A review of field performance of EVA-based encapsulants

As part of a past PVMaT contract (ZAG-3-11219-02-105661), several encapsulant formulations, developed for enhanced photothermal stability, were fielded at the STAR facility (Arizona) for long-term testing and observation. In all, 36 modules (4 different module manufacturers) have been evaluated. At the annual evaluation point, the modules had been exposed in the field for 4.5 years. Visual inspection and I-V measurements were made for each module. Upon inspection, all formulations designed to eliminate the discoloring mechanism appeared to be clear. The relative short-circuit current (I_sc) was measured for each module. For all module types, it was found that the dependence of the relative Isc with exposure time was the same for a particular module type, regardless and exclusive of the encapsulant formulation.