Building Integrated Photovoltaic (BIPV), Degradation, Monitoring, Roofing Systems, Shading
Summary / Abstract:
Building integrated photovoltaic (BIPV) systems often operate under elevated temperatures and recurrent shading, which can accelerate performance loss. However, to date there are few reports on long-term performance of BIPV systems, as distinct from building applied PV (BAPV). This work reports the performance loss rates (PLR) after 5 to 10 years of operation of 55 rooftop BIPV systems in Switzerland. Median PLR was calculated to be 0.06% per year, indicating essentially no degradation, though there was a large spread of rates. Some systems were noted to be shaded at times, so a fault detection and diagnosis algorithm (FDDA) was developed to quantify shading severity. The FDDA used DC voltage and current and meteorological data as inputs and classified faults according to pre-defined thresholds. Faults caused by shading were grouped to determine the shading factor of each system. Shading factor showed a weak correlation to PLR, but delineated an upper limit, indicating it limits maximum achievable performance. Shading factor was found to increase in newer systems, and decrease with system capacity. Through innovative BIPV module and system design, the effect of shading and corresponding performance losses can be mitigated.