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This report, Volume 2 in a series, documents the construction of the
first U.S. compressed-air energy storage (CAES) plant from August 1988
to May 1991. By providing valuable information on construction and cost
schedules for Alabama Electric Cooperative's (AEC) plant, this report
will help utilities evaluate and build CAES plants.
BackgroundEPRI has studied CAES, a potentially viable storage alternative, since
1975. CAES plants use both electric energy and fuel. For each kWh of
electrical output, approximately 0.80 kWh compressor input plus 4570
Btu (HHV) fuel input are required. Previous experience with CAES was
one 290-MW-4h German plant in service since 1978. AEC's plant improves
fuel consumption by about 25%, with a first-of-a-kind recuperator. AEC
selected a joint venture bidder and construction proceeded on a
turnkey-contract basis. EPRI provided the following: the recuperator
and specialized plant-performance instrumentation and analysis;
technical and engineering support to review design and construction
efforts; and an engineer of record to document project progress.
Objectiveo To document the engineering record of the first U.S. CAES plant from
the beginning of plant construction to acceptance by the host- utility
for commercial dispatch.
o To summarize general conclusions and lessons learned about the
overall plant, cavern, and turbomachinery.
ApproachEPRI's site-and-field engineer documented the AEC CAES plant's
construction history in an engineering diary. Additional data from a
number of sources supplemented the diary. These sources included
information from engineering review meetings, from plant
specifications, and site visits by key EPRI and technical-support
engineers. Also adding to the data were engineering audits and
extensive photography of the plant during construction. The report
documented lessons for both successful activities and those needing
ResultsACE's construction was completed in approximately 40 months. This was
two months longer than scheduled and mainly due to completion delays in
the electrical/control system. Cavern construction, from initial
drilling to complete solution mining proceeded smoothly in about 25
months. The recuperator was installed in April 1990. Air was first
injected into the cavern in April 1991. On March 31, 1991, the
generator was first synchronized and the plant was accepted for
commercial dispatch on May 31, 1991. Among the lessons learned from the
project are the following: a turnkey-type contract, such as AEC's
contract, is cost-effective; prefabricated buildings should result in
cost reduction; and extensive design evaluation should focus on the
impact of emergency startup/shutdown transients on recuperator,
turbomachinery, and motive-air systems. Also of interest are these
observations: the recuperator and motive air systems should have
full-cavern pressure to avoid using large pressure relief systems; and
separate controls for compression and generation shutdowns enable
repairs to one system without affecting the other.
EPRI PerspectiveThis first U.S. CAES plant uses a cavern (solution-mined in a salt
formation) for air storage. Appropriate geology (porous- media,
hardrock or salt) is available in 85% of the United States. Future
plants also can take advantage of improved technology through more
modern cycles, such as those involving humidified air (CASH-ES).
Engineers based the turbomachinery in the AEC plant on
combustion-turbine technology with turbine-inlet temperatures of 1600
degrees Fahrenheit or less. As a result of EPRI-directed work with
Westinghouse and Dresser-Rand, future plants can take advantage of more
modern expanders with inlet temperatures up to 2350 degrees Fahrenheit
compared to the AEC plant, engineers estimate this higher
inlet-temperature turbine technology can lower CAES plant costs by 20%.
By outlining a method to reduce CAES-plant costs with standard
components, EPRI has made further information on construction and
engineering available. For more information, see EPRI report TR-103209,
"Standardized CAES Plant: Design and Construction."
For further information about EPRI, call the EPRI Customer Assistance Center at (800) 313-3774 or email email@example.com