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- HUNTSVILLE, Alabama (ENS)
- The National Aeronautics and Space Administration (NASA) is investigating
to determine if solar collectors can be constructed in outer space to capture
solar energy and beam it down to earth.
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- Twenty years after rejecting the idea as costly and impractical,
NASA has awarded more than $6 million in contracts to assess the feasibility
of constructing what the agency calls "sun towers" that could
capture 1.2 billion watts of solar power.
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- Using highly efficient photovoltaic cells and replacing
metal towers with plastic, the sun towers would have 22 mile solar collectors
in a stationary orbit more than 22,000 miles high.
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- NASA estimates the solar energy beamed down to earth
could supply the electricity needs of 1.2 million homes.
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- NASA has awarded contracts to 23 organizations to work
for nine months to see if the concept of space stations would be feasible
by 2015. The companies will meet soon at the Marshall Space Flight Center
in Alabama.
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- Microwave beams are the most practical technology to
transmit the energy, but microwaves burn anything that crosses its beam,
including planes and birds. NASA opposes using laser light, because lasers
could be perceived as a potential weapon.
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- Research in Japan is evaluating transmission by lasers
from the space station to airships in the atmosphere, which would convert
the energy into microwaves for beaming to earth. The receiving antennas
would be up to 15 miles in diameter.
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- Each sun tower would mount a series of 200-meter solar
collectors along the 22 mile structure, and stay in a geosynchronous orbit
22,000 miles high.
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- This positioning means each sun tower would stay in the
same place with relation to the Earth, as communications satellites do
today. Concentric prisms would focus the sun's rays onto the solar cells,
and robots would be needed to maintain the system.
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- The units would be beyond the reach of a space shuttle,
and would have to be constructed on earth.
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- Cost estimates run from $1 to $2 billion for a 1.2 gigawatt
plant. NASA officials say they want to reduce costs to five cents per kilowatt
hour, close to price for conventional electricity.
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