More Realistic Consideration of Backsheets Coefficient of Thermal Expansion on Thermomechanics of PV Modules

This paper deals with the effect of anisotropic and negative thermal expansion of polymeric backsheets. Even though these effects are well known in polymer engineering, so far they have not been considered in FEM simulation of PV modules. Therefore, we investigate the influence of those effects on the thermomechanical stress in PV modules after lamination and for mechanical load as well as thermal cycling. With the anisotropic partially negative coefficient of thermal expansion (CTE) the general shape of the third principal stress after lamination changes to a more asymmetric one. The probability of cell fracture after mechanical loading changes with the compressive stress after lamination. It ranges from 5 % for the AAA backsheet up to 55 % for the APA. This leads to the conclusion that the anisotropic, partially negative CTE of backsheets is not negligible and should be considered in all thermomechanical simulations of PV modules.