Installation of largest transformer at sea – excellent example of Holland’s Glory
Dutch offshore companies ready for further growth of offshore wind energy.
Dutch offshore companies realise a unique operation in the North Sea. Under the direction of Seaway Heavy Lifting, one of the world’s largest convertor platforms – a ‘power socket at sea’ – is installed to the west of Sylt, the East Frisian Island. Siemens built the SylWin alpha platform.
It is so large and heavy that the ingenious ‘float-over method’ has been used to lift it from a pontoon onto the already installed ‘jacket’ (the base of the platform). This approach has been used successfully in the Gulf of Mexico and in the Far East, but is the first time that a platform as large as SylWin alpha was installed using the method in the North Sea.
Siemens commissioned Seaway Heavy Lifting (based in Zoetermeer, the Netherlands) to perform the unusual operation that in turned called in the assistance of maritime service providers Dockwise and Mammoet. The 14,000Mt SylWin alpha platform was transported on a pontoon that has been positioned in between the jacket legs. The platform was installed onto the legs of the jacket by ballasting the pontoon. Dockwise was responsible for this phase. Mammoet will then use jacks to lift the platform into its final position on the jacket.
The 83m long, 56m wide and 26m high SylWin alpha platform is the largest of its type. 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 is not strong enough to lift the SylWin alpha jacket. Therefore, the decision was taken 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.
The 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 megawatt. Grid manager TenneT, Siemens’ customer, 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 160km long seabed cable and a 45km long underground cable to the onshore Büttel high-voltage station.
As a contribution to sustainable energy provision, Northern Europe already has 40 offshore wind farms in operation, another 40 will be installed in the coming 10 years. TenneT, the grid manager, 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 are playing an important role in installing the wind farms and the electricity grid.
United we are strong
A large number of Dutch companies are involved in the installation of SylWin alpha led by the main contractor Seaway Heavy Lifting. In the summer of 2013, in collaboration with Marin, the research institute, extensive simulations of the most complex aspects of the installation were made. Mammoet was closely involved in the transportation of the jacket. Equipment supplied by Cape Holland, IHC Merwede and Franklin Offshore Europe was used during the installation of the jacket by Seaway’s crane vessel Oleg Strashnov. Boskalis supplied the majority of the required pontoons and tugboats; Dockwise is responsible for the float-over operation.
Jan Willem van der Graaf, CEO Seaway Heavy Lifting: “This is an excellent example of what the Dutch offshore industry has to offer the developing offshore wind sector. An additional four gigawatts of offshore wind capacity must have been realised in the Dutch sector of the North Sea by 2023. This means work to install wind farms and the associated electricity grid. Seaway Heavy Lifting and its partners are ready to contribute to this sustainable ambition. In Seaway Heavy Lifting’s head office in Zoetermeer, 270 engineers and staff are doing the preparations for these projects. There is also sufficient opportunity for people who are looking for work to contribute to such projects at Seaway Heavy Lifting in the coming years.”