Environmental Engineering Reference
In-Depth Information
9.5 Economics
Hydroelectric power plants are considered the most cost-effective option for sup-
plying renewable electricity today. This applies mainly to older systems where the
construction costs have largely already been amortized. The relatively high con-
struction costs and long amortization periods for new sites substantially increase the
cost of generating electricity.
For small plants fewer than fi ve megawatts the investment in modernization amounts
to between 2500 and 5000 euros per kilowatt; for the reactivation of a plant or a
new plant it is between 5000 and 13000 euros per kilowatt. The costs for larger
plants are somewhat lower but depend greatly on local conditions. In addition to
the investment and operating costs, large-scale hydropower plants have to pay a fee
for water use in some countries.
With old medium-sized plants in the power range between 10 and 100 megawatts,
the cost to generate electricity is less than 2 cents per kilowatt hour. For new plants
this cost can increase up to 4 to 10 cents per kilowatt hour (Fichtner, 2003). The
costs for small plants can even be higher.
9.6 Ecology
Hydropower plants are the most controversial of all the renewable power plants.
Classic run-of-river, storage and tidal power plants in particular have a huge impact
on the natural environment.
Due to the barrage system, bodies of stationary water form in places where water
fl owing over pebbles and boulders previously provided a suitable habitat for many
different kinds of fi sh. As a result of the changes in their habitat, numerous fi sh and
plants are becoming extinct. Another danger for fi sh is the hydroelectric turbines
themselves. Although grating prevents large fi sh from entering the processing
area of a plant, the metal bars of the grating let small forms of life slip through
and become injured or killed by the turbines. The barrier systems are often an
insurmountable obstacle for fi sh swimming in the water. Fish bypasses that run
alongside the barriers help enormously in improving the freedom of movement for
fi sh (Figure 9.16). Nevertheless, barrier systems are still an obstacle for certain types
of fi sh.
Large reservoirs fl ood wide areas of land and destroy people's homes as well as
natural habitat. Sinking biomass decomposes in water and releases large quantities
of climate-damaging methane. This problem can be reduced considerably if reser-
voir basins are carefully cleared before they are fl ooded.
Breaches in walls are another danger with large dams. Normally dams are con-
structed so that they are largely earthquake-proof. But even the best construction is
powerless against targeted terrorist attacks. Huge devastation will occur if the stored
up masses of water pour into a valley all at once.
