A Sharper Focus for Photovoltaics

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A second-generation design squeezes the process into a single glass block: light beaming through the top of the block reflects off primary mirrors shaped into the bottom face, up to secondary mirrors shaped into the top face, and back to one-millimeter-square photovoltaic cells popped into the center of the primary mirrors.

Whereas silicon solar panels today cost close to $3 per watt to produce, Conley says SolFocus will manufacture solar systems at $2 per watt when it opens its first concentrator plant next year; and he says gigawatt-scale production will cut the cost per watt to just 50 cents. The second generation should cut costs further, says Conley, to as low as 32 cents per watt.

Despite these optimistic claims, though, SolFocus will have plenty of competition. Robert McConnell at the U.S. Department of Energy, and an expert on concentrated photovoltaics, says SolFocus must not only prove its technology but also outperform a growing field of competitors. "They've got at least three dozen competitors, including companies that have many more years of development," says McConnell.

Indeed, SolFocus's toughest competition could come from the world's largest photovoltaic manufacturer, Japan-based Sharp, which has developed a concentrator using Fresnel lenses -- the same basic technology used to amplify the signal beam in lighthouses. Sharp's system employs an array of such lenses in a single block of relatively cheap injection-molded plastic.

The DOE's McConnell says the most critical test for concentrators will be durability. In concentrator photovoltaic's first period of development in the 1970s and 1980s the technology suffered from a series of disasters, akin to the flying blades and broken gearboxes that bedeviled wind power's pioneers. Sulfur in the air eroded mirrors. Hail and wind smashed delicate lenses. Dust jammed the tracking devices needed to keep the systems targeted on the sun. And in the worst cases damaged systems posed serious fire hazards.

SolFocus' self-contained devices should be less susceptible to damage and safer than their predecessors, claims Conley. Nevertheless, they're targeting large field-based solar power plants for their first rollouts, and leaving the more lucrative commercial rooftop market for later on.