sábado, 21 de mayo de 2011
What Is Tidal Energy?
Energy is the greater or lesser capacity to perform work or produce an effect in the form of movement, light, heat, etc. Is the ability to produce change.
With an average of 4 km deep, seas and oceans cover three quarters of the surface of our planet. Represent an enormous reservoir of energy always in motion. On the surface winds cause waves that can reach 12 meters, 20 meters below the surface, temperature differences (which vary from -2 º C to 25 º C), generate current, and finally, both on the surface and substance, the combination of solar and lunar attractions.
Tides, ie the movement of sea water, produce energy that is transformed into electricity in tidal power stations. It exploits the energy released by seawater in their movements rise and fall of the tides (ebb and flow). This is one of the new ways of producing electricity.
The system consists of a pinching of the water at the time of high tide and release it, forcing it to pass through the turbines at low tide. When the tide rises, the sea level is higher than the water inside the estuary. Opening the floodgates, the water passes from side to side of the dam, and their movements are also moving turbine generators running around next to the channels through which water circulates. When on the contrary, low tide, the sea is dela level lower than the river, because water movement is in the opposite direction as above, but tambe is used to produce electricity.
The terrestrial and lunar gravitational energy, solar energy and wind power are, respectively, to three forms of ocean energy, tidal waves and thermal gradients. It can extract energy by suitable devices.
The tidal energy or wave is used in sea water by damming natural coves and by passing through hydraulic turbines.
The slight difference in temperature between the surface and reaches the deep sea (gradient term), is a source of energy called mareomotérmica.
The energy of the waves produced by winds and very irregular. This has led to the construction of multiple types of equipment to enable their use.
The three categories of movement of the sea:
Due to the joint actions of the Sun and the Moon there are three types of changes in sea surface:
- Ocean currents
- Waves and waves
Ocean currents are large bodies of water, as a result of
Heating and exclusive direct action of the sun, moving horizontally, then, are real salty rivers that cross the ocean surface.
His training also influences the salinity of the water. The width and depth of the ocean currents are sometimes considerable, the latter achieved in some cases hundreds of meters. The sense in which progress is different in the hemispheres, northern and southern. Some streams pass from one to another hemisphere, others rise, move, move or die and diluted in the same hemisphere at birth.
The paths of these currents are constant, and this circumstance is what the man advantage during the long era of sailing, was the first and only use the power of ocean currents.
The knowledge of ocean currents, its amplitude, direction, speed, etc., Is of considerable importance to mariners. One of its actions is to divert its route to the vessels that enter them, encourage or impede navigation in the sense in which the scroll. The big warm Gulf stream, which runs from the Gulf of Mexico to the western coasts of Europe, not only softens the atmosphere of these by their temperatures, but also facilitates the Atlantic crossing vessels are heading West to east.
No other has obtained favorable effect man of tremendous kinetic energy of ocean currents. But the results and benefits of another kind (weather anthropogeographical, economic, etc.) Are incalculable.
2. Harnessing wave energy and wave
It has been said that the winds printed to the surface layers of the sea wave motions of two kinds: the waves and waves.
The former can be seen in the sea, even in the absence of wind are moving masses of water and spread on the surface in the form of cylindrical waves. It's pretty rare to see a sea wave isolated, and usually occur several ripples appear on the surface parallel and separated by regular intervals. When a boat goes over the crest of the wave perpendicular to it, the bow rises, and when it drops on the back, the bow sinks into the water. Is the characteristic pitch.
The elements of a wave are its length, ie the distance between two consecutive peaks, the amplitude or vertical distance between a crest and a valley period, estrus is the time between the passage of two consecutive peaks ahead at a fixed point, and speed.
The movement of waves in the sea can be compared with that of a wheat field under the action of wind. The pins are tilted in the direction of the wind, straighten and re-tipping, similarly, by wave action, a smooth and vertical vein, it contracts and becomes thicker in the movement that is formed when the valley while thins and extends in correspondence with the phase of peak or elevation. It seems therefore that oscillates back and forth at a fixed point, dampening the oscillatory motion quickly, to study the sea.
The energy waves develop is huge and proportional to water bodies that range and amplitude of oscillation. This energy is divided into two parts, which practically are the same: a potential energy, which causes deformation of the sea surface, and a kinetic energy or movement due to displacement of the particles, in short, the water body.
If the depth is small, the kinetic energy is transported with a speed that depends on certain characteristics of the wave. It has been estimated that a wave height of 7.50 meters on the level of calm waters and 150 meters wavelength, propagating with a speed of 15 meters per second, delivers an output of 700 horsepower per meter crest, as this wave of the same features that had 1Km. Wide develop the considerable power of 700,000 horsepower. This explains the disastrous effects the sea storms.
