Reliability of EVA modules

The issue of the long term reliability of photovoltaic (PV) modules made with ethylene vinyl acetate (EVA) encapsulant is discussed, particularly in reference to the yellowing or darkening observed after long term exposure to high temperature and high illumination levels. Observations of the results of long term exposure of Solarex modules at a number of field sites is reported. Laboratory results on high temperature exposure of EVA and long term exposure of the cell metallization to acetic acid is presented. None of these tests explain the fill factor loss observed in the Arco modules at Carrisa Plains. Detailed examination of a number of Carrisa modules has shown that a major contributor to the power loss is failure of the back interconnects, independent of any EVA degradation