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Sea or ocean wave power is getting gradually more noticeable in several countries all over world as most important and potential source. For next level in Renewable technologies, we are in obligations not just to manage with the global warming environment even also to protect natural ecology and to coexist with environment. The founding of a power system that uses sustainable energy is grabbing attention as promising solution to these problems. This paper presents a discussion on one of the renewable energy resources, which is extracting power from waves, and also includes history of power, generated from waves to modern technologies, used so far along with current status of technology and impact of these new technologies in the human lives.
The main motto of this course work is to attain a better insight, into the subject matter of renewable source of energies and its applications. This is very attractive region as it is something that affects everyone, who has special interest in the region of renewable source of energy. Where, power generations from wave are likely to be major growth in years which are recent.
As, a student of electrical engineering in my future career, power will play a vital role. Often, engineers progress to some form of achievement later their career. Wave power generation relates to the energy of ocean waves from surface and the use of that energy to produce electricity (Dean and Dalrymple, 1991). Actual waves are generated by wind stroke and also are an not direct form of solar energy (Goda, 2000).
HISTORY OF WAVE POWER:
The earliest of 1799 on 12 July the work on the field of wave power device was started by both of the family member's father along with son in France named as Girard. This process of transforming wave power in utilizable power has moved many researchers and by the year 1980 more over thousand patents was been registered at that time (McCormick, 1981).
In 1940s, Yoshion Masuda started developing a direction-finding buoy motorized by wave energy which was oscillating water column floating type. That device was used in 1965 in Japan and later by American also. Later on Masuda promoted a large construction of floating type equipped with several Oscillating Water Columns along with different air turbines and named as Kaimei on 1976, which was not great success because the theoretical knowledge at that stage was in initial part(Masuda, 1979).
The major changes in the field of renewable energies occur due to the oil crisis of 1973, which suddenly increases the interest in huge-scale power extraction from waves. The University of Edinburgh which located in Scotland was the major landmark to bring the wave power in the notice of community of intercontinental scientific. In year of 1975, UK administration taking place in the research and further development. Later on international conferences were held on year's simultaneously1976, 1978, 1979, and 1982 (Grove-Palmer, 1982). Where, in Norway 1985 the work went on to large construction with both complete-sized shorelines devices. In the island, Islay at Scotland prototype of OWC shoreline got the visible success in whole Europe after 1990s, because until 1990s, it was in the stage of basic level. In the year 1992 the initial project was started after the noticeably change by the conclusion made in 1991 by R&D program on sustainable energies of European commission (Whittakern etal., 1993).
In 21st century 17 countries made a contract on ocean energy system in 2001, which was establish by international energy agency. From previous only some years, interest in this field has been growing in Canada and USA (Previsic etal., 2009).
VARIOUS TECHNOLOGIES AT MARKETS:
Large varieties of wave power modern methods, ensuing as of dissimilar paths, where power could wrap up from waves, which are present in the markets now-a-days. In Which absorption of power, depend upon the location and water depth such as offshore, shoreline and near-shore. According to researcher reviews more than hundred projects at different stages of progress are been identified in recent years, and it also seems that the numbers of projects are increasing due to vast varieties of technologies. Even the vast varieties of devices has planned but merely a small number of fully- sized devices was been deployed, built in open water of coastal, are every so often called as primary generation device. Where, this type of generation machines near shore or on the shoreline stands on the bottom of the sea or rigid to a rock face. Easier installation of this device is only possible by shoreline devices and also it can be easily maintained because it does not need any electrical cables. Mainly oscillating water column are typically first generation device.(Falcao, 2009).
Fig. 1. Different technologies in wave energy (Falcao, 2009).
OSCILATING WATER COLUMN
The device which comprises partly steel arrangement or submerged concrete, inner side where air is rapt on top of water free face, open below water face is oscillating water column. Incident waves produce the oscillating movement of interior open face, which force the air towards and run throughout a turbine, which drives an electric originator generator. Most of the prototypes used the rectifying valve which was invented in mid 1970s for the axial-well turbines. OWC prototypes of full sized were first constructed at Norway close to Bergen in the year 1985, India near Trivendrum (1990) (Ravindran and Koola, 1991), UK in Islay island near Scotland (2000) (Whittaker etal., 1993). In all of the prototypes, OSPREY is the largest one which was been destroyed by the sea in 1995 near the coast of Scottish and this OSPREY is one of the fixed structure OWC.
OSCILLATING BODY SYSTEMS
Basically Oscillating bodies are offshore devices, which are sometimes classified as third generation devices, it can either fully submerged or floating. Typically in deep water 40 m, offshore devices can exploit the more dominant wave regimes, when compared to the first generating system offshore wave power devices are more complex. In this type of prototypes systems only some of the systems have come close to the complete manifestation stage because of the problems associated regarding with maintenance and mooring, along with this it need electrical cables for long under water (Falcao, 2009).
