Modelling the non-isothermal curing kinetics of peroxide crosslinking polyolefin copolymers for photovoltaic module lamination

This study presents a model for determining the non-isothermal curing kinetics of peroxide crosslinking polyolefin copolymers used for encapsulation of silicon solar cells in photovoltaic modules. Therefore, rheological data of ethylene vinyl acetate copolymer (EVA) and polyolefin elastomer (POE) were analyzed. The curing kinetics were described assuming a temperature dependent Arrhenius rate coefficient and implementing a reaction rate model. Validation was performed under isothermal and non-isothermal conditions. An excellent agreement of experimental and model data was ascertained. The model was used to determine the non-isothermal crosslinking conversion during lamination of EVA or POE based photovoltaic mini-modules. Temperatures were tracked by positioning seven sensors within the mini-modules. Moreover, a thermal simulation model was implemented. Also on module level, the experimental results corroborated the simulated data. A lamination temperature of 150 °C led to insufficient curing of POE based modules. Similar conversion rates were achieved for EVA and POE encapsulants at 150 and 160 °C, respectively.