevated roughness (E-type) and explores how PV system configuration impacts secondary and tertiary vortices for outer flow approaching the ABL. Wind tunnel experiments were performed on a scaled PV array subjected to varied inflow conditions, inter-panel spacing, and system yaw (a). Stereoscopic particle image velocimetry data show modified secondary and tertiary motions in the reset turbulent boundary layer dependent on system configuration. This study informs not only design of future PV systems, but also introduces the complexity of E-type roughness applicable to natural and industrial environments.