Material study of photovoltaic modules with silicone encapsulation after long-term outdoor exposure

In this study we analyze the properties of silicone elastomers used in the fabrication of PV modules in the early 1980's, which were in operation outdoors in a semi-tropical climate for more than 20 years. We observe that the silicone materials have very similar properties to recent, freshly cured silicone. The information gathered gives evidence that silicone elastomers undergo only very limited degradation after years of exposure in the field in operating PV modules. A moderate decrease in elastic modulus was observed, but further studies are needed to determine whether this effect is real. The very limited degradation of silicone encapsulant is consistent with the low performance decrease reported in other studies.