Thermo-mechanical assessment of solar cell displacement with respect to the viscoelastic behaviour of the encapsulant

This paper is proposed to enhance the mechanical simulation model for crystalline solar modules by implementing the viscoelastic behaviour of the encapsulation material ethylene-vinyl acetate (EVA). The material is characterized by thermo-mechanical analysis (TMA) experiments. Utilizing time-temperature superposition techniques a master-curve is constructed and the coefficients for the Williams-Landel-Ferry (WLF)-function are determined. This experimental data is transfered into a numerical representation and validated with creep bending tests of glass-polymer-glass-laminates. In the final step the viscoelastic model is used for calculating the cell displacement during the lamination process, followed by thermal cycling. The results for thermal cycling are compared with an optical cell-displacement measurement within a photovoltaic (PV) module.