This is my group researching assignment presentation as mini project of Renewable Energy subject.

1. Institute of Technology of Cambodia
Department Electrical and Energy Engineering
Topic: Wave power
Lecturer: ETH Oudaya
Students:
VORN Rithy e20120795
YA Phalkun e20140873
YAV Leakhena e20140874
YORN Thort e20120815

2. ContentI. Introduction
II. History
III. Resource
IV. Variability
V. Wave Motion
VI. The Velocity of Ocean Waves
VII. Wave energy and power
VIII. Ocean Wave Energy Technology
IX. About Pelamis
X. Case study
XI. Advantages and disadvantages of Wave power
XII. Conclusion
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3. II. Introduction
 Wave energy or wave power is essentially power drawn from waves. When wind
blows across the sea surface, it transfers the energy to the waves.
 They are powerful source of energy and the energy output is measured by wave
speed, wave height, length of wave and water density
 The more strong the waves, the more capable it is to produce power. The
captured energy can then be used for electricity generation.
 Successful and profitable use of wave energy on a large scale only occurs in a
few regions around the world. The places include the states of Washington,
Oregon and California and other areas along North America’s west coast. This
also includes the coasts of Scotland Africa and Australia.
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4. I. History
 The first known patent to use energy from ocean waves dates back to 1799, and
was filed in Paris by Girard and his son.An early application of wave power was a
device constructed around 1910 by Bochaux-Praceique to light and power his
house at Royan, near Bordeaux in France.
 Modern scientific pursuit of wave energy was pioneered by Yoshio Masuda's
experiments in the 1940s. He has tested various concepts of wave-energy devices at
sea. Among these was the concept of extracting power from the angular motion at
the joints of an articulated raft, which was proposed in the 1950s by Masuda.
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5. 5

6. III. Resource
 The passage of wind over the surface of the sea results in the gradual transfer of
energy into the water to produce waves. When wind blows across the surface of
the water strongly enough it creates waves.
 Wind power typically has densities in the range 1.2 – 1.8 kW/ . Waves with a
typical power density of 50 kW per meter of wave front or crest length.
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7. IV. Variabilities
 The wave resource, not unlike the wind resource on which it depends, also varies
on a day - to - day and season - by - season basis; in general wave conditions are
more energetic in the winter than in the summer.
 For example, about half of the annual wave power at all UK sites occurs during
the winter months of December, January and February, as shown in Figure 2.22.
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8. Figure 07: Average monthly wave power in the UK. Average monthly wind power
capacity factor [15] is shown for reference purposes. (Reproduced from Sinden,
G.E., 2007, DPhil Thesis with permission of Environmental Change Institute,
Oxford University Centre for the Environment).
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9. V. Wave motion
The circular particle motion has an amplitude that decreases exponentially with depth
and becomes negligible for D< /2.
1). The surface waves are sets of unbroken sine waves of irregular wavelength, phase
and direction.
2). The amplitudes of the water particle motions decrease exponentially with depth. At a
depth of below the mean surface position, the amplitude is reduced to 1/e of the surface
amplitude (e = 2.72, base of natural logarithms). At depths of the motion is negligible,
being less than 5% of the surface motion.
3). The amplitude a of the surface wave is essentially independent of the wave length ,
velocity C or period T of the wave, and depends on the history of the wind regimes above
the surface. It is rare for the amplitude to exceed one-tenth of the wavelength.
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10. Figure 08: Particle motion in water waves. (a) Deep water, circular motion of water
particles. (b) Shallow water, elliptical motion of water particles.
A particle of water in the surface has a circular motion of radius a equal to the
amplitude of the wave. The wave height H from the top of a crest to the bottom of a
trough is twice the amplitude: H = 2a. The angular velocity of the water particles is
(radian per second).
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11. Figure 09: Wave characteristics.
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12. Figure 10: Water surface perpendicular to resultant of gravitational and
centrifugal force acting on an element of water, mass m.
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13. Figure 11: Resultant forces on surface particules.
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14. Figure 12: Accelerations and velocities of a surface water particle. (a)
Water surface.
(b) Particle acceleration, general derivation. (c) Particle velocity.
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15. The surface motion is that of a travelling wave
Period of the motion
The velocity of a particle at the crest of the wave
The wave surface velocity in the x direction
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16. VI. The Velocity of Ocean Waves
d :The depth of the water.
g : The acceleration of gravity, 9.81 m/s2.
h: The height of the wave—the vertical distance between the through and the crest
of a wave.
T : The period the time interval between two successive wave crests at a fixed point.
v : The phase velocity of the wave—the ratio between the wavelength and the
period.
λ: The wavelength the horizontal distance between two successive wave crests,
measured along the direction of propagation.
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17. Deep water , thus the wave velocity
Shallow water , thus the wave velocity
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18. VII. Wave energy and power
a) Basic
The elementary theory of deep water waves begins by
considering a single regular wave. The particles of water
near the surface will move in circular orbits, at varying
phase, in the direction of propagation x.
Figure 13: Elemental motion of water, drawn to show the exponential
decrease of amplitude with depth.
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19. • The kinetic energy per unit width of wave front per unit of wave
• Potential energy per unit width of wave per unit length
• The total energy per unit width per unit length of wave front, i.e. total energy per
unit area of surface
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20. Figure14: Local pressure fluctuations in the wave. (a) Pressures in the
wave. (b) Local displacement of water particle.
b) Power extraction from waves
The energy is associated with water that remains at the same location
when averaged overtime
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21. The power carried in the wave at x, per unit width of wave-front at any
instant, is given by
The power carried forward in the wave per unit width across the wave front.
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22. Wave technologies have been designed to be installed in the nearshore,
offshore, and far offshore locations.
While wave energy technologies are intended to be installed at or near the
water's surface, there can be major differences in their technical concept
and design.
VII. Ocean Wave Energy Technologies
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23. VII. Ocean Wave Energy Technologies
 Point absorbers
 Attenuators
 Overtopping devices
 Terminators.
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24. VII. Ocean Wave Energy Technologies
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25. VII. Ocean Wave Energy Technologies
 Terminator Devices
 The wave motion inside the chamber
alternately compresses and decompresses the
air that exists above the water level inside the
chamber.
 As a result, an alternating stream of high-
velocity air is generated.
 This airflow is driven through a duct to a
turbine generator that is used to generate
electricity.
 The energy generating capacity of a single
terminator device can be up to 1.5 MW.
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26. VII. Ocean Wave Energy Technologies
 Terminator Devices
26

