Solar proponents love to run the math on how much (or how little) Southwestern desert one would need to cover with solar energy installations to power the United States. David Mills, founder and chairman of Palo Alto, CA solar startup Ausra, has his own estimate: 145 kilometers. Mills’ estimate is more credible than most, and not only because he’s a former president of the International Solar Energy Society.

Mills’ company is developing a less well known variant of solar power that could actually make solar power work as a total energy solution: solar thermal power plants that turn sunlight into steam and then use that steam to produce electricity in turbines (much as a nuclear or coal-fired power plant does). See my story on the MIT Technology Review website this morning — “Storing Solar Power Efficiently” — on why such plants’ ability to store heat sets them apart from other renewable energy options such as wind power and photovoltaics (solar panels that turn light directly into electricity).

Note that the potential of solar thermal power extends beyond the U.S.: China and India have sun-baked desert regions available for large solar installations, while Europe is just a transmission line away from North Africa.

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