tidal power

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Tidal PowerTidal Power

Low duty cycle but feasible in Low duty cycle but feasible in certain topologically certain topologically favorable locationsfavorable locations

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Natural Tidal Bottlenecks – Natural Tidal Bottlenecks – Its those damn crazy Welsh Its those damn crazy Welsh

again …again …

Boyle, Renewable Energy, Oxford University Press (2004)

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1. Tidal Turbine 1. Tidal Turbine Farms: Challenge Farms: Challenge its top optimize its top optimize turbine designturbine design

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Tidal FenceTidal Fence

Array of vertical axis Array of vertical axis tidal turbinestidal turbines

No effect on tide No effect on tide levelslevels

Less environmental Less environmental impact than a impact than a barragebarrage

1000 MW peak (600 1000 MW peak (600 MW average) fences MW average) fences soonsoon

Boyle, Renewable Energy, Oxford University Press (2004)

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Tidal Turbines (MCT Tidal Turbines (MCT Seagen)Seagen)

750 kW – 1.5 MW750 kW – 1.5 MW 15 – 20 m rotors15 – 20 m rotors 3 m high Pile3 m high Pile 10 – 20 RPM10 – 20 RPM Deployed in multi-unit Deployed in multi-unit

farms or arraysfarms or arrays Like a wind farm, butLike a wind farm, but

Water 800x denser Water 800x denser than airthan air

Smaller rotorsSmaller rotors More closely spacedMore closely spaced

http://www.marineturbines.com/technical.htm

MCT Seagen Pile

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Tidal Turbines Tidal Turbines (Swanturbines)(Swanturbines)

Direct drive to Direct drive to generatorgenerator No gearboxesNo gearboxes

Gravity baseGravity base Versus a bored Versus a bored

foundationfoundation Fixed pitch turbine Fixed pitch turbine

bladesblades Improved reliabilityImproved reliability But trades off But trades off

efficiencyefficiency

http://www.darvill.clara.net/altenerg/tidal.htm

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Deeper Water Current Deeper Water Current TurbineTurbine

Boyle, Renewable Energy, Oxford University Press (2004)

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Oscillating Tidal TurbineOscillating Tidal Turbine

Oscillates up and Oscillates up and downdown

150 kW prototype 150 kW prototype operational (2003)operational (2003)

Plans for 3 – 5 MW Plans for 3 – 5 MW prototypesprototypes

Boyle, Renewable Energy, Oxford University Press (2004)

http://www.engb.com

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Polo Tidal TurbinePolo Tidal Turbine Vertical turbine Vertical turbine

bladesblades Rotates under a Rotates under a

tethered ringtethered ring 50 m in diameter50 m in diameter 20 m deep20 m deep 600 tonnes600 tonnes Max power 12 MWMax power 12 MW Much better power Much better power

per ton ratio than per ton ratio than Power BuoysPower Buoys

Boyle, Renewable Energy, Oxford University Press (2004)

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Advantages of Tidal Advantages of Tidal TurbinesTurbines

Low Visual ImpactLow Visual Impact Mainly, if not totally submerged.Mainly, if not totally submerged.

Low Noise Pollution Low Noise Pollution Sound levels transmitted are very lowSound levels transmitted are very low

High PredictabilityHigh Predictability Tides predicted years in advance, unlike Tides predicted years in advance, unlike

windwind High Power DensityHigh Power Density

Much smaller turbines than wind turbines for Much smaller turbines than wind turbines for the same powerthe same power

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Disadvantages of Tidal Disadvantages of Tidal TurbinesTurbines

High maintenance costsHigh maintenance costs High power distribution costsHigh power distribution costs Somewhat limited upside capacity Somewhat limited upside capacity

less than 100 GW worldwide less than 100 GW worldwide Intermittent power generation over Intermittent power generation over

24 hour day24 hour day Fish bumping (but not chopping due Fish bumping (but not chopping due

to low RPM)to low RPM)

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2. Tidal Barrage 2. Tidal Barrage Schemes Schemes

impound tides to impound tides to create a damn create a damn

resevoirresevoir

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Potential Tidal Barrage Potential Tidal Barrage SitesSites

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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Schematic of Tidal Schematic of Tidal BarrageBarrage

Boyle, Renewable Energy, Oxford University Press (2004)

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Cross Section of La Cross Section of La Rance BarrageRance Barrage

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

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La Rance Tidal Power La Rance Tidal Power BarrageBarrage

Rance River estuary, Brittany (France)Rance River estuary, Brittany (France) Largest in world – 750 m dikeLargest in world – 750 m dike Completed in 1966Completed in 1966 2424××10 MW bulb turbines (240 MW)10 MW bulb turbines (240 MW)

