Scotland’s wind success story bolstered by £323m stability investment

  • Ten contracts awarded to improve long-term stability of electricity system

  • World-first large-scale use of grid forming converters to support increasing wind farm energy generation

  • ‘Fossil fuel-free power stations’ to provide cheaper, greener way of boosting stability

National Grid ESO is today announcing it has secured long-term stability to the electricity system in Scotland through world-first use of technology which will help manage growing wind farm capacity and help facilitate the transition to green energy.

Following a successful tender, the ESO has awarded 10 contracts to four companies worth a total of £323 million which provide net zero solutions to stability issues.

The imminent closure of nuclear power stations in Scotland and northern England, and the rising number of onshore and offshore wind farms in Scotland, will lead to a loss of inertia which poses a potential stability risk as inertia is needed to maintain frequency on Britain’s electricity system.

The winning 10-year contracts, starting in April 2024, will solve this issue in two ways. They will primarily solve insufficient Short Circuit Levels (SCL) - the amount of current that flows on the system during a fault - in various locations across Scotland. They will also provide a “green” form of inertia to help keep the electricity system stable, such as after a rare trip at a large power station.

Previously, inertia has been provided by coal or gas power plants but the ESO is now procuring inertia from carbon-free sources, which is not only significantly cheaper for consumers, but allows for greener system operation and more renewable energy to run.

The green solutions will provide the equivalent combined SCL and inertia of almost four coal-fired power stations.

Five of the successful solutions are synchronous condensers – ‘green’ motors with free-spinning flywheels which boost inertia and SCL. The other five solutions will comprise what is thought to be a world-first use of new grid forming converters at multiple locations across a region to improve inertia and SCL when disturbances occur in the electricity system.

Grid forming converters allow for a non-synchronous technology, such as batteries, wind, and solar to connect to the system, and mimic the effect of a power station but without using fossil fuels to provide inertia and SCL.

Julian Leslie, Head of Networks at National Grid ESO, said:

We believe this is the first time in the world where grid forming inverters have been used in multiple locations across a region to provide a system-wide solution to short circuit levels and inertia.

These zero-carbon stability-improving devices will enable more green electricity to run, are cheaper for consumers, and will allow the market to deliver as much wind generation as possible.

“This technology will help to future-proof Scotland’s wind generation success story, help us continue to operate the fastest decarbonising electricity network in the world and achieve our plans to be able to operate a zero-carbon grid by 2025.

Scotland’s Cabinet Secretary for Net Zero and Energy, Michael Matheson, said:

Accelerating the transition to renewable energy sources is a fundamental part of Scotland’s journey to net zero. Our plans include more than doubling the country’s onshore wind capacity and supporting the world’s largest floating offshore wind leasing round. ScotWind puts Scotland at the forefront of the global development of offshore wind and represents a massive step forward in our energy transformation.

This ambitious growth will require innovative, parallel work and investment in how we harness, store and manage electricity generated by renewable sources, and I welcome this investment from National Grid ESO, which demonstrates that renewables and other zero-carbon technologies are capable of providing the services needed for a secure electricity system.


Winning tenders



Technology type



Grid forming battery storage



Grid forming battery storage

TINZ Programme 1 ProjectCo 3 Ltd


Synchronous condenser

Zenobe Energy Limited


Grid forming battery storage

Zenobe Energy Limited

Kilmarnock South

Grid forming battery storage

Zenobe Energy Limited


Grid forming battery storage

WP Grid Services 3 Ltd


Synchronous condenser

WP Grid Services 8 Ltd


Synchronous condenser

WP Grid Services 1 Ltd

Thurso South

Synchronous condenser

WP Grid Services 9 Ltd


Synchronous condenser

Notes to Editors

  • The Stability Pathfinder Phase 2 tender attracted 225 proposals from 21 separate companies. Of these, 10 bids were chosen which delivered 11.55 GVA (Giga Volt Ampere) of SCL and 6.75 GVAs (Giga Volt Ampere seconds) of inertia. This represented a total investment of £323 million by ESO.

  • The contracts awarded follow Stability Pathfinder Phase 1 undertaken in January 2020 which secured 12.5 GVAs of inertia over a six-year period at a cost of £328 million.

  • More investment in stability services is expected to be announced by the ESO later this year. For more information on inertia read our website explainer.

Contact details

For media enquiries about National Grid ESO, please contact Alan Harris (07815 464323).