The sea waves are formed only at certain points of our planet, and since they propagate radially. Because of its importance will mention one: the area of the Azores islands, located almost opposite the Strait of Gibraltar and about 1800 km west of the center of a quasi-permanent cyclonic area. The large sea waves that form in the islands mentioned, Regrowth by the force of strong winds greatly increase their height, mass and speed of advance.
This explains the effects that occur when lashed the coast of Portugal, Spain, France, England and Ireland.
Simple technique is used to capture the energy carried by sea waves in vertical oscillations. It suffices to have several floats fitted with a rod that slides along guides and vertical movements which are transmitted through the rod to electrical generators. The practical realization of this type of machine is, however, very difficult because, sooner or later, these machines end up being destroyed by too much power to be captured.
Veltri Cattaneo engineer invented a device, installed at the foot of the rocky promontory on which sits the city of Monaco and to provide seawater to the Oceanographic Museum in that city. It consists of a certain diameter shaft that connects the bottom of the sea. Throughout this well moves guided float a heavy iron bars embedded in the wall that drops float buoyancy of sea water and in accordance with the oscillations of its surface. By toggle links, float transmitting its thrust to the piston rods of two hydraulic pumps would-blowers who raised the water to the Oceanographic Museum. This machine, which worked a dozen years, ended up being destroyed by the waves despite its robustness and simple construction. Its yield was small and it is rather a curiosity than a really useful device.
The waves are formed at any point from the sea by the wind. On a calm day in the morning, the surface of the sea is absolutely calm. But when it starts blowing a soft breeze form in the calm surface of water elevations small, tiny waves, the sea is "curls." As wind speed increases, the waves grow in height and mass more quickly than the length, depth, wave. Finally, when the wind blows violently, the waves reach gigantic size and the momentum from that run on the sea surface at high speed and discharge all their power over the obstacles in their path. The effects of these shocks are huge and the amount of energy dissipated in them is considerable.
The effects of such tremendous shocks are visible in ports and jetties, are cited cases in which artificial cement blocks more than two or three tons of weight has been lifted from his seat and thrown several meters away.
They have many appliances and devices designed to harness energy from waves, but none so far has yielded practical results. The wave energy is wild, difficult to tame. In 1929 the practice was the first project to use the horizontal force of the waves used was the Savonius rotor, wheel consists of two asymmetrical half-cylinders mounted on a chassis. The device worked for several months in Monaco. The corrosive action of sea water made them useless.
These and other techniques have been applied to the use of horizontal or translational energy of the waves. The inconsistency of these limits, on the one hand, his job.
The failure of attempts reviewed and many others carried out, seems to show that it is vain to hope to harness energy from waves and waves. But man has resigned himself to contemplate how much kinetic energy is lost, continuous, eternal nature that offers free, in view of the failure of the use of wave energy and wave, technicians focused their efforts use derived from the change in sea level, that is, the tides and the heat of sea water.
Proposed system, to fix the energy of the waves, you can make a classification, which are set on the continental shelf and floats, which are installed in the sea.
One of the first was the Norwegian Kvaerner converter, whose first prototype was built in Bergen in 1985. It consists of a hollow tube of concrete, ten feet long, arranged vertically in the hollow of a cliff. The waves penetrate the bottom of the cylinder and move up the column of air, which drives a turbine installed at the upper end of the tube. This plant has a capacity of 500 KW, serving a village of 50 houses.
The Salter Duck, consisting of an elongated float which is shaped like a duck section. The narrowest part of the float is facing a wave to absorb their movement as best as possible. The floats rotate under the action of waves around an axis whose rotation drives an oil pump that is responsible for moving a turbine.
The difficulty in this system is the generation of electricity with the slow movements that occur.
Cockerell raft, consisting of a set of articulated platforms that are impacted by the wave crests. The rafts up and down pushing a fluid to an engine driving a generator via a hydraulic system installed in each joint.
Russell rectifier, consisting of modules that are installed on the seabed, parallel to the progress of the waves. Each module consists of two rectangular boxes, one above the other. The water passes from top to bottom through a turbine.
Nasuda buoy consists of a device
Floating where the wave motion is used
Low pressure that drives a generator.
3. Harnessing tidal energy:
Tides are periodic oscillations of sea level. It is difficult to realize this phenomenon off the coast, but near them materialize, are evident by the vast sea spaces that regularly exposes and covers again.
