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Floating wind turbines: the future of wind energy?

Axelle Viré Faculty of Aerospace Engineering A.C.Vire@tudelft.nl

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Outline

•  Trends in (offshore) wind energy •  Concepts of floating wind turbines •  Some challenges •  Research in the field at LR

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Trends in (offshore) wind energy

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Scale-up success

’85 87 89 91 93 95 97 99 01 03 05 07 09 11 13 15

.05 . 3 . 5 1.3 1.6 2 4.5 5 7.5 8 MW

33 m Ø

171 m Ø

126 m Ø

A380 Airbus

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How big is 8MW?

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How big is 8MW?

Samsung S7.0-171 83.5 m blade length

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Cumulative wind power installations in Europe (GW)

Wind in power – 2015 European Statistics, EWEA report (Feb. 2016)

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Cumulative wind power installations offshore in Europe (MW)

The European offshore wind industry - key trends and statistics 2015, EWEA report (Feb. 2016)

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Types of foundations

Newly installed foundations in Europe in 2015 •  97% monopiles (385 structures) •  3% jackets (12 structures) In 2015, there were 3,313 foundations installed offshore in Europe

97%  

3%  

97%  

3%  

Monopile: www.londonarray.com (May, 2016) Jacket: Alpha  Ventus,  www.offshorewind.biz  (May,  2016)  

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Limitations of current technology

Most seas are deeper than 50 metres Existing commercial foundations are not economically viable in deep seas

Source:  N

.  Anscombe

,  Turbines  take  flo

at,  Pow

er  Engineer,  Vo

l.  18,  Issue

 3  (2

004)  

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Concepts of floating wind turbines

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Main types of foundation

Tension leg platform Semi-submersible Spar buoy

Stability Moorings Buoyancy Ballast Assembly Dry dock Dry dock On/off-shore Installation Towing to site Towing to site Towing or not Depth 50-150 m 50-150 m 100m - ?

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Recent developments

2008  –  Blue  H  (80kW)    

hSp://www.bluehengineering.com/historical-­‐development.html  

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Recent developments

2009  –  Hywind  (2.3MW)   Upcoming–  Hywind  Scotland  Pilot  Park  (30MW)  

www.statoil.com/HywindScotland  

Photo:  Trude  Refsahl/Statoil          

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Recent developments

2011  –  WindFloat  (2MW)   Upcoming  –  WindFloat  Atlan\c  (25MW)  

hSp://www.principlepowerinc.com/en/windfloat  

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Recent developments

2011-­‐2016  –  Fukushima  Forward  project  (2MW,  5MW,  7MW)  

hSp://www.fukushima-­‐forward.jp  

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And much more…

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And much more…

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Combining wind and wave energy

hSp://www.floa\ngpowerplant.com  

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Floating airborne wind energy

hSp://www.skysails.info/english/power  

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Some challenges

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Some challenges

•  Turbine –  Rotor-wake interactions –  Control systems

•  Support structure –  Conservatism in the design (not cost effective) –  Relation between size of turbine rating

•  Mooring lines –  Dynamic behaviour of moorings, esp. in shallow water –  Anchors and soil conditions

•  Electrical infrastructure –  Dynamic power cables

•  Operation and maintenance –  Harsh environmental conditions

•  Design standards –  Lack of experience leads to conservative designs –  Modelling of the system dynamics

Technologically  feasible  but  needs  to  be  cheaper!  

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Numerical modelling

Accuracy

Cost

CFD & FEM

Aero-servo- hydro-elastic

coupling

Reduced modeling Pre-design

Design validation

Detailed design

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Research at LR

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High-fidelity modelling of FSI

Unstructured mesh fluid/ocean model (finite elements)

Fluidity training workshop Nov 2011 – A brief introduction to numerical simulation & Fluidity – Matthew Piggott

© Imperial College London Page 17

A highly multi-scale example: astronomically forced M2 tide in the North Atlantic coupled to the North and Baltic Seas A high resolution mesh is required to resolve the channels connecting the Baltic and North Seas but a much coarser mesh is acceptable in the North Atlantic More than two orders of magnitude difference between coarsest and finest resolutions

hSp://fluidityproject.github.io  

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High-fidelity modelling of FSI

