UK energy grid turns to flywheels for stable power supply

Britain’s energy operator is turning to an age-old technology to strengthen its power grid as traditional plants shut down and renewable systems take their place. The devices in focus are flywheels spinning metal disks that for centuries have provided stability to machines ranging from potters’ wheels to steam engines by resisting sudden changes in motion.

Today, grid operators see flywheels as a way to supply much-needed inertia to electricity networks dominated by renewables, helping prevent large-scale blackouts like the one that recently struck Spain and Portugal.

In conventional grids, inertia is created by massive spinning turbines in coal and gas plants, which help balance supply and demand by maintaining a steady frequency.

Solar and wind farms, however, do not contribute inertia, nor can they easily manage other grid challenges such as voltage control.

Flywheels can replicate the stabilizing role of turbines, adjusting their spin to smooth out fluctuations and keep the grid steady.

“The system becomes more vulnerable to swings without rotating turbines,” explained David Brayshaw, professor of climate science at the University of Reading. “As renewable energy expands, finding reliable solutions like this will become increasingly important.”

Flywheels and batteries

The Iberian Peninsula, which is powered by a high share of renewables, went dark on April 28 after its grid was unable to absorb a sudden surge in voltage and deviations in frequency.

Spain's government has since pointed fingers at conventional power plants for failing to control voltage levels.

It could serve as a wake-up call similar to a 2019 outage which plunged parts of Britain into darkness following a drop in grid frequency.

That blackout prompted UK energy operator NESO to launch what it called a "world-first" program to contract grid-stabilising projects.

Flywheels and batteries can add synthetic inertia to the grid, but engineering professor Keith Pullen says steel flywheels can be more cost-effective and durable than lithium-ion batteries.

"I'm not saying that flywheels are the only technology, but they could be a very, very important one," said Pullen, a professor at City St George's, University of London and director of flywheel startup Levistor.

In the coming years, Pullen warned the grid will also become more unstable due to greater, but spikier demand.

With electric cars, heat pumps and energy-guzzling data centres being hooked onto the grid, "we will have more shock loads... which the flywheel smooths out".

Carbon-free inertia
Norwegian company Statkraft's "Greener Grid Park" in Liverpool was one of the projects contracted by NESO to keep the lights on.

Operational since 2023, it is a stone's throw from a former coal-fired power station site which loomed over the northern English city for most of the 20th century.

But now, instead of steam turbines, two giant flywheels weighing 40 tonnes (40,000 kilogrammes) each whirr at the Statkraft site, which supplies 1% of the inertia for the grid needed in England, Scotland and Wales.

Each flywheel is attached to a synchronous compensator, a spinning machine that further boosts inertia and provides voltage control services in the Liverpool region.

"We are providing that inertia without burning any fossil fuels, without creating any carbon emissions," said Guy Nicholson, Statkraft's zero-carbon grid solutions head.

According to NESO, 11 other similar synchronous compensator and flywheel projects were operational in Britain as of 2023, with several more contracted.

'Not fast enough'

The government is "working closely with our industry partners who are developing world-leading technology, including flywheels, static and synchronous compensators, as we overhaul the energy system", a Department for Energy Security and Net Zero spokesperson told AFP.

But, "we aren't building them fast enough to decarbonise the grid", warned Nicholson.

Britain aims to power the grid with clean energy 95% of the time by 2030, before completely switching to renewables in the next decade.

"At the moment... we can't even do it for one hour," Nicholson said.

Even when there is sufficient solar and wind energy being generated, "we still have to run gas turbines to keep the grid stable", he explained.

Still, Britain and neighbouring Ireland seem to be ahead of the curve in procuring technology to stabilise renewable-heavy grids.

"In GB and Ireland, the system operators are leading by contracting these services," Nicholson said.

"On the continent, there hasn't been the same drive for that."

"I think these things are driven by events. So, the Spanish blackout will drive change."