renewable energy sources andré_alves

Upload: andre-alves

Post on 30-May-2018

218 views

Category:

Documents


0 download

TRANSCRIPT

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    1/26

    Brno University of Technology

    Renewable Energy Sources

    Energy of the Waves

    Work done by:Andr Alves

    Portuguese Erasmus Student

    Brno, April 2010

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    2/26

    Energy of the Waves

    Renewable Energy Sources 2

    Index

    1.Summary ...................................................................................................................... 3 2. Introduction ................................................................................................................ 4

    3. Wave Energy ............................................................................................................... 5

    4. History of wave energy ............................................................................................... 7 5. Wave Energy in Portugal ........................................................................................... 9

    5.1. Future prospects in the Portuguese case ......................................................... 10 6. Technology Wave Energy Conversion .................................................................... 12

    6.1. Coastal Gadgets ................................................................................................. 12 6.1.1. Device oscillating water column (OWC) ...................................................... 13 6.1.2. Central European pilot of the island's peak ................................................. 14 6.1.3. Central LIMPET ............................................................................................ 14 6.2. Device near the coast ......................................................................................... 15 6.2.1. OSPREY .......................................................................................................... 15

    6.2.2. CEO Douro ...................................................................................................... 16 6.3. Device away from the coast............................................................................... 17 6.3.1. Archimedes Wave Swing ............................................................................... 17 6.3.2. Pelamis ............................................................................................................. 18 6.3.3. Wave Dragon .................................................................................................. 18

    7. Environmental impacts associated with the conversion of wave energy ............. 20 7.1.Visual Impacts .................................................................................................... 20 7.2. Noise .................................................................................................................... 20 7.3. Disturbance of the environment ....................................................................... 21

    8. Barriers to development ........................................................................................... 23 9. Conclusions ............................................................................................................... 25

    10. Bibliography ............................................................................................................ 26

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    3/26

    Energy of the Waves

    Renewable Energy Sources 3

    1.Summary

    This text has as its primary goal to present and describe the key technologies thatenable the conversion of wave energy into electricity. In this work we will try to givesome idea of the history of wave energy, with particular emphasis on the Portuguesecase. The first part focuses his attention on a global perspective of wave energy, from1960 until the present day, while later shows the most relevant facts that are related tothe business of development of technologies for conversion of wave energy inPortugal. Given the nature of these technologies, others may arise, or not replacing theexisting ones, but the current state of development permits already outline a method of classifying and predicting their environmental impacts, and also discusses the mainbarriers to its development.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    4/26

    Energy of the Waves

    Renewable Energy Sources 4

    2. Introduction

    The challenges posed by the need to implement policies that ensure sustainabledevelopment are particularly relevant in the energy field. Increasingly we are faced with

    the need to find renewable energy a real and reliable alternative to conventional formsof electricity generation, responsible for serious threats to the environment. The legalobligations imposed by EU directives and the Kyoto Protocol only reinforce this need. The oceans, containing the biggest of all natural resources, is home to a huge energypotential, which can contribute significantly to the growing energy needs at a globallevel. The energy contained in the oceans may have different origins, leading todifferent classifications.

    The most relevant are undoubtedly tidal energy, resulting from the interaction of gravitational fields of the moon and sun, the ocean thermal energy, a direct result of sunlight, the energy of ocean currents, whose origin is in the temperature gradients andsalinity and tidal action and finally the wave energy, which results from the effect of

    wind on the ocean surface. The latter form of energy can be considered a concentratedform of solar energy, as this is that the uneven heating of the land surface, is responsiblefor winds. Once created waves can travel thousands of miles at sea with virtually noenergy loss. In coastal regions the energy density in this wave decreases due interactionwith the seabed.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    5/26

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    6/26

    Energy of the Waves

    Renewable Energy Sources 6

    conservative in the rates of conversion of available energy easily conceives that thisresource is an asset to Portugal, which is still unexplored.

    Portugal was also one of the pioneers in research and development of devices forwave energy conversion, because since 1977 that a group of Institute Superior Tcnico(IST), Technical University of Lisbon is dedicated to the topic, a group which he joined

    in another 1983 of the National Institute of Engineering, Technology and Innovation(INETI). The central European pilot of Pico Island represents the culmination of the

    joint effort of the IST, the INETI and some companies, such as EDP, EDA andEFACEC, as regards the implementation of technologies for conversion of waveenergy. Its historical importance is safeguarded securely by future generations of researchers and scientists. The constitution, in 2003, the Center of Wave Energy, aninternational nonprofit whose nature is directed at developing and promoting the use of wave energy through technical and strategic support to companies, proves the growingof interests in this area.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    7/26

    Energy of the Waves

    Renewable Energy Sources 7

    4. History of wave energy

    Although not always associated with the concept of useful energy, the energypotential of ocean waves has been recognized since antiquity, being the eighteenthcentury the first proposals for the harnessing of wave energy. Table 1 seeks to outlinethe important facts from the decade 1960, with the first name that it is the figure of themaster Yoshio Masuda, who from the mid-1960s, Japan started the development of maritime buoys powered by wave energy.

