This document reviews various technologies for capturing energy from ocean waves. It describes how wave energy is stored as potential and kinetic energy and can be transported over long distances. Various devices are classified based on their working principles, including oscillating water columns, oscillating bodies, and overtopping converters. Examples of specific devices are provided, along with descriptions of air turbine, hydraulic, and electrical power take-off systems. The conclusion states that while progress has been made in modeling wave energy converters, more information is still needed on mooring systems, and large-scale testing is required to support development of these technologies.

1. Giorgio Lippi 77778
Marco Mori 77776
António Falcão
2013-2014
Mechanical Engineering

2. CONTENTS:
 WAVE ENERGIES
 MODELING
 DEVICES
 POWER EQUIPMENT
2
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

3. The energy from ocean waves is the most conspicuous form of ocean energy
about twice the global
electricity supply in
2008 (16,800 TWh/yr or
54 EJ/yr)
Total theoretical wave energy estimated potential: 32,000 TWh/yr (115 EJ/yr)
Data in open sea:
As the waves propagate into the shore,
they are modified in a complex way by
bottom effects and by sheltering due to
the presence of land
The wave energy is related to the wind. When the wind blows over the ocean,
air-sea interaction transfers some of the wind energy to the water, forming
waves, which store this energy as:
• POTENTIAL ENERGY
mass of water displaced from
the mean sea level
• KINETIC ENERGY
motion of water particles
3
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

4. The wave energy level is usually expressed as power per unit length along the wave crest or along the shoreline direction;
typical values for ‘‘good’’ offshore locations (annual average) range between 30 and 80 kW/m and occur mostly in
moderate to high latitudes.
Seasonal variations are in general
considerably larger in the
northern than in the southern
hemisphere, which makes the
southern coasts of South
America, Africa and Australia
particularly attractive for wave
energy exploitation.
Waves are very efficient at
transferring energy, and can
travel long distances over
the ocean
4
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

5. 𝐸 =
1
8𝜋
𝜌𝑔2 𝐴𝑤2 𝑇 𝑊 𝑚
Energy flux in deep water:
5
E is the wave energy flux per unit crest length
Aw is the wave amplitude
T is the wave period
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

6. 𝑚 + 𝐴 𝜔 ∙ 𝑥 = 𝑓𝑑 − 𝐵 𝜔 𝑥 −𝜌𝑔𝑆𝑥 + 𝑓𝑃𝑇𝑂
1 Freedom degree oscillating body with linear PTO:
𝑓𝑑 is the vertical component of the excitation force acting
on the assumedly fixed body
6
Oscillating body
𝐵 𝜔 is the radiation damping coefficient (accounting for the
damping on the body due to energy transfer to waves
radiated away)
𝐴 𝜔 is the hydrodynamic coefficient of added mass
accounting for the inertia of the water surrounding the
body
is the cross-sectional area of the body by the
unperturbed free surface plane 𝜌𝑔𝑆𝑥 is the
hydrostatic restoring force
𝑆
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

7. 𝑚 + 𝐴 𝜔 ∙ 𝑥 = 𝑓𝑑 − 𝐵 𝜔 𝑥 −𝜌𝑔𝑆𝑥 + 𝑓𝑃𝑇𝑂
PTO
𝑓𝑃𝑇𝑂 = −𝐶 𝑥 − 𝐾𝑥
PTO damper coefficient C
PTO spring stiffness K
7
1 Freedom degree oscillating body with linear PTO:
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

8. 𝑚 + 𝐴 𝜔 ∙ 𝑥 = 𝑓𝑑 − 𝐵 𝜔 𝑥 −𝜌𝑔𝑆𝑥 − 𝐶 𝑥 − 𝑘𝑥
𝑋 =
𝐹𝑑
−𝜔2 𝑚 + 𝐴 𝜔 + 𝑖𝜔 𝐵 + 𝐶 + 𝜌𝑔𝑆 + 𝑘
𝜔 =
𝜌𝑔𝑆 + 𝑘
𝑚 + 𝐴 𝜔
1
2
𝐶 = 𝐵 𝜔
Resonance
PTO damping=Radiation damping
8
Energy convertion limit
𝐿 𝑀𝐴𝑋 =
𝑃 𝑀𝐴𝑋
𝐸
=
𝜆
2𝜋
𝐿 =
𝑃
𝐸
= 𝑐𝑎𝑝𝑡𝑢𝑟𝑒 =
𝑃 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑
𝐸𝑛 𝐷𝑖𝑠𝑝
𝑃 𝑀𝐴𝑋 =
1
8𝐵
𝐹𝑑
2
1 Freedom degree oscillating body with linear PTO:
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

