An integral component of a wind turbine, the drivetrain is continually evolving as new concepts and designs are explored. As larger turbines are developed, and more wind farms are installed in deeper water, the service and maintenance of each component must also be considered. Want to learn more about this topic? Please also visit our website: http://bit.ly/wind-drivetrain

1. Reliability and Serviceability of Drivetrains
Offshore wind power is undergoing intense growth in order to meet the European energy
targets laid out for 2020. Research and development is being carried out into all aspects of
the industry as it attempts to emerge as the main source of renewable energy throughout
Europe.
An integral component of a wind turbine, the drivetrain is continually evolving as new
concepts and designs are explored. As larger turbines are developed, and more wind farms
are installed in deeper water, the service and maintenance of each component must also be
considered.
The design of drivetrains is moving towards direct drive technology, and new initiatives are
also being developed in hydraulic and hydrodynamic technology. All of the new concepts and
designs have reliability as a central aim in development, as drivetrain failure is a big
contributor to the time a wind turbine spends out of commission.
Operation and Development
Planned maintenance at sea is a much more complicated routine than on land, and
unexpected service visits are highly unwelcome. A wind turbine drivetrain may have a yearly
maintenance routine consisting of generator brush inspections, gearbox oil and filter changes,
LSS bearing grease refill and container removal. The extra overheads of a boat, a crew, and
sea trained technicians can easily amount to several thousand pounds; and the weather can
delay schedule and increase the costs.
According to data gathered from existing offshore wind farms, drivetrain, generator, and
gearbox failures account for around 14% of all down time for offshore turbines. Due to the
complexity of repairs, however, they account for 39% of the time a turbine is out of
commission per year. Typical failures include HSS generator and bearing damage, coupling
degradation and internal gearbox component failures.
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2. There are several causes associated with drivetrain failure, some specific to the offshore
environment. Wind speed can increase considerably even when only a short distance from
the shore; while this improves the potential for energy production, it significantly increases
the stress and pressure placed on components and can cause fatigue damage far quicker
than in onshore applications. Turbulence is also greatly increased at sea, and although
designers plan the layout of wind farms to avoid it, turbines can still be subject to
downstream turbulence from other turbines in the grid.
Direct drive technology is being developed to eliminate the gearbox from the drivetrain
assembly altogether. While Hybrid technology is being developed to combine very simple and
reliable gearboxes with direct drive systems. These are being designed with maintenance
fully in mind, and monitoring systems are being developed which can highlight weaknesses
before they become failures to proactively prevent down time.
ETI drivetrain test rig
To support the Crown Estates’ round three offshore programs in the UK, the Energy
Technologies Institute is building a wind turbine drivetrain test rig in Blyth, Northumberland.
The rig will be open access and will be the world’s largest test centre, able to test turbines up
to 15MW. The indoor test rig is being designed so that the whole nacelle can be tested prior
to installation, giving much more commercial security to large scale deployment.
Built on the Narec (New and Renewable Energy Centre) site in Blyth, and known as Project
Fujin, the test rig will enable drivetrain testing in different dynamic scenarios, and will test
the whole drivetrain system. New technologies and prototypes can be rigorously tested
before trial installation, helping to speed up the design process.
Opening in late 2011, the centre will test gearbox design, validation and development,
converter and control validation, grid disconnection simulation, component testing and
research, environmental impact simulation, and lightening strike protection systems.
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IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany
t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de
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3. Artist’s impression of the drivetrain test centre, Source: Narec
ETI’s Chief Executive, David Clarke, said of the test centre, “This world leading facility will
allow turbine manufacturers and engineering teams to test the reliability of their equipment
under realistic load conditions without the expense and risk of deploying them offshore.”
Ricardo MultiLife Bearing
Ricardo was selected in collaboration with HORIBA to design plans for the construction of the
ETI drivetrain test rig, and the company was also given a grant of three million pounds by the
Northern Wind Innovation Program (NWIP) to develop durable gearbox bearings for wind
turbine gearboxes.
A global company, Ricardo is a key developer within the wind turbine drivetrain sector, and is
involved in the design of modular solutions for drivetrains. The MultiLife bearing project was
initiated to increase the durability and reliability of gearbox bearings for use offshore.
Bearings are prone to several different types of failure and in-service maintenance is very
difficult due to conditions.
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IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany
t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de
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4. Source: Ricardo
Research by Ricardo found that Wind turbine bearings with fixed inner races can wear in a 40
degree arc, resulting in premature failure. Ricardo has been tasked with developing a
prototype bearing which will have a five times increase in lifespan. The final design of the
MultiLife bearing provides several benefits; it can be retro-fitted to existing turbines with very
little change needed to the gearbox. Ricardo is confident that this year it will complete the
project and reveal a bearing with a five times increased life expectancy.
Want to learn more about current technologies and developments in the
drivetrain concepts for wind turbines?
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IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany
t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de
Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de