Heat from the sun boils water to run a steam turbine generator, which delivers power to the grid.
BrightSource generates electricity using an approach called concentrated solar power, in which computer-controlled mirrors, known as heliostats, focus the sun's heat to boil water and turn a steam turbine.
These could be among the first full-scale power plants in the nation to turn powdered coal into a synthetic natural gas that is burned in a gas turbine whose exhaust gas powers a steam turbine.
Areva bought the Mountain View, Calif. company Ausra, a company that has developed a system of reflectors that concentrates and directs sunlight to create steam and spin a turbine.
The output is a hot, high-pressure mix of steam and CO2 that powers a turbine.
Legge notes that newer fossil fuel plants use the heat that was once wasted to turn an extra steam turbine, a process known as combined cycle.
The oil, which glows purplish when hot, flows to an adjacent power plant, where it boils water into steam that runs a turbine, and is pumped back to do it all over again.
From there the trash is fed into three boilers that burn at 2, 000 degrees, heating water to create steam that spins a 60-megawatt turbine.
Geothermal power plants turn hot water into steam or vapor to run a turbine and generate electricity, after which the water is injected back into the underground geothermal reservoir.
The resulting steam drives a standard electricity-generating turbine.
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Ivanpah is a solar concentrator project, using fields of mirrors, known as heliostats, to concentrate sunlight onto a solar receiver on top of a tower. (This project when finished will include 173, 000 heliostats.) The concentrated sunlight is used to heat water, generating steam which is used to turn a traditional turbine and generator to produce electricity.
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Combined-cycle gas turbines, which use hot exhaust gases from one turbine to generate steam to turn a second one, can transform 6, 800 Btu of gas into a kilowatt-hour of electricity, enough to light one lightbulb for ten hours.
To supply the extra juice, utilities turn on inefficient single-cycle gas turbines, which turn 25% of the fuel's energy into electricity, as opposed to 45% for combined-cycle plants that use turbine exhaust to make steam to run a second generator.
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