Are Flywheels Bringing Grid Stability to the UK's Renewable Power Surge?                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      

As Britain retires its last coal and gas-fired generators, the National Grid is losing a critical stabilising asset: synchronous inertia. This property, inherent to heavy rotating turbines, helps maintain the grid’s 50 Hz balance. With renewables, particularly wind and solar power, lacking this inertia, technologies like flywheels are gaining traction as rapid-response solutions for grid resilience.

Flywheels store kinetic energy by spinning a rotor at high speeds in a low-friction environment. They can inject power in milliseconds to counter sudden frequency drops, making them ideal for frequency response and balancing. National Grid ESO’s Stability Pathfinder programme has already awarded contracts for flywheel projects, highlighting their growing role in keeping the grid stable as renewable penetration increases.

Flywheels offer several clear advantages in the current energy landscape:

Ultra-fast response: They can deliver energy in milliseconds, stabilising the grid instantly during sudden fluctuations.

Durability: Unlike batteries, flywheels experience little degradation over time, offering long service lifespans and consistent performance.

Sustainability: They are a low-carbon solution, producing no emissions and requiring minimal replacement of parts or materials.

Complementary use: Flywheels excel at short-duration, high-frequency balancing, making them ideal partners to longer-duration battery systems.

These strengths make them well-suited to the UK’s immediate challenge of balancing a renewables-heavy grid.

Despite their promise, flywheels also come with limitations:

Short storage duration: Flywheels are not designed for sustained discharge, meaning they cannot replace batteries or other long-duration storage technologies.

High upfront costs: The technology requires significant capital investment, particularly in large-scale applications.

Integration complexity: Flywheels must be carefully integrated with existing infrastructure, requiring specialist engineering and grid coordination.

Market positioning: Because they provide a niche service, developers must demonstrate value within regulatory and commercial frameworks, such as the ESO’s inertia contracts.

Addressing these challenges will be critical to scaling their role beyond pilot and demonstration projects.

The UK’s push for resilient energy infrastructure

Flywheels are already finding practical applications: from stabilising the National Grid to supporting motorway rapid EV charging infrastructure. With this, hybrid projects - combining flywheels with batteries - are also under development, creating flexible systems that can balance power both instantly and over longer durations.

These projects reflect a wider momentum in the UK’s push for resilient energy infrastructure.

And although Flywheels are certainly not any kind of ‘magical solution’ to the very real challenges the UK’s National Grid currently faces, they are part of a multi-layered solution to ensure stability while renewables grow.

Their value lies in filling a crucial gap, helping ensure the UK grid remains reliable, flexible, and future-ready.

Flywheels could fast become a vital part of the UK’s transition to clean energy, offering rapid stability and sustainable performance where traditional inertia is disappearing, and whilst challenges remain around cost, integration, and scalability, their ability to complement other storage and balancing solutions positions them as an important technology for the next phase of the UK’s energy transition.