The document summarizes various wave power conversion systems for producing electrical energy from sea waves. It describes how sea waves are formed and quantifies the power associated with waves. Several devices are then described that extract mechanical energy from waves including oscillating water columns, the Pelamis system, and the Wave Dragon system. The Pelamis system is discussed in more detail, as it consists of articulated cylinders that move with waves to pump hydraulic fluid and drive electric generators. The document concludes that wave power could make a major contribution to renewable energy production.
WIND POWER GENERATION SCHEMES are Constant speed - Constant frequency systems (CSCF)
Variable speed - Constant frequency systems (VSCF)
Variable speed - Variable frequency systems (VSVF)
WIND POWER GENERATION SCHEMES are Constant speed - Constant frequency systems (CSCF)
Variable speed - Constant frequency systems (VSCF)
Variable speed - Variable frequency systems (VSVF)
The aim of this paper is to analyze the performance of the three-phase squirrel cage induction motor under various voltage fluctuation levels. Generally, Induction motor drives are preferred for its simple and easy control. Their performance depends on relative power supply quality such as voltage sag, harmonics, voltage unbalance and voltage fluctuations. The induction motor is more sensitive to voltage fluctuations within certain amplitude levels and frequencies. This paper presents a study of voltage sag effects on an induction motor using simulation. In this paper, the impact of voltage fluctuations on induction motor performance is investigated. S. Sakthivel"Effect of Voltage Sag on an Induction Motor" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-5 , August 2018, URL: http://www.ijtsrd.com/papers/ijtsrd18298.pdf http://www.ijtsrd.com/engineering/electrical-engineering/18298/effect-of-voltage-sag-on-an-induction-motor/s-sakthivel
There are three basic ways to tap the ocean for its energy. We can use
The ocean's waves.
The ocean's high and low tides .
Temperature differences in the water.
1-Wave Energy
Kinetic energy (movement) exists in the moving waves of the ocean. That energy can be used to power a turbine. The wave rises into a chamber. The rising water forces the air out of the chamber. The moving air spins a turbine which can turn a generator.
When the wave goes down, air flows through the turbine and back into the chamber through doors that are normally closed.
2-Tidal Energy
Two types of tidal plant facilities.
Tidal barrages
Tidal stream generator
pq and facts Power Quality problems in distribution systems:
Transient and Steady state variations in voltage and frequency. Unbalance, Sags, Swells, Interruptions,
Wave-form Distortions: harmonics, noise, notching, dc-offsets, fluctuations. Flicker and its
measurement
Sea waves have high energy densities, the highest among renewable energy sources with the natural seasonal variability of wave energy following the electricity demand in temperate climates securing energy supplies in remote regions.
it provides the overview about compresses air energy storage with a method used to store electrical energy when it is surplus and release energy back to the system during peak demand.
This is a slide collection made for educational purposes as part of the EU Leonardo pilot project 1860 Alter ECO in 1999.
Authors: Johannes Falnes and Jørgen Hals Todalshaug
The aim of this paper is to analyze the performance of the three-phase squirrel cage induction motor under various voltage fluctuation levels. Generally, Induction motor drives are preferred for its simple and easy control. Their performance depends on relative power supply quality such as voltage sag, harmonics, voltage unbalance and voltage fluctuations. The induction motor is more sensitive to voltage fluctuations within certain amplitude levels and frequencies. This paper presents a study of voltage sag effects on an induction motor using simulation. In this paper, the impact of voltage fluctuations on induction motor performance is investigated. S. Sakthivel"Effect of Voltage Sag on an Induction Motor" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-5 , August 2018, URL: http://www.ijtsrd.com/papers/ijtsrd18298.pdf http://www.ijtsrd.com/engineering/electrical-engineering/18298/effect-of-voltage-sag-on-an-induction-motor/s-sakthivel
There are three basic ways to tap the ocean for its energy. We can use
The ocean's waves.
The ocean's high and low tides .
Temperature differences in the water.
1-Wave Energy
Kinetic energy (movement) exists in the moving waves of the ocean. That energy can be used to power a turbine. The wave rises into a chamber. The rising water forces the air out of the chamber. The moving air spins a turbine which can turn a generator.
