530 HYDROELECTRIC POWER DEVELOPMENT
energy of the water and are built of steel; their efficiencies are about 85%
(overshot) and 75% (undershot) for a wide range of flow conditions 0.2
Q/Qmax1. For further details of water wheels see Viollet (2005) and
Müller and Kauppert (2004).
The main advantage of small hydropower schemes which are – like all
hydropower – a valuable renewable energy source are their flexibility of
siting, relatively short periods of design and construction, modest capital
costs, possible multiple development, automation of control, conjunctive
use with other energy sources and flexibility in meeting demand. However,
they are not suitable for meeting major concentrated demands and require
careful considerations of suitable plant siting, capacity and type.
For further discussion of small hydroelectric plants see e.g. Monition,
Le Nir and Roux (1984) and Gosschalk (2002).
12.12 Other energy resources
Hydropower is of course only one of many resources for generating elec-
tricity. Electricity from coal, oil, gas and nuclear fission power stations and
other renewable resources like wind power, tidal and wave energy, geo-
thermal, solar and depression energy, combustion of biomass as well as the
nuclear fusion power (currently at the feasibility stage) all provide the
components for an energy policy which is constantly evolving particularly
at the time when the need for the reduction of carbon emissions is para-
mount. Even a superficial discussion of energy policies as well as of the
above mentioned alternatives is beyond the scope of this text and only a
brief mention of marine based power development is included.
In principle three forms of marine energy can be considered for
power generation (for a more detailed discussion see Kerr 2005):
- tidal barrage power using head difference;
- tidal stream power using kinetic energy;
- wave power using the energy of wave motion.
In all cases economic, technical and environmental issues have to be con-
sidered.
(a) Tidal power
The use of tidal energy dates back to the 12th century, when tidal mills
worked along the coast of Brittany, France. The basic principle of their
operation was to form a storage basin by constructing a dyke closing off a
cove; the basin filled through gates during the flood tide, and during the
ebb tide it emptied through an undershot wheel, thus producing a driving
