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 employ hybrid packaging made of EVA and POE. Therefore, is it better to select 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 generating system is a solar cell module, often known as a solar panel or photovoltaic module. Their job is to transfer solar energy into electrical energy so that it may be stored in the battery or used to power a load.

PV

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 generating sector. The majority of bifacial cell components on the market today are packed with double glass, while some also include transparent backplanes.

The longevity and power generation efficiency of solar modules are directly impacted by the quality of battery packing. Among them, 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.
Due to the demands of lightning protection engineering, the aluminum alloy frame of the module is needed to be grounded, and a relatively large DC voltage is created between the battery cells and the aluminum frame. It is not possible for EVA to provide 100% insulation for packed 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.

EVA breaks down into acetic acid when it comes into contact with water vapor in the component. Sodium ions are created when acetic vinegar and alkali mix, and these ions are concentrated on the battery’s surface. The solar industry now generally recognizes the four phases listed above as the whole process of the genesis of the PID phenomenon. the root of the PID impact.

What are EVA packing film’s benefits and drawbacks?

The fundamental component of EVA film is EVA, with additional additives, such as cross-linking agents, thickeners, antioxidants, light stabilizers, etc. 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, there are also clear PID shortcomings.

The potential to overcome EVA’s intrinsic flaws appears to be provided by the development of double-glass components. Since the water vapor transfer rate of glass is virtually nil, the low or zero water permeability of double-glass components makes EVA’s hydrolysis resistance no longer an issue.

Modules with two panes of glass withstand corrosion better.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 using metallocene catalysts. POE is a highly effective ion and water vapor barrier. There is no production of acidic chemicals during the aging process, and the water vapor transmittance is only around 1/8 of EVA. It’s an efficient and dependable photovoltaic system with great anti-aging qualities. The recommended material for component encapsulation films.

POE

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 a growth 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. POE film is currently almost the standard option for dual-glass modules, and a lot of dual-glass power station owners select POE film when it comes to bidding.

The future is yet undetermined and faces tough competition!

But EVA film is currently approaching a tipping moment as well. End users are typically more aware of component costs due to the pressure of more economical Internet access and less subsidies. In order to cut expenses or deal with POE supply problems, several 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 may be used with double-glass modules that have frames.

Using EVA film for double-glass modules is a good option 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.