Siemens Installs Two Test Wind Turbines With Direct Drive Technology

Tag : Synchronous Generator

Erlangen, Germany - Siemens Energy recently announced that it willtest two 3.6-megawatt (MW) wind turbines with direct drive (DD)technology at a site in west Denmark. The first test turbine was tobe erected immediately, with the second to follow later in 2008.Siemens will subject the two DD wind turbines to comprehensivetesting for a minimum of two years. The purpose of this project isto assess whether direct drive technology is competitive withgeared machines for large turbines. Beside testing DD technology,Siemens will continue product development of turbines withgearboxes, and new turbines featuring geared technology will bereleased in the upcoming years. Wind power business is one of themajor contributors to the Siemens environmental portfolio. Infiscal 2007, the company generated revenue totaling some EUR17billion from products and solutions for environmental and climateprotection.
The main advantage of direct drive wind turbines is their smart,straightforward design that makes the use of gearboxes dispensable.With fewer moving parts DD technology has the potential to reducemaintenance costs, which could result in higher turbineavailability. However, DD machines are typically known to beheavier and more expensive in manufacturing than geared windturbines. One of the main objectives of the Siemens DD project isto establish if and for which turbine sizes direct drive machinesare competitive with geared turbines. A special focus will be onoffshore applications, where wind turbines need to be especiallyrobust and reliable.
Siemens will equip the two DD test wind turbines with synchronousgenerators excited by permanent magnets. The test generators willbe supplied by two different companies: One was developed by theSiemens Industry Sector and the other by Converteam. "By selectingtwo manufacturers we will be able to compare and access thebenefits of different technical solutions with respect to generatordesign," said Henrik Stiesdal, CTO of the Siemens Wind PowerBusiness Unit. "At a nominal torque in the range of 2500 kNm thetwo generators are among the largest permanent magnet machines everbuilt anywhere in the world."
Prior to installation of the direct drive test turbines, the twogenerators will be thoroughly tested on a test bed specially builtfor this purpose. Inside the test bed the generators can operate upto and above nominal power and speed. The tests on the firstgenerator have confirmed all theoretical assumptions made in theconceptual studies; testing of the second generator has been inprogress since June.
With a rotor diameter of 107 meters and a power rating of 3.6 MW,the two test turbines are similar in design to the standard SiemensSWT-3.6-107 offshore machine. By selecting a proven technologicalbasis for the test machines, Siemens will be able to use standardrotor blades, standard towers and many standard components from the3.6-MW series-produced machine. However, Siemens does not intend touse the configuration of the DD test turbines for future seriesproduction.
"Direct drive wind turbines are an exciting technological option,but at this stage we cannot yet state whether they will prove to bea competitive alternative to geared turbines," said Stiesdal. "Butwith the installation of two DD test turbines Siemens is laying thefoundation for such a judgment and is once more demonstrating itsrole as the front-runner in the development of innovativetechnology." Beside testing direct drive wind turbines, Siemenswill continue to develop its proven turbine technology. Forexample, a new 2.3-MW machine with a 101-meter rotor diameter forsites with low or medium wind speeds is currently at the prototypestage.
SOURCE: Siemens Energy