Oceanic energy

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  • Marine current turbines work, in principle, much like submerged windmills, but driven by flowing water rather than air. They can be installed in the sea at places with high tidal current velocities, or in a few places with fast enough continuous ocean currents, to take out energy from these huge volumes of flowing water. These flows have the major advantage of being an energy resource which is mostly as predictable as the tides that cause them, unlike wind or wave energy which respond to the more random quirks of the weather system. The technology under development by MCT consists of twin axial flow rotors of 15m to 20m in diameter, each driving a generator via a gearbox much like a hydro-electric turbine or a wind turbine. The twin power units of each system are mounted on wing-like extensions either side of a tubular steel monopile some 3m in diameter which is set into a hole drilled into the seabed.
    The submerged turbines, which will generally be rated at from 750 to 1500kW per unit (depending on the local flow pattern and peak velocity), will be grouped in arrays or "farms" under the sea, at places with high currents, in much the same way that wind turbines in a wind farm are set out in rows to catch the wind. The main difference is that marine current turbines of a given power rating are smaller, (because water is 800 times denser than air) and they can be packed closer together (because tidal streams are normally bi-directional whereas wind tends to be multi-directional).
    Environmental Impact Analyses completed by independent consultants have confirmed our belief that the technology does not offer any serious threat to fish or marine mammals. The rotors turn slowly (10 to 20 rpm) (a ship's propeller, by comparison, typically runs 10 times as fast and moreover our rotors stay in one place whereas some ships move much faster than sea creatures can swim). The risk of impact from our rotor blades is extremely small bearing in mind that virtually all marine creatures that choose to swim in areas with strong currents have excellent perceptive powers and agility, giving them the ability to successfully avoid collisions with static or slow-moving underwater obstructions.
  • The "Swanturbines" design is different to other devices in a number of ways. The most significant is that it is direct drive, where the blades are connected directly to the electrical generator without a gearbox between. This is more efficient and there is no gearbox to go wrong. Another difference is that it uses a "gravity base", a large concrete block to hold it to the seabed, rather than drilling into the seabed. Finally, the blades are fixed pitch, rather than actively controlled, this is again to design out components that could be unreliable.
    http://www.darvill.clara.net/altenerg/tidal.htm
  • Stingray is designed to extract energy from water that flows due to tidal effects - tidal stream energy. It consists of a hydroplane which has its attack angle relative to the approaching water stream varied by a simple mechanism. This causes the supporting arm to oscillate which in turn forces hydraulic cylinders to extend and retract. This produces high pressure oil which is used to drive a generator.
    http://www.engb.com
  • From http://www.geocities.com/newideasfromtelewise/tidalpowerplant.htm
    The tidal activity in land is much smaller than that of in the sea because of its less flexibility and high density. With the help of a hydraulic system, it is possible to extract energy from land tidal activity.  When the tide occur, the top surface of the Earth will move up and down and  the body structure of the mechanism fixed on the top surface will also move up and down (see diagrams below). But there occurs a relative motion between the top surface of the Earth and the bottom of the supporting stand because of the density difference between the top and bottom (density will be less on the top surface), flexibility (elasticity) difference between the top and bottom (flexibility will be more on the top surface). The large two-way head piston is rigidly connected to the strong rigid-supporting stand and which is rigidly fixed in the bottom of the deep well.
    During the upward motion of the cylinder (assume that the relative movement between the top and bottom is about 1cm), as the large two- way head piston is remaining stationary related to the bottom, the inside volume of lower chamber will decrease and the fluid in it will experience a high pressure, that causes the fluid in it with a volume of  0.0824m3 to escape through the 32.3cm diameter cylinder (Sc4 - see.fig) provided on the body structure. Since there is a small piston 4(Sp4) which can slide through its small cylinder, the fluid will push this piston in 1meter and the one way  piston 2 (Lp2) connected on the other end will also moves 1meter. Since the diameter of the one way cylinder2 (Lc2) is 1meter then, the volume of the displaced fluid by Lp2 will be 0.785m3 and  this fluid will escape through 37.7 cm diameter cylinder 3 (Sc3). This causes, the  small piston 3 (Sp3)  and the small piston 2 (Sp2) with the rack slides through the small cylinder 2(Sc2) and small cylinder 3 (Sc3) in 7meter. As the rack  is meshing with the pinions P1 & P2, it will rotate and through the gear train of the required gear ratio the power will be transferred to the rotor of the generator; and by its rotation, electricity will be produced.
