technological developments since the completion of the La Rance power
scheme have stimulated the construction of smaller tidal plants in
Canada, China and Russia and the planning of major schemes in
Argentina, Australia, Canada, China, India, Korea, Russia and the UK
with a total capacity of 43 GW and annual power of 63 TWh. For further
details of tidal power generation see e.g. Wilson and Balls (1987) and
Haws (1997).
(b) Tidal stream power
Marine currents caused by tides or/and oceanic circulation have a large
potential energy even if most are too slow for exploitation. Some develop-
ment projects are under way.
(c) Wave power
Using the sinusoidal wave equations and the expressions for its energy
(see Sections 14.2.3 and 14.2.4) and applying some approximations
Mosonyi (1988) derived a very simple equation for the specific wave
power:
PH^2 T(kW/m) (12.36)
(His the wave height (m) and Tthe wave period(s)). Mosonyi assumes
that about 50% of this energy can be captured and utilized with a further
50% efficiency (generation and transmission).
Worldwide the wave energy is a very large renewable resource even
if only a small part is realistically recoverable. The UK has the largest
potential of European countries with locations in Australia and South and
North America having substantial resources.
Wave energy devices are either shoreline, near-shore (mounted on
the sea bed) or offshore (floating) and convert energy by using an oscillat-
ing water column, hinged contour devices (power is extracted from the
motion of the joints) or the motion of the device relative to the sea bed.
The on-shore and near-shore plants have the additional advantage of the
technology being integrated into harbour walls and coastal protection
structures.
A cylindrical device seated on the sea bed with its upper part oscil-
lating vertically as water pressure changes with passing waves was as a pro-
totype installed in 2004 off the coast of Portugal; the first commercial wave
energy installation (hinged contour device) is likely also to be in Portugal
(Kerr, 2005). Devices using an oscillatory water column as shoreline devel-
opment were tested in UK.
For further details of wave power development and devices see
Taylor (1983) or Thorpe (1999).
532 HYDROELECTRIC POWER DEVELOPMENT
