Wind loads on heliostats and photovoltaic trackers at various Reynolds numbers

Abstract

Wind loads on heliostats are usually determined at boundary layer, low-speed wind tunnels at which the design full-scale Reynolds number cannot be reached. In doing so, it is supposed the wind load coefficients are Reynolds number independent, which is known to be the case for sharp edged bodies. But for the stow position the usually round torque tube is directly exposed to the wind and could influence the wind loads. By measurements in a high-pressure wind tunnel, it can be demonstrated that the design-relevant wind load coefficients are not Reynolds number dependent. However, the inclination of the mirror plane in stow position, due to the deflection of the heliostats structure at high Reynolds number, leads to increased wind loads and must be considered. The results are also valid for photovoltaic trackers of similar shape.