    Similarly, during the down ward motion of the cylinder, in the tidal-fall, the inside volume of upper chamber will decrease and the fluid in it will experience a high pressure that causes the fluid in it with a volume of  0.1m3 to escape through the 35.6cm diameter cylinder (Sc1 - see.fig) provided on the body structure. Since there is a small piston 1(Sp1) which can slide through its small cylinder, the fluid will push this piston in 1meter and the one way  piston 1 (Lp1) connected on the other end will also moves 1meter. Since the diameter of the one way cylinder1 (Lc1) is 1meter then, the volume of the displaced fluid by Lp1 will be 0.785m3 and  this fluid will escape through 37.7 cm diameter cylinder 2(Sc2). This causes the small piston 2 (Sp2) and small piston 3 (Sp3) with the rack, slides through  the small cylinder 2(Sc2) and small cylinder 3 (Sc3) in 7meter. As the rack is meshing with the pinions P1 & P2, it will rotate and through the gear train of the required gear ratio the power will be transferred to the rotor of the generator and by its rotation, electricity will be produced.
  • The construction of this barrage began in 1960. The system used consists of a dam 330m long  and a 22km2 basin with a tidal range of 8m, it incorporates a lock to allow passage for small craft. During construction, two temporary dams were built on either side of the barrage to ensure that it would be dry, this was for safety and convenience. The work was completed in 1967 when 24, 5.4m diameter Bulb turbines, rated at 10MW were connected to the 225kV French Transmission network. 
  • Blue Energy Power System - For large scale power production, multiple turbines are linked in series to create a tidal fence across an ocean passage or inlet. These are large scale, site specific, custom engineered energy installations which will vary in size and output by location. These structures have the added benefit as a transportation solution.
    Mega Power System - A scaled-up version of the Blue Energy Power System, the mega class is a tidal fence capable of producing thousands of megawatts of power. These tidal fences can be many kilometers long and can operate in depths of up to 70 metres.
    http://www.bluenergy.com/technology.html
  • The potential energy of a set of waves is proportional to wave height squared times wave period (the time between wave crests). Longer period waves have relatively longer wavelengths and move faster. The potential energy is equal to the kinetic energy (that can be expended). Wave power is expressed in kilowatts per meter (at a location such as a shoreline).
    The formula below shows how wave power can be calculated. Excluding waves created by major storms, the largest waves are about 15 meters high and have a period of about 15 seconds. According to the formula, such waves carry about 1700 kilowatts of potential power across each meter of wavefront. A good wave power location will have an average flux much less than this: perhaps about 50 kw/m.
    Formula: Power (in kw/m) = k H2 T ~ 0.5 H2 T,
    where k = constant, H = wave height (crest to trough) in meters, and T = wave period (crest to crest) in seconds.
  • Potential world-wide wave energy contribution to the production of electricity is estimated by IEA (International Energy Agency) to be between 10 and 50% of the world’s yearly electricity demand of 15,000 TWh
    A recent study by the DTI and Carbon Trust in UK is stating some 200,000 MW installed wave and tidal energy power by 2050 which with a load factor of 0.35 is resulting in a power production of 6 TWh/y. Independent of the different estimates the potential for a pollution free energy generation is enormous
    http://www.wavedragon.net/technology/wave-energy.htm
  • Another promising type of wave energy power plant is a shoreline-based system called the Tapered Channel (Tapchan).  The principle here is capital intensive yet has potential due to its ruggedness and simplicity.  A tapering collector funnels incoming incoming waves in a channel.  As the wave travels down the narrowing channel it increases in height till the water spills into an elevated reservoir.  The water trapped in the reservoir can be released back to the sea similar to conventional hydroelectric power plants to generate electricity [1].  The advantage of this particular system lies in its ability to buffer storage which dampens the irregularity of the waves.  However, the Tapchan system does require a low tidal range and suitable shoreline topography -limiting its application world-wide. A demonstration prototype of this design has been running since 1985 and plans are under consideration to build a commercial scale plant in Java [8].
    http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html
  • The Oscillating Water Column generates electricity in a two step process. As a wave enters the column, it forces the air in the column up the closed column past a turbine, and increases the pressure within the column. As the wave retreats, the air is drawn back past the turbine due to the reduced air pressure on the ocean side of turbine.
