Influence of Mechanical Load at Low Temperatures on Cell Defects and Power Degradation at Full Scale PV Modules

The scope of this work is the application and evaluation of mechanical load tests on photovoltaic modules for the simulation of wind and snow loads at -20 and -40 °C. This behavior is not taken into account in the existing standards for module certification. For most PV modules, EVA is taken as encapsulation material, which has a low Young’s modulus at room temperature absorbing mechanical strain transferred from the top layer to the cells. This Young’s modulus rises by several orders of magnitude when the temperature is reduced to -40 °C accompanied by increasing forces on the cells and subsequently cell breakage. Cyclic and static mechanical load tests at three temperatures (25, -20, -40 °C) were carried out at Fraunhofer ISE. The tests have unveiled a correlation between cell cracks and the temperature at which the mechanical load was applied. Compared to the applied cyclic load profiles, the test according to IEC 61215 – 10.16 caused the most failures at all temperatures.