# Flywheels and small mechanical stores

Spinning rotors that store motion, and springs and hydraulic accumulators.

Source page: https://www.materialinsights.org/energy/e_flywheels/

Storage · Mechanical · No. 80

- Storage
- Duration: Seconds to minutes
 Storage · Mechanical · Foundation · Energy

Carbon-fibre rotors spinning at about 16,000 rpm in vacuum help keep the grid's frequency steady, cycling up to 175,000 times.

Chart: Illustration: Flywheels and small mechanical stores

##### Where it comes from

Chart: Map of where it comes from

A motor spins a heavy rotor of steel or carbon fibre, and to discharge the same machine becomes a generator as the rotor slows.

##### Three things to know

1. Stored energy rises with the square of speed, so modern rotors spin very fast inside vacuum casings.
2. A flywheel can lose up to 15% of its charge an hour, so it suits seconds and minutes, not overnight storage.
3. China's Dinglun plant cost about USD 1,600 per kW in 2024, about half Stephentown's USD 3,450 (both calculated).

##### The journey

1. 1 **Grid power**Motor spins the rotor up to speed
2. 2 **Spinning rotor**Steel or carbon fibre in vacuum
3. 3 **Magnetic bearings**Keep friction losses low
4. 4 **Generator**Rotor slows, returning power in seconds
5. 5 **Grid service**Frequency control, backup, power quality

##### Go deeper pick a tab to open it in full

## Other sections

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