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Singapore Upcycles Old Solar Panels into Heat-Harvesting Electricity Materials

Image credits: ntu.edu.sg

Researchers from Nanyang Technological University, Singapore (NTU Singapore) and the Agency for Science, Technology, and Research (A*STAR) have created a technology that can transform old solar panels into a new, high-performance thermoelectric material that harvests heat and converts it into electricity.

“This study demonstrates that thermoelectrics is a fertile ground for upcycling defect and impurity-sensitive semiconductors,” says Dr Ady Suwardi, team lead from A*STAR’s Institute of Materials Research and Engineering (IMRE).

To identify the ideal combination of materials, scientists from A*STAR’s IMRE and the Institute of High-Performance Computing (IHPC) each contributed their area of expertise in computational modelling and material properties.

On the other hand, under the direction of Associate Professor Nripan Mathews, researchers from NTU’s Singapore-CEA Alliance for Research in Circular Economy (SCARCE) used their knowledge of recovering valuable materials from solar waste to create the technologies necessary for recovering silicon from solar panel waste.

The amount of waste produced globally from silicon in end-of-life solar panels is expected to reach 8 million tonnes by 2030 and 80 million tonnes by 2050 due to the rise in the usage of solar renewable energy over the past several decades and solar panels’ short 30-year lifespan.

Solar cells, which are the building blocks of solar panels and are composed of silicon, aluminium, copper, silver, lead, and a complicated mixture of other materials, are called solar cells. Due to the difficulty and expense of sorting and recycling such materials individually, current recycling techniques primarily salvage the glass and metallic support structures from solar panels.

Most silicon, which is in 90% of solar cells, ends up in landfills. Reusing silicon is hard because recycled silicon has impurities and flaws that can’t be used to make solar cells that work. This makes it hard to turn used silicon into solar cells or other technologies that use silicon.

This was a problem, but the team turned it into an opportunity by coming up with a way to turn old solar cells into better thermoelectric material. Unlike solar cells, this technology takes advantage of the different properties of thermoelectrics, where adding impurities and flaws makes them work better instead of worse.

The scientists first used ball milling technology to grind solar cells into a fine powder to impart thermoelectric properties such as power conversion and cooling efficiency to discarded silicon and to improve the performance of the upcycled silicon-based thermoelectrics. After that, phosphorus and germanium powder were added to change their original properties before the powder mixture was treated using spark plasma sintering at high heat and temperature.

This initiative brought attention to the interconnected study by SCARCE that involves A*STAR recycling silicon recovered from solar panel trash into silicon-based thermoelectrics for generating electricity from heat.

The group will also try to test a technique for large-scale recycling of waste silicon, which can be used for high-temperature energy harvesting applications like generating power from waste heat from industrial processes.

This research partnership demonstrates NTU’s dedication to its 2025 Strategic Plan, which places a strong emphasis on sustainability and innovation for a circular economy. The NTU Sustainability Manifesto, which sets the university’s direction towards sustainability, carbon neutrality, and societal impact, is also supported by this.

This initiative fits in with A*STAR’s initiatives to create environmentally friendly approaches to waste management and energy efficiency. Researchers have demonstrated that by utilising resource recovery techniques and working with A*STAR, it is possible to produce valuable materials of high quality and useful in the production of renewable energy components.

To achieve the objectives of developing a circular economy—creating sustainable materials, extending the lifespan of diverse products, and reducing waste—researchers must collaborate with local higher education institutions and other members of the R&D ecosystem.

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