The Influence of Incidence Angle on the Reliability of Photovoltaic Modules: Lessons Learned

Abstract

To maximize energy yield, photovoltaic (PV) system designers optimize parameters that enhance plane-of-array irradiance, with module tilt angle being a key factor. However, higher irradiation also raises operating temperatures, accelerating degradation mechanisms. While simulations offer insight, experimental validation is essential to assess tilt angle impacts on long-term reliability. This study presents an indoor accelerated aging test replicating variations in UV exposure linked to tilt angle. passivated emitter and rear contact (PERC) c-Si mini-modules underwent controlled UV soaking, elevated temperatures, and humidity to replicate prolonged outdoor conditions. Degradation was monitored through I–V curve measurements and electroluminescence imaging. Encapsulant discoloration and photobleaching primarily reduced short-circuit current (I_SC), while boron-oxygen light-induced degradation (BO-LID) and light and elevated temperature-induced degradation (LeTID) contributed to I_SC and open-circuit voltage (V_OC) losses. Further UV doses of 34, 17, and 6.5 kWh/m², representing different tilt angles, caused maximum power (P_max) reductions of 0.79%, 0.61%, and 0.35%, respectively. These results highlight the need for further study of BO-LID and LeTID in PERC and other c-Si PV technologies. The observed tilt angle effects cannot be generalized to long-term degradation. Further investigation into long-term impact by applying stabilization methods to the modules and afterward fitting the data to degradation models is needed to draw final conclusions.