The conversion of wave energy in different ways, confine water which are nearest to top wave plus initiates it with more out coming spills, in a lake it is suppose to be kept on higher stage, compared to mean free- face point of sea area. Here, hydraulic turbines with extra or fewer conventional low-head are used for conversion of the potential power of the stored water. Due to strongly non-linear characteristics of hydrodynamics of overtopping devices and the cases unlike to the wave power converters in oscillating water column type and theory of linear water wave cannot able to identify oscillating body (Falcao, 2009).
Slack-moored converter of wave power consists a group of half-submerged cylinders attached with help of hinged links is known as Pelamis, which is also known as an offshore and floating wave energy converter. Pelamis execute work on ocean waves by making action to move adjacent cylindrical compartment comparative to both transversely with a degree of two to free links. In both of the axes, which include every each link will be supposed to liable straight to precede a final net liable by the PTO. The liable response offers an efficient hydrostatic solidity compact from an erect response, ensuing in a normal frequency reliant on the slope ( Yemm etal., 2000)
Here, the device can be intended along with a resonate response harmonized to leading frequency of the wave climate in which installation is done, reducing the reactive necessities of the PTO. The groups of cylinders of hydraulic type, which propel liquid, through organize manifolds, in the persuasive accumulator in favor to store temporary energy in Pelamis PTO. The soft deliver of persuasive liquid from accumulator is to start grid-attached electric generator, which is usually used by hydraulic motors. Actually Pelamis PTO is called as primary and secondary transmission. Here, the waves work, up on the arrangements to stored power, are transformed by the hydraulic cylinders along with their controls of primary transmission. While, the secondary transmission transforms the power temporarily kept in hydraulic accumulators into electricity, then again transferred to shore with their hydraulic motors attached to electric generators (Retzler etal., 2003).
Fig. 2. Physical layout of PTO along with the response of Pelamis WEC ( Yemm etal., 2000)
Cylinder provides the looming link moment which must be varied all the way through each wave cycle in a way that the wave can do the utmost quantity of job on the device as a full. Only the electronically controlled valves can achieve the real time grip of the link moment, which manage the run of liquid among accumulator, hydraulic cylinder and basin reservoir. Coupled variable displacement pumps to carry constantly changeable flow along with pressure, usually had a high efficiency of approximately 60% are used by conventional hydrostatic transmissions. Where, in PTO of Pelamis, at any time if compartment is pressurized it swaps fluid in a straight line along with storage accumulator; which causes losses through valves and pipes.. Primary transmission of Pelamis can comfortably soak up incident energies ten times greater than the average incident energy to which the generation apparatus should be economically harmonized (Hendreson, 2005).
An offshore wave energy converter which use works on the overtopping theory is known as the Wave Dragon. Where it consists of reflectors which are two, focus on inward waves towards an access ramp, a reservoir for gathering the overtopping water and also some selected number of hydro turbines for swapping the pressure head into energy. Wave dragon is fully outfitted with automatic control systems (Hald etal., 2002 ). Where, every single component had a power rated between 4-10 MW, depends up on that how much powerful the wave climate will be at research site. Wave Dragon mainly consists of three elements.
First element is two unused wave reflectors tending the waves towards the access ramp, attached to the main arrangement.
Second element is that the main body consists of a patented twice as curved ramp and a reservoir for water storage.
Finally the third element is a group of low head propeller turbines for conversion of hydraulic head in the water storage reservoir into electricity (Frigaard etal., 2004). Wave dragon is one of the unique wave energy converters among of all other converters because it uses the power in the water straightly through water turbines. Even though, it is feasible but the design of wave dragon is little bit complex, to develop well-organized turbines for very low and varying head, and develop a turbine plan to maintain energy production, lessen construction, preservation and running costs. All of this work has been done with one motto: to generate as much power as possible at the cheaper possible costs-and should be like an environmental friendly and feasible way (Tedd etal., 2008).
Fig.3. storage of water in the reservoir above the sea level (Tedd etal., 2008).
STRUCTURE OF WAVE DRAGON
Wave dragon is moored in reasonably deep sea water as like a ship, to make advantage of the ocean waves before they lose energy gained as they arrive at the coastal area. Where wave dragon is designed and implemented with open air - chamber. Where, a pressurized air system is present and makes the floating height flexible. In addition, the open air-chambers minimizes the activities of the main body structure, as the wave produce pressure on the underside of the body compresses air instead of moving the body (Beels, 2009).
Fig. 4. Normal view of wave diagram (Beels, 2009).
SEAWAVE SLOT-CONE GENERATOR
The Sea Slot-cone Generator actually is a wave power converter of the type of overtopping. The arrangement includes of a set of reservoirs, which are arranged like everyone on the above of each other on top of the indicate water point in which the incoming waves water is kept temporary. Each reservoir consists of specially structured low head hydro-turbines which are useful in transforming the potential energy of the temporarily stored water into energy. Depending on the wave height of incoming wave, overtopping water is kept in different selected basins. Here, the role play by the Turbines on the power take off of the device is an important and smooth. The key potential strength of the machine consists on sturdiness, cheap cost and the ability of being integrated in breakwaters (Margheritini etal., 2008).
