RWE to Deploy Collared Monopiles at Kaskasi Offshore Wind Farm

German energy company RWE will introduce the so-called ‘collared monopiles’ on the Kaskasi offshore wind farm in the German North Sea.

Designed based on an RWE patent, the collars will be installed around three monopile foundations at seabed level.

According to RWE, the new foundation technology will provide additional support for lateral loading, increase the bearing capacity, and improve the structural integrity of the entire foundation, especially in difficult ground.

“The collared monopile, a patented solution developed in-house, will help to increase stability in difficult ground. Furthermore, Kaskasi will be the first commercial offshore wind farm in the world to use an improved installation method to drive all monopile foundations to target penetration,” Sven Utermöhlen, Chief Operating Officer Wind Offshore Global at RWE Renewables, said.

”The vibro pile driving technique will reduce both installation time as well as noise emissions for marine life. This showcases our technical expertise as the second biggest player in offshore wind globally and means that we will continue to be at the forefront of the evolution of technology in this industry.”

RWE Renewables has signed a contract with DEME Offshore for the transport and installation of the new foundation technology at the 342 MW Kaskasi wind farm.

Bas Nekeman, Business Unit Director Northern Europe at DEME Offshore, said: “The Kaskasi collar installation project is a good example of how we can bring added value to our clients. Our versatile fleet of offshore installation vessels enables us to deploy the ideal vessel for this project and, in close collaboration with our client, we are tailoring the installation techniques and minimising any potential risks.”

The Kaskasi offshore wind farm will consist of a total of 38 wind turbines, with each turbine having a capacity of up to 9 MW, installed at the site some 35 kilometres north of the island of Heligoland.

The installation of the foundations will start in the third quarter of 2021 using the vibro pile-driving method. Kaskasi will be the first commercial offshore wind farm in the world using the vibro driving technique to install all monopile foundations to target penetration, RWE said.

The Team

The detailed design of the foundation collars was developed by the German civil engineering company JBO based on the RWE patent. Bladt Industries was selected as the manufacturer of the collars. Bladt will also manufacture and deliver the wind farm’s foundations.

DEME Offshore will transport the three collars from the manufacturer’s load-out port in Aalborg, Denmark, to the Kaskasi construction site near Heligoland.

Then the DEME Offshore team will install the steel collars around three of the 38 monopile foundations for which DEME will deploy the jack-up vessel Neptune.

The collar will be installed at seabed level in water depths of up to 25 metres. The space between the collar and the monopile foundation will be filled with grout material to create a stable connection. RWE will carry out accompanying tests to verify that the collar improves the structural behaviour in comparison to standard monopiles.

The Kaskasi wind farm is expected to start commercial operations in the summer of 2022.