CWD NewsCWD – Center for Wind Power Drives der RWTH Aachen | www.cwd.rwth-aachen.de December 2018, Nr. 7

From the Research Department 2 CWD is developing and testing new materials for the energy revolution 2

News from the Test Bench 2 Main bearing mounted on plain bearings on the 4-MW test bench of the CWD 2

Workshops 3 After the workshop is before the workshop 3

Spotlight 3 Base load-optimised wind turbine for need-based energy production 3 Tipa: Testing a 100-kW tidal turbine at the CWD 3 CWD project team achieves 3rd place for the RWTH Innovation Award 3

Dear partners and friends of the CWD, dear readers, it is now more than ten years since we started with the development of plain bearings mounted in wind turbine gearboxes. Today, almost every gearbox or turbine manufacturer has a corresponding solution undergoing field trials. Experiences so far and the prognoses for increased deployment in the field are highly positive. As compared to the use of a gearbox, using hydrodynamic main bearings in wind turbines is more challenging. Outside the power production, the bearing in the gearbox are relieved, and it is possible to retain control at low sliding speeds while coasting with the existing solutions. However, in the rotor bearing, even in idle mode, there are significant bearing loads from the rotor weight and the aerodynamic forces at the rotor blades. Based on the positive experiences from the plain bearings mounted in wind turbine gearboxes, we decided to tackle the theme of “hydrodynamic rotor bearings” in our research, since plain bearings are better scalable in size, and it is possible to carry out a bearing replacement with available resources on the tower. In this issue, we present a successful test of the first hydrodynamic main bearing, as well as the development of new sliding materials. I hope you enjoy reading this newsletter and find new points of contact with us within its pages. Yours, Ralf Schelenz P.S.: If you have not already subscribed to the

newsletter and are interested in doing so,

please click on the following link: www.

cwd.rwth-aachen.de/aktuelles/newsletter/.

n Editorial n In this Issue

n Snap-Shot

One of the biggest system test benches for wind turbines in Asia is coming up in Taichung in Taiwan. A

delegation from Taiwan visited the Center for Wind Power Drives to get in contacted with the Aachen-

based experts, regarding possible cooperation in the planning phase.

CWD NewsCWD – Center for Wind Power Drives der RWTH Aachen | www.cwd.rwth-aachen.de Page 2

n From the Research Department

n News from the Test Bench

CWD is developing and testing new materials for the energy revolution

In the research project “WEA-GLiTS”, the CWD, in close cooperation with the RWTH-Institut für Oberflächentechnik (IOT or Institute for Surface Technology), is developing and testing thermal sprayed coatings for their use as plain bearing materials in wind turbines. To start with, the friction and wear properties for a large number of these new materials were investigated in tribometer trials. It was quickly observed that with regard to the wear behaviour, these materials delivered significantly better results than their conventional predecessors.

Then, the five materials with the best intermediate results were tested on a plain bearing test bench under conditions similar to those prevailing in the field. For these investigations, the respective materials were applied using thermal sprayed coating technology on the sliding surfaces of the trial rings. In this process, the material particles are melted and then sprayed on the surface. In this manner, the material composition and the material topology can be controlled, so as to be able to apply tailor-made material systems for different applications. For example, a material system was developed, in which small reservoirs of hexagonal boron nitride are integrated in the material matrix as solid lubricant. These reservoirs get released in

operation, and the additional solid lubricant reduces the friction between the sliding partners. In the plain bearing trials carried out so far, consistently excellent results were achieved with the selected material systems. Even in operation under mixed friction conditions,

excellent friction and wear behaviour could be proved. In the further course of the project, the best of the tested materials will be selected and applied on a 1-MW demonstrator plain bearing. Then, with this demonstrator, thanks to the good testing infrastructure of the CWD, further tests will be carried out under dynamic wind loads.

Main bearing mounted on plain be-arings on the 4-MW test bench of the CWD

With the development of wind turbines of higher and higher capacity, unavoidably, the requirements for all the system components are also becoming more stringent, especially for the main bearing. This relates not only to the dimensions of the roller bearings, but their cost and weight as well. Here, replacing the roller bearings with a plain bearing as the main bearing can be a suitable, and in several aspects better, alternative. As compared to roller bearings, there are advantages in installation space and weight. But with regard to service life, repair and maintenance too, plain bearings are often more cost-effective. Together with Renk AG, scientists of the CWD have developed an innovative concept of a main bearing mounted on plain bearings. The concept of a 4-point