When the wave goes down, air flows through the turbine and back into the chamber through doors that are normally closed.
2-Tidal Energy
Two types of tidal plant facilities.
Tidal barrages
Tidal stream generator
pq and facts Power Quality problems in distribution systems:
Transient and Steady state variations in voltage and frequency. Unbalance, Sags, Swells, Interruptions,
Wave-form Distortions: harmonics, noise, notching, dc-offsets, fluctuations. Flicker and its
measurement
Sea waves have high energy densities, the highest among renewable energy sources with the natural seasonal variability of wave energy following the electricity demand in temperate climates securing energy supplies in remote regions.
it provides the overview about compresses air energy storage with a method used to store electrical energy when it is surplus and release energy back to the system during peak demand.
This is a slide collection made for educational purposes as part of the EU Leonardo pilot project 1860 Alter ECO in 1999.
Authors: Johannes Falnes and Jørgen Hals Todalshaug
Tidal energy is produced by the surge of ocean waters during the rise and fall of tides. Tidal energy is a renewable source of energy.
During the 20th century, engineers developed ways to use tidal movement to generate electricity in areas where there is a significant tidal range—the difference in area between high tide and low tide. All methods use special generators to convert tidal energy into electricity.
Tidal energy production is still in its infancy. The amount of power produced so far has been small. There are very few commercial-sized tidal power plants operating in the world. The first was located in La Rance, France. The largest facility is the Sihwa Lake Tidal Power Station in South Korea. The United States has no tidal plants and only a few sites where tidal energy could be produced at a reasonable price. China, France, England, Canada, and Russia have much more potential to use this type of energy.
In the United States, there are legal concerns about underwater land ownership and environmental impact. Investors are not enthusiastic about tidal energy because there is not a strong guarantee that it will make money or benefit consumers. Engineers are working to improve the technology of tidal energy generators to increase the amount of energy they produce, to decrease their impact on the environment, and to find a way to earn a profit for energy companies.
Tidal Energy Generators
There are currently three different ways to get tidal energy: tidal streams, barrages, and tidal lagoons.
For most tidal energy generators, turbines are placed in tidal streams. A tidal stream is a fast-flowing body of water created by tides. A turbine is a machine that takes energy from a flow of fluid. That fluid can be air (wind) or liquid (water). Because water is much more dense than air, tidal energy is more powerful than wind energy. Unlike wind, tides are predictable and stable. Where tidal generators are used, they produce a steady, reliable stream of electricity.
Placing turbines in tidal streams is complex, because the machines are large and disrupt the tide they are trying to harness. The environmental impact could be severe, depending on the size of the turbine and the site of the tidal stream. Turbines are most effective in shallow water. This produces more energy and allows ships to navigate around the turbines. A tidal generator's turbine blades also turn slowly, which helps marine life avoid getting caught in the system.
The world's first tidal power station was constructed in 2007 at Strangford Lough in Northern Ireland. The turbines are placed in a narrow strait between the Strangford Lough inlet and the Irish Sea. The tide can move at 4 meters (13 feet) per second across the strait.
Barrage
Another type of tidal energy generator uses a large dam called a barrage. With a barrage, water can spill over the top or through turbines in the dam because the dam is low. Barrages can be constructed across tidal rivers, bays, and estuaries.
Ocean and Wave Energy or Ocean Power ConversionTechnologiesTesfaye Birara
Energy conversion is the process of changing one form of energy into another, a fundamental capability that enables modern civilization to function. It can occur in various ways, from converting the kinetic energy of wind into mechanical power through windmills to transforming solar energy into electrical energy in solar panels. This transformation is essential not just for daily usage but also for harnessing and utilizing natural resources more efficiently. In the context of rural electrification, this process plays a critical role. By converting available local energy resources into electricity, rural communities can access a stable and reliable power supply. This not only improves the quality of life but also supports economic development by powering homes, schools, businesses, and healthcare facilities. Consequently, energy conversion facilitates the broader goal of rural electrification, demonstrating the interconnection between technological innovation and societal advancement.
one among the energy generation plan for future using speedy automobiles. The new way of renewable energy generation. Designed to extract power through engineering ocean technology in land.
