1 Tidal Power Low duty cycle but feasible in certain topologically favorable locations

2 Natural Tidal Bottlenecks - Wales Boyle, Renewable Energy, Oxford University Press (2004)

3 In Nova Scotia

4 1. Tidal Turbine Farms: Challenge its to optimize turbine design 300 KW Turbine

5 State of the Art Design 1.5 MW 1350 Tons

6 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)

7 Tidal Turbines (MCT Seagen) 750 kW – 1.5 MW 750 kW – 1.5 MW 15 – 20 m rotors 15 – 20 m rotors 3 m high Pile 3 m high Pile 10 – 20 RPM 10 – 20 RPM Deployed in multi-unit farms or arrays Deployed in multi-unit farms or arrays Like a wind farm, but Like a wind farm, but Water 800x denser than air Water 800x denser than air Smaller rotors Smaller rotors More closely spaced More closely spaced MCT Seagen Pile

8 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

9 Deeper Water Current Turbine Boyle, Renewable Energy, Oxford University Press (2004)

10 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)

11 Polo Tidal Turbine Vertical turbine blades Rotates under a tethered ring 50 m in diameter 20 m deep 600 tonnes Max power 12 MW Much better power per ton ratio than Power Buoys Boyle, Renewable Energy, Oxford University Press (2004)

12 Advantages of Tidal Turbines Low Visual Impact Low Visual Impact Mainly, if not totally submerged. Mainly, if not totally submerged. Low Noise Pollution Low Noise Pollution Sound levels transmitted are very low Sound levels transmitted are very low High Predictability High Predictability Tides predicted years in advance, unlike wind Tides predicted years in advance, unlike wind High Power Density High Power Density Much smaller turbines than wind turbines for the same power Much smaller turbines than wind turbines for the same power

13 Disadvantages of Tidal Turbines High maintenance costs High maintenance costs High power distribution costs High power distribution costs Somewhat limited upside capacity  less than 100 GW worldwide Somewhat limited upside capacity  less than 100 GW worldwide Intermittent power generation over 24 hour day Intermittent power generation over 24 hour day Fish bumping (but not chopping due to low RPM) Fish bumping (but not chopping due to low RPM)

14 2. Tidal Barrage Schemes  impound tides to create a damn resevoir

15 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

16 Schematic of Tidal Barrage Boyle, Renewable Energy, Oxford University Press (2004)

17 Cross Section of La Rance Barrage

18 La Rance Tidal Power Barrage Rance River estuary, Brittany (France) Rance River estuary, Brittany (France) Largest in world – 750 m dike Largest in world – 750 m dike Completed in 1966 Completed in ×10 MW bulb turbines (240 MW) 24×10 MW bulb turbines (240 MW) 5.4 meter diameter 5.4 meter diameter Capacity factor of ~33 % Capacity factor of ~33 % Electric cost: 3.7¢/kWh Electric cost: 3.7¢/kWh Tester et al., Sustainable Energy, MIT Press, 2005Boyle, Renewable Energy, Oxford University Press (2004)

19 La Rance Turbine Exhibit

20 La Rance River, Saint Malo

21 Tidal Barrage Energy Calculations R = range (height) of tide (in m) A = area of tidal pool (in km 2 ) m = mass of water g = 9.81 m/s 2 = gravitational constant  = 1025 kg/m 3 = 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) Tester et al., Sustainable Energy, MIT Press, 2005

22 La Rance Barrage Example  = 33% R = 8.5 m A = 22 km 2 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 (1989)  Impressive Scale Severn River estuary (Border between Wales and England) Severn River estuary (Border between Wales and England) 216 × 40 MW turbine generators (9.0m dia) 216 × 40 MW turbine generators (9.0m dia) 8,640 MW total capacity 8,640 MW total capacity 16 km (9.6 mi) total barrage length 16 km (9.6 mi) total barrage length £8.2 ($15) billion estimated cost (1988) £8.2 ($15) billion estimated cost (1988)

25 Severn Barrage Proposal Capital Costs Boyle, Renewable Energy, Oxford University Press (2004) ~$15 billion (1988 costs) Tester et al., Sustainable Energy, MIT Press, 2005

26 Tidal Barrage Environmental Factors Changes in estuary ecosystems Changes in estuary ecosystems Less variation in tidal range Less variation in tidal range Fewer mud flats Fewer mud flats Less turbidity – clearer water Less turbidity – clearer water More light, more life More light, more life Accumulation of silt Accumulation of silt Concentration of pollution in silt Concentration of pollution in silt Visual clutter Visual clutter

27 Advantages of Tidal Barrages High predictability High predictability Tides predicted years in advance, unlike wind Tides predicted years in advance, unlike wind Similar to low-head dams Similar to low-head dams Known technology Known technology Protection against floods Protection against floods Benefits for transportation (bridge) Benefits for transportation (bridge) Some environmental benefits Some environmental benefits

28 Disadvantages of Tidal Barrages High capital costs High capital costs Few attractive tidal power sites worldwide Few attractive tidal power sites worldwide Intermittent power generation Intermittent power generation Silt accumulation behind barrage Silt accumulation behind barrage Accumulation of pollutants in mud Accumulation of pollutants in mud Changes to estuary ecosystem Changes to estuary ecosystem

29 PromisingPromising Tidal Energy Sites PromisingCountryLocationTWh/yrGWCanada Fundy Bay Cumberland41.1 USAAlaska Passamaquody2.11 Argentina San Jose Gulf 9.55 Russia Orkhotsk Sea IndiaCamby157.6 Kutch Korea 10 Australia But Bottom Line Sum is only about 70 GW  BFD?

30 Local Sites Tacoma Narrows Tacoma Narrows Deception Pass (Oceana Energy has Permit) Deception Pass (Oceana Energy has Permit) San Francisco Bay (Golden Gate) San Francisco Bay (Golden Gate) Straits of Juan De Fuca (twice the scale to that of Severn Barge) Straits of Juan De Fuca (twice the scale to that of Severn Barge)