Energy and the New Reality, Volume 2:

C-Free Energy Supply

Chapter 7: Ocean Energy

L. D. Danny Harveyharvey@geog.utoronto.ca

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Publisher: Earthscan, UKHomepage: www.earthscan.co.uk/?tabid=101808

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

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

Incoming wave

Motion of water column

Air co lumn

Air flow

Front wall of concrete chamber Turbine and generator

Figure 7.2b A floating wave energy conversion device

TURBINE HOUSING

TURBINE DUCTS

FLOODABLE TANKS

BUOYANCYMATER IAL

MOO NPOOL

AIRFLOW

REMO VABLE UNIT

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 oon 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

Severn Bridge

Cardiff

Weston-super-Mare10m

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

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

sea level

basinlevel

time of day

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

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

sealevel

time of day

basin level

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

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

sea level

time of day

basin level

Figure 7.6a A bulb tidal turbine

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

generator insideturbine runner

distributorsteady plinth

bulb hanger

water flow

bulb casing

Figure 7.6b A stratflo tidal turbine

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

runner

generator

Figure 7.6c A tubular tidal turbine

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

runner

gear box

generator

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

0 5 10 15 20 25 30 35

Temperature (°C)

Dep

th (

m)

Hawaii

Puerto Rico

The Gulf of Mexico

Naul

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

Evaporator

Working Fluid (Vapour)

P

P

Warm SurfaceSeawater

Turbine

Generator

Condenser

Cold DeepSeawater

Working Fluid (Liquid)

PPump

Pump

Pump

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

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

Fresh w ater

Sea water

Brackish water

Power

Brackish water

Fresh w ater bleed

PressureExchanger

M em brane M odulesTurbine

Wa

ter

Filt

er

Wa

ter

Fil

ter