Technical Evaluation of a USSC Integrated/Direct Mount PV Roofing Module System at NREL

The results of a 16 month technical evaluation performed on a nominal 1 kWac utility-interconnect amorphous silicon PV system deployed at the National Renewable Energy Laboratory's PV outdoor test site are given here. The system employs 64 prototype United Solar Systems Corp. Integrated/Direct Mount PV Roofing Modules mounted on simulated attic/roof structures. In this paper we show that the PVarray fill factor has been relatively stable with respect to time and that the seasonal variations in performance can be largely attributed to seasonal variations in current. We also show that in determining the summer and winter ac power output, the summation of the manufacturer-supplied module peak powers at STC for a; similarly located and configured a-Si PV array should be derated by factorsof approximately of 0.83 and 0.78 for summer and winter operation, respectively.