Performance evaluation of photovoltaic self-consumption systems on industrial rooftops under continental Mediterranean climate conditions with multi-string inverter topology

Abstract

This study analyses the performance and grid integration of seven photovoltaic self-consumption systems installed on industrial rooftops under real operating conditions. The analysed systems feature different orientations and peak power capacities, allowing to evaluate their behaviour through different indices and metrics proposed in the IEC 61724 and the literature, such as the Performance Ratio (PR), Final Yield (Yf) or Capacity Utilisation Factor (CUF), among others. Additionally, the interaction of these systems with the load and the electrical grid is examined and proposed, providing a better view of their operation. The results reveal that, although most systems operate close to expectations, with PR, Yf and CUF annual averages of 0.81, 1555.51 h/y and 0.19 respectively, factors such as partial shading, capture losses, and inverter configurations without grid injection affect their efficiency. The proposed Equivalent Capacity Utilisation Yield (YL), Load Ratio Yield (YGL), Load Ratio To Grid Yield (YGL,TG) and Load Ratio From Grid Yield (YGL,FG) are introduced to characterise the interaction between local demand and electrical grid constraints, providing a comprehensive assessment of system performance and grid use. A reduction in the full-load equivalent hours during which the interconnection node operates at its nominal capacity is observed following the integration of rooftop photovoltaic systems, as the values of YGL are consistently lower than those of YL. The results also indicate that the indices and metrics proposed in the literature, together with real data monitoring, are effective tools for evaluating the performance of photovoltaic systems and optimising their integration into electrical grids.