Sieves and stainless steel improve solar panel recycling

A team of Australian engineers has developed a more efficient way to recycle solar panels.

Solar photovoltaics (PVs) are mixtures of glass, metals, silicon and plastic, making them difficult to recycle.

This new process, which has just been patented, can separate out 99% of the components in PVs.

Professor Yansong Shen describes recycling solar panels as: ”a very pressing and urgent problem as  those first generation of panels are coming to their end-of-life.”

Shen is leader of the ProMO research lab at the University of New South Wales, which developed the process.

“We want to reuse and recycle those panels, but at the moment there is very limited research and very limited technology to allow us to do so effectively and prevent them from just ending up in landfill.”

Shen and colleagues have spent three years developing the technique.

First, they remove the aluminium and glass frame leaving the solar cells – which are mixtures of silicon and various metals, including silver.

“The next step is the crushing the panel and separation of material inside the solar cell and that is currently one of key bottlenecks for the whole system,” says Shen.

“If we do not have a simple method for high-abrasion separation, then we can’t effectively move on to the third step which is recovering the various material that has been separated and being able to reuse it.

“The key to our new process is the addition of the sieving aids which help to crush the solar cells into smaller particles allowing a better separation of all the components. That makes it much easier to recover important elements such as the silver contained in the solar cells.”

Diagram of sieving process
Credit: Professor Yansong Shen/UNSW

The team use stainless steel balls and sieves inside a vibrating container to separate the parts of each cell.

The process only takes between five and 15 minutes.

“We spent around three or four months working on that element, also testing with sieving aids made of clay or plastic,” says Chengsun He, a MPhil candidate at the lab.

“We can use different size sieving aids for different stages of the process. The main goal is to ensure that all of the PV cells particles can be crushed by the sieving aids, while the glass and other significant material remains intact at the top.”

Sieves in lab
The new patented PV recyling process developed at UNSW involves crushing and sieving material inside a vibrating container for around 5-15 minutes. Credit: Professor Yansong Shen/UNSW

Then, the pure components can be extracted using a typical chemical leaching process.

This means they can recover precious metals like silver from the panels. The researchers were able to recover about 640 grams of silver per tonne of PV waste taken through their process.

Extrapolating this, they believe that their method could recover between 5000 and 50,000 metric tonnes of silver alone from the PV waste expected to be generated between now and 2050.

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