This movement of rising and falling of sea water is produced by the attractive action of the Sun and the Moon. The rising water is called flow, and decrease reflux, this shorter time than the first .. The moments of maximum elevation of the flow is called high tide and ebb tide peak.
The tidal range is not the same everywhere; zero in some inland seas, and in the Black Sea, between Russia and Turkey, of little value in the Mediterranean, which reaches only 20 to 40 centimeters, is equal weak in the Pacific Ocean. By contrast, achieves remarkable value in certain areas of the Atlantic, which recorded higher tides. Thus, in the southern Atlantic coast of Argentina in the province of Santa Cruz, the amplitude reaches 11 meters, so that in Puerto Gallegos ships are dry during low tide.
But even more than the tide in some places, such as in the bays of Fundy and Frobisher, Canada (13.6 meters), and in some corners of the European coasts of Britain in the Severn estuary (13, 6 meters), and France in the bay of Mont-Saint-Michel (12.7 meters) and Rance estuary (13 meters).
Belidor, a professor in the School of Artillery of La Fere (France), was the first to study the problem of harnessing the kinetic energy of the tides, and envisioned a system that allowed continuous operation of such energy, utilizing two basins or enclosures conjugates.
The use of tides as a power source mounted several centuries. The coastal rivers and coastal currents were observed spinning the wheels of his mills, which were built along the banks of some rivers in western France and other countries where tides are of a certain intensity. Can still see some of these mills on the shores of Normandy and Brittany in France. Advances in technology led to the abandonment of simple machines as performance, now scarce.
Belidor ideas were picked up by other French engineers who designed a tidal estuary of Avranches in the north and 25 kms from Brest based on building a strong dam to shut the estuary and use the energy of falling mid-tide, calculating turbines to take advantage of a drop between 0.5 and 5.6 meters. Studies for this project was ready in late 1923, but the project was abandoned.
Other projects were studied in the United States to harness the power of tides in the bay of Fundy and other smaller ones that open in it, which offer uneven tides of up to 16.6 meters. Cobscook was built in a tidal average yield, which lasted for a few years, since its performance was more expensive than inland power plants.
The theories put forward by Belidor in his Treatise on Hydraulic Architecture (1927) were in the air, but the idea of harnessing the huge tidal power was never completely abandoned, only when sufficiently advanced technology, there emerged a group of engineers who undertook the project to solve the problem definitively.
The first serious attempt to take advantage of tidal energy is currently performed in France, precisely in the Rance estuary, off the coast of Brittany. Only covers 2,000 ha. But meets the conditions magnificent end in view, the level between high and low tide reaches a maximum of 13.5 meters, one of the largest in the world. The volume of water that entered the second installation is estimated at 20,000 m3. , Which was substantially higher than the second into the sea by the Rhine The cost will be billions of francs, but it is estimated that annual yield over 800 million kw / h. A powerful artificial dam that closes the mouth of the estuary, a lock to keep the communication between it and the sea and navigation ensures inside.
All elements of the tidal station - generators, auxiliary engines, turbines, repair shops, halls and rooms for the staff director and workers, "everything is contained, enclosed by the walls of the mighty dam that closes the mouth of the estuary . A wide cement path that runs throughout it.
4. Ocean thermal energy:
The exploitation of differences in temperature of the oceans has been proposed many times since it hinted d'Arsoval in 1881, but the best known pioneer of this technique was the French scientist Georgi Claudi, who spent his entire fortune, obtained by the invention of the neon tube in a thermal conversion plant.
The ocean thermal energy conversion is a method of converting into useful energy the temperature difference between surface water and the water is 100 m deep. In the tropics this difference varies between 20 and 24 º C. Is sufficient to use a difference of 20 º C.
The advantages of this energy source is associated with a permanent and benign temperature drop from the environmental point of view. May have secondary benefits such as food and drinking water, because the deep cold water rich in nutrients and SPF.
The possibilities of this technique have been enhanced due to the transfer of technology associated with offshore oil exploration. The technological development of deep platform installation, the use of composite materials and new joining techniques make it possible to design a platform, but the maximum problem is economic.
The possibilities for the future of tidal power are not considered as power sources, because of low profitability and the serious assault that would mean for the environment. In Galicia, such stations would only be possible in the Ria de Arousa (Pontevedra), and its construction would involve the destruction of much of the shellfish resources of the estuary.
There are currently four projects approved to restore the maritime heritage and that reference Bolt mills in Escalante, Santa Olaya, Island, Victoria, in Noja, and Jado, under argon.
