Performance degradation and reliability evaluation of crystalline silicon photovoltaic modules without and with considering measurement reproducibility: A case study in desert area

In this paper, performance degradation and reliability evaluation of crystalline silicon photovoltaic modules deployed in desert climate was investigated based on the more than 7-year tracking test. It is found that peak power standard deviation first increased with time, reaching the peak when modules operated for 3 years, and then continuously decreased. Then, relationship among power warranty, power degradation rate and tolerance on maximum power is revealed for the first time. If 1% of module failures during warranty period is allowable, the 30-year warranty can be realized when degradation rate is 0.4–0.6 %/year with tolerance 0 ∼ +5% and 0 ∼ +3%, or degradation rate is 0.5 %/year with tolerance ±5% and ±3%, or degradation rate is 0.4 %/year with tolerance ±10%, ±5% and ±3%. Finally, reproducibility of power measurement is introduced for more accurately evaluating module performance degradation and reliability. Meanwhile, determination procedure of reproducibility for module electrical performance is systematically set forth. It is found that power warranty period can be prolonged if reproducibility is considered. The results obtained in this paper can provide new insights into performance degradation, reliability assessment and power warranty for fielded crystalline silicon solar modules.