ANNUAL DEGRADATION RATES OF BULK CLYSTALLINE SILLICON PV MODULES ESTIMATED FROM INDOOR AND OUTDOOR MEASUREMENTS

摘要

The global cumulative solar PV installations reached nearly 200 GW by the end of 2014. Therefore, the investigation of long-term durability of PV systems is much important. The National Institute of Advanced Industrial Science and Technology (AIST) has measured the outdoor performance from eight kinds (15 types) of PV arrays in AIST Kyushu Center. In this study, we focus on bulk crystalline silicon (c-Si) PV modules, because the market share of bulk c-Si technologies is more than 90% in 2014. We evaluate the annual degradation rates of the performance of the PV modules by two methods. One method is estimated from the average or total power outputs of all installed c-Si PV modules, which are measured by a solar simulator once a year. The other method is based on I-V curves of the PV arrays, which have been measured by I-V curve tracers for outdoor usage every ten minutes since the start of 2013. Both the results based on the indoor and outdoor measurements show that the degradation rates of the ordinal p-type c-Si PV modules are quite low, although those of the high-efficiency n-type c-Si PV modules tend to be high. In recent years, new processes, which enhance PV cell efficiencies such as MWT (Metal Wrap Through) and PERC (Passivated Emitter Rear Cell) technologies, are adopted into commercial PV modules. Therefore, the durability and reliability of the PV modules with new processes should be investigated by both acceleration tests and actual outdoor operation.