Getting the silicon out of silicon panels

How are solar panel manufacturers taking the pain out of the shortage of polysilicon that is hurting its ability to meet demand?

They are cutting out the amount of silicon they put into their solar cells, said Dick Swanson, founder of SunPower, which makes some of the most efficient solar cells on the market. In the first quarter of 2005, SunPower's cells contained between 12 and 14 grams of silicon. Now they contain just under 8 grams, while the industry average is 10.

"We plan to get down to 5 grams," he told an audience at the ThinkEquity Greentech Summit on Thursday in San Francisco. If polysilicon gets down to $20 a kilogram, that could save 10 cents a watt in the cost of the electricity produced. Swanson admitted that the $20 a kilo price is unlikely. It's now around $60. But new capacity is coming on, so it could get down to the mid-20s.

Solar cell manufacturers are cutting costs in other ways, too. In the old days, silicon wafers were sawed off one at a time off an ingot. Now, the industry uses a wire slicer, like an egg slicer, to get through the hard material. The development of these tough wires came from the radial tire industry. This allows the solar cell makers to make thinner wafers (which use less material) simultaneously.

Swanson also said that SunPower has a goal of making its solar cells more efficient. The company has developed solar cells that are 22 percent efficient. That is, they convert 22 percent of the sunlight into electricity. He'd like to get to 24.6 percent. The absolute physical maximum for a silicon solar cell is 29 percent.

SunPower also has a goal of reducing the cost of solar power by 50 percent by 2012. By that time, solar modules (before installation costs) should cost $1.82 a watt.