Power producer RWE has announced that the first offshore turbine foundation for the Sofia Offshore Wind Farm in the Dogger Bank area of the Central North Sea has been installed.
RWE said that following the installation of subsea cable infrastructure, the installation of the first foundation marks the start of offshore construction within the array itself.
The foundation was installed by contractor Van Oord’s Aeolus vessel. This is the first of 100 monopile foundations that will be installed at the 593 sq km array.
Van Oord will be responsible for installing all of the foundations, under its engineering, procurement, construction and installation (EPCI) contract with RWE, which also covers array cables.
The monopiles are up to 8.8m in diameter, up to 92m in length and up to 1,530 tonnes in weight. They are being manufactured by EEW in Germany and then transported by barges to the UK’s Port of Tyne, which is serving as the storage and marshalling base for the foundations.
For the Sofia offshore wind farm, extended monopile foundations are being used, which Van Oord said eliminates the need for a transition piece.
To complete the foundations, the monopiles will be equipped with secondary steel components such as main access platforms, internal platforms, boat landings and upper ladders. These secondary steel components are being manufactured by various suppliers in the Netherlands and Poland before being transported to the Port of Tyne.
Van Oord intends to deploy its Calypso cable-laying vessel and Dig-it trencher later in 2024 to install 360km of array cables.
This comes after Van Oord previously collaborated with RWE on the Rampion, Humber Gateway, Robin Rigg and London Array wind farms.
The Aeolus vessel will install three foundations per cycle, with a transit time of up to 16 hours. While the duration of this phase of the campaign will depend on sea conditions, all 100 foundations are expected to be installed by spring 2025.
RWE said that this follows the installation of the high-voltage direct current (HVDC) export cable, which started last year.
The company has talked up the significance of the latest steps taken at the Sofia wind farm site.
“Sofia is RWE’s largest offshore wind construction project to date, and its furthest from shore,” stated RWE Offshore Wind CEO Sven Utermohlen. “Installing the first monopile is a highly symbolic moment in the construction of every offshore wind farm.”
Sofia will have a capacity of 1.4GW and will use 14MW Siemens Gamesa (SG 14-222 DD) turbines, which RWE described as the most advanced offshore wind turbine technology available. It is due to enter service by the end of 2026.
RWE also noted that of 44 of the wind farm’s 100 turbines would be equipped with recyclable blades.
Dogger Bank wind expansion
This comes amid broader advances to build out offshore wind capacity, both by RWE and other players.
The Sofia wind farm was originally known as the Dogger Bank Teesside B project, and received planning consent in 2015 along with three other project areas within the Dogger Bank Zone. Since then, the projects’ ownership has undergone changes, with RWE taking full ownership of Dogger Bank Teesside B, which was subsequently renamed Sofia, while withdrawing from the other three projects.
The other projects collectively became the Dogger Bank Wind Farm and are now being progressed by Equinor, SSE and Vargronn. On May 14, the partners announced that the installation of monopile foundations and transition pieces for the Dogger Bank B phase of the project had begun.
This came after Seaway7 recently completed the installation of all 95 transition pieces on Dogger Bank A.
Elsewhere in the Dogger Bank area, meanwhile, RWE is also taking steps forward on its early-stage Dogger Bank South (DBS) offshore wind farm projects, which it is developing jointly with Masdar.
On May 16, RWE and Masdar announced that they had contracted data acquisition firm Ocean Infinity for 3D ultra-high resolution seismic geophysical surveys at DBS West. Ocean Infinity has been tasked with surveying the subsea terrain at each of the proposed wind turbine foundation sites for DBS West, with the work due to start in June.
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