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How does an Hydroelectric Power Plant Works ?


Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower. Hydroelectricity is an established power-generation technology with over 100 years of commercial operation.

The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The hydro station consumes no water, unlike coal or gas plants. The average cost of electricity from a hydro station larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour. With a dam and reservoir it is also a flexible source of electricity since the amount produced by the station can be changed up or down very quickly to adapt to changing energy demands. Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of greenhouse gases than fossil fuel powered energy plants.,

How Hydroelectric Power Plant Works ?
Before going to know that how an hydroelectric power  plant work we should have to know about the parts of power plant. In hydroelectric plants there are four major components :

  • Dam :-  Raises the water level of the river to create falling water. Also controls the flow of water. The reservoir that is formed is, in effect, stored energy.
  • Turbine :- The force of falling water pushing against the turbine's blades causes the turbine to spin. A water turbine is much like a windmill, except the energy is provided by falling water instead of wind. The turbine converts the kinetic energy of falling water into mechanical energy.
  • Generator :- Connected to the turbine by shafts and possibly gears so when the turbine spins it causes the generator to spin also. Converts the mechanical energy from the turbine into electric energy. Generators in hydropower plants work just like the generators in other types of power plants.
  • Transmission lines :- Conduct electricity from the hydropower plant to homes and business.


The most common type of hydroelectric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. But hydroelectric power doesn’t necessarily require a large dam. Some hydroelectric power plants just use a small canal to channel the river water through a turbine.

Another type of hydroelectric power plant- called a pumped storage plant can even store power.
The power is sent from a power grid into the electric generators. The generators then spin the turbines backward, which causes the turbines to pump water from a river or lower reservoir to an upper reservoir, where the power is stored. To use the power, the water is released from the upper reservoir back down into the river or lower reservoir. This spins the turbines forward, activating the generators to produce electricity. A small or micro-hydroelectric power system can produce enough electricity for a home, farm, or ranch.

Advantages of Hydroelectricity :-
  • The way the electricity is produced does not harm the environment as much as fossil fuels like oil or coal do.
  • Hydroelectricity is very powerful and safe, and produces no waste.
  • An important advantage of hydroelectric dams is their ability to be used as a peaking power plant. When the electricity demand declines, the dam simply stores more water.
  • Water that has been stored in a reservoir can be released (let go) when needed, so the energy can be made quickly.
  • Another advantage is that hydroelectricity cannot run out as long as there is a good water supply. Once the dam is built, the electricity costs very little, no waste or pollution is produced, and electricity can be generated whenever it is needed.
  • Impoundment hydroelectric plants, in particular, create recreation areas as a byproduct. The reservoirs created by these projects can be used by people for swimming, fishing, and boating.
Advantages of Hydroelectricity :-
  • The building of large dams to hold water can damage the environment.
  • The hydropower dams are a source of methane, which is 25 times more greenhouse potent than carbon dioxide (CO2).
  • Methane is formed in the dam when organic matter decays in the absence of oxygen. The organic matter is made up of both the plant material flooded when the dam is initially filled, and plant and soil debris washed into the dam from the banks and upstream. Phytoplankton is also a source of dam emissions in the form of organic matter.
  • Dams with large seasonal differences in height will produce methane emissions from a continual cycle of growth and decay on the banks when plants grow in summer, only to be flooded again in winter.
  • Another disadvantage of the hydropower technology is the large areas of land needed to construct large hydropower dams.
  • In 1983, the Australian government stopped the Tasmanian state government from building a dam on the Gordon River in Tasmania after a huge public protest.The dam would have flooded the Franklin River. The Three Gorges Dam in China is the world's largest hydroelectricity project. The dam has flooded a huge area, meaning that 1.2 million people had to be moved. Scientists are concerned about many problems with the dam, such as pollution, silt, and the danger of the dam wall breaking.

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