The encapsulant is an integral part of a solar PV module, commonly referred to as a solar panel. Among other functions, it provides cushioning to the PV cells and binds them to the top surface (glass) and rear surface (glass or backsheet) of the module.
Over the years, two popular materials, EVA (Ethyl Vinyl Acetate) and POE (Polyolefin Elastomer), have been widely used for PV encapsulation. However, due to certain limitations associated with each material, encapsulation material suppliers have engineered a new solution called EPE (EVA-POE-EVA) encapsulant – a multilayer construction that combines the best properties of both materials.
In this article, we will explore the properties of EVA and POE encapsulants and how the EPE encapsulant addresses their shortcomings, as well as the increasing applications of EPE in modern cell architectures.
Limitations of EVA and POE
EVA is a thermoplastic polymer with superior adhesive properties and excellent optical transmission. However, it also has some drawbacks, such as low resistance to potential-induced degradation (PID).
Recognizing these limitations, module manufacturers turned to POE encapsulant, known for its high resistance to water vapour and PID, as well as its freedom from acid and free radical formation. However, POE comes with its own set of challenges, including a higher susceptibility to bubble generation during the lamination process, longer lamination time, and poorer adhesion to glass than EVA encapsulant.
EPE: Properties and Advantages
EPE encapsulant is a multilayer film consisting of a thin layer of POE sandwiched between two layers of EVA, produced through the co-extrusion process. This innovative construction aims to harness the best attributes of both EVA and POE encapsulants. The central POE layer acts as a superior water vapour barrier and also enhances the anti-PID performance, while the outer EVA layers provide improved adhesion to glass and PV cells. To prevent acid formation, manufacturers typically use specially developed acid-free EVA in EPE configurations.
Additionally, the lamination time for EPE is approximately 450 seconds, striking a balance between the 600 seconds required for EVA and the 300 seconds for single-layer POE. This optimized lamination time contributes to the overall efficiency of the manufacturing process.
Expanding Applications of EPE in Modern Cell Architectures
The advantages offered by EPE encapsulant in solar panels have led to its increasing adoption, particularly with emerging cell architectures like TOPCon. Some studies indicate that TOPCon cells are more susceptible to moisture ingress than PERC cells, making EPE a favourable choice in such scenarios.
EPE is also best suited for Glass-Glass solar panels that utilize PERC, TOPCon, or HJT cells.
As the solar industry continues to evolve, EPE demonstrates its potential to play a pivotal role in enhancing the performance and durability of solar PV modules.
Data Credits:
RenewSys R&D
Image Credit:
RenewSys