Winergy’s HYBRIDDRIVE Gearbox and Generator Combo

Winergy is a German company long known for its quality and innovation in gearboxes and drive systems for wind turbines.

At the American Wind Energy Association (AWEA) Windpower Conference and Expo last month, Winergy introduced its new 3 MW HYBRIDDRIVE technology, which combines a 2-stage gearbox and a permanent magnet generator into one product (Winergy press release).

According to Winergy’s press release, the new design provides the advantages of reduced size and weight of the nacelle and drive train:

The direct linkage of the two stage gearbox and the permanent-magnet driven generator shortens the drive train by approximately 35%. This design allows for a significant reduction of the nacelle size and minimization of the overall weight.

Winergy found the inspiration for its new gearbox and generator combo from work performed by Global Energy Concepts LLC (GEC) in a DOE funded study for the WindPACT program back in 2000 – 2002.

The GEC drivetrain utilized a 2-stage gearbox with a CARB bearing which allows the second stage to free float to maintain alignment between the gear mesh of the first and second stages of helical gears. This has the benefit of being able to absorb most deflections and off axis loading conditions encountered by the stochastic nature of the wind.

Although it also utilizes a 2-stage gearbox, instead of a CARB bearing, the Winergy HYBRIDDRIVE has a different internal bearing arrangement. Winergy’s web site doesn’t provide details, but one of the company’s representatives at the AWEA Conference indicated that they have a double row tapered roller bearing arrangement and bushings with elastomeric dampers as well as a torque tube to accommodate loading and deflections.

Two-stage gearboxes are not new for Winergy. The company also owns U.S. Patent No. 6,459,165 (’165 Patent), which is entitled “Drive train for a windmill” and relates to drive train architecture that utilizes a double row helical set of gearing. It is possible that this prior IP has contributed to the design of the HYBRIDDRIVE system.

The ’165 Patent is directed to a transmission arrangement for a wind turbine including a rotor (1) with several blades (3) secured in a hub (2). The rotor (1) is connected to a generator (6) via a two-stage planetary transmission comprising an input stage (4) and an output stage (5).

The hub (2) is directly connected to the base (10) of the input stage (4) of the two-stage planetary transmission, which is entirely contained in the hub (2). According to the ’165 Patent, this arrangement provides a more compact transmission suitable for higher outputs:

The object of the present invention is a wind-power plant that is more compact and accordingly appropriate for higher outputs, of 2.5-5 MW, is only slightly heavier, and is less complicated. Directly connecting the hub to the input stage of the two-stage planetary transmission renders the transmission more compact.

Winergy also owns U.S. Patent Application Publication No. 2010/0160104 (’104 Application), entitled “Epicyclic gearbox for a wind power installation” and directed to a forced lubrication system on a two stage drivetrain.

Lubrication is an obvious necessity of rotating machinery, but a forced lubrication system saves the cost of a separate external system with pumps and other associated components, and it can also improve overall drivetrain efficiency. The ’104 Application discusses one way in which a forced lubrication system can be made to work for a two stage gearbox with independent channels for each stage

It remains to be seen if the new Winergy design will prove to be as good as the free floating CARB bearing design in terms of reliability and the ability to absorb loads. Winergy advertised the HYBRIDDRIVE at 25 tons, which is very light if that metric actually includes the generator weight. However, it was unclear from the self-contained drivetrain on display at the Expo whether the generator was integrated in what was shown.

One caveat to a lighter weight gearbox is that they need to be able to prevent deflections of the gearbox housing, which can lead to significant reliability issues. Scrimping on housing mass to save weight might contribute to deflection problems and misalignments of their gears.

We’ll have to wait and see if this is a long term issue. If the 25 tons is just the gearbox without the generator, then this isn’t terribly light at all and the extra mass there may serve to inhibit some of those deflections.

The deflection issues are also prevalent because wind turbine OEMs are chasing higher capacity factor ratings with the increased rotor diameters, and the loads on the drivetrain and tower are increasing as a result. The proof will be in the pudding for Winergy as they test and deploy this solution for Fuhrländer AG for their new 3MW, 120m rotor turbine for IEC Class IIa.

With the reliability of the direct drive systems yet to be proven, it’s great to see innovation on gearbox driven designs which take advantage of 30+ years of development and testing to enable more reliable solutions. After all, as Winergy says, “Reliability is our profession.”

Article by Eric Lane and Philip Totaro.

Totaro & Associates is an innovation strategy and patent search consulting firm. To find out more please visit www.totaro-associates.com.