The solar-thermal industry took another step forward last week when Ausra Inc. announced it has secured more than $40 million in funding to build and operate utility-scale power plants. The announcement is the latest example that solar-thermal is gaining traction as a major solar technology.
Currently, nine solar-thermal (or concentrating) power plants in California’s Mojave dessert supply 350 megawatts of electricity annually. But that amount stands to increase more than four fold when planned projects come on line, including Southern California Edison’s 500-MW Stirling solar dish contract, Pacific Gas & Electric’s 553-MW deal with Solel and a 400-MW facility in the planning stages by BrightSource Energy.
Ausra, located in Palo Alto, California, is backed by Silicon Valley venture capital firms Khosla Ventures and Kleiner, Perkins, Caufield & Byers (KPCB). The company claims its thermal energy storage systems have an edge because they can provide on-demand power generation during both day and night. Moreover, it claims it can do so at just 10 cents per kilowatt-hour, which would be on par with the price of electricity from burning natural gas in California, if the state’s Public Utilities Commission chooses to impose a cost for CO2 emissions.
At this price, Ausra claims solar-thermal can provide all of the nation’s electricity needs. David Mills, chief scientific officer and founder of Ausra has been quoted as saying, “Within 18 months, with storage, we will not only reduce [the] cost of [solar-thermal] electricity but also satisfy the requirements for a modern society, supplying [electricity] 24 hours a day and effectively replacing the function of coal or gas.”
The Compact Linear Fresnel Reflector (CLFR) – Ausra’s core technology, conceived by Mills in the early 1990s – allows for greater ground coverage, lower weight and greater durability than precision-shaped parabolic mirrors, which have been the standard for solar-thermal applications. However, it is the company’s power-storage claims that are drawing the most attention.
Ausra plans to use pressurized steam to drive electricity-generating turbines during the night. It is believed that such a storage system would prove cheaper than battery storage and could drop the kilowatt-hour price even further, if storage times are sufficient. However, long-term steam storage has yet to be proven on a large scale, and there are risks associated with the high-pressure levels required.
Assuming the steam-storage system is effective, solar-thermal has tremendous potential. Mills and his colleagues presented a paper this week at the Solar Energy Society World Congress in Beijing claiming that such solar-thermal power plants could provide for the electricity needs of both California and Texas, and if scaled, are capable of meeting 96% of the national electricity demand.
According to Ausra’s executive vice president John O’Donnell, solar-thermal arrays covering 8,464 square miles of land – roughly 10% percent of the area managed by the Nevada Bureau of Land Management – could provide an equivalent to the nation’s total energy use in 2006.
Currently, Ausra has only one prototype solar array that provides additional steam to a coal-fired plant in Australia. But the company has acquired land in undisclosed location in southern California, presumably the future-site for a larger power plant.
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