    Principles1960 Mid Buoys Commander Y. Masuda

    FinalPrinciples Salter proposed to produce large-scale power

    1970 Mid Program United Kingdom (2 GW)FinalPrinciples Linear theory in the frequency domain

    1980 Mid First pilot plants in Japan and NorwayFinal Linear models in time domain of WEC'sPrinciples Linear analysis in the frequency domain sets of WEC's

    1990 Mid Models 'Wave-to-Wire' WEC'sFinal Nonlinear hydrodynamic analysis of WEC'sPrinciples Sea trials of several pilot plants

    2000Mid Technology DemonstrationFinal Demonstrate the economic viability of the technology

    Table 1 - Highlights the history of the Waves

    It was the period that followed the crisis in the oil market of 1973 that the energyof the waves appeared in the programs research and development (R & D) in the UK,and the work of Salter pointed to the potential energy available in waves (Salter,1974). The immediate result of this interest culminated in the emergence of variousactivities in several countries (Sweden, Norway, Denmark, Portugal, Ireland, Japan andUSA), emphasizing the British program that would prove too ambitious (the originaltarget envisaged the installation of plants amounted to 2 GW), which may be consideredresponsible for the abandonment almost entirely on government support for thisprogram in the mid-1980s.

    The Japanese experience has diverged considerably from the UK program, sinceresearch has the option of the commander of the buoys Masuda for Kaim, a shipdemonstration which included 13 pneumatic chambers coupled to the generated electric40-50 kW, with the principle operation of the CAO. Oscillating WaterColumn (Oscillating Water Column). Tests of Kaimer occurred in 1978 and 1979,followed by the construction of a central CAO (40 kW) in Senza, circa 1983. At the endof this decade has been built yet another central CAO (60 kW), this time on a

    breakwater at the port of Sakata. The program also includes a central Japanese floatingCAO: Mighty the Whale.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    8/26

    Energy of the Waves

    Renewable Energy Sources 8

    The Norwegian approach was similar, resulting in the construction of two plantsof different types: one of CAO of 400 kW (Kvaerner) and a boiler of overtopping calledTapchan (Tapered Channel). The first has since been destroyed due to a storm, and thesecond state in operation for several years. Since the beginning of the 1990s that otherpilots were built in central India, China, Portugal and United Kingdom, with powers

    ranging between 20 and 500 kW, and all type of CAO (except Tapchan). It is notsurprising that the central CAO, including coastal, are therefore the most studied,although there are extensive publications on the performance of these plants, which canbe seen as an indicator of expectations about income from core were not affected. Thisis not surprising, especially in older plants that have not benefited from the advancedsimulation and control project which is at present available. It should not be overlookedthat Japan, China and India have a low energy resource, which necessarily leads to lessfavourable conditions for the conversion of wave energy.

    The European Commission's support is evident since 1991, starting withpreliminary studies on the energy of waves (1991 and 1992) which was followed since

    1993 a series of projects under the umbrella of JOULE. Among those, the projects thatled to the creation of a European Atlas of the wave energy resource ("Atlas of Wave Energy Resource in Europe") and the construction of two power pilot CAO, one onPico Island and another on the island of Islay, Scotland. In 2003, the Commission hasfinanced the construction and testing of a plant scale of 1:4 Wavedragon. Since 1993the Commission sponsored an international conference of wave energy (Edinburgh1993, Lisbon 1995, Patras 1998, Aalborg 2000 and Cork 2003) which has beenagitating for further R & D in this area in Europe. This action was complemented in2000 to 2003, the activities of a European network of wave energy (European Wave

    Energy Network), which involves 14 teams from universities, research institutes andcompanies from more active in the field of the use of wave power . This Europeannetwork will be expanded in the next three years with a Coordinated Action on OceanEnergy, which involves 51 partners, half of which are businesses. At the same time ithas a European research network on wave energy, also funded by the EuropeanCommunity, involving 11 partners, of which two are companies.

    The late 1990s and beginning of the new century saw the appearance of fivepilot plants four different technologies, which were tested in 2004 at sea. The fact thatfour of these pilot plants are owned by companies should be viewed as an extramotivating factor, and as a sign of progress towards maturity of the technologies of wave energy. The data from these pilot plants are fundamental to the development of systems, because they constitute, for example, tools to validate the models

    performed. Another step is no less important for demonstrating the economic viabilityof technologies that will follow a process similar to that of other technologies, such asthose inherent in the conversion of wind energy.

    Recently, Portugal had the first wave park in the world. The Scottish companyOcean Power Delivery (OPD) has made the assembly of three Pelamis machines nowcalled (name of a sea snake) who settled in what is the first park in wavesworldwide. The client is a renewable energy company Enersis, based in Oeiras, and thatpark will be located off the Aguadoura, slightly above the Povoa de Varzim.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    9/26

    Energy of the Waves

    Renewable Energy Sources 9

    5. Wave Energy in Portugal

    The problems associated with the wave energy are particularly relevant in thePortuguese case. Portugal was one of the pioneer countries to study this issue and stillhas an active contribution in the international arena, which should be regarded withsome surprise and that is directly related to the energy characteristics of waves off thePortuguese coast.

    Among the usable energy of the waves is that in recent years has been the mostactive research and development (R & D). Portugal is one of the pioneers, with activityin this field since the seventies, having participated and coordinated large projects withcurrent European construction of prototypes. Led the project on the island of Pico andparticipated in projects LIMPET, the island Islay (Scotland), and Archimedes WaveSwing' (AWS), offshore of Viana do Castelo. Also highlighted the leadership of Portugal in preparation of the European Atlas of Wave Energy, related to systemresources offshore.

