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Influences of Different Backsheet on PV Module Reliability and Durability in High Humidity Environment for the EU PVSEC 2019
H. Gong, M. Gao, Y. Guo
Activation Energies, Backsheet, Module Reliability, WVTR, High Humidity
Photovoltaic Modules and BoS Components
Subtopic: PV Module Design, Manufacture, Performance and Reliability
Event: 36th European Photovoltaic Solar Energy Conference and Exhibition
Session: 4AV.1.54
1098 - 1101
ISBN: 3-936338-60-4
Paper DOI: 10.4229/EUPVSEC20192019-4AV.1.54
0,00 EUR
Document(s): paper, poster


Most commercial crystalline silicon modules are encapsulated with ethylene-vinyl acetate (EVA) and polymer backsheets to provide protection against environmental exposure. EVA is a moisture sensitive material in which a hydrolysis reaction will occur to produce acetic acid in the presence of heat and moisture. However, polyester backsheets cannot completely block the moisture ingress into the module. So, the hydrolysis reaction of EVA is inevitable. But different polyester backsheets have different water vapor transmission rate (WVTR). At present, there is no definite conclusion about the WVTR selection of backsheets in tropics area. The most common practice in the PV industry is to assess the backsheet's suitability for the tropics through extended damp heat testing. In this work, first we investigate the degradation of modules with different backsheets through extended 3000hrs damp heat test, and correlate this to the backsheet WVTR. The results showed that the double glass modules and the modules without backshseet have lowest power degradation. For double glass module, almost no moisture can ingress into the modules and also no hydrolysis reaction occurred. For the modules without backsheet, although the hydrolysis reaction occurred, the acetic acid also can release totally. For the modules encapsulated with backsheet WVTR of 0.6g/m2.day, 1.25 g/m2d·ay, 2.34 g/m2d·ay, 3.30 g/m2d·ay, the power degradation increased with the WVTR. Then, we also analyze the failure mechanism of the modules installed in the tropic area and the modules after received extended damp heat test using FTIR. We found that these modules have similar failure mechanism. Lead acetate can be detected on the EVA. So the modules’ failure activation energy in the tropic area can be obtained. Then we can use Hallberg-Peck model to calculate the different indoor extended damp heat testing time at different temperature and relative humidity area.