Two frequently utilized encapsulating films for double-glass modules are EVA (ethylene-vinyl acetate copolymer) and POE (ethylene-octene copolymer). These days, some producers package their products using EVA, some with POE, and some are beginning to use hybrid packaging that combines POE and EVA. Therefore, is it better to choose POE or EVA for double-glass modules? For those working in the field, it is something to consider.
The main component of a solar power generation system is a solar cell module, sometimes known as a solar panel or photovoltaic module. Their job is to transfer solar energy into electrical energy so that it can be stored in the battery or used to power a load.
Photovoltaic modules, the main component of solar power plants, are separated into two categories based on how they are packaged: single-glass modules and double-glass modules. Bifunctional cells have advanced quickly along with the solar power generation industry. The majority of bifacial cell components on the market today are packaged with double glass, while some also have transparent backplanes.
According to Bloomberg New Energy Finance (BNEF), bifacial battery modules will have a market share of more than 90% by 2022. In the meantime, double-glass modules will take over as the most popular type of module, with transparent backsheets having a comparatively limited market share.
The longevity and power generation efficiency of solar modules are directly impacted by the quality of battery packaging. Among these, PID and other performances are greatly influenced by the packaging film, thus choosing the right kind of film is essential.
What forms a PID?
The term PID, or potential induced degradation, refers to the process wherein a significant quantity of charge builds up on the battery’s surface, rendering it inefficient and producing a sharp decrease in the battery component’s power.
The aluminum alloy frame of the module must be grounded in order to comply with lightning protection engineering requirements, and a comparatively high DC voltage forms between the aluminum frame and the battery cells. It is not possible for EVA to achieve 100% insulation for packaged components. Water vapor enters the component during usage through the back sheet, silica gel, and other layers, breaking down the EVA and releasing free-moving acetic acid that precipitates on the glass surface. The sodium ions created by the alkali reaction are free to move. When an external electric field is applied, the sodium ions travel toward the battery’s surface and gather in the layer that acts as an anti-reflection, which lowers the module power.
What are EVA packing film’s benefits and drawbacks?
EVA plus a variety of additives, including thickeners, cross-linking agents, antioxidants, light stabilizers, etc., make up the majority of EVA film. Before 2014, EVA was the material of choice for packaging solar modules because of its low cost, superior aging resistance, and outstanding packing performance. However, its PID flaws are also very clear.
The potential to overcome EVA’s intrinsic flaws appears to be provided by the development of double-glass components. The low or nonexistent water permeability of double-glass components eliminates the issue of EVA’s hydrolysis resistance because glass has an essentially nil water vapor transmission rate.
The issues of water vapor penetration at the edge of double-glass modules and the ensuing subpar anti-PID efficacy, however, remain unsolved.
The advantages and difficulties of POE packaging film
POE is a novel kind of polyolefin thermoplastic elastomer having a restricted distribution of comonomers, a narrow relative molecular mass distribution, and a controlled structure, which was developed from metallocene catalysts. POE is a highly effective ion and water vapor barrier. Merely 1/8 of the EVA is transmitted via water vapor. It has outstanding anti-aging qualities and doesn’t age by producing acidic compounds. It is a highly dependable and efficient photovoltaic The material of choice for films encasing components.
POE film has superior moisture barrier and anti-aging qualities, but because of its high particle cost and subpar processing performance compared to EVA, the POE market has not yet been fully opened. Up until recently, backplane manufacturers who experienced the difficulties posed by double glass also contributed to the creation of POE film.
POE film has seen an increase in volume and a fall in price since 2017, although its market share has remained steady. Furthermore, starting 2020, POE has had a great chance to take market share as a result of significant EVA shortages and sharp price rises. These days, POE film is practically universally used for dual-glass modules, and many owners of
The future is yet undetermined and faces tough competition!
But EVA film is currently approaching a tipping point as well. End users are typically more aware of component costs due to the pressure of more economical Internet access and fewer subsidies. In order to cut expenses or deal with POE supply problems, some component makers have started to use mixed packaging techniques of EVA and POE. Concurrently, double-glass modules have started to employ frame designs due to the growing popularity of big silicon wafer modules; EVA offers superior processing fluidity compared to POE. Certain module manufacturers maintain that EVA can be used with double-glass modules that have frames.
Using EVA film for double-glass modules is a good idea because of the advancements in both EVA film production technology and battery cell anti-PID performance. POE film production will benefit more from the strong competition that EVA film has brought to the table. Companies lower POE costs, expedite cost reduction and efficiency enhancement, and support the expansion of the solar sector.
