Alstom and Converteam are collaborating on the world’s largest direct drive permanent magnet generator (PMG) for a wind turbine.
As a first step Converteam will equip Alstom’s two 6 MW offshore wind turbine prototypes that will be installed onshore and offshore in Europe during winter 2011 and in 2012.
Alstom’s next generation 6 MW turbine design aims bring down the cost of energy (COE) of offshore wind. These include an arrangement featuring Alstom Pure Torque technology and Converteam’s direct drive PMG that will together ensure greater reliability of the turbine’s drive train.
Alstom Pure Torque protects and improves generator performance by diverting unwanted stresses from the wind safely to the turbine’s tower. Only turning force, or torque, is transmitted to the generator, which ensures sufficient air gap is maintained between the generator rotor and stator, thereby boosting its performance and reliability.
“Direct drive” systems have no mechanical gearbox coupled to the generator. Their low number of rotating parts increases reliability, to maximise turbine availability and reduce maintenance costs.
The use of a “permanent magnet” generator leads to better generation efficiencies and even greater overall mechanical reliability, which is critical in offshore wind where reliability is fundamental.
Converteam will supply Alstom with its “Advanced High Density” (AHD) direct drive PMG, which is a more compact and lightweight design compared to earlier generation direct drive systems.
Alfonso Faubel, Alstom Power’s Wind business vice president, said: “We’re developing a robust, simple and efficient turbine that will lower the COE of offshore wind power. There can be no design compromises on a power-generating product that will operate in the industry’s most challenging environmental conditions.”
Converteam delivered their first permanent magnet generators for 5 MW wind turbines in 2004, and their first high power (rated 3.7 MW) direct drive PMG has been in operation since 2008.
Pierre Bastid, CEO of Converteam, said: “The generator will have the largest torque of any Permanent Magnet Generator built to date, and with this project, we are making a big step in commercialising very large direct drive wind generators. Alstom’s turbine will be one of the largest direct drive wind turbines in the wind offshore market, and the largest to feature a Direct Drive Permanent Magnet Generator.”
Alstom’s turbine has been developed for the wind conditions encountered in most offshore locations in Europe, the US and the rest of the world. Two prototypes will be installed in 2011 and 2012, a pre-series in 2013 (the final rollout step before full commercialisation), and series production in 2014.
Other key features of the turbine include its very large rotor diameter – using the world’s longest turbine blades jointly developed with LM Wind Power – and 6 MW power output for higher energy output.
High yield helps offset wind farm investment and operating costs. The turbine’s weight has also been optimised to reduce installation and infrastructure costs.
[Image copyright 2011 Converteam]