    Much research is occurring internationally to develop oscillating water columns which require less stringent siting conditions, including the OSPREY and floating columns, such as the Japanese Mighty Whale
  • Another notable example of an OWC is the “Mighty Whale.”  It is the world’s largest offshore floating OWC and was launched in July 1998 by the Japan Marine Science and Technology Center.  This prototype, moored facing the predominant wave direction, has a  displacement of 4,400 tons and measures 50m long.  The Mighty Whale has three air chambers that convert wave energy into pneumatic energy.  Wave action causes the internal water level in each chamber to rise and fall, forcing a bi-directional flow over an air-turbine to generate energy.  The resulting electricity is supplied mainly to the nearby coastal areas.  Storage batteries onboard ensure that electricity is available even during periods of reduced wave activity.  It is projected that a  row of such devices could be used to supply energy to fish farms in the calm waters behind the devices, and aeration/purification of seawater [7].
    http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html
  • This technology builds upon SARA's pioneering Ocean Wave Energy Conversion system, awarded US Patent 5,136,173; 1992. Unlike alternative concepts that make use of cumbersome intermediate mechanical stages, SARA's approach uses direct conversion of mechanical fluid energy into electricity, via a highly efficient magnetohydrodynamics (MHD) process.
    Product:
    Rapidly-deployable Wave-powered MHD Electric Generator for the US Navy
    Low-cost commercial power for coastal communities.
    Benefits:
    Almost no moving parts. No gears, no levers, no turbines, no drive belts, no bearings, etc.
    Direct, local, and efficient conversion of fluid motion into electricity, with no intermediate mechanical stages.
    Highly-compatible with very-strong, but slow-moving, driving forces (ocean waves, for example).
  • High capital costs for initial construction [9] to resist exposure to strong wave forces, storms, and corrosion [10];
    Wave energy is an intermittent resource [2];
    Requires favorable wave climate.  The highest concentration of wave energy occurs between the latitudes 40° and 60° in each hemisphere, which is where the winds blow most strongly.  Latitudes of around 30° of the equator due to the regular trade winds may also be suitable for exploitation of wave energy [11];
    Offshore wave energy systems require investment power transmission cables for electrical connections to shore [11];
    Degradation of scenic ocean front views from wave energy devices located near or on the shore, and from onshore overhead electric transmission lines [10];
    Potential interference with other uses of coastal and offshore areas such as navigation, fishing, and recreation if not properly sited [2];
    By reducing the height of waves they may affect beach processes in the littoral zone [2].
  • Ocean waves have the potential to contribute up to one TW to the global energy supply. 
    The problems associated with the intermittence of wave energy can be smoothed by integration with the general energy supply system. 
    Many different wave power plants, some of them multi-purpose, have been proposed, assessed, and cost-estimated
    With the development of large-scale demonstration and commercial power plants underway, wave energy will begin to play an increasing role in complementing other renewable and conventional energy technologies to meet global needs. 
  • Oceanic energy

    1. 1. Oceanic Energy Professor S.R. Lawrence Leeds School of Business University of Colorado Boulder, CO 80305 1
    2. 2. Course Outline  Renewable  Sustainable Hydro Power Wind Energy   Oceanic Energy   Solar Power Geothermal Biomass        Hydrogen & Fuel Cells Nuclear Fossil Fuel Innovation Exotic Technologies Integration  Distributed Generation 2
    3. 3. Oceanic Energy Outline   Overview Tidal Power     Technologies Environmental Impacts Economics Future Promise  Wave Energy      Technologies Environmental Impacts Economics Future Promise Assessment 3
    4. 4. Overview of Oceanic Energy 4
    5. 5. Sources of New Energy 5 Boyle, Renewable Energy, Oxford University Press (2004)
