force. The operational principle of a tidal power plant remains the same as
that of the tidal mills, but the turbine units may produce power during
filling as well as emptying of the basin (Fig. 12.22(a)).
Tidal amplitudes attain considerable magnitudes along certain
coastal stretches (Canadian Atlantic coast 13.5 m, Bristol Channel, UK,
10 m, French Atlantic coast 8 m; figures relate to mean annual ranges). In
the Pacific region, e.g. the coasts of China and Russia, mean amplitudes of
6–9 m have also been recorded.
In spite of the fact that tidal power production costs are slightly
higher (around 3p per kW h compared with 2–2.5p. for nuclear power, at
1980 prices) and that it fluctuates both daily and seasonally, it could dis-
place oil- or coal-fired stations for peak generation and also provide power
for pumped storage schemes.
The first tidal power station at La Rance on the west coast of France
has an installed capacity of 240 MW (24 bulb-type units of 10 MW each)
with a load factor of 25%, the peaks in the generation of power being
directed to displace the peak generation of oil-fired plants and to supply
the pumped storage schemes in the Pyrenees. The bulb turbines also
permit pumping, thus superelevating the basin level (Fig. 12.22(b)) with
respect to the sea level at the end of filling. This installation has now been
accepted as successful since its energy production costs are competitive
with those of other resources in the French power system. Furthermore,
OTHER ENERGY RESOURCE 531
Fig. 12.22 Tidal power development