Escalante: The Lock mill in Escalante is the first one is recovering, with an investment of 24 million pesetas in the first phase, capital from the Ministry of Environment. In ruins, its restoration is being carried out using as models old photographs of early twentieth century and is expected to close by the end of December. It has the objective of this restoration, offering an alternative to beach tourism, attracting visitors the rest of the year through tourism, agro-ecological and economically revitalize the area.
Victoria Mill (in Noja). This mill also tried to reconstruct the purpose of placing a Classroom Observation of nature that allow researchers to develop studies on the region. This building stands on the wall that closes the reservoir and south-facing facade is gone.
Jado mill (in the neighborhood of Ancillo in argon). The restoration project of this mill has a budget of 39.9 million pesetas, and with the mayor, Joaquín Fernández San Emetrio, seeks a symbolic link that contributes to a better understanding of the natural environment and traditions Seven Villas. This initiative will help to enrich the natural and architectural heritage of the municipality and will organize various activities, exhibitions, classroom outreach birding and the environment.
Molino de Santa Olaya (Jewel marsh) The rehabilitation of this mill has a grant of 50 million pesetas from the Ministry of Environment, a project that was part of a major initiative to rebuild the mill Escalante, called the "Ecopark Trasmiera" which is to promote tourism through the use of knowledge and cultural and environmental heritage.
In some coastal regions are given a particularly high and low tides. In these places, large dams proposed coastal power would generate large volumes of water, even with small differences in height. It's like hydropower, but the origin of gravitational attraction of the sun and especially of the moon, instead of the hydrological cycle. In Mexico, in general, this resource is not abundant.
The largest tidal power plant is in the Rance estuary (France). The first windmills appeared in France tides. These were installed in the center of a dike that closed a cove. This created a reservoir that was filled during the reflux through a gate, during the ebb, the water rose and drove the wheel paddles. The energy was obtained only once per trip. If it has taken so long to move from rudimentary to know today, is because the construction of a tidal poses significant problems, requiring advanced technological systems.
The reservoir created by damming the Rance works has a capacity of 184000000 m3 between high and low water levels. It stretches for twenty miles, that stretches to the edge of Rance, next to the deepest part of river.
The innovation consists of the installation of groups such as "bulb" of users to exploit the current two-way flow and ebb of this form is used to maximize the potential of the tides.
Each group consists of a turbine, whose four-blade impeller is adjustable and is coupled directly to an alternator. Work both within a crater-shaped metal warhead.
The tidal plant with a set of 24 bulb has an important group of 220 megawatts, in addition to the power supply, is a major research and development center, and thanks to it must be technological advances in the construction of concrete structures into the sea, studies of resistance of metals to marine corrosion and development of bulb groups.
But the momentum in the use of this energy source, was obtained by the turbine "Strafflo" in testing since 1984 in the Bay of Fundy, Canada (where there are the highest tides in the world) there exists a power of 18 MW. The innovation of this system is that the electric generator surrounding the turbine blades, rather than be installed below the same axis. This will get a performance boost because the generator does not get in the flow of water.
Britain also constructing a tidal power project in the Severn estuary, having studied two possible locations, which seemed more favorable / called Cardiff-Weston), supposed to build a dike of 16.3 kilometers to place turbogroups 192, with a expected production of 14.4 TWh / year, but projected a social rejection by the impact to the ecosystem.
Rance tidal plant (France)
5. Advantages and disadvantages of tidal energy
- Auto renewable.
- No pollution.
- Low cost of raw material.
- No concentrated population.
- Available in any climate and season.
- Visual and structural impact on the coastal landscape.
- Location on time.
- Depending on the tidal range.
- Transfer of expensive energy.
- Negative effect on flora and fauna.
6. Opportunities in Argentina
The tidal range in the South Atlantic Coast of our country is one of the highest in the world, a circumstance that creates the hope of harnessing tidal energy at low cost and daunting.
Thus, experts focus on the Valdes Peninsula, northwest of Chubut, formed by the San José gulfs to the north, fed by the Gulf of San Matías, and the Golfo Nuevo, south, fed by the O. Atlantic.
The narrow Istmo Carlos Ameghino (5 to 7 km wide) separating the two Gulfs, acts as a magnificent natural dam. Contains either side of the growing water and drainpipes that will rotate in either Gulf. The tidal wave, moves from the poles, that is, to us from south to north and physical conformation of the Golfo Nuevo to 5.6 meters wide and the Gulf of San José with the feature to exist between the two Gulfs range flood-tide of five hours.
Because of these slopes, there are energy values that give the conclusion that unstable power would double the current installed hydroelectric capacity in the country.