    6. 6. Global Primary Energy Sources 2002 6 Boyle, Renewable Energy, Oxford University Press (2004)
    7. 7. Renewable Energy Use – 2001 7 Boyle, Renewable Energy, Oxford University Press (2004)
    8. 8. Tidal Power 8
    9. 9. Tidal Motions 9 Boyle, Renewable Energy, Oxford University Press (2004)
    10. 10. Tidal Forces 10 Boyle, Renewable Energy, Oxford University Press (2004)
    11. 11. Natural Tidal Bottlenecks 11 Boyle, Renewable Energy, Oxford University Press (2004)
    12. 12. Tidal Energy Technologies 1. Tidal Turbine Farms 2. Tidal Barrages (dams) 12
    13. 13. 1. Tidal Turbine Farms 13
    14. 14. Tidal Turbines (MCT Seagen)       750 kW – 1.5 MW 15 – 20 m rotors 3 m monopile 10 – 20 RPM Deployed in multi-unit farms or arrays Like a wind farm, but    Water 800x denser than air Smaller rotors More closely spaced MCT Seagen Pile 14 http://www.marineturbines.com/technical.htm
    15. 15. Tidal Turbines (Swanturbines)  Direct drive to generator   Gravity base   Versus a bored foundation Fixed pitch turbine blades   http://www.darvill.clara.net/altenerg/tidal.htm No gearboxes Improved reliability But trades off efficiency 15
    16. 16. Deeper Water Current Turbine 16 Boyle, Renewable Energy, Oxford University Press (2004)
    17. 17. Oscillating Tidal Turbine    Oscillates up and down 150 kW prototype operational (2003) Plans for 3 – 5 MW prototypes http://www.engb.com 17 Boyle, Renewable Energy, Oxford University Press (2004)
    18. 18. Polo Tidal Turbine       Vertical turbine blades Rotates under a tethered ring 50 m in diameter 20 m deep 600 tonnes Max power 12 MW 18 Boyle, Renewable Energy, Oxford University Press (2004)
    19. 19. Power from Land Tides (!) http://www.geocities.com/newideasfromtelewise/tidalpowerplant.htm 19
    20. 20. Advantages of Tidal Turbines  Low Visual Impact   Low Noise Pollution   Sound levels transmitted are very low High Predictability   Mainly, if not totally submerged. Tides predicted years in advance, unlike wind High Power Density  Much smaller turbines than wind turbines for the same power http://ee4.swan.ac.uk/egormeja/index.htm 20
    21. 21. Disadvantages of Tidal Turbines     High maintenance costs High power distribution costs Somewhat limited upside capacity Intermittent power generation 21
    22. 22. 2. Tidal Barrage Schemes 22
    23. 23. Definitions  Barrage   Flood   An artificial dam to increase the depth of water for use in irrigation or navigation, or in this case, generating electricity. The rise of the tide toward land (rising tide) Ebb  The return of the tide to the sea (falling tide) 23
    24. 24. Potential Tidal Barrage Sites Only about 20 sites in the world have been identified as possible tidal barrage stations 24 Boyle, Renewable Energy, Oxford University Press (2004)
    25. 25. Schematic of Tidal Barrage 25 Boyle, Renewable Energy, Oxford University Press (2004)
    26. 26. Cross Section of a Tidal Barrage http://europa.eu.int/comm/energy_transport/atlas/htmlu/tidal.html 26
    27. 27. Tidal Barrage Bulb Turbine 27 Boyle, Renewable Energy, Oxford University Press (2004)
    28. 28. Tidal Barrage Rim Generator 28 Boyle, Renewable Energy, Oxford University Press (2004)
    29. 29. Tidal Barrage Tubular Turbine 29 Boyle, Renewable Energy, Oxford University Press (2004)
    30. 30. La Rance Tidal Power Barrage     Rance River estuary, Brittany (France) Largest in world Completed in 1966 24×10 MW bulb turbines (240 MW)      5.4 meter diameter Capacity factor of ~40% Maximum annual energy: 2.1 TWh Realized annual energy: 840 GWh Electric cost: 3.7¢/kWh 30 Boyle, Renewable Energy, Oxford University Press (2004) Tester et al., Sustainable Energy, MIT Press, 2005
    31. 31. La Rance Tidal Power Barrage http://www.stacey.peak-media.co.uk/Brittany2003/Rance/Rance.htm 31
    32. 32. La Rance River, Saint Malo 32
    33. 33. La Rance Barrage Schematic 33 Boyle, Renewable Energy, Oxford University Press (2004)
    34. 34. Cross Section of La Rance Barrage http://www.calpoly.edu/~cm/studpage/nsmallco/clapper.htm 34
    35. 35. La Rance Turbine Exhibit 35
