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Solar Company Says Its Tech Can Power 90 Percent of Grid and Cars
Solar-power-plant company Ausra has released a paper claiming that solar-thermal electric technology can provide 90 percent of U.S. grid electricity, with enough left over to power a fleet of plug-in electric vehicles. The company estimates that such a changeover would eliminate 40 percent of the country's greenhouse gas emissions with a land footprint of 9,600 square miles, about the size of Vermont (thanks, Kent).

The key to the scenario, however, is developing the ability to store energy for 16 hours, thus creating a stable power source through cloudy periods and the night, a feat that has so far eluded engineers.

"If we can do storage," Ausra CEO Bob Fishman said, "We can take on coal."

The paper says Ausra expects to commercialize its energy-storage technology within two years. A prototype of the system will go into a model plant the company plans to finish this summer in Bakersfield, California, the company's founder, David Mills, told Wired.com.

The new research (.pdf) was presented at the IEA SolarPACES conference in Las Vegas, and is described as peer-reviewed.

Solar-thermal power is gaining adherents, including Google.org, which cut a deal with another player, eSolar, as a way to cleanly generate cost-competitive, city-scale amounts of power. Unlike traditional photovoltaics, which use panels to convert sunlight into electricity, solar-thermal plants focus the sun's rays on liquids to make steam that powers turbines. Solar-thermal is flat-out more efficient -- at 20 to 40 percent -- than photovoltaics, which in the field convert sunlight to electricity at about 15 to 22 percent. And solar-thermal fits into the industrial model of power production, meaning that it works in big plants, not distributed across a bunch of houses and buildings.

Mills' paper reveals some interesting statistics about the construction cost of solar-thermal technologies: $3,000 per kilowatt of capacity, but estimated to drop to $1,500 per kW over the next "several" years. The New York Times last year quoted GE Energy executives giving construction costs for coal plants at $2,000 to $3,000 per kilowatt.

Ausra says it can generate electricity for 10 cents a kilowatt hour, which is close to the cost of natural gas, and it expects the price to drop even further. The company has received a lot of attention because of its compact linear Fresnel-reflector technology, and because it lined up two big-name VCs early: Vinod Khosla and Kleiner Perkins, where Al Gore is a partner. It's received $43 million in venture capital, and an additional $30 million at least in venture debt. It's planning a $100 million-to-150 million funding round later this year.

Ausra, for now, sells power to utilities. In total, it's announced real commitments for 1,500 megawatts of solar power deployments from California's Pacific Gas & Electric (1000 MW) and Florida Power and Light (500 MW). Fishman, however, says the company has several thousand more megawatts of deals in the pipeline. A recent deal between a different solar player, Abengoa, and Arizona Public Services, for a 280-megawatt plant had the following terms: 30 years, $4 billion.

Still, there are reasons to be skeptical. For one, companies have been piling into the solar-concentrating space. Stirling Energy Systems, SkyFuel, Solel, BrightSource, Rocketdyne, Abengoa and the aforementioned eSolar are all working on using mirrors to concentrate the sun's energy in one way or another. That's a lot of competition for a still-small chunk of the energy business.

Perhaps a more fundamental question is: Can all these prospective plants actually get built? Conceptually, solar thermal is a real bright spot in an otherwise depressing renewable-energy landscape, but until there are dozens of functional plants, it will be hard to know what kind of engineering costs these facilities are going to run into. And that's assuming that the storage technologies being discussed turn out to work. There's a long road from a prototype plant in Bakersfield to providing 90 percent of the nation's electric needs. For one, the nation's electricity-transmission infrastructure would have to change considerably as well, but that's a topic for another post.

Jeremy Carl, a research fellow in Stanford's Program on Energy and Sustainable Development, and a noted sane proponent of cleanish coal, saw scaling up the solar thermal plants as the major problem.

"In the time frame we have it is incredibly difficult to scale these sorts of new technologies up to the point where it becomes meaningful to the global energy system," Carl wrote in an e-mail to Wired.com. "There are always shortages of engineers who understand the technology, systems integrators, people to build components, etc."

Other environmental groups, however, level the same criticism at carbon capture and sequestration, which aims to trap carbon dioxide emissions from coal burning and bury them underground.

Carl also questioned whether or not the solar-thermal plants could approach the 100 percent reliability that grid-electricity users have come to expect.

"The Tesla guys are finding out the hard way that 99 percent reliability is not acceptable in a consumer mass-market product like a car," Carl said. "The same is even more true for power sources."

In the near term, these companies will be feeding off states in the southwestern United States that have built solar requirements into their renewable energy dictums. Nevada, Arizona, New Mexico and Colorado all require between 15 and 20 percent of their power to come from solar sources. Solar-thermal is the only technology that could realistically deliver that type of power. Any sort of system that puts a price on emitting carbon dioxide -- either a carbon tax or a cap-and-trade framework -- would be helpful because it would penalize coal and aid cleaner technologies.

Ultimately, though, these companies want to dominate the grid. As Mills wrote in the paper, solar-thermal "is probably the only currently available technology which can be considered for a globally dominant role in the electricity sector over the next 40 years." To achieve a dominant role globally, including China and India in the picture, they'll have to fulfill Google's dream of making RE < C, i.e., making renewable energy less expensive than coal.