Marine Current Turbine Modelization

Transcription

1 Marine Current Turbine Modelization Grégory GERMAIN & al. IFREMER Marine Structures Laboratory 1 1/31

2 Marine Current Turbine Modelization Why do we need to develop tools for turbines modelization? - Performance of turbines array (bathymetry, turbine interactions, velocity profil, turbulence intensity) - Environmental impacts evaluation (sedimental transport, flow modification) - Co/Decommissioning and maintenance Sabella D10 deployment 2 2/31

3 Marine Current Turbine Modelization Problematic of the scale effects : Array effects on environment Site conditions (global flow, sea-bed, free surface) Spatial variations accross the site Inter-array modelling (device interaction) Device operating characteristics Site flow field Turbines characteristics Incident flow char. Ambiant TI Device scale Array scale Coastal Basin scale Near field wake Local effects Operating char. Energy yield Altered flow field Global effects Atlantis turbine exemple 3 3/31

4 Marine Current Turbine Modelization Needs in term of academic research: - Flow characteristic effects (homogeneity, profile, orientation, turbulence intensity) - Combined waves and current effects - Turbine interaction and turbulence effects Free surface effects Wake effects 4 4/31

5 Marine Current Turbine Modelization Needs in term of academic research: - Flow characteristic effects - Combined waves and current effects - Turbine interaction effects 2 kinds of modelization : - experimental Tri-bladed horizontal axis turbine Ondulating membranee Eel Energy - numerical Blade pressure repartition and wake evolution Ondulating membrane: simplified model 5 5/31

6 Marine Current Turbine Modelization Is it possible to developp a generic tool? 6 6/31

7 Wave and Current Circulating Tank Wave and Current flume tank - Ifremer, Boulogne/Mer Dedicated experimental tool for wave/current/structure interaction studies - Test section: 4 x 2 x 12 m 3 - Current < 2,2m/s ; Turbulence intensity rate [3 % ; 20 %] - Regular and irregular waves (0,3 m crest/through ; 2s max ; with current up to 0,8 m/s) - Imposed motions (±46 cm ; ±30 ; ±1m/s) Turbulent flow generated by a grid Regular waves with current Imposed motions synchronized with waves and current 7 7/31

8 Marine Current Turbine Modelization TGL / Alstom Turbine 1/25 tri-bladed scale turbine Parameters Radius R Depth H Flow speed U Rotation speed Reynolds Number Re Maximal Power Fr = Scale 1 Scale 1: = 1:25 Ratio Similitude 9m ~50 m 4 m.s-1 17 tr.min ,2 MW 0,35 m 2m 0,8 m.s-1 90 tr.min W 1/ 1/ 1/ 1/2 1/ -1/2 1/ 3/2 1/ 7/2 Fr = 0,2 R U R U TSR = (gh)1/2 Cp = 1/2 R2 U3 U Re = TSR = 4 - Pmax = f(cpmax) 8 8/31

9 Marine Current Turbine Modelization Performances evaluation in Towing or Circulating tank? Tri-bladed horizontal axis turbine, with active rotor speed control Power coefficient in function of TSR Tidal Energy Round Robin Tests. Comparisons between towing tank and circulating tank results, B. Gaurier, G. Germain, JV. Facq, CM. Johnston, AD. Grant, AH. Day, E. Nixon, F. Di Felice, M. Constanzo, In preparation for IJOME. 9 9/31

10 Performances evaluation - Blocage & turbulence effects - Viscosity effects Saxo Margot 17h45 0,7R 2 Re = 2 1/2 c [U +(0,7R ) ] ~ 1,5.105 (scale 1/25) ~ 1,5.107 (scale 1) c 10 10/31

11 Wake characterization from LDV measurements TSR = 3.5 TSR = 2.5 TSR LDV measurement in the wake of a 3-bladed turbine Wake characterization at two operating points 11 11/31

12 Marine Current Turbine Modelization How to characterize wave effects - Regular and irregular waves - Waves following the current or in the opposit direction - Amplitude max. 30 cm Current max. 0,8 m.s-1 - Periode 0,5 to 2s 12 12/31

13 Waves / turbine interaction Wave effects: Current: 0.4 m/s following waves Waves: 15 cm peack-trough height frequency: 0.6 Hz Waves Waves Blades rotation Combination of Waves and Blades rotation effects 13 13/31

