Huge flywheels will secure the frequency in the UK

As fossil fuel-fired power plants are replaced by electricity from solar and wind energy, the power of the electricity grid decreases. Large turbines, for example, in coal-fired power plants contribute to a swing block that helps to maintain the frequency at 50 Hz in the event that a generator falls at another power plant.

In the UK, there was a major blackout in August last year when the frequency dropped to 48.88Hz. More than a million people were without electricity.

One way to quickly correct the frequency if needed is through quick-start gas power plants or batteries. But in Scotland, another method is now being tested.

New design from General Electric

Two huge flywheels will be installed near the Keith Resort. Norwegian company Statkraft won a contract from power grid operator National Grid to balance the power grid. To help, Statkraft will take newly designed flywheels, or “rotary stabilizers,” which will be manufactured by General Electric. The technology was used previously in electrical grid contexts, but it does not appear to have occurred at this scale.

The UK power grid is one of the most advanced in the world, in terms of reliability and share of renewable energy. We are therefore excited to be able to add this new way to operate the power grid, says Julian Leslie, Network Director at National Grid ESO, in a statement.

200 tons of rotary mass

Each flywheel has a mass of 200 tonnes and rotates at 500 rpm. Reactive capacity is 65MV (same as one MW unit). The energy stored in the flywheel is 450MW (which can be converted to 0.125MWh, which never happens in such contexts). The flywheel loss while waiting to be in use is approximately 770 kW.

Statkraft hopes the plant will be up and running next winter. The cost is estimated at 25 million pounds, equivalent to 290 million crowns.