27. The Oscillating Water Column (OWC) generates
electricity in a two step process.
As a wave enters the column, it forces the air in the
column past a turbine and increases the pressure within
the column.
As the wave retreats, the air is drawn back past the
turbine due to the reduced air pressure on the ocean
side of the turbine.
Irrespective of the airflow direction, the turbine
(referred to as a Wells turbine, after its inventor) turns
in the same direction and drives a generator to produce
electricity.
VII. Ocean Wave Energy Technologies
 Terminator Devices
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28. VII. Ocean Wave Energy Technologies
Attenuators
 The segments flex at hinged joints as a
wave passes along the device. The
mechanical motion of the flexing is
converted to electrical energy using
hydraulic motors and generators.
 The electrical energy is fed down a
single umbilical cable to a junction on
the seabed.
 Several devices can be connected
together and linked to shore through a
single underwater transmission cable.
 The energy generating capacity of a
single attenuator device can be up to 1
MW.
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29. VII. Ocean Wave Energy Technologies
 Attenuators
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30.  Each Pelamis has three power module joined by
tubular section.
 Wave causes the modules and tubes to move in
relation to each other.
 This motion is resisted by hydraulic rams in each of
joints.
 The hydraulic rams pump high-pressure oil through
hydraulic motors.
 The hydraulic motors drive electrical generators to
produce electricity.
VII. Ocean Wave Energy Technologies
 Attenuators
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31. VII. Ocean Wave Energy Technologies
 Point Absorbers
 The rise and fall of the wave height at a single
point that caused by passing waves is used to
drive electromechanical or hydraulic energy
converters to generate power.
 This mechanical energy drives an electrical
generator. The electrical energy is fed down a
single umbilical cable to a junction on the seabed.
 Several devices can be connected together and
linked to shore through a single underwater cable.
They can either float or be anchored to the sea
floor.
 An individual point absorber device may produce
up to 11 MW of electricity.
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32. VII. Ocean Wave Energy Technologies
 Point Absorbers
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33. VII. Ocean Wave Energy Technologies
 Overtopping Devices
• Overtopping devices generally are anchored
in open water and consist of reservoirs that
are filled by wave action to levels above the
surrounding sea level.
 The energy generating capacity of a single
overtopping device can be up to 11 MW.
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34. IX. About Pelamis
Pelamis wave power is a
technology that uses the motion
of ocean surface wave to create
electricity developed by the
Scottish company was
established in 1998 and had
office and fabrication facilities
in Leith Docks, Edinburgh,
Scotland.
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35. IX. About Pelamis
 Construction details
• Each Pelamis machine is of
120mts long.
• It has a diameter of 3.5 mts.
• Each Pelamis machine has three
power conversion modules.
• Each machine is rated to produce
750KW
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36. IX. About Pelamis
 Production of Pelamis
PCM
Steel
Tube
nose
Assembly
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37. IX. About Pelamis
37

38. IX. About Pelamis
 Operation of Pelamis wave power
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39. IX. About Pelamis
 How does it work?
• The Buoyant Moored Device works by rotating
about a long linkage
• The Oscillation Water Column, water work a
piston to pumps air and drive a turbine to generate
power
• Machine floats on the surface of the water. The
structure is secured by flexile cable fitted to the
seabed 39

40. IX. About Pelamis
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41.  Electrical cable
• Submersible ower cables
are vulnerable to damage
and need to be buries
into soft sediments on
the ocean floor.
• XLPE insulations have
proven to be an excellent
alternative having no
such potential hazards
associated with its
operation.
IX. About Pelamis
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42. IX. About Pelamis
 Wave energy Market
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43. X. Case Study
Project Name Okeanós: Pelamis wave energy farm Portugal
Project Three P1-A Pelamis machines
Location Aguçadoura/ Póvoa de Varzim, Northern Portugal
Installed capacity 3 * 750 kW = 2.25 MW; plans exist to extend to 30
devices (22.5 MW)
Technology Type Pelamis: Floating articulated attenuator
Project Type/Phase Commercial contract
Year Construction of devices terminated in 2006, later
assembly and partly testing by early 2008; installation
summer 2008
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44. XI. Advantages and disadvantages
Advantages
1) Renewable
2) Environment Friendly
3) Easily Predictable
4) Less Dependency on
Foreign Oil Cos
5) No Damage to Land
Disadvantages
1)Suitable to Certain Locations
2)Wave length
3)Noise and Visual
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45. VII. Conclusion
• No land requirement
• Invest installation
• Run low operation cost
• Product electricity 24 h per day
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