# Compressed-air and CO2 storage: Overview

Storing power as air squeezed into caves under our feet

Source page: https://www.materialinsights.org/energy/e_caes/overview/

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](https://utilitydive.com/news/long-duration-energy-storage-deployments-rose-49-in-2025-woodmac/814336), 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)

#### Also in Mechanical
[PHS Pumped hydro storage](https://www.materialinsights.org/energy/e_pumped_hydro/)[Grv Gravity storage](https://www.materialinsights.org/energy/e_gravity/)[Fly Flywheels and small mechanical stores](https://www.materialinsights.org/energy/e_flywheels/)[LAES Liquid air storage](https://www.materialinsights.org/energy/e_liquid_air/)

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 More on this tile in the tabs above: science and technology, engineering and performance, economics, impact and additionality, what to track.

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_caes/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_caes/correlation/index.md)
- [Science and technology](https://www.materialinsights.org/energy/e_caes/sg-sci/index.md)
- [Engineering and performance](https://www.materialinsights.org/energy/e_caes/sg-eng/index.md)
- [Economics](https://www.materialinsights.org/energy/e_caes/sg-econ/index.md)
- [Impact and additionality](https://www.materialinsights.org/energy/e_caes/sg-impact/index.md)
- [What to track](https://www.materialinsights.org/energy/e_caes/tracking/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_caes/links/index.md)