Siemens Energy has installed the first prototype of a newly designed direct-drive wind turbine.

The new SWT-3.0-101 DD is a gearless machine with a power rating of 3 MW. It has a rotor diameter of 101 m (331 ft). The prototype was installed close to the Danish town of Brande, where Siemens Wind Power headquarters is located.

Direct-drive wind turbines offer a smart, straightforward design that makes the use of gearboxes dispensable. Siemens will thoroughly test and validate the performance of the SWT-3.0-101 before the new product will be officially launched for sale in 2010.

“Compared to a standard wind turbine with gearboxes, we managed to reduce the number of parts in the new SWT-3.0-101 DD by half,” said Henrik Stiesdal, CTO of the Siemens Wind Power Business Unit. “With fewer moving parts, the direct-drive technology has the potential to significantly reduce maintenance time, which could result in even higher turbine availability.”

The new SWT-3.0-101 DD, which primarily will be targeted for high-end onshore markets, features a compact synchronous generator excited by permanent magnets. The generator was produced by the Large Drives Business Unit within the Siemens Industry Sector. The main advantage of permanent magnet generators is their simple and robust design that requires no excitation power, slip rings or excitation control systems. This leads to high efficiency even at low loads.

“One and a half years after starting the testing of two direct-drive concept wind turbines, we are now confident that this technology is a sound base for future Siemens wind turbines,” said Stiesdal. In July 2008, Siemens installed the first of two 3.6-MW direct-drive-concept turbines. The purpose was to assess whether direct-drive technology is competitive with geared machines.

“We can now conclude that the concept machines are operating with an excellent performance and that we are ready to move ahead with developing the concept into a commercially competitive product,” said Stiesdal.

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