Iowa Utilities Propose A Wind-Powered Energy Storage Plant
A group of municipal utilities in Iowa are proposing to build a
unique power plant that will combine wind power with a compressed
air energy storage (CAES) facility. The proposed Iowa
Stored Energy Plant (ISEP) will use a 100-megawatt wind power
facility to pump air into an underground aquifer, compressing the
air. During times of peak power demand, the compressed air will
be supplied to 200 megawatts of combustion turbines that are fired
with natural gas, allowing the turbines to operate at high efficiencies.
The group places the cost of the ISEP at $215 million and hopes
to launch the project this fall, with a startup date in mid-2006.
CAES plants work by replacing a combustion turbine's compressor
with a source of compressed air. Nearly two-thirds of the natural
gas supplied to a conventional combustion turbine is used to drive
the compressor, so a CAES plant burns much less natural gas than
a conventional combustion-turbine plant.
ISEP Background:
The centerpiece of the Iowa Stored Energy Plant is compressed air
energy storage (CAES). CAES is a technology to store energy in the
form of compressed air in an underground facility for use in later
generation. CAES is in use in two other locations, a 290-megawatt
plant in Germany and a 110-megawatt plant in Alabama, and is a well-known
and cost-effective generation technology. A 2,700-megawatt CAES
plant has also been proposed by CAES Development Company, LLC for
construction in Norton, Ohio.
The Iowa Stored Energy Plant project proposes two innovations to
the CAES concept:
First, the compressed air will be stored in an underground aquifer,
rather than in a cavern as in other CAES projects.
Second, wind energy will be used to compress air, in addition
to the off-peak power used elsewhere.
When generation is needed, the compressed air is released to drive
natural gas-fired combustion turbines. The compressed air reduces
the need for 2/3 of the natural gas normally used in a turbine.
A separate section of the underground aquifer will also be used
for storing natural gas. Gas storage will allow the facility and
other gas utilities to buy natural gas when prices are lower.
Preliminary cost estimates show that a configuration of 200 megawatts
of CAES generation capacity with a 100-megawatt wind farm is the
most economical. Although wind energy is the lowest-cost new generation
option available, it is not reliable by itself. CAES acts as a “battery”
for wind energy and makes it a dispatchable electrical resource.
 While
the Iowa Stored Energy Plant incorporates wind directly into its
design, it will also indirectly promote the use of wind energy in
the region. CAES will be operated to follow loads and fill in where
other generation is unavailable or uneconomical. Wind generation
output is highly variable, but CAES can fill in the gaps for wind.
This could expand the role of wind in the region's generation mix.
The combination of natural gas and wind for electric generation
lowers carbon emissions significantly and uses the abundant Iowa
wind resource. In the future, a carbon neutral power plant, replacing
natural gas with shelled corn, another important Iowa resource,
can be envisioned.
Although sites in other states are being explored for CAES, Iowa
is in the forefront of stored energy development. First, Iowa possesses
a site that is ideal for the CAES power plant and wind farm. An
underground aquifer near Fort Dodge contains the dome structure,
capacity, and porosity needed for storage of both compressed air
and natural gas. Second, Iowa has vast wind resources and corn acres.
Income from leases of underground aquifer storage rights and for
placement of wind turbines would give local landowners an ongoing
revenue stream. At a $215 million construction cost, the Iowa Stored
Energy Plant would provide an economic benefit not only for the
Fort Dodge area, but for the entire state of Iowa.
Contact:
Patty Cale-Finnegan
Energy Services Coordinator
Iowa Association of Municipal Utilities
1-800-810-4268
pcale@iamu.org
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