wave power conversion systems for electrical energy production
DESCRIPTION
TRANSCRIPT
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A. Leão Rodrigues
Faculty of Science and Technology of Nova University of Lisbon
March 2008
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Wave energy is the capacity of the waves for doing work. It is a renewable energy. Ocean waves are generated by the influence of the wind on the ocean surface.
OutlineOutline
• Origin of Sea WavesOrigin of Sea Waves• Sea Wave CharacteristicsSea Wave Characteristics• Power Associated to a Sea WavePower Associated to a Sea Wave• Resource of Wave PowerResource of Wave Power• Types of Wave Power Types of Wave Power
MechanismsMechanisms• Pelamis Energy ConverterPelamis Energy Converter• Wave Energy MarketWave Energy Market• ConclusionsConclusions
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Origin of Sea Origin of Sea WavesWaves
storm
swellwind
wave direction
fetch
Sea waves formation due to a storm
trough
Waves - The combination of forces due to the gravity, sea surface tension and wind intensity are the main factors of origin of sea
waves. Fetch - distance over which the wind excites the waves
To distances far from the fetch, sea waves have a regular shape and the phenomenon is called swell.
Water particle v
v
v
v
Sea Wave
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Sea Wave CharacteristicsSea Wave Characteristics
Tv
crest
crest
trough
H
wavelength - distance between two consecutive crests, or two consecutive troughs
height H - distance crest to trough. It is proportional to wind intensity and its duration.
wave period T - time in seconds needed for the wave travel the wavelength
frequency f = 1/T - indicates the number of waves that appears in a given position.
wave speed –The ratio wavelength/period or v = /T = f.
declivity – the ratio /2H
When this value is greater than 1/7 the wave becomes unstable and vanishes.In deep water, the energy in waves can travel for thousands of miles until that energy is finally dissipated on distant shores.
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Power Associated to a Sea Power Associated to a Sea WaveWave
The power associated with a wave of wavelength and height H and a front b is given by
bgHP 2
2
1
H
b
Power per metre (b = 1 m) of front wave is approximately
When wave height is doubled then generates four times as much power.
20.5 P H T W m
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The world resource of wave power is estimated in about 2 TW.
Resource of Wave Resource of Wave PowerPower
Europe represents about 16% of the global wave power resource (320 GW)
Only about 10 to 15% of the global estimated resource can be converted in electrical energy.
Equator
Global wave power distribution in kW/m
Increased wave activity is found between the latitudes of 30° and 60°
on both hemispheres
mkW THP 25.0
Height (m) Period (s)
A good wave have ~50 kW/m
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A r e a s f o r d e v e l o p m e n t o f w a v e e n e r g y f a r m s :
A r e a s f o r d e v e l o p m e n t o f w a v e e n e r g y f a r m s :
A b o u t 3 3 5 k m o f t h e P o r t u g u e s e w e s t c o a s t l i n e a r e p o t e n t i a l l y a v a i l a b l e t o w a v e e n e r g y u t i l i z a t i o n
R e s t r i c t e d a r e a s o r w i t h e v e n t u a l c o n f l i c t o f u s e s :
5000 MW
Resource of Wave Resource of Wave Power in Power in Portuguese coastPortuguese coast
Povoa do Varzim
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Types of Wave Power Types of Wave Power MechanismsMechanismsThe sea wave’s motion can be converted into
mechanical energy by using proper wave power mechanisms
Shoreline
Nearshore
Offshore
• oscillating column of water
• underwater pneumatic systems
• wave dragon system
• oscillating bodies system.
lying on the bottom of the sea
on sea level.
