Degradation factor analysis of crystalline-Si PV modules through long-term field exposure test

Degradation factors that affect the performance loss of crystalline-Si PV modules have been analyzed through long-term field exposure test, in order to contribute to the long-term reliability improvement. Tested PV modules were manufactured in the early 1990´s and many modules were stable for 10-12 years exposure. However, some of the modules showed the performance loss which exceeds 10% either due to discoloration caused by the delamination between the solar cell and EVA or due to increase of the series resistance caused by the cracks in electrode soldering. It is demonstrated that the signs of these degradations can be detected before the performance loss become significant by careful visual inspection or the temperature distribution inspection under forward bias condition.