Handbook of Energy Storage for Transmission or ... - W2agz.com

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Figure 7
”Adiabatic” CAES Cycle
Compressed Air Storage Underground Facilities
The compressed air for the CAES plant may be stored underground, near the surface, or
aboveground. Underground storage media may be in any of the following man-made and
naturally occurring geological formations:
• Salt caverns created by solution mining (which typically costs about $1/kWh of energy
stored) or dry mining (which typically costs about $10/kWh stored [7, 8]).
• Underground rock caverns created by excavating comparatively hard and impervious rock
formations (either through new excavation for the CAES plant or in existing hard-rock
mines) (which typically costs $30/kWh stored [9]).
• Naturally occurring porous rock formations (e.g., sandstone, fissured limestone) from
aquifers or depleted gas or oilfields (which typically costs only $0.10/kWh stored [10]). It
should be noted the aquifers used for CAES contain non-potable salt water.
• Abandoned limestone or coalmines (which typically cost about $10/kWh stored [11]).
In general, a geological formation suitable for underground air storage must meet the following
requirements:
• The formation must have sufficient depth to allow safe operation at the required air pressure.
Compressed Air Energy Storage (CAES) Page 8