EVA or POE, how to choose the encapsulation film for photovoltaic double-glass modules?
Two popular encapsulation films for double-glass modules are called EVA and POE, which stand for ethylene-vinyl acetate copolymer and ethylene-octene copolymer, respectively. Which is the better option for double-glass components, EVA or POE? Currently, some manufacturers select EVA for packaging, other manufacturers pick POE for packaging, and some manufacturers are starting to employ EVA+POE hybrid packaging. People in the field should give it some thought.
The main component of a solar power generating system is a solar cell module, which is sometimes referred to as a solar panel or a photovoltaic module.
From the standpoint of packaging, photovoltaic modules—the essential component of solar power plants—can be separated into single-glass modules and double-glass modules. Double-sided batteries have expanded quickly alongside the growth of the solar energy generating sector. Currently available double-sided battery components are often packaged with double glass, while some are also available with transparent backplanes.
According to Bloomberg New Energy Finance (BNEF), bifacial battery modules will hold a market share of more than 90% by 2022. At the same time, double-glass modules will overtake transparent backplanes as the dominant product on the module market, while transparent backplane market share is still rather tiny.
The effectiveness of power generation and the lifespan of solar modules are directly impacted by the quality of battery packing. The packaging film is one of those that significantly affects PID function, and the choice of film material is crucial.
1.How is PID created?
Potential Induced Degradation, also known as PID (Potential Induced Degradation), is the term used to describe what happens when a significant amount of charge builds up on a battery's surface and eventually causes the surface to fail and collapse, which causes a sharp decrease in the power of the battery's internal components.
A rather high DC voltage is created between the battery sheet and the aluminum frame as a result of the necessity of grounding the aluminum alloy frame of the module for lightning protection applications. It is impossible for EVA to provide 100% insulation for packed components. During usage, water vapor enters the component through the backplane, silica gel, etc., causing the EVA to break down and form freely flowing acetic acid, which precipitates on the surface.
Alkali reaction produces sodium ions that are free to move. When an external electric field is present, the sodium ions travel to the battery's surface and collect on the anti-reflection layer, reducing the power of the module.
When moisture gets into the module, EVA breaks down with water to create acetic acid, which then combines with alkali to create sodium ions, which are then enhanced on the battery surface. The solar industry typically recognizes the PID phenomenon process as consisting of the four phases listed above. a reason for the PID effect.
2. What are EVA packing film's benefits and drawbacks?
EVA is the primary ingredient of EVA film, along with a number of additives, including a crosslinking agent, a thickening, an antioxidant, a light stabilizer, etc. Prior to 2014, EVA was the material of choice for packaging solar modules because of its superior packing performance, superior aging resistance, and affordable pricing. But its PID flaw is equally plain to see.
Double-glass modules appear to provide EVA the opportunity to overcome its inherent flaws. The low or zero water permeability of double-glass modules eliminates the issue with EVA's capacity to resist hydrolysis since the water vapor transfer rate of glass is virtually negligible.
It is currently unclear how to address the issues of water vapor penetration at the edge of double-glass modules and the ensuing subpar anti-PID efficacy.
3. Possibilities and difficulties with POE packaging film
POE is a novel kind of polyolefin thermoplastic elastomer with narrow relative molecular weight distribution, narrow comonomer distribution, and controlled structure that was created by metallocene catalysts. The water vapor transmission rate of POE is only approximately 1/8 that of EVA, the aging process does not result in acidic chemicals, it has good anti-aging performance, and it is a high-efficiency, high-reliability photovoltaic material. the preferred material for component encapsulation films.
Despite POE film's superior water vapor barrier and anti-aging capabilities, its market has not yet completely developed because of the expensive particle costs and subpar processing capabilities compared to EVA. Up until recently, backplane businesses that recognized the difficulty of double glass also contributed to the creation of POE film.
Since 2017, POE film sales have increased, prices have decreased, and the market share has continued to grow. Furthermore, POE has further got a favorable opportunity to conquer the market since 2020 as a result of the severe EVA scarcity and the sharp price increase. The majority of owners of double-glass power plants now specify POE film as the preferred material for double-glass modules.
4. Future: intense rivalry, unknowable!
However, the EVA movie also signaled a turning point at the time. End users tend to focus more on module pricing as a result of grid parity and subsidy reduction pressure. Some module makers have started using mixed EVA+POE packaging to cut costs or address the POE supply issue. In addition, double-glass components are now using framed designs due to the popularity of big silicon wafer components, and EVA has superior processing fluidity than POE. Some component producers think that EVA may be used for double-glass components with frames.
EVA film is frequently used for double-glass modules due to advancements in both EVA film production technology and cell anti-PID performance. The creation of POE films will benefit greatly from the strong competition that EVA film brings to the table. Businesses may encourage the expansion of the photovoltaic sector by accelerating cost reduction, improving efficiency, and lowering POE costs.
Having a high silane concentration, great transparency, a low crystal point, and the appearance of white particles, Coace R1020 is an olefin copolymer that has been silane-grafted.
Application examples: sticky film for encapsulating solar panels Glass cement