Sofia Completes Turbine Installation, Enters HVDC Commissioning
RWE has successfully completed the installation of all 100 turbines at the Sofia Offshore Wind Farm in the UK North Sea, reaching a key construction milestone at one of the largest offshore wind projects in the world. The final Siemens Gamesa SG 14-222 DD turbine was placed on 10 June 2026, with testing and commissioning of the project's HVDC distribution system now continuing before the turbines can be brought online.
Turbine Installation Campaign
Turbine installation at Sofia began in March 2025 using Cadeler's Wind Turbine Installation Vessel (WTIV) Wind Peak, operated by Siemens Gamesa Renewable Energy (SGRE). Operating out of the Port of Hull, Wind Peak transported and installed turbine components in batches of six sets per trip, supported at the offshore site by IWS's service operation vessel IWS Seawalker. The campaign reached the halfway point in September 2025 before concluding in June 2026. The Sofia project was the first turbine installation campaign completed by Wind Peak since the vessel's delivery in August 2024.
Mikkel Gleerup, CEO of Cadeler, said the completion of turbine installation at Sofia marked an important achievement for the project and for Wind Peak, and that Cadeler was proud to have supported RWE and Siemens Gamesa in delivering a project that will make a meaningful contribution to the UK's renewable energy supply.
Turbine Specifications
Each of Sofia's 100 turbines is rated at 14 MW, stands 252 metres tall at its highest point, and features 108-metre blades with a 222-metre rotor diameter. Half of the turbines — 50 units in total — are equipped with specialist RecyclableBlades, representing the first large-scale deployment of this technology at an offshore wind farm in the UK. The recyclable blade sets, comprising 150 blades in total, were manufactured by SGRE and assembled at its facility at Green Port Hull.
HVDC Transmission System
Sofia's electrical output will be transmitted to shore via a ±320 kV HVDC system with a rated capacity of 1,320 MW, supplied under a £600 million (approximately $827 million) contract by a consortium of GE Renewable Energy's Grid Solutions and Sembcorp Marine. GE Grid Solutions is responsible for the engineering, procurement, construction and installation of the two HVDC converter stations — one offshore and one onshore — while Sembcorp Marine designed, constructed and is commissioning the offshore converter platform (OCP).
The OCP comprises a 17,000-tonne topside and jacket foundation structure piled into the seabed, located approximately 220 kilometres from the nearest shore. At the time of its design, it was the most powerful and most remote offshore converter platform ever built. The system utilises GE Grid's second-generation voltage source converter (VSC) valve and incorporates GE's eLumina™ HVDC Control System. Prysmian was contracted to design, supply, install and commission the HVDC cable connecting the offshore and onshore converter stations, with the onshore connection made to the national grid substation at Lackenby.
Testing and commissioning of the HVDC distribution system is ongoing at the Sofia site. The turbines will be connected to the HVDC system once that commissioning phase is complete.
Project Background
Sofia is located on the Dogger Bank, approximately 195 kilometres off the north-east coast of the United Kingdom, spanning a consented area of 593 square kilometres. The project is being developed by RWE with a total investment of approximately £3 billion and secured a Contract for Difference (CfD) in a UK government competitive auction. Once fully operational, Sofia will generate up to 1.4 GW of renewable electricity — enough to meet the annual power requirements of approximately 1.2 million typical UK homes, contributing roughly half of the annual electricity needs of the north-east of England.
Full commercial operation is targeted for September 2026.
