Dutch player Heerema Marine Contractors has won a deal to transport and install the high-voltage direct-current (HVDC) offshore platform for RWE Renewables’ Sofia offshore wind farm in the UK.


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Located on the Dogger Bank, 195 kilometres offshore, Sofia spans an area of 593 square kilometres. The 1.4 gigawatt capacity project will be one of the largest offshore wind farms in the world when completed.

Monday’s announced deal for Heerema was struck with Singaporean fabricator Sembcorp Marine (Sembmarine), which, along with GE Renewable Energy’s Grid Solutions, recently scooped a contract worth around £600 million ($826 million) for the platform.

Heerema said installation is set for 2024 and it will used its heavy-lift semi-submersible crane vessel Sleipner for the job.

A Heerema spokesperson said transportation will take about six to eight weeks, while installation is planned for the northern hemisphere spring/summer of 2024.

The spokesperson declined to revealed the value of the contract.

The vessel has previously executed work for the Hollandse Kust and Hornsea 2 offshore wind farms.

On the drawing board: the Sofia platform. Photo: Image HEEREMA MARINE CONTRACTORS

Sembmarine and GE last July began early design works for the project after being selected as the preferred supplier of the HVDC electrical transmission system that represents Sofia’s second-largest contract.

The workscope comprises the design, manufacture, installation, commissioning and maintenance of the offshore converter platform (OCP) and the onshore converter station, including all ancillary equipment.

Singapore-based contractor Sembmarine’s workscope includes the design, construction, installation and commissioning of the OCP. It has now subcontracted the installation to Heerema.

The OCP, at the heart of the wind farm, comprises a 17,000-tonne topsides and jacket foundation structure piled into the seabed.

Located 220 kilometres from the nearest landfall, it will be the most powerful and most remote OCP ever built.

Sembmarine will this year start construction of the OCP, with delivery and installation at the Sofia wind farm scheduled for 2023.

Powering up: the 1.4GW Sofia offshore wind project Photo: Image RWE RENEWABLES