9. 𝑚 + 𝐴 𝜔 ∙ 𝑥 = 𝑓𝑑 − 𝐵 𝜔 𝑥 −𝜌𝑔𝑆𝑥 − 𝐶 𝑥 − 𝑘𝑥
9
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Solution: 1-D, linear PTO, No spring
c
c
C Function of device dimension
𝐴 𝜔 𝐵 𝜔 Function of wave period (𝜔=1/T)
• Device’s Energy convertion depends on itself dimensions
• Devices behaviour is selective on waves period
1 Freedom degree oscillating body with linear PTO:
Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

10. Wave energy conversion Technologies
Presently there are many different technology options because the convergence has not yet occurred.
One of the methods that is been used to classify the different system is based on the working principle
Oscillating water column
(air turbine)
Oscillating bodies
(hydraulic motor. Turbine, linear
electrical generator)
Overtopping
(low-head hydraulic turbine)
Fixed structure
Floating
Fixed structure
Floating
Submerged
Floating structure
Heaving Buoys
Rotational Joints
Essentially translation (heave)
Rotation (bottom-hinged)
Non–Concentrating Breakwater
Concentrating Breakwater
Isolated
In Breakwater
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
10Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

11. Oscillating Water Column (OWC)
• Fixed structure (Pico,Limpet) • Floating (Sakata, Mutriku)
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
11Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

12. Oscillating Body systems
One body: Two bodies:
• Heaving bodies (Acqua Buoy, FO3, Wavebob,
Power Buoy)
• Fully submerged (Archimede wave swing)
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
12Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

13. CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Oscillating Body systems
• Pitching bodies - Pelamis • Pitching bodies - Searev
13Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

14. CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Oscillating Body systems
has a surface piercing flap that spans the
whole water depth and the fluid is sea water
powering a Pelton turbine located onshore
totally submerged and uses oil as
working fluid
• Bottom-hinged systems - The Oyster • Bottom-hinged systems - Wave Roller
14Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

15. CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Overtopping converters (with concentration)
• Fixed structure (Tapchan, SSG) • Floating (Wave Dragon)
15Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

16. Power take off systems: AIR TURBINES
Conventional turbines are not appropriate for reciprocating flows, and so
new types of turbines had to be devised and developed.
WELLS TURBINE SELF-RECTIFYING IMPULSE TURBINE DENNIS AULD TURBINE
CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
16
Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

17. CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Power take off systems: HYDRAULIC
HYDRAULIC TURBINE HIGH PRESSURE OIL HYDRAULIC PTO
17Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

18. CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Electrical Conversion:
Rotating electrical generator driven by a
mechanical machine
Linear electrical generator: the generator consists of a
stator and a translator (rather than a rotor).
18Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori

19. CONTENTS
WAVE
ENERGIES
MODELING DEVICES CONCLUSIONS
Conclusion:
1. The present situation shows a wide variety of wave energy systems, without it being clear which types will
be the final winners.
2. Although substantial progress has been achieved in the theoretical and numerical modeling of wave
energy converters
3. Less information seems to be available about mooring: effect of mooring a is non-linear and quite complex
dynamic problem, but of main importance for its role in energy absorption properties of devices.
4. Wave energy systems developping need substantial financial support from governments, plants are to be
tested in the open ocean and they must be large structures, because of the risonance effects. Mostly Europe is
moving in that direction, but , in the last few years, interest in wave energy utilization has been growing rapidly
also in other parts of the world.
19Renewable Energies - Wave energy utilization: A review of the technologies – Giorgio Lippi, Marco Mori