Development of a MW scale wind turbine for high wind complex terrain sites the MEGAWIND project

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Development of a MW scale wind turbine for high
wind complex terrain sites the MEGAWIND project
European Wind Energy Conference 2006 Athens,
Greece, 27/2/2006-2/3/2006 Technical
TrackSession CT3 Innovative turbines,
components, systems and techniques

• P. Vionis, D. Lekou, F. Gonzalez, J. Mieres,T.
  Kossivas, E. Soria,
• E. Gutierrez, C. Galiotis, T. P. Philippidis, S.
  Voutsinas, D. Hofmann

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The Partners

• Industrial (3)
• NECSO (ES), MADE (ES) and
• GEOBIOLOGIKI SA (GR)
• Research Organisations (4)
• CRES (GR), EC-JRC-IPCS (IT),
• CIEMAT (ES) and ICE/HT (GR)
• Universities (3)
• UP (GR), NTUA (GR) and
• DU/NU (UK)

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Project Background
Some of the most promising areas for wind energy
development are in high wind mountainous sites of
poor infrastructure High transportation and
erection costs are discouraging the installation
of MW size WTs in such areas
Strategic aim To develop procedures to
circumvent the barriers hindering the deployment
of large wind turbines in such sites
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Project objectives

• The development of critical components of a 1.3
  MW WT focusing on the following aspects
• an alternative tower allowing for on-site
  manufacturing
• high wind speed optimised blades featuring
  splitting parts
• advanced geabox aiming at high reliability, easy
  maintenance and low noise

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Advanced Composite Tower

• Extensive research has been carried out with
  regard to
• composite materials suitable for composite
  structures
• alternative joining designs
• alternative tower designs
• Environmental effects on selected materials
• Design focused on 2 alternative concepts
• Monolithic (GFRP)
• Hybrid (GFRP high strength concrete)
• Design is strongly influenced by manufacturing
  processes and relevant costs
• Large scale structural tests on ½ length
  1/3-scale prototypes of both designs have been
  carried out

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Monolithic Tower test configuration in
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During test and final failure
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Monolithic Tower final test in
Base Moment N?m versus Curvature m-1
1.8 MNm
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Sandwich Tower test configuration in
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Sandwich Tower test configuration in
Base Moment N?m versus Curvature m-1
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Performance of H. Tower
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Comparison between M. H. Towers
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Advanced Composite Tower Conclusions from 1/3
scale tests

• The monolithic tower meets all the serviceability
  and safety criteria
• The equivalent peak bending moment at the 1/3
  scale was 0.72 MNm, while the tower failure
  occurred at 1.8 MNm (SF2.3)
• SF could be improved to 3.2 with better quality
  assurance on the filament winding lay-up
• The hybrid tower meets all the serviceability and
  safety criteria, although the production quality
  assurance lower than ordered
• Tower base moment at failure 1.17 MNm (SF1.6)
• SF could be improved to 2.5 had the FRP material
  modulus been only equal to the monolithic tower
  tested.

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Advanced Composite Tower- Final Design

• Total tower length 40.8 m
• Diameter varying from 3.14 m (bottom) to 2.40 m
  (top)
• 17 parts 2.4 m each
• 8 parts carbon fibre skins and polyurethane core
• 1 part hybrid glass/carbon fibre skins and high
  strength concrete core
• 8 parts glass fibre skins and polyurethane core

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Advanced Composite Tower- Constructed
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Advanced Composite Tower- Test preparations
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Split Rotor Blade Aerodynamic Design
Guidelines

• Optimize the blade for maximum Energy Production.
• Design a blade to produce a rated power of 1300
  KW.
• Design new optimised airfoils.
• No use of external aerodynamic reinforcements.
• Design of the Airfoil sections
• Generate a database of airfoils, optimized for
  maximum energy production over the whole range of
  their operation
• Design airfoils insensitive to the transition of
  their boundary layer.
• Select airfoils exhibiting a flat top CL and a
  smooth post stall drop of CL in order to
  reduce/avoid stall induced vibrations.

