North Sea grid link to share offshore wind power between five coastlines

Grid operators from five North Sea coastlines have signed an agreement to build a shared offshore network that would link wind farms in different national waters with a series of high-voltage subsea cables. The group, known as the Northern Seas Interconnector Partnership, says the first link could carry power within six years.

At present most offshore wind farms send their electricity along a single cable to their own coast. When the wind blows hard in one area and drops in another, there is often no easy way to move the surplus, and turbines are sometimes switched off even though power is needed elsewhere. The new network would connect wind farm hubs directly to each other as well as to shore.

Cables on the seabed

The first phase involves about 700 km of direct-current cable and three offshore converter platforms, each the size of a large office block standing on steel legs in the sea. Engineers estimate the system could move up to 6 gigawatts, enough to supply several million homes during windy periods.

The wind is almost always blowing somewhere across the North Sea, and the trick is getting the power to where people need it.

Henrik Aasland, the partnership's technical director, said the most difficult work would be agreeing common rules for who pays and who earns when electricity crosses borders at sea. Fishing organisations have asked to be involved early in route planning, after disputes elsewhere over cables laid through busy trawling grounds.

• Initial cable length: about 700 km

• Planned transfer capacity: up to 6 gigawatts

• Partners: five national grid operators

Supporters of the project argue that it would also reduce costs for consumers. When one country has spare wind power and its neighbour is burning gas to meet demand, a direct link at sea lets the cheaper electricity flow across without first landing on shore and travelling through congested land networks. Studies commissioned by the partnership suggest savings could run into hundreds of millions of euros a year once the full network is in place.

Independent energy analyst Corinne Albescu said the plan was technically sound but warned that cable factories and installation vessels are already booked for years ahead. The partners plan to publish a route survey next year, with seabed mapping due to begin once permits are granted.