Large Scale Assembly and Erection of Floating Offshore Wind Turbines

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• Large Scale Assembly and Erection of Floating
  Offshore Wind Turbines
• M.Sc Anders Myhr
• M.Sc David W. Moss
• Prof. Tor Anders Nygaard
• European Offshore Wind, Stockholm
• 16.09.2009

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Aquilo, the concept

• Flexible and simple
• Minimize risk
• Horizontal assembly
• Reduce the number of vessels
• and cranes during the operation
• Optimized and developed for
• turbines with single buoy floaters

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Development of model

• ANSYS finite element model of semisub-
• platform, cradle and wind turbines
• Platform setup
• Metacentric height gt 1 meter
• Natural periods gt 20 sec
• Wave forces by Morrisons Equation
• Point pre-calculated wind force
• Buoyancy
• Gravity

Heave amplitude m
Time s
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Limits and assumptions

• Operate during 90 of
• North Sea weather conditions
• Linear wave trains with a
• significant wave height of 6m
• Static wind field with a
• speed of 36 m/s

Height m
Wind speed m/s
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Turbine loads in horisontal position

• Cantilever
• Nacelle loads
• Necessary length of Aquilo

NJORD Stress MPa
Length from tower base m
5MW Hywind Stress MPa
Length from tower base m
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Turbine loads in vertical position
Wave force N/m

• Wind force
• Wave force
• Keel-effect

Depth m
Height m
Point forces N
Height m
Wind force N/m
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Loads during pivotation

• Peak loads
• Model errors
• Wave slamming

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Fatigue of the construction

• Horizontal position
• Vertical position
• During pivotation

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Evaluation

• Assembly frequency
• Investment cost
• Flexibility

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Conclusion

• The Aquilo concept should be a decent contender
  in future assembly and erection of offshore wind
  turbines.
• The versatility for application on different
  assembly platforms are yet to be proven but
  should result in lesser dynamic response and
  loading on both the pivot cradle and turbine
  towers.
• Further work
• More load combinations
• Damping and Eigen-frequencies
• Winches and anchor handling
• Economics

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Thank you for your time.

• For further information please contact me at
  myhr.anders_at_gmail.com