Raphael Thys
Recycling solar panels into different components is possible in a clean, green way. 9Tech
Venice-based startup 9Tech has found a highly efficient approach to recycling solar panels where up to 99 percent of components can be recovered.
The approach differs from previous attempts since it does not release toxic fumes into the atmosphere and is much cleaner and greener than conventional recycling methods.
As countries push for cleaner energy sources, estimates suggest that a whopping 400 gigawatts of solar power are being added to the grid every year, and this number is expected to more than quadruple by the end of the decade.
While this is a welcome move, another worry troubling environmentalists is the pile of waste that will result when the solar panels reach the end of their lifespan. Built to withstand weather events over 30 years, solar panels are tough and difficult to dismantle. Recycling or recovering individual components is even more challenging and uses some harsh chemicals.
Why are solar panels hard to recycle?
Most solar panels being installed these days belong to the crystalline silicon type, which consists of an array of silicon wafers topped with a coating of silicon nitride. Conductors made from silver and copper are then printed onto the wafer surface, and the whole assembly is laminated in adhesive polymers to protect it from moisture.
To strengthen the setup further, the laminated sheets are encased in sheets of tempered glass and put into an aluminum frame. The polymer adhesive must be removed first to recycle the panel, but it is extremely sticky.
It can be burned off but releases harmful gases. Recovering expensive components like silver requires toxic reagents like hydrofluoric acid and nitric acid. Therefore, sending the panels to a landfill is much easier than recovering individual components.
Venice-based 9Tech has developed an efficient method of recycling components that do not release toxic chemicals or poisonous fumes.
How does 9Tech recycle solar panels?
At its pilot plant at an industrial site in Venice, 9Tech’s personnel remove the aluminum frame and tempered glass, leaving them with a sandwich of silicon wafers, metal conductor, and sticky polymer.
They use a combustion furnace to heat the components to temperatures over 750 Fahrenheit (400 degrees Celsius), where the polymer vaporizes. A filter captures the content of its fumes, and the heat from the furnace is repurposed.
The leftovers from the furnace are put through a series of sieves and a roller that removes silicon based on its thickness and mechanically strips out the copper. The team uses an organic acid to remove the silver from the silicon pieces. It uses ultrasound to loosen the bonds between the two elements.
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A mesh net is then used to remove the silicon pieces, leaving silver in the solution, which can either be filtered out or centrifuged. According to the company, its pilot plant can recover 90 percent of the silver, 95 percent of the silicon, and 99 percent of the copper from the solar panels.
The approach is more expensive to execute than conventional methods, but the high purity and high value of the recovered materials can help offset the cost. The recovered materials are in their pure form, making them suitable for reuse.
The team wants to build a demonstration facility that will process 800 panels daily. In addition to helping recycle solar panels, the facility will finetune the economics of running a recycling plant.
The report contains information that first appeared in IEEE Spectrum.
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ABOUT THE EDITOR
Ameya Paleja Ameya is a science writer based in Hyderabad, India. A Molecular Biologist at heart, he traded the micropipette to write about science during the pandemic and does not want to go back. He likes to write about genetics, microbes, technology, and public policy.