California Utility Signs Agreement for Solar Thermal Power

November 28, 2007

Photo of a series of long, thin flat mirrors mounted in circular hoops that allow them to tilt to follow the sun. The mirrors are reflecting sunlight onto a pipe that is mounted above them.

The Ausra technology employs nearly flat mirrors that direct sunlight onto an overhead tube, in which water is boiled into steam.
Credit: Ausra, Inc.

The Pacific Gas and Electric Company (PG&E) announced early in November that it has signed an agreement to purchase power from a 177-megawatt solar thermal power plant. Ausra, Inc. plans to build the facility in San Luis Obispo County, which is located north of Los Angeles on the California coast. The facility will cover about one square mile and will feature Ausra's "Compact Linear Fresnel Reflector" technology, which employs nearly flat rotating mirrors to concentrate the sun's heat onto a series of "receiver" pipes. Unlike most solar thermal power plants, which pump oil or other heat transfer fluids through the receiver pipes and then use that hot fluid in a boiler, the Ausra technology pumps water through the receiver pipes and vaporizes it under the sun's heat. Ausra has filed an Application for Certification for the plant with the California Energy Commission (CEC), which must grant approval before construction begins. If approval is granted, the plant is expected to begin generating power in 2010. See the PG&E press release and the Ausra Web site.

Meanwhile, the CEC has completed its initial staff assessment of a solar thermal plant proposed for Victorville, which is northeast of Los Angeles. The proposed plant would use parabolic troughs—U-shaped mirrors that focus the sun's heat onto a receiver tube—to produce enough steam to generate 50 megawatts of power, while turbines fueled with natural gas will boost the net output of the plant to 563 megawatts. The initial assessment produced a number of questions for the City of Victorville, which submitted the plant proposal. Before the CEC will give its approval, the city will need to address issues relating to air quality, endangered species protection, historic items, and water management, as well as the effects of solar glare and thermal plumes on the operations of a nearby airport. See the CEC press release.