U.S. Water News Online
DES MOINES, Iowa -- A group of Iowa cities intends to not
only harness the wind, but also capture it, store it underground and
use it to help make electricity when demand peaks.
Members of the Iowa Association of Municipal Utilities have
invested in a proposed power plant that would use wind turbines to
drive compressed air into underground aquifers. The air would be
released to generate electricity when needed.
It's a new twist on the idea of using wind energy in a way that
removes the unreliability of nature.
"Wind energy is dependent upon whether the wind is blowing or
not," said Bob Haug, executive director of the Iowa Association of
Municipal Utilities. "But if you can use the compressed air as a
storage medium, you get the certainty and the dispatchability that
you need to make wind compete."
The plant will use power from its own wind turbines, supplemented
by cheaper electricity bought at off-peak times, to force air into
rock formations at least 2,000 feet underground.
Current plans call for pressurized storage of tens of billions of
cubic feet of air in rock formations deep underground.
When it is needed, the air will be released and mixed with small
amounts of natural gas to power electricity-generating turbines.
"We've done quite a few studies in last couple of years and the
economics look very favorable," said Tom Wind, an energy consultant
who is a technical adviser on the Iowa Stored Energy Plant project.
Haug said the plant would use a third to half the amount of
natural gas needed by conventional turbines. However, instead of
natural gas, the plant could burn biomass such as corn stalks or
"In the future, we could get very close to a totally renewable
plant," he said.
The idea of pursuing the wind storage plant came as the municipal
utilities were considering investing in their own electricity
generating plant in 2001. The group first considered a coal-fired
plant, but began considering the increasing cost of environmental
regulations and the impact coal plants have on the environment.
"For us, it's really risk management," Haug said. "We know
generating electricity with coal produces mercury and that's
dangerous to the health of our children."
Global warming also focuses attention on renewable, clean energy
sources, he said.
The project, backed by 74 members of the municipal utilities
group, obtained a $1.2 million U.S. Department of Energy grant last
year to study the idea. It anticipates another $1 million this year
to continue to evaluate the project's feasibility. About $700,000 has
been raised by the utilities that support the idea.
Organizers also plan to seek support from major utilities, Wind
Only two other underground compressed air plants are in operation.
A plant in Huntorf, Germany, was built more than 23 years ago and a
plant in McIntosh, Ala., is 11 years old. Both store compressed air
in underground salt caverns.
Iowa's project is unique in that it would use wind power to store
the air and combine it with massive underground storage capacity.
The Germany and Alabama plants store hundreds of thousands of
cubic feet of air in a thermos-bottle shaped container installed in
the salt mines. The Iowa project would use naturally occurring
pockets embedded in sand or sandstone formations sealed by shale or
The area, which would cover hundreds of acres of land, could store
tens of billions of cubic feet of air, Haug said. That capacity would
allow the wind energy plant to compete with fossil fuel plants.
The ground above the storage area would remain undisturbed. The
group building the plant would need only to acquire leasing rights to
the underground storage, Haug said.
The Iowa project's initial plans call for construction of a 100
megawatt wind farm and a 200 megawatt compressed air energy storage
The plant is expected to cost about $300 million. A site has not
yet been chosen, but it likely will be in central Iowa, where
suitable underground formations are known to exist, Haug said.
Plans call for the plant to go online by 2010.
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