CONCLUSION to our physics SIA

Is this where we summarise all the information we have gathered, and talk about new insights and observations?

Hmm.. sure hope it is.

Okay then. PHYSICS SIA-- WAVE ENERGY! (:

We had started off with merely a load of question marks in our head, wondering what we were supposed to do, where we were supposed to start, what we were supposed to end up with...
And when we finally did decide to start on our project, we still didn't have any of the answers to those questions anyway. We just started because our conscience and the fact that our physics marks were at stake were beckoning us to start; so we did.

The very first big leap we took was forming the agenda for our online journal / weblog. After we crafted what we were going to include, we went on adding posts with information on wave energy, step at a time (:

Thus, we now see that our blog includes an introduction to wave energy, a few physics principles and theories of wave energy, some devices used to harness wave energy and often, convert it into electrical energy, common uses of this wave energy, the general advantages and disadvantages of using wave energy as an energy source, and lastly a case study on 1 country (or so we intended to).

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But of course it is apparent that our 6th point had been revised, due to the fact that we could not find information for wave energy usage for a specific country. Our sixth point is instead a case study on a particular wave power generator, and we closely relate this case study to the physics principles mentioned in an earlier post (point number 2).

If we were to give a summary of all the points,
...

it would take forever. No, honestly.

But we'll still give a summary anyway. (on the main areas of study in this broad topic)

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1) Introduction to wave energy

--> Waves are created by the progressive transfer of energy from wind currents passing over the surface of the ocean.
--> Large waves are generally more powerful. Its power can be determined by wave height, wave speed, wavelength, and water density.
--> Wave power refers to the energy of ocean surface waves and the capture of that energy to do useful work - including electricity generation, desalination, and the pumping of water (into reservoirs).
--> Wave power is a form of renewable energy and is generally rather pollution-free.

2) Physics principles and theories of wave energy (process of harnessing wave energy; conversion of forms of energy)

--> Wave energy, is created by natural conversion of part of the wind energy above the oceans. Wind energy is created by natural conversion of part of solar energy. By heating air, the sun creates winds (This is because warmer air rises up while cooler air falls due to the difference in density). The winds blowing along the water surface create waves. Wind pressure pushes down wave troughs and lifts up wave crests.

--> Bernoulli's principle states that as the speed of a moving fluid is directly proportional to the pressure within the fluid.

--> Ocean waves encompass two forms of energy: the kinetic energy of the water particles, that in general follow circular paths; and the potential energy of elevated water particles. On the average, the kinetic energy in a linear wave equals its potential energy. This, essentially, illustrates the principle of conservation of energy, that energy can be converted from one form to another, and cannot be destroyed nor created.

--> The energy flux (rate of flow of fluid / particles / energy through a given surface) in a wave is proportional to the square of the amplitude and to the period of the motion.

3) Devices used to harness wave energy and often, convert it into electrical energy

--> terminator devices, oscillating water column, point absorber, attenuators, overtopping devices, seagoing vessels, heaving devices, pitching devices, surging devices.

--> An economically viable design with a simple geometrical construction but strong enough to withstand against the waves with different heights and different wave periods and directions is essential.

4) Uses of wave energy (How it helps in carrying out business within the industry)

--> There has been research into potential uses for wave energy other than electricity, most notably desalinization and hydrogen generation.

--> The electricity generated using wave power is usually used to run large factories and companies, which may otherwise cause the depletion of fossil fuels that are non-renewable. Otherwise, the generated electricity may also be supplied to households in order to power appliances used in daily life, as well as effectively reduce the already large amount of carbon emissions that the particular country is giving out. This an effort to reduce the harm we are doing on Mother Earth can help save up to 10,000 tonnes of carbon dioxide each year.

--> Electrolysis is currently the most viable means of producing hydrogen from any of the four alternative energy sources. Electrolysis involves the dissociation of water into hydrogen and oxygen by passing a current (generated by wave energy) through an electrochemical cell, and has been available commercially for decades

--> The panel motion is coupled by a connecting rod to a fluid pump which generates a high-pressure fluid output that may be used to drive a reverse osmosis desalination unit or to produce other useful work. Seawater or brackish water may be desalinated through reverse osmosis membranes to produce water quality for consumption, agricultural, or other uses. The pump may be of the positive-displacement piston type, plunger type, or multi-staging driver type, or a variable volume pump.

