1 Overview of Oceanic Energy. 2 Sources of New Energy Boyle, Renewable Energy, Oxford University...
Transcript of 1 Overview of Oceanic Energy. 2 Sources of New Energy Boyle, Renewable Energy, Oxford University...
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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
http://www.marineturbines.com/technical.htm
MCT Seagen Pile
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Tidal Turbines (Swanturbines)
Direct drive to generator No gearboxes
Gravity base Versus a bored foundation
Fixed pitch turbine blades Improved reliability But trades off efficiency
http://www.darvill.clara.net/altenerg/tidal.htm
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Oscillating Tidal Turbine
Oscillates up and down 150 kW prototype
operational (2003) Plans for 3 – 5 MW
prototypes
Boyle, Renewable Energy, Oxford University Press (2004)
http://www.engb.com
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Polo Tidal Turbine
Vertical turbine blades Rotates under a
tethered ring 50 m in diameter 20 m deep 600 tonnes Max power 12 MW
Boyle, Renewable Energy, Oxford University Press (2004)
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Advantages of Tidal Turbines
Low Visual Impact Mainly, if not totally submerged.
Low Noise Pollution Sound levels transmitted are very low
High Predictability 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
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Disadvantages of Tidal Turbines High maintenance costs High power distribution costs Somewhat limited upside capacity Intermittent power generation
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Definitions
Barrage An artificial dam to increase the depth of water for
use in irrigation or navigation, or in this case, generating electricity.
Flood The rise of the tide toward land (rising tide)
Ebb The return of the tide to the sea (falling tide)
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Potential Tidal Barrage Sites
Boyle, Renewable Energy, Oxford University Press (2004)
Only about 20 sites in the world have been identified as possible tidal barrage stations
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Cross Section of a Tidal Barrage
http://europa.eu.int/comm/energy_transport/atlas/htmlu/tidal.html
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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
Tester et al., Sustainable Energy, MIT Press, 2005Boyle, Renewable Energy, Oxford University Press (2004)
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Tidal Barrage Energy Calculations
ARE
gRARmgRE21397
2/)(2/
R = range (height) of tide (in m)A = area of tidal pool (in km2)m = mass of waterg = 9.81 m/s2 = gravitational constant = 1025 kg/m3 = density of seawater 0.33 = capacity factor (20-35%)
kWh per tidal cycle
Assuming 706 tidal cycles per year (12 hrs 24 min per cycle)
AREyr2610997.0
Tester et al., Sustainable Energy, MIT Press, 2005
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La Rance Barrage Example
= 33%R = 8.5 mA = 22 km2
517
)22)(5.8)(33.0(10997.0
10997.026
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yr
yr
yr
E
E
ARE
GWh/yr
Tester et al., Sustainable Energy, MIT Press, 2005
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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
Boyle, Renewable Energy, Oxford University Press (2004)
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Promising Tidal Energy Sites
Country Location TWh/yr GW
Canada Fundy Bay 17 4.3
Cumberland 4 1.1
USA 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
Korea 10
Australia 5.7 1.9
http://europa.eu.int/comm/energy_transport/atlas/htmlu/tidalsites.html
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Tidal Barrage Environmental Factors Changes in estuary ecosystems
Less variation in tidal range Fewer mud flats
Less turbidity – clearer water More light, more life
Accumulation of silt Concentration of pollution in silt
Visual clutter
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Advantages of Tidal Barrages
High predictability Tides predicted years in advance, unlike wind
Similar to low-head dams Known technology
Protection against floods Benefits for transportation (bridge) Some environmental benefits
http://ee4.swan.ac.uk/egormeja/index.htm
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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
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Wave Power Calculations
2
2es TH
P
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
Example: Hs2 = 3m and Te = 10s
m
kWTHP es 45
2
103
2
22
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Global Wave Energy Averages
http://www.wavedragon.net/technology/wave-energy.htm
Average wave energy (est.) in kW/m (kW per meter of wave length)
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Wave Energy Potential
Potential of 1,500 – 7,500 TWh/year 10 and 50% of the world’s yearly electricity demand IEA (International Energy Agency)
200,000 MW installed wave and tidal energy power forecast by 2050 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
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Oscillating Water Column
http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html
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LIMPET Oscillating Water Column
Completed 2000 Scottish Isles Two counter-rotating
Wells turbines Two generators 500 kW max power
Boyle, Renewable Energy, Oxford University Press (2004)
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Turbines for Wave Energy
Boyle, Renewable Energy, Oxford University Press (2004) http://www.jamstec.go.jp/jamstec/MTD/Whale/
Turbine used in Mighty Whale
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Wave Dragon
http://www.wavedragon.net/technology/wave-energy.htm
Wave DragonCopenhagen, Denmarkhttp://www.WaveDragon.net
Click Picture for Video
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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
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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
Boyle, Renewable Energy, Oxford University Press (2004)
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Wave Power Advantages
Onshore wave energy systems can be incorporated into harbor walls and coastal protection Reduce/share system costs Providing dual use
Create calm sea space behind wave energy systems 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
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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
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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
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World Oceanic Energy Potentials (GW)
Source Tides Waves Currents OTEC1
Salinity World electric2
World hydro
Potential (est) 2,500 GW 2,7003
5,000 200,000 1,000,000
4,000
Practical (est) 20 GW 500 50 40 NPA4
2,800 550
1 Temperature gradients2 As of 1998
3 Along coastlines 4 Not presently available
Tester et al., Sustainable Energy, MIT Press, 2005