(About 250 surfers visit expert-eyes.org a month to find out what hydroelectricity is though this site mainly deals with human environmental impact of hydroelectric projects.
This write up by Deepak M. Roy (student of Electrical and Electronics
Engineering, College of Engineering, Trivandrum) is for those who seek
information on the basics of hydroelectricity.)
Hydroelectricity or hydroelectric power is the electricity obtained by harnessing the power
of water flowing down from a high level. It is a timeless and renewable
Huge generators convert the potential energy of falling
or fast moving water into electrical energy. The potential energy
of the water is first converted into mechanical energy and then into
Water, usually stored in dams, is led down through
large pipes or tunnels to lower levels, and in the course of the fall,
the water rotates turbines. The mechanical energy produced is
converted to electricity by the generators connected to it.
The structure that
houses the turbines and generators is called the powerhouse.
Transformers change the alternating current produced by the generators into current of very high
voltage for easy transmission through long distances.
Hydropower is one of
the three principal sources of energy used to generate electricity,
the other two being fossil fuels and nuclear fuels. Hydroelectricity
has certain advantages over these other sources: it is continually
renewable thanks to the recurring nature of the water cycle, and causes no pollution. Also, it is one of
the cheapest sources of electrical energy.
The Itaipú Dam
between Brazil and Paraguay, which is 190 metres high and
generates more than 12,600 MW, is the largest hydropower dam in the world. (The
185-metre Three Gorges Dam, now being constructed in China on the upper
Yangtze River, would take its place by 2009, producing 18,200 MW of power ). The
Grand Coulee Dam, located near Spokane, Washington, is the largest
hydropower dam in the United States, producing 6,480 MW. The Rogun
Dam, in Russia, the tallest in the world, is 335 metres high.
The Oroville dam, located in California, the tallest in the
United States, is 235 metres high. Idukki dam in India is Asia's
first and largest archdam.