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Degradation Mechanism Analysis of Damp Heat Aged PV Modules
H. Gong, G. Wang, M. Gao
Backsheet, Durability, WVTR, Damp Heat (DH), PV Module, PCT
Components for PV Systems
Subtopic: PV Modules
Event: 27th European Photovoltaic Solar Energy Conference and Exhibition
Session: 4BV.3.38
3518 - 3522
ISBN: 3-936338-28-0
Paper DOI: 10.4229/27thEUPVSEC2012-4BV.3.38
0,00 EUR
Document(s): paper


Photovoltaic (PV) modules lifetime are desired to be greater than 25 years, however the industry standard IEC61215 tests are only designed to identify early failures within the first five years of operation. Therefore accelerated aging tests are required. Extended Damp Heat (85°C/85% relative humidity) and PCT (Pressure Cooker Test) tests have been carried out to assess long-term durability of PV modules, and further analyze the relevant degradation mechanisms. Most crystal silicon photovoltaic modules are encapsulated with ethylene-vinyl acetate (EVA) and Tedlar-Polyester backsheets to provide protection against environmental exposure. However, EVA is a moisture sensitive material in which an hydrolysis reaction will occur to produce acetic acid in the presence of heat and moisture. This reaction results in reduced the PH concentration inside the module that accelerates metallic corrosion that leads to significant output power degradation. The backsheet is a barrier to prevent moisture from getting into the modules, hence the WVTR (Water Vapor Transmission Rate) is an important factor to minimize this degradation mechanism. This work investigates the degradation of modules with different backsheets and EVAs, and correlates this to the backsheet WVTR. The extended Damp Heat and PCT tests were applied, and the modules were periodically analyzed for degradation by recording their performance by pulse solar simulator and EL (electroluminescence) imaging.