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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'Advanced rotor technologies' taking place on Tuesday, 11 March 2014 at 11:15-12:45. The meet-the-authors will take place in the poster area.

J. Dietrich Mayer WINDCOMP GmbH, Germany
Co-authors:
J. Dietrich Mayer (1) F P Christoph Lucks (1)
(1) WINDCOMP GmbH, Berlin, Germany

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Presenter's biography

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

J. Dietrich Mayer Dipl.-Ing. German
since 01/2013 windcomp GmbH, Managing Director
since 06/2010 SITAC RE PvtLtd, India, Technical Director
since 05/2008 ADMYRE GmbH, Managing Partner
04/2006 – 04/2008 Natenco GmbH, Managing Director
07/2005 – 02/2006 Iberdrola Renewables GmbH, Managing Director
01/2001 – 06/2005 eternegy GmbH, Managing Director
10/1995 – 12/2000 DEwind GmbH, Founding Partner/Director
11/1992 – 08/1995 Ventis GmbH, Head Global Sales
Experience:
Development, design, operation of WEC
Experts reports , feasibility studies
Measurement technologies
DD of projects and companies
Owner’s/Lender’s Engineer
Project development and management
Interim management

Abstract

Laser based measuring metods for WEC rotors

Introduction

Since the middle of the 1980‘s wind energy underwent a steady growth world wide to become the second biggest source of economically exploitable renewable energy after Hydro.
As development continued turbine capacity constantly grew and so did their dimensions. The growing dimensions caused growing structural loads
The most sensitive part of the turbine is the rotor. All dynamic forces which load the structure are caused and transmitted by the rotor which has to withstand these loads itself.
Any asymmetry in the rotor geometry results in dynamic unbalance and subsequently vibrations and increased loads. Thus tresulting in lower production and higher fatique.


Approach

Laser based measuring methods are able to identify geometric disalignments and asymetries causing loads not coverd by the design calculation assumptions. Further more they can be used to very accurately measure blade vibrations while operation and thus provide the nessesary data to implement a load control of the WEC operation. With a constantly rising number of turbien with rotor diameters of more than 100m these measurement methods can help to reduce the weight of the turbines substantially.

Main body of abstract

Different methods of controlling the rotor geometry of a wind turbine by laser systems are possible:
1. The rotor monitoring system mounted on the top of the nacelle permanently controls the condition of the rotor by measuring the blade-deflection in relation to the generated power.
The measurement provides information about:
Aging
Structural damages
Icing
Pitch faults

2. The ground based geometrical rotor survey allows to check the geometry of the rotor and the tower from the ground.
The measurement provides information about:
Symmetric spacing between the rotor blades
Directional stability
Pitch angle symmetry
Tower vibration

3. The Internal Blade Monitoring System mounted inside each rotor blade, permanently controls the condition of the blades by measuring the blade vibration in different planes.
The measurement provides information about:
Turbulence intensity
Wind direction
Aging
Structural damages
Operational load misbalance between the blades
Icing

Due to the great variety of wind turbines with different technical concepts in the market a variety of measurement methods is needed to cover all machines.


Conclusion

More than 300 wind turbines have been measured and the results are remarkable.
In average 20% of the measured turbines are noticeable due to vibrations caused by aerodynamic imbalance or mass imbalance. About 40% are in a state where it would be advisable to synchronise the rotor blade angle or compensate the mass imbalance or both. The remaining 40% of turbines are in a critical state and synchronisation and/or mass compensation are inevitable to avoid structural damage due to strong vibrations.



Learning objectives
For any turbine > 1 MW it is advisable to check the rotor geometry in the course of a periodic inspection. Especially modern wind turbines for low wind regimes with rotor diameters over 80 m are threatened by such imbalances due to the fact that they are designed to the limits. Above that generation losses occur which may reach considerable dimensions.