A new method for removing silicon from used solar panels, transforming it into a nanomaterial, has been tested by a group of researchers at the Institute for Frontier Materials (IFM) at Deakin University in Australia. A result of great value, which has even been quantified at $45,000 per kilogram.

A major breakthrough for renewables

"Solar panel cells are manufactured using high-value silicon, but this material cannot be reused without first being purified because it becomes highly contaminated over the 25–30-year lifespan of the panel," said lead researcher Mokhlesur Rahman in a press release. "We have developed a process that brings the silicon collected from used cells back to a purity of over 99 per cent, in less than a day and without the need for hazardous chemicals. This thermal and chemical process is much more environmentally friendly, more efficient, and less costly than any other method currently on the market."

The nano-silicon extracted through this process is then combined with graphite to create a new type of battery anode that has been shown to multiply the capacity of lithium-ion batteries tenfold. "We are using that nano-silicon to develop low-cost battery materials that will help deliver battery technologies that are higher-performing, longer-lasting, and less expensive — essential for supporting the energy transition in Australia," said Rahman.

The growth of solar energy

Photovoltaic cells are the components of solar panels that convert sunlight into electrical energy. These cells, also known as solar cells, are made of a semiconductor material. Silicon is the most widely used material in solar cells, accounting for more than 95 per cent of the modules currently on the market.

Solar photovoltaic energy generated 179 terawatt-hours (TWh) more energy in 2021 than in the previous year, according to the International Energy Agency (IEA). A record increase, equal to 22 per cent year on year. In 2010, this type of energy amounted to just 32.2 TWh; it now exceeds 1,000 TWh.

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Where do used solar panels end up today?

In addition to solar cells, panels are made up of other components and materials, such as the metal frame and glass covering. According to the International Renewable Energy Agency (Irena), the value of raw materials recoverable from end-of-life solar panels worldwide will be approximately $450 million by 2030. Solar panel recycling can include the separation of glass from the silicon wafer and the separation and purification of silicon cells and metals such as copper, lead, silver, and tin. According to a report published in 2021 by the National Renewable Energy Laboratory (Nrel) and the Electric Power Research Institute (Epri) in the United States, fewer than 10 per cent of photovoltaic modules are recycled.

"This technology developed by Deakin University — which includes purification, nano-silicon production, and integration into new battery technology — is a giant leap forward in how we address the problem of solar panel waste," said Professor Ying (Ian) Chen, director of the Arc Research Hub for Safe and Reliable Energy. "Silicon recovered from end-of-life solar panels can become an enormous and sustainable source of nano-silicon to meet future demand for battery raw materials. Helping to power the homes, transport, and communities of the future."

Translated by Patrick Bracelli