Long-term power performance evaluation of vertical building integrated photovoltaic system

As the mandatory scope of zero-energy building certification has expanded, the integration of renewable energy systems into building designs and energy operations has significantly increased. The long-term maintenance of these systems is crucial for sustaining zero-energy goals. The primary key to maintaining renewable energy systems is to assess quantitative performance factors, such as degradation and malfunction. This study presents a comprehensive evaluation of the long-term power performance of a large-scale vertical building-integrated photovoltaic system, which has been monitored over 9 years (2012–2020). The system, comprising 22 arrays with a total installed capacity of 142.654 kWp, was analyzed to derive quantitative performance indicators that highlight the importance of continuous maintenance. The photovoltaic system's arrays were investigated to separate them into analysis groups, and simulation-based analysis was carried out for the detailed assessments. The findings revealed that 19 of 22 arrays were operating normally, while three experienced malfunctions. In 2020, a 19.12 % performance degradation was observed in normally operating arrays compared to 2012. Post-malfunction, the affected arrays performed at approximately half the efficiency of the normal arrays. Despite theses issues, inverter efficiency remained stable across all arrays. However, a noticeable decline in array efficiency indicated performance degradation due to specific array issues. When compared to simulation-based theoretical performance, in 2020, the malfunctioned arrays exhibited nearly triple the performance degradation of the normally operating arrays. These results underscore the critical role of quantitative performance indicators in maintenance strategies and demonstrate how inadequate maintenance can lead to substantial power generation losses.