Allseas BorWin4 DolWin4

Allseas to Install DolWin4 & BorWin4 HVDC Offshore Platforms

Dragados Offshore has selected Allseas to install the high voltage direct current (HVDC) converter platforms for the DolWin4 and BorWin4 offshore grid connection projects in the German North Sea.


Under the contract, the company will be responsible for the transportation and single-lift installation of two 900 MW converter stations for the transmission of wind-generated power.

The offshore grid connection projects will transmit together a power of 1.8 GW which will be enough to meet the power demands of a major city like Hamburg, Allseas said.

Both the DolWin4 and BorWin4 platforms will be built in Cadiz, Spain, and transported by Allseas cargo barge Iron Lady to Rotterdam for transfer to the installation vessel Pioneering Spirit.

The structures comprise topsides weighing approximately 12,500 tonnes, supported by 7,000-tonne (DolWin4) and 8,000-tonne (BorWin4) jackets.

Installation is scheduled for 2027.

“These are substantial structures, ideally suited to our unique transport and single-lift installation capabilities. We showed what we are capable of with DolWin6 last year and the market has taken notice. As the size of converter stations increases, so does the argument for our significantly safer, faster, and more efficient single-lift solution”, said Matthijs Groenewegen, Allseas Vice President Projects.

DolWin4 and BorWin4 are the first offshore grid connection systems to be developed by German transmission system operator Amprion Offshore GmbH, said Allseas.

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Dragados Offshore is responsible for delivering the two platforms, with partner Siemens Energy providing the HVDC technology.

Prysmian is responsible for the design, supply, installation, and commissioning of land and submarine cables for the DolWin4 and BorWin4 offshore wind farm connection systems.

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The two connections will be installed in parallel and are scheduled to begin operating in 2028. BorWin4 would thus even be connected to the grid one year earlier than originally planned.

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