The rise of solar power in the last decade has been a climate success story. But solar power comes with a dark side. As solar farms grow around the world, so does the problem of tons of waste panels in the future.
Researchers in Australia have now come up with a technique that could not only make solar panels easier to recycle, and also make them less expensive to manufacture. And all it takes is a kitchen microwave.
Most solar panels today are made of silicon. During their manufacture, the silicon is heated at temperatures above 900°C in a furnace to change its properties. This burns a lot of energy and adds cost. Zapping silicon in microwave ovens instead would not only be faster and more energy efficient, it also makes the panels easier to recycle at the end of their working life, the Australian team reports in a paper published in Applied Physics Letters.
The world’s solar capacity went from 1.4 gigawatts in 2000 to 760 gigawatts in 2020, and solar power now generates almost 4 percent of the world’s electricity, according to the International Energy Agency.
Solar panels typically last about 30 years. Studies predict that around 8 million metric tons of these panels will reach the end of their lives by 2030. That number will go up to 80 million metric tons by 2050.
Most of these panels, which contain toxic lead that can leach out, end up in landfills. Besides the potential environmental hazard, this is also a waste of resources because the panels contain valuable materials. Only the European Union mandates panel recycling as of now. But current recycling technologies are limited and energy-intensive.
Binesh Puthen Veettil of Macquarie University and colleagues devised a cheaper, less energy-intense way to both make and recycle solar panels. The team bought a kitchen microwave and added heat-proofing so it could handle very high temperatures. They found that microwaves could heat and process the silicon in solar cells nearly as efficiently as a furnace. Microwave radiation selectively heats silicon, leaving the rest of the panel of glass, plastic and aluminum largely unaffected.
As an added bonus, microwaving also softened the plastic, making it easier to peel off, and freeing the solar cell and glass for recycling. The plastic coating is designed to protect the panel from moisture, but is difficult to remove. “Until now it made economic sense to just dump the panels in the landfill,” said Veettil in a press release. “In the rare instances when they are recycled, you crush the panels, heat them to about 1400°C and wash them with chemicals to remove the plastic—a highly energy-demanding process.”
The researchers have a patent pending for the microwave-based recycling process. They are now working on further improvements with plans to commercialize it.
Source: Binesh Puthen Veettil et al. Microwave annealing of silicon solar cells. Appl. Phys. Lett. 2023.