Review of journal articles of wave energy converters and their impact on powe...Nuwan Dinusha
Ocean waves are a huge, large untapped energy source, which is a considerable renewable energy source that can generate the useable energy forms. This review introduce the general status of wave energy and evaluate the device types that represent current wave energy converter (WEC) technology which defer according to the location, type and the modes of operation, power take off (PTO) methods Benefits and the challenges that have to face during the ocean wave power generation. Ocean wave energy power can contribute to the Sri Lanka power crisis. Wave climate and geographical construction around the country and best places to establish the wave energy power plant in the Sri Lanka and available technologies. Social and environmental impact of wave power plant.
Model of Ocean Wave Energy Converter Based on Water Mass Gravity Force as a R...AM Publications
The aim of this study was to develop a model of ocean wave energy converter based on water mass gravity force (WEC-WGF) to overcome the flaws of existing wave energy converter that rely on water buoyancy force. This paper presented physical model experiment result of wave energy converter based on water mass gravity force. The harvested energy were compared with calculated theoretical energy based on linear wave theory. The physical model investigation was carried out at wave simulator (flume) in Hydraulics Laboratory Department of Civil Engineering, Hasanuddin University Indonesia on February - March 2016. The physical model consists of a series of one-way gear connected with plastic container as an interface between converter and regular generated wave. Investigation was carried out to observe the influence of gravity weight mass and wave height variations on converters harvested power. The experiment result indicated that the amount of converter Power Take Off (PTO) were strongly influenced by variation of gravity weight mass (Mgw), followed by wave height (H) and wave period (T) respectively. These results outperform the calculated power by means of linear wave theory. The result of this experiment could be used as a reference to develop theoretical or analytical model of wave energy converter based on water mass gravity force.
This report discusses the potential contribution that energy derived from the tides and waves can make to overall energy supply in a sustainable way. It covers the topics of wide range like how tides and waves are formed; functions of the possible and popular power generation systems especially tidal barrages,turbines, oscillating water columns and wave farms. Advantages and disadvantages of tidal and wave energy are also briefly discussed. Some cost data’s used give us brief insight into the economic prospects of the tidal and wave energy. By turning to potential along the Indian coastline, we found that India do have a huge potential of tidal and wave energy, though it has started very late. Government
initiatives and extensive research focused on the mentioned relevant opportunities will surely change the energy scenario.
A wave-to-wire model of ocean wave energy conversion system using MATLAB/Simu...Jakir Hossain
Renewable energy sources, unlike the conventional combustible fuels, are naturally distributed and extensively available in a boundless manner all over the world in different forms. Here, in this paper, authors elucidate the scopes and opportunities of the ocean wave to develop a low-cost, environmental friendly, and sustainable electrical power generation system. At the present time most technological modernizations aimed at exploiting such resources are at early stage of development, with only a handful of devices close to be at the commercial demonstration stage. None of them, though, operates converting the wave energy contents at its very origin: the orbital motion of water particles right below the ocean surface. The Sea spoon device catches the kinetic energy of ocean waves with favorable conversion proficiency, according to specific "wave-motion climate". In this letter, authors illustrate a possible methodology of converting this naturally exorbitant energy with efficient conversion methodology and simulating the conversion environment with MATLAB/Simulink platform.
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
PHP Frameworks: I want to break free (IPC Berlin 2024)Ralf Eggert
In this presentation, we examine the challenges and limitations of relying too heavily on PHP frameworks in web development. We discuss the history of PHP and its frameworks to understand how this dependence has evolved. The focus will be on providing concrete tips and strategies to reduce reliance on these frameworks, based on real-world examples and practical considerations. The goal is to equip developers with the skills and knowledge to create more flexible and future-proof web applications. We'll explore the importance of maintaining autonomy in a rapidly changing tech landscape and how to make informed decisions in PHP development.
This talk is aimed at encouraging a more independent approach to using PHP frameworks, moving towards a more flexible and future-proof approach to PHP development.
JMeter webinar - integration with InfluxDB and GrafanaRTTS
Watch this recorded webinar about real-time monitoring of application performance. See how to integrate Apache JMeter, the open-source leader in performance testing, with InfluxDB, the open-source time-series database, and Grafana, the open-source analytics and visualization application.
