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But it could be.

Mines in Utah are producing a rare metal that's being used to produce solar panels at scale to combat the effects of climate change.

Making solar panels isn’t always green

Mines in Utah are producing a rare metal that's being used to produce solar panels at scale to combat the effects of climate change.

Tellurium is used to make solar panels—an important clean energy source—but mining it in China is decidedly not. 

According to Michael Parr, executive director of the Ultra Low-Carbon Solar Alliance, most solar panels are made with crystalline silicon, with 95 percent of that supply chain coming from coal-powered China.

China’s huge carbon footprint, along with its penchant for using forced labor—among other humanitarian issues—in the region where solar panels are produced, is a sad reality many Americans have been willing to overlook for solar panels, Parr says. 

That might be changing.

“I think people are realizing that even if you turn a blind eye to the sustainability issues, the supply issues are getting increasingly real,” he says. “Some of these developers who have long feasted on cheap panels are saying, ‘Let’s get together and make a buyers consortium committed to buying $6 million a year in US-made modules to incentivize more US [solar power] manufacturing.”

First Solar, for one, wants to keep it in the country. The US solar panel manufacturer will get its tellurium from Rio Tinto, who announced last May that it began producing tellurium at its Kennecott copper operation in Utah, only the second US source of tellurium.

A waste product of copper mining, Saskia Duyvesteyn, chief advisor for R&D at Rio Tinto’s copper product group, says mining tellurium is a “win-win-win.” Mining makes up for the bulk of tellurium’s carbon footprint, she says, and that has already been expended in mining the copper.

“Tellurium is actually an impurity in our final copper. So, by removing it, we reduce that impurity and make a better copper, which means that we can recycle those streams more easily, internally,” Duyvesteyn says. “Then, we treat them less, so that we actually are producing slightly less waste.”

On paper, it hasn’t been economically the best decision for Rio Tinto to produce tellurium—it still isn’t—but, according to Duyvesteyn, the value is intangible. “It can’t just be straight up basic dollars. You’ve got to look at the bigger picture. And some of these [minerals] that are harder to put an easy value on I often put in the commercial priceless category—I don’t know how to put a real price on that,” she says.

Duyvesteyn calls Rio Tinto’s Utah production of tellurium “a game changer” for the industry “A few years ago, there wasn’t even a critical minerals list. That’s part of this change,” Duyvesteyn says. “I think people have recognized how important it is for us to make sure that we’ve got domestic sources.”

First Solar is keenly aware of what US tellurium supply means to making America’s solar panels green. As soon as the Ohio-based company finishes expanding to a third facility, it believes it will be the largest fully vertically-integrated solar manufacturing complex outside of China.

“Our modules are highly sought after by developers of large-scale solar power plants that are looking to reduce their exposure to the risks and volatility associated with Chinese crystalline silicon supply chains,” says Mike Koralewski, First Solar’s chief manufacturing operations officer.

Before First Solar gets the tellurium, it will be refined in Montreal by 5N Plus into a cadmium telluride (CadTel) semiconductor compound, Koralewski says. 5N Plus will also use the tellurium to manufacture ultra-high purity semiconductor materials at its facility in St. George, Utah, to serve the security and medical imaging markets, 5N Plus says.

"Tellurium is actually an impurity in our final copper. So, by removing it, we reduce that impurity and make a better copper, which means that we can recycle those streams more easily, internally."

Brock Alexander, VP of government and defense for 5N Plus, says the company elected to process Kennecott’s tellurium in Montreal for practical reasons. “We have the skills and expertise in the Montreal campus and Montreal site, and as part of our key business, we’ve expanded that facility in June of last year,” Alexander says. “So that’s their focus, to purify tellurium and then compound it with other materials that our customers request.”

CadTel, made from tellurium, is “uniquely American,” and is the only commercially scaled alternative to the Chinese-dominated crystalline silicon market, Koralewski says. CadTel has “the lowest carbon and water footprint and fastest energy payback time of any commercially available solar technology today.”

First Solar’s panels are good for 30 years and can be recycled with more than 90 percent of the CadTel recovered for use in new solar panels, according to Koralewski. A kilogram of CadTel semiconductor can be recycled up to 41 times to produce clean energy for over a thousand years.

Parr says solar products made in the US have a “much smaller” carbon footprint than solar products made elsewhere. “Almost all [US] manufacturing in solar is electrified so there’s no real fossil fuel input except from purchase power. And the grid here is much cleaner than in China. The carbon intensity of the Chinese power grid is roughly double that of the US because they’re still burning a lot of coal,” he says.

Parr has hope for what might lie ahead. “I think if Rio Tinto demonstrates that they can profitably recover tellurium from their waste products, you may see other folks start to crack that door open.”

Michael Moats, a professor of metallurgical engineering at the Missouri University of Science and Technology and a consultant for Rio Tinto, says the struggle to make a civilized lifestyle with all the comforts we need and want is challenging, and there will always be waste products. It’s up to scientists and society to look for ways to minimize the impact of that.

“We have some hard decisions as a country,” Moats says. “Are we happy with the Chinese or any country controlling our supplies? Are we happy with other people polluting and destroying their part of the world so we can keep our part clean?”

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