Researchers from the Case Western Reserve University and Turkey’s Gebze Technical University (GTU) have used engineering epidemiology and statistical-data analytics to develop new models for predicting how PET (polyethylene terephthalate) backsheets applied to solar modules deteriorate when exposed to various accelerated weathering conditions.
PET films are commonly used in the back of solar modules as a durable protective barrier for the electronic components and to protect people from getting an electrical shock.
The group of scientists claim that the modeling approach they have adopted provides reliable predictions of the changes in yellowing index and haze formation in the PET films when these are exposed to constant stressors and stress levels for a given exposure time.
Environmental stressors such as irradiance, heat, and humidity, the researchers say, are present in all climatic zones. These stressors drive degradation of polymeric components in PV modules and contribute to performance loss. PET, in fact, is highly susceptible to moisture and ultraviolet (UV) irradiance. “PET degradation mainly occurs via photolytic and hydrolytic cleavage of an ester bond resulting in decreased molecular weight with concomitant changes in crystallinity, morphology, discoloration (yellowing) and/or haze formation,” the researchers explained.
The research team has identified multiple degradation modes that arise under multi-factor exposure conditions using statistically informed study protocols to produce datasets of step-wise observational variables to build physical and statistical models. Furthermore, the scientists have implemented a simulation methodology for PV modules’ service lifetime using temperature-dependent diffusion and permeation coefficients of polymer films cross-correlated with real-world time series climatic data.
The research, titled “Predictive models of poly (ethylene-terephthalate) film degradation under multi-factor accelerated weathering exposure”, was published in the scientific journal PLOS ONE.
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