Scientists at the U.S. Department of Commerce's National Institute of Standards and Technology claim that the root cause of solar panel backsheet degradation - from the EVA sealant in the solar cell to the chemicals in the backsheet itself - degrades at an accelerated rate.
A different kind of test
The researchers are trying to understand the causes of premature cracking of polyamide solar backsheets and how the polyamide material interacts with the solar panel structure. They have conducted chemical and mechanical tests on samples of solar panel backsheets used in the United States, China, Thailand and Italy. Most of them showed clear signs of premature rupture, they said.
The analysis also showed that the area of the substrate most affected by cracking and degradation was the inner layer, which tends to become harder.
EVA sealant
The scientists also found that damaging the chemicals in the solar cell sealant (ethylene vinyl acetate (EVA) film) and dripping onto the backsheet accelerated the degradation of the backsheet.
The scientists placed several polyamide test strips into bottles of acetic acid and then five months later analyzed their degradation compared to strips placed in air or water. Cracks resembling weathered negatives appeared on the surface of the plastic strips exposed to acetic acid. These cracks were much more severe than in the samples exposed to air or water, the researchers said.
"Acetic acid can greatly accelerate chemical degradation and promote the breakdown of the inner polyamide layer," the researchers concluded. "This study suggests that in situ cracking of polyamide solar backsheets can be attributed to a combination of chemical degradation and physical reorganization (chemical crystallization) under cyclic thermomechanical stress."
The scientists also noted that panels produced during the 2010-2012 period used primarily polyamide solar backsheets.
