Heerema Marine Contractors has installed the first out of 27 Vestas V174 9.5-MW turbines at the Arcadis Ost 1 wind farm. Semi-submersible crane vessel (SSCV) Thialf installed the turbine using the RNA method, a unique floating installation method, for the first time.

The plan to use a floating installation method for Arcadis Ost 1 was announced for the first time in November 2019. On 24 November, after almost three years of development and engineering, Heerema has successfully executed the floating installation of the first Arcadis Ost 1 turbine.

The innovative method has two main advantages. The first is zero seabed interaction, especially important in areas of significant water depth or challenging soil conditions. The second advantage is a shorter installation cycle.

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Assembly and lifting in parallel

To speed up the installation process, assembly and lifting operations are happening in parallel. One of the Thialf’s two main cranes lifts the pre-assembled wind turbine generator (WTG) tower to the foundation, whilst the second main crane is used to pre-assemble the WTG in parallel.

For the latter, Heerema developed a method where the Rotor Nacelle Assembly (RNA) lift takes place on a so-called “support” tower on board of the crane vessel. The support tower provides a stable platform to allow a fast and secure assembly of the nacelle and blades. Once pre-assembled, the complete RNA is lifted as one piece onto the WTG tower in only one lift.

The pre-assembly process on board the Thialf ensures full control thereby guaranteeing a safe and highly reliable installation environment. The reduced number of lifts between the vessel and the structure eliminates key risks of the floating installation. Vestas has delivered RNA lift-feasible components by developing new tools to support the offshore floating installation.

‘This first installation is the result of extensive engineering, innovation, and the dedication of our team, alongside Parkwind and Vestas, who together have worked hard to deliver the first floating installation of a wind turbine generator using our novel RNA method,’ says Michel Hendriks, chief operating officer of Heerema Marine Contractors. ‘This moment is also a major milestone within the offshore wind industry, and Heerema will continue to develop and enhance our capabilities for the floating installation of offshore wind farms.’

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Arcadis Ost 1

The Arcadis Ost 1 is a 257 MW wind farm developed by Parkwind, located in the German territorial waters of the Baltic Sea, northeast of the island of Rügen and will generate enough green energy to power the equivalent of up to 290,000 households. It is Europe’s first wind farm equipped with Vestas’ V174-9.5-MW turbines and Parkwind’s first international project. The installation campaign started in June 2022 and the wind farm’s final commissioning is planned in 2023.

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