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

Grgory GERMAIN

Benot GAURIER

Jean-Valry FACQ

Thomas BACCHETTI

Ifremer, Marine Structures Laboratory

Boulogne-sur-Mer, France

GCGC Dunkerque July, 2014

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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

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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=R/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

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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

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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

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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

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

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Introduction Experimental Features Results Conclusion device | configuration Performances | Washes

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Email : [email protected]

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Open Ocean Brest 15 rue Johannes Kpler

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THANK YOU FOR

YOUR ATTENTION

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Email : [email protected]