Solar energy has become a viable and affordable source of renewable energy around the world. Solar panels for residential and commercial buildings are more affordable than ever, and they are long-lasting, with a lifespan of about 30 years.

But when solar panels have decreased in efficiency to the point that they need to be replaced, this green solution to energy generation becomes an electronic waste-disposal problem. Most spent solar panels end up in landfills with other e-waste, including personal computers, smart phones, and myriad other electronic devices gone kaput.

By 2050, the world will be grappling with an estimated 78 million tons of solar panel e-waste, says Mool Gupta, a professor of electrical and computer engineering at the University of Virginia, where he is working on a solar-panel recycling solution. Viable recycling solutions for e-waste would meet an important target of United Nations Sustainable Development Goal 12, which emphasizes sustainable patterns of production and consumption to minimize waste, including e-waste, and its impact on the environment and on human health.

Gupta says that dead solar panels can be recycled using chemical and thermal processes, but those processes are not economical. Chemically or thermally decomposing the materials that hold solar panels together requires tremendous amounts of energy and creates safety issues that cost more than the value of recoverable materials. So, landfill disposal has become the default option. Any recycling process proposed for solar panels “has to be cost-effective so that people don’t look at the landfill as an option.”

Every year, there is a small decrease in the efficiency of a solar module due to polymer films in the solar panel turning yellow from ultraviolet light exposure. When efficiency is reduced by 80%, “then it’s not economic and that’s the end of life. That doesn’t mean the glass is bad and that doesn’t mean the silicon that was used is bad. There are still valuable components that are in good condition,” he says.

Gupta’s approach began with looking at the components of solar panels, which include an aluminum frame, high-quality glass for photovoltaic (PV) application, an encapsulant on both sides of the solar cell, a silicon wafer, and a junction box. He notes that 14% of the world’s silver is used by the PV industry, but other valuable materials include silicon, aluminum, glass, and copper. “If we can recover those components they can be reused,” Gupta says, while also noting that metal recycling reduces the need for destructive minerals mining.

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