1 overview of oceanic energy. 2 sources of new energy boyle, renewable energy, oxford university...

1

Overview of Oceanic Energy

2

Sources of New Energy

Boyle, Renewable Energy, Oxford University Press (2004)

3

Global Primary Energy Sources 2002


4

Renewable Energy Use – 2001


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Tidal Power

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Tidal Motions


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Tidal Forces


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Natural Tidal Bottlenecks


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Tidal Energy Technologies

1. Tidal Turbine Farms

2. Tidal Barrages (dams)

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1. Tidal Turbine Farms

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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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Deeper Water Current Turbine


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Oscillating Tidal Turbine

Oscillates up and down 150 kW prototype

operational (2003) Plans for 3 – 5 MW

prototypes


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


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Power from Land Tides (!)

http://www.geocities.com/newideasfromtelewise/tidalpowerplant.htm

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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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2. Tidal Barrage Schemes

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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


Only about 20 sites in the world have been identified as possible tidal barrage stations

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Schematic of Tidal Barrage


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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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Tidal Barrage Bulb Turbine


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Tidal Barrage Rim Generator


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Tidal Barrage Tubular Turbine


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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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La Rance Tidal Power Barrage

http://www.stacey.peak-media.co.uk/Brittany2003/Rance/Rance.htm

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La Rance River, Saint Malo

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La Rance Barrage Schematic


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Cross Section of La Rance Barrage

http://www.calpoly.edu/~cm/studpage/nsmallco/clapper.htm

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La Rance Turbine Exhibit

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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

26

yr

yr

yr

E

E

ARE

GWh/yr


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Offshore Tidal Lagoon


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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


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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 Energy

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Wave Structure


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Wave Frequency and Amplitude


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Wave Patterns over Time


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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.”


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Wave Energy Technologies

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Wave Concentration Effects


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Tapered Channel (Tapchan)

http://www.eia.doe.gov/kids/energyfacts/sources/renewable/ocean.html

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Oscillating Water Column

http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html

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Oscillating Column Cross-Section


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LIMPET Oscillating Water Column

Completed 2000 Scottish Isles Two counter-rotating

Wells turbines Two generators 500 kW max power


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“Mighty Whale” Design – Japan

http://www.jamstec.go.jp/jamstec/MTD/Whale/

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Might Whale Design


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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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Ocean Wave Conversion System

http://www.sara.com/energy/WEC.html

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Wave Conversion System in Action

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Wave Dragon


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.


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Declining Wave Energy Costs


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Wave Energy Power Distribution


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Wave Energy Supply vs. Electric Demand


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Wave Energy Environmental Impacts

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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


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Wave Energy Summary

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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


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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


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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


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Future Promise

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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


1 overview of oceanic energy. 2 sources of new energy boyle, renewable energy, oxford university...

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