    Portuguese coastal regions, particularly the west coast of the mainland and theAzores islands, are among those that have better natural conditions, European and evenglobal level, for the harnessing of wave energy. The energy that comes along the 500km to the west coast is about 120 TWh / year. The conversion of just 1% of usefulenergy produced 1.2 TWh / year, which would correspond to an installed capacity of 550 MW, assuming a load factor of 0.25.

    Portugal has one of the few industrial-scale prototypes for the conversion of wave energy. On the island of Pico, Azores, the device CAO (oscillating water column)is the most developed and most successful among other devices installed in the area of the coast or near it. This device has 400 KW of installed capacity and produces about 1GWh / year of electricity. Portugal is a country that dominates the CAO plant

    technology and equipment, including conversion by air turbine. In the offshore regionof the Viana do Castelo AWS system in which the technology is essentially Dutch. Thisis a prototype corresponding to one of the few systems in use offshore. The productionof electricity is made from moving upward and downward, from a float that is activatedby the movement of waves.

    As the plant to be installed in Povoa de Varzim, already in top working order,have the power of 24 MW and will use Pelamis technology. The study developedimpact assessments on the operation of systems of 60 kV north of Porto and theNational Transmission Network for various scenarios of operation. The technologyPelamis resembles a snake dangling articulated as the waves pass through its length.The swing joints permits operation of electricity generators and energy is then collectedby a submarine cable and sent to earth. It is planned that 1 km2 of ocean is filled withPelamis generators providing a power of 24 MW, for example can feed 20,000homes. Off the coast of Povoa de Varzim machines will be installed energy use is about5 kilometers of land. The waves offshore energy can offer a technically more stable thanthe wave of surf or even those generated by harnessing the wind. This energy is then fedto a substation to interconnect the electricity grid via a submarine cable.

    Among the projects of harnessing wave energy in Portugal account for theinstallation of a central wave energy on the new breakwater construction in Foz doDouro. The Central of Foz do Douro entail an investment of seven million Euros andwill have an installed capacity of 1 megawatt (MW). At the end of the first year of operation, it is expected that the center of Foz do Douro to produce 1.2 million kilowatthours of energy consumption equivalent to 500-600 families.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    10/26

    Energy of the Waves

    Renewable Energy Sources 10

    5.1. Future prospects in the Portuguese case

    The growing interest in renewable energies in Portugal, particularly on waveenergy, led to creation of an international nonprofit association whose nature is directedat developing and promoting the use of wave energy through technical and strategicsupport to companies : the Wave Energy Centre. This expression of interest arises in theculmination of twenty-five years of R & D in Portugal, taking the country in this timeinterval ensured a leading position. The international interest is also growing:Companies like Wavegen and Ocean Power Delivery in Scotland, to spokes inDenmark, Teamwork Technology in the Netherlands, Ocean Energy in Ireland AquaEnergy and Ocean Power Technology in the United States of America and Energetechin Australia work in order to extract energy from ocean waves. Fruit of the activity of some of these companies and also from several institutions for R & D, Europe has atpresent several pilot plants of different types, which are being tested at sea or at highstage of development. Two of these stations, one coastal (Pico ) further offshore (AWS),are in Portugal. The so-called offshore systems are particularly suited for the extractionof large-scale power through its installation in parks (similar to wind power), so arethose where recent research has focused his attention, although the technology is themost studied Oscillating Water Column for application in the coastline. The economicviability of these devices is also starting to be seriously considered. A recent document(PNEO, 2004) aims to draft a national strategy for wave energy. In this section we seek to highlight the strengths and weaknesses of the current national situation on this theme,highlighting the opportunities offered and the difficulties in achieving theobjectives. The strengths and weaknesses in order to implement these technologies inPortugal are generally schematized in Table 2, and briefly discussed below.

    Strengths Weaknesses

    Existence of market Risks inherent a technology indevelopmentScientific capacity Limited availability of

    Portuguese companies forinvestments in this area

    Technological andindustrial capacity

    Unfavourable imagethe first systems

    Favourable government policy Technical barriers(Aggressiveness of theresource)

    EU requirements in the field of renewable energies

    Complexity and delay of the licensingprocess

    Table 2 - Strengths and weaknesses of the Portuguese case (PNEO, 2004)

    Consider first the strengths. As the first element of that column of Table 2 wehave the existence of the market. From the internal point of view this market because

    there is an initial analysis of the bathymetric depth of 50 m shows off the western coastof the mainland Portuguese there are about 250-350 km in length which can be used for

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    11/26

    Energy of the Waves

    Renewable Energy Sources 11

    quarrying of energy wave energy, because they do not fit into the status of areasreserved for other purposes (protected areas, shipping, military activities and recreation,protection zones for submarine cables, and not collide with the activity of fishing). Notethat the systems will normally be installed offshore at depths between 50 and 80 m,depending on local conditions, such as the existence of zones or corridors of fishing and

