First Monopile Installed at Denmark’s Largest Offshore Wind Farm

April 30, 2025, by Adnan Memija

Jan De Nul’s heavy-lift vessel Les Alizés has installed the first of 72 monopiles at RWE’s 1.1 GW Thor offshore wind farm in the Danish North Sea.

The monopiles were shipped from the heavy-lift terminal in Eemshaven, the Netherlands, to the Thor construction site located approximately 22 kilometres off the west coast of Jutland.

In 2023, RWE selected Dajin Offshore and EEW SPC to supply 36 TP-less monopiles each, together with secondary structures, for the 72-turbine project in Denmark.

The monopiles are around 100 metres in length and weigh up to 1,500 tonnes each.

The units are being installed by Jan De Nul’s vessel Les Alizés under a contract signed with the developer in June 2023. Five monopiles can be loaded in one shipment.

“This is yet another big step in building the energy transition, and we execute multiple scopes of work: from installing inter-array and export cables, over scour protection to monopile foundations. For the diverse areas of expertise, we are deploying several units out of our fleet of vessels,” said Philippe Hutse, CEO Offshore Energy at Jan De Nul.

Innovative reused hard covers will be installed to protect the monopiles from harsh conditions at sea until the turbine towers are mounted.

Secondary steel structures for the foundations are being handled from the Danish Port of Thyborøn, which is the offshore construction base for Thor and home port for the project’s service vessels. The control centre for managing marine logistics and traffic throughout the offshore construction phase is also located in the port.

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Thor, Denmark’s largest offshore wind farm to date, will feature 72 Siemens Gamesa’s SG 14-236 DD turbines that will be installed using a jack-up vessel from Fred. Olsen Windcarrier. Of the 72 turbines, 40 will feature recyclable rotor blades.

The turbine installation works are scheduled to be carried out from the Port of Esbjerg, Denmark, starting in 2026.

Once complete in 2027, Thor is expected to produce enough renewable energy to supply the equivalent of more than one million Danish households.