Moisture-resistant module design

Moisture-resistant module design means choosing module designs, and pairing them with installation practices, that limit how much moisture reaches the cells. Its purpose is to prevent severe metallization corrosion. It targets the main corrosion route: when the encapsulant, usually EVA, is exposed to heat and water, it breaks down and releases acetic acid. That acid attacks busbars, ribbons, solder bonds and gridlines. Key design choices are an encapsulant that holds back water ingress and tolerates heat, and a suitable backsheet. Options include backsheets with an aluminium foil layer as a moisture barrier, or glass on the back of the module. A glass-glass module with an edge seal that works as a moisture barrier needs far longer damp heat exposure before moisture ingress shows up than a module with a standard polymer backsheet. Standard backsheets do not block moisture. Barrier materials alone are not enough, because good adhesion, interfaces, edges and junction box openings all control where moisture gets in. Delamination opens faster paths for water and speeds up corrosion. Glass-glass construction does not by itself stop moisture ingress. One glass-glass design whose encapsulant did not adhere well delaminated and corroded in the field. Vapour barriers can also trap reaction byproducts inside the module, which can increase corrosion or cause blisters. Standard qualification testing (IEC 61215) may not reveal these problems. In plants already in service, this design approach goes alongside replacing badly corroded modules and finding out how water is getting in.