    the type of bottom (geology and bathymetry). Even taking conservative criteria(assuming, for example, that 15% of the energy available for offshore systems isconverted into electrical energy and assuming that will be viable only for installation of systems 250 km of coastline) arrived at the value of 10TWh/year representative of introduction of electricity into the grid which corresponds to about 20% of nationalelectricity consumption. If we assume further that the load factor is 25% we obtain asvalue of the power to install 4.5 GW for that stretch of coast, value that should becompared with the approximately 3.75 GW of wind power by 2010 to install and can beregarded as the national potential. From the standpoint of the foreign market studiessuggest that wave energy will be economically viable energy resources in areas withgreater than 15 kW / m (average annual flow of energy carried in each meter of wavefront), a value that is supplanted by natural conditions in Portugal: 45 kW / m at sea anda little less 30 kW / m at depths of about 50 m. Another important factor is the waveenergy resource to be attractive in a very large number of sites on a global scale, whichgives an exceptional opportunity for anyone who comes to mastering technology. Another strong point to stress is related to government incentives, which in this means,for example, the rate attributed to wave energy (0.225 / kWh), which is extraordinarilyfavourable worldwide. Regarding the weaknesses highlight the risks inherent in adeveloping technology, which requires a high financial burden to the economic viabilityis reached, the limited experience of Portugal in technological innovation and technicalbarriers associated with the nature of resource itself. The relative strengths andweaknesses of these are of course subjective, and only time will tell which aredominant.

    The opportunities for the country are so diverse, and go through the productionof a significant amount of electrical energy by a renewable source by creating jobs,developing the economy in terms of a technology and the global impact of anoffshore technology with application potential in other ocean resources, and theopportunity for domestic companies as suppliers of components, equipment andservices. The definition of a National Strategy for the area of the Wave Energy isessential for the short to medium term, opportunities and strengths above are rented, andrequires the definition of supporting measures that support it. Also highlighted theinvolvement of a Portuguese company independent power producer, the ENERSIS in

    two of the current technologies, the AWS and the Pelamis, which may allow short-termtest of its kind in central waters.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    12/26

    Energy of the Waves

    Renewable Energy Sources 12

    6. Technology Wave Energy Conversion

    After decades of research and development arise at present different solutionsthat meet the technological challenge that is presented to extract energy from

    waves. These technologies are not competing today, that situation may change in thenear future, as it will not be correct to say that these are the only solutions possible,given the increasing interest in this field and constant input of new ideas, businesses andother institutions in this area . It is essential to establish criteria for the classification of different technologies that could pass, like extraction technologies from other forms of renewable energy, the power of the devices. The classification criteria adopted in theoverwhelming majority of references relates to the distance from the coast of the deviceby grouping them in this way:

    Coastal devices (in English nomenclature: shoreline); Devices near the coast (near-shore);

    Devices away from the coast (offshore). The main difference between the devices near the coast and away from the coast

    is clear from the depths involved. In the first case the depths are typically less than 20 mand the devices will be laid on the seabed, while the second case 50 devices willfluctuate. Importantly, the scheme is more energy waves at depths of 50 m than atdepths of 20 m, having, by this hand, an advantage in putting them at depths greater.

    Another classification is plausible that this classification is associated with themode of conversion of wave energy into electrical energy (i.e., type of device).

    Thus we have three main classes of devices for converting wave energy, whichmay include:

    Oscillating water column, CAO (OWC - Oscillating Water Column); Floating bodies, may be absorbing point (Point Absorbers) or

    progressive (Surging devices); Overtopping (overtopping devices).

    6.1. Coastal Gadgets

    Coastal devices are those that are fixed or built from scratch on thecoastline. This proximity gives them immediate advantages such as ease of installation

    and maintenance, lack of large tracts of submarine cables and fastening systemscomplex, but they take them the possibility of enjoying the most powerful regimes of waves, characteristic of areas of great depth. In fact the effects of energy dissipation dueto friction (the result of interaction between wave and seabed) are manifested for depthsbelow 80 m and the associated breaking of the waves are dominant for depths below 10m, so in device has an average coastal available only between 25% and 50% of available resource for a device away from the coast. This limitation may be partiallylifted in the process of site selection for implementation of the device, looking for areaswhere there is a natural concentration of energy. Another important limitation relates tothe concerns at the level of environmental impacts (particularly in safeguarding theenvironment the device). Within the class of devices coastal one that stands out, thenumber of applications and the research that was targeted is that of devices oscillating

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    13/26

    Energy of the Waves

    Renewable Energy Sources 13

    water column (OWC), known in English nomenclature by OWC (Oscillating Water Column).

    6.1.1. Device oscillating water column (OWC)

    The devices of oscillating water column (OWC) basically consist of partiallysubmerged hollow structures, which are open to the sea below the free surface of seawater. The electricity generation process follows two stages: when a wave enters thestructure of the air that was inside it is forced through a turbine as a direct result of increased pressure in the "tube". When the wave returns to the sea air passes into theturbine again, this time in reverse, due to lower pressure inside the "tube". To takeadvantage of both these movements opposite the turbine used is usually the type Wells,who owns the property to maintain the direction of rotation regardless of the directionof flow. The group turbine / generator is responsible for electric energy production. TheCAO devices have been installed all over the world. For example in 1985 a 500 kWdevice was installed in Tofteshallen, Norway, having operated for three years, wasdestroyed by a storm in 1988 (White, 1989). In 1991 he was installed a prototype 150kW on a breakwater one Indian port (Ravindran et al., 1995). The data collected duringoperation make improvements allowed on site, thus resulting in the proposal to build 10such devices on the west coast of India, giving a power of 1.1 MW.

