Sofia wind farm: World's farthest fixed-bottom turbines completed in North Sea

Crews have finished erecting the 100th and final turbine at the Sofia wind farm, 121 miles off the English coast. The milestone, reached on 10 June, completes the offshore installation phase of the world’s farthest fixed-bottom wind farm and marks a major engineering feat in the middle of the North Sea.

The wind farm sits on the Dogger Bank, an area of shallow water that was once dry tundra connecting Britain to mainland Europe. Because the bank lies just 50 to 120 feet below the surface, engineers were able to drive steel foundations directly into the seabed. Without this geological quirk, a project this far from the coast would have required more expensive and less proven floating turbine technology.

The logistics of building 121 miles out

Building at this distance required a specialised installation vessel to transport and erect the massive machines. The vessel loaded six complete turbine sets at a time from Hull — including the tower sections, nacelles, and blades — before making the 121-mile crossing to the site.

Each of the 14-megawatt turbines stands 827 feet from the sea surface to the tip of its highest blade, featuring 354-foot blades that sweep an area of nearly 10 acres with every rotation.

"Sofia is our largest offshore construction project globally and remains on track and on budget," the project’s chief executive of offshore wind said, noting that the wind farm is on schedule to generate first power this year. The total cost of the project is estimated at $3.7 billion.

To bring the electricity back to land, developers had to lay 137 miles of high-voltage direct current cable to Redcar on the Teesside coast. The cable is longer than the distance from the shore to the wind farm because it must follow the contours of the seabed to avoid deep trenches.

An offshore converter platform, installed on a jacket foundation last year, will step up the power from 66 kilovolts of alternating current to 320 kilovolts of direct current to minimise transmission losses over the long journey home.

Operating at the edge of the horizon

The distance from land will also change how the wind farm is operated and maintained once it is fully commissioned.

While closer inshore projects allow technicians to make daily round trips from the coast, crews working at Sofia face a journey of nearly a day just to reach the site from the operator's base in Grimsby. Because winter weather in the central North Sea can halt boat transfers for days at a time, engineers have designed the turbines with extra sensors and tighter condition monitoring to reduce the need for physical visits.

Half of the turbines installed feature recyclable blades, marking the largest deployment of this technology on a British offshore wind project to date.

The wind farm is scheduled to reach full commercial operations in late 2026, when its 1.4-gigawatt capacity will be capable of powering roughly 1.2 million British homes.