Evaluation of PV Module Outdoor Degradation rate by means of I-V Curve Fitting with DE and Linear Interpolation Method

Degradation rates of photovoltaic (PV) modules were calculated by means of linear interpolation method only using outdoor data such as module temperature, solar irradiance, and current-voltage characteristics. This method could quantify not only degradation rates of output power of PV modules but also the others characteristic values such as short-circuit current, open-circuit voltage, and fill factor. As a result, it is revealed that crystalline silicon PV modules are degraded due to current reduction. In addition, relative errors of calculated degradation rate of each characteristic values are within 0.8% in average by comparing with the result of indoor measurement.