    Another very active program initially was the Japanese, with CAO devices to beinstalled at the port of Sakata in breakwaters in Kujukuri-Cho and still Haramachi,where he first rectifying valves were used in order to control the air flow to and fromthe turbine, allowing for stable production of energy. Please note that some of thesedevices (particularly those related to coastal structures and breakwaters) are consideredfixtures near the coast.

    Will then be shown the two examples that best illustrate current devices coastalCAO: Central European pilot of Pico island, Azores, and the central LIMPET on theIsland of Islay, Scotland.

    Figure 2 - Schematic of a central oscillating water column

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    14/26

    Energy of the Waves

    Renewable Energy Sources 14

    6.1.2. Central European pilot of the island's peak

    The pilot's European central island of Pico (hereinafter referred to as the centralpeak) appears as the culmination of the actions initiated in 1991 by the EuropeanCommission under research and development on the subject of wave energy. The actionhad, initially, the selection of a site in one of the EU countries to implement the firstpilot central European type. The Azores archipelago has very favourable conditions forexploitation of wave energy, either by their location in an area where there is a highenergy resource, either by the absence of a continental shelf responsible for thedissipation of wave energy by bottom friction characteristic patent in the volcanicislands. The fact that the tidal range is small (less than half the amplitude in themainland Portuguese) was decisive for the final choice fell on Porto Cachorro, on thenorthwest coast of the island of Pico.

    Tests in the central peak began in the summer of 1999 and extended, withsignificant interruptions, until 2001, as a result of several deficiencies, especially thelevel of the auxiliary mechanical equipment. You are currently underway to recover thispower, under the activities of the Center for Wave Energy.

    The teachings, lessons and experience gained in this project are a valuablecontribution to the development of future wave power stations in Portugal.

    Figure 3 - Central oscillating water column of Pico Island

    6.1.3. Central LIMPET

    The central LIMPET (acronym for Land Installed Marine Power EnergyTransmitter) emerged as the natural continuation of the success of a prototype 75 kWthat was installed on the Scottish island of Islay, which is located centrally. The centralLIMPET is the first device for converting wave energy to be exploited commercially inthe United Kingdom (operational since November 2000). It was developed by a Scottishcompany, the Wavegen (the same who supplied the mechanical equipment to the centralpeak), together with Queen's University of Belfast, the European commission andCharles Brand Engineering. With a nominal power of 500 kW at center can supplyelectricity to about 400 dwellings. Its location allows you to receive about 20 kW permeter of wavefront incident, slightly above the equivalent to the central peak.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    15/26

    Energy of the Waves

    Renewable Energy Sources 15

    Figure 4 - Views from the central LIMPET (courtesy Wavegen)

    It is noted that the island of Islay presented himself as a candidate naturalimplementation of this power (and the prototype that preceded it) not only by naturalconditions with respect to the wave climate, but also easy access to central, because asignificant portion of electricity consumed is imported from Scotland (not generated onthe island) and also the local population against renewable energy, with particularemphasis on wave energy. Like the central peak, but even more important, the costsrelated to construction of the structure were responsible for the enhancement project andis yet capable of massive reductions in the future.

    6.2. Device near the coast

    As already mentioned the concept of "closeness" of the coast must be interpretedin terms of depth seen in areas more or less from shore. Thus the CAO type devicesinstalled in breaking seas, can be lumped into this category, as a breakwater or a pier isnot a natural shoreline (will not be correct to speak well in coastal devices). Theincorporation of devices these structures have additional advantages because theyalready exist in many cases and an additional structure may even enhance its originalpurpose (e.g. coastal protection). Given the introductory nature of this text will bedisplayed one type device that CAO can be broadly encompassed in this category,

    OSPREY, which is also referred to the center to build a breakwater at the mouth of theDouro.

    6.2.1. OSPREY

    The OSPREY (Ocean Swell Powered Renewable Energy) was developed in themid-1990s by the Scottish company Wavegen as an isolated system of CAO, to beplaced near the coast, in waters 20 m deep. Consisted of a double-walled metalstructure, which should be towed to the site, which would be submerged by the filling of its cavity wall with dense material, it being understood in the sea. The occurrence of anaccident during the sinking led to discontinuation of the project. There are plans to

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    16/26

    Energy of the Waves

    Renewable Energy Sources 16

    revive this project, involving an offshore wind turbine to one of these plants (Figure 5).

    Figure 5 - Model with the inclusion of OSPREYfor wind turbine use

    6.2.2. CEO Douro

    The CEO (Center of Wave Energy) Douro results from a proposal submitted bythe Consulmar PRIME IDEA program, which is involved in the Center of Wave Energyamong others. The project aims to develop and implement CAO in a central pier head of Foz do Douro (see Figure 6). The participation of the Center for Wave Energy passes

    the tests in laboratory wave tank (model specification and testing, monitoring andanalysis of test results), specification of primary energy production equipment (turbo-generator group) and evaluation annual production of energy.

