Correlation of power loss to string and module level performance for arrays of c-Si and CIGS technologies in the North East climate

The generated power output of a PV plant is generally less than the estimated power output. This results in a reduced available power for usage or revenue. This reduction can be minimized with proper real time monitoring of the PV array. The importance of string level monitoring using sensors at the combiner level to identify triggers for underperforming strings, and its further analysis using I-V curve monitoring and infrared imaging, is illustrated in this study. The c-Si string level monitoring indicates that a 2-5% percent difference in Pmax is not always driven by a common cause, with the one array having a reduction in current and another due to voltage differences.. The overall degradation rates are within 0.3% for the 3 year operation period of the array. The correlation of the degradation rate to the performance metrics is presented along with the weather corrected performance ratio of the arrays which is calculated to be 85-90%.