Energy and the New Reality, Volume 2:
C-Free Energy Supply
Chapter 7: Ocean Energy
L. D. Danny Harvey
harvey@geog.utoronto.ca
Publisher: Earthscan, UK
Homepage: www.earthscan.co.uk/?tabid=101808
This material is intended for use in lectures, presentations and as
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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
Front wall of concrete chamber
Turbine and generator
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
REMOVABLE UNIT
TURBINE DUCTS
AIR
FLOW
FLOODABLE TANKS
MOONPOOL
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 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
3m
Severn Bridge
10m
11m
9m
8m
Cardiff
7m
6m
5m
4m
Weston-super-Mare
2m
3m
4m
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
turbine runner
generator inside
bulb casing
distributor
steady plinth
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
Depth (m)
400
600
Hawaii
800
Puerto Rico
The Gulf of Mexico
1000
Naul
1200
1400
0
5
10
15
20
Temperature (°C)
Source: www.xenesys.com
25
30
35
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
Generator
P
Condenser
Pump
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
Water
Filter
Power
Membrane Modules
Turbine
Fresh water
Water
Filter
Brackish water
Fresh water bleed
Source: Khan and Bhuyan (2009, Ocean Energy: Global Technology Development and Status,
IEA-OES Document T0104 )