One of the repercussions of Fuhrländer’s insolvency is a delay to the installation of its 3MW FL3000 prototype turbine, originally planned for the end of the year. If it comes to fruition, the FL3000 is designed for low-to-medium wind conditions (IEC class IIA), and will represent a new generation of 3MW volume medium-speed geared wind turbines.
The Fuhrländer turbine features a 120.6-metre rotor diameter and incorporates the patented Larus Compact drive system from engineering consultancy W2E Wind to Energy. This Larus Compact drive is also applied in the proven 2.5MW high-speed FL2500 model, but the new addition is an interesting combination of the Larus with Winergy’s HybridDrive.
Larus Compact drive technology comprises a single rotor bearing and a large-diameter shaft coupling that transmits rotor torque only to the flanged gearbox via an annular array of flexible elastomer elements. Rotor bending moments, by contrast, are led directly through the rotor bearing via the machine’s main carrier into the tower. This prevents harmful loads from entering into the gearbox.
HybridDrive is a semi-integrated medium-speed design solution incorporating a two-stage planetary gearbox and a permanent magnet generator. Winergy’s product development focus was on overall compact design. A flange connection between gearbox and generator enables easy individual component exchange while eliminating the need for an intermediate connecting shaft.
"System integration enables drivetrain length to be shortened by about 35-45% compared to a conventional non-integrated geared drive system of similar power rating," said Matthias Deicke, Winergy’s head of electrical systems.
Another focus of the design was to boost operational efficiency under both partial- and peak-load conditions. During a bench testing campaign earlier this year, peak load efficiency of the total system (generator and gearbox) measured over 96%, said Deicke. This ranks among the best values of all existing drivetrain technologies, he added.
HybridDrive has a smaller-sized generator and requires only about 20% of the rare earth element quantity compared to direct-drive systems with similar power rating.
Development of the FL3000 technology was a joint effort between German companies Winergy, Fuhrländer and W2E. Fuhrländer acquired 51% of W2E’s share capital in early 2012, but these firms have already co-operated closely for a decade. W2E will operate its own experimental FL3000 wind turbine in Kankel near Rostock, for which a building permission has been given.
W2E's version of Fuhrländer’s 2.5MW FL 2500 turbine model is characterised by a flanged three-stage gearbox and a non-integrated doubly-fed induction generator. Another FL3000 project partner is the mechanical/dynamics department of Germany’s Rostock University, responsible for specific subtasks in the area of multi-body simulation. The German environment ministry provided financial support due to the innovative nature of the project.
The HybridDrive’s compact dimensions can potentially provide several other design-related benefits. New turbine designs like the FL3000 enable a substantially shortened nacelle with reduced weight. This nacelle mass reduction can positively affect tower and foundation mass, as well as costs. Alternatively, designers can opt to move the power electronic converter and transformer into the nacelle instead of the tower foot.
HybridDrive can be combined with either a single rotor bearing or an alternative solution with a main shaft and two bearings. HybridDrive planetary gears can be offered with common roller bearings or journal bearings. The latter combine compact dimensions with high load carrying capacity and a built-in capability to absorb peak loads while offering a long service life.