Showing Off With a Solar Thermal Salute

By Todd Woody

eSolar The solar thermal power producer eSolar shows off.

A picture was worth 24,000 mirrors when eSolar, a company based in Pasadena, Calif., that specializes in solar thermal power, transformed a vast field of heliostats at its Southern California solar farm into a Fourth of July tableau of the American flag and the Statue of Liberty.

The Google-backed start-up, which is building solar farms for Southern California Edison, P.G.&E. and El Paso Electric, uses software and imaging technology to create a dynamic parabola from tens of thousands of closely packed mirrors, focusing the sun’s rays on water boilers that sit atop towers. The intense heat vaporizes the water to create steam that drives an electricity-generating turbine.

As the holiday weekend approached, eSolar’s software engineers got a bit creative.

“The programmers have very accurate software control over the field,” said eSolar’s chief executive, Bill Gross, in an e-mail message Friday evening.

The company’s five-megawatt Sierra demonstration power plant northeast of Los Angeles deploys 24,000 mirrors — each one capable of being individually moved by computer. “To celebrate Independence Day,” the company announced at its Web site late last week, “eSolar’s Sierra SunTower power plant has employed this high-precision technology to declare energy independence.”

The display, of course, was designed to show off eSolar’s technological prowess — and it’s not the first time the company has deployed the gimmick.

Mr. Gross, the founder of the tech-incubator Idealab, contends that eSolar can deliver electricity cheaper than natural gas by using sophisticated algorithms to control inexpensive and lightweight mirrors called heliostats.

“The bigger picture here is that we invested like crazy in Moore’s Law instead of more steel,” he said, referring to Intel’s co-founder, Gordon Moore, who famously remarked that computer processing power doubles about every two years.

“We have such precise control over the field that we can do anything with the mirrors we want,” Mr. Gross said, “and this is proof of it.”