In this webinar, we will review the benefits of leveraging InfluxDB and Grafana when executing load tests and demonstrate how these tools are used to visualize performance metrics.
Length: 30 minutes
Session Overview
-------------------------------------------
During this webinar, we will cover the following topics while demonstrating the integrations of JMeter, InfluxDB and Grafana:
- What out-of-the-box solutions are available for real-time monitoring JMeter tests?
- What are the benefits of integrating InfluxDB and Grafana into the load testing stack?
- Which features are provided by Grafana?
- Demonstration of InfluxDB and Grafana using a practice web application
To view the webinar recording, go to:
https://www.rttsweb.com/jmeter-integration-webinar
UiPath Test Automation using UiPath Test Suite series, part 4DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 4. In this session, we will cover Test Manager overview along with SAP heatmap.
The UiPath Test Manager overview with SAP heatmap webinar offers a concise yet comprehensive exploration of the role of a Test Manager within SAP environments, coupled with the utilization of heatmaps for effective testing strategies.
Participants will gain insights into the responsibilities, challenges, and best practices associated with test management in SAP projects. Additionally, the webinar delves into the significance of heatmaps as a visual aid for identifying testing priorities, areas of risk, and resource allocation within SAP landscapes. Through this session, attendees can expect to enhance their understanding of test management principles while learning practical approaches to optimize testing processes in SAP environments using heatmap visualization techniques
What will you get from this session?
1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
Topics covered:
Execution from the test manager
Orchestrator execution result
Defect reporting
SAP heatmap example with demo
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
91mobiles recently conducted a Smart TV Buyer Insights Survey in which we asked over 3,000 respondents about the TV they own, aspects they look at on a new TV, and their TV buying preferences.
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
DevOps and Testing slides at DASA ConnectKari Kakkonen
My and Rik Marselis slides at 30.5.2024 DASA Connect conference. We discuss about what is testing, then what is agile testing and finally what is Testing in DevOps. Finally we had lovely workshop with the participants trying to find out different ways to think about quality and testing in different parts of the DevOps infinity loop.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
To Graph or Not to Graph Knowledge Graph Architectures and LLMs
Wave energy
1. Wave power conversion systems for electrical energy production
Leão Rodrigues
Department of Electrical Engineering
Faculty of Science and Technology
Nova University of Lisbon
2829-516 Caparica - PORTUGAL
e-mail: leao@uninova.pt Teleph: +351 212948545
Abstract. Due to economic social cohesion, the European
Union is promoting to improve the production of electrical
energy from renewable energy sources. Sea waves have
associated a form of renewable energy which can be captured
by using a hydro mechanical device that in turn drives an
electrical generator to produce electrical energy.
After a brief description of wave formation and quantifying the
power across each meter of wave front associated to the wave,
the paper describes several devices used presently to extract
mechanical energy from the waves and their advantages and
disadvantages are presented as conclusions. In particular, the
modern Pelamis system is described in some detail.
Wave energy market is also discussed.
Sea Waves Formation
2.
The combination of forces due to the gravity, sea surface
tension and wind intensity are the main factors of origin
of sea waves. Figure 1 illustrates the formation of sea
waves by a storm. Wave size is determined by wind
speed and fetch (the distance over which the wind excites
the waves) and by the depth and topography of the
seabed (which can focus or disperse the energy of the
waves). To distances far from the fetch, sea waves have a
regular shape and the phenomenon is called swell
.
Key words
wind
storm
swell
Wave Power; Devices to convert wave energy; Pelamis
wave energy converter; Wave energy market.
wave
direction
fetch
1. Introduction
Wave power refers to the energy of ocean surface waves
and the capture of that energy to do useful work. Sea
waves are a very promising energy carrier among
renewable power sources, since they are able to manifest
an enormous amount of energy resources in almost all
geographical regions. The global theoretical energy from
waves corresponds to 8x106 TWh/year, which is about
100 times the total hydroelectricity generation of the
whole planet. To produce this energy using fossil fuels it
would result an emission of 2 millions of tones of CO2.
This means that wave energy could contribute heavily for
the attenuation of pollutant gases in the atmosphere, as
defended by the Kyoto Protocol.
