The effect of partial shading on the reliability of photovoltaic modules in the built-environment
Ebrar Özkalay, Flavio Valoti, Mauro Caccivio, Alessandro Virtuani, Gabi Friesen, Christophe Ballif
Abstract
Residential photovoltaic systems often experience partial shading from chimneys, trees or other structures, which can induce hot-spots in the modules. If the temperature and frequency of these hot-spots are high, the module's reliability and safety may be at risk. IEC 61215-2:2021 hot-spot endurance test is utilized to evaluate the materials' ability to withstand partial shading. Since modules in residential systems can be subjected to higher temperatures than those in the open field, IEC TS 63126:2020 recommends adjusting the module temperature for the hot-spot endurance test according to the module's operating temperature. This study tested the hot-spot endurance of PERC, IBC and HJT modules under standard (55 °C) and more severe (75 °C, Level 2 condition in IEC TS 63126:2020) test conditions, as well as outdoor accelerated-ageing tests were performed with shadow masks. The results demonstrated that irrespective of environmental conditions, hot-spots can form at lower temperatures, with more shading-tolerant cells (i.e., cells with lower breakdown voltage) or with shorter strings. We also show that it is possible to shorten the effort- and time-consuming hot-spot endurance test described in the standard and obtain similar results. In addition, the hot-spot endurance test for residential PV systems was evaluated in terms of module temperatures and duration. In this respect, we propose to increase the testing temperatures of the hot-spot endurance testing for modules operating at high temperatures in IEC TS 63126:2020.