Energy performance and degradation over 20 years performance of BP c-Si PV modules

The energy performance and degradation of 3 BP PV modules, type BP 1233, operating for a period of just more than 20 years are studied and compared to the nominal power output data. The 3 PV modules power the outdoor lighting of the Solar Campus and perform smoothly for all this period, without any special treatment or maintenance, although they were physically weathered on a continuous basis. Life cycle power degradation was estimated from a series of i, V experiments carried out under field conditions. The experimental analysis led to the determination of the present peak power, at STC, the series and shunt resistances, R_s and R_sh, respectively, and the fill factor, FF. Causes of degradation and especially of its extent were attributed to discolouring, junctions' damage, humidity ingress in the box, encapsulant delamination, hot spots, etc., as realized by in situ inspections.