Long-Term Performance and Shade Detection in Building Integrated Photovoltaic Systems

Building integrated photovoltaics (BIPV) operate in a unique environment compared with field-mounted systems and may experience elevated temperatures and recurrent or persistent shading. These stresses are expected to accelerate degradation, but there are few performance reports for true BIPV systems as defined in IEC 63092-1. Herein, the long-term performance (over 5-10 years) of 55 BIPV systems in Switzerland is reported. Using a year-on-year (YOY) performance loss rate (PLR) analysis, the median degradation rate of all systems together (fleet-wide) is determined to be 0.06% per year (i.e., essentially no degradation), though there is a large spread of rates. Visual inspection of the systems indicated that some are shaded at times, so a fault detection and diagnosis algorithm (FDDA) is developed to estimate the shading severity of the systems using their daily production profiles. The fraction of time in shading fault presents a linear trend for the upper limit of PLRs, though by itself it is not a strong predictor of system performance. On average, the degree of shading is found to increase in newer systems, and decrease in larger capacity systems. These results highlight the importance of alleviating shading stresses through innovative BIPV module and system design.

Automated summary

This study reports on the long-term performance of 55 BIPV systems in Switzerland, finding a median degradation rate of 0.06% per year with significant variation. An algorithm was developed to estimate shading severity in systems experiencing shading issues. It was observed that newer systems have higher shading severity while larger capacity systems have lower shading severity, emphasizing the importance of innovative BIPV module and system design to alleviate shading stresses.