Influence of Material Models on the Numerical Predictions of Thermomechanical Behavior of Silicon Photovoltaic Modules

Abstract

Silicon photovoltaic (PV) modules are made using different materials, namely glass, EVA, silicon, and a backsheet material such as PET. To develop a numerical thermomechanical PV module model capable of providing accurate predictions, the influence of the material models on the predictions must be analyzed. A two-dimensional, thermomechanical, finite-element (FE) model of PV modules was created, and it was able to reproduce some experimental measurements. It was then used to study the influence of the material models on the numerical predictions. Attention was given to the material models of EVA and silicon. Firstly, the material model of EVA was considered, and the predictions of the following models were compared: linear elastic, temperature-dependent linear elastic, and viscoelastic. Secondly, as the coefficient of thermal expansion (CTE) plays a major role in the thermomechanical behavior, the influence of its temperature dependence on the predictions was compared. The numerical results show that it is necessary to use a viscoelastic EVA model to reproduce the experimental data of the change in cells gap. It was also found that the temperature dependence of the CTE of EVA and silicon has significant influence on the module deflection and stress, hence it should be taken into consideration in future numerical studies.