Vattenfall has awarded Siemens Energy with an order for 72 model SWT-4.0-130 wind turbines for its new Sandbank offshore wind farm. The project is being erected 90 km to the west of the island of Sylt, in waters with depths of between 25 and 37 m, within the exclusive economic zone off the German North Sea coast. The project will feature a pioneering service plan in conjunction with its closest neighbour, the DanTysk wind farm that will result in synergies and cost reductions through the implementation of joint operations. Vattenfall have contracted Siemens to carry out the maintenance services of the Sandbank facilities over an initial period of five years.
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The maintenance operations will take place using a Service Operations Vessel (SOV) especially designed and manufactured for these projects. In the next phase of the project this vessel, that has been especially fitted out with accommodation for the technicians and an on-board workshop equipped with spare parts, will be based at a halfway point between the two wind farms. A helicopter will provide additional support enabling the transportation of the entire team to the mainland as well as to and from the wind turbines. The DanTysk wind farm, that is already in a more advanced phase of construction and is similarly equipped with Siemens G4 platform wind turbines, is situated a mere 20 kilometres away. The permanent availability of the SOV for its deployment and use at both wind farms will result in highly efficient maintenance operations thanks to the short distance between them and their high level of accessibility.
The wind turbines themselves will also make a considerable contribution to increasing effectiveness and reducing costs at the Sandbank project. The SWT-4.0-130 wind turbine model ordered for the project represents the latest generation in Siemens G4 platform wind turbines. These combine the most innovative technology of the wind turbines manufactured for onshore wind farms (over 900 units worldwide in operation, producing an average of 3.6 MW) with a significantly enhanced output of 4 MW at comparable maintenance costs.
Indeed the rotor with its 130-m diameter produces optimum energy even at low and moderate wind speeds. The advanced rotor blades also contribute to efficiency: the 63-m long aeroelastic blades have been designed to withstand high wind loads thanks to their flexibility and as such, they have been manufactured to have 20% less mass than conventional blades. Once the project has been commissioned at the end of 2016, the Sandbank wind farm will rank among the most modern offshore wind farms in the world. Construction is scheduled to start in summer 2015.