Page 296 - Fluid Mechanics and Thermodynamics of Turbomachinery

CHAPTER 9

Hydraulic Turbines

Hear ye not the hum of mighty workings? (KEATS, Sonnet No. 14).
The power of water has changed more in this world than emperors or kings.
(Leonardo da Vinci).

Introduction
To put this chapter into perspective some idea of the scale of hydropower devel-
opment in the world might be useful before delving into the intricacies of hydraulic
turbines. A very detailed and authoritative account of virtually every aspect of
hydropower is given by Raabe (1985) and this brief introduction serves merely to
illustrate a few aspects of a very extensive subject.
Hydropower is the longest established source for the generation of electric power
which, starting in 1880 as a small dc generating plant in Wisconsin, USA, developed
into an industrial size plant following the demonstration of the economic transmis-
sion of high voltage ac at the Frankfurt Exhibition in 1891. Hydropower now has a
worldwide yearly growth rate of about five per cent (i.e. doubling in size every 15
years). In 1980 the worldwide installed generating capacity was 460 GW according
to the United Nations (1981) so, by the year 2000, at the above growth rate this
should have risen to a figure of about 1220 GW. The main areas with potential for
growth are China, Latin America and Africa.
Table 9.1 is an extract of data quoted by Raabe (1985) of the distribution of
harnessed and harnessable potential of some of the countries with the biggest usable
potential of hydro power. From this list it is seen that the People’s Republic of
China, the country with the largest harnessable potential in the world had, in 1974,
harnessed only 4.22 per cent of this. According to Cotillon (1978), with growth
rates of 14.2 per cent up to 1985 and then with a growth rate of eight per cent, the
PRC should have harnessed about 26 per cent of its harvestable potential by the
year 2000. This would need the installation of nearly 4600 MW per annum of new
hydropower plant, and a challenge to the makers of turbines around the world! One
scheme in the PRC, under construction since 1992 and scheduled for completion
in 2009, is the Xanxia (Three Gorges) project on the Yangtse which has a planned
installed capacity of 25 000 MW, and which would make it the biggest hydropower
plant in the world.
Features of hydropower plants

The initial cost of hydropower plants may be much higher than those of thermal
power plants. However, the present value of total costs (which includes those of
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