Researchers from the Institute for Frontier Materials at Deakin University claim to have solved the biggest problem currently preventing photovoltaic cells from being recycled.
Material scientists Dr Md Mokhlesur Rahman and Prof Ying (Ian) Chen pioneered the investigation to recover silicon from waste solar panels and then nano-size it, ready for use in lithium-ion batteries. They say this is key to repurposing discarded solar cells and will prevent high-value waste from going to landfill.
“Although silicon semiconductors make up a relatively small part of solar panel cells, the material’s value is extremely high. Scientists have been looking for ways to repurpose the silicon for some time and we believe this to be the missing piece of the puzzle,” says Dr Rahman.
With the average service life of a solar panel being between 15 and 25 years, the researchers reckon that without a silicon recycling process, by 2050 there will be around 1.5 million tonnes of solar panel waste in landfill – the equivalent of around 100,000 small cars.
And while the bulk of each panel is made up of glass, metal and plastic materials, there is a small part made from silicon.
“Silicon cells are the most important component of a solar panel, transferring the sun’s energy into electrons. They’re also a high-value material being a chemical element and far too precious to end up as waste, which is why this finding is significant,” says Prof Chen.
“We can’t claim solar panels to be recyclable, in a circular economy sense, until scientists find a way to harvest and repurpose their most valuable components.”
Dr Rahman continues: “Surprisingly, the recovered silicon seems to work the same way as commercial silicon does. Our preliminary investigation validates the concept of disassembling silicon-based photovoltaic panels, and repurposing the existing silicon into nano-silicon for the battery industry, creating huge potential as an alternative source for the sector.
“Our discovery addresses several significant challenges currently facing industries dependent on batteries and energy storage heading into the future.
“First, being such an exceptionally high value commodity with widespread applications we do not want any of this precious product wasted. Battery grade nano-silicon is highly expensive and retails for more than $44,000 per kilogram.
“Second, with the automotive industry set to be battery driven in the future, the push to find ways to increase battery capacity is growing. Part of the silicon repurposing process is to nano-size the battery grade silicon, leaving a nano-silicon, which can store about 10 times more energy in the same space.
“It’s the holy-grail of repurposing – to take a product that would otherwise be waste, recycle it, and in the process make it even more valuable at the other end.”
The project has been directly supported by Institute for Frontier Material’s Circular Economy Strategy Lead, Catherine McMahon, in collaboration with Deakin Research Innovations’ Senior Commercial Manager Andrew Rau and industry partner Delaminating Resources Melbourne.