The global wave resource due to wave energy is roughly
2 TW and Europe represents about 320 GW, which is
about 16% of the total resource. However, for various
reasons, it is estimated that only 10 to 15% can be
converted into electrical energy, which is a vast source of
energy, able to feed the present all world.
Eventually, wave energy could make a major
contribution by yielding as much as 120 TWh/year for
Europe and perhaps three times that level worldwide. The
ocean is a true store of renewable energy.
Fig. 1. Sea waves formation due to a storm
The water particles excited by the wind have in each
location of the ocean circular trajectories with highest
diameter at the surface and diminishing exponentially
with depth. The conjugation of this circular motion is
responsible for the wave formation and respective
propagation, as shown in figure 2.
crest
λ
crest
wave direction propagation
v = λf.
H
trough
λ/2
Fig. 2. Propagation of sea waves
2. The distance between two consecutive crests, or two
consecutive troughs, defines the wavelength λ. Wave
height H (crest to trough) is proportional to wind
intensity and its duration.
The wave period T (crest to crest) is the time in seconds
needed for the wave travelers the wavelength λ and is
proportional to sea depth. The frequency f = 1/T indicates
the number of waves that appears in a given position.
Consequently the wave speed is v = λ/T = λ/f. The ratio
λ/2H is called the wave declivity and when this value is
greater than 1/7 can be proved that the wave becomes
unstable and vanishes.
Longer period waves have relatively longer wavelengths
and move faster. Generally, large waves are more
powerful.
3. Power Associated to a Sea Wave
Ocean waves transport mechanical energy. The power
associated with a wave of wavelength λ and height H and
a front b is given by
1
(1)
P = ρgH 2 λb
2
where ρ is the water specific weight and g is the gravity
acceleration. The power across each meter of wave front
associated to an uniform wave with height H (m) and
wavelength λ (m) is then
Pu =
P 1
= ρ gH 2 λ
b 2
(2)
and is expressed in W/m.
During a “tsunami”, waves far from the beach have long
wavelength λ1 a small height H1 but great power. When
the waves propagate into the beach the power is kept
almost constant (neglecting friction) and the wavelength
decreases to λ2. Therefore, Eq. (2) shows that the height
2
of the wave must increases to square H2 in order to
maintain Pu constant, as illustrated in figure 3. These big
waves have devastated effects on the beach!
λ2
λ1
H2
H1
ocean
beach
seabed
Fig.3 Formation of a “tsunami”
For irregular waves of height H (m) and period T (s), an
equation for power per unit of wave front can be derived
as
(3)
Pi ≅ 0 .42 H 2 T
and is expressed in kilowatts per meter (kW/m) of wave
front. It is significant to note that wave power varies with
the square of wave height. Then, when wave height is
doubled generates four times as much power [1].
Excluding waves created by major storms, the largest
waves are about 15 meters high and have a period of
about 15 seconds. According to the Eq.(3), such waves
carry about 1700 kilowatts of potential power across each
meter of wave front. A good wave power location will
have an average flux much less than this, perhaps about
50 kW/m. The Atlantic waves along northwest cost have
an average value o 40 kW/m.
4. World Resource of Wave Power
Wave energy is unevenly distributed over the globe.
Figure 4 shows an Atlas of the global power density
distribution of the oceans where the numbers indicate
kW/m. The north and south temperature zones have the
best sites for capturing wave power. The prevailing
winds in these zones blow strongest in winter. Increased
wave activity is found between the latitudes of 30° and
60° on both hemispheres, induced by the prevailing
western winds blowing in these regions
Equator
Fig.4 Global wave power distribution in kW/m
The oceanic wave climate (i.e. far offshore) offers
enormous levels of energy. As waves approach the
shore, energy is dissipated, leading to lower wave power
levels on the shoreline. Therefore, the energy availability
is sensitive to location and the distance from the
shoreline.
5. Types of Wave Power Mechanisms
The sea wave’s motion can be converted into mechanical
energy by using proper wave power mechanisms. There
are currently about 40 types of mechanisms for exploiting
the energy available in waves, several of which are now
being constructed. These devices are generally
categorized by location installed and power take-off
system.
