Recycling solar panels and circularity

The vast majority of today's solar panels are poor candidates for recycling because of the way they are made. TNO wants to change that. Indeed, recovering and reusing components and materials avoid wasting energy and critical raw materials. European and US solar cell and module manufacturers can thus also offer an alternative to modules made in Asia.

Optimal dismantling

‘For us, research focused on design for recycling of solar panels started four years ago’, says Martin Späth, senior consultant and project manager for PV technology at TNO. ‘In that, we were unique. Not many parties were focused on that yet, especially where the actual development of new products was concerned. The major problem in solar panel recycling - and this always precedes circularity - is posed by the encapsulant. This anchors the solar cells firmly in the module. At the same time, it makes optimal dismantling of end-of-life modules extremely difficult. We came up with a solution.’

Release encapsulant

TNO, together with industrial partners, developed a new bonding layer for solar panels: the release encapsulant. The advantage - as the name suggests - is that it can be easily removed when recycling solar panels. This allows components and materials to be completely separated from each other, without complex energy-consuming and environmentally damaging processes. The release encapsulant is now being extensively tested and further developed for various solar cells.

Recyclable plastic

TNO is currently either leading or participating in six innovation projects on recycling and circularity of solar panels. First of all, Späth mentions PANGEA. This Dutch project is working on a silicon solar panel with a PFAS-free recyclable plastic backsheet and the release encapsulant. The idea is that components can be reused to produce new ones at the end of life. In addition, the possibility of replacing the solar cells during the operating phase with the next generation of better-performing solar cells is being explored, which obviously has implications for the environmental impact over the life of the module.

Optimal dismantling

‘In addition, we are working within international consortia on the recyclable solar panels of the future’, Späth says. ‘For example, we are testing our release encapsulant in applications in a tandem triple junction silicon solar panel with two perovskite top layers in the EU Horizon project TRIUMPH. In doing so, we are looking at optimal dismantling for component recovery. Another European project is PILATUS. In it, a pilot line will be built for the production of heterojunction Interdigited-Back-Contact (IBC) tunnel solar cells and panels. TNO focuses here on the application of non-fossil produced encapsulants and the use of our release encapsulant. All this is of course accompanied by critical raw material analyses and environmental impact assessments.’ Read more about project PILATUS.

Pioneering technology

Späth lists three more Dutch projects that focus on reusing discarded solar panels. This is how TNO initiated Si-nfinity. This focuses on optimising the environmental impact of solar panels by developing breakthrough technology for recovering silicon and other materials such as silver. HERO is all about reusing pv glass panels in a building-integrated pv application. And within 'Repair mend to be', the focus is on creating an innovative glass repair technique for damaged solar panels. Among other things, TNO can draw on its experience as developer of the repair material for the 'Carglass technology'. This, too, shows TNO to be a leading knowledge institute on recycling and circularity in the global solar market, according to Späth.

Big steps

Späth: ‘In this regard, the development of our release encapsulant was an absolute milestone. It does what it has to do. We are also exploring, through our industrial innovation partners, bringing it to market in different types of solar panels. We’re not there yet, but it is coming. We are also making great strides in the recovery of materials, such as silicon. In terms of purity, we are in a learning line towards solar grade quality and we are well on our way. We can already extract silicon from discarded modules suitable for reuse in car battery anodes. With such successes in the recycling and circularity of solar panels, the industry and research community really know where to find us by now.’

Part of society

The work of Späth and his colleagues is in the international spotlight. At the same time, he stresses that TNO is more than a developer of innovative technology. Among other things, he points to cooperation with governments, for example in relevant policy-making for building a recycling chain for PV glass. ‘We also advise startups and large companies at home and abroad that want to test their ideas in recycling and sustainable products. And together with the OPEN Foundation, for example, we did a cost-benefit analysis for contemporary solar panel recycling. In short, we also have our role on the financial-economic side of things, as a knowledge institute that is part of our society and wants to take social responsibility.’

Header photo: Niels van Loon (TNO)