In-Situ Measurement of Power Loss for Crystalline Silicon Modules Undergoing Thermal Cycling and Mechanical Loading Stress Testing

We analyze the degradation of multi-crystalline silicon photovoltaic modules undergoing simultaneous thermal, mechanical, and humidity-freeze stress testing to develop a dark environmental chamber in-situ measurement procedure for determining module power loss. We analyze dark I-V curves measured on modules undergoing degradation in three steps; first for shunting and recombination losses; second, series resistance and lifetime losses; and finally, other losses including short circuit current, current mismatch losses associated with a decrease in photo-current generation by removal of some cell areas due to cell fractures, and the additional series resistance losses observed under illumination. Based on the analysis, we propose an in-situ module power loss monitoring procedure that relies on dark current-voltage measurements taken during the stress test and initial and final module flash testing to determine the power degradation characteristic of the module.