Locations are shoreline, nearshore and offshore. Power
take-off systems can be oscillating column of water,
underwater pneumatic systems, wave dragon system and
oscillating bodies system. Also these mechanisms can be
lying on the bottom of the sea, on the shoreline and on
sea level.
Description of these systems is following presented.
3. •
A prototype of 40 kW using an asynchronous generator
was installed in Pico Island, Azores, Portugal, and an
optimal overall efficiency of 35 % was claimed [2,3,4].
Shoreline Locations
A Oscillating Water Column
converter
This system consists of a chamber built in shoreline cost
with the layout shown in figure 5. The motions of
ocean/sea waves push an air pocket up and down behind
a breakwater. Then the air passes through an air turbine.
Next, when the wave returns to the sea, an air depression
will circulate through the turbine in the opposite sense.
However, this turbine has been designed to continue
turning the same way irrespective of the direction of the
airflow.
Wells
turbine
grid
~
wind
double fed wound rotor
induction generator
air turbine/generator
Fig. 7 Wound induction generator variable speed diagram
airflow
The problem with this pneumatic system is that the
rushing air can be very noisy, unless a silencer is fitted to
the turbine. But the noise is not a huge problem anyway,
as the waves make quite a bit of noise themselves.
breakwater
B Pendulum System
Fig. 5 Oscillating column of water system
This is a rectifier Wells turbine type, designed by
Professor Alan Wells of Queen's University, which
drives an electric generator mounted on the same shaft, as
illustrated in figure 6. To control the air pressure inside
the camera a valve in parallel (sometimes in series) with
the turbine is used.
The Pendulum system is also installed in the shoreline
and consists of a parallelepiped concrete box, which is
open to the sea at one end, as shown in figure 8.
hydraulic pump
wave
asynchronous
generator
pendulum
flap
Concrete box
Fig.8 Pendulum system
turbine
Wells
Fig. 6 Generator / rectifier air turbine group
The generator delivers power into the grid with constant
frequency and rms voltage. Because the turbine rotates
with a variable speed a synchronous machine is not
appropriate. Instead, a double fed wound rotor induction
generator is used, as shown diagrammatically in figure 7.
The wound rotor is fed by the stator using a converter
and with this arrangement the frequency and voltage is
kept constant for a large range of turbine speed variation.
A pendulum flap is hinged over this opening, so that the
actions of the waves cause it to swing back and forth.
This motion is then used to power a hydraulic pump and
an electric generator.
•
Nearshore Locations
C Offshore Wave Dragon System
Wave Dragon System is a floating slack-moored energy
converter of the overtopping type that can be displayed in
a single unit or in arrays. Groups of 200 Wave Dragon
4. units result in a wave power park with a capacity
comparable to a traditional fossil fuel based power plant.
The Wave Dragon system was the world’s first nearshore
wave energy converter producing power for the grid. The
basic idea of this system consists of two large "arms" that
focus waves up a ramp into a reservoir. The water returns
to the ocean by the force of gravity via a low head hydro
turbine which drives an electric generator. Figure 9
illustrates this principle
overtopping
Fig. 11 Power Buoy
reservoir
above the ocean surface. Using the three-point mooring
system, they are designed to be installed about 8 km
offshore in water 40 to 60 m deep.
turbine outlet
Fig. 9 Wave Dragon System Principle
Wave Dragon is a very simple construction and only the
turbines are the moving parts. This is essential for any
device bound for operating nearshore where the extreme
forces seriously affect any moving parts. In comparison
with traditional hydroelectric power stations, this new
technology is competitive. Figure 10 shows a photograph
of the Wave Dragon system installed nearshore
E Salter’s Duck System
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. A cross section of the Salter
cam (or Duck) is shown in figure 12 and 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.
Fig. 10 Wave Dragon System Installation Nearshore
The Wave Dragon concept combines existing, mature
nearshore and hydro turbine technology in a novel way.
Due to its size service, maintenance and even major
repair works can be carried out at sea leading to low cost
relative to others systems.
•
Offshore Locations
D Power Buoy
This system utilizes the Power Buoy technology which
consists of modular ocean-going buoys, as shown in
figure 11.The rising and falling of the waves moves the
buoy-like structure creating mechanical energy which is
converted into electricity and transmitted to shore by
means a secure, undersea transmission line.
