December 5, 2007 4:00 AM PST

Storing sun and wind power

Storing sun and wind power
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When the sun sets or the wind dies down, renewable energy sources get a lot less reliable.

That's why large-scale electricity storage technologies are being pursued by a number of energy technology companies. Although none of these technologies are commonplace, they could fill a niche in the booming solar and wind industries and make renewable energy more economically compelling.

One company with a novel approach is Massachusetts-based start-up General Compression, which is building a wind turbine that compresses air and stores it underground in caves or other geological structures. The compressed air is drawn when needed and expanded to drive electricity generators.

A document on General Compression's Web site last month that has since been removed indicated it was looking for $30 million this fall to finance its expansion.

Earlier this month, Australian firm Cleantech Ventures made a "significant investment" in Smart Storage Pty to commercialize a hybrid battery for off-grid storage. The "ultrabattery" technology stems from research at Australia's national science agency.

Flywheels from companies like Beacon Power have been approved by regulators for maintaining a steady frequency over the grid as power demand fluctuates minute to minute. The flywheels--essentially a huge rotating cylinder--are designed to absorb energy when the grid is making excess energy and feed the energy back to meet shortfalls in supply.

Images: Making wind power that lasts all day

For several hours of storage, utilities are testing different battery technologies. Each of these techniques has different purposes and drawbacks but are getting serious consideration, say experts.

"There's been more going on in energy storage in the last six months than in decades (prior)," said Garth Corey, an electrical storage consultant and former Sandia National Labs scientist. "There are true benefits, but we haven't had the tools to do it."

An energy bill, now making its way through Congress, may include a provision that would boost the amount of renewable energy that electric utilities need to generate.

But even without higher renewable energy mandates, large-scale storage stands to make wind and solar--two of the fastest sources of power generation--more versatile.

Bottling wind power
Right now, electricity generators supply electricity to meet shifting demand. But unlike natural gas or coal-fired power plants, utilities cannot count on a wind farm or solar array to meet its peak demand needs, typically in the middle of the day.

One of the most promising techniques for addressing "peak power" is called compressed air energy storage (CAES), a storage method that General Compression intends to plug into.

This technique allows utilities to store hours' and even weeks' worth of electricity. The idea is to use power generators to compress air during off-peak hours, like during the middle of the night, and then tap into it later in the day, when they can command a higher price for electricity.

CONTINUED: Putting ideas to the test…
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Testing the system to ensure it works.
Posted by WheelerCub (25 comments )
Reply Link Flag
Posted by kadsanat (2 comments )
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This is some promising news.
I like the compressed air idea but it doesn't tell us about the energy trade-off so we don't really know if it is worth it or not. Batteries, 50% more or not, still aren't the answer. One loses so much in the power conversion that I'm not sure that we wouldn't have to have a wind turbine or solar panel every square mile in the US. I'm sure, sooner or later, someone will come up with the proper way to store AC power, until then, we are stuck with the traditional power sources. Coal, gas, and now atomic.
Posted by suyts2 (152 comments )
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We aren't stuck with coal gas nukes
Solar power plant companies already have other ways of storing power. Some use hot water or oil, while the most effective seems to be molten salt. The compressed air in caverns idea is the one in a proposal to convert the U.S. electric grid to 69% solar by 2050 using solar thermal and concentrating PV power plants in the southwest U.S.

Scientific American A Solar Grand Plan
<a class="jive-link-external" href="" target="_newWindow"></a>

Green Wombat has a bunch of articles about progress in California with solar thermal power plants.

<a class="jive-link-external" href="" target="_newWindow"></a>

Wind and solar complement each other. Wind is stronger generally at night, while solar obviously works only in daytime. Solar is strong during peak hours.

Using 1% of our southwest deserts with solar power plants would power the whole country.
1% of the Sahara Desert would power the whole world. Here's what Ausra, a solar thermal company says:

"Solar thermal power plants such as Ausra's generate electricity by driving steam turbines with sunshine. Ausra's solar concentrators boil water with focused sunlight, and produce electricity at prices directly competitive with gas- and coal-fired electric power."

"Solar is one the most land-efficient sources of clean power we have, using a fraction of the area needed by hydro or wind projects of comparable output. All of America's needs for electric power ? the entire US grid, night and day ? can be generated with Ausra's current technology using a square parcel of land 92 miles on a side. For comparison, this is less than 1% of America's deserts, less land than currently in use in the U.S. for coal mines."

There is an enormous amount of dis-information out there, trying to convince us that alternative energy can't do the job. Don't believe it.

Besides wind and solar there is a big potential with biomass to methane like Environmental Power Corp is doing.

"Wild Rose Dairy in Webster Township, WI is home to an innovative renewable energy facility powered by cow manure and other organic waste. The farm is home to 900 dairy cows, and an on-site anaerobic digester creates methane-rich biogas from their waste, which is used to generate 750 kilowatts of electricity per hour?enough to power 600 local homes 24/7."

"Environmental Power?s Huckabay Ridge is the largest renewable natural gas plant in North America, if not the world. Huckabay Ridge generates methane-rich biogas from manure and other agricultural waste, conditions it to natural gas standards and distributes it through a commercial pipeline. The purified biogas, called RNGĀ®, is generated by Environmental Power?s subsidiary, Microgy, and is a branded, renewable, pipeline quality methane product."

All the existing forms of energy get bigger subsidies than alternative clean energy, so don't be fooled by arguments about subsidizing them.
Nukes, coal, gas and oil are heavily subsidized.
In the case of oil hugely subsidized.
Posted by frflyer (5 comments )
Link Flag
Will be
Will be that true?
It's nice but who knows...
Paroles - <a class="jive-link-external" href="" target="_newWindow"></a>
Pedia - <a class="jive-link-external" href="" target="_newWindow"></a>
Posted by parolespedia (2 comments )
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Geological Stresses
I don't like the sound of the underground compressed air storage. What happens when the pressure increases underground to store energy and then the air is bled off to use the energy later? Any time you push against a rock and release the force, something gives, even if only a tiny amount. Now repeat that process hundreds or thousands of times. The result will be underground collapses. Would you want such things occurring beneath your house or office?
Posted by c|net Reader (856 comments )
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More like hot air
Nothing innovative here. Just another take on storing energy for later use much like water pump storage but with very low practicality. Imagine the volume of compressed air need to generate any meaningful MW of electricity.
Posted by oxtail01 (308 comments )
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Hot air?
The people who drew up a proposal to convert the U.S. grid to 69% solar by 2050 seem to think the compressed air in caverns idea is viable.

Scientific American A Solar Grand Plan
<a class="jive-link-external" href="" target="_newWindow"></a>

<a class="jive-link-external" href="" target="_newWindow"></a>
Green Wombat has several articles on current progress with solar thermal in California. Just scroll down to see all the stories.
Posted by frflyer (5 comments )
Link Flag
storage of the aeolian kinetic as hydro potential
The neighbourhood generation and storage system I call "Aeolian Hydro" uses a vertical wind turbine attached to an Archimedes screw to lift water into a storage cistern.

The storage cistern can release water to power microhydro generation when there is an unmet requirement for power.

This would convert intermittent wind energy into reliable microhydro power to provide energy when the sun isn't available.
Posted by wylde brumby (1 comment )
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Nice article! I think I would also read this I heard from my friends that it has good benefits. :D
Posted by bowking (6 comments )
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