    Figure 6 - Preview art from the jetty at the mouth of the Douro

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    17/26

    Energy of the Waves

    Renewable Energy Sources 17

    6.3. Device away from the coast

    The last class of devices for converting wave energy is considered the mostrecent (hence these devices are sometimes referred to as third generation) and one thatallows them to benefit from more powerful wave regimes, typical of areas with a highdepth. Such schemes entail a technological challenge yet higher. To be able to extractthe maximum energy possible for these devices need to be at (or near) the surface, thusrequiring mooring systems (flexible or rigid) and submarine cables to transfer land tothe electricity produced. Costs and losses associated with this transfer are outweighedby increased "production" of energy, thereby increasing the ratio Energy Produced / Associated Costs (ETSU, 2001). The generalized concept at present is to implementseveral provisions of parks where the purpose is the production of electricity on a largescale. Will be presented in detail three cases (Archimedes Wave Swing, Pelamis andWave Dragon) and also those others deemed relevant. It is noteworthy that these threedevices in different ways to convert energy from waves, so it will be given on a case, abrief description about the device type and mode conversion of wave energy.

    6.3.1. Archimedes Wave Swing

    The Archimedes Wave Swing is a device for converting wave energy of theclass of floating bodies (absorption point), developed by Teamwork Technology(Netherlands), and its development was started in 1994. This system, schematicallyrepresented in Figure 7, consists of two hollow cylinders, placed one upon another,within which there is air pressurized to a pressure such that it balances the weight of the

    upper cylinder (float) and the water column outside it supports. With the passage of thewave outside pressure varies, being higher on the crests and smaller armholes,producing a vertical oscillatory movement of the float on the base. This movement isused to drive a linear electric generator that produces electrical energy transmitted by anundersea cable to a ground station, where the energy is transformed so that it can beinjected into the mains. With a diameter of 10-15 m, much smaller than the wavelength(150 m), the AWS can be considered as an absorption device off.

    Figure 7 - Principle of Operation Figure 8 - Central AWS pilot waterthe AWS Portuguese

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    18/26

    Energy of the Waves

    Renewable Energy Sources 18

    6.3.2. Pelamis

    The Pelamis is a device for converting wave energy of the progressive type,developed by Ocean Power Delivery Ltd (Scotland), founded in 1998 with the intentionof developing and commercially exploiting. The devices are progressive systems withan elongated longitudinal dimension of the order of magnitude of wavelength and arearranged in the direction of wave propagation in order to generate a pumping effectprogressive, associated with the wave passing through the action of a flexiblecomponent in contact with water. The Pelamis is basically a semi-submerged articulatedstructure composed of various cylindrical modules which are connected by flexible

    joints. The wave motion of the incident waves causes the oscillation of the cylindricalmodules around the joints that unite them and thus the pressurized oil to be forcedthrough hydraulic motors, which in turn trigger electrical generators that produceelectricity. The Pelamis is designed keeping in mind its implementation in parks, so it isnot surprising that the energy extracted from all modules (three on each device) bewithdrawn and sent to shore via a single cable, which is particularly relevant if we havea large number of devices present. Other important variables in the design of thePelamis was the first attempt to use existing components in the offshore industry, as itwas the understanding of the company once it becomes clear that the device is feasiblethat the same industry will produce more efficient components and a cost remarkablylower than the present, and moreover the survival of the device, which was identified asa key parameter in the process of development, even on a priority attempts to improvethe efficiency of energy conversion.

    Figure 9 - Pelamis

    6.3.3. Wave Dragon

    The Wave Dragon is a device for converting wave energy that can be consideredas an overtopping device away from shore (offshore), setting an example of the onlyclass that until now had not been focused. The development of this device is beingundertaken by the Wave Dragon, an international consortium that includes businesses

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    19/26

    Energy of the Waves

    Renewable Energy Sources 19

    and institutions in Denmark, UK, Ireland, Sweden, Austria and Germany. With a powerrating that can range from 4 to 11 MW (depending on wave climate), the Wave Dragonwas the first device away from the coast in June 2003, introducing electricity into a gridin Nissum Bredning, Denmark, by pilot test of a central built at a scale of 1:4,5(installed power 20 kW). The system basically consists of two reflectors that focus the

    incident waves onto a ramp, a reservoir that stores water in the meantime climbed theramp and also a number of low head turbines, through which electricity isproduced. The Wave Dragon can be likened to a floating mini-hydro, as its operatingprinciple is at all similar to a conventional hydroelectric.

    Figure 10 - Wave Dragon

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    20/26

    Energy of the Waves

    Renewable Energy Sources 20

    7. Environmental impacts associated with the conversionof wave energy

    The implementation of devices for converting wave energy may have a widerange of environmental impacts, some of which are beneficial. Knowledge of theseeffects in the case of devices for converting wave energy is limited, since there are atpresent, units or full-scale prototypes with a time interval in operation have to light withthe necessary rigor all the implications entry into the surroundings. The analysispresented here follows that made by Thorpe (2001) and presented in De Vries (2000)and the report of WaveNet (2003), which coupled with the experience to other forms of renewable energy, including the placement of wind turbines off the coastline, isassociated some experience with some devices (highlight is the first prototype installedon the island of Islay, Scotland). The environmental impacts are certainly specific toeach site, whereby the definition of their tolerability will also vary from place to place.

