RWE has successfully installed the first monopile at its 760MW OranjeWind offshore project in the Dutch North Sea.
This marks a significant milestone for the project, which is a joint venture of RWE and TotalEnergies. Installation of all 53 monopiles is due to be completed by early 2027.
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Sven Utermöhlen, CEO RWE Offshore Wind, commented: “RWE and TotalEnergies are delivering one of the largest wind farms in the Dutch North Sea. After years of planning, the project has become a reality with the installation of the first monopile. This is a huge success for the team and its supply chain partners.”
The foundations are monopiles without transition pieces. This means the turbines are bolted directly to the monopile’s top flange, without needing a transition section. This design significantly reduces the amount of steel used. Secondary steel components such as the Main Access Platform, Internal Cassette and boat landings are mounted directly onto the monopile in a separate installation campaign. Each monopile will be around 90m long and 8m in diameter.
The monopile was loaded at Sif’s terminal at the Maasvlakte near Rotterdam. It was transported to and installed at the site off the coast of Ijmuiden by Jan De Nul’s vessel the Les Alizés, part of a long-term charter between Jan De Nul and RWE.
The Les Alizés is an innovative floating vessel that uses dynamic positioning to ensure correct placement of the monopiles. It uses a 5,000t crane that reaches 160m at full height to lift the monopiles so they can be driven into the seabed by a hydraulic impact hammer. The Les Alizés is an ultra-low emissions vessel, a notation for ships that go beyond existing MARPOL requirements for lowering emissions. It is equipped with systems that significantly reduce nitrogen oxide and fine particle emissions.
To protect marine life from the sound impact of piling, the project is applying a so-called bubble curtain, where compressed air is pumped through a hose to create a wall of bubbles around the piling site, which absorb and reflect sound-waves. The project will also conduct noise measurements outside the bubble curtain to verify and ensure that sound levels remain within the applicable limits.
