This Week: Product Pick - The M5000 - A 5-MW hybrid-drive offshore wind turbine

Already experienced in renewable power generation, France-based Areva purchased the start-up German company Multibrid in 2007, particularly for its 5-MW hybrid-drive offshore wind turbine, the M5000. Now, Areva’s model is on the market as the first turbine designed just for large-scale offshore wind farms.

The M5000 is well suited for offshore use because it is powerful, yet relatively compact and lightweight. The nacelle and rotor combined weigh only about 349 tons. This makes the turbine easier to transport and erect, crucial when working on the open sea. The nacelle is fully assembled on land by the Areva technicians, to allow lifting it onto the tower as a complete unit. This trims time and cost, while increasing safety. More so, the company says the nacelle’s reduced weight permits a cost-effective tower and foundation. The components’ compact placement in the nacelle stems from studies of conventional turbines.

The M5000’s hybrid-drive design consists of a one-stage planetary gearbox and a permanent magnet synchronous generator. By integrating the rotor bearing, gearbox, ad generator, the turbines design eliminates the need for component housing. Small dimensions also create short paths for load transmission to the tower head ideal for offshore projects. With this robust construction, the M5000 achieved the stronger wind rating Class I Type certificate (IEC1b) by the International Electrotechnical Commission.

The turbine’s low rotational speed along with a small number of rotating pats and roller bearings minimize the risk of drive train damage. In addition, all key subsystems and sensors are installed in duplicate, so their failure doesn’t result in a shutdown. Condition monitoring keeps tabs on components’ and report irregularities, which makes maintenance work easier to schedule and more efficient.

In fact, two online condition-monitoring systems ensure reliable, safe operation. Engineers applied online monitoring of the drive train from rotor bearing, to gearbox, to the turbine’s speed. Additionally, a monitor detects rotor and blade status to allow proper maintenance. The control system, called Multivis, allows monitoring component condition and parameters such as temperatures, flow, and switching rate.

Protecting turbine equipment from corrosion is vital to its service life, especially offshore. To that end, the M5000 has an air-treatment system that filters corrosive elements from outside air. This creates and overpressure of purified air within the entire system, thus protecting it from external corrosive influences such as salt and moisture.

The turbine’s components are shipped to Areva’s manufacturing facilities in the German coastal city of Bremerhaven. Here, they are assembled at a location ideal for transporting the turbines directly to offshore installations.

In 2009, Areva installed its first six M5000 turbines for the Alpha Ventus project-Germany’s premier offshore wind farm-and has agreed to provide 40 units for the project’s second phase. Subsequently, the turbine was chosen for Germany’s initial utility-scale offshore wind project, Global Tech 1, consisting of 80 units (400 MW). Through a syndicate of 11 banks, it’s the first offshore wind project in the country to achieve third party financing.

Areva recently signed TSA & SMA Agreements with Trianel GMbH (a consortium of German regional utilities and communities) for the Borkum West II project, and will provide 40 turbines (200 MW). Both projects will be installed in 2012-2013 and commissioning is scheduled for 2013. In total, Areva’s 5-MW wind turbines support an order backlog of 1,000 MW (1 GW) in offshore projects.

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