Environmental Engineering Reference
In-Depth Information
Early hydroelectric plants were built in mountainous regions to take advantage of
fast-flowing streams and waterfalls. Later, dams were built to create a reservoir of potential
energy that could be tapped on demand. Such projects not only allowed for electricity
generation on a grand scale but also involved enormous investment and environmental
disruption. Many countries, particularly those with few native fossil fuel reserves, came
to rely heavily on hydropower to satisfy their electricity needs, and, in many cases,
plants have iconic status in many developing countries, representing both the blessings and
the blight of industrial development.
Power Generation in All Shapes and Sizes
The technology of hydropower is relatively simple. The kinetic energy of flowing water
drives a turbine, thereby generating electricity. Like wind power, hydropower is an indirect
form of solar energy. Without the constant replenishment of the river source through
evaporation and rainfall, the river and the reservoir would quickly dry up.
There are two main types of hydropower plant: dams and run-of-the-river schemes.
Dammed hydropower relies on a reservoir that builds up behind the dam, while
run-of-the-river schemes, which are small-scale by nature, take advantage of the natural
flow of the river and a very small reservoir, known as pondage (see
Figure 4.4
)
. The
capacity of a dammed hydropower plant depends mostly on the volume of water in the
reservoir and on the size of the dam. Unlike other renewable energy sources, hydropower
lends itself to megaprojects. The world's four largest power plants are all hydropower
facilities, with capacities from 22 to 8 gigawatts. However, such mammoth hydroelectric
projects are limited by the number of suitable rivers, not to mention by the social and
