Britain’s energy operator is turning to an ancient technology—flywheels—to future-proof its grid. This move comes as traditional power plants that have long stabilized the system are being shut down and replaced by renewable energy sources.
For centuries, spinning metal devices known as flywheels have been used to provide inertia—a resistance to sudden changes in motion—for various machines, from a potter’s wheel to the steam engine. Now, grid operators are looking to this technology to add inertia to renewable-heavy electricity systems, aiming to prevent blackouts similar to the one that recently hit Spain and Portugal.
The Role of Flywheels in a Stable Grid
In an electricity grid, inertia is typically supplied by the large spinning generators found in coal-fired and gas power plants. This helps maintain a steady frequency by smoothing out fluctuations in supply and demand. However, renewable energy sources like solar and wind power do not add this crucial inertia and often cannot assist with other issues, such as voltage control.
Flywheels can mimic the rotational inertia of these power plant generators, spinning faster or slower to respond to fluctuations. According to David Brayshaw, a professor of climate science at the University of Reading, a system without spinning turbines is “more prone to fluctuations than it would be otherwise.” He added that as the grid incorporates “ever higher levels of renewables, we’re going to have to think about this more carefully.”
Flywheels and Batteries
The Iberian Peninsula, which relies heavily on renewables, experienced a blackout on April 28 after its grid was unable to handle a sudden surge in voltage and frequency deviations. This incident serves as a wake-up call, much like a 2019 outage that plunged parts of Britain into darkness following a drop in grid frequency. That blackout led the UK energy operator, NESO, to launch a “world-first” program to contract grid-stabilizing projects.
While both flywheels and batteries can add synthetic inertia to the grid, engineering professor Keith Pullen notes that steel flywheels can be more cost-effective and durable than lithium-ion batteries. Pullen, who also directs the flywheel startup Levistor, believes flywheels could become “a very, very important” technology. He warns that the grid will also face more instability from the “spikier demand” of electric cars, heat pumps, and data centers, which “the flywheel smooths out.”
Carbon-Free Inertia
One of the projects contracted by NESO is Norwegian company Statkraft’s “Greener Grid Park” in Liverpool. Operational since 2023, the site is a short distance from a former coal-fired power station. Instead of steam turbines, it now houses two giant flywheels, each weighing 40 tonnes (40,000 kilograms), which supply 1% of the inertia needed for the grid in England, Scotland, and Wales.
Each flywheel is connected to a synchronous compensator, a spinning machine that further boosts inertia and provides voltage control services in the region. Guy Nicholson, Statkraft’s head of zero-carbon grid solutions, proudly states, “We are providing that inertia without burning any fossil fuels, without creating any carbon emissions.” According to NESO, 11 other similar projects were operational in Britain as of 2023, with several more contracted.
‘Not Fast Enough’
A spokesperson for the Department for Energy Security and Net Zero told AFP that 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.”
However, Nicholson warned that “we aren’t building them fast enough to decarbonise the grid.” Britain aims to power its grid with clean energy 95% of the time by 2030 and completely switch to renewables in the following decade. Despite having sufficient solar and wind energy generation at times, Nicholson explained, “we still have to run gas turbines to keep the grid stable.”
Still, Britain and Ireland appear to be ahead of the curve in securing this grid-stabilizing technology. “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.”
