Hail resistance of composite-based glass-free lightweight modules for building integrated photovoltaics applications

In this work, we manufacture lightweight (5 kg/m2) photovoltaic (PV) mini-modules for building integration replacing conventional glass sheets by a composite sandwich backsheet and a polymeric frontsheet. Our test devices are subjected to hail tests according to IEC 61215 and characterized electrically (to extract IV parameters) and by means of electroluminescence (EL) to visualize the hail-induced damages. The influence of both backsheet stiffness and frontsheet design on the hail test results are presented and discussed. Based on the results, two module design contributions to hail resistance are highlighted: i) a global energy dissipation, mostly related to the backsheet properties, is promoted by the deformation of the entire PV module structure and ii) a local energy dissipation occurs in the frontsheet under the hail impacts. These results clearly show that a balance between frontsheet design and backsheet stiffness has to be found in order to maximize hail resistance while minimizing the module’s weight. By combining the ideal backsheet structure with the proper frontsheet layer, we show that a rigid glass-free medium-area module can easily pass relevant hail test with less than 5% power losses.