First U.S. "Power Tower" Lights Up California

clipped from www.scientificamerican.com In southern California's Antelope Valley, 24,000 silver-bright mirrors have been positioned to reflect light on two 50-meter-tall towers. And at 11:08 A.M. local time Wednesday, this concentrated light heated steam in those towers to turn a turbine—the first "power towers" in the U.S. to convert the sun's heat into electricity for commercial use. Dubbed Sierra SunTower, the power plant can produce five megawatts, enough to power roughly 4,000 local homes at full capacity—and provide the modular blueprint for larger plants in California and New Mexico, according to eSolar, the Pasadena start-up behind the power plant. "We call this a commercial demonstration," says eSolar senior vice president of engineering Craig Tyner. "A 46-megawatt commercial design will incorporate 16 of these towers, two of which we have at Sierra" as well as more than 200,000 mirrors capable of generating at least 90 gigawatt-hours of electricity per year.