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Compressed Air Energy Storage (CAES)

1978
Underground salt cavern for Compressed Air Energy Storage in thermodynamics applications.

(generated image for illustration only)

Compressed Air Energy Storage (CAES) is a method to store energy generated at one time for use at another time. At a utility scale, energy is stored by compressing air and storing it in an underground reservoir, such as a salt cavern. When electricity is needed, the pressurized air is heated and expanded in a turbine, driving a generator.

CAES plants operate in two modes: compression (charging) and expansion (discharging). During charging, typically at night when electricity prices are low, an electric motor drives a compressor to pressurize air, which is then injected into a large underground storage cavern. The process of compressing air generates a significant amount of heat. In conventional diabatic CAES systems, this heat is treated as waste and dissipated into the atmosphere. During discharge, the compressed air is released from the cavern, heated using a fuel like natural gas (to increase its volume and energy output), and then expanded through a turbine to generate electricity. The need for natural gas reduces the overall efficiency and environmental benefit. More advanced designs, known as adiabatic CAES (A-CAES), aim to store the heat of compression in a thermal energy storage medium and use it to reheat the air during expansion, eliminating the need for fossil fuels and significantly increasing round-trip efficiency from ~40-50% for diabatic to a theoretical >70% for adiabatic systems.

UNESCO Nomenclature: 3322
– Thermodynamics

Type

Physical System

Disruption

Incremental

Usage

Niche/Specialized

Precursors

  • Boyle’s law and the ideal gas law
  • invention of the air compressor
  • development of gas turbines
  • geological survey techniques for identifying suitable underground caverns

Applications

  • utility-scale energy storage
  • load shifting for power grids
  • providing reserve capacity for grid stability
  • integration of large-scale wind farms

Patents:

NA

Potential Innovations Ideas

  • isothermal caes systems that aim to compress and expand air at a constant temperature
  • underwater caes using hydrostatic pressure of the sea
  • small-scale caes systems using above-ground pressure vessels
  • hybrid caes-battery systems for combined power and energy services
  • using depleted gas fields as storage reservoirs
  • advanced adiabatic caes with high-temperature thermal storage
  • co-location with industrial plants to utilize waste heat
  • liquid air energy storage (laes) as a cryogenic variant
  • caes systems integrated with direct air capture of co2
  • mobile caes units for temporary power needs
Related to: CAES, compressed air, energy storage, underground cavern, turbine, compressor, load shifting, grid storage, diabatic, adiabatic.

Historical Context

Compressed Air Energy Storage (CAES)

1970
1974
1974
1978
1980
1980
1980
1970
1972
1974
1975-06-01
1980
1980
1980
1980

(if date is unknown or not relevant, e.g. "fluid mechanics", a rounded estimation of its notable emergence is provided)

10th year anniversary

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