5) General advantages and disadvantages of using wave energy as an energy source (further improvements to be made to the level of efficiency of harnessing the energy of waves to generate electricity and numerous other uses)

--> Little to no chemical pollution during operation and little to no land use
--> Is a renewable and highly sustainable non-nuclear source of energy (green energy); wave energy is naturally replenished, in a sense that they cannot 'run-out'.

--> predictable and dependable (wave power spectrum, can be determined beforehand)

--> many ideal locations in Europe, North and South America, Africa, South Pacific Ocean and Asia where high power densities exist close to highly populated areas

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IMPORTANT:

As we come to the end of our series of posts on this online journal regarding the power of waves, a simple conclusion can be drawn... that there is indeed a great possibility that wave energy will be one of our essential energy sources in the future. Considering the fact that global warming, ozone layer depletion and so on have been a worry to us ever since so many decades ago, the potential of wave energy and other 'green-energy' sources will definitely be maximised. Besides being environmentally-friendly, wave energy is a renewable source, thus the problem of 'limited energy resources' can probably be eliminated and ignored. Wave energy plays a major role in the world's efforts to prevent climate change.

Water, being almost 800 times denser than air, would also allow wave power generators to yield much more energy than, for instance, wind power generators, thus satisfying the overwhelming needs of our growing population, economy and commercial industry. At the moment, harnessing this energy may pose a considerable problem due to certain technological limitations, but with the advancement of mankind as well as science and technology, very soon, the use of such renewable energy sources will be possible, and the dream of a greener, less-polluted-than-ever-before Earth will be realised..

References

1) Wikipedia. (2008). Standing Wave. [online]
URL: http://en.wikipedia.org/wiki/Standing_waves (28 April 2008)

2) WAVEenergy. (2005). Harvesting the power of the ocean. [online]
URL: http://www.waveenergy.no/ (7 May 2008)

3) AEoogle. (unknown). Wave Power. [online]
URL: http://www.alternative-energy-news.info/technology/hydro/wave-power/ (18 May 2008)

4) The New York Times. (2007). Wave Energy. [online]
URL: http://www.nytimes.com/2007/12/09/magazine/09waveenergy.html?_r=1&oref=slogin
(18 May 2008)

5) Department of Physics, NTNU. (1997). Wave-energy Research. [online]
URL: http://folk.ntnu.no/falnes/w_e/index-e.html (30 May 2008)

6) Energy Resources, Wave Powder. (2008). Wave Power – energy from the wind on the sea. [online] URL: http://home.clara.net/darvill/altenerg/wave.htm (2 June 2008)

7) Earthlink. (2003). Animated Demonstration of Bernoulli’s Principle. [online]
URL: http://home.earthlink.net/~mmc1919/venturi.html
(7 June 2008)

8) Energy Information Administration. (unknown). Ocean Energy. [online]
URL: http://www.eia.doe.gov/kids/energyfacts/sources/renewable/ocean.html
(10 June 2008)

IT'S REVIEWING TIME

HELLO EVERYONE!

From this day onwards, it will seem as if we are ignoring the existence of this 'PHYSICS SIA 2008' weblog.
Why?

IMPORTANT NOTICE:

We regret to inform the world that from this day onwards, there will be no new posts, therefore we may appear to be hibernating instead of updating the weblog regularly.

BUT, not having new posts DOES NOT mean we're not updating our blog!

As you can see, we have gathered information and collated data (look below!).
However, we will need to carry out a few essential and necessary things, such as..
ASCERTAIN that the information is accurate and true,
EDIT the information,
ADD MORE information,
REVIEW the information,
UNDERSTAND the information well enough to
INSERT OUR OWN OPINIONS, VIEW AND NEW INSIGHTS!

..and so on (:

We appreciate your kind understanding and cooperation.


Yours sincerely,

The authors of this weblog
YCYS!

