Direct-drive wind turbines combine robust engineering with a low system weight. This not only reduces infrastructure, installation, and maintenance costs but also increases energy yields and profitability over the full service life of a wind plant.
Now, a six-megawatt (MW) direct-drive wind turbine for use in offshore wind farms has been recently launched. The rotor blades of the Siemens SWT-6.0 are 75 metres in length – longer than for any other 6 MW wind turbine. Based on Siemens’ Quantum Blade technology, the blades are also shaped to deliver maximum performance at a range of wind speeds.
With a combined weight of around 350 metric tons for the nacelle and rotor blades, the SWT-6.0 wind turbine is the lightest system in its class. This cuts costs not only for transport to the site but also for the foundations and tower. Direct-drive wind turbines are reliable, energy-efficient, and extremely robust. At the same time, they feature fewer individual components and require less-frequent maintenance than comparable systems. This not only increases the hours of operation and the power yield but also makes the technology attractive for offshore installations.
The nacelle of the SWT-6.0 has been designed for easy servicing, even in offshore conditions, and features a special platform to which engineers can be winched down from a helicopter. Inside, there is plenty of room to work and good access to all the important components, particularly the direct-drive generator, which boasts a very high efficiency thanks to the use of permanent magnets.
Since May 2011, this wind turbine has been operating without problems in a field trial in Denmark. Over the next two years, Siemens will install a pilot series of up to 50 plants in Germany, Denmark, the Netherlands, and the UK.
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