New technologies to reduce the carbon footprint of photovoltaic panels

In an eco-innovation approach, CEA-Liten and INES are developing several technologies to reduce the ecological footprint of photovoltaic panels. The first is based on the use of recycled glass and plant fibers, the second on a new assembly process, and the third is currently under construction.

In order for France to achieve carbon neutrality by 2050, the massive deployment of photovoltaic panels is essential to increase the share of renewable energies in the energy mix. By the end of 2021, the power of the French solar park will reach approximately 14 GW. In its forecast report on “(Transition) 2050”, Ademe indicated that it should reach a level between 92 and 144 GW in 2050. In front of this sector that is considered strategic, another challenge is at the level of relocation. of the manufacturing of the photovoltaic module sector in France and Europe, while it was largely dismantled in the 2010s, to be transferred to Asia. In this context, CEA-Liten and INES (National Institute for Solar Energy) are developing several technologies with the aim of reducing the carbon footprint of photovoltaic panels, while taking care to maintain their competitiveness.

The front of the module is made of recycled glass. Credit CEA-Liten/INES

A new module, with two particularities, is the subject of a proof of concept. The first, on its front face, is its incorporation of glass from a recycled panel. “Thanks to a mechanical process developed by CEA, we have shown that it is possible to disassemble the photovoltaic modules to recover the glass and return it to a new assembly cycle through lamination, explained Aude Derrier, Head of Department at CEA-Liten. We have proven that it does not cause damage to the product, and it makes it possible to achieve the same performance and the same durability as new glass. »

The back of the photovoltaic panel made of plant fibers in flax and basalt CEA-Liten/INES
The back part of the panel made of vegetable fibers in flax and basalt. Credit: CEA-Liten/INES

The second particularity concerns the rear face. Traditionally, they are designed with a three-layer film based on PET (Polyethylene terephthalate) and PVDF (Polyvinylidene fluoride), whose function is to provide protection against moisture penetration. Here, the researchers used a thermoplastic composite, which consists of a combination of plant fibers (flax and basalt) combined with a thermoplastic resin. Since flax tends to swell in the event of humidity, which causes the deterioration of the thermomechanical behavior of the photovoltaic cells – they are no longer in compression, but in traction -, the use of basalt has an effect of counteracting this phenomenon. And finally, this new rear face achieves the same level of durability and sealing as the standard panel.

Improve life cycle analysis of solar panels

In terms of photovoltaic efficiency, performance similar to standard products based on backsheet encapsulating glass was observed, regardless of the solar technology used: PERC (Passivated Emitter and Rear Contact), HJT (heterojunction), or TOPCon (Tunnel Oxide Passivated.Contact) . While the life cycle analysis (LCA) of this new product has been improved due to the reduction in the carbon footprint. ” We have obtained approximately between 50 and 80 kg of C02eq/kWp (kilowatt peak) compared to standard panels, said Aude Derrier. By comparison, the CRE (Energy Regulation Commission), which acts as the independent authority responsible for guaranteeing the proper functioning of the French energy markets, recommends the provision of panels whose carbon footprint is less than 550 kg of C02eq/kWp. »

In parallel with this new module, CEA-Liten and INES are developing a new process for manufacturing and assembling solar panels. Currently, the most used technology is vacuum membrane lamination. The researchers tested and proved the interest of a thermocompression process with induction heating. It has the advantage of accepting the use of new polymer materials and thermoplastic composites, and especially the results of recycling. “We are at the beginning of a new story in the way of manufacturing photovoltaic modules, especially by rethinking the whole eco-innovation strategy in a different way, rejoice in the specialist. The new assembly process will allow us to open up the field of possibilities in terms of materials. »

For example, it is possible to use recycled materials from the automotive industry, as is the case with polypropylene, and combine it with recycled carbon fibers. In the usual lamination process, the use of these materials is impossible. Induction heating produces a very rapid increase in temperature, up to 250 or even 270 degrees, and does not cause any damage to the photovoltaic cells, which makes it possible to maintain their performance and optimize the profitability of the industry . This new technology will also make it possible to incorporate larger quantities of thermoplastic composites in the production of modules, with the advantage of being reusable, unlike thermosettings.

In this approach to eco-innovation, CEA-Liten and INES are also conducting research with the aim of reducing the amount of silver in the modules by developing a new technology for interconnecting photovoltaic cells. “We are at the very beginning of this program, but I think we will achieve a proof of concept early next year”, concluded Aude Derrier.

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