The effect of storage conditions on the long-term stability of ethylene-vinyl-acetate (EVA) copolymer used in glass/glass modules

We evaluate the effect of storage conditions of uncured encapsulant rolls and the potential consequences on photovoltaic (PV) module performance. We show the impact of residual water trapped inside laminated double glass PV modules after lamination and during UV exposure. We focus on ethylene vinyl acetate (EVA) copolymer and its stability over 630 kWh/m2 UV exposure (equivalent to 10 years of outdoor exposure in a Central European country). Three storage conditions were tested by simulating different moisture contents to mimic relative humidity variations that can occur when polymeric foils are exposed to an uncontrolled envi-ronment, such as the PV module production line, next to the laminator machine. The presence of water during lamination had no apparent impact on module quality and performance after the fabrication but only became apparent during the aging test. The module power loss was directly related to the EVA chemical and physical degradation and varied depending on the storage history. Results indicate that when the storage is not too harsh, its effect can be somehow mitigated. Based on our observations, we leave a door open to the adoption of high-quality EVA polymers in the manufacturing of glass-glass modules. However, the storage and handling conditions prescribed by the supplier should be carefully respected.