Case study -- Limpet (Wave power generator) by Wavegen

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27/05/08

Limpet is a shoreline unit to generate electricity in areas exposed to strong wave energy. It is located on the island of Islay, which is off the west coast of Scotland. The wave power generator was designed and built by Wavegen and researchers from Queen's University in Belfast and has financial backing from the European Union. The current Limpet device is called Limpet 500, which means that it can generate 500 kilowatts of electricity into the island of Islay.


How does Limpet work?

Limpet uses the principle of an oscillating water column (OWC). An oscillating water column is a partially-submerged, hollow structure, either vertically or at an angle, either in shallow water or onshore.















The waves continuously build up crests and troughs in front of the rock face of the power generator. Then, wave power forces seawater to enter the shell chamber. The interior of chamber also follows the sequence of the wave outside the chamber.

During crest formation, the level of water in the chamber rises, compressing the entrapped air at the top of the chamber to a value that is slightly above the atmospheric pressure. Thus, the air is forced through a “blowhole” and into “Wells Turbine”, which is designed by Professor Alan Wells of Queen’s University in Belfast.

However, during trough formation, the water inside the chamber recedes, the air is then decompressed to be under atmospheric pressure. This keeps the turbine moving. However, the crest and trough formation of the wave also cause the air to move in two directions. Hence, Wells turbine has been designed to turn successively in only one direction regardless of the direction of the airflow to ensure the efficiency of the harvesting of energy.

The rotation of turbine produced by the constant movement of air is tehn used to drive a generator that converts the energy into electricity.

--yingshi

Edited and reviewed by: seokting on 26/06/08

General advantages and disadvantages/impacts of using wave energy

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22/05/08

ENVIRONMENTAL IMPACTS

Positives:

1) Little to no chemical pollution during operation and little to no land use (Lemonis 2004). These devices would have very low greenhouse gas emissions estimated at 11g of CO2 per kWh for near-shore schemes (Duckers 2004), and 21.67g per kWh for the off-shore Pelamis device (Banjeree et al 2006). This compares to a release of about xx KG of CO2 per kWh for coal-fired electricity production. Environmentally benign and non-polluting: no fuel, no exhaust gases, no noise. Minimal visual impact.

2) As a renewable and highly sustainable non-nuclear source of energy (green energy), wave energy is naturally replenished, in a sense that they cannot 'run-out', is in constant supply over time and that has environmental and social impacts that are generally more benign that that of fossil fuels.

3) Wave power is predictable and dependable, thus humans can be armed with the ability to accurately forecast the wave power spectrum days in advance. This way, they can be well prepared for the next strong currents in order to harness the maximum amount of energy possible and obtain the energy needed for conversions to other forms.

4) There are many ideal locations in Europe, North and South America, Africa, South Pacific Ocean and Asia where high power densities exist close to highly populated areas, therefore there is potential for wave energy to be harnessed and put to efficient, effective use to support many many households, especially when it comes to the generating of electricity.

--cassandra

Negatives:

1) These devices require very high construction costs. From a net energy perspective, the energy required to build the infrastructure may outweigh the small amount of electricity wave projects are capable of producing in the short term. Severe storms have dashed the hopes of some earlier projects, probably before serious energy has been returned.

Wave energy is at an early stage of development and is therefore still relatively expensive when compared to other sources of electricity. The House of Commons Science and Technology Committee concluded in 2001 that a true picture of the likely cost of wave power will only be available after the industry has matured and large devices have been operating for some time. However, the cost of wave energy has fallen over the past 10 to 15 years and ongoing technological developments mean the predicted costs of wave energy are continually being reduced.

2) They may also alter coastlines by changing energetic patterns of waves (Lane 2007 may generate various environmental impacts, most of which are unknown. Some wave energy devices may affect the natural flow of sand and other beach sediment and so would require sensitive siting but the installations could also potentially benefit the environment by creating safe havens for fish and helping to reduce coastal erosion.

3) Other potential impacts, such as disruption of marine habitat and fish migration patterns, and sedimentation, are generally agreed to be minimal, but important considerations on an individual project basis.