With less optimism, several proposals have been more about the closure scheme of San José and Nuevo Gulfs by dams, and its communication by a canal across the Isthmus where the plant would be located. This plant, as technical reports, could produce more than 8,000 billion kilowatt-hour clean energy and unique in the world to be continuous.
The possibility of energy in the peninsula, has a long history (the first project of utilization data, 1915) culminating in the enactment of Law 20956 passed in 1975 which provides, in a period not exceeding 3 years, the development of harnessing tidal power project in the Peninsula Valdés, using the tidal phase shift between the Golfo Nuevo and San José.
The need to seek new sources of natural energy forces us to develop new harvesting technologies, the Valdes Peninsula offers promising chances of success.
Our project to harness the use of this energy in Argentina, will be held in the South Patagonian the country, because here are the major tidal amplitudes and are in strong winds.
The buildings to be small and made of corrosion resistant materials to sea water, thus avoid the deterioration of these buildings and reduce the chances of an environmental impact.
While this construction requires a high cost of implementation, there would be a disadvantage, since over time the use of this energy savings will show us both to give us the energy produced by tides and to stop buying fuel . We can say that in the long term, this work will pay for itself.
For the realization of this project would employ people trained and efficient construction, as well as would consult with experienced professionals in the field.
As for the problem represented by the visual and structural impact of the coastal landscape, we would build our plant in an area with little competition tourist
In summary, we base our project on savings, efficiency and utilization of natural energies.
7. Importance of using fossil fuels
Are coal, oil and natural gas, formed by decomposition of plants and animals that lived millions of years ago and were deposited within the earth. Represent the solar energy stored underground.
When these fuels are burned, they release energy accumulated over millions of years, producing heat and CO2. They are formed by H and C and are considered the energy that moves the world.
Not only used for energy conversion, also served in the chemical industry in the manufacture of various products.
But despite moving the world, these fuels are the main responsible for environmental degradation and pollution as burning coal, gas, naphtha and other petroleum products, removes oxygen to the air, producing heat and releasing carbon dioxide and other gases.
We must remember that cause us problems.
The sun's energy reaches the earth in the form of various radiations, some as light or visible light radiation and other invisible as the infrared and ultraviolet. A portion of that energy back into space, as reflected by clouds, dust, air, the other part reaches the ground where it becomes heat back into space.
But there are gases such as carbon dioxide, nitrogen oxides, sulfur oxides, water vapor, which absorbs heat energy from the earth's surface, producing the so-called "greenhouse effect", which is the normal process that keeps a stable temperature on the planet.
After this work, we conclude that we must consider several important points or concepts have a clear idea on the subject.
The first thing to consider is that we must encourage the use of tidal energy, as well as having the full use of clean and alternative energies such as solar and wind, among others, the most important thing here is to finish once and for all with the use of fossil fuels, as we saw, is one of the causes of global warming.
If the carrying out of a conclusion means to summarize on the subject, we can say that the use of water as a natural resource, means taking into account factors such as those involved in this work, among which we mention the influence of the stars that cause changes in the sea, or even the presence of the winds that produce waves, among others, the most outgoing of the use of the sea, is it environmentally friendly. We can also include in this short summary is that (as the project that we do) while capital investment to be undertaken is large and that our country has a lot of important, at the same time, the use of energy clean forms a source of savings.
It is considered important to highlight the global warming issue (on news reporting) and is a current issue and truly frightening. We also considered necessary to be honest and accept that media coverage of the issue we got under, and it seemed a good idea all the news relating to our theme and globalize all the following conclusion:
Fossil fuels are the main energy producers, also, as mentioned, are largely responsible for warming the earth. If we take as basis the use of renewable energies, not only prevent pollution but also save a lot. In our country, wind power is very important (in Patagonia mills are installed), as well as solar and tidal power in the area of the Peninsula Valdes.
Considering that oil also is a highly polluting factor, we just have to see the information about stroke in different rivers and seas, and cause disastrous events, not only water but also in the flora and on wildlife that live there.
So we think that although we can not install a tidal power plant, nor windmills can avoid energy waste from our homes, saving it, even to ourselves. Then switch off the lights and do not need that kind of thing we heard thousands of times.
So yes, in our view, those who deal with these issues should take into account projects to harness energy from renewable sources, but as we said before, Who's going to pay attention to us?
"Economic Geography." Ediciones Macchi.
"Adventures in Science Energy (a resource for knowing and caring)," Standard Canton. Editorial Astros.
"The World of Energy", Luis Postigo. Editorial Sopenahttp: / / www.blogger.com / img / blank.gif.http://www.blogger.com/img/blank.gif
J. Betiana original publication SCANAVINO in www.monografias.com
Publicado por Luis Fraczinet