Under the direction of Seaway Heavy Lifting, one of the world's largest convertor platforms – a “power socket at sea” – has been installed to the west of Sylt, the East Frisian Island.
Siemens built the SylWin alpha platform. It is so large and heavy that the float-over method had to be used to lift it from a pontoon onto the already installed jacket. It was the first time this approach was used in the North Sea for a platform this large.
On Site Ballasting
The 14,000 mt SylWin alpha platform was transported on a pontoon that was positioned in between the jacket legs. The platform was installed onto the jacket’s legs by ballasting the pontoon. Then jacks were used to lift the platform into its final position on the jacket. A feat that was realised with the help of Dockwise and Mammoet.
Earlier this year, Seaway Heavy Lifting used its crane vessel Oleg Strashnov to install the jacket. In spite of the Oleg Strashnov being considered one of the world's strongest crane vessels, it was not strong enough to lift the SylWin alpha jacket.
Therefore, the decision was made to add additional buoyancy in the form of buoyancy tanks and to ballast the pontoon on site. This complicated operation has been preceded by more than a year of preparatory work.
SylWin Alpha
The 83-metre long, 56-metre wide and 26-metre SylWin alpha converter platform will serve as a power socket for the DanTysk, Sandbank and Butendiek wind farms, which together comprise 240 wind turbines and represent a generating capacity of 864 MW. Grid manager TenneT is responsible for the connection of the wind farms to, in this case, the German high voltage grid.
The SylWin alpha platform transforms the alternating current generated by the wind turbines into direct current that is transported via a 160-km long seabed cable and a 45-km long underground cable to the onshore Büttel high-voltage station.
Ever More Offshore Wind Farms
Northern Europe already has forty offshore wind farms in operation, another forty will be installed in the coming ten years. TenneT is installing the offshore electricity grid in the German and Dutch sectors of the North Sea to which the wind farms will be connected. Dutch offshore companies play an important role in installing the wind farms and the electricity grid.
