Material Insights · Understanding the Material World

Compressed-air and CO2 storage

Air or CO2 squeezed into caverns, bags or domes and expanded through turbines later.

Storage · Mechanical · No. 81

  • Storage
  • Duration: Hours to days
Storage · Mechanical · Foundation · Energy

An Alabama plant has stored electricity as squeezed air in a salt cavern since 1991, enough for 26 hours.

Chart: Illustration: Compressed-air and CO2 storage

Where it comes from

Chart: Map of where it comes from

Compressors push air into salt caverns or mined caves; newer adiabatic plants keep the heat of compression to reach a design efficiency of 72.1%.

Three things to know
  1. Older plants waste the heat of squeezing and burn gas to reheat, returning only 29 to 52% of the power.
  2. Extra hours are cheap: a 100 MW plant falls from USD 295/kWh at 4 hours to USD 122/kWh at 10 hours.
  3. China's Feicheng plant cost about USD 115/kWh (calculated), against about USD 375/kWh reported for California's Willow Rock.
The journey
  1. 1 Spare powerDrives compressors when electricity is cheap
  2. 2 CompressionAir heats up as it is squeezed
  3. 3 Heat storeAdiabatic plants keep that heat
  4. 4 CavernSalt or rock holds air under pressure
  5. 5 ExpansionReheated air spins a turbine for power
Covered in Storing energy: from fuel stocks to batteriesEnergy
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