highlighting of ambient turbulence impact on the interaction effects between tidal turbines

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Highlighting of ambient turbulence impact on the interaction effects between tidal turbines Youen KERVELLA Open Ocean, Marine Energy Consultancy 15 rue Kepler, Brest, France Grégory GERMAIN Benoît GAURIER Jean-Valéry FACQ Thomas BACCHETTI Ifremer, Marine Structures Laboratory Boulogne-sur-Mer, France GCGC – Dunkerque – July, 2014

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Youen Kervella, Ph.D. in hydrodynamics and sediment dynamics, explains the highlighting of ambient turbulence impact on the interaction effects between tidal turbines.

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Page 1: Highlighting of ambient turbulence impact on the interaction effects between tidal turbines

Highlighting of ambient turbulence impact on the interaction effects between tidal turbines

Youen KERVELLA

Open Ocean, Marine Energy Consultancy

15 rue Kepler, Brest, France

Grégory GERMAIN

Benoît GAURIER

Jean-Valéry FACQ

Thomas BACCHETTI

Ifremer, Marine Structures Laboratory

Boulogne-sur-Mer, France

GCGC – Dunkerque – July, 2014

Page 2: Highlighting of ambient turbulence impact on the interaction effects between tidal turbines

22/07/2014 © Open Ocean 2014 All right reserved 2

Context: • Future tidal turbines areas: intense currents and high

turbulence level • Need to know the turbulences impact on turbines

• Need to estimate the environmental impact of tidal

farms

• Numerical models to be calibrated

Study: • Previous measurements with 1 then 2 tidal turbines: # Experimental study of the turbulence intensity effects on marine current turbines behaviour. Part I: One single turbine.

Mycek et al., 2014, Renewable energy. # Experimental study of the turbulence intensity effects on marine current turbines behaviour. Part II: Two interacting turbines. Mycek et al., 2014, Renewable energy.

• Understanding interactions between 3 turbines in various configurations

• Identify the ambient turbulence impact on performance and wake development

Numerical modeling of currents energy extractions by 6 tidal turbines (with and without TEC) in Raz Blanchard area

(Open Ocean)

Introduction Experimental Features Results Conclusion Setup | configurations Config 1 | Config 2

Page 3: Highlighting of ambient turbulence impact on the interaction effects between tidal turbines

22/07/2014 © Open Ocean 2014 All right reserved 3

Pool : # dimensions: 18 x 4 x 2 m # currents, waves, free surface # Input current velocity: from 0,1 to 2,2 m/s # Measurement: LDV, PIV, torque, ..

Experiment: # Input current velocity: 0,8 m/s # Turbulence intensity (TI): 3 and 15% # Measurement system: LDV, torque

Tidal turbines: # 3 horizontal axis three-bladed turbines of 700 mm diameter # TSR=ΩR/U∞ fixed at 4 (maximum power, Carlier et al., 2014) # torque and balance => Cp et Ct

Introduction Experimental Features Results Conclusion device | configuration Performances | Washes

Page 4: Highlighting of ambient turbulence impact on the interaction effects between tidal turbines

22/07/2014 © Open Ocean 2014 All right reserved 4

2 turbines side by side (2D spaced) upstream and one turbine centred downstream

Over speed recovery created between both upstream turbines

Turbine downstream is instrumented (performance)

2 inter-rows distances (DIR) tested: 4D and 6D

Measurements LDV at -1D, 2D and 4D of the second row (wakes)

Introduction Experimental Features Results Conclusion device | configuration Performances | Washes

Page 5: Highlighting of ambient turbulence impact on the interaction effects between tidal turbines

22/07/2014 © Open Ocean 2014 All right reserved 5

• Maximum power at TSR = 4

• Soft differences for

DIR= 4D and DIR= 6D • Global curves form

similar for both TI

• 30 % Cp decrease for TI=15% compared to TI=3%

Introduction Experimental Features Results Conclusion device | configuration Performances | Washes

Page 6: Highlighting of ambient turbulence impact on the interaction effects between tidal turbines

22/07/2014 © Open Ocean 2014 All right reserved 6

• Small differences for DIR 4D and DIR 6D downstream turbine position, except for -1D profil

• No speed increase at

the center of the flume behind the 1st row for TI=3%.

• Speed decrease at the center of the flume behind the 1st row for TI=15%

• Speed decrease behind

turbines is «smoothed» when TI increases (from 45 to 70 % for TI=3% and from 10 to 30% for TI=15%)

Introduction Experimental Features Results Conclusion device | configuration Performances | Washes

Wakes

Page 7: Highlighting of ambient turbulence impact on the interaction effects between tidal turbines

• Obvious role of the ambient turbulence on performance and wakes development:

- TI increase Cp et Ct decrease (30%)

- TI increase Wakes limited development and smaller speed decrease

• Turbulence is key in tidal farm development areas such as Raz-Blanchard, TI between 15 and 25% estimated

• Need to consider TI in numerical modeling

• Study = test tank and in-situ database used to the numerical modeling validation

22/07/2014 © Open Ocean 2014 All right reserved 7

Introduction Experimental Features Results Conclusion device | configuration Performances | Washes

Page 8: Highlighting of ambient turbulence impact on the interaction effects between tidal turbines

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THANK YOU FOR

YOUR ATTENTION

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Email : [email protected]