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Saturday, November 17, 2007

Solar energy without the panel

Imagine a solar panel without the panel. Just a coating, thin as a layer of paint, that takes light and converts it to electricity. From there, you can picture roof shingles with solar cells built inside and window coatings that seem to suck power from the air. Consider solar-powered buildings stretching not just across sunny Southern California, but through China and India and Kenya as well, because even in those countries, going solar will be cheaper than burning coal. That’s the promise of thin-film solar cells: solar power that’s ubiquitous because it’s cheap. The basic technology has been around for decades, but this year, Silicon Valley–based Nanosolar created the manufacturing technology that could make that promise a reality.

The company produces its PowerSheet solar cells with printing-press-style machines that set down a layer of solar-absorbing nano-ink onto metal sheets as thin as aluminum foil, so the panels can be made for about a tenth of what current panels cost and at a rate of several hundred feet per minute. With backing from Google’s founders and $20 million from the U.S. Department of Energy, Nanosolar’s first commercial cells rolled off the presses this year.

Cost has always been one of solar’s biggest problems. Traditional solar cells require silicon, and silicon is an expensive commodity (exacerbated currently by a global silicon shortage). What’s more, says Peter Harrop, chairman of electronics consulting firm IDTechEx, “it has to be put on glass, so it’s heavy, dangerous, expensive to ship and expensive to install because it has to be mounted.” And up to 70 percent of the silicon gets wasted in the manufacturing process. That means even the cheapest solar panels cost about $3 per watt of energy they go on to produce. To compete with coal, that figure has to shrink to just $1 per watt.

Nanosolar’s cells use no silicon, and the company’s manufacturing process allows it to create cells that are as efficient as most commercial cells for as little as 30 cents a watt. “You’re talking about printing rolls of the stuff—printing it on the roofs of 18-wheeler trailers, printing it on garages, printing it wherever you want it,” says Dan Kammen, founding director of the Renewable and Appropriate Energy Laboratory at the University of California at Berkeley. “It really is quite a big deal in terms of altering the way we think about solar and in inherently altering the economics of solar.”

In San Jose, Nanosolar has built what will soon be the world’s largest solar-panel manufacturing facility. CEO Martin Roscheisen claims that once full production starts early next year, it will create 430 megawatts’ worth of solar cells a year—more than the combined total of every other solar plant in the U.S. The first 100,000 cells will be shipped to Europe, where a consortium will be building a 1.4-megawatt power plant next year.

Right now, the biggest question for Nanosolar is not if its products can work, but rather if it can make enough of them. California, for instance, recently launched the Million Solar Roofs initiative, which will provide tax breaks and rebates to encourage the installation of 100,000 solar roofs per year, every year, for 10 consecutive years (the state currently has 30,000 solar roofs). The company is ready for the solar boom. “Most important,” Harrop says, “Nanosolar is putting down factories instead of blathering to the press and doing endless experiments. These guys are getting on with it, and that is impressive.”

MICHAEL MOYER
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