4) There are also noise impacts due to some devices used to harness wave energy.

5) Though the wave devices have no emissions during generation but the energy associated with the construction of the device does have small associated emissions.

6) There has been some concern about aesthetics and disruption of fishing, shipping, and boating. These impacts would occur in both construction and operation.

--yuwei

Edited and reviewed by yingshi on 19/06/2008

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11/06/08

Public Perception

Public attitudes toward ocean energy technologies are unknown, but clean energy is generally perceived in a positive light because of its environmental and other benefits. Successful demonstration projects and careful siting practices will help ensure public acceptance of these emerging green energy options.

All new and unfamiliar technologies may initially be viewed with skepticism. In addition, concerns have been expressed over the potential impacts of shoreline and nearshore wave energy devices related to aesthetics as well as sediment transport and other physical processes. These and other technologies may also impact recreational and commercial activities.

OVERCOMING 'negative' point number ONE, which is the only one that can be solved at all

Wave energy is already competitive in niche markets, such as remote islands, which are often reliant on expensive (and environmentally detrimental) diesel generators. The development of wave energy alongside other technologies - fish farms, harbour defences, desalination plants or wind farms could further reduce costs. In addition, there are potentially many opportunities for the wave energy sector to collaborate with the wind power industry, both on joint projects (e.g., combined offshore facilities) and by addressing common problems such as connecting the electricity they generate to the National Grid.

--yuwei

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17/06/08

Challenges

These are some of the challenges to deploying wave power devices:
Efficiently converting wave motion into electricity; generally speaking, wave power is available in low-speed, high forces, and the motion of forces is not in a single direction. Therefore, it is a challenge to ensure most of the wave energy which acts in different directions to be converted to electrical energy. Besides, as solar energy is converted to wind energy and finally to wave energy, much energy is lost to the surroundings in the process of conversion and hence, it is very important to prevent further loss of energy. Most readily-available electric generators operate at higher speeds, and most readily-available turbines require a constant, steady flow.

Constructing devices that can survive storm damage and saltwater corrosion; likely sources of failure include seized bearings, broken welds, and snapped mooring lines. Knowing this, designers may create prototypes that are so overbuilt that materials costs prohibit affordable production.

High total cost of electricity; wave power will only be competitive when the total cost of generation is reduced. The total cost includes the primary converter, the power takeoff system, the mooring system, installation & maintenance cost, and electricity delivery costs.

--yingshi

Edited and reviewed by the same people who wrote it:

26/06/08

Uses of wave energy

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13/05/08

Wave energy has yet to be demonstrated as a possibility for large-scale commercial power generation. However, with the rising costs of fossil fuels and increasing environmental concerns, a competitive wave industry, if developed, could be one of the most environmentally benign of the renewables. The most practical application for wave energy in the short to medium term could be on small, remote islands without easy access to fossil fuel shipments or the need for long transmission lines. The potential for these sorts of small but locally important projects seems highest in the UK, where wave power density is high and much of the research is centered. Ocean Power Delivery, the Scottish company that provided the 2.25 MW installation in Portugal, is planning a 3 MW project in Orkney, the small island systems off the north coast of Scotland (OPD 2007). There has also been research into potential uses for wave energy other than electricity, most notably desalinization and hydrogen generation.

Wave energy conversion device for DESALINIZATION

An impulse-type “wave motor” employs a seabed-mounted or supported structure mounting a wave energy absorbing panel on a hinged lever arm for reciprocation motion to obtain optimal absorption of wave energy from wave motion in the sea. For deepwater wavelengths of L, the panel is optimally positioned in a region within L/2 depth from the sea surface. The panel motion is coupled by a connecting rod to a fluid pump which generates a high-pressure fluid output that may be used to drive a reverse osmosis desalination unit or to produce other useful work. Seawater or brackish water may be desalinated through reverse osmosis membranes to produce water quality for consumption, agricultural, or other uses. The submerged operating environment of the device in a region of one-half the design wavelength provides the maximum available energy flux and forced oscillations. The pump may be of the positive-displacement piston type, plunger type, or multi-staging driver type, or a variable volume pump.

