Energy and the New Reality, Volume 2: C-Free Energy Supply Chapter 7: Ocean Energy

L. D. Danny Harvey [email protected]

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Figure 7.1 Wave power density (kW per m of coastline) along the world’s coastline Source: Boud (2002, Status and Research and Development Priorities 2003, Wave and Marine Current Energy, International Energy Agency, Implementing Agreement on Ocean Energy Systems)

Figure 7.2a A shoreline wave energy conversion device

Turbine and generator Front wall of concrete chamber Air flow Air column Motion of water column Incoming wave

Source: Khan and Bhuyan (2009, Ocean Energy: Global Technology Development and Status, IEA-OES Document T0104 )

Figure 7.2b A floating wave energy conversion device

TURBINE HOUSING TURBINE DUCTS AIR FLOW FLOODABLE TANKS MOONPOOL REMOVABLE UNIT BUOYANCY MATERIAL

Source: Khan and Bhuyan (2009, Ocean Energy: Global Technology Development and Status, IEA-OES Document T0104 )

Figure 7.3 Rotation of the Earth and moon around a common centre and the resulting bulge in the ocean surface due to the resulting centrifugal force

m o o n e a rth

Source: Elliott (1996, Renewable Energy: Power for a Sustainable Future, Oxford University Press, Oxford)

Figure 7.4 The variation in tidal range within the Severn Estuary of the UK

3m m 4 m 5 m 6 7m 8m Severn Bridge m 9 Cardiff 10m 11 m Weston-super-Mare 4m 3m 2m

Source: Elliott (1996, Renewable Energy: Power for a Sustainable Future, Oxford University Press, Oxford)

Figure 7.5a Variation in water level outside and inside a tidal barrage (dam) designed to produce power only during the flood flow

sea level basin level time of day

Source: Elliott (1996, Renewable Energy: Power for a Sustainable Future, Oxford University Press, Oxford)

Figure 7.5b Variation in water level outside and inside a tidal barrage (dam) designed to produce power only during the ebb flow

basin level sea level time of day

Source: Elliott (1996, Renewable Energy: Power for a Sustainable Future, Oxford University Press, Oxford)

Figure 7.5c Variation in water level outside and inside a tidal barrage (dam) designed to produce power during both the flood and ebb flows

sea level basin level time of day

Source: Elliott (1996, Renewable Energy: Power for a Sustainable Future, Oxford University Press, Oxford)

Figure 7.6a A bulb tidal turbine

bulb hanger water flow bulb casing generator inside steady plinth distributor turbine runner

Source: Boud (2002, Status and Research and Development Priorities 2003, Wave and Marine Current Energy, International Energy Agency, Implementing Agreement on Ocean Energy Systems)

Figure 7.6b A stratflo tidal turbine

generator runner

Source: Boud (2002, Status and Research and Development Priorities 2003, Wave and Marine Current Energy, International Energy Agency, Implementing Agreement on Ocean Energy Systems)

Figure 7.6c A tubular tidal turbine

generator gear box runner

Source: Boud (2002, Status and Research and Development Priorities 2003, Wave and Marine Current Energy, International Energy Agency, Implementing Agreement on Ocean Energy Systems)

Figure 7.7 Potential sites for tidal barrages along with the tidal range (m) and potential installed power capacity (GW) Source: Elliott (1996, Renewable Energy: Power for a Sustainable Future, Oxford University Press, Oxford)

Figure 7.8 Proposed tidal current energy devices

Source: Boud (2002, Status and Research and Development Priorities 2003, Wave and Marine Current Energy, International Energy Agency, Implementing Agreement on Ocean Energy Systems)

Figure 7.9 Proposed tidal-current turbines

Source: www.e-tidevannsenergi.com

Figure 7.10 Vertical variation in temperature in the upper 1.5 km of the ocean at various tropical and subtropical locations

0 200 400 600 800 1000 1200 1400 Hawaii Puerto Rico The Gulf of Mexico Naul 0 5 10 15 20

Temperature (°C)

25 30 35

Source: www.xenesys.com

Figure 7.11 Geographical variation in the difference in temperature between the ocean surface and ‘deep’ water (typically at a depth of 1000 m) Source: www.xenesys.com

Figure 7.12 A closed-cycle OTEC process based on the Rankine cycle Warm Surface Seawater Working Fluid (Vapour) Evaporator Turbine

P

Pump Generator Condenser

P

Pump Working Fluid (Liquid)

P

Pump Cold Deep Seawater Source: Khan and Bhuyan (2009, Ocean Energy: Global Technology Development and Status, IEA-OES Document T0104 )

Figure 7.13 A pressure-retarded osmosis process for generating electricity from a salinity gradient

Brackish water

Pressure Exchanger

Sea water Power

Membrane Modules Turbine

Brackish water Fresh water bleed Fresh water

Source: Khan and Bhuyan (2009, Ocean Energy: Global Technology Development and Status, IEA-OES Document T0104 )