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Swanson’s cells are among the most efficient commercially available forms of photovoltaic technology; they convert around 22 percent of the sunlight hitting them into electricity. (The solar panels in Chicago will produce about two-thirds as much power as they would in a sunnier location.) But the panels and wheezing motor are also a stark reminder of just how difficult it has been to make silicon photovoltaics cheap enough to compete with more conventional sources of electricity.

Right now, with the 30 percent investment tax credit, the cost of energy from a photovoltaic plant in a sunny region is competitive with electricity produced by fossil fuels during peak hours, says Swanson. But that is the best-case scenario for solar. In less sunny regions and at times other than the middle of the day, when electricity prices are high and solar cells are most efficient, the power produced by photovoltaics is still far too expensive.

Dozens of startups have formed in recent years to pursue technologies that their founders hope will be more cost effective. To Swanson’s mind, however, the attention given to these efforts is misplaced. The cost of electricity from silicon photovoltaics is decreasing by 5 to 8 percent a year as the industry grows at a rapid pace, he says; within five years, as the existing technology improves and manufacturers realize economies of scale, it will be competitive without federal incentives.

“We don’t need a breakthrough,” Swanson says. “Waiting for the next big breakthrough [in photovoltaics] will do nothing but cause you to grow moss underneath your feet.” He adds, “We have a road map where we can very clearly see how to halve the cost from where we are today. And that is sufficient to fuel explosive industry growth.”

Turning the Corner
The solar industry might not need a breakthrough to continue healthy growth rates. But many scientists say that without dramatic advances, solar power will never supply the vast amount of power needed to eventually displace fossil fuels.

Of the 46 new energy research centers announced by the secretary of energy in late April, 24 are doing work related to solar power, and each is receiving $2 million to $5 million annually over the next five years. Likewise, two of the eight new DOE innovation hubs will focus on solar technologies: one on electricity and the other on techniques for storing the energy from sunlight in the form of fuels. And the proposed 2010 DOE budget, which (coming just a few months after the stimulus bill) contained relatively modest increases for most new energy technologies, nearly doubled the research budget for solar power.

Much of the research focuses on overcoming the fundamental dilemma of photovoltaic technology: the trade-off between cost and efficiency. Conventional solar cells are efficient because the silicon from which they’re made is grown as a single crystal, yielding a perfectly ordered molecular structure; when the semiconductor absorbs sunlight, the light’s energy excites electrons that can travel through this crystal structure unimpeded, escaping to create an electrical current. But making devices out of single-crystal silicon is relatively difficult and expensive. Newer photo­voltaic technologies use materials that have a less ordered structure and can be deposited as thin films; they are potentially easier and cheaper to make, but they’re also less efficient.

“With photovoltaics you have either high efficiencies or low cost, but what we urgently need are [photovoltaics] with both attributes,” says Harry Atwater, a professor of physics and materials science at Caltech. “One of the challenges of solar power is how to get hundreds of gigawatts to a terawatt of power in a way that is cost effective.” Achieving that, he says, may take technology “very different than what we use today.”

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Credits: Chris Strong, Technology Review
Video by Robert Brilliant

Tagged: Business, Energy, renewable energy, solar power, economics, stimulus package

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