Collared Monopile Debuts on RWE’s Kaskasi Offshore Wind Farm

For the first time ever in the renewables industry, special collars were installed around the monopile foundation at the seabed level on RWE’s Kaskasi wind farm offshore Germany.


The ‘collared monopile’ is a design based on a RWE patent. The new technology is expected to provide additional support for lateral loading, increase the bearing capacity and improve the structural integrity of the entire foundation.

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”At our Kaskasi offshore wind farm we use innovative technologies that will set standards throughout the entire offshore industry,” Sven Utermöhlen, CEO Offshore Wind, RWE Renewables, said.

”It’s a great credit to the project team and our contractors that we developed, manufactured and safely installed the three innovative foundation collars. The collared monopile, a patented solution developed in-house, will help to increase stability in difficult ground. This showcases our technical expertise as the second largest player in offshore wind globally.”

The 342 MW Kaskasi is RWE’s sixth wind farm off the German coast. The project is currently under construction 35 kilometres north of the island of Heligoland.

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In total three innovative foundation collars were successfully embedded into the seabed – each seven metres high, weighing 170 tons.

The installation in water depths of up to 25 metres was carried out by the jack-up vessel Sea Challenger from DEME Offshore.

The space between the collar and the monopile foundation was filled with grout material, creating a stable connection.

RWE will carry out accompanying tests to verify that the collar improves the structural behaviour in comparison with standard monopiles.

The detailed design of the collars was developed by the German civil engineering company JBO based on the RWE patent, Bladt Industries was selected as the manufacturer, and DEME Offshore was responsible for the transportation and installation.

”Whilst these monopile foundation collars represent only a relatively small scope of work
DEME Offshore is performing at the Kaskasi offshore wind farm, we are extremely happy achieving this important milestone for the project,”
Bas Nekeman, Business Unit Director Northern Europe at DEME Offshore, said.

”The installation of these type of structures is a world’s first which required us to develop a tailor-made solution. The completion of the three monopile foundation collars demonstrates our ability to deliver our customers the right technical know-how, operational excellence and team spirit required for the successful delivery of these types of innovative projects.”

Apart from the collared monopile, further innovations introduced at Kaskasi are the vibro pile driving technology and the ‘Self-Expanding Pile Shoe’, a new foundation solution with a concrete ring that expands in the seabed, and Siemens Gamesa’s recyclable rotor blades.

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The blades are the first of their kind, thanks to an innovative resin that enables components to be recycled for new applications at the end of their lifecycle.

The installation of the wind turbines is scheduled to start this summer. By the end of 2022, a total of 38 wind turbines are to be fully operational. Then, the Kaskasi offshore wind farm will have the capacity to supply the equivalent of approximately 400,000 households with green electricity every year.

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