5.4 meter diameter5.4 meter diameter Capacity factor of Capacity factor of ~33 %~33 % Maximum annual energy: 2.1 TWhMaximum annual energy: 2.1 TWh Realized annual energy: 840 GWhRealized annual energy: 840 GWh Electric cost: 3.7¢/kWhElectric cost: 3.7¢/kWh

Tester et al., Sustainable Energy, MIT Press, 2005Boyle, Renewable Energy, Oxford University Press (2004)

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La Rance Turbine ExhibitLa Rance Turbine Exhibit

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La Rance River, Saint La Rance River, Saint MaloMalo

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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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Proposed Severn Barrage (1989)

Boyle, Renewable Energy, Oxford University Press (2004)

Never constructed, but instructive

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Proposed Severn Barrage Proposed Severn Barrage (1989) (1989) Impressive Scale Impressive Scale

Severn River estuary (Border Severn River estuary (Border between Wales and England)between Wales and England)

216 216 × 40 MW turbine generators × 40 MW turbine generators (9.0m dia)(9.0m dia)

8,640 MW total capacity8,640 MW total capacity 16 km (9.6 mi) total barrage length16 km (9.6 mi) total barrage length £8.2 ($15) billion estimated cost £8.2 ($15) billion estimated cost

(1988)(1988)

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Severn Barrage ProposalSevern Barrage Proposal

Power Generation over Power Generation over TimeTime

Boyle, Renewable Energy, Oxford University Press (2004)

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Severn Barrage ProposalSevern Barrage Proposal

Capital CostsCapital Costs

Boyle, Renewable Energy, Oxford University Press (2004)

~$15 billion(1988 costs)

Tester et al., Sustainable Energy, MIT Press, 2005

So that’s about 30 Billion dollars today for 9 Billion Watts not terrible but not great

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Tidal Barrage Tidal Barrage Environmental FactorsEnvironmental Factors

Changes in estuary ecosystemsChanges in estuary ecosystems Less variation in tidal rangeLess variation in tidal range Fewer mud flatsFewer mud flats

Less turbidity – clearer waterLess turbidity – clearer water More light, more lifeMore light, more life

Accumulation of siltAccumulation of silt Concentration of pollution in siltConcentration of pollution in silt

Visual clutterVisual clutter

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Advantages of Tidal Advantages of Tidal BarragesBarrages

High predictabilityHigh predictability Tides predicted years in advance, unlike Tides predicted years in advance, unlike

windwind Similar to low-head damsSimilar to low-head dams

Known technologyKnown technology Protection against floodsProtection against floods Benefits for transportation (bridge)Benefits for transportation (bridge) Some environmental benefitsSome environmental benefits

http://ee4.swan.ac.uk/egormeja/index.htm

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Disadvantages of Tidal Disadvantages of Tidal BarragesBarrages

High capital costsHigh capital costs Few attractive tidal power sites Few attractive tidal power sites

worldwideworldwide Intermittent power generationIntermittent power generation Silt accumulation behind barrageSilt accumulation behind barrage

Accumulation of pollutants in mudAccumulation of pollutants in mud Changes to estuary ecosystemChanges to estuary ecosystem

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PromisingPromising Tidal Energy Tidal Energy SitesSites

CountryCountry LocationLocation TWh/yrTWh/yr GWGW

CanadaCanada Fundy BayFundy Bay 1717 4.34.3

   CumberlandCumberland 44 1.11.1

USAUSA AlaskaAlaska 6.56.5 2.32.3

   PassamaquoPassamaquodydy

2.12.1 11

ArgentinArgentinaa

San Jose San Jose GulfGulf

9.59.5 55

RussiaRussia Orkhotsk Orkhotsk SeaSea

125125 4444

IndiaIndia CambyCamby 1515 7.67.6

   KutchKutch 1.61.6 0.60.6

KoreaKorea    1010   

AustraliaAustralia    5.75.7 1.91.9

http://europa.eu.int/comm/energy_transport/atlas/htmlu/tidalsites.html

But Bottom Line Sum is only about 70 GW BFD?

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Local SitesLocal Sites

Tacoma NarrowsTacoma Narrows Deception Pass (Oceana Energy has Deception Pass (Oceana Energy has

Permit)Permit) San Francisco Bay (Golden Gate)San Francisco Bay (Golden Gate) Straits of Juan De Fuca (twice the Straits of Juan De Fuca (twice the

scale to that of Severn Barge)scale to that of Severn Barge)