    7.1.Visual Impacts

    The visual impact is very variable depending on the type of device. It may bevirtually nil in the case of the devices away from the coast or in the case of significantcoastal devices. Let us first examine the devices away from the coast: the case of beingtotally submerged their visual impact is nil, and even if they are only semi-submergedon its distance from the coast is high enough to minimize this impact. It may however

    have some impact on the visual signalling devices, when visible from earth, resultingfrom the demarcation of the area occupied by devices. Necessarily have to be structureson land for transmission of electricity to the grid, and these always have a yes that isimportant to minimize the associated impact. Devices near the coast are more likely tobe responsible for a greater visual impact, which can however be minimized throughintegration of coastal protection structures such as jetties or breakwaters. Theimplementation of coastal devices should, in principle, in areas of high energy density,which typically are not suitable for recreational purposes, thus not interfering with thistype of use. It should be noted that independent studies conducted in the UnitedKingdom show that the visual impact is always smaller than that associated with theequivalent situation for the technologies to convert wind energy (WaveNet, 2003).

    7.2. Noise

    The environmental impact associated with noise is often overlooked but can beconsiderable. For example, the central pilot 75 kW of CAO on the island of Islayproduced in a calm day, audible noise is about 200 m. Hopefully one day of rough seanatural noise of the waves and wind is similar to the noise from the operation of acentral energy of the waves of the type of CAO, provided that adequate systems areused for noise suppression. With respect to systems far from the coast the impact onhumans is nil. As the sound propagates to greater distances underwater, the noise causedby devices to extract energy from waves may, however, affect the navigation andcommunication systems of certain marine animals, particularly cetaceans. This issue

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    21/26

    Energy of the Waves

    Renewable Energy Sources 21

    deserves a closer study, although it seems unlikely that their negative influence on asignificant scale (note that the problem of interference with communication in case of adolphin is unlikely, because the associated frequency is particularly high whencompared with the emitted the devices). Even though the influence of navigation andcommunication systems of animals is not significant, special attention should be given

    to prevent the installation of parking devices constitutes a physical barrier to themigrations of species, which incidentally turns out to be safeguarded for reasons designand installation, due to the distances required between the devices.

    7.3. Disturbance of the environment

    As already mentioned one of the major environmental impacts associated withthis type of technology is related to the interference they cause in the environment thatare inserted into the phases of construction and installation, although some of thesesystems in the construction phase is not carried out in site. While these concerns are notunique devices for extracting energy from waves, should be taken into considerationwhen planning the implementation of this technology. The build in modules, a shipyard,you can minimize the immediate impact but in certain coastal structures, as was the caseof central LIMPET may be required considerable changes in the coastline. Although notyet lawful all the possible effects that the introduction of these devices can cause themarine environment, it is expected that changes to the regime itself waves are due totemporary disturbance in the living standards of some species. There should be changesnot only in wave climate but also in the sea currents in the tidal regime and patterns of

    mixture of microscopic species that constitute the base of the food chain for manymarine species. For devices away from the coast, and when placed in parks, is toprovide a reduction of wave action in coastal areas nearby, so it may be an advantage asa disadvantage, depending on the use of these areas. In these devices one other caremust be taken, and this related to the anti-corrosion coatings and the type of protectionused to prevent the build-up of marine organisms. These products were toxic nature of the past and may in the long run be detrimental to marine species. The experience of theshipbuilding industry shows that can be used non-toxic products without environmentalconsequences.

    On the problem of pollutant emission by producing electricity these devices donot emit any pollutant, which does not mean that they are zero emissions throughout its

    life cycle, as seen in the installation process, by example, techniques of extraction of wind energy (Mendes et al., 2002). The implementation of these technologies involves:

    the extraction and movement of land (where the devices coastal); Processing equipment;

    the generation and transmission components; Construction and the operative mode of the device; Decommissioning; Processing of waste arising.

    In terms of emissions of pollutants the most critical phases are those that involvehigh energy consumption, such as the manufacture of components, while at the otherextreme actions involving the transport of materials. It is also expected that all stages

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    22/26

    Energy of the Waves

    Renewable Energy Sources 22

    are an order of magnitude lower than the manufacturing of the components of the devicewith regard to energy needs. Phases such as decommissioning and waste treatmentresult (material recycling, etc) are still neglected, given the early stage at whichtechnology is. In any case the magnitude of emissions in all these phases is practicallyzero compared with the conventional options for producing electricity. In conclusion it

    is noted that all these environmental impacts are not equated by the current legislation,so that if confirmed the economic viability of devices for extracting energy from wavesmust be taken swift actions in legal terms.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    23/26

    Energy of the Waves

    Renewable Energy Sources 23

    8. Barriers to development

    There is a potential energy recognized and considered extremely attractive, thereader may at first sight, surprising that the technologies to convert energy from waveshave not reached yet, like its counterpart wind, a level of widespreadcommercialization. The barriers to the development of these technologies are of different types and can be encapsulated in four general categories:

    a. techniques; b. conflicts of interest; c. administrative and legal; d. Financial.

    With regard to these technical barriers are related to characteristics inherent inthe energy resource, the most important being:

    the irregularity of the amplitude, phase and direction of the waves, with a furtherchallenge to try to maximize energy capture in a frequency range of the incidentwave;

    the efforts that the structural devices are subject, which in extreme storms mayreach one hundred times the load averages;

    the very mechanism inherent in the electric generators, which require afrequency much higher than the incident wave;

    The technological challenges are surmountable, and the more relevant questionconcerns the cost associated with these solutions, because in a market economy thisparameter is dominant. Another category of barriers to the development of devices forconverting wave energy is related to possible conflicts of interest, because the areas of implementing these technologies can have other uses. Within this category we can alsodefine two types of conflicts: those posed by overlapping uses and lifted a ban orrestriction on use of the area.

