1 Overview of Oceanic Energy

2 Sources of New Energy Boyle, Renewable Energy, Oxford University Press (2004)

3 Global Primary Energy Sources 2002 Boyle, Renewable Energy, Oxford University Press (2004)

4 Renewable Energy Use – 2001 Boyle, Renewable Energy, Oxford University Press (2004)

5 Tidal Power

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

7 Tidal Forces Boyle, Renewable Energy, Oxford University Press (2004)

8 Natural Tidal Bottlenecks Boyle, Renewable Energy, Oxford University Press (2004)

9 Tidal Energy Technologies 1. Tidal Turbine Farms 2. Tidal Barrages (dams)

10 1. Tidal Turbine Farms

11 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 MCT Seagen Pile

12 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

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

14 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)

15 Polo Tidal Turbine Vertical turbine blades Rotates under a tethered ring 50 m in diameter 20 m deep 600 tonnes Max power 12 MW Boyle, Renewable Energy, Oxford University Press (2004)

16 Power from Land Tides (!)

17 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

18 Disadvantages of Tidal Turbines High maintenance costs High power distribution costs Somewhat limited upside capacity Intermittent power generation

19 2. Tidal Barrage Schemes

20 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)

21 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

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

23 Cross Section of a Tidal Barrage

24 Tidal Barrage Bulb Turbine Boyle, Renewable Energy, Oxford University Press (2004)

25 Tidal Barrage Rim Generator Boyle, Renewable Energy, Oxford University Press (2004)

26 Tidal Barrage Tubular Turbine Boyle, Renewable Energy, Oxford University Press (2004)

27 La Rance Tidal Power Barrage Rance River estuary, Brittany (France) Largest in world Completed in ×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)

28 La Rance Tidal Power Barrage

29 La Rance River, Saint Malo

30 La Rance Barrage Schematic Boyle, Renewable Energy, Oxford University Press (2004)

31 Cross Section of La Rance Barrage

32 La Rance Turbine Exhibit

33 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

34 La Rance Barrage Example  = 33% R = 8.5 m A = 22 km 2 GWh/yr Tester et al., Sustainable Energy, MIT Press, 2005

35 Offshore Tidal Lagoon Boyle, Renewable Energy, Oxford University Press (2004)

36 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)

37 Promising Tidal Energy Sites CountryLocationTWh/yrGW CanadaFundy Bay174.3 Cumberland41.1 USAAlaska Passamaquody2.11 ArgentinaSan Jose Gulf9.55 RussiaOrkhotsk Sea12544 IndiaCamby157.6 Kutch Korea 10 Australia

38 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

39 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

40 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

41 Wave Energy

42 Wave Structure Boyle, Renewable Energy, Oxford University Press (2004)

43 Wave Frequency and Amplitude Boyle, Renewable Energy, Oxford University Press (2004)

44 Wave Patterns over Time Boyle, Renewable Energy, Oxford University Press (2004)

45 Wave Power Calculations H s 2 = Significant wave height – 4x rms water elevation (m) T e = avg time between upward movements across mean (s) P = Power in kW per meter of wave crest length Example: H s 2 = 3m and T e = 10s

46 Global Wave Energy Averages Average wave energy (est.) in kW/m (kW per meter of wave length)

47 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.”

48 Wave Energy Technologies

49 Wave Concentration Effects Boyle, Renewable Energy, Oxford University Press (2004)

50 Tapered Channel (Tapchan)

51 Oscillating Water Column

52 Oscillating Column Cross-Section Boyle, Renewable Energy, Oxford University Press (2004)

53 LIMPET Oscillating Water Column Completed 2000 Scottish Isles Two counter-rotating Wells turbines Two generators 500 kW max power Boyle, Renewable Energy, Oxford University Press (2004)

54 “Mighty Whale” Design – Japan

55 Might Whale Design Boyle, Renewable Energy, Oxford University Press (2004)

56 Turbines for Wave Energy Boyle, Renewable Energy, Oxford University Press (2004) Turbine used in Mighty Whale

57 Ocean Wave Conversion System

58 Wave Conversion System in Action

59 Wave Dragon Wave Dragon Copenhagen, Denmark Click Picture for Video

60 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.

61 Declining Wave Energy Costs Boyle, Renewable Energy, Oxford University Press (2004)

62 Wave Energy Power Distribution Boyle, Renewable Energy, Oxford University Press (2004)

63 Wave Energy Supply vs. Electric Demand Boyle, Renewable Energy, Oxford University Press (2004)

64 Wave Energy Environmental Impacts

65 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 CO 2, SO 2, and NO x  11g, 0.03g, and 0.05g / kWh respectively Boyle, Renewable Energy, Oxford University Press (2004)

66 Wave Energy Summary

67 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

68 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

69 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

70 Future Promise

71 World Oceanic Energy Potentials (GW) Source Tides Waves Currents OTEC 1 Salinity World electric 2 World hydro Potential (est) 2,500 GW 2, , ,000 1,000,000 4,000 Practical (est) 20 GW NPA 4 2, Temperature gradients 2 As of Along coastlines 4 Not presently available Tester et al., Sustainable Energy, MIT Press, 2005