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How a Hydroelectric Dam Works

written by: Suvo • edited by: Lamar Stonecypher • updated: 7/26/2013

The power of falling water is unlocked by a hydroelectric dam in the form of electricity. In this article, we will look at how hydroelectric dams work, and what are their advantages and disadvantages.

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    Hydroelectric power produced by hydroelectric dams accounts for 20% of the world’s total production of electrical energy. Although human beings have been using the power of water for around 2000 years now, the idea of generating electricity from it only started in the mid-20th century.

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    How it Works

    Hydroelectric Dam 

    A hydroelectric dam converts potential energy (and/or kinetic energy) to electrical energy by means of a turbine and alternator.

    A typical hydroelectric dam has the following main parts:

    • Water Reservoir: A large quantity of water is stored in a reservoir (or dam). The height or depth of the stored water determines how much electricity can be generated. As the depth increases, the generation of electricity also increases.
    • Gate: A control gate is used for releasing/blocking water from the dam. Depending upon the electricity requirements, the gate is opened.
    • Penstock: The released water from the dam reaches the turbine blade through the penstock. The proper slope and diameter of the penstock is important for the efficiency of the dam.
    • Turbine: The turbine consists of a number of large fan blades and a spindle. The spindle rotates when water strikes the blades. Thus the power of flowing water is converted to the rotational power of the spindle.
    • Alternator: The spindle of the turbine is connected to the alternator, where rotational power of the spindle is converted into electrical power. The produced electricity is then distributed to the grid.
    • River: The outflow of water from the turbine is released to a river.
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    Advantages of Hydroelectric Dams

    • Cheap Electricity: The operating cost of a hydroelectric dam is minimal as there is no costly fossil fuel required. Hydroelectric dams also tend to last longer than thermal power plants.
    • Less Emissions: Hydroelectric power plants produces less green house gas emissions when compared to a thermal power plant.
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    Disadvantages of Hydroelectric Dams

    • Effect on Eco-Systems: The construction of a dam affects the eco-system of the river and surrounding area. Some species of fish cannot increase their population because of dams.
    • Relocation: Dams are often constructed in populated locations causing both humans and animals to relocate.
    • Green House Gas Emissions: Althoug hydroelectric dams have considerabley fewer emissions than thermal power plants, the blocked water in the dam does cause the release of methane into the atmosphere.
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    There are many advantages to using hydroelectric power, but no form of producing energy is without its downfalls. We hope continued research and development will minimize the disadvantages.