Hydropower Plants | Pumped Storage Scheme Working Principle


Hydro energy is the energy generated by the force of water. This is the powerful way of generating electricity. The hydro energy is converted into electrical energy by hydroelectric power plant and this energy is called hydroelectricity.

History of hydroelectric power plants

The words first hydroelectric power plant builds across the Fox River in Appleton wiscon in US in the year 1882. India’s first hydroelectric power plant was commissioned in 1887 at Sidrapong Darjeeling in west Bengal.

India’s largest hydro power plant is located at river koyna in Maharashtra. It has capacity of producing 1920 megawatt electricity. Bhakranangal is the biggest dam in India as well as the world’s highest straight gravity dam.

Working principle of hydroelectric power plant

In this power plant production of electricity depends upon the highest water from ground level volume of water flowing per unit time efficiency of turbines.


Hydroelectric power plant requires water reservoir these plants are constructed near big dams. Water stored in dams has potential energy. Water under pressure carried by pen-stock and supplied to the turbine through the inlet value pen stock is the pipe made up of steel or concrete.

A surge tank reduces the excessive water force on the pen stock.

The trash rack prevents the debris from getting entry into the power house.

Due to force of water the turbine starts rotating due to which mechanical energy is produced.

The shaft from the turbine is connected to the generator. Therefore generator produces electricity is raised by using the transformer and is transferred by the distribution lines.

After running the turbine water is passed through the downstream water level by draft tube.

The demand of electricity varies by day and night as well as among the season. Hence there is a need two store the energy so that it can be used at the time of high electricity.

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Advantage of hydroelectric power plant

  • The most important advantage is that it keeps the environment clean.
  • Hydro energy can be stored in high level reservoirs and used whenever is necessary.
  • Electricity is produced at a constant rate
  • The life of dams and power plants last for many decades
  • The water can be used for supplying, drinking water, irrigation water sports, industries, power plants. When electricity is not needed the sluice gate is closed to stop the generation of electricity it also allows the storage of water.


  • However the disadvantage is that constructing hydroelectric power plants and dam is very expensive.
  • It requires very large area
  • Planning a hydroelectric plant and reservoir may lead to the disruption of the lives of people as they have to relocate to another area.

Pumped storage scheme

When there are large amount of electricity needed by the consumers that time is called as peaks normally in the morning and evenings.

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During these peaks the quick reacting stations are needed pump storage schemes are this category.

The pumped storage scheme consists of a lower and upper dam between these two dams station is located. This also doubles the pumping during the emergency and peak demand. The water stored in upper dam is released large water ways flows through the turbines to generate electricity. During peak periods the electricity demand is reduced reversible pump turbines use electricity from grid to pump the water backup to the upper dam.

It necessary to pump stations back after use pump base power stations only provided electricity only limited periods of time. In addition it is expensive to run then the pumping cost.


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