Solar panels have become one of the most recognizable symbols of clean energy.
They sit on rooftops, cover large solar farms and generate electricity from sunlight without producing carbon dioxide while operating.
They play an important role in reducing greenhouse gas emissions and helping countries move away from fossil fuels.
However, there is another side to the solar energy story that is becoming increasingly important. As millions of solar panels grow older, scientists are asking a simple but critical question: What should happen when these panels stop working?
Experts estimate that by 2050, the world could generate more than 80 million metric tons of discarded solar panels.
Without better recycling systems, many of these panels could end up in landfills, creating a major waste problem while also throwing away valuable materials that required significant mining and energy to produce.
Researchers at New York University Tandon School of Engineering believe recycling needs to become a much bigger part of the solar industry’s future.
In a new paper published in Chem Circularity, Assistant Professor Juanita Hidalgo and postdoctoral researcher Sara Hamilton explain that chemistry may provide a smarter and more sustainable solution.
Today’s recycling methods mainly recover materials that are relatively easy to separate, such as aluminum frames, glass and copper wiring. While these materials are valuable, they are only part of what makes up a solar panel.
Inside the panels are important metals including silver, indium, gallium, tellurium and lead. These materials are essential for producing solar cells and are expensive to mine. Unfortunately, recovering them is often difficult and costly.
Most current recycling relies on a process called pyrometallurgy, which uses extremely high temperatures—sometimes close to 2,000 degrees Celsius—to melt materials apart. Although this method works, it consumes large amounts of energy and can make it difficult to separate different metals cleanly.
The researchers say another approach called hydrometallurgy could be a better option. Instead of using extreme heat, this method uses specially chosen liquids to dissolve specific metals while leaving other materials behind. The dissolved metals can then be purified and reused to make new products.
Because the process works at much lower temperatures, it could use less energy and recover valuable materials more efficiently.
The study also found that different types of solar panels present different recycling challenges. Conventional crystalline silicon panels, which make up about 95% of the global solar market, usually require strong acids to recover their silver. While effective, these chemicals can be hazardous to handle and difficult to recycle themselves.
Thin-film solar panels also contain valuable metals that often require harsh chemical treatments to recover.
One encouraging finding involves perovskite solar cells, a newer technology attracting worldwide attention because they are cheaper to manufacture and have achieved very high efficiencies in laboratories. Unlike traditional solar cells, many perovskite materials can be separated much more easily.
In fact, several recent studies have shown that one of their key ingredients, lead, can be recovered using something as simple as hot water. As the water cools, the dissolved lead forms crystals that can be reused to manufacture new perovskite solar cells.
The researchers believe the future of solar power should include recycling from the very beginning.
Instead of focusing only on making panels more efficient, engineers should also design them so they can be easily taken apart and their valuable materials recovered at the end of their working lives.
This approach could help make solar energy cleaner, more sustainable and truly circular for generations to come.
