Working of hydroelectric power plant

In this article we are going to learn how Hydroelectric Power Plant works, what are the requirements of hydroelectric power plant for the selection of site, etc.

ThreeGorgesDam hydroelectric power plant

Hydroelectric Power Plant

In hydropower plant potential and kinetic energy of the water is used to rotate the turbine and hence generator to generate electricity.

Classification of Hydroelectric Plants:

  1. Conventional and pumped storage plants: in the conventional type, water is collected in the dam and its head is used for the rotation of turbine. In lean demand period, water is pumped back using water pump in the storage tank and used in peak demand period for the generation of electricity.
  2. Base and peak load plants: Hydel power plant is used as base load plant in lean demand period where as it can be used as peak load plant when there is shortage of water. Example of base load plant is conventional one and example of peak load plant is pumped storage plants.
  3. Base and head discharge: in hydel power plant potential energy of the water is converted into kinetic energy which is then converted in to mechanical energy and finally to electrical energy. All these energy conversions depend upon two main factors i.e. level of water in tank (head of water) and second is flow of water through the turbine.

Layout of Hydroelectric Power Plant (Hydro Station):

Following figure shows the basic layout diagram of the hydroelectric power plant.

Hydroelectric Power Plant Layout
Layout of Hydro Electric Power Plant

Construction & Working of Hydroelectric Power Plant:

Following are some of the main components of the hydroelectric power plant.

  1. Reservoir: water harvested from the catchment area is stored in the reservoir which is then used to generate the electricity.
  2. Dam: it is made in the path of the river to make the reservoir to hold the rain water.
  3. Spillways: Spillways are made to make the dam safe. When level of water is exceeds some defined point, it will discharge through these spillways.
  4. Forebay: when there is sudden change in the turbine load, in such cases there is need of temporary storage of water. This temporary storage of water near turbine is called as forebay.
  5. Surge tank: surge tank is build in between dam and the valve house. It is used to take care of the system load fluctuations.
  6. Penstock: it is water pipeline carrying water from dam to turbine.
  7. Prime mover or turbine: it is the main part of the power station. It is coupled with the generator. Turbine is rotated by the flow of water. As it is coupled with the generator, generator also rotates which produces electricity.
  8. Powerhouse: it consists of turbine, alternator and electrical equipment.
  9. Tail races: outlet water of the turbine is discharged to the river trough tail races.
  10. Selection of site:

Following are some of the factors that should be considered for Hydropower Power Plant while selecting a site.

  • Availability of water
  • Location of the dam
  • Head of water
  • Storage of water
  • Transport facilities
  • Distance from the load centre

Youtube video to understand working of hydroelectric power plant:

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Working of Gas Power Plant

In this article we are going to learn about how Gas Power Plant works? Gas power plant is also called as gas turbine power plant.

gas power plant
Gas Power Plant

Gas Power Plant:

In the previous article we have seen the overall idea of working of Thermal Power Plant which uses steam energy for the generation of electricity. Today we are going to discuss one more power plant which is known as gas turbine power plant. Gas power plant uses compressed air to rotate the generator and to generate electricity.


Following figure shows the schematic arrangement of a gas turbine power plant.

gas turbine power plant
Gas turbine power plant

Working of Gas Power Plant

In gas power plant air which is also known as the working fuel is compressed using air compressor at very high pressure. This compressed air is then fed into the combustion chamber where the fuel burns and produces hot flue gases (exhausts) at high pressure. It is then expanded in the turbine at high pressure to rotate the turbine. Turbine is coupled with the generator. Therefore when turbine rotates, generator also rotates and generates electricity.

In gas power plant, the compressed air is preheated before going to combustion chamber by the regenerator which uses hot air from the turbine to increase the efficiency.

Some part of the turbine energy is also used to run the air compressor so as to increase the overall efficiency.

Advantages and disadvantages of Gas Turbine Power Plant:

  • No special requirement for site selection. Gas turbine power plant can be built anywhere.
  • Initial cost of gas power plant is lowest as compare to hydel, nuclear or thermal power plant.
  • Running cost of gas power plant is higher.
  • But the maintenance and transmission & distribution cost is low.
  • Impact of gas power plant on environment is lower.
  • Overall efficiency of gas power plant is 40%. Therefore gas turbine power plant is quite efficient.
  • Space requirement is less.
  • Gas power plant is reliable.

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