14 Waves / turbine interaction Wave effects: Variations 3 times greater than without waves Flume tank characterisation of marine current turbine blade behaviour under current and wave loading, B. Gaurier, G. Germain, P. Davies, A. Deuff, Renewable Energy, Vol. 59, November /31

15 Waves / turbine interaction BlueWater Trials: floating platform with 2 turbines 15 15/31

16 Turbulence characterization Synchronized flow and turbine power measurements: Flow measurements: - U=0.8 m/s ; TI = 3 et 15% - 2D LDV: 3h ~ 600 Hz Power measurements: - TSR = 4 - Torque sensor: 3h, 100 Hz 16 16/31

17 Turbulence effects on turbine performances Upstream flow turbulence spectrum -5/3 Dissipative range Inertial range Coherent zone Correlation between synchronised power and flow measurements, a way to characterize turbulence effects on marine current turbine, O. Duran, F. Schmitt, B. Gaurier, G. Germain, EWTEC /31

18 y x u y x 6 7 x TI = 3 % I [%] y y Turbulence effects on wake expansion u I [%] x TI = 15 % 18 18/31

19 Turbulence characteristic effects Grid turbulence generator b = bar width;10 M = grid spacing. 0 l = f(b) U Turbulence intensity (%) Flow straightener Turbulence intensity (%) small grid large grideddies that Integral length scale can be thought of as the average size of turbulent contain the greatest proportion of turbulent(a)energy in the flow. (b) M Distance downstream of grid (m) Downstream distance normalised with bar width l b 0.8 m 1m z x 2m Turbine instrumented to measure rotor thrust and torque, and blade In-plane and Out-of-plane bending moments. Flume bed Turbulence decays with distance downstream of grid. Turbine installed at locations behind grid with approximately 15, 10, and 5% turbulence intensity /31

20 Turbulence characteristic effects Case1 I =4.6%; `=0.76m Case2 I =14.3%; `=0.15m Case3 I =10.2%; `=0.18m Case4 I =6.8%; `=0.22m Case6 I =17.8%; `=0.41m (b) (a) 0.5 Case5 I =25.2%; `=0.28m Power Coefficient Power Coefficient Thrust Coefficient University of Southampton turbine Thrust Coefficient IFREMER turbine Turbulence and tidal turbines, T. Blackmore, B. Gaurier, G. Germain, L. Myers, A. Bahaj, EWTEC /31

21 Trials with Southampton University for turbulence effects characterization 21 21/31

22 Marine Current Turbine Modelization Turbines in an array - Hypotheses: - Same depth ; no swell - Different rotation speeds and settings - All other parameters fixed Simplified array of turbines 22 22/31

23 Turbine interaction effects Velocity deficit behind the downstream turbine Efficiency of the downstream turbine with upstream velocity Efficiency of the downstream turbine with discintegrated velocity Experimental study of the turbulence intensity effects on marine current turbines behaviour, Part II: Two interacting turbines, P.Mycek, B. Gaurier, G. Germain, G. Pinon, E. Rivoalen, Renewable energy /31

24 Turbine interaction effects Three turbines in interaction U=0.8 m/s TI = 3 & 15 % TSR [0 ; 8] Configuration {2+1} & {1+2} 24 24/31

25 Experimental constraints - Number of turbines - Waves, turbulence, variable bathymetry - Sedimentary aspects Schématisation de l'implantation d'une ferme d'hydroliennes 25 25/31

26 Numerical modelization BEM (Blade Element Momentum) Method - Wake / Performances - Exp. Data for Cd / Cl of blade profile BEM Method + CFD (Ansys, CFX...) - Wake / Performances - Cells number / Computational time Vortex Methods + Synthetic eddy method for turbulence - Wake + Performances - Unsteady - Only solid walls meshed 26 26/31

27 Numerical modelization of horizontal axis turbines 27 27/31

28 Numerical and experimental study of the interaction between two marine current turbines, P. Mycek, G. Germain, B. Gaurier, G. Pinon, E. Rivoalen, International Journal of Marine Energy, April /31

29 Numerical modelization of horizontal axis turbines Three turbines in interaction Numerical and experimental study of elementary interactions in marine current turbines array Part III: Three turbines interaction, C. Carlier & al., in preparation /31

30 Conclusion Experimental and numerical tools are complementary - waves/current/turbine interaction effects - turbines in array - turbulence effects - sedimentary aspects? 30 30/31

31 And for the other kind of technologies? Ondulating membrane developped by Eel Energy 31 31/31