Heerema Develops Offshore Wind Construction Method Using Floating Vessel
Offshore wind farm Arcadis Ost 1 in Germany will be the first to make use of a floating vessel for the installation of wind turbine generators. This construction technology is the result of a year-long joint development between Parkwind, Heerema Marine Contractors and MHI Vestas Offshore Wind.
The announcement of the first floating wind turbine generator (WTG) installation, followed by the signing of a conditional agreement for turbine supply between Parkwind and MHI Vestas took place on 26 November during the Wind Europe conference in Copenhagen.
Arcadis Ost 1
Parkwind is developing the 257-megawatt Arcadis Ost 1 offshore wind farm. The project, located 20 kilometres northeast of the island of Rugen in the Baltic Sea, will consist of 27 MHI Vestas V174-9.5-megawatt turbines mounted on monopile foundations and one offshore substation. It is the first offshore wind farm to install the newly developed V174 turbines. Arcadis Ost 1 will supply green power to an estimated 300,000 German households.
Reducing Risk and Installation Time
Considering the challenging soil conditions at the Arcadis Ost 1 site, Parkwind looked at possible alternatives to traditional installation methodologies. In joint cooperation with Heerema Marine Contractors and MHI Vestas, the floating installation method was developed.
‘More than one year ago, Heerema Marine Contractors, together with our partners MHI Vestas and Parkwind, started an intensive research to find out the possibilities of installing turbines utilising our fleet of floating assets [Heerema’s fleet consists of heavy lift vessel Aegir and the three semi-submersible crane vessels Sleipnir, Balder and Thialf – ed.],’ says Koos-Jan van Brouwershaven, CEO of Heerema Marine Contractors. ‘In our Simulation Center, we created an authentic visualisation of the local situation, including crane and vessel controls, realistic weather conditions, sea swell patterns and seabed conditions. This collaboration led to an innovative method which will be used for the installation of turbines in the Arcadis Ost 1 wind park.’
This methodology offers two advantages; it avoids all interaction with the soil thereby reducing the project’s risk compared to a traditional jack-up installation and it allows for a reduced installation time and thus reduces cost.
Nacelle and Blade Assembly on Board
A floating installation vessel is used to assemble the WTG components. The vessel will have all turbine components on its deck including a dummy tower. This tower will provide a stable platform on board the vessel to assemble the nacelle and the blades.
The first step will be lifting the WTG tower onto the pre-installed turbine foundation. The second step is the most advanced element in the assembly process which includes lifting the nacelle onto the dummy tower and attaching the blades. This process ensures full control over the blades thereby guaranteeing a safe and highly reliable blade assembly. After the Rotor Nacelle Assembly (RNA) on the installation vessel, the complete RNA will be lifted as one piece onto the WTG tower.
Picture (top): Blade and nacelle assembly on dummy tower on board.