Abstract
To accelerate the degradation with thermal fatigue in crystalline silicon photovoltaic modules, the modules were exposed to dry thermal stress with rapid thermal cycling, and module impedance was monitored in situ during this testing. The spikelike increase in module impedance at a temperature-alteration point was observed in the early stage of this rapid thermal cycling. The pattern of increase in module impedance proceeded step-by-step, from the early stage, via the double-spikelike pattern at two temperature-alteration points (the middle stage), and finally to the successive increases in module impedance in the high-temperature period (the late stage). The nondestructive analyses suggest that the interconnector failures without the defects of photovoltaic cells occurred. From these results, it is suggested that the pattern of increase in module impedance is related to the interconnection degradation of modules, and that the rapid thermal cycling with in situ monitoring of module impedance would be a useful procedure for the earlier detection of interconnection failures in photovoltaic modules.