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oscillating column of water systems
Shoreline mechanisms
Oscillating column of water system
turbine Wells
asynchronous generator
Generator/rectifier air turbine group
air turbine/generator
airflow
breakwater
hydraulic pump
Concrete boxpendulum flap
wave
Pendulum system
converter
Wells turbine
double fed wound rotor induction generator
~
grid
wind
Oscillating column of water – Pico Island, Azores
0,35
0,30
0,25
0,20
0,15
0,100,0 1,0 2,0 3,0 4,0 5,0
Rendimento
Ângulo de calagem das pás
Sem válvula de alívio
Com válvula em paralelo
Com válvula em série
Air output
turbine Wells
Wave
Structure
Parallel valveGenerator Turbine
Series valve
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underwater pneumatic systems
Nearshore
Wave and Roller (USA) 13 Wave and Roller (USA) 13 kWkW
2 MW pneumatic systems 2 MW pneumatic systems (Holand)(Holand)
Archimedes Wave Archimedes Wave SwingSwing
shaft connected to the buoy
Linear Linear generatorgenerator
fixed coil
permanent magnet
Power Buoy (USA) 40 kWPower Buoy (USA) 40 kW
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Offshore mechanisms
Salter’s Duck system
Floating cylinder
oscillating movement converter
electric generator
waves
Escone
sea level
under sea
This converter unit, called Escone, after his inventor Esko Raikano, is the heart of the system and converts the reciprocating motion to a rotating shaft connected direclty to a generator for generating electrical energy with high
efficiency.
Bristol cylinder for wave energy extraction
One of the first methods to extract mechanical energy from the waves was invented in the 1970s by Professor Stephen Salter of the University of Edinburgh, Scotland, in response to the Oil Crisis. It can be moored, to distances of 80 km of the cost. The cam rotates about its axis and is shaped to minimize back-water pressures.
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Pelamis ConverterPelamis Converter
Profile view Top view
Sea snake
Pelamis
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Some aspects of Pelamis Some aspects of Pelamis constructionconstruction
Rolling the steel plate Steel tubes of 3.5 m in diameter
TransportationArticulation
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Pelamis Pelamis layoutlayout
Power module of 250 kVAPower transformer de 950 kVA 6.6/15 kV Three phase cable 15 kV
Three phase cable 15 kV
D/3
T D = 3.5 m
Articulation Power Module
120 m ~
30 m 5 m
Nose P-750
Articulation
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Hydraulic arm
High pressure container
Motor/generator set
Distributor
Reservoir
Vertical articulated axis
Horizontal articulated axis
Power modulePower module
Inside view of the power module
Efficiency = 35 %
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Electric generator
Gas under pressure
HP
Valve 1
Hydraulic motor
Hydraulic arm 1
Hydraulic arm 2
Fluid under pressure
Reservoir
LP
force
force
Valve 2
High pressure
Low pressure
Hydraulic circuitHydraulic circuit
Hydraulic arms
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Pelamis wave energy converter of 750 kW
Wave farm of Aguçadora of 2.25 MW
Association of Pelamis units in a total of 30 MW
(waiting for legislation)
2100 m
600 mof
PelamisPelamisWave direction
Pelamis
Seabed
Anchorage
Pelamis anchorage to the seabed
Flexible cable
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Pelamis installationPelamis installation
Total power = 2.25 MW. (3 units of 750 kW)
15 kV
2001 2002 2003 3 year average
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
150
125
100
75
50
25
0
Wave Seasonal Variability
Ave
rage
inci
dent
pow
er (k
W/m
)
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Costs distribution for a wave power plant
Wave Wave EnergyEnergy MarketMarket
mechanical and electrical equipment
49%
structures
27%
assemblage
13%
grid connectionproject management
2%
5%
anchorage
4%
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ConclusionsConclusions Wave energy is not expensive to operate and maintain, no fuel is needed
and no waste is produced. However, it depends on the intensity of the waves and needs a suitable site where waves are consistently strong. The infrastructure must be able to withstand very rough weather.
Wave power lies not in huge plants but in a combination of on-shore generation and near-shore generation (using a different technology) focused on meeting local or regional needs. If this system prove to be economically possible, only 0.1% of the renewable energy within the world's oceans could supply more than five times the global demand for energy.
The Pelamis Wave Energy Converter is a revolutionary concept resulting from many years of engineering development. It was the world’s first commercial scale machine to generate electrical energy into the grid from offshore wave energy and the first to be used in commercial wave park projects. In Portugal, Pelamis System is now proving to be successful.