Ten years outdoor operation of silicon based photovoltaic modules at central latitude of Japan

• The performance of all PV modules decreased approximately linearly.
• The performances of sc-Si and mc-Si PV modules were low in summer and high in winter.
• The performances of the a-Si and tandem PV modules were high in summer and low in winter.
• For a-Si, the recovery of PR by thermal annealing in summer decreased with time, and it led to the great DR in summer.
• The tandem PV module overcame the shortcoming of the a-Si PV module by reducing the thickness of a-Si.

For the estimation of energy output from photovoltaic (PV) modules, considering the impact of degradation is essential. In this study, the longtime outdoor performance of various types of silicon-based PV modules [single crystalline Si (sc-Si), multi crystalline Si (mc-Si), amorphous Si (a-Si), a-Si/micro crystalline Si tandem, and a-Si/a-SiGe/a-SiGe three-stack (3-stack)] which were installed at the same outdoor exposure condition in Shiga Prefecture, Japan were investigated using Performance Ratio (PR) as an index of performance of PV modules for ten years from 2000 to 2009. Yearly PR and monthly PR were analyzed and degradation rates (DR) were calculated. The DR was different on the kinds of PV modules from 0.404 to 3.51%/year. The a-Si PV module showed the largest DR and the 3-stack PV module had the least trend to degrade. The analysis of the monthly DR indicated that the high DR of the a-Si PV module was due to the quite large DR in summer, whereas the monthly DR of sc-Si and mc-Si PV modules did not differ much from each other throughout the years.