Hydro-power 291Table 11.5Contributions to world energy supply (in millions of tonnes
of oil equivalent) from renewable sources in 1990 and as assumed
under the WEC scenario C in 20201990 2020
% of world % of world
Mtoe energy Mtoe energy‘Modern’ biomass 121 1.4 561 5.0
Solar 12 0.1 355 3.1
Wind 1 0.0 215 1.9
Geothermal 12 0.1 91 0.8
‘Small’ hydro 18 0.2 69 0.6
Tides, waves and 0 0.0 54 0.5
tidal streams
Total (new 164 1.8 1345 11.9
renewable sources)
‘Large’ hydro 465 5.3 661 5.8
‘Traditional’ biomass 930 10.6 1060 9.3
Total (all renewables) 1559 17.7 3066 27.0
FromEnergy for Tomorrow’s World: the Realities, the Real Options and The
Agenda for Achievement. WEC Commission Report. 1993. London: World En-
ergy Council,p. 94.Hydro-power
Hydro-power, the oldest form of renewable energy, is well established and
is competitive economically with electricity generated by other means.
Some hydroelectric schemes are extremely large. The world’s largest, the
Three Gorges project on the Yangtze river in China, when completed will
generate about 20 000 MW of electricity. Two other large schemes, each
of over 10 000 MW capacity, are in South America at Guri in Venezuela
and at Itaipu on the borders of Brazil and Paraguay. It is estimated^28
that there is potential for further exploitation of hydroelectric capacity
to three or four times the amount that has currently been developed,
much of this undeveloped potential being in the former Soviet Union and
in developing countries. Large schemes, however, can have significant
social impact (such as the movement of population from the reservoir
site), environmental consequences (for example, loss of land, of species
and of sedimentation to the lower reaches of the river), and problems
of their own such as silting up, which have to be thoroughly addressed
before they can be undertaken.