1

Tidal PowerTidal PowerLow duty cycle but feasible in Low duty cycle but feasible in

certain topologically certain topologically favorable locationsfavorable locations

2

Natural Tidal Bottlenecks - Natural Tidal Bottlenecks - WalesWales

Boyle, Renewable Energy, Oxford University Press (2004)

3

In Nova ScotiaIn Nova Scotia

4

1. Tidal Turbine 1. Tidal Turbine Farms: Challenge Farms: Challenge

its to optimize its to optimize turbine designturbine design

300 KW Turbine

5

State of the Art DesignState of the Art Design

1.5 MW

1350 Tons

6

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 barrageimpact than a barrage 1000 MW peak (600 1000 MW peak (600

MW average) fences MW average) fences soonsoon

Boyle, Renewable Energy, Oxford University Press (2004)

7

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

8

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 efficiencyBut trades off efficiency

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

9

Deeper Water Current Deeper Water Current TurbineTurbine

Boyle, Renewable Energy, Oxford University Press (2004)

10

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

11

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)

12

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 windTides predicted years in advance, unlike wind

High Power DensityHigh Power Density Much smaller turbines than wind turbines for Much smaller turbines than wind turbines for

the same powerthe same power

13

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)

14

2. Tidal Barrage 2. Tidal Barrage Schemes Schemes

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

resevoirresevoir

15

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

16

Schematic of Tidal Schematic of Tidal BarrageBarrage

Boyle, Renewable Energy, Oxford University Press (2004)

17

Cross Section of La Cross Section of La Rance BarrageRance Barrage

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

18

La Rance Tidal Power La Rance Tidal Power BarrageBarrage

Rance River estuary, Brittany Rance River estuary, Brittany (France)(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 % Electric cost: 3.7¢/kWhElectric cost: 3.7¢/kWh

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

19

La Rance Turbine ExhibitLa Rance Turbine Exhibit

20

La Rance River, Saint La Rance River, Saint MaloMalo

21

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

22

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

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

23

Proposed Severn Barrage (1989)

Boyle, Renewable Energy, Oxford University Press (2004)

Never constructed, but instructive

24

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)

25

Severn Barrage ProposalSevern Barrage ProposalCapital CostsCapital Costs

Boyle, Renewable Energy, Oxford University Press (2004)

~$15 billion(1988 costs)

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

26

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

27

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

28

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

29

PromisingPromising Tidal Energy Tidal Energy SitesSites

CountryCountry LocationLocation TWh/yrTWh/yr GWGWCanadaCanada Fundy BayFundy Bay 1717 4.34.3   CumberlandCumberland 44 1.11.1USAUSA AlaskaAlaska 6.56.5 2.32.3   PassamaquoPassamaquo

dydy2.12.1 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 0.60.6KoreaKorea    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?

30

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)