Denmark: Siemens Tests 6MW Turbine with World’s Largest Rotor

On October 6th 2012, Siemens Energy has begun field testing of its new 154 m rotor for the 6-megawatt (MW) offshore wind turbine in Østerild, Denmark. The SWT-6.0-154 turbine is equipped with the world’s longest rotor blades – each blade is 75 meters in length. With a record rotor diameter of 154 meters, each SWT-6.0-154 turbine can produce 25 million kilowatt hours of clean electricity in offshore locations, enough to supply 6,000 households.

As early as May 2011, Siemens installed the first prototype of its new 6-MW turbine using a 120 m rotor. It has now been operating successfully for well over a year. The serial version of the 6-MW turbine will use the 154 m rotor and is expected to become the new benchmark in the offshore wind industry.

“The start of field testing of the 154 m rotor for the 6-MW is an exciting step in the development of competitive technologies for the large offshore wind farms of the future. We incorporated our technological expertise gained over more than three decades into the development of both the gearless turbine and its 75-meter rotor blade,” says Henrik Stiesdal, CTO of the Wind Power Division within the Siemens Energy Sector.

The gearless drive technology permits a compact design: Using Siemens` Direct Drive technology the SWT-6.0 is the lightest turbine in its class, having a nacelle weight of only 200 tons. This combination of robust design and low weight reduces offshore infrastructure, installation and maintenance costs. “At the same time, the turbine delivers an increased energy yield and offers greater profitability over its life cycle,” Stiesdal adds.

Siemens developed the SWT-6.0 specifically for demanding conditions in offshore locations. “The new 6-megawatt turbine is a milestone in wind energy technology,” says Stiesdal. “Compared to our first 30-kilowatt turbine, which we developed 30 years ago, the new STW-6.0-154 will produce over a thousand times more energy per year.”

The rotor blade development is equally impressive. The first blade of the 30-kilowatt turbine was five meters long, approximately the length of a minibus, while the new 75-meter rotor blades have a length corresponding to that of an Airbus 380 plane, the world’s largest aircraft.

The first Siemens 6-MW turbine was installed in May 2011 at the Høvsore test site in Denmark. Due to height restrictions a 120 m rotor was used on the prototype. It has now operated for well over a year, setting new production records during the testing. The record-breaking 154 m rotor is mounted on a 6-MW turbine installed at the new national test center at Østerild, Denmark, and formal release of the turbine took place at the inauguration of the test center on 6 October, 2012.

The B75 blade used in the new rotor is characterized by high stability and low weight. Special aerodynamic profiles deliver optimum performance at a wide range of wind speeds.

For the manufacturing of the B75 blade, Siemens uses the patented IntegralBlade® process, which permits rotor blades to be produced from a single casting without adhesive joints. An IntegralBlade® is up to 20 percent lighter than blades manufactured with traditional methods. Overall, combining an intelligent rotor blade profile with low weight helps lower the cost of wind energy.

The new SWT-6.0-154 is already a commercial success. In July 2012, Siemens entered into a Master Agreement with the Danish energy group, DONG Energy, for the delivery of 300 offshore turbines of this type. The wind turbines are expected to be used in projects off the coast of the U.K.

Siemens will soon install two more SWT-6.0 prototypes in the British offshore wind power plant, Gunfleet Sands. This will be the first time that the Siemens 6 MW wind turbine will be tested offshore. Both machines for this project will be equipped with the 120 m rotor.

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Press release, October 8, 2012; Image: Siemens