Compressed-air and CO2 storage: Overview
Storing power as air squeezed into caves under our feet
What this tile covers Air or CO2 squeezed into caverns, bags or domes and expanded through turbines later. Share of use <.01% share of world stored energy (2025)Share of the world's stored energy (energy capacity held, TWh, latest year 2019 to 2026) across the forms with figures, about 22,551 TWh; fuel stocks dominate. Battery and other stores count capacity, not state of charge (calculated) CAES was 45% of more than 15 GWh of long-duration storage added in 2025 (Wood Mackenzie), about 6.8 GWh, plus the 1.8 GWh Feicheng plant connected in 2024; about 8.6 GWh. Older plants such as Huntorf and McIntosh are not added, so this is a lower bound. Source: Long-duration energy storage deployments rose 49% in 2025: Wood Mackenzie, Utility Dive.
Key facts
| Duration | Hours to days |
| Chain | Electrical → compressor → pressure (+ heat) → expander → electrical |
Included from the reference tables
- Diabatic and adiabatic CAES in caverns
- Underwater air bags
- Compressed CO2 (Energy Dome)
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