Making More Solar Cells from Silicon
By Kevin Bullis in Technology Review, March 4 2010
A new manufacturing process could cut the cost of making crystalline silicon wafers for solar cells by 80 percent. The process is being developed by Lexington, MA-based 1366 Technologies, which this week showed off the first solar cells made this way. The technology is key to the company's plan to make solar power cheaper than the electricity generated from coal within 10 years.
Silicon wafers are the core component in conventional solar cells--they're what absorbs sunlight and generates electrons. Yet the way wafers are currently manufactured wastes half of the expensive, ultra-pure crystalline silicon they're made from. When large ingots of silicon are cut into hair-thin wafers, waste silicon is lost as sawdust. The new process--details of which remain secret--produces wafers directly from molten silicon without any sawing. This saves material and reduces the number of steps needed to make solar cells, both of which bring down costs.
"The technology could be disruptive," says Reidar Langmo, the CEO of Novus Energy Partners and the founder of the solar company REC. Langmo recently joined the board at 1366.
The process was invented by Emanuel Sachs, a professor at MIT who developed a similar technology that was commercialized by Evergreen Solar, a solar cell manufacturer based in Marlboro, MA. But the new process will be much faster, says Frank van Mierlo, 1366's CEO. One machine could produce 30 times more watts of solar cells, which could lower the cost of equipment, as far fewer machines would be needed to make the same number of solar cells. The company plans to make solar cells that are the same dimensions as conventional solar cells. That way they can be stitched together in arrays to make complete solar panels using existing manufacturing lines.
So far the company has made only small solar cells--a couple of centimeters across (conventional solar cells are about 15 centimeters wide). Van Mierlo says the company plans to break ground on its first 100-megawatt production facility next year.
1366's first cells are not nearly as efficient at converting the energy in sunlight into electricity as crystalline solar cells currently on the market. However, while van Mierlo doesn't give a specific figure, he says his company's cells are more efficient than thin-film solar cells, another type of solar cell that is cheaper to produce than crystalline silicon ones. Commercial thin film cells, such as those made of cadmium and tellurium, are about 11 percent efficient.
The technology is being scaled up with the help of a $4 million grant from the Advanced Research Projects Agency for Energy and $5 million in private funds the company raised as a result of getting that grant, van Mierlo says.