--seokting

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13/05/08

Storing and Transporting Energy as HYDROGEN (hydrogen generation)

Offshore wind, solar, and wave energy do not always produce energy at the time at which it is needed. In addition, the energy produced at remote offshore locations using these technologies and ocean current technology must typically be brought to onshore consumers. To address the sporadic nature of energy production from these sources at offshore locations, feasible methods for storing excess energy until it can be used and for transporting it must be developed. Currently, the most attractive approach is the use of hydrogen as a storage medium. Hydrogen can be generated on location on a variety of scales, and it can be stored and transmitted for later consumption in fuel cells in vehicles or converted into electricity. At this time, however, hydrogen is not being used to store or transport energy produced with ocean energy technologies in commercial applications.

HYDROGEN PRODUCTION

(Offshore electrolysis-hydrogen generation unit)


In future commercial applications, hydrogen could be produced offshore at the point of energy generation in a co-located facility, or it could be produced at an onshore location, utilizing the energy generated at the offshore power generation facility. Because all four alternative energy sources under analysis in the OCS Alternative Energy Programmatic EIS are capable of producing electricity, electrolysis is currently the most viable means of producing hydrogen from any of the four alternative energy sources. Electrolysis involves the dissociation of water into hydrogen and oxygen by passing a current through an electrochemical cell, and has been available commercially for decades.

--cassandra

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06/06/08

But of course, after all that, we still have to come back to the most essential and prominent use of wave energy: the conversion of this kinetic energy into electrical energy!

CONVERSION TO ELECTRICAL ENERGY

During the next 20 years, experts foresee a need for 1500 GW. of additional power supply to meet new demand. This equals to 15000 power plants that are 100 MW each and 59 million barrels of oil consumed in each day. The world Bank estimates that the developing countries alone will need to spend $100 billion each year for the next 30 years installing new power plants most of which will be in the equatorial Zone. These are astronomical figures that could mean enormous quantities of fossil fuel and 2.2 billion tons of CO2 release to the atmosphere per year. Hence, an urgent need to switch to alternate energy. Among the alternate energy resources, wave energy is considered as one of the promising alternate energy resources that has high availability factor (day & night) compare with other resources such as Wind energy or Solar energy.

It has been estimated that if less than 0.1% of the renewable energy available within the oceans could be converted into electricity, it would satisfy the present world demand for energy more than five times over.

Therefore, it is important and worthwhile to conduct experiments on wave energy harnessing techniques to tap the wave power to generate electricity.

The electricity generated in this way (using 'green' energy / renewable sources of energy) is usually used to run large factories and companies, which may otherwise cause the depletion of fossil fuels that are non-renwable. This, therefore, facilitates the progress made by

commercial industries without causing too large / too many adverse effects on the environment and on society.

Otherwise, the generated electricity may also be supplied to households in order to power appliances used in daily life, as well as effectively reduce the already large amount of carbon emissions that the particular country is giving out. This an effort to reduce the harm we are doing on Mother Earth can help save up to 10,000 tonnes of carbon dioxide each year.

--yuwei

Edited and reviewed by the people who wrote it:

21/06/08

Ocean Wave Energy Technologies / Devices used to harness wave energy and often, convert into electrical energy

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02/05/08

A variety of technologies have been proposed to capture the energy from waves. Some of the more promising designs are undergoing demonstration testing at commercial scales.

Wave technologies have been designed to be installed in nearshore, offshore, and far offshore locations. The OCS Alternative Energy Programmatic EIS is concerned primarily with offshore and far offshore wave technologies. Offshore systems are situated in deep water, typically of more than 40 meters (131 feet).

While all wave energy technologies are intended to be installed at or near the water's surface, they differ in their orientation to the waves with which they are interacting and in the manner in which they convert the energy of the waves into other energy forms, usually electricity. The following wave technologies have been the target of recent development.





















