National Grid Announces Preferred Bidder for Vital Sea Link Project

Subscribe to our free newsletter today to keep up to date with the latest construction and civil engineering news.

National Grid has named Siemens Energy as the preferred bidder to deliver the two converter stations required for the Sea Link project, a pivotal part of the United Kingdom’s evolving energy infrastructure. This announcement, made on April 14, 2025, places Siemens Energy at the center of a project designed to move renewable power more efficiently across the country.

The contract award follows a competitive procurement process and marks a significant milestone in National Grid’s plan to strengthen the national electricity network. The converter stations will form part of a high-voltage direct current (HVDC) connection that will run beneath the southern North Sea, linking Suffolk and Kent. Once operational, Sea Link will improve the flow of low-carbon electricity, helping to meet growing demand and support the shift to cleaner energy sources.

Sea Link’s scope and strategic importance for the UK grid

Sea Link is designed to carry up to 2 gigawatts of electricity through a 138-kilometer subsea route. It will use 525 kilovolt HVDC technology to transfer large volumes of power with minimal losses. The system will connect new converter stations in Friston, Suffolk, and near Richborough, Kent.

The route was selected to maximize capacity while limiting surface disruption, running primarily under the seabed and through the Thames Estuary. This design strengthens the eastern portion of the national grid, which is under pressure as offshore wind farms and other renewable generation projects come online.

The project’s importance lies in its ability to improve both regional and national energy flows. It will support a more balanced transmission system, which is increasingly critical as variable sources such as wind and solar generation increase across the country.

Details on Siemens Energy’s role and next steps

Siemens Energy will deliver converter stations at both ends of the subsea link. These stations convert alternating current (AC), used by households and businesses, into direct current (DC) for long-distance transmission and then back into AC at the receiving end.

This role follows a competitive procurement process conducted by National Grid. As preferred bidder, Siemens will now work with National Grid to finalize design and delivery planning. This phase sets the groundwork for full contract execution and scheduling.

Pending planning consent, construction is expected to begin in 2027. While the converter stations are just one part of the Sea Link infrastructure, they are essential to the system’s performance and reliability.

How Sea Link fits into the Great Grid Upgrade

Sea Link is a core part of National Grid’s broader Great Grid Upgrade, which aims to modernize the UK’s electricity infrastructure. This is the largest investment in the grid in generations and reflects the urgent need to adapt to new patterns of energy use and generation.

The UK’s electricity demand is rising due to the growth of electric vehicles, heat pumps, and industrial electrification. At the same time, a larger share of supply is coming from remote and variable sources. Addressing this challenge requires infrastructure that is more resilient and flexible.

Sea Link will provide an efficient high-capacity path between areas of surplus generation and areas of high demand. It reduces the need for local fossil fuel peaking plants and ensures renewable energy can be delivered where and when it is needed.

One of Sea Link’s major contributions is its ability to help deliver renewable power more effectively. The East of England, particularly Suffolk, is a growing center for offshore wind. Without sufficient transmission capacity, that energy could remain underused.

Sea Link resolves this challenge by enabling cleaner energy to travel south to Kent and beyond. It removes transmission bottlenecks, improving grid efficiency and lowering the risk of curtailing renewable output.

Once completed, Sea Link will contribute to a more robust and climate-aligned electricity system. It will play a key role in meeting net-zero targets, cutting carbon emissions, and delivering affordable, low-carbon energy to millions of homes and businesses.

Sources

• National Grid