A first for Jan De Nul
Gode Wind 3, Germany
Whether it’s about constructing wind turbines at sea, installing a bridge across a river, or the remediation of a polluted site: large projects only succeed when you pay attention to the smallest details. Even in supersized structures, the margins are narrow, with less than a centimetre to spare.
Let’s take a closer look at the installation of the offshore substation for the Gode Wind 3 offshore wind farm in Germany. A first for Jan De Nul to install an offshore substation, and a first for our newest crane vessel Les Alizés on her maiden assignment.
A heavy challenge
Our next-gen crane vessel Les Alizés successfully installed the heaviest load of the project: a 1,900-tonnes offshore substation topside with connecting modular support frame.
After the project kicked-off in July with the installation of the first 6 monopiles for Gode Wind 3, the crane vessel installed her very first offshore substation. The load was lifted and meticulously placed on top of its foundation.
Extra challenging: the installation needed to be done in floating conditions. The crane vessel Les Alizés is fitted with a powerful dynamic positioning system (DP2), keeping the vessel in position at all times. The barge which carried the offshore substation and modular support frame, moored alongside Les Alizés. The vessel’s main crane picked up its load in floating conditions, a challenge where coordination, precision and weather conditions were key.
The offshore substation
The Gode Wind 3 offshore substation stands as tall as a 5-storey building and gathers the produced electricity of 23 Gode Wind 3 turbines of 11MW each. The substation converts the 66kV AC to 155kV AC and sends the electricity through a subsea HVAC export cable to the DolWin Kappa convertor station.
DC transmission is needed to transport large volumes of electricity over long distances. From a certain amount of power (MW) and a certain distance (approx. 100 km) the losses in a HVAC system become too big. In such cases conversion to DC is a more economical solution compared to high-voltage AC.
The modular support frame
Made in France
Chantier de l’Atlantique in Saint-Nazaire, France, fabricated the 1,900 tonnes offshore substation and a 350 tonnes modular support frame. Because of the size and weight of both components, the transport overseas needed to be prepared meticulously. The size of the barge, the power of the tugboat, the exact position of both components on board, the sea fastening, the position of the rigging tools... everything was prepared down to the last detail, as no manipulation was possible once the barge had left the yard
Ørsted projects
The installation of this offshore substation is part of the bigger project Gode Wind 3 offshore wind farm of Ørsted. The construction of this 242 MW offshore wind farm is taking place in parallel with the company’s 900 MW Borkum Riffgrund 3 project. Les Alizés is contracted to install all 107 monopile foundations needed for both wind farms, including this offshore substation and connecting modular support frame.
Paolo De Temmerman, Works Manager
