PV module performance at PG&E

Outdoor performance is evaluated for a single-crystal, a polycrystalline, a ribbon, and three amorphous silicon modules. To compare the performance of PV modules, a model relating output power to irradiance and ambient temperature is developed. During typical midday conditions, crystalline silicon efficiencies are 9% to 12% while amorphous silicon efficiencies are 4% to 5%; performance estimated using the model is within +or-5% (relative) of measured performance. Crystalline silicon efficiencies are highest during the winter and lowest during the summer. Amorphous silicon efficiencies are less sensitive than crystalline silicon efficiencies to changes in ambient temperature. Technology improvements are evident when comparing the performance of these modules to that of older modules.