Yellowing in PV Modules: Causes and Prevention
Solar photovoltaic (PV) modules, commonly known as solar panels, have become a promising source of renewable energy, harnessing sunlight to produce clean electricity.
However, like any technology, PV modules are susceptible to wear and tear over time, and one issue that may arise is the yellowing of PV modules, which can cause concern for solar panel owners.
What is yellowing of PV modules?
Yellowing of PV modules refers to the optical degradation of ethyl vinyl acetate (EVA), a material used as an encapsulant on the panel, causing the once-clear encapsulant to become visibly yellow or even brown.
Apart from its aesthetic impact, yellowing affects the output and performance of the panel due to the high absorption of light in the EVA film.
Causes of yellowing in PV modules
The primary cause of yellowing in PV modules is the degradation of EVA due to an uncontrollable chemical reaction from materials within the panel. Most solar panels use EVA as an encapsulation material to shield the solar cells from environmental factors such as moisture and dust. However, as the EVA degrades, it begins to turn yellow.
The two main reasons for yellowing are:
Acetic acid formation: Studies in the solar industry have revealed that acetic acid is responsible for turning the EVA encapsulate yellow. The chemical reaction occurs between the chemicals used in silicon solar cell surfaces and the chemicals used in treating the glass, particularly on the PV cell surface. As the yellow discoloration occurs, the UV absorbers in the EVA break down, and the percentage of cross-linked polymers increases, leading to the panel's inner layer discoloration.
Exposure to sunlight: While solar panels are designed to be exposed to sunlight, problems arise when the EVA is made from cheaper materials. EVA plays a crucial role in maintaining UV resistance in solar panels, preventing the ultraviolet rays from affecting the panels themselves. However, when lower-quality materials are used for EVA, its resistance to UV rays diminishes. Consequently, prolonged exposure to UV rays causes the EVA to turn yellow or brown, typically after the first few years of usage.
How to prevent yellowing?
Preventing yellowing in PV modules can be challenging, as it is often the result of low-quality EVA. The best approach to avoid this issue is to ensure that you purchase solar panels from a reputable manufacturer that uses top-quality materials for the backsheet and encapsulation.
Before buying solar panels, it is essential to inquire about the quality and expected durability of the EVA used. Choosing panels from trusted manufacturers can help ensure that the EVA will resist yellowing and maintain its transparency and efficiency over the years.