    36. 36. Tidal Barrage Energy Calculations R = range (height) of tide (in m) A = area of tidal pool (in km2) m = mass of water g = 9.81 m/s2 = gravitational constant ρ = 1025 kg/m3 = density of seawater η ≅ 0.33 = capacity factor (20-35%) E = ηmgR / 2 = η ( ρAR) gR / 2 E = 1397ηR A kWh per tidal cycle 2 Assuming 706 tidal cycles per year (12 hrs 24 min per cycle) E yr = 0.997 ×10 6ηR 2 A 36 Tester et al., Sustainable Energy, MIT Press, 2005
    37. 37. La Rance Barrage Example η = 33% R = 8.5 m A = 22 km2 E yr = 0.997 ×106ηR 2 A E yr = 0.997 ×10 (0.33)(8.5 )(22) 6 2 E yr = 517 GWh/yr 37 Tester et al., Sustainable Energy, MIT Press, 2005
    38. 38. Proposed Severn Barrage (1989) Never constructed, but instructive 38 Boyle, Renewable Energy, Oxford University Press (2004)
    39. 39. Proposed Severn Barrage (1989)  Severn River estuary        Border between Wales and England 216 × 40 MW turbine generators (9.0m dia) 8,640 MW total capacity 17 TWh average energy output Ebb generation with flow pumping 16 km (9.6 mi) total barrage length £8.2 ($15) billion estimated cost (1988) 39
    40. 40. Severn Barrage Layout 40 Boyle, Renewable Energy, Oxford University Press (2004)
    41. 41. Severn Barrage Proposal Effect on Tide Levels 41 Boyle, Renewable Energy, Oxford University Press (2004)
    42. 42. Severn Barrage Proposal Power Generation over Time 42 Boyle, Renewable Energy, Oxford University Press (2004)
    43. 43. Severn Barrage Proposal Capital Costs ~$15 billion (1988 costs) 43 Tester Renewable Energy, OxfordMIT Press, Press (2004) Boyle, et al., Sustainable Energy, University 2005
    44. 44. Severn Barrage Proposal Energy Costs ~10¢/kWh (1989 costs) 44 Boyle, Renewable Energy, Oxford University Press (2004)
    45. 45. Severn Barrage Proposal Capital Costs versus Energy Costs 1p ≅ 2¢ 45 Boyle, Renewable Energy, Oxford University Press (2004)
    46. 46. Offshore Tidal Lagoon 46 Boyle, Renewable Energy, Oxford University Press (2004)
    47. 47. Tidal Fence     Array of vertical axis tidal turbines No effect on tide levels Less environmental impact than a barrage 1000 MW peak (600 MW average) fences soon 47 Boyle, Renewable Energy, Oxford University Press (2004)
    48. 48. Promising Tidal Energy Sites Country Location TWh/yr GW Canada Fundy Bay 17 4.3 Cumberland 4 1.1 Alaska 6.5 2.3 Passamaquody 2.1 1 Argentina San Jose Gulf 9.5 5 Russia Orkhotsk Sea 125 44 India Camby 15 7.6 Kutch 1.6 0.6 USA Korea 10 Australia 5.7 http://europa.eu.int/comm/energy_transport/atlas/htmlu/tidalsites.html 1.9 48
    49. 49. Tidal Barrage Environmental Factors  Changes in estuary ecosystems    Less turbidity – clearer water   More light, more life Accumulation of silt   Less variation in tidal range Fewer mud flats Concentration of pollution in silt Visual clutter 49
    50. 50. Advantages of Tidal Barrages  High predictability   Similar to low-head dams     Tides predicted years in advance, unlike wind Known technology Protection against floods Benefits for transportation (bridge) Some environmental benefits http://ee4.swan.ac.uk/egormeja/index.htm 50
    51. 51. Disadvantages of Tidal Turbines     High capital costs Few attractive tidal power sites worldwide Intermittent power generation Silt accumulation behind barrage   Accumulation of pollutants in mud Changes to estuary ecosystem 51
    52. 52. Wave Energy 52
    53. 53. Wave Structure 53 Boyle, Renewable Energy, Oxford University Press (2004)
    54. 54. Wave Frequency and Amplitude 54 Boyle, Renewable Energy, Oxford University Press (2004)
    55. 55. Wave Patterns over Time 55 Boyle, Renewable Energy, Oxford University Press (2004)
    56. 56. Wave Power Calculations Hs2 = Significant wave height – 4x rms water elevation (m) Te = avg time between upward movements across mean (s) P = Power in kW per meter of wave crest length 2 s e H T P= 2 Example: Hs2 = 3m and Te = 10s H T 3 ×10 kW P= = = 45 2 2 m 2 s e 2 56
    57. 57. Global Wave Energy Averages Average wave energy (est.) in kW/m (kW per meter of wave length) http://www.wavedragon.net/technology/wave-energy.htm 57
    58. 58. Wave Energy Potential  Potential of 1,500 – 7,500 TWh/year    200,000 MW installed wave and tidal energy power forecast by 2050     10 and 50% of the world’s yearly electricity demand IEA (International Energy Agency) Power production of 6 TWh/y Load factor of 0.35 DTI and Carbon Trust (UK) “Independent of the different estimates the potential for a pollution free energy generation is enormous.” http://www.wavedragon.net/technology/wave-energy.htm 58
