Inside Clean Energy: Recycling Solar Panels Is a Big Challenge, but Here’s Some Recent Progress

German researchers have made solar cells from 100 percent recycled silicon.

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Close-up of a photovoltaic solar energy panel with reflection of the sun. Credit: Andrew Aitchison / In pictures via Getty Images
Close-up of a photovoltaic solar energy panel with reflection of the sun. Credit: Andrew Aitchison / In pictures via Getty Images

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German researchers said this week that they have taken silicon from discarded solar panels and recycled it for use in new ones.

This is a positive step for dealing with the coming mountain of waste from solar power, but it’s just one part of dealing with a complicated challenge.

The Fraunhofer Center for Silicon Photovoltaics CSP in Freiburg, Germany, said that its researchers were part of a team that produced solar cells from 100 percent recycled silicon. Cells are the little squares, usually blue, that you see arranged in a tile pattern on solar panels. They are the parts that capture the sun’s energy to convert it to electricity, and silicon is their essential material.


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Peter Dold, project manager at Fraunhofer CSP, said the process can work for recycling all crystalline silicon solar parts, regardless of the manufacturer. This is an important detail because one of the challenges in recycling solar components is that the process sometimes varies to account for differences in the manufacturer.

“It was important for us to develop a scalable process that makes economic sense,” Dold said in a statement.

To get an idea of the significance of this announcement, I reached out to Meng Tao of Arizona State University, a leading authority on developing systems to recycle solar components.

“I applaud their progress,” he said about the work at the Fraunhofer Center.

And then he explained why recycling silicon is only a small part of dealing with solar power waste.

Solar power is booming, with millions of metric tons of solar panels being produced each year. A panel has a projected lifespan of about 25 years, which means that today’s new solar farms will go out of service in the late 2040s.

The International Renewable Energy Agency said in a 2016 report that the waste from solar panels was on track to go from 250,000 metric tons in 2016 to a cumulative total of 78 million tons by 2050. The United States would have 10 million tons that year.

Since that report, the growth of solar power has accelerated, so the 2050 numbers are likely going to be even higher, Tao said.

As solar cells age, tiny cracks may begin to appear on the silicon surface, which can reduce the ability of the cells to do their job. But most of the deterioration of a solar panel is because of wear and tear on other parts, like electrical contacts.

Solar cells made of recycled silicon, developed by a team that includes Fraunhofer Center for Silicon Photovoltaics CSP in Freiburg, Germany. Credit: Fraunhofer Center for Silicon Photovoltaics CSP

Most of the weight in a solar panel, about 75 percent, is glass, Tao said. Next is aluminum, with 10 percent; wiring in a junction box, at 5 percent; and silicon, with just 3.5 percent. Panels also contain small amounts of lead, which is one reason that they need to stay out of landfills. (The percentages are approximate and can vary depending on variations in the technology and manufacturer of the panels.)

So, silicon is an important material, and being able to recycle it is a step forward, but researchers need to find cost-effective ways to recycle all the parts in a solar panel.

Today, most recyclers that work with solar panels are breaking them apart to reuse the aluminum and the wiring, but there is a limited market for the other components, Tao said.

Researchers have been looking for uses for glass from solar panels and found solutions like making a material that can be mixed with concrete.

But the ultimate goal for solar recycling is to make the process circular, which means old solar components could be processed to be used in new solar components, Tao said. That hasn’t happened yet with glass.

The desire for a circular economy around solar panels is one reason why the announcement from the Fraunhofer lab is so encouraging.

Researchers took old solar cells and broke them down into fragments as small as 0.1 millimeter and then used a chemical process to strip away everything but the silicon. The next step was to process the silicon into a form that looks like a pile of gray grains. After that, researchers use this silicon to manufacture new solar cells.

The resulting cells have an efficiency of 19.7 percent, which refers to how well the cells can convert the energy from the sun into electricity. This is below the 22.2 percent efficiency of equivalent new cells on the market, but it’s better than the efficiency of the older solar cells that were recycled, Dold said. The research is ongoing, and may still lead to greater efficiency.

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Tao is part of a team at Arizona State that was awarded a $485,410 grant from the U.S. Department of Energy, which was announced in November. His lab will be using the grant to help develop chemical processes to help extract valuable and toxic materials from solar panels.

Much like the battery recycling research I wrote about last month, some of the most promising research in recycling solar panels has to do with breaking materials down at a chemical level, rather than the less sophisticated process of breaking them down mechanically.

Tao said he has noticed growing public interest in solar panel recycling, which he thinks is because people realize that the transition to clean energy needs to be done in a way that minimizes waste.

“Certainly solar energy is sustainable, but if the technology to utilize solar energy is not sustainable, we still don’t have sustainable solar energy,” he said.

Other stories about the energy transition to take note of this week:

Minnesota Regulators Approve Xcel Plan that Sheds Coal and Embraces Renewables: The Minnesota Public Utilities Commission this week approved Xcel Energy’s long-term plan for managing its power plants, an important document for a trend-setting utility that aims to get to net-zero emission by 2050. The company had sparred with environmental groups over the details of the plan, including Xcel’s initial desire to build a new natural gas plant, as Mike Hughlett reports for the Star Tribune. But the utility later dropped the proposal for the gas plant while continuing to review the possibility of proposing new gas plants in a future plan. The newly approved proposal includes closing all coal plants by 2030, substantial investments in renewable energy and a 10-year extension of the life of the Monticello nuclear plant, which otherwise was scheduled to close in 2030. The nuclear plant still would need to get a license extension from federal regulators. The final version of Xcel’s plan had support from environmental and organized labor groups. Since Xcel was a trend-setter in proposing a net-zero plan in 2018, this plan may end up being another trend-setter for how utilities can take the crucial early steps toward getting to net zero, as I reported last year.

Company Will Build Fast Chargers for EVs at Tennessee Plant: Tritium, an Australian manufacturer of electric vehicle charging systems, said this week that it is opening a plant in Tennessee. The plant near Nashville will have an initial capacity to build more than 10,000 fast-charging systems per year, and will employ about 500 people, according to Andy Humbles of the Nashville Tennessean. President Joe Biden held an announcement event in Washington, D.C., with Jane Hunter, Tritium’s CEO. “It’s going to have a ripple effect, beyond, far beyond the one state,” Biden said. “This is great news for workers across the country, for (the) economy and frankly for the planet.”

Why This Could Be a Critical Year for Electric Cars: As automakers begin selling electric versions of pickup trucks, electric vehicles are close to a breakthrough moment. The rapid growth of EV sales could make 2022 the year when this part of the automotive market becomes unstoppable, as Jack Ewing and Neal E. Boudette report for The New York Times. But there are many companies and workers that stand to lose, like makers of mufflers and fuel injection systems. “It’s one of the biggest industrial transformations probably in the history of capitalism,” said Scott Keogh, chief executive of Volkswagen Group of America. “The investments are massive, and the mission is massive.”

California Coalition Fighting Rooftop Solar Subsidies Has Close Ties to Utilities: A coalition that claims to represent low-income, senior and environmental leaders is running ads warning about a cost shift that forces consumers to subsidize solar for people who live in mansions. But the group, Affordable Clean Energy for All, is not a grassroots movement. It is a public relations campaign sponsored by big utility companies that stand to benefit from policies that hurt rooftop solar, according to this story by me and Anne Marshall-Chalmers. We reached out to nearly all of the social justice groups in the coalition and found that few wanted to talk. The coalition’s ads are trying to influence the public and the California Public Utilities Commission as the commission considers rules that could cut subsidies and substantially increase the costs of owning rooftop solar.

Inside Clean Energy is ICN’s weekly bulletin of news and analysis about the energy transition. Send news tips and questions to [email protected].

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