A buoy with 40 kW power has a diameter of 4 m and is
16 m long, with approximately 5 m of the unit rising
Fig. 12 Salter’s Duck system
Conversion of the float movement into electrical energy
is difficult because of the slow oscillations. While it
continues to represent the most efficient use of available
material and wave resources, the machine has never gone
to sea, primarily because its complex hydraulic system is
not well suited to incremental implementation, and the
costs and risks of a full-scale machine would be high.
Most of the prototypes being tested absorb far less of the
available wave power, and as a result their mass/power
ratio remain far away from the theoretical maximum [5].
F Pelamis Wave Energy Converter
The Pelamis Wave Energy Converter, a Scottish
invention, consists of six articulated cylinders of 3.5 m in
diameter and 30 m in length (floaters) articulated
connected to four cylinders of 3.5 m in diameter and 5 m
5. in length (power modules) This articulated structure with
140 m in a total length is placed 2/3 semi-submerged
offshore in deep waters, as shown in figure 13. Due to the
waves, this structure up and down and side to side as a
sea snake (Pelamis in Greek).
Each of these four modules has a 250 kW electric
generator giving a total power of 750 kW for each
Pelamis unit. A 10 kV three phase power transformer is
situated in the front floater and send the electric energy
across underwater power cables to a substation in land.
Figure 16 shows an association of various numbers of
units constituting a wave farm [6].
Fig. 13 Pelamis Wave Energy Converter
The structure is secured by flexile cables fitted to the
seabed. in such way that the float axis is oriented in the
predominant wave direction. Figure 14 shows the
Pelamis structure anchored to the seabed.
Pelamis
wave
direction
flexible
cable
seabed
anchorage
Fig. 14 Pelamis fixation to the seabed
This long, hinged tube as the hinges bend, they pump
hydraulic fluid creating pressurized oil to drive a
hydraulic motor that drives an electric generator,
mounted inside the 5 m floating power module, as shown
in figure 15
Fig. 16 Pelamis wave farm
A wave farm utilizing Pelamis technology was recently
installed in Aguçadora Wave Park, about three miles off
Portugal's northern coast, near Póvoa do Varzim, The
wave farm initially uses three Pelamis P-750 machines
developing a total power of 2.25 MW. Other plans for
wave farms include a 3MW array of four 750 kW
Pelamis devices in the Orkneys, off northern Scotland,
and the 20MW Wave hub development off the north
coast of Cornwall, England.
Only one Pelamis-750 placed on the sea of 55 kW/m
average intensity will produce per year a total energy of
2,2x106kWh. This gives a load factor α of
α =
2 , 2 × 10 6 kWh
= 0 ,34
750 kW ( 365 dias × 24 horas )
Usually other devices for extraction wave energy have
lower load factors, of the order of 0.25. This calculation
shows that the Pelamis system presents a great advantage
for future investments and an amazing breakthrough in
power generation. The system is safe, easy to install, and
not harmful to the environment, although some
legislation has to be published.
.
H Wave Roller System
piston
Fig. 17 Wave Roller plate
Fig. 15 Inside view of the power module
The Wave Roller System is
a plate lying on the bottom
of the sea, whose back and
forth movement caused by
bottom waves is collected
by a piston, as illustrated in
figure 17.
The piston compresses oil
to power a hydraulic
motor, which drives in turn
an electric generator to
produce electrical energy.
6. This is a typical undersea system used because the
bottom waves are more continuous and predictable than
surface waves. Figure 18 shows an array of these floating
plates placed on seabed.
e (t ) = −
dψ
dt
(4)
giving an alternating voltage at coil terminals, which can
be applied to an electric load. Compared to most other
wave energy devices, the Archimedes Wave Swing also
takes up a proportionately smaller area of the sea, in
relation to power generated.
shaft
connected
to the buoy
permanent
magnet
Fig. 18 Array of Wave Roller plates.