    Thus we have:

    1. Possible areas of overlap of uses: Fishing areas; Pits of materials; Recreational areas and leisure; Areas of archaeological interest.

    2. Areas of restricted or prohibited: Areas that intersect major shipping routes; Military training camps; Areas in the vicinity of other relevant structures, coastal or distant from

    the coast (Bridges, ports, oil platforms, offshore wind farms, ...); Traffic areas of submarine cables or pipelines; Nature reserves.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    24/26

    Energy of the Waves

    Renewable Energy Sources 24

    1. the fisheries question is what becomes most relevant (in the case of thedevices away from the coast) and should be taken some preventive measures, forexample by establishing an open dialogue with the authorities or the communitiesinvolved before the project achieved, taking into account different fishing gear and

    practiced their area of activity.In the Portuguese coast the depth of installation of parks offshore wave energy isgenerally far enough from the coast not to interfere with the fishing and close enough tothe coast does not reach the 6 mile distance from which is allowed industrial fishing.For example it makes no sense to put one or more devices for converting wave energyinto areas already identified as areas of fishing or natural ponds. A query to multipleentities must be made in this light. It will be necessary to demarcate the areas where thedevices, which broadens the exclusion zones and increases the likelihood of otheractivities might be affected. Moreover the influence zones of recreation and leisure canbe beneficial, particularly in the case of offshore devices. In this case creates a zonedownstream of that, in principle, is more sheltered, especially in terms of sea waves,

    which can promote various activities (windsurfing, sailing in small boats).2. Finally in February. The main effect is related to the influence on the

    navigation, once again particularly relevant for the devices off the coastline. These mayrepresent a hazard to navigation because the freeboard (distance between water leveland the top cover of the device) is small, which can impede their detection (visual andradar), that problem does not arise if the devices are submerged. This question, whichcan assume larger proportions in the case of parking devices, can be circumvented bycareful control of nautical charts and proper signage. It should be noted that, in a sense,a wave energy park may even increase the safety of navigation by creating theinfrastructure for surveillance and intervention.

    It is also worth noting that should be avoided placing devices in the area of access to ports. A final comment for the other categories of barriers to development: theadministrative concern with issues related to licensing agile anything that involvesmany ministries and public institutes, and making the field of harnessing the energy of waves unattractive to investment, while the legal details relating to access to thenetwork, constraints in energy supply and power purchase tariff.

    Finally, the financial barriers are related not only with the selling price of electricity but also with strategies to support projects such as funds or special loans fortechnological innovation projects. The development of support schemes are vital to astage where the technology is still in the demonstration.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    25/26

    Energy of the Waves

    Renewable Energy Sources 25

    9. Conclusions

    Portugal has very favourable conditions for the exploitation of wave energy. Itwas one of the pioneer countries to study this issue and still has a contribution in theinternational arena. The country with the need to reduce greenhouse gas emissions andreduce energy imports, with the production of energy through waves contributedsignificantly to this reduction. Consequently, the production of wave energy researchand bring opportunity for job creation and high export potential worldwide. Althoughthere is still significant industrial experience in this area, there are four differenttechnologies to extract energy from waves with prototypes to be tested at sea: theOscillating Water Column (OWC), the Pelamis, the Archimedes Wave Dragon andWave Swing (AWS ).The Central Oscillating Water Column system is the mostinvestigated, having been built several plants worldwide. It is a coastal system that isparticularly suitable for integration in coastal protection structures. Currently there aretwo such pilot plants, one in Scotland, the Central LIMPET, Central and Pico in the

    Azores. The remaining devices are offshore systems are completely submerged.The environmental impacts associated with the conversion of wave energyshould be minimal. In environmental terms, the direct impact is almost nil, since thetechnology in question does not use harmful substances. In visual terms, structures,usually slightly raised the water line, will be installed at a considerable distance fromshore and already out of sight from land. Those plants will be installed outside thechannels of access to ports or to fish and far below sea routes, so it will not causesignificant adverse impact on navigation.

  • 8/9/2019 Renewable Energy Sources Andr_Alves

    26/26

    Energy of the Waves

    10. Bibliography

    o file:///C:/Documents%20and%20Settings/User/My%20Documents/ondas2/sa_co

    sta_ondas_ENERSIS.pdf

    o file:///C:/Documents%20and%20Settings/User/My%20Documents/enrgias%20d

    as%20ondas/centro%20d%20energias%20das%20ondas/associatesp.htm

    o file:///C:/Documents%20and%20Settings/User/My%20Documents/Os%20meus

    %20ficheiros%20recebidos/icon.bmp

    o file:///C:/Documents%20and%20Settings/User/My%20Documents/enrgias20das

    %20ondas/Cruz.pdf

    o http://www.acre.murdoch.edu.au/refiles/wavw/text.html

    o http://www.energiasrenovaveis.com/html/energias/ondas.html

    o http://www.iclei.org/efacts/ocean.html

    o http://www.wavegen.co.uk/resour.html

    o http://www.wave-energy-centre.org/pagesp/projectsp.html

    o http://www.waveswing.com/

    o http://www.inescporto.pt/noticias-eventos/nos-na-imprensa/povoa-ganha-

    energia-ondas

    o Oliveira, Alcino Sousa, e Solange Maria Almeida, Energias Renovveis Vila

    Real: UTAD, 2003. (Srie didctica. Cincias aplicadas; 223)