Terminator devices extend perpendicular to the direction of wave travel and capture or reflect the power of the wave. These devices are typically onshore or nearshore; however, floating versions have been designed for offshore applications. The oscillating water column is a form of terminator in which water enters through a subsurface opening into a chamber with air trapped above it. The wave action causes the captured water column to move up and down like a piston to force the air though an opening connected to a turbine. Oscillating Water Columns are partially submerged, hollow structures open to the seabed below the water line. The heave motion of the sea surface alternatively pressurizes and depressurizes the air inside the structure generating a reciprocating flow through a turbine installed beneath the roof of the device.

A point absorber is a floating structure with components that move relative to each other due to wave action (e.g., a floating buoy inside a fixed cylinder). The relative motion is used to drive electromechanical or hydraulic energy converters.

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Attenuators are long multisegment floating structures oriented parallel to the direction of the waves. The differing heights of waves along the length of the device causes flexing where the segments connect, and this flexing is connected to hydraulic pumps or other converters.

Overtopping devices have reservoirs that are filled by incoming waves to levels above the average surrounding ocean. The water is then released, and gravity causes it to fall back toward the ocean surface. The energy of the falling water is used to turn hydro turbines. Specially built seagoing vessels can also capture the energy of offshore waves. These floating platforms create electricity by funneling waves through internal turbines and then back into the sea.

--seokting

Edited and reviewed by: yuwei, 15/06/08

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24/05/08

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There are many wave energy conversion techniques patented worldwide. Some main concepts for wave energy converters can be classified within a few basic types:

• Heaving devices (floating or submerged), which provide a heave motion that is converted by mechanical and hydraulic systems in linear or rotational motion for driving electrical generators.

• Pitching devices that consist of a number of floating bodies, hinged together across their beams. The relative motions between the floating bodies are used to pump high-pressure oil through hydraulic motors, which drive electrical generators.

• Surging devices that exploit the horizontal particle velocity in a wave to drive a deflector or to generate pumping effect of a flexible bag facing the wave front.

An economically viable design with a simple geometrical construction but strong enough to withstand against the waves with different heights and different wave periods and directions is essential. The design would usually consist of a rectangular chamber and a pyramidal top which is installed on top of the chamber. A conical duct is erected on the pyramidal top to reciprocally move the air from the chamber and into the chamber during the process of wave approach and wave leaves the chamber. A turbine which is mounted on top of the duct is subjected to turn in one direction as the airflow moves bi-directional. A generator is coupled to the turbine that produces electricity by rotating it's armature shaft which is coupled with the turbine shaft.

--yuwei

A simple piece of wave-energy-propulsion technology

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The arrows in the bare-bones diagram show the vertical push of the water, the function is caused by the wave or by strong current, acting on a stern-mounted rigid blade.

Simplifying the representation to stern-mounted blades only, this illustration shows the response of the system to the surface waves.

In fact, this design calls for an additional set of propulsive blades to be mounted well forward on both sides of the hull. In this top-view illustration, graduated tone is used to indicate a flexible-blade system.

The forward and aft blades function independently. When one is pushed down by the waves, the other is forced up. Similarly, the blades on each side of the boat are also free to respond differently as wave forces shift.

Thirty degrees of deviation from level is acceptable, but not over 45 degrees. The curved line indicates a "quadrant" which is a structure to limit motion inward so that the blade would not rub against the hull. As an alternative, some form of hydraulic system might be designed to enable control over the degree of tilt while eliminating this external structural detail. To achieve a more hydrodynamic shape, the goal of design refinement is to minimize the number of exterior-mounted connecting parts which can become fouled with seaweed or other debris.

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(LOOK AT THE DIAGRAMS!)

The diagram shows support struts with a control joint restricting the amount of motion permitted. Flexible blades might not require this type of joint; in that case, the degree of flex would be that permitted by the material used.

In addition to propulsion, this method of capturing and redirecting the energy into forward motion would theoretically mitigate the infamous up-down, pitching and rolling motions that cause to sea-sickness.

