Calculation of Degradation Rates of Poly Crystalline Si and CIGS PV Module using Outdoor Linear Interpolation Method

We propose the method to calculate the degradation rate of PV modules by outdoor linear interpolation method (LIM). Since the reference I-V curves which are based on measured I-V curves and used to LIM are created in each season, transitions of expected I-V curves indicate how PV modules degrade. The degradation rates of not only the maximum power but also the other parameters such as short circuit current and open circuit voltage can be calculated from the expected I-V curves. In this paper, the outdoor degradation rates of poly crystalline Si and CIGS were calculated. As a result, in poly crystalline Si case, the degradation rate of maximum power was calculated as -0.4 %/year due to short circuit current reduction. In CIGS case, although the initial power generation performance was better than the datasheet value, the annual degradation rate of the maximum power was calculated as -2.1 %/year. The reason of maximum power reduction was the reduction of both short-circuit current and open-circuit voltage.