Evaluating Durability of a Double Edge Sealant in a Floating Photovoltaic Application

Moisture ingress into photovoltaic (PV) modules is one of the main drivers behind module midlife- and wear-out-failures, particularly when modules are installed in locations with high humidity stress. To minimize moisture ingress, impermeable front- and backsheets in combination with an edge sealant around the module perimeter can be used. Besides low water vapor transmission rates through the sealant material, mechanical durability of the sealant is of utmost importance. In this work, we assess the durability of a double edge sealant design used in a floating PV (FPV) concept in which the float and PV module are integrated. Strength of attachment testing, combined with measurements of failure type, are performed on samples taken from an FPV prototype after outdoor exposure and are compared to measurements on lab samples that are unexposed or exposed to indoor accelerated stress. We observe a significant decrease of lap shear strength for the double edge sealant after field exposure, coupled with more adhesive failure. Correlation to accelerated stress test results indicates that the observed adhesion losses can partly be attributed to degradation driven by ultraviolet light. By reporting on observations of FPV field degradation and exploring how indoor accelerated stress testing can be used to understand the origins of the observed degradation, this work constitutes an important early contribution to the field of FPV reliability.