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Tuesday, 11 March 2014
16:30 - 18:00 Advanced drive trains technologies
Hardware Technology  


Room: Tramuntana
Session description

In recent years several alternative drive train solutions have been proposed and also introduced on prototypes and in larger series. The new solutions seek to reduce the cost of energy by improving the reliability and service costs while keeping the initial costs competitive. Only a few of the new solutions have found their way into the competitive onshore market. The session will look into some of the potential incremental improvements that can be foreseen on the mainstream onshore market, but also look at some more radical concepts that may hold potential.

Learning objectives

  • Get an understanding of the options for journal bearings when used in the gearbox
  • See how field experience and numerical analysis can be used to optimise the performance of gearbox solutions
  • Learn more about the potential of magnetically geared solutions for wind application
  • See some of the potential improvements that can be implemented on drivetrains with gearboxes
Lead Session Chair:
Steffen Haslev Sørensen, RCA Engineering, Denmark

Co-chair(s):
Andreas Reuter, Fraunhofer IWES
Chris Kirby Magnomatics Limited, United Kingdom
Co-authors:
Stuart Calverley (1) F P Chris Kirby (1) Ewoud Stehouwer (2) Ben Hendriks (2)
(1) Magnomatics Limited, Sheffield, United Kingdom (2) Garrad Hassan, Sint Maarten, The Netherlands (3) University of Sheffield, Sheffield, United Kingdom

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2014 and are published here unedited

Mr Kirby formed his first high technology company in 1997. He is currently CEO of Magnomatics Limited in the UK. He studied Electronics and Computer Science at the University of Keele and is a Chartered Electrical Engineer. After conducting research in ultrasonic instrumentation he founded NDT Solutions which developed advanced non destructive scanning equipment for the wind and aerospace sectors. He founded Magnomatics in 2006 to exploit magnetic gearing innovations from the University of Sheffield. He formed a team of engineers to develop large magnetically geared machines in 2007 with a focus on marine propulsion and direct drive WT generators.

Abstract

Front mounted magnetically-geared pseudo direct drive generator

Introduction

The input rotor speed and torque of offshore wind turbines leads to large generator sizes, so typically a multistage gearbox is used to reduce generator size and mass. However; gearbox losses reliability and maintenance requirements make direct drive solutions attractive, if only the generator size could be reduced. A magnetic equivalent to a planetary gear has been combined with a permanent magnet generator to reduce the size and mass of the drivetrain and give high efficiency. This novel direct drive generator is combined with a front-mounted kingpin turbine architecture to deliver class-leading cost of energy.

Approach

A nacelle with a stationary main shaft kingpin, matching the generator diameter, has been chosen for its low mass, scalability of design and ease of installation and maintenance. The cost of energy has been compared with a direct drive permanent magnet, a medium speed permanent magnet and high speed DFIG drivetrain configurations. The cost of energy model includes engineering models for the rotor nacelle assembly and support structure CAPEX, bill of parts and operational O&M. This architecture is suitable for differing wind classes and rotor sizes using conventional production methods for sizes up to 20MW with >200m rotor diameter.

Main body of abstract

A magnetic gear has been magnetically and mechanically integrated with a permanent magnet generator. This novel Pseudo Direct Drive generator uses well understood principles and conventional production techniques. It has been proven in a 300kW prototype that replicates the magnetic and mechanical stresses of a multi-megawatt generator. The concept combines the advantages of direct drive and geared systems: no gear contacts and a compact generator. With high operational reliability, this layout offers the possibility to scale to a 200 m diameter, 10 MW turbine, with the present bearing supply chain and is one of the innovations being investigated at 10 to 20 MW-scale as part of the EU funded Innwind project.
The measured data from the prototype has confirmed the modelling techniques used to design and evaluate multi-megawatt systems. The extremely high part-load efficiency of the generator requires only convective air-cooling systems that increase reliability and give a low maintenance drivetrain. The front-mounted kingpin architecture has a tower top mass 10% lower than traditional layouts and leads to minimal main bearing loads. It also gives a highly accessible system that can be replaced in a single lift, without the need for an external crane. This turbine architecture gives low capital and operational cost and delivers class-leading cost of energy.


Conclusion

The pseudo direct drive generator offers high efficiency, reliability and low maintenance with the size and mass of a geared integrated drive train. When combined with a front-mounted kingpin turbine design, this leads to a highly optimised wind turbine system with class leading cost of energy. The generator has been successfully tested at 300kW and there is high confidence that it can be economically extended to the multi-megawatt range.


Learning objectives
The benefits of magnetically geared pseudo direct drive generators are high part-load efficiency, with the size and mass of traditional geared drive trains. Scalable for large offshore wind applications, they enable the design of low cost, low maintenance wind turbines that can deliver class-leading cost of energy.