Operating Temperatures and Diurnal Temperature Variations of Modules Installed in Open-Rack and Typical BIPV Configurations

Because of building skin integration with restricted or reduced rear-side ventilation, elevated operating temperatures are expected in building-integrated photovoltaics (BIPV) modules and systems, which may impact their long performance and reliability. This article reports an analysis of operating temperatures and diurnal (day-night) temperature variations of the modules in open-rack and some BIPV mounting configurations (BIPV-ventilated and BIPV-insulated) monitored over a period of 2-5 years in Southern Switzerland. The modules in BIPV configurations operated at 20 degrees C-30 degrees C higher temperatures than the same modules installed in an open-rack configuration. In the worst-case, the temperature of the BIPV modules reached values slightly above 90 degrees C. In addition, the modules installed in BIPV configurations were confronted with considerably greater diurnal (day-night) temperature variations compared with the same modules with an open-rack mounting (on average 18 degrees C-25 degrees C more). This demonstrates that these modules can suffer from higher thermo-mechanical stresses, potentially leading to accelerated degradation rates, and shorter lifetimes. The suitability of the indoor qualification and safety tests in IEC 61215 and IEC 61730 were evaluated according to the threshold set at the 98th percentile real-life operating module temperature (as defined in the IEC TS 63126 guideline for qualifying PV modules operating at elevated temperatures). This study shows that according to IEC TS 63126, BIPV modules on a tilted surface in Southern Switzerland may need to be tested at harsher environmental conditions (e.g., higher temperatures) in a selection of indoor qualification and safety tests.