The first monopile and first transition piece have been installed at the Dogger Bank Wind Farm in the North Sea in the UK, marking a key milestone for the construction of the largest offshore wind farm in the world.

The foundations, designed by Wood Thilsted, are up to 72m long, weigh an average of 1,057 tonnes and include the world’s largest 8m offshore wind flange. The design features the world’s first bi-level transition piece for safe installation and operation, with installation work being carried out by Seaway 7 with support from DEME.

Paul Cooley, Director of Offshore Wind at SSE Renewables, one of the joint ventures (JVs) involved in Dogger Bank, said: “This is a very important milestone for the project as it marks the start of our campaign to install 277 turbine foundations. on the three phases of what will be the largest offshore wind farm in the world. »

Dogger Bank Wind Farm, a JV between SSE Renewables (40%), Equinor (40%) and Eni Plénitude (20%), is made up of three offshore wind farm sites more than 130 km off the northeast coast from England. When operational, the wind farm will generate 3.6 GW of energy.

SSE Renewables is the main operator for the development and construction of Dogger Bank, while Equinor will be the main operator of the wind farm when completed for its expected life of approximately 35 years.

“As prime operator during the construction phase of the Dogger Bank Wind Farm, we are working with our development and supply chain partners to install some of the largest turbine foundations in the world on this world-class project” , Cooley said.

“During this campaign, we are using foundations designed in the UK and with steel components made in the UK, all of which help support jobs in the UK and a just and fair transition to net zero. “

Steel made by Tata Steel in Wales and processed at Corby and Hartlepool is used in the transition piece support components, while South Tyneside-based Metec and Rochdale-based Granada Material Handling also won contracts with Smulders to support the project.

The foundations have been optimized to cope with the difficult wave loads in the Dogger Bank area of ​​the North Sea, with installation in water depths of up to 32m and at a distance of 130km from shore and provide a solid and stable foundation for the scale of the GE Renewable Energy’s Haliade-X turbines, which are expected to be installed on each of the turbine foundations starting in the spring of 2023. Each turbine has a power output of up to 14 MW.

lastair Muir Wood, CEO of Wood Thilsted, said: “Wood Thilsted is proud to contribute to the success of the Dogger Bank wind farm. Our team faced challenges including working with the largest turbine at the time, an innovative dynamic positioning installation vessel, and very large wave loads.

“What made the success possible was the collaborative working relationship shared with the Dogger Bank team and other key stakeholders. This project is a model of success for current and future projects.

The DEME offshore installation vessel DEME Innovation installs a monopile at the Dogger Bank wind farm off the coast of England. (Photo: DEME)

During the three-year installation program for the three phases of Dogger Bank, a total of 277 monopiles and transition pieces will be loaded onto installation vessels in Rotterdam before being transferred to the offshore wind farm site. Using dynamic positioning technology, the vessels will locate the installation site in the seabed, from which a monopile measuring up to 72m will be knocked down and transferred to a pile clamp, before being lowered in the seabed.

A hammer will be used to drive the monopile to the design depth in the seabed before a guidance system aligns the installation of the 8 meter record flanges, which serve as the connection for the transition piece which is then installed on the monopile. The foundations require 152 giant M80 bolts to secure them before a cover is inserted over the top of the transition piece to leave it watertight.

Seaway 7 has been awarded the Tier 1 contract to install the foundations on all three phases of the Dogger Bank Wind Farm, with sub-contractor DEME, also the project’s inter-grid cable installer, deploying its installation vessel offshore Innovation for the first foundations on Dogger Bank A. Later, the Seaway Strashnov will deploy on the Dogger Bank A to continue the installation of the foundations.

Lucien Romagnoli, Renewables Business Unit Manager at DEME Offshore, said: “These unique foundations are huge but also technically complex. This is an important moment for offshore wind and the energy transition.

In November 2020, the Sif and Smulders consortium won the contract to manufacture all 190 monopiles and transition pieces for the Dogger Bank A and B phases of the wind farm, with a contract for all 87 monopiles and transition pieces remainder of Dogger Bank C awarded to consortium in 2021.