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Split Rotor Blade Designed profile CL-CD
characteristics
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Split Rotor Blade Structural design
T-Bolt concept was selected for the intermediate
joint
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Split Rotor Blade Intermediate Joint Design

• Designed According to VDI 2230
• 45 necked-down bolts (M24x2)
• Bolt Length 453mm
• Design Load (ECDneg)
• F 85.878 kN

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Split Rotor Blade - Structural Design FEM model
of blade 30_1(GRP) Tsai-Wu failure criterion
IEC 61400-1 Class I
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Split Rotor Blade Component testing

• Full-scale specimen
• study the behaviour of the intermediate joint
• Bolt preloading
• Estimation of joint constant,F
• Separation Load
• Static and fatigue strength of joint

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Split Rotor Blade
Manufacturing
Blade inner part - 4595 kg - 12.4 m
Blade outer part - 1828 kg - 17.25 m
ready for transportation
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Split Rotor Blade Blade assembly
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Split Rotor Blade Full scale Testing (edgewis
e)
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Split Rotor Blade Full scale Testing (flapwis
e)
Max test load 4.3 MNm at root
Max test load 4.3 MNm at root
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Advanced Transmission System

• Feasibility Studies of Alternative Gearbox
  Concepts
• 4 Epicyclic Gearboxes
• 5 Parallel Axis Gearboxes
• Selected Gearbox 3 Stage Single Helical, Dual
  Load Path with Balance Beam Load Equalisation
• Advantages - Lowest Part Count - 8 Gears
• 12 Bearings
• - Low cost
• - No Significant Weight or Size Penalty

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Advanced Transmission System 3 Stage, Dual Load
Path, Balance Beam
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Advanced Transmission System 3 Stage, Dual Load
Path, Balance Beam

• PROS
• Simple load path balancing technique
• Very compact overall design (40 smaller than
  standard dual path parallel axis gearbox)
• Small number of Gear elements
• Small number of Bearings
• Good access to both gear elements and bearings
• Potential to design very quiet gearbox

• CONS
• Slightly higher and wider than reference
  Epicyclic 2 Helical stage arrangement

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Measurement campaign

• Since the prototype gearbox could not be
  manufactured in time, the dynamic behaviour of a
  gearbox of similar concept (3 stage, duplex load
  path) operating on a MADE 1.3 MW WT was
  investigated
• An advanced measuring system was implemented on
  the refitted gearbox components
• Measurements included
• bending moments and torsion on the main shaft,
• intermediate shaft torque
• axial load on the low speed shaft
• movement of the gearbox
• Power data, rotor speed and azimuthal position
• Meteorological data

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Sensor installation
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Measurement campaign
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Conclusions

• Innovative solutions have been pursued for the
  major WT components tower, rotor gearbox
• TOWER
• A 40 m composite tower was for the first time
  manufactured and full scale tested
• Extensive RD work on alternative tower designs,
  suitable composite materials, joining systems and
  manufacturing methods
• Joining of the shell rings can be carried out
  on-site
• FRP towers offer new possibilities for the
  on-site logistics and assembly
• Further effort is needed in the fatigue
  verification of the tower concept and the design
  of special tower details

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Conclusions

• SPLIT BLADE
• The 30 m blade is the biggest split blade built
  and full-scale tested to date
• The prototype blade was manufactured using low
  cost material and simple production methods. If
  more advanced production methods and materials
  are used, bigger split blades could be
  efficiently implemented
• The blade sustained successfully static test
  loading. Failure of a number of bolts of the
  blade joint during fatigue testing lead to joint
  design refinement
• The advantages of the split blade concept were
  demonstrated also in practice, when the blade was
  transported from Greece to Denmark by truck for
  testing in 3 days

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Conclusions

• TRANSMISSION SYSTEM
• A number of alternative gearbox arrangements has
  been investigated
• An optimal gearbox for wind turbines has been
  designed, having the novel arrangement of a three
  stage, duplex load path with single helical gears
  and a balance beam to equalise torque on the
  intermediate gear shafts
• The assessment of the proposed gearbox design in
  service is an issue for further investigation
• The created measurement database from the
  operation of a similar concept gearbox is a
  valuable tool for getting a better insight in the
  loading of this type of gearbox

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The happy team in front of the tower
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The happy team in front of the blade