Cadmium: The Dark Side of Thin-Film?

The future of the solar power industry may be bright, but solar also has a dark side — the panels being built today have an estimated lifespan of 30 to 40 years and then are largely discarded. The problem with that is that some thin-film photovoltaic solar cells contain hazardous substances like cadmium that can pose a health risk if the solar panel is simply thrown out after it’s done soaking up the sun. The issue is important enough that in late October, the Silicon Valley Toxics Coalition (SVTC), which lobbies to keep old computer parts from being dumped, plans to release a report raising concerns about cadmium in solar panels and urging manufacturers to reclaim old panels to keep cadmium out of the waste stream.

Only about 1 percent of electrical generation globally comes from solar today, but that is expected to grow to 20 or 40 percent by 2020, according to McKinsey & Co. SVTC cites forecasts such as that to argue that the solar industry should develop best practices now to ensure solar panel makers take responsibility for the product lifecycle.

“The writing is pretty much on the wall that solar panels have materials in them that need to be recovered because some of them are hazardous,” said Shelia Davis, executive director of the SVTC. Although relatively few solar panels have reached end of life, she’s concerned that when more of them are retired, they could end up with other construction debris in landfills.

Cadmium, a byproduct of copper, lead and zinc mining, can be really bad for humans and the ecosystem. It’s a toxic metal that can cause kidney and breathing problems, according to the U.S. Labor Department. The European Union has also banned cadmium from being used in batteries and electronics.

Cadmium is used in one of the leading new thin-film PV panel types, but as a compound that manufacturers argue is much safer than cadmium alone. Thin-film solar leader First Solar uses cadmium-telluride to make the semiconductors that are sandwiched between two sheets of glass to convert the sunlight into electricity. So do newer startups like AVA Solar.

Cadmium-telluride (called cad-tel for short) is a more cost-effective way of making thin-film PVs than the older crystalline silicon design. AVA Solar’s vice president of marketing, Russell Kanjorski, said cad-tel is a compound that renders the cadmium inert, reducing the risk of contamination versus cadmium alone. Tests by the National Renewable Energy Laboratory showed that cad-tel would have to be heated to 1,041 degrees Celsius before it breaks down. Most roof fires burn at temperatures of 800-900 degrees.

Nonetheless, OSHA labels cad-tel a hazardous material that must be handled with caution in the manufacturing process as if it were cadmium, Kanjorski added. And when it starts shipping its first solar panels, AVA Solar will set aside a certain amount of money from each sale to fund a reclamation program. “You don’t want to be a green company but then leave a problem 30 or 40 years from now,” he noted. First Solar also offers a reclamation program.

At this point AVA and First Solar seem to be in the minority. Reclamation programs are a low priority for startups focused more on raising capital and building production, pointed out Graham Stevens, associate director of the energy practice at Navigant Consulting. “It’s not surprising that on the cadmium telluride side some of the smaller companies that are startups are not as focused on the environmental issues,” he said. Stevens anticipates many will eventually develop reclamation programs once their businesses mature.

Cad-tel thin film panels are poised for strong growth as the overall solar industry grows. The thin-film solar panel market grew 126 percent in 2007, over 2006, primarily due to growth of the cad-tel product, according to Navigant research. The two other thin film types are copper indium gallium selenide (CIGS), which has one-hundredth the amount of cadmium as cad-tel, and amorphous silicon, which contains no cadmium, said Stevens.

Ultimately, that’s the purpose of the forthcoming SVTC report: to deal with cad-tel now before it gets too big. The SVTC’s Davis says she intends for her report to draw attention to the problem and encourage solar panel makers to deal with end-of-life issues for their products now.


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