Silicon Stretching Could Mean Much Cheaper Solar Energy

Researchers at the Norwegian University of Science and Technology (NTNU) have developed a commonsense way to lower the cost of solar panels, focusing on their most expensive component: silicon.

“We’re using less expensive raw materials and smaller amounts of them [and] we have fewer production steps and our total energy consumption is potentially lower,” Fredrik Martinsen and Ursula Gibson of NTNU’s Department of Physics said in a statement.

Gibson and Martinsen say they’ve developed a processing technique that produces solar cells from silicon 1,000 times less pure than what’s now considered essential for making the panels. As a result, the silicon is much less expensive.

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The solar cells used by the NTNU team, working with colleagues at Clemson University, are made from silicon fibers coated in glass. The researchers used the same stretching methods used to make fiber-optic cables, but in this case added a dollop of silicone.

Fiber-optic cables are made by softening thin glass rods with heat, then stretching them into filaments. The NTNU fibers for solar cells are made by inserting a silicon core into a glass tube about one-tenth of an inch in diameter. This assembly is then heated to soften the glass and melt the silicon.

As with fiber-optic cable, the assembly is stretched until it becomes a thin fiber of silicon encased in glass as much as 100 times narrower than it was before.

By borrowing the technique for making fiber-optic cables, the NTNU-Clemson researchers also solved another problem -- the need for pure silicon in solar cells. Ridding silicon of contaminants takes hard work, a lot of energy and a generous research grant. Melting and stretching it, though, purifies silicon even as it turns it into a filament suitable for a solar cell.

But by melting and stretching the silicon, Gibson says, “We can use relatively dirty silicon, and the purification occurs naturally as part of the process of melting and re-solidifying in fiber form. This means that you save energy, and several production steps.”

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For example, the NTNU-Clemson approach requires only about one-third of the energy to produce a solar cell than that of the conventional method, according to an estimate in their article on the research published in the journal Scientific Reports.

Gibson said she was inspired to combine silicon purification and solar cell production after reading an article on silicon fibers by John Ballato at Clemson, a leading researcher in developing fiber-optic materials.

“I saw that the method he described could also be used for solar cells,” Gibson said. So she and her research team started working with Ballato, “and we developed a key technique at NTNU that improved the fiber quality.”

By Andy Tully of Oilprice.com

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