Sofia Offshore Wind Farm

The Sofia offshore wind farm, previously known as the Dogger Bank Teesside B wind farm, is a 1.4GW wind power development project located off the north-east coast of England, UK. Upon completion, it will become one of the world’s biggest offshore wind farms.

The Sofia wind power project is being developed and will be operated by Innogy through its wholly-owned subsidiary Sofia Offshore Wind Farm (SOWFL). Innogy is a subsidiary of the German energy company E.ON.

Forewind, a consortium between SSE, Equinor (formerly Statoil), Statkraft, and Innogy, obtained a development consent order (DCO) for the wind farm in August 2015, while Innogy secured 100% ownership of the project in August 2017.

Innogy won a contract for difference (CfD) for the 1.4GW wind farm from the UK Department for Business, Energy and Industrial Strategy (BEIS) held in September 2019, while the final phase of six-month pre-construction site investigation was initiated in June 2020.

The onshore construction works for the £3bn ($3.74b) wind farm project are expected to be started followed by a final investment decision (FID) in 2021, while the offshore works are expected to be started in 2023.

The Sofia offshore wind farm is expected to commence operations in 2024 and achieve the full capacity to power approximately 1.2million UK households annually in 2026. 

Location and site details

The Sofia offshore wind farm will be developed on a 593km² site in the Dogger Bank area of the North Sea, approximately 195km off the north-east coast of the UK. The wind farm will be located in 35m-deep waters.

The other Dogger Bank wind farms being developed near the site are Creyke Beck A, Creyke Beck B, and Teesside A that have 1.2GW installed capacity each. 

Sofia offshore wind farm make-up 

The 1.4GW Sofia offshore wind farm will comprise 100 SG 14-222 DD wind turbines from Siemens Gamesa with a rated capacity of 14MW each, and a 66kV/320kV offshore substation to transmit the electricity output.

With 222m-diametre rotor and 108m-long carbon and fibreglass blades, each direct-drive turbine will have a swept area of 39,000m²_.

Mounted on a monopile foundation driven into the seabed, each turbine will stand approximately 262m tall.

The SG 14-222 DD turbine, ideal for high-wind offshore location, is the latest, most powerful offshore wind turbine model from Siemens Gamesa which is expected to be market-ready in 2024. Sofia will be the first wind farm in the UK to use this turbine model.

Power transmission

The electricity generated by each and every turbine will be collected and transmitted through a network of approximately 370km of 66kV inter-array cables to the offshore substation of the wind farm.

At the offshore substation, the electricity will be converted from 66kV alternating current (AC) to 320kV direct current (DC).

The electricity from the offshore substation will be further transmitted through a 220km-long high-voltage direct current (HVDC) subsea export cable which will make landfall at the Teesside coast between Redcar and Marske-by-the-Sea.

From the landfall location, a 7km-long HVDC onshore cable will transfer the electricity to a new converter station near the village of Lazenby, from where it will be fed into the National Grid through six 2km-long AC cables connecting an existing substation at Lackenby.

Contractors involved with the Sofia offshore wind farm

Siemens Gamesa Renewable Energy received a conditional order to supply 100 SG 14-222 DD wind turbines as well as provide comprehensive service and maintenance services for the Sofia offshore wind farm in June 2020.

Fugro was engaged to perform the geophysical and geotechnical surveys for the Sofia offshore wind power project in February 2020.

Mott MacDonald was engaged as the front-end engineering and design (FEED) contractor for the subsea HVDC voltage source converter (VSC) interconnector for the Sofia offshore wind power project.