For this purpose overfall of levels of a water surface is artificially created by means of dams on the rivers. By gravity water is poured from upper upstream ducts in lower on special channels where water turbines are located which blades are untwisted by a water flow. The turbine rotates a rotor generator. Special variety of hydroelectric power plants are hydroheat-sink plants. In addition to its direct purpose - electricity - hydropower decides a number of important objectives: the creation of drinking and industrial water supply, development of navigation, creation of irrigation systems for agriculture, fish-farming, the regulation of river flows, allowing for control of high waters and floods, ensuring the safety of the population.
Advantages:
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The use of renewable energy;
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Very cheap electricity;
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The work is not accompanied by harmful emissions into the atmosphere;
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Fast beginning of mode of output of working power after plant is switched on (relative to TPP ).
The first hydroelectric plant in Russia was «Bereza» plant (Ziryanovsk), built on the river Beryozovka in 1892. It had 4 turbines with total capacity of 200 kW and was intended to support with electricity of a mine water low tide from Zyryanovsky mine.
"Golden Age" of Russian hydropower was in the period from 1930 to 1990, and now in Russia there are 102 hydroelectric plants with capacity of over 100 MW.
The beginning of technical assistance to foreign countries in the construction of hydroelectric power plants were put in the middle of the last century. In the end of 1950s, there began development of the market in the Middle East: the construction of waterworks on the river Arax (Iran, 1970) , the project for the construction of "the Aswan hydropower complex" (Aswan Dam, Egypt, 1970), "Euphrates Hydro" (Syria , 1978 year). Subsequent projects: HPP "Hoa Binh" in Vietnam (1994), HPP "Capanda" in Angola (2007).
Today all over the world there is a real "boom" of the construction of new HPP, mostly in developing countries - China, India, Brazil, Pakistan, Iran, Ethiopia. For Russia the priorities are the following: the development of a hydroenergy potential of own rivers, and the design, construction and modernization of the plant abroad, such as HPP "Naglu" ( Afghanistan) - 94 MW hydroelectric power plant modernization; HPP " Polotsk " (Belarus ) - "turnkey" construction of 22 MW hydroelectric power plant; HPP " Capanda" ( Angola) - supply of spare parts.