Effect of soiling on wind-induced cooling of photovoltaic modules and consequences for electrical performance

This study investigates the effect of soiling on the cooling capacity of the wind and its consequences for the performance of photovoltaic modules. Cooling and electrical characteristics were measured on a glass-glass module for wind speeds up to 4 ms(-1) and soiling levels up to 41 gm(-2). Soiling can promote the cooling of photovoltaic modules and affects the influence of wind on module performance. Soiling may result in less external heating of the module's surface because of the higher albedo of a soiled module compared to a clean one. Also, soiling results in a decrease of the amount of heat to be evacuated by the wind whereas the capacity of the wind to evacuate heat is not affected; the surplus in cooling capacity can be used to cool the module to a lower temperature than if the module were clean. Soiling had a negative effect on the short-circuit current and the maximum power whereas no direct effect on the open-circuit voltage was observed, but soiling did stimulate the positive effect wind has on the voltage. The study sheds more light on the physical processes that occur on and near the surface of a soiled photovoltaic module.