Towards a quantification of thermal and thermomechanical stress for modules in building-integrated photovoltaics configurations

Abstract

Due to reduced rear-side ventilation, building-integrated photovoltaics (BIPV) are prone to higher operating temperatures, which may impact their long-term performance and reliability. However, often overlooked in the study of thermomechanical stress in PV modules are the intraday temperature variations, resulting from factors such as cloud movements and subsequent changes in irradiance. This work proposes a statistical analysis of cell and module temperature measurements in single-cell c-Si modules on a test bench in Neuchâtel, Switzerland. The goal is to study and compare various BIPV-relevant module topologies with a range of factors such as the insulation type, tilt angle, and glass thickness. The standard indicators such as the 98th percentile temperature and diurnal temperature variations are examined, as well as proposed new thermomechanical stress indicators based on temperature gradients and cell versus module temperature differences. Unexpectedly, results indicate that, considering the intraday temperature variations, close-roof module configurations (with small ventilation gaps) are potentially at a higher risk of suffering long-term thermomechanical fatigue than fully insulated modules, which are exposed to higher operating temperatures.