EVA or POE, how to choose the encapsulation film of photovoltaic double glass module?

GWELL as EVA film extrusion line manufacturer, As the core equipment of photovoltaic power station, photovoltaic module can be divided into single glass module and double glass module from the perspective of packaging. With the development of photovoltaic power generation industry, double-sided batteries have developed rapidly. At present, most double-sided battery modules in the market are packaged with double glass, and a few are packaged with transparent backsheet.

According to reliable market research data, by the end of 2022, the market share of double-sided battery modules will exceed 90%. At the same time, the market share of transparent back sheet is relatively small, and double glass components will become the mainstream of the component market.

The quality of battery packaging directly affects the power generation efficiency and service life of photovoltaic modules. Among them, the packaging encapsulation film has a significant impact on the performance of PID, and the selection of encapsulation film material is very important.

How is PID formed?

The full name of PID (potential induced degradation) is potential induced attenuation, which means that a large number of charges gather on the battery surface, causing the battery surface to collapse and fail, resulting in a sudden drop in the power of the battery module.

Due to the needs of lightning protection engineering, the aluminum alloy frame of the module requires grounding, and a relatively high DC voltage is formed between the battery and the aluminum frame. For EVA packaging components, EVA cannot achieve 100% insulation. In the process of use, water vapor penetrates into the interior of the components through silica gel and backsheet, causing EVA to decompose and produce free moving acetic acid. Acetic acid reacts with the alkali precipitated on the glass surface to form free moving sodium ions. Under the action of external electric field, sodium ions move to the battery surface and gather in the antireflection layer on the battery surface, resulting in the reduction of module power.

When water vapor enters the module, EVA decomposes with water to produce acetic acid, acetic acid reacts with alkali to produce sodium ions, and sodium ions are enriched to the battery surface. The above four steps are the whole process of forming PID phenomenon, which is also a widely recognized cause of PID effect in the photovoltaic industry.

China Gwell Machinery Co., Ltd. Factory show

What are the advantages and disadvantages of EVA packaging film?

The main component of EVA film is Eva, plus various additives, such as crosslinking agent, thickener, antioxidant, light stabilizer, etc. EVA has become the preferred material for photovoltaic module packaging before 2014 because of its excellent packaging performance, good aging resistance and low price. But its PID defect is also obvious.

EVA POE Solar Film Extrusion Line is used for solar cell packaging. It is a durable and reliable packaging material. China Gwell’s EVA/POE/EPE packaging film extrusion production line is in the leading position in the world.

GWELL as EVA film extrusion line manufacturer,The emergence of double glass components seems to give EVA the possibility to overcome its natural defects. Because the water vapor transmittance of glass is almost zero, the low water permeability or zero water permeability of double glass components makes the hydrolysis resistance of EVA no longer a problem.

However, how to solve the problems of water vapor infiltration at the edge of double glass module and the resulting poor anti PID performance still can not get a positive solution.

Opportunities and challenges of POE packaging film

POE, developed from metallocene catalyst, is a new polyolefin thermoplastic elastomer with narrow relative molecular weight distribution, narrow comonomer distribution and controllable structure. Poe has excellent water vapor barrier ability and ion barrier ability. The water vapor transmission rate is only about 1/8 of that of EVA. It will not produce acidic substances during aging. POE has excellent anti-aging performance. It is the preferred material for high-efficiency and high reliability PV module packaging film.

Although POE encapsulation film has better water vapor barrier ability and better anti-aging performance, the market of POE has not been fully opened due to its high particle cost and lower processing performance than EVA. Until recent years, backsheet enterprises that feel the challenge of double glass have also joined in the development of POE encapsulation film.

Since 2017, the volume and price of POE film have increased and the market share has been increasing. Moreover, since 2020, due to the serious shortage of EVA and the rapid rise of price, POE has further obtained a good opportunity to occupy the market. At present, POE encapsulation film has almost become the mainstream choice of double glass components. Many owners of double glass power stations have designated POE encapsulation film at the bidding stage.

GWELL factory workshop real shot

The future: fierce competition, still unknown!

However, at present, EVA encapsulation film has also ushered in a turning opportunity. Under the pressure of cheap internet access and reduced subsidies, end customers generally pay more attention to component prices. At present, some component factories have begun to adopt EVA + POE (what we called EPE) combination packaging to reduce costs or cope with POE supply shortages. At the same time, with the popularity of large silicon wafer components, double glass components began to use frame design, and the processing fluidity of EVA is better than POE. Some component manufacturers believe that double glass components with frames can use EVA.

With the further improvement of the anti-PID performance of the battery and the production technology of EVA encapsulation film, it is not necessary to use EVA encapsulation film for double glass components. The benign competition brought by EVA encapsulation film to POE encapsulation film will be more conducive to POE encapsulation film manufacturers to accelerate cost reduction and efficiency increase, reduce POE cost and promote the further development of the photovoltaic industry.

what can China GWELL help you?

GWELL has more than ten years of producing EVA and POE encapsulation film extrusion line, and owns 90% market share of machine in this industry. We helped a lot of clients to choose and upgrade the machine. And the machine line speed is always leading by GWELL in this industry. Thus, we have an absolute say in equipment selection. That is what we can promise and we can help you wipe away your doubt. So whether you want to buy the machine or not, you are welcome to contact our manager to get the latest news in this industry.

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