Custom built synchronous condenser units now in operation at Uniper’s Grain power station site helping to deliver a low carbon electricity system


• Two new custom built synchronous condenser units at Uniper’s Grain power station site have come into commercial operation, providing dedicated inertia and voltage control services to the National Grid system operator. 
• Follows two synchronous condenser units coming online at our Killingholme power station site in 2022. 
• Uniper now the biggest provider of grid stability services under Phase 1 of National Grid ESO’s Stability Pathfinder. 
• The services delivered by Uniper will enable more renewable generation to come onto the electricity system, whilst maintaining a stable power system as the UK transitions to a net zero carbon future. 
• Uniper’s investment in these innovative solutions at Grain comes at the same time studies are underway to decarbonise the production of electricity at Grain power station. 

Two newly built synchronous condenser units have come into operation at our Grain power station site in Kent, and are now supplying essential grid stabilising services to the British electricity system operator, National Grid ESO.

Built on the site of the former Grain A oil power station, the custom designed, rotating grid stability technology is connected to the existing onsite 400kV substation, providing inertia and voltage control to the electricity grid without the need to generate power.

Siemens Energy has worked with Uniper to install and commission the equipment at the site, which consists of two new build synchronous condensers and flywheels.

Synchronous condenser units are key to enabling the introduction of more renewable technology to generate electricity in Great Britain. Up to now thermal power stations, with their large spinning generators, have provided inertia as a by-product of generating electricity. With the growth of wind and solar, separate dedicated facilities are needed to help manage grid stability, because renewable generation is not connected to the grid in the same way and cannot provide inertia, which is essential to keep electricity supplies at the right frequency.

This comes almost a year after the two units at our Killingholme power station site, became operational. Uniper was awarded four six-year contracts by National Grid ESO in 2020, to provide inertia services and voltage control to the grid under phase 1 of its Stability Pathfinder at both  Killingholme and Grain power station sites.

This latest development is one of a number of projects we are exploring at our Grain site, as we work towards decarbonising the production of electricity at the existing natural gas fired power station. Options being considered include the use of alternative fuels, such as hydrogen and retrofitting post combustion carbon capture technology.

Mike Lockett, Uniper UK Country Chairman and Group Chief Commercial Officer Power

We are immensely proud to see the synchronous condenser units up and running at our Grain power station site.

Along with the units already operating at our Killingholme site, Uniper is providing services that have a vital role in helping keep the British electricity system secure, stable and at the right frequency, enabling more solar and wind power to come online as the UK transitions to a net zero carbon future. Uniper is now delivering all of the vital stability services it has been contracted to supply to National Grid ESO under phase 1 of its Stability Pathfinder to 2026, putting us at the forefront of this market.

Our investment to deliver this innovative service runs alongside our ambitious decarbonisation strategy to make our European power generation assets carbon neutral by 2035 – by refuelling with hydrogen or biofuels, or retrofitting carbon capture technology.

Mike Lockett, Uniper UK Country Chairman and Group Chief Commercial Officer Power

Maintaining grid stability and security of supply is a vital part of Britain’s energy strategy. Working with Uniper, we are proud to have developed this customised technology solution at Grain. The intermittent nature of renewable energies means that grid stabilisation technologies, like synchronous condensers, will play an important role in our energy transition.

Steve Scrimshaw, VP of Siemens Energy UK&I

Notes to editors:

What is inertia and why is it needed? 

The National Grid Electricity System Operator (NGESO) must maintain the electricity system at 50 Hz in order to keep power supplies secure. In the UK, electricity is generated at power stations at the same frequency. Rapid changes in the frequency of electricity can create instability in the system if demand for power exceeds supply, or there is too much power being supplied to the system. If this breaches a certain limit, this can cause equipment and domestic appliances to disconnect or be damaged, as well as power cuts. Inertia in the energy system slows down the rate at which frequency changes, helping the grid to remain stable at the right frequency and voltage level. The more inertia in the system, the slower the change in frequency, which gives the grid operator more time to react and manage system stability effectively.

As we move towards a net zero future and more of our electricity is generated from renewable sources, one of the challenges for the energy system operator is how to replace the inertia services that are, in the main, provided as a by-product of thermal generation. The new and repurposed synchronous condenser units at Killingholme and Grain consist of a large piece of spinning machinery which connects to the grid but doesn’t generate any power. Instead, the mass of the generator, connected to a flywheel rotating 3,000 times per minute, retains kinetic energy, known as inertia, in the electricity system, which helps the grid remain stable at the right frequency and voltage level.

About Uniper

Düsseldorf-based Uniper is an international energy company with activities in more than 40 countries. With around 7,000 employees, it makes an important contribution to security of supply in Europe. Uniper’s core businesses are power generation in Europe, global energy trading, and a broad gas portfolio.

Uniper procures gas – including liquefied natural gas (LNG) – and other energy sources on global markets. The company owns and operates gas storage facilities with a capacity of more than 7 billion cubic meters. Uniper plans for its 22.5 GW of installed power-generating capacity in Europe to be carbon-neutral by 2035.

The company already ranks among Europe’s largest operators of hydroelectric plants and intends to further expand solar and wind energy, which are essential for a more sustainable and autonomous future.

Uniper is a reliable partner for communities, municipal utilities, and industrial enterprises for planning and implementing innovative, lower-carbon solutions on their decarbonization journey. Uniper is a hydrogen pioneer, is active worldwide along the entire hydrogen value chain, and is conducting projects to make hydrogen a mainstay of the energy supply.


About Uniper UK

In the UK, Uniper owns and operates a flexible generation portfolio of seven power stations, a fast-cycle gas storage facility and two high pressure gas pipelines, from Theddlethorpe to Killingholme and from Blyborough to Cottam. We also have significant long-term regasification capacity at the Grain LNG terminal in Kent, to convert LNG back to natural gas.


About Siemens Energy

Siemens Energy is one of the world’s leading energy technology companies. The company works with its customers and partners on energy systems for the future, thus supporting the transition to a more sustainable world. With its portfolio of products, solutions and services, Siemens Energy covers almost the entire energy value chain – from power generation and transmission to storage. The portfolio includes conventional and renewable energy technology, such as gas and steam turbines, hybrid power plants operated with hydrogen, and power generators and transformers. A majority stake in the wind power subsidiary Siemens Gamesa Renewable Energy (SGRE) makes Siemens Energy a global market leader for renewable energies. An estimated one-sixth of the electricity generated worldwide is based on technologies from Siemens Energy. Siemens Energy employs around 92,000 people worldwide in more than 90 countries and generated revenue of €29 billion in fiscal year 2022. www.siemens-energy.com.


This press release may contain forward-looking statements based on current assumptions and forecasts made by Uniper SE Management and other information currently available to Uniper. Various known and unknown risks, uncertainties and other factors could lead to material differences between the actual future results, financial situation, development or performance of the company and the estimates given here. Uniper SE does not intend, and does not assume any liability whatsoever, to update these forward-looking statements or to modify them to conform with future events or developments.