Performance analysis and modelling of a 50 MW grid-connected photovoltaic plant in Spain after 12 years of operation

This study aims to estimate the performance and losses of a 50 MW photovoltaic (PV) utility-scale after 12 years of operation. The PV plant has monocrystalline and polycrystalline silicon modules and is located in the central region of Spain with an annual insolation of 1976 kWh/m2. Monitoring data over the entire year 2020 has been analyzed and filtered to assess the performance results following the IEC 61724 standard guidelines. The annual average reference yield, final yield, performance ratio and capacity utilization factor are of 5.44 h/d, 4.28 h/d, 79.24%, and 19.77%, respectively. Besides the experimental analysis, this work improves the estimation of the daily performance ratio, especially in days with low insolation. Two different modelling approaches have been assessed and compared. In first place, a physical model has been adopted, based on the most common losses, and including an exponential expression to account for low irradiance losses. In second place, statistical models have been used, with either multiple linear regressions or random forest algorithms. In contrast with other published models which require many inputs, the best accuracy has been reached with the random forest model using only the ambient temperature and solar irradiance as predictors, obtaining a RMSE of 1% for the PR and for the energy production.