    59. 59. Wave Energy Technologies 59
    60. 60. Wave Concentration Effects 60 Boyle, Renewable Energy, Oxford University Press (2004)
    61. 61. Tapered Channel (Tapchan) http://www.eia.doe.gov/kids/energyfacts/sources/renewable/ocean.html 61
    62. 62. Oscillating Water Column http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html 62
    63. 63. Oscillating Column Cross-Section 63 Boyle, Renewable Energy, Oxford University Press (2004)
    64. 64. LIMPET Oscillating Water Column      Completed 2000 Scottish Isles Two counter-rotating Wells turbines Two generators 500 kW max power 64 Boyle, Renewable Energy, Oxford University Press (2004)
    65. 65. “Mighty Whale” Design – Japan http://www.jamstec.go.jp/jamstec/MTD/Whale/ 65
    66. 66. Might Whale Design 66 Boyle, Renewable Energy, Oxford University Press (2004)
    67. 67. Turbines for Wave Energy Turbine used in Mighty Whale 67 Boyle, Renewable Energy, Oxford University Press (2004) http://www.jamstec.go.jp/jamstec/MTD/Whale/
    68. 68. Ocean Wave Conversion System http://www.sara.com/energy/WEC.html 68
    69. 69. Wave Conversion System in Action 69
    70. 70. Wave Dragon Wave Dragon Copenhagen, Denmark http://www.WaveDragon.net Click Picture for Video http://www.wavedragon.net/technology/wave-energy.htm 70
    71. 71. Wave Dragon Energy Output      in a 24kW/m wave climate = 12 GWh/year in a 36kW/m wave climate = 20 GWh/year in a 48kW/m wave climate = 35 GWh/year in a 60kW/m wave climate = 43 GWh/year in a 72kW/m wave climate = 52 GWh/year. http://www.wavedragon.net/technology/wave-energy.htm 71
    72. 72. Declining Wave Energy Costs 72 Boyle, Renewable Energy, Oxford University Press (2004)
    73. 73. Wave Energy Power Distribution 73 Boyle, Renewable Energy, Oxford University Press (2004)
    74. 74. Wave Energy Supply vs. Electric Demand 74 Boyle, Renewable Energy, Oxford University Press (2004)
    75. 75. Wave Energy Environmental Impacts 75
    76. 76. Wave Energy Environmental Impact      Little chemical pollution Little visual impact Some hazard to shipping No problem for migrating fish, marine life Extract small fraction of overall wave energy   Little impact on coastlines Release little CO2, SO2, and NOx  11g, 0.03g, and 0.05g / kWh respectively 76 Boyle, Renewable Energy, Oxford University Press (2004)
    77. 77. Wave Energy Summary 77
    78. 78. Wave Power Advantages  Onshore wave energy systems can be incorporated into harbor walls and coastal protection    Create calm sea space behind wave energy systems     Reduce/share system costs Providing dual use Development of mariculture Other commercial and recreational uses; Long-term operational life time of plant Non-polluting and inexhaustible supply of energy http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html 78
    79. 79. Wave Power Disadvantages        High capital costs for initial construction High maintenance costs Wave energy is an intermittent resource Requires favorable wave climate. Investment of power transmission cables to shore Degradation of scenic ocean front views Interference with other uses of coastal and offshore areas   navigation, fishing, and recreation if not properly sited Reduced wave heights may affect beach processes in the littoral zone http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html 79
    80. 80. Wave Energy Summary     Potential as significant power supply (1 TW) Intermittence problems mitigated by integration with general energy supply system Many different alternative designs Complimentary to other renewable and conventional energy technologies http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html 80
    81. 81. Future Promise 81
    82. 82. World Oceanic Energy Potentials (GW)        Source Tides Waves Currents OTEC1 Salinity World electric2 World hydro Temperature gradients 2 As of 1998 1      Potential (est) 2,500 GW 2,7003 5,000 200,000 1,000,000        3 4,000 Along coastlines  4 Practical (est) 20 GW 500 50 40 NPA4 2,800 550 Not presently available 82 Tester et al., Sustainable Energy, MIT Press, 2005
    83. 83. Solar Power – Next Week 83 http://www.c-a-b.org.uk/projects/tech1.jpg

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