Absorption and desorption of water in glass/ethylene-vinyl-acetate/glass laminates

Ethylene-vinyl-acetate (EVA) is used as the encapsulation polymer in photovoltaic (PV) modules to protect the sensitive parts of the module from the exterior environment. For many module types, exposure to water is an important lifetime-limiting factor. An important question is how quickly the EVA absorbs water in wet conditions and how fast water is desorbed when the module is at operational temperature in sunny conditions. In this work, the water penetration and escape rates in glass/EVA/glass laminates were compared. A question of particular interest was how sample temperature affects the escape rate. It was found that water desorption at 50 °C sample temperature is 16 times faster than absorption at room temperature, which implies that unsealed modules will dry out rapidly on sunny days. The implications of water absorption/desorption experiments for module design were also discussed.