The Energy Story - Chapter 15: Solar Energy - 0 views
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Solar energy can also be used to make electricity.
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solar power plants, like the one in the picture to the right in California's Mojave Desert, use a highly curved mirror called a parabolic trough to focus the sunlight on a pipe running down a central point above the curve of the mirror.
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mirror focuses the sunlight to strike the pipe
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gets so hot that it can boil water into steam
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team can then be used to turn a turbine to make electricity.
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California's Mojave desert, there are huge rows of solar mirrors arranged in what's called "solar thermal power plants"
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this idea to make electricity for more than 350,000 homes
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problem with solar energy is that it works only when the sun is shining
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cloudy days and at night, the power plants can't create energy.
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solar plants, are a "hybrid" technology
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daytime they use the sun
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night and on cloudy days they burn natural gas to boil the water so they can continue to make electricity.
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form of solar power plants to make electricity is called a Central Tower Power Plant, like the one to the right - the Solar Two Project.
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Sunlight is reflected off 1,800 mirrors circling the tall tower
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mirrors are called heliostats
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move and turn to face the sun all day long
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light is reflected back to the top of the tower in the center of the circle where a fluid is turned very hot by the sun's rays.
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luid can be used to boil water
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make steam to turn a turbine and a generator.
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We can also change the sunlight directly to electricity using solar cells.
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Solar cells are also called photovoltaic cells
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PV cells for short
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be found on many small appliances
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calculators
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even on spacecraft
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first developed in the 1950s for use on U.S. space satellites
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made of silicon, a special type of melted sand.
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sunlight strikes the solar cell, electrons (red circles) are knocked loose
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move toward the treated front surface (dark blue color)
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electron imbalance is created between the front and back
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two surfaces are joined by a connector, like a wire, a current of electricity occurs between the negative and positive sides.
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individual solar cells are arranged together in a PV module and the modules are grouped together in an array.
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arrays are set on special tracking devices to follow sunlight all day long.
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electrical energy from solar cells can then be used directly
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used in a home for lights and appliances
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in a business
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Solar energy can be stored in batteries to light a roadside billboard at night
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energy can be stored in a battery for an emergency roadside cellular telephone when no telephone wires are around.
