Ken Silverstein EnergyBiz Insider Editor-in-Chief

It sounds mind boggling. And to some extent, it is. But the idea is easily explained: Compressed Air Energy Storage technology keeps underground compressed air so that it can later be used to create electricity. There's a lot of smart people trying to make systems to store wind when it is really blowing and then to release that air when it is not. The underground storage facilities that exist now typically rely on fossil fuels to compress and subsequently release the compressed air for power generation.

The Iowa Association of Municipal Utilities is considering a 300-megawatt plant that is comprised of a 100 MW wind farm and a 200 MW compressed air energy storage facility. The association has spent more than $1.5 million studying the concept. The plant would serve as a battery to store the intermittent wind power. If it gets built, construction costs would be $215 million and the facility would generate income from leases of underground storage rights and for wind turbine placement.

"Adding renewable energy and a different type of storage space to the equation has the potential to make an already effective technology even more attractive," says Patti Cale-Finnegan, energy services coordinator for the association. The aquifer is located near the electric transmission grid and a gas pipeline. Part of the facility may be used to store natural gas, making the project of interest to gas as well as electric utilities.

While the concept of compressed air energy storage is more than 30 years old, only two such plants exist -- a ten-year-old-facility in McIntosh, Ala., about 40 miles north of Mobile, and a 23-year-old plant in Germany, both in caverns created in salt deposits. Palo Alto, Calif.-based Electric Power Research Institute has estimated that more than 85 percent of the United States has geological characteristics to accommodate underground compressed air energy storage.

Take the Alabama Electric Cooperative: It pumps air underground at night. During the day and at peak times, that air is released and heated using a small amount of natural gas. The heated air flows through a turbine generator to produce electricity. In conventional gas-turbine power generation, the air that drives the turbine is compressed and heated using natural gas. On the other hand, compressed air energy storage technology needs less gas to produce power during periods of peak demand because it uses air that has already been compressed and stored underground.

The Obstacles

Compressed air energy storage can make environmental and economic sense. Nearly two-thirds of the natural gas in a conventional power plant is consumed by a typical natural gas turbine because the gas is used to drive the machine's compressor. In contrast, a compressed air storage plant uses low-cost heated compressed air to power the turbines and create off-peak electricity, conserving some natural gas.

To be sure, obstacles to storing wind underground stand in the way. The disadvantage is that energy is lost when it is "pumped" into the cavern and then re-extracted as compressed air. Some estimates say that it could be as high as 80 percent. That, in effect, means that the selling price must accommodate that shortcoming, which may drive up rates for consumers. Also, building storage can be pricey, which might make some prospective projects infeasible.

"Wind power is variable and so storage is the answer," says Brian Parsons, project manager for the National Wind Technology Center in Golden, Co. "And storage is a good concept, but it is expensive." In the meantime, he says that gas turbines and hydropower facilities that are able to ramp up quickly and integrate wind at low costs are alternatives to energy storage.

Ultimately, though, storage projects could bear fruit. Gas prices have been volatile and gone as high as $15 per million BTUs during the winter. Under those circumstances, an investment in underground storage could pay for itself over time. Moreover, if the nation develops an energy policy that pushes renewable power sources, the idea may catch on.

If that happens, developers say that they can win approval from stakeholders. Because storage is used with renewable forms of power, capital costs can be more readily recouped. And furthermore, wind and solar energy, for example, could be stored whenever it is generated and then released on demand -- helping to negate the argument that those power sources are intermittent and therefore unreliable.

Consider a project by the Sandia National Laboratories and Haddington Ventures. Together, they are trying to determine the feasibility of creating storage in a 2,200 foot deep mine near Cleveland, Ohio. If the storage facility gets built, it would be a 2,700 megawatt facility and sell wholesale power to other generators or large industrial users.

"We know it works," says Steve Bauer, who is leading Sandia's efforts. "This is just bigger than anything else."

Compressed Air Energy Storage can be a cost effective solution because it would replace expensive "peaking" units that provide power during the hottest summer days or the coldest winter nights. The storage features would bring down the cost of power as well as reduce the stress on base load plants that would otherwise be needed. By extension, compressed air energy storage plants would minimize the release of harmful emissions created by fossil fuel-fired generators.

High energy prices are definitely harmful. But the chief benefit of such conditions is that environmentally-friendly technologies that once seemed distant might now be just around the bend. Researchers and developers alike say that when it comes to energy storage, they aren't just blowing smoke.

For far more extensive news on the energy/power visit:  http://www.energycentral.com .

Copyright © 1996-2005 by CyberTech, Inc. All rights reserved.