The yellowing effect of photovoltaic modules is the reflection of EVA encapsulant degradation. In general, EVA discoloration is considered to reduce modules’ efficiency. The question is, what is the electrical performance of yellow modules? Fraunhofer and National Renewable Energy Laboratory have been studying this problem for many years.
Can EVA be replaced in solar panels?
EVA is definetely the most popular encapsulant used in solar modules (90% market share) and this trend should continue (although can drop to 60%).
When EVA degrades, it becomes yellow since it goes through a chemical reaction where acetic acid is produced. It is followed by UV absorber breaking down and an increase of gel content.
Sometimes cheaper and less durable EVA is sometimes used to reduce costs as encapsulant is a major cost component in solar panels. However, the backsheet and EVA are both important as protective barriers that can affect the module’s durability, and substitutions of lower quality EVA material may reduce the lifetime of the module due to EVA yellowing and consequent power loss.
How yellowing affects solar panels?
In general, EVA discoloration is considered to reduce solar panels efficiency by 9 to even 50%. Some studies show however that yellowing is only an aesthetic problem, blaming reduction of efficiency on hot spots produced due to multiple hot soldering joints.
The cycle of studies conducted by Fraunhofer and NREL lead to following conclusions:
– the acetic acid released when EVA is degrading may cause corrosion in solar panels
– reduction of efficiency in UV-exposed EVA is most noticeable for wavelengths of 350-950 nm
– reduction of quantum efficiency in UV-exposed EVA is most noticeable for wavelengths of 350-650 nm
– if solar cell efficiencies increased at lower wavelengths there could be increased power losses due to yellowing
– EVA material needs to advance together with photovoltaic technology
How to avoid yellowing in solar panels?
Yellowing effect is caused by UV radiation, therefore it cannot be avoided because solar panels have to be exposed to solar radiation to produce energy. It is however advisable not to buy the cheapest modules on the market, where components costs were reduced by implementing cheaper and less resistant EVA.