--yuwei

edited and reviewed by: seokting on 17/06/08

Physics Principles involved in Ocean Wave Energy

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23/04/08
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Wave energy, is created by natural conversion of part of the wind energy above the oceans. Wind energy is created by natural conversion of part of solar energy. By heating air, the sun creates winds. This is because warmer air rises up while cooler air falls due to the difference in density. Hence, this creates movement in air, which is wind. Then, the winds blowing along the water surface create waves. Wind pressure pushes down wave troughs (lowest portion of the waves, as shown in the diagram below) and lifts up wave crests (the highest portion of the waves), due to Bernoulli's principle.

Bernoulli's principle states as the speed of a moving fluid increases, the pressure within the fluid decreases, and conversely, as the internal pressure increases, the speed of a fluid decreases proportionally.

(For more information and illustrated diagrams on Bernoulli's principle, please refer to http://home.earthlink.net/~mmc1919/venturi.html)

Hence, as the velocity of the wind increases, the pressure above the surface of the ocean decreases. This creates higher pressure under the ocean surface. The difference in pressure then pushes the water upwards and lifts it up. This is how wave is created. According to Bernoulli's principle, it also means that when the velocity of wind is higher, wavelength is also higher as wavelength determines wave power.

--yingshi

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29/05/08

Both air pressure differences between the upwind and the lee side of a wave crest, as well as friction on the water surface by the wind shear stress cause the growth of the waves. The wave height increases with increasing wind speed, duration since the wind started to blow, and of the fetch (the distance of open water that the wind has blown over).

Thus, in general, wave power is determined by wave height, wave speed, wavelength and the density of water.

Oscillatory motion is the highest at the surface of the ocean and hence most devices used to extract wave energy are built on the surface.

Among different types of ocean waves, wind generated waves have the highest energy concentration. Wind waves are derived from the winds as they blow across the oceans. This energy transfer provides a natural storage of wind energy in the water near the free surface. Once created, wind waves can travel thousands of kilometres with little energy losses, unless they encounter head winds.

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Ocean waves encompass two forms of energy: the kinetic energy of the water particles, that in general follow circular paths; and the potential energy of elevated water particles. On the average, the kinetic energy in a linear wave equals its potential energy. The energy flux in a wave is proportional to the square of the amplitude and to the period of the motion. The average power in long period, large amplitude waves commonly exceeds 40-50 kW per meter width of oncoming wave.

--cassandra

Edited and reviewed by the same people who wrote it:

11/06/08, 27/06/08

A random problem-- image suggestion

SO, as the title of this blog post indicates, the image above sort of explains yingshi's question in a rather comprehensive manner..

hope it helps!

--seokting

Introduction to Wave Energy

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12/04/08

WAVES~~~

Waves are created by the progressive transfer of energy from wind currents passing over the surface of the ocean (as long as the waves propagate slower than the wind speed just above the waves, there is an energy transfer from the wind to the most energetic waves). Waves are formed from turbulence because wind pressure pushes down wave troughs and lifts up wave crests, due to Bernoulli's principle. (will be elaborated in physics principles)

Generally, large waves are more powerful. Specifically, wave power is determined by wave height, wave speed, wavelength, and water density.

The equation here:

View: http://en.wikipedia.org/wiki/Wave_energy#Physical_concepts

where,

P the wave energy flux per unit wave crest length (kW/m),
Hm0 is the significant wave height (meter), as measured by wave buoys and predicted by wave forecast models. By definition, Hm0 is four times the standard deviation of the water surface elevation,
T is the wave period (second),
ρ is the mass density of the water (kg/m3), and
g is the acceleration by gravity (m/s2)

shows the factors affecting the size and power of a wave.

It also states that wave power is proportional to the wave period and to the square of the wave height. When the significant wave height is given in meter, and the wave period in second, the result is the wave power in kW (kilo watt) per meter wavefront length.

--yingshi

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22/04/08

WAVES AS A SOURCE OF ENERGY

Renewable energy effectively uses natural resources such as sunlight, wind, rain, tides and geothermal heat, which are naturally replenished. Renewable energy technologies range from solar power, wind power, hydroelectricity/micro hydro, biomass and biofuels for transportation. Therefore, wave energy does have its benefits of being renewable and environmentally friendly. (This is elaborated further below)

Wave power refers to the energy of ocean surface waves and the capture of that energy to do useful work - including electricity generation, desalination, and the pumping of water (into reservoirs). Wave power is a form of renewable energy. Though often co-mingled, wave power is distinct from the diurnal flux of tidal power and the steady gyre of ocean currents. Wave power generation is not a widely employed technology, and no commercial wave farm has yet been established.

