Summary:

The National Renewable Energy Laboratory (NREL) is looking into ways of reducing waste and recycling solar panels, which contain some hazardous waste that can't go to landfills. Only one state in the country, Washington, has dictated what to do when solar modules end their useful life. 

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Main Article:

The cutting-edge research at the U.S. Department of Energy's (DOE's) National Renewable Energy Laboratory (NREL) will one day go to waste—but not into a landfill.

Every technology eventually runs into the end of its life. Photovoltaic (PV) panels and lithium-ion (Li-ion) batteries become less effective and need to be replaced. Researchers at NREL are making strides toward ensuring old technology can be more easily recycled.

"We're thinking about this broadly across many technologies, but PV is the one we've been thinking about the longest at the lab," said Garvin Heath, a senior scientist and member of the Resources and Sustainability Group in NREL's Strategic Energy Analysis Center.

While hundreds of millions of tons of trash continue to be dumped into American landfills annually, a growing percentage has been diverted to recycling centers since the first Earth Day in 1970. But these centers aren't set up for renewable energy technologies. NREL is looking to answer questions such as: "What methods should be used to recycle materials from PV panels and batteries used to power electric vehicles?" and "How can that be done economically?"

Demand for PV Power Raises Solar Panel Questions

Globally, the amount of energy generated by PV has risen exponentially since the early 1990s, when it barely registered, to 512 gigawatts last year. The amount is expected to hit 4.5 terawatts in 2050. Lagging that increase will come a surfeit of PV panels past their prime. In 2050, the United States is projected to have 10 million metric tons of PV waste—half of what China's problem will be, according to a report co-authored by HeathPDF. In addition to his work at NREL, Heath leads a task force on the sustainability issues of PV for the International Energy Agency.

Most solar panels today use silicon in converting sunlight into electricity and carry a 25-year warranty. More than 90% of a PV panel's weight comes from glass, plastic, and aluminum, which aren't hazardous waste. But the trace elements of silver, tin, and lead that are also part of the panels are considered hazardous, so ensuring proper disposal at end of life is important.

It's also important to recover the precious, critical, and hazardous materials in end-of-life panels. "If we can extract the materials, the potential value of those materials is considerable," Heath said.

A 2050 estimate projects that, in the United States, enough raw materials can be recovered to produce 2 billion new panels (the equivalent of 630 gigawatts) and puts the value of those materials at $15 billion. "Of course, if those materials go back into creating new modules, that's a nice circular loop," Heath said. "Not all those materials are going to be able to do that, but there's potential there."

One U.S. manufacturer, First Solar, unveiled a free PV recycling program in 2005. The company's panels differ from the more commonly used silicon panels in that they are made using cadmium telluride (CdTe), and cadmium ranks as one of the most toxic materials on the planet. First Solar recaptures about 95% of the CdTe, refines it, and then reuses it in a new solar panel through a recycling process they own and run at several facilities around the world.

A law that took effect last year across the European Union requires that at least 85% of waste from PV panels must be recovered, and 80% of that waste must be either recycled or reused. "This is just a start," said Michael Kempe, a senior scientist at NREL. "It essentially means that the frames and glass need to be recycled because that is where the mass is."

In the United States, only one state has decided what must be done with PV panels at the end of their life. In 2017 Washington approved a law requiring manufacturers to finance a takeback and recycling system at no cost to the owner. The law will take effect in 2021, at which time only PV manufacturers participating in a recycling plan will be allowed to sell their panels in the state.

Recycling PV panels will require that they first be collected and transported, which is an expensive process. Then the components must be separated, which is also expensive. The Electric Power Research Institute reports of hearing recyclers quoting prices between $10 and $30 a module just for processing. The costs are expected to come down as the amount of waste volume increases.

The price that owners of rooftop PV panels ultimately must pay will determine where that piece of technology winds up. "If they have to pay $25 to recycle it, it's going in a landfill," Kempe said. "But if they can take it to a recycling facility for free, that's where it will go. This is why it is so important for economical recycling processes to be developed and implemented."

Kempe, whose research focuses on ways to extend the lifespan of  PV panels, said his goal is to see them last for 50 years. Manufacturers could make some changes to a PV panel so that it would be easier to recycle decades from now, but that's not likely to happen if it means sacrificing durability or performance. "That trumps ease of recycling," Kempe said.