Effect of Encapsulation Modulus on the Response of PV Modules to Mechanical Stress

Abstract

The crystalline silicon photovoltaic (PV) module is a laminate assembly composed of materials with widely varying mechanical and thermal properties. The properties of these materials are important factors influencing the performance and reliability of modules following exposure to external mechanical stress. In particular, a key role of encapsulation is to protect the solar cells from external stresses, yet some encapsulant mechanical properties can vary with temperature. Since current mechanical loading tests for certification of PV modules are performed at room temperature, these tests may not adequately simulate or accelerate in-field mechanical stresses and failures. This work examines the impact on module performance and cell integrity of dynamic and static load testing at both high and low temperature using a custom-built mechanical testing rig capable of operating inside a climate chamber. Two different encapsulation materials were compared: a standard EVA thermosetting film and a silicone. The loading conditions were based on relevant qualification test standards and test modules were characterized for performance and damage using a solar simulator and electroluminescence imaging. Testing revealed significant differences in the ability of the encapsulant to protect the solar cells from damage due to mechanical loading at various temperatures, with the encapsulant modulus being a critical factor.