Here's how to make a solar cell from silicon: take one solid block of doped silicon, saw it into thin wafers, layer said semiconductors beneath a panel of transparent glass, connect them to a metal electrode that can channel away the electrons knocked loose by incoming photons and turn it into a photovoltaic device. That process has at least two flaws: such silicon is expensive, contributing more than half to the final price of a solar photovoltaic, and sawing it turns as much as half of that silicon into wasted grit.*

As a result, solar costs as much as $4 per watt by the time it's installed on your roof or in a large-scale power plant, says Arun Majumdar, the first director of the new Advanced Research Projects Agency for Energy, or ARPA-E. "If you can reduce that to $1.50 per watt it can enable scaling," or widespread adoption of the clean, renewable electricity source, he told at last week's ARPA-E summit.

And a company called 1366 Technologies may have found a way to do just that by growing a nearly pure wafer directly from melted silicon rather than forming an ingot that is then sawed.

The idea could cut wafer costs by as much as 80 percent, says Craig Lund, director of business development for the company that takes its name from the solar constant—the watts of solar radiation that hit each square meter of the atmosphere. From 1366's furnace in Lexington, Mass., the company makes an "as-created fully functioning solar cell." In fact, silicon wafers currently contribute more than half of the high price of sil

That may make silicon photovoltaics, which are the most efficient currently at turning sunlight into electricity, as cheap as thin-film solar cells, whose advantage is cost but which are not as good at creating electric current. In fact, rapidly decreasing cost for solar power means some experts expect such distributed electricity generation to cost the same or less than electricity from today's grid by as soon as 2015.

After all, "more solar energy reaches Earth in every year than the combined total of all the energy in all the fossil fuels still in the ground," noted Chris Rivest, co-founder of SunPrint, whose technology prints thin film solar cells made from cadmium-telluride, at the ARPA-E summit. "By subsidizing corn, we made it a national priority to make food cheap. Why not do that with silicon? Slightly cheaper glass may not be sexy today but when solar uses more glass than construction you can bet it will be."

 * Clarification (3/11/10): This sentences has been changed to clarify the expense of silicon wafers in regard to photovoltaics.