New Ways to Catch Rays
With evidence mounting that the global warming trend is
accelerating, finding solutions to our dependence on fossil
fuels for our growing energy needs is becoming increasingly
urgent. A significant part of the solution may well lie in
solar energy. Today, a host of scientists and entrepreneurs
are busy developing new means of harnessing the abundant,
renewable, and entirely free energy of the sun. In this slide
show, take a look at six of the hottest new solar
technologies.—Evan Schwartz
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Thermal trough This is the world's largest
solar power plant, situated on a stretch of land larger
than New York's Central Park. Out in the Mojave Desert,
three hours from Los Angeles, rows of trough-shaped
mirrors collect and concentrate the sun's heat and
ultraviolet radiation to cook tubes of synthetic oil up
to 750°F. The hot oil is piped to a generating
station to flash-boil water, making steam that drives a
traditional power turbine. Built in the mid-1980s, the
Kramer Junction plant has been reliably providing about
350 megawatts of peak power to the L.A. grid, enough to
power more than 150,000 homes.
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Thermal trough (continued) A second major
"thermal trough" plant of this kind, called Nevada Solar
One, is expected to open in spring 2007 just outside Las
Vegas, Nevada. Improved technology will provide 64
megawatts of power to the grid, enough for 32,000 homes.
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Mirrored dish Resembling large satellite
dishes, these giant mirrored dishes collect solar
radiation and use it to generate electricity in a novel
way. Each dish bears its own Stirling engine, which
works by using heat to expand a hot gas that drives
pistons to produce electricity. Developed by Stirling
Energy Systems, early versions are in use at Sandia
National Laboratories in New Mexico.
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Mirrored dish (continued) Two large
California utilities have signed contracts to buy 800 to
1,750 megawatts of electricity from 32,000 to 70,000 of
these Stirling dishes, to be located in southern
California deserts (see artist's rendering at right).
Construction is slated to begin in late 2008.
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Thin film The solar films seen on the roof
of this home aren't as efficient as silicon panels in
converting sunlight into electricity. But the materials,
which are made by United Solar Ovonic, are so flexible
that they can be made into aesthetically pleasing
shingles.
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Thin film (continued) Flexible thin-film
modules form the solar roof of New York's Stillwell
Avenue subway station. It's one of the world's largest
thin-film, building-integrated installations. Sixty
thousand square feet of panels generate 210 kilowatts of
power, enough to meet two-thirds of the station's energy
requirements.
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Highly concentrated sunlight This is one of
three High Concentration Photovoltaic arrays operating
at Nevada's Clark Power Station. These giant panels,
produced by Amonix Corp., use optical lenses to
concentrate an intense amount of sunlight onto solar
cells. Since each lens channels "250 suns" worth of
light to each square in the panel, the same amount of
electricity can be produced using a fraction of the
silicon material typically required. Each array
generates 25 kilowatts of electricity, enough to power
about a dozen homes.
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Solar paint Imagine generating electricity
via the paint on your house or business. Nano-solar
paint, now under development, works just like a silicon
solar panel but at a fraction of the cost. At its heart
is a dark, sunlight-absorbing paint coated onto the
surface of aluminized mylar, which conducts electricity.
A protective clear layer of indium tin oxide that covers
the paint also conducts electricity. When sunlight
strikes the paint, electrons are knocked loose, reaching
wires that channel electricity to the home.
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Sun-grown biofuel This is a bioreactor that
recycles carbon dioxide emissions from a traditional
power plant. The apparatus traps the carbon within
ordinary algae cells, which multiply through natural
photosynthesis. This prototype bioreactor, created by
GreenFuel Technologies Corp., was originally tested on
the rooftop of a power plant at MIT. More recently, a
larger version was installed at the Redhawk natural gas
power plant in Arlington, Arizona.
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Sun-grown biofuel (continued) After the
algae cultures trap the carbon, most of the water is
removed, and the green sludge is put in large tubes and
shipped to a conventional biodiesel processing plant,
where liquid biogas is produced for diesel cars and
trucks.
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interactive version. The text to the left is provided for printing purposes.
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Evan Schwartz is a writer and producer for "Saved By the Sun"
and the author of
Juice: The Creative Fuel That Drives World-Class Inventors
(Harvard Business School Press, 2004).
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March 2007
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