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Applications

•  Wind/tidal turbine modelling through actuator disks –  Abolghasemi et al. “Simulating tidal turbines with multi-scale mesh optimisation techniques”,

Journal of Fluids and Structures 66:69-90 (2016) –  Viré et al. “Towards the fully-coupled numerical modelling of floating wind turbines”, Energy

Procedia 35:43-51 (2013)

•  Dynamics of a floating monopile –  Viré et al. “Towards the fully-coupled numerical modelling of floating wind turbines”, Energy

Procedia 35:43-51 (2013)

•  Aerodynamics of kite wings –  Rajan et al. “Fluid-structure interaction of an inflatable kite wing”, Airborne Wind Energy

Conference (2015)

•  Wave-structure interactions

–  Viré et al. “Application of the immersed-body method to simulate wave-structure interactions”, European Journal of Mechanics B/Fluids 55:330-339 (2016)

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Applications

•  Wind/tidal turbine modelling through actuator disks –  Abolghasemi et al. “Simulating tidal turbines with multi-scale mesh optimisation techniques”,

Journal of Fluids and Structures 66:69-90 (2016) –  Viré et al. “Towards the fully-coupled numerical modelling of floating wind turbines”, Energy

Procedia 35:43-51 (2013)

•  Dynamics of a floating monopile –  Viré et al. “Towards the fully-coupled numerical modelling of floating wind turbines”, Energy

Procedia 35:43-51 (2013)

•  Aerodynamics of kite wings –  Rajan et al. “Fluid-structure interaction of an inflatable kite wing”, Airborne Wind Energy

Conference (2015)

•  Wave-structure interactions

–  Viré et al. “Application of the immersed-body method to simulate wave-structure interactions”, European Journal of Mechanics B/Fluids 55:330-339 (2016)

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Wave-structure interactions

•  Regular waves of steepness where and •  Intermediate water depth: ( ) •  Inviscid flow Reference: linear wave theory (MacCamy & Fuchs, 1954)

ak = 0.01gk tanh(kh) = (2⇡T )2 T = 1

h/�0 = 0.45 �0 = 2⇡g/!2

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Wave-structure interactions

0 5 10 15 20

−1

−0.5

0

0.5

1

x/h

η/a

0 5 10 15 20

−1

−0.5

0

0.5

1

x/h

η/a

Theoretical solution Defined-body approach Immersed-body approach

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Wave-structure interactions

•  Irregular waves •  Amplitudes of the focused wave ( is the Jonswap peak) •  The amplitude is maximum at: and Reference: second-order calculation (Sharma & Dean, 1981)

Asumkp = 0.018 Asumkp = 0.09kp

xf = 10h tf = 7.5T

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Wave-structure interactions

8 9 10 11 12

−0.5

0

0.5

1

t/Tp

η/Asum

8 9 10 11 12

−0.5

0

0.5

1

t/Tp

η/Asum

CFD Second-order solution

Asumkp = 0.018 Asumkp = 0.09

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Wave-structure interactions

With defined pile Without pile

6 7 8 9−1

−0.5

0

0.5

1

t/Tp

η/η⋆max

6 7 8 9−1

−0.5

0

0.5

1

t/Tp

η/η⋆max

Asumkp = 0.018 Asumkp = 0.09

With immersed pile

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Wave-structure interaction

0 2 4 6 8 10 12 14−0.3

−0.1

0.1

0.3

0.5

0.7

t∗

F ∗|body

Immersed bodyHu et al. (num)Hu et al. (exp)

1.4 1.6 1.8 2 2.2 2.40.3

0.4

0.5

0.6

0.7

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Upcoming works

•  CFD modelling of the TetraSpar concept (Stiesdal, 2016), with Deltares and NTNU

•  Re-design of blades for model-scale testing, with MARIN

•  Build synergies at TU Delft and internationally on floating wind energy

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The future of wind energy?

Subsidies and costs of EU energy, Ecofys (Nov. 2014)

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The future of wind energy?

   Market  study  floa\ng  wind  in  the  Netherlands, TKI Wind Op Zee (Nov. 2015)

Cost comparison for a wind farm of 800 MW installed capacity

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Thank you for your attention