By 2045, Germany will have accumulated up to 5.6 million tons of spent solar panels. But instead of turning into waste, they could become valuable raw material for producing new solar panels. This proposal was put forward by scientists at Cologne Technical University in Germany, who have developed a deep recycling technology for photovoltaic modules. According to their calculations, using recovered materials could reduce the cost of producing new solar panels in Europe by 60–77%, while simultaneously cutting greenhouse gas emissions, water consumption, and the need for raw material extraction.
Today, most recycling facilities process solar panels mechanically, mainly extracting glass and aluminum frames. The most valuable components – silicon, silver, and copper – are either lost or contaminated to such an extent that they become unsuitable for reuse. Meanwhile, each ton of spent solar panels contains materials worth approximately €1,175. Nearly half of that value comes from just half a kilogram of silver, the price of which exceeds €1,100 per kilogram. Thus, current recycling technologies effectively leave the most expensive components unused.
To preserve these materials, German researchers proposed a deep recycling technology fundamentally different from existing methods. First, the solar panel is treated with short pulses of bright light, which allow the glass, aluminum frame, protective film, and silicon cells to be separated with virtually no damage. The solar cells are then immersed in a molten mixture of sodium and potassium hydroxides at around 200 °C, whereupon they are rapidly cooled. This enables the extraction of silver with 99.57% purity without the use of aggressive acids, while copper is separated electrochemically. In the final stage, the silicon is further purified by zone melting to achieve a quality suitable for producing new solar panels.
To process one ton of solar panels, the scientists needed only 148 kWh of electricity – roughly five times less than conventional pyrolysis, which heats panels up to 400 °C. Using materials recovered from one ton of spent panels, approximately 15 kilowatt-peak of new solar modules can be manufactured.
Calculations showed that using recycled materials would reduce the cost of producing new solar panels by 60-77% compared to using virgin raw materials. In the solar energy industry, cost is typically calculated per every watt of installed panel capacity. According to the researchers’ estimates, this figure could drop from the current €0.225 to €0.086 per one watt, and if recycling and production are organized within a single closed-loop system – to €0.05 per watt.
Underlying the economic advantages is a significant environmental impact. Since there is no need to extract and process a significant portion of raw materials anew, each ton of produced solar panels makes it possible to avoid approximately 2.15 tons of CO₂-equivalent emissions. At the same time, water consumption is reduced by nearly 10,000 cubic meters, while mineral resource extraction – and consequently the overall environmental footprint of production – also decreases.
However, the widespread adoption of such technologies is currently hindered by existing EU legislation. In Germany, for example, companies are required to recycle at least 85% of the mass of solar panels, but the regulations do not take into account the value of the recovered materials. As a result, factories only need to recycle glass and aluminum to comply with the law, while silver and silicon – the most economically valuable components – often remain underutilized.
According to the researchers, new rules that incentivize the recovery of the most valuable components could change the situation. Proposed measures include support for building modern recycling facilities, designing solar panels with a view to future disassembly and recycling, and revising the system of environmental fees: the easier a module is to recycle, the less its manufacturer should pay.
