Thứ Sáu, 11 tháng 1, 2013

Storing Solar Energy - Using Thermal Power Plants

Thermal-power plants which store heat intended for over cast days could possibly address many of the difficulties with storing solar energy.
Solar advocates like to brag that merely a couple of hundred square kilometers worth of photovoltaic solar panels placed in Southwestern deserts could possibly power the United States. Their particular strategies contain a warning, needless to say: with no backup energy plants or costly purchases in massive batteries, flywheels, or additional energy-storage systems, this solar power supply would likely vary significantly with each and every passing cloud (along with the daily rise and fall as well as seasonal ebbs and flows). Solar power startup company Ausra, located in Palo Alto, believes they have the answer: solar-thermal-power plants that will convert sunlight into steam and efficiently store heat for cloudy days.
"Fossil-fuel supporters normally point out that solar cannot get the job done, that solar cannot operate in the evening, solar cannot run the overall economy," says David Mills, Ausra's founder and chairman. "That is certainly accurate if you do not possess storage." He admits that solar-thermal plants tend to be the most effective due to the fact storing heat is much simpler when compared with storing electrical energy. Mills estimates that, as a result of that benefit, solar-thermal plants suitable of holding sixteen hours worth of heat could possibly supply over 90 percent of existing U.S. energy requirement at rates competitively priced with fossil fuel as well as natural gas.
Major utilities are choosing the theory. In July, the Pacific Gas and Electric Company (PG&E) agreed upon a 25-year deal together with Ausra rival Solel Solar Systems of Beit Shemesh, Israel, to purchase energy from a 553-megawatt solar-thermal plant which Solel will be building in California's Mojave Desert. The plant can provide 400,000 homes throughout northern and central California as soon as it is completed in 2011. Florida Power & Light, in the meantime, hired Solel to upgrade the 1980s-era solar-thermal plants it manages in the Mojave.
Ausra, on the other hand, is discussing together with PG&E to provide electrical power via a 175-megawatt plant which it intends to construct in California, that it secured $40 million in venture funding this month.
Everything that distinguishes Ausra's design will be its general simplicity. In traditional solar-thermal plants such as Solel's, a lengthy trough of parabolic mirrors concentrates sunlight on a pipe filled up with a heat-transfer liquid, usually some type of oil or brine. The liquid, subsequently, generates steam to drive a turbine and create electrical power. Ausra's solar collectors utilize mass-produced and therefore inexpensive flat mirrors, and in addition they concentrate light onto pipes filled up with water, therefore directly generating steam. Ausra's collectors generate a reduced amount of power, however that power is cheaper to generate.
One megawatt's worth of Ausra's solar collectors have been generating steam in New South Wales, Australia, ever since 2004; the steam is fed directly into the turbines of a mainly coal-fired power plant. The last part of the system--a proprietary heat-energy-storage system--should become ready by 2009.
Mills is not going to state precisely what materials his company's system will probably heat, despite the fact that a number of the latest solar-thermal plants by Ausra competitors--including one in Nevada which launched this particular summer as well as the two being constructed in Spain near Granada--plan to make use of molten-salt storage. Molten salts tend to be cost-effective salt solutions that will soak up significant energy after they melt and offer up that energy once they freeze.
Precisely what Mills can easily declare for sure is the fact that Ausra's storage system will certainly reduce its power-generation expenses. This is the incredible statement because energy storage may cost perhaps up to twice the price of electricity coming from photovoltaics or wind turbines.
Heat storage is a lot more successful compared to electricity storage: merely two to seven percent of the actual energy is wasted any time heat is banked inside a storage system, in comparison with losses of at the very least fifteen percent whenever energy is stashed in a battery. A bigger factor, claims Mills, would be the fact storage makes it possible for thermal plants to work with more affordable turbines.
The end result is that Mills vows that increasing storage as well as cost savings because of economies of scale as well as reduced price of investment capital (simply because banks know more about solar-thermal technologies) will certainly reduce Ausra's existing ten to eleven cents per kilowatt-hour expense of power by 50 percent. By 2010, he is expecting solar thermal to give California with standard power more affordable when compared with natural gas, at the moment established by the state at 9.2 cents per kilowatt-hour.
Read More about how scientists are storing solar energy to give homeowners the ability to use solar energy at night.

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