bearing with two radial and one axial bearing point was designed for a wind turbine of the 6-MW class and implemented in a simulation. To validate the results and to investigate the hydrodynamic behaviour under real operating conditions, a 1-MW demonstrator (see the picture) was developed and constructed as a derivative of the 6-MW concept. To that end, the main bearing of an existing wind turbine was replaced by an alternative plain bearing. The results of the test series with this demonstrator confirm the functionality of the concept. Even at low rotational speeds, the bearing shows very good behaviour with regard to the factors of friction torque and temperature. Consolidating on these findings, currently, a 3-MW demonstrator is being developed and tested on the 4-MW test bench of the CWD. The findings of the trials with the two demonstrators will then be fed back towards the optimisation of the 6-MW concept.

Slide element with thermal sprayed coating

electric drive plain bearing load unit

CWD NewsCWD – Center for Wind Power Drives der RWTH Aachen | www.cwd.rwth-aachen.de Page 3

n Spotlight

n Workshops

After the workshop is before the workshop

From 18.12. to 19.12.2018, experts from science and industry will have the opportunity to shape the future of wind power at the 10th CWD Workshop. This time, the focus will be on the following three thematic blocks: n Cross Industry Innovation n Digital Photonic Production -

Perspectives on Tomorrow's World of Individualized & Smart Industrial Products

n Field experience with electrostatic and electrodynamic loads of bearings

Register at workshop@cwd.rwth-aachen.de and realize new research projects together with the Center for Wind Power Drives and exclusive cooperation partners.

Base load-optimised wind turbine for need-based energy production

The research project EFRE was started in January at the CWD. The main goal of the project is the development of a complete onshore wind turbine with a comparably small specific area output. Or, putting it another way: the ratio of the generator output to the rotor diameter should be smaller than normally. Consequently, in comparison to the systems currently in use, at a low load level (= low wind speed), the number of full-load hours increases. With such systems, the use of wind energy at low-wind onshore locations becomes more economical.

In this three-year project, the CWD is cooperating with the companies Windwise GmbH and Eickhoff Antriebstechnik GmbH. Apart from the development, the testing of the nacelle on the system test bench of the CWD and the subsequent measurement of the entire system in the field are all part of the investigation program.

Tipa: Testing a 100-kW tidal turbine at the CWD

Tidal turbines use sea currents, which occur very regularly owing to the rising and falling of the tide, for power generation. So far, such turbines were relatively uneconomical in operation, and are therefore not popular. The EU-funded project TIPA has the development of a tidal turbine in the kW range as its goal. An

innovative drive train concept is envisaged to increase the energy production, reduce the operating costs and make the system more competitive than the existing tidal turbines. At present, a prototype of the turbine is being tested on the 1-MW test bench of the CWD in testing facilities (see picture).

CWD project team achieves 3rd place for the RWTH Innovation Award

In a ceremony, the “FlexPad” team comprising the scientists Tim Schröder, Dennis Bosse and Professor Georg Jacobs from the Chair for Wind Power Drives received the third place prize at the Innovation Awards of the RWTH Aachen.

Every year, university projects that make a particular contribution to the attractiveness of the Aachen Region as an innovation location are honoured with prizes.

The prize-winning new development involves a plain bearing in conical construction that provides protection from wear by tilting the rotating shaft. In addition, individual sliding segments can be replaced easily and at low cost. This development can make a decisive contribution to further increasing the availability of wind turbine and contribute to the energy revolution.

n Disclaimer CWD I Center for Wind Power Drives

ACS I Institute for Automation of Complex Power Systems Prof. Dr.-Ing. Antonello Monti

AIA I Institute of Aerodynamics Prof. Dr.-Ing. Wolfgang Schröder

CWD I Chair for Wind Power Drives Prof. Dr.-Ing. Georg Jacobs

IEM I Institute of Electrical Machines Prof. Dr.-Ing. habil. Dr. h. c. Kay Hameyer

IRT I Institute of Automatic Control Prof. Dr.-Ing. Dirk Abel

PGS I Institute for Power Generation and Storage Systems Prof. Dr. ir. Dr. h. c. Rik W. De Doncker

WZL I Laboratory for Machine Tools and Production Engineering Prof. Dr.-Ing Christian Brecher

Editorial and Contact: Samuel Leupold, M.Sc. Center for Wind Power Drives RWTH Aachen University Campus-Boulevard 61 | D-52074 Aachen

Tel.: +49 241 80 90245 Fax: +49 241 80 92885 E-mail: news@cwd.rwth-aachen.de URL: www.cwd.rwth-aachen.de