Invisible from the surface, the system has a low
environmental impact. Unit plates of 15 kW each are
generally used. Contract discussions to install the Wave
Roller System are already underway in Finland.
e(t)
fixed coil
G The Archimedes Wave Swing
The Archimedes Wave Swing (AWS) is a submerged
cylinder shaped buoy, moored to the seabed, at least six
metres below the sea surface. Passing waves move an air
filled upper casing against a lower fixed cylinder, with
the up and down movement converted into mechanical
energy, as shown in figure 19.
wave propagation
oscillating
cylinder
fixed
cylinder
s eabed
s eabed
Fig. 19 Archimedes Wave Swing
The mechanical energy is converted into electrical energy
by means a linear synchronous generator. The stator is a
fixed coil to seabed. The linear rotor is a permanent
magnet connected to the oscillating buoy by means a
shaft, as illustrated diagrammatically in figure 20. During
the rotor oscillation the linked magnetic flux ψ with the
coil will induce in it, according to Faraday law, an emf
given by
ψ
Fig. 20 AWS permanent magnet linear electric generator
With a low environmental impact and hazards to
shipping, Archimedes Wave Swing system has high
power density, it can survive the most violent storms and
minimising maintenance at sea.
It is believed that this system will lead directly to the
construction of the first mini wave park of Archimedes
units in Scottish waters, by the third quarter of 2010,
expanding within 12 months to 20 units.
The main early markets for Archimedes Wave Swing will
be Scotland, Portugal and Spain.
H Bristol Cylinder
The Bristol Cylinder consists in a floating cylinder that
collected the wave’s movement. The cylinder is
mechanically connected to the energy unit by flexible
joints and rods. The rods are moving slowly with cylinder
and the reciprocating motion is transferred to the axels in
converter unit. 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. For the energy unit a suitable
slow speed generator will be needed. When transfering
converter movements with mechanical arms and rotation
7. to the generator the efficiency should be kept as high as
possible. The Bristol Cylinder operates under the sea
level as shown in figure 21.
sea level
The MW cost installed to be competitive is situated in 0.5
to 0.6 M€/MW and the economic competitive is
attainable when is installed at least a power of 6.8 GW.
Presently, the world wave energy market is situated in
750x106 €. The European Union estimates a wave energy
cost of about 5 €/kWh.
waves
Floating
cylinder
under sea
electric
generator
Escone
oscillating
movement
converter
Fig. 21 Bristol cylinder for wave energy extraction
Two or more Bristol cylinders could be connected in
parallel. It is also possible to make wave parks near shore
or wind power units connected together like float
offshore. In offshore the converter parts can be located
above the sea level and the collector rotation just under
the sea surface. This method of collector wave energy is
in the process of pending patents in Finland.
7. Conclusions
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.
Acknowledgement
6. Wave Energy Market
Construction of wave parks should be made in areas of
moderated or lower environment sensibility, using safe
technologies. The relative costs distribution of a wave
park plant is shown displayed in the graph of figure 22.
grid connection
13%
5%
Thanks are due to the Electrical Engineering Department
of the Faculty of Sciences and Technology of Nova
University of Lisbon for the help in the preparation of
this work. The author is also grateful to Centre for
Technology and Systems (CTS) from Uninova for the
financial support provided.
4% 2% project
management
assemblage
27%
anchorage
structures
mechanical and electrical equipment
49%
Fig. 22 Costs distribution for a wave power plant
References
[1] Bent SØrenfen: “Renewable Energy”, Elsevier Academic Press, 2004 Edition.
[2] A.J.N.A. Sarmento, L.M.C. Gato, A.F. de O. Falcão,
"Turbine-controlled wave energy absorption by
oscillating-water-column devices". Ocean Engineering, vol. 17, p. 481-497, 1990.
[3] A.O. Falcão, P..P. Justino, “OWC wave energy converters with valve-constrained air flow”, Proceedings
of the Second European Wave Power Conference,
European Commission, EUR 16932 EN, 1995.
[4] A.F. de O. Falcão, P.A.P. Justino, “OWC Wave Energy Devices with Air-flow Control”. Ocean Engineering, vol. 26, p.1249-73. 1999.
[5] B. Weedy and B. Cory: “Electric Power Systems”,
Wiley, Fourth Edition, London 1998.
[6] Wikipedia: Web site on Power Waves
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