The movement of waves and the rising and falling of tides can be harnessed to drive turbines that generate electricity. There are two main types of wave energy collectors. The first type directs waves into man-made channels, where the water passes through a turbine that generates electricity. The second type uses the up and down movement of a wave to push air.

Wave is a powerful source of energy. In fact, it can go up to many metres in height. The total power of waves breaking around the world’s coastlines is estimated to be 2 to 3 million megawatts.

Wave power varies considerably in different parts of the world, and wave energy cannot be harnessed effectively everywhere. Wave-power rich areas of the world include the western coasts of Scotland, northern Canada, southern Africa, Australia, as well as the northwestern coasts of United States.

Good wave power locations have a flux of about 50 kilowatts per metre of shoreline. Capturing 20 percent of this, or 10 kilowatts per metre, is plausible. Assuming very large scale deployment of (and investment in) wave power technology, coverage of 5000 kilometres of shoreline (worldwide) is plausible. Therefore, the potential for shoreline-based wave power is about 50 gigawatts. Deep water wave power resources are truly enormous, but perhaps impractical to capture.

--cassandra

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08/05/08

BENEFITS OF WAVE ENERGY (brief overview)-- Renewable and environmentally friendly

Wave energy is a renewable and pollution-free energy source that has the potential to contribute with 2,000 TWh per year of the world's energy production.
Wave energy is free. No fuel is needed to generate the energy and thus no waste is produced. Wave energy plays a major role in the world's efforts to prevent climate change. It potentially displaces 1 to 2 billion tonnes of CO2 annually from usual fossil fuel generating sources.

--yingshi

Entire post reviewed and edited by same people who wrote it:

07/06/08

a group discussion (:

Hello there! This blog post merely consists of our group discussion in class on the information and research to include in this blog. So here it is!

Date: Tues, 8 April 2008
Time: 9.45 to 10.15am
Venue: Sec 301 Classroom

Information that our group will include in this online journal :

1) Introduction to wave energy

2) Physics principles and theories of wave energy (process of harnessing wave energy; conversion of forms of energy)

3) Devices used to harness wave energy and often, convert it into electrical energy

4) Uses of wave energy (How it helps in carrying out business within the industry)

5) General advantages and disadvantages of using wave energy as an energy source (further improvements to be made to the level of efficiency of harnessing the energy of waves to generate electricity and numerous other uses)

6) Case study on 1 country

7) Conclusion


GOOD LUCK TO US!!!!! (:

A random problem

From a report, Wave Energy Potential on the U.S. Outer Continental Shelf (2006), it states that:

“Because wind is generated by uneven solar heating, wave energy can be considered a concentrated form of solar energy. Incoming solar radiation levels that are on the order of100 W/m2 are transferred into waves with power levels that can exceed 1,000 kW/m of wave crest length. The transfer of solar energy to waves is greatest in areas with the strongest wind currents (primarily between 30° and 60° latitude), near the equator with persistent trade winds, and in high altitudes because of polar storms.”

I don't understand how wind is generated by solar heating and why it is a form of solar energy.

--yingshi

ALOHA.

GREETINGS ONE AND ALL!

This is Foo Yun Shuen Cassandra (14), Lim Seok Ting (25), Teh Ying Shi (33), Zhang Yuwei (35) from Nanyang Girls' High School, 301, and unfortunately this blog was set up for not-so-fun purposes.

Nanyang Girls' High School is on Jupiter. We come in peace. -SMILES-

We regret to inform the planet Earth, inclusive of Mr Mark Shone of the Earth version of Nanyang Girls' High School that we have only just set up this blog. This is exactly how slow we are. We apologise and shall get to work as soon as possible. Cough.

Oh, we forgot. Our topic is: WAVES and the potential it has as a source of ENERGY (: