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Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 20091
Introduction to Ocean
Wave
Energy
Conversion.
Aurélien Babarit
Hydrodynamic and Ocean Engineering Group
Laboratoire de Mécanique des Fluides (CNRS UMR 6598)Ecole Centrale de Nantes
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 20092
Outline
> Introduction
> Ocean wave energy : resource
> Wave energy converters : a review of the technology.
> Current issues.
> The full scale test site : SEM-REV
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 20093
The
Hydrodynamic
and
Ocean
Engineering Group
Hydrodynamic and Ocean Engineering GroupStaff : 39/19, Head : Bertrand Alessandrini
Laboratoire de Mécanique des FluidesStaff : 88/37, Director : Alain Clément
EMCI EMN DAH
• Free surface flows• Scale of floating structures (ships, offshore platforms)• Numerical and experimental approaches
Tools :
Numerical tanks Bassins numériquesExperimental tanks Full scale test site
Expertise :
Research interests :• Ocean wave modelling and propagation• Performances (ship resistance, seakeeping, manoeuvrability)• Impact – Violent Flows.• Marine Renewable Energy
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 20094
Marine Renewable
Energy
Tidal Energy.
The Rance’s barrage, 240MWc
Marine Current Energy.
Seagen, 1.2MWc
Ocean Wave energy.
Pelamis, 750MWc
Offshore Wind Energy.
Hywind, 5MWc
Pacific OTEC, 5MW © OCEES International
Ocean Thermal Energy.
Osmotic energy.
Statkraft, 20 MWc
Estimation of the harnessable energy = 120 000 TWh/an. Source International Energy Agency.
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 20095
Ocean Wave Energy : Resource
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 20096
Ocean
waves
> Sun Wind Ocean waves
> Measurement
Sea surface of hurricane Isabel© Mike Black @ NOAA
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 20097
Ocean
waves
Wave> A random phenomenon
FT
Wave energy spectrum :> Steady on a hour scale> Parameters :
• T1 peak period• H13 significative height
T1 (s) H1/3 (m) P (kW/m)
6 1 2.4
9 2.5 22.5
17 14 2500Measured during Hurricane Katrina
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 20098
Estimation of
the
Wave
Energy
Resource
> Power available by wave front in a given sea state (T1 , H13 ) :
> Scatter diagram of probabilities of occurrence C (T1 , H13 ) of sea states at a given location • From met-ocean models.• From measurements (datawells, waveriders)
over several years
> Mean annual power available on a given state : île d’Yeu (46°41.45‘N / 2°25.65'W)
( ) 23/113/11 4.0, HTHTPwave =
( )( )∑>=<
3/11 ,
23/113/11,4.0
HTwave HTHTCP
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 20099
World wave
energy
resource
Estimation of the harnessable wave energy ~20000 TWh/an (International Energy Agency)
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200911
Wave
energy
conversion
> Started in the 70’s (first and second oil crisis)
> Almost stopped in the 80’s (cheap oil again)
> Re-started in the beginning of the 90’s.
> At the moment, more than 60 projects (technologies) in development around the world (mainly Europe)
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200912
Three
main categories
> Oscillating Water Columns (OWC)
> Overtopping systems
> Wave activated bodies
+ uncommons…
LIMPET (500kW)
pelamis (750kW)
Seawave
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200913
Configurations
Attenuator
Terminator
Point absorber
λ = wavelength, ~50 à 150 m
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200914
Overtopping
systems
> Principle
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200915
TAPCHAN (Norvège)
> Built in 1985, close to Bergden> 350 kW> Stopped in 1991
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200917
Seawave
Slot-cone
Generator
(Norvège)
> 1/15 model tested in 2005
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200918
Wavedragon
> Prototype : ¼ scale> 237 t> 20 kW
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200920
Oscillating
Water
Columns
> Principle :
LAND
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200921
The
Pico plant (Azores)
> Wells turbine
> 400 kW
> 12x12 m chamber
> Production : 0.54 GWh/an
> 1.3 M€
> 0.23 €/kWh
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200923
OWC in a harbour
> Sakata harbor (Japon)
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200924
OWC in a floating
structure
OSPREY 2000
2MW
WAVEGEN UK
OSPREY 2000
2MW
WAVEGEN UK
Energetech (Australie)
Sperbuoy (UK)
The mighty whale (Japon)
BBDB (Irlande)
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200925
Wave
activated
bodies wave
energy
converters.
> Salter’s duck (1983)> 14 m diameter, 90 m long, 11000 t
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200926
Mc
Cabe
wave
pump
(Ireland)
> Application to dessalinasation> 1996, 40 m long> 60 kW ~ 300000 m3/an, 0.2€/m3
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200927
AWS (Pays bas)
DémonstrateurÉchelle 1/1
2MW
Mise à l’eau été. 2004Leixoes(Portugal)
> Direct drive
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200928
Pelamis
(Ecosse)
> 4 x 30 m, 3.5m diameter – 750kW> Hydraulic Power Take Offs
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200929
Pelamis
(Scotland)
1/20 scale model test at Ecole Centrale de Nantes (every year since 2003)
1/7 scale model test
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200930
Pelamis
(Scotland)
March 2004
April 2004: first full scale trials at sea
Since september 2008: first commercial wave energy power plant connected to the grid in Portugal
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200931
SEAREV (Nantes)
> Principle :• A moving mass in a closed buoy• Relative motion is used to drive a Power
Take Off.> Advantages :
• Closed system, all moving parts are dries• Internal reference.• No end stops : the moving mass is a
cylinder with an off centered gravity center.
> The relative motion is controlled.
> 2 patents (2006, 2008, property of CNRS)
> Collaborations
Yoke
Hull
Heavy
cylinder
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200932
Artistic
view
Hull
Cylinder
Hydrauliccylinders
HP accumulator
Hydraulic motor Generator
Electric cable
BP accumulator
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200933
Numerical
models
> Frequency and time domain> Linear and non linear hydrostatic and Froude
Krylov forces (calculation on the exact wetted surface).
> Linear and non linear moorings.> Fluid structures interactions using potentiel
theory
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200934
The
SEAREV model
+ Measurement of the incident wave using wave probes+ Motion tracking system using video cameras (Qualisys).+ Brakes for application of the latching control.
Electrical motor Inertial measurement unit
Cylinder
Buoy
Measurement of the relative motion
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200935
The
Hydrodynamic
and
Ocean
Engineering Wave
Tank
Dimensions: 50 x 30 x 5 m + Pit 5x5x10m
48 PC-controlled flaps (electrical motors)
Reflected waves absorption (wavemaker)
Motion tracking system
Parabolic-shape stainless-steel beach
T = 0.5 ~ 5 s
Hmax ⁄
2 mIrregular and regular waves
Unidirectional and crossed waves
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200936
Tank tests
> Two sets of tank tests in 2006.• Scale 1/12.• Development of control algorithms.• Validation and calibration of numerical models.
> New experiments.• New design• Scale 1/25th • Experiments on moorings and survivabilities
issues.
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200938
Towards
a full scale
prototype
> Technical feasbility proven in 2007.
> Towards a full scale prototype.
• 25 m, 1000 t.> Looking for industrial
partners.
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200939
> A powerful resource
> Many (too much?) technologies in development• No consensus on the technological solution (contrarily to land based
wind energy).
> First (pre) commercial plant at sea (25c€/kWh)
> Many technical and scientific issues remain to be tackled to bring costs (and risk) down.
Summary.
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200940
> Scientific issues :
Wave
energy
converters
Hydrodynamicprocess
Power TakeOff
ResourceMechanicalEnergy Electricity
Wave energy converters
Seakeeping : large amplitude of motions
Interactions in arrays of wave energy converters
…
Direct drive
Storage and smoothing of the power
…
Control - command
Optimal control
Control strategies for arrays
Strong coupling
Sea state description
Wave prediction
Main area of ourresearch activites
Collaborations
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200941
The full scale test site : SEM-REV
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200942
The
SEM-REV facility
: Full scale
test site
ECNLaboratory
Wave EnergyGrid connectedTest centre
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200943
• one berth, grid connected (2.5 MW)• 30m water depth, flat and sandy bottom• 1 km2 fully instrumented sea area (ADCPs, waveriders buoys, HF radar, …)• radio link (data) to the onshore base
• Budget : 5.5 M€• Operational in 2010
Characteristics
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200944
Thank
you
for your
attention
« Utilisez la nature, cette immense auxiliaire dédaignée. (…) Réfléchissez au mouvement des vagues, au flux et reflux, au va-et-vient des marées. Qu'est-ce que l'océan? une énorme force perdue. Comme la terre est bête! Ne pas employer l'océan! »
Victor HUGO, Quatre-vingt treize (1874)
Books on wave energy :
• Falnes J., 2000, Ocean Waves and Oscillating Systems : Linear interactions including wave-energy extraction, Cambridge University Press
• Cruz J., 2008, Ocean Wave Energy : Current Status and Future Perspectives, Springer.
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200946
Seakeeping
: Large amplitude of
the
motion
> Usual methodology for designing offshore structures (platforms, off-loading buoys, …)
PrototypeTank testingNumerical simulation
Virtual mode Small scale model (1/20) Full scale
> Methodology inadapted in case of wave energy converters, because :• Linearity assumptoins.• Wave energy converters are designed by purpose for large amplitude of motions.
> Standard CFD tools are non satisfactory:• CPU time : 1day / wave period. • Inaccuracy in modelling and propagating ocean waves, especially in random waves.
New class of numerical methods, based on potential theory under weak-scatter assumptions.
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200947
Temps adimensionnel
Ang
lede
tang
age
(°)
0 0.2 0.4 0.6 0.8 1-20
-10
0
10
20
Potentiel linéaireIcareExperience
Large amplitude of
the
motion : SWENSE approach
> Improvement of the accuracy
> CPU time is long : ~semaine.
Green : ExperimentsBlue : Linear theoryRed : RANSE solver
Institut Henri Poincaré – Wave Turbulence Workshop - April, 10th, 200948
Wave
interactions in large arrays
of
wave
energy
converters
> Wave interactions between systems can be :• destructive : masking effects.• constructive : focusing.
> Issues : • (Very) large arrays (>10)• Environmental impacts.
Experimental model Comparison between experiments and numerical model
Recommended