Advancements In Solar Backsheet Technology

Innovations In Backsheets Segment Enhances Efficiency, Aesthetics And Sustainability In Photovoltaic Modules

Advancements In Solar Backsheet Technology

Polymers for the front: White glass can be replaced by backsheets as the rear cover of the module, backsheet makers, like Coveme, try to attack glass on the front side by offering polymer based frontsheets. (Source: Coveme)

In addition to the core technology developments discussed in our previous articles on solar backsheet (see Latest Trends In Backsheets), manufacturers of this solar module process materials are also actively improving their products. This article summarizes such developments and views of leading backsheet makers on various other topics.

Front sheet: While it is too early to say if this is already a trend, several players in the backsheet segment are working on polymer based front sheets to replace the glass. While Coveme was the first among the backsheet suppliers to make such a product available, a few more have launched similar products(see Backsheets Supporting Sustainability). An interesting one is DuPont’s recently launched Tedlar-based front sheet solution, and a few backsheet makers are also offering such front sheets for flexible modules, according to Oakland Fu, global marketing manager for PV application at DuPont.. The front sheet facilitates high transparency and good UV resistance with a tested 20,000 hours of UV aging. Fu says that the product has gained attention from a few module makers for developing flexible and lightweight modules for BIPV as well as for specific rooftop projects requiring low weight. While the traditional module has a weight of 15 kg/m2, the flexible module with the front sheet weighs less than 5 kg/m2, said Fu.

Jolywood says that demand for such front sheets has grown stronger since 2022. According to CTO Zhang, it is already mass producing a product that weighs only 3.5 kg/m2 – a mere 1/5th of a comparable standard module. Such products are mainly suitable for roofs with low load-bearing requirements, curved roofs and portable energy storage devices, adds Jolywood’s CTO Fute  Zhang.

Féron is also offering a front sheet for specialty applications where glass cannot work, and Michael Robertz, Sales Manager at Feron, says it is a “big market” for the company. China’s Suzhou Hondol New Material Limited, providing inputs for the first time (not with the product data tables), is mainly in the manufacture of CPC-based backsheets, but also supplies front sheets made of glass fiber. The product weighs 5 kg compared to 30 kg for a similar module based on the glass-glass configuration, says Tongxin Wang. Currently, the front sheet made of fiberglass is twice as expensive as glass, but with more and more module makers accepting it, the price difference can be brought to parity, he adds. Fumotech is another company that has front sheet solutions on offer.

Non-fluoropolymers: Starting with Féron in this subsection on non-fluoropolymer products, the company highlights the benefits of its polyolefin based backsheet, which according to the company exhibits excellent UV resistance as indicated by 15,000 hours of weathering test and 8,000 hours of damp heat test, comparable to any fluoropolymer films. High reflectivity of above 90% is another feature highlighted by the company, and it is also working on a high reflective black backsheet. This product range is based on a monolayer construction, thus immune from interlayer delamination.

Crown is mainly promoting its BO range of backsheets, launched in 2012. The product range follows the structure of PET/PO or PET/PU. According to Crown, PO film has better water vapor barrier and insulation performance than coatings, which can effectively protect cells and ribbons from water vapor erosion. The PO film also exhibits superior UV and hydrolysis resistance. The BO product range was mainly promoted to overseas clients with high environmental protection standards such as Q CELLS, REC, LGE, SunPower, Vina Solar and many more. However, the product range also found a local market in 2018, while the rise in PVDF prices has accelerated the reach to mainstream module makers. product. Crown claims most of the leading Chinese module makers in China are using its BO range in larger quantities. With no complaints registered so far, Crown takes this as a demonstration of 10 years of outdoor performance and a testimony for the proven reliability

Backsheets for advanced cell structures: The PV industry is commercializing advanced cell architectures such as TOPCon, HJT and IBC. Some of these technologies are more sensitive to moisture ingression compared to standard PERC. Backsheet makers are now introducing products with WVTR barrier technology. Coveme’s dyMat barrier film backsheets additionally contains an integrated PET barrier layer with an additive, resulting in a low WVTR of 0.3 g/ m2.d. These laminates were specifically developed for HJT cells and floating systems with all types of cells. The product’s important characteristic is that the backsheet structure does not utilize an aluminum sheet to achieve low WVTR values. Therefore, not only does the module production process remain unchanged, but the transparent variant can also be used for bifacial modules. The backsheet is available in white or black and has a maximum system voltage of 1,500 V. Most of the leading backsheet companies are working on, or are already offering, high barrier films with and without aluminum with a WVTR of about 0.5 g/m2.d and close to zero, respectively.

Endurans also says its PP based backsheet provides better moisture barrier property over the PET based products. The company is working with partners and labs to demonstrate benefits of the coextruded PP backsheet compared to other materials and even glass-glass.

Reflective black backsheet: Black backsheets are commonly used by module manufacturers to improve aesthetics. Such modules have been favorably received in the European residential markets. These black modules, however, cannibalize power and efficiency of the modules since there is no reflection of the light that hits the cell spaces due to the intrinsic light absorption of the black color. Nearly every leading company, including Cybrid, Jolywood and Hangzhou First, are working on reflective black backsheets that solve this problem to an extent. Coveme provided some additional details on such a product. It has created a mono-layer PET-basedThe technique can also be implemented on to the company’s other backsheet configurations as well. Interestingly, all of these latest product advancements from Coveme discussed in different sections can be combined into a single product, implying that Coveme can provide a reflective black backsheet with a low WVTR made from recycled PET. Cybrid is also offering such backsheet with 55% reflectivity, and Stepen Gong, Senior Product Manager, cybrid also presented the test results at the TaiyangNews conference, which show that the use of reflective black backsheets result in power gains of 2.15% in a bifacial module (see Cybrid’s presentation recording here).

Coveme is working a lot in the direction of sustainability. As part of this effort, the company has published a life cycle analysis (LCA) report on its backsheet (see Protecting Solar PV Panels & Planet).

RenewSys has started an interesting program called Dr. PV where the company offers free service to the modules for critical performance and reliability parameters in terms of TUV, IEC or any other test parameters. Separately, Dow is also offering a flowable silicone sealant solution that can be sprayed onto the degrading backsheets as a repairing solution.

The article is an excerpt from the TaiyangNews Market Survey on Backsheets and Encapsulation 2022-23, which can be accessed free of charge here.

About The Author

Shravan Chunduri

HEAD OF TECHNOLOGY Shravan is a name to reckon with in the solar industry. Having caught the solar bug very early in his career, he began his journey 20 years ago in research, followed by stints in solar manufacturing. He then moved on to write and eventually ventured into Consulting. At TaiyangNews, he is responsible for drafting the technology reports and articles that are regularly published in TaiyangNews, apart from hosting the Conferences and Webinars that TaiyangNews conducts. [email protected]

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