NYT‘s Green Inc explains:
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….
[CEO Bill] 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….
“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.”