U.S. Energy Secretary Steven Chu recently announced the funding of 24 new solar projects as part of the nation’s economic stimulus efforts. One of the projects involves research at Missouri University of Science and Technology, where Dr. Lifeng Zhang is working on methods to recycle silicon wastes generated in the production of solar wafers.
Silicon is expensive, accounting for approximately 25 percent of the cost of a solar cell. As much as 50 percent of the silicon used to make solar wafers becomes a slurry waste. Currently, that waste is being stored until someone can figure out how to re-use the silicon in the slurry.
“We need silicon materials,” says Zhang, assistant professor of materials science and engineering at Missouri S&T. “There’s no reason to waste it. We have to find a way to recycle it.”
To make the material recyclable, silicon powders must be separated from bigger, non-recyclable particles in the slurry. According to Zhang, this can be done by mixing the slurry with water and forcing it through a flow chamber. The particles sink and separate from the silicon powder.
But a more promising method might involve electromagnetic separation. Silicon, like metal, is conductive in a liquid state. Zhang proposes liquefying it at high temperatures. He says electromagnetic equipment could be used to separate the non-conductive particles from the heated slurry. The silicon slurry would then be considered “clean.”
Zhang’s national research award is $150,000. The university will match that with another $150,000. Zhang says $130,000 will be used to purchase the electromagnetic equipment.
Several solar cell manufacturers intend to work with Zhang by sending him slurry samples for testing purposes. Of course, silicon is also used to make computer chips and other products.
“This is a hot topic,” Zhang says. “I like working on it a lot.”
The project is officially funded for one year. If Zhang can prove his methods work, there is a good chance that the research will continue to receive support for another three years.
The Missouri S&T project is part of a wider $300 million investment designed to support the nation’s clean energy technologies, including solar power, carbon capture from coal, and high-efficiency cars and trucks.
All of the officially funded research projects selected by the government are part of the American Recovery and Reinvestment Act, which also involves support from private partners.