[OKC] How to use solar energy at night and a new study on nuclear power

[Shauna Struby]

A new study,
<http://climateprogress.org/wp-content/uploads/2009/01/nuclear-costs-2009.pd
f> "Building Risks and Costs of New Nuclear Power," puts the cost for
nuclear power at 25-30 cents per kilowatt hour  -- triple current U.S.
electricity rates - and double the cost of  solar-thermal power using salt
technology (see article below). This nuclear power study fills a critical
gap in the current debate over nuclear power - transparency. As the study
notes:

 

"Utilities promoting new nuclear power assert it is their least costly
option. However independent studies have concluded new nuclear power is not
economically competitive."

 

But here's something that is economically competitive . a few highlights
from How to use solar energy at night: 

 

And  <http://www.aps.com/> Arizona Public Service Co. (APS) has contracted
with Abengoa Solar to build a 280-megawatt solar thermal power plant-dubbed
<http://www.aps.com/solana> Solana or "sunny place"-70 miles (110
kilometers) southwest of Phoenix on nearly 2,000 acres (800 hectares) of
land. "One of the great things about molten salt technology is that you can
get more out of the pure solar resources, more energy out of the same
facility," says Barbara Lockwood, manager for renewable energy at APS. "It's
an alternative that provides us with additional green energy," as much as
1,680 megawatt-hours when cloudy or after sunset.

 

Electricity from a
<http://www.sciam.com/article.cfm?id=sunny-outlook-sunshine-provide-electric
ity> solar-thermal power plant costs roughly 13 cents a kilowatt-hour,
according to Glatzmaier, both with and without molten salt storage systems.

That price is still nearly twice as much as electricity from a
<http://www.sciam.com/blog/60-second-science/post.cfm?id=coal-war-can-the-fo
ssil-fuel-be-cle-2008-12-23> coal-fired power plant-the current cheapest
generation option if environmental costs are not taken into account. But
Arizona's APS and others can then use solar energy to meet the maximum
electricity demand later in the day. "Our peak demand [for electricity] is
later in the evening, once solar production is trailing off," Lockwood says.
That's "the reason we went that direction and are so interested in storage
technology."

 

Ultimately, it will come down to how much value policymakers and consumers
put on electricity that is renewable and emissions-free. "If we start
valuing carbon and force a coal plant to go
<http://www.sciam.com/article.cfm?id=future-of-clean-coal-tied-to-success-of
-carbon-capture-and-storage> carbon-free via sequestration then we're at or
over 10 cents per kilowatt-hour from coal," Mancini says. "Any of these
technologies can get to that same 10 cents level with [molten salt] storage.
Then the market will make the call."

 

Article here:

 

How to Use Solar Energy at Night

Molten salts can store the sun's heat during the day and provide power at
night

By David Biello 

 

Near Granada, Spain, more than 28,000 metric tons of salt is now coursing
through pipes at the
<http://www.solarmillennium.de/Technologie/Referenzprojekte/Andasol/Die_Anda
sol_Kraftwerke_entstehen_,lang2,109,155.html> Andasol 1 power plant. That
salt will be used to solve a pressing if obvious problem for solar power:
What do you do when the sun is not shining and at night?

The answer: store sunlight as heat energy for such a rainy day.

Part of a so-called parabolic trough
<http://www.sciam.com/article.cfm?id=sunny-outlook-sunshine-provide-electric
ity> solar-thermal power plant, the salts will soon help the facility light
up the night-literally. Because most salts only melt at high temperatures
(table salt, for example, melts at around 1472 degrees Fahrenheit, or 800
degrees Celsius) and do not turn to vapor until they get considerably
hotter-they can be used to store a lot of the sun's energy as heat. Simply
use the sunlight to heat up the salts and put those molten salts in
proximity to water via a heat exchanger. Hot steam can then be made to turn
turbines without losing too much of the original absorbed solar energy.

The salts-a mixture of sodium and potassium nitrate, otherwise used as
fertilizers-allow enough of the sun's heat to be stored that the power plant
can pump out electricity for nearly eight hours after the sun starts to set.
"It's enough for 7.5 hours to produce energy with full capacity of 50
megawatts," says Sven Moormann, a spokesman for
<http://www.solarmillennium.de/index,cat1.html> Solar Millennium, AG, the
German solar company that developed the Andasol plant. "The hours of
production are nearly double [those of a solar-thermal] power plant without
storage and we have the possibility to plan our electricity production."

Using mirrors to concentrate the sun's energy is an old trick-the ancient
Chinese and Greeks both used it to start fires-and modern power plants
employing it might provide a significant source of renewable energy without
any
<http://www.sciam.com/article.cfm?id=from-bad-to-worse-with-greenhouse-gas-e
missions> greenhouse gas emissions.

That is a step forward in its own right, but such power plants are limited
to generating energy only when there is sunshine. So engineers have tried a
number of different technologies to store the sun's energy so that such
power plants can be more broadly employed. They have tried
<http://www.sciam.com/article.cfm?id=storing-the-breeze-new-battery-might-ma
ke-wind-power-reliable> batteries but too much of the energy that goes in is
not returned, and they tend to be too expensive, according to an analysis
from the  <http://www.nrel.gov/> National Renewable Energy Laboratory (NREL)
in Golden, Colo. Compressing air or pumping water uphill are more promising,
but the opportunities to do that are limited by the number of caverns and
the availability of water and reservoirs.

 

More here :::
http://www.sciam.com/article.cfm?id=how-to-use-solar-energy-at-night 

 

 

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