During the overtopping events, the energy absorbed from a given level of water in the reservoir is in directly proportion to its altitude above the mean level of turbine head.
Fig. 6. Diagram representation of multistage in SSG device (Margheritini etal., 2008).
In this wave energy convertor the water stored in the reservoirs go on its way backwards to the sea or ocean with the help of a turbine which spinning it, and generates power. The interesting innovative subject of the Multi-Stage Turbine is been developed and the design of the structure include a set of turbines depending up on the set of reservoirs spread out intentionally inside each other, running a common generator through a common general shaft. Concentric ducts are used to connect each of the runners to one of the reservoir. Main advantage for multi stage technology is different heights of water head, therefore this process results in a higher efficiency (Vicinanza and Frigaard, 2008).
SEAREV WAVE ENERGY CONVERTER
The Searev wave energy generator device is device of floating type.This encloses of weighty straight-axis wheel, which behave like interior gravity orientation.The horizontal-axis wheel mechanically behaves like a pendulum because centre of gravity is being off-centered. The rotational movement of this pendulum wheel acts comparative with hull, which ON a PTO hydraulic; mean it works as an electric motor into movement. Main benefits about this design is, all the components in action are protected as of the stroke from water of sea inner side of a clogged hull, where the option for pendulum wheel involves neither stop nor any protection system restricting the stroke (Babarit eta., 2005).
Fig. 6. Searev schematic representation (Babarit eta., 2005)
This movement is useful to nourish an electric generator with the help of transformation in series levels.
ANACONDA WAVE ENERGY CONVERTER
Anaconda wave energy converter is a snake like 200 m rubber tube with a hydraulic turbine, drives an electric generator which could produce 1 MV of wave power. This Anaconda wave energy converter has a distensible tubes made with rubber which is subjected to anchored to the depth of 50m into seabed, floating just below the water surface according to the activities of wave, so that to face waves head-on always. A bulge waves is created by the movement of waves in the inner side of the rubber tube, where it is filled with the lower pressure water of sea. Before hitting to the hydraulic turbine, the bulge waves travel lower path along with the length of the rubber tube at the stern which creates power. As it is made up of rubber so their only few moving parts which has to be maintained well, so it can say that it is more resilient than the other wave energy converters also been proved that the potential of Anaconda wave dragon can bring wave energy price lower to £0.09/kWh when compared to the general convertor which has a potential of £0.25/kWh. Recent study on Anaconda states that this generating device can generate power off in any type of coast with wave strength more than 25kW/m and it is envisaged to be set of arrangement with 20 or more than 20 machines which, provides more than 20 MW. UK government is planning to launch this fully modified prototype by the year of 2014.
Fig. 7. General view of anaconda concept (Chaplin etal., 2007).
The research on Anaconda found that it has the potential to distribute penetrate reductions in the cost of wave power and that it could symbolize as the upcoming generation of marine renewable energy (Chaplin etal., 2007).
It is clearly seems that sea or ocean is a massive storage of energy in it with huge density, because indirectly it is like reservoir which stores energy in it that and we human beings are trying to extract it by using various technologies from olden years to present days, to get the power in most feasible way. Different types of prototypes were been designed according to their climatic conditions and sea conditions by the several countries who are in need and those who are aware of global warming. In the above discussion only few well known and efficient prototypes were discussed, just to have a basic view or knowledge. Each prototype had own principle of working and specialties to extract power from waves but main motto of each country, who are working on any kind of renewable energies is to extract the power in a cheaper cost by reducing the cost of device and to get power in more cheaper and cheaper level. The most preferable technology in all wave power technologies is Pelamis wave power technology, because it has a capability of 750 KW for each converter. The capacity of this converter in Portugal is 2.25MV and in Scotland it's been planned for a capacity of 3MV (http://www.ewi.uni-koeln.de, 2010). For developing economy of their country and to reduce the power cost in future. It's the known fact that all non-renewable resources are getting extinguish as global warming increases. We know that most needed thing in human life is power which plays a vital role in a whole day. In a recent review of European countries it is been notified that 20% of coastal line is in UK region and being used for wave power.
My conclusion from this review is that the main evaluation of impact of this technology in all over world will be in such a way that the close-relation and co-operation would lies in the unions of world. As, UK is also one of the parts of this European Union, and it should be more helpful to the remaining countries in Union in present and next generation because, all they need is power and UK has an upper hand in coastal lines. So, literally this co-operation will boost up the technologies with each other help in need of power with the past achievements and experience. May be next generation will get more success by getting more advanced knowledge in this concept with the help of previous technologies, as we are doing in present generation. All these vast technologies of renewable in UK and other unions all over world, who are having resources to develop power, would build a shield of economy to become a powerful nation in technologies in next upcoming generations.