Offshore construction begins on RWE’s flagship Sofia

  • 05 September 2023
  • The 1.4-gigawatt offshore wind project is one of the world’s largest single offshore wind farms – operational in 2026
  • Prysmian’s Leonardo da Vinci vessel will lay the first sections of high voltage direct current (HVDC) export cables
  • Sofia will play a key role in helping the UK achieve its net zero ambitions

Offshore construction has officially started at RWE’s 1.4 gigawatt (GW) Sofia Offshore Wind Farm, to install essential subsea cable infrastructure from the UK’s north east coast to the wind farm site on Dogger Bank, in the central North Sea.

Cable contractor Prysmian’s high-tech Leonardo da Vinci vessel will lay the first section of high voltage direct current (HVDC) export cable, ready to transport green electricity from the wind farm back to the UK coast, and ultimately into the UK transmission network.

The work marks a significant milestone for the project, with Sofia representing a more than £3billion investment in the UK’s energy infrastructure by RWE. The wind farm will make a significant contribution towards the country’s net zero targets, and be capable of generating enough clean electricity equivalent to meeting the needs of over 1.2 million typical UK homes.

Sven Utermöhlen, CEO RWE Offshore Wind: “Sofia is RWE’s largest renewable construction project to date, and its furthest from shore. The project is setting new standards in terms of addressing innovation, sustainability, and engineering challenges. The laying of the first section of export cable represents the culmination of 13 years of planning, preparation, and diligence, as well as a huge amount of support from suppliers and stakeholders alike. Building a project of this size and scale is a great opportunity to demonstrate our expertise in delivering offshore wind energy around the globe.”

Sofia Offshore Wind Farm is located on Dogger Bank, 195 kilometres from the nearest point on the UK’s north east coast, and will have a single offshore converter platform, with the electricity generated transported to landfall 220 kilometres away in Redcar, Teesside.

Prysmian’s 170-metre-long vessel will operate out of the Port of Middlesbrough and will lay two 130 kilometre sections of cable in parallel. It will start its cable laying work from just off the Teesside coast between Redcar and Marske-by-the-Sea. One end of each of the two sections of subsea cable will be pulled underwater from the vessel through cable ducts that were installed earlier this year. The cable will pass below the beach, sand dunes and road before emerging at the landfall construction compound. The cutting-edge vessel will then move away from the coast, laying the full length of cable along its set route towards the offshore wind farm. 

Installation of two remaining 90km sections of marine export cable is planned for 2024. By late 2024, Leonardo da Vinci will have laid four sections of ±320kV HVDC marine export cables with XLPE insulation, totalling 440 kilometres plus the accompanying communications cables.

Onshore construction has been underway in Teesside since June 2021, to construct the project’s onshore converter station and cable corridor. The laying of the first sections of export cable marks the start of a three year offshore construction phase.

The ongoing offshore construction works will include the arrival of the project’s offshore converter platform, due to make the journey from Batam, Indonesia to the UK in 2024. Also planned for next year is the start of installation of the 100 extended monopile foundations and array cables.

The wind farm will use 100 Siemens Gamesa 14 megawatt (MW) offshore wind turbines (SG 14-222 DD), the most advanced offshore wind turbine technology available, and is scheduled to be completed by the end of 2026. Forty-four of the project’s 100 turbines will be equipped with recyclable blades. Operations and maintenance activities for the wind farm will be located at RWE’s new offshore wind operations base ‘Grimsby Hub’, which will also support Triton Knoll Offshore Wind Farm and future projects.

RWE is the UK’s largest power producer and has ambitions to invest up to £15 billion gross in new green technologies and infrastructure in the UK by 2030.