Tidal Power Low duty cycle but feasible in

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

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

In Nova Scotia 3

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

State of the Art Design 1. 5 MW 1350 Tons 5

Tidal Fence n n Boyle, Renewable Energy, Oxford University Press (2004) 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 6

Tidal Turbines (MCT Seagen) n n n 750 k. W – 1. 5 MW 15 – 20 m rotors 3 m high Pile 10 – 20 RPM Deployed in multi-unit farms or arrays Like a wind farm, but n n n Water 800 x denser than air Smaller rotors More closely spaced http: //www. marineturbines. com/technical. htm MCT Seagen Pile 7

Tidal Turbines (Swanturbines) n Direct drive to generator n n Gravity base n n Versus a bored foundation Fixed pitch turbine blades n n http: //www. darvill. clara. net/altenerg/tidal. htm No gearboxes Improved reliability But trades off efficiency 8

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

Oscillating Tidal Turbine n n n Oscillates up and down 150 k. W prototype operational (2003) Plans for 3 – 5 MW prototypes http: //www. engb. com Boyle, Renewable Energy, Oxford University Press (2004) 10

Polo Tidal Turbine n n n n Boyle, Renewable Energy, Oxford University Press (2004) 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 11

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

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

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

Potential Tidal Barrage Sites Only about 20 sites in the world have been identified as possible tidal barrage stations Boyle, Renewable Energy, Oxford University Press (2004) 15

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

Cross Section of La Rance Barrage http: //www. calpoly. edu/~cm/studpage/nsmallco/clapper. htm 17

La Rance Tidal Power Barrage Rance River estuary, Brittany (France) n Largest in world – 750 m dike n Completed in 1966 n 24× 10 MW bulb turbines (240 MW) n n 5. 4 meter diameter Capacity factor of ~33 % n Electric cost: 3. 7¢/k. Wh n Boyle, Renewable Energy, Oxford University Press (2004) 18 Tester et al. , Sustainable Energy, MIT Press, 2005

La Rance Turbine Exhibit 19

La Rance River, Saint Malo 20

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 r = 1025 kg/m 3 = density of seawater h 0. 33 = capacity factor (20 -35%) k. Wh per tidal cycle Assuming 706 tidal cycles per year (12 hrs 24 min per cycle) 21 Tester et al. , Sustainable Energy, MIT Press, 2005

La Rance Barrage Example h = 33% R = 8. 5 m A = 22 km 2 GWh/yr 22 Tester et al. , Sustainable Energy, MIT Press, 2005

Proposed Severn Barrage (1989) Never constructed, but instructive 23 Boyle, Renewable Energy, Oxford University Press (2004)

Proposed Severn Barrage (1989) Impressive Scale Severn River estuary (Border between Wales and England) n 216 × 40 MW turbine generators (9. 0 m dia) n 8, 640 MW total capacity n 16 km (9. 6 mi) total barrage length n £ 8. 2 ($15) billion estimated cost (1988) n 24

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

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

Advantages of Tidal Barrages n High predictability n n Tides predicted years in advance, unlike wind Similar to low-head dams n Known technology Protection against floods n Benefits for transportation (bridge) n Some environmental benefits n http: //ee 4. swan. ac. uk/egormeja/index. htm 27

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

But Bottom Line Sum is only about 70 GW BFD? Promising Tidal Energy Sites Country Canada Location Fundy Bay TWh/yr 17 GW 4. 3 USA Cumberland Alaska 4 6. 5 1. 1 2. 3 Argentina Passamaquody San Jose Gulf 2. 1 9. 5 1 5 Russia India Orkhotsk Sea Camby 125 15 44 7. 6 Korea Kutch 1. 6 10 0. 6 Australia 5. 7 1. 9 http: //europa. eu. int/comm/energy_transport/atlas/htmlu/tidalsites. html 29

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