Hydroelectric Power Plant: Definition, Working Diagram or Layout [with PDF]


In 2019, hydroelectric power plants contributed about 18-20% of the total electricity generation in the world. Hydroelectricity is the most widely used form of renewable energy. It is a much more flexible source of electricity and the cost of electricity generation is relatively low. 

Hydroelectric Power Plant Parts or Layout

The Hydro Power Plants consists of mainly six parts:

  1. Dam and Reservoir
  2. Control Gate
  3. Penstock
  4. Water Turbine
  5. Generator
  6. Surge tank
hydroelectric power plant
Source : www.mpoweruk.com

Dam and Reservoir

When we hear the word Dam that means sufficient water storage at some height. When the water from some height is released the velocity increases and is further used for the generation of electricity with the use of a turbine. The dam forms a large reservoir behind it. The height of the water level (called a water head) in the reservoir determines how much potential energy is stored in it.

Control Gate

In simple words, this is like controlling the flow of water. First Water from the reservoir is allowed to flow through the penstock and then to the turbine. The amount of water that is to be released in the penstock can be controlled by a control gate. When the control gate is fully opened, the maximum amount of water is released through the Penstock.


The potential energy of the water is converted into kinetic energy as it flows down through the Penstock due to gravity.

4. Water Turbine or Hydraulic Turbine 

The flow of water from the Penstock is taken into the water turbine. The turbine is mechanically coupled to an electric generator. The kinetic energy of the water drives the turbine and consequently, the generator gets driven.

5. Generator

A generator is mounted in the powerhouse and it is mechanically coupled to the turbine shaft. When the turbine blades are rotated, it drives the generator, The electricity is generated which is then stepped up with the help of a transformer for the transmission purpose.

6. Surge Tank

The Surge tanks are usually provided in high or medium-head power plants when considerably long Penstock is required. A surge tank is a small reservoir or tank which is open at the top. It is fitted between the reservoir and the powerhouse. The water level in the surge tank rises or falls to reduce the pressure swings in the Penstock.

Hydro Power Plant Working

A large amount of water is available in the reservoir before the dam. When water strikes to the turbine blade it starts rotating due to which hydraulic energy is converted into the mechanical energy. This mechanical energy is then converted to Electrical with the help of a generator.

Advantages of Hydroelectric power plant:

The following advantages of Hydroelectric Power Plants :

  1. This power plant is a renewable energy source. The water energy can be used again and again.
  2. They have high efficiency.
  3. The running cost of the Hydraulic turbine is less as compared to other turbines.
  4. The environmental pollution is negligible.
  5. The main advantage of the Hydraulic turbine is that at the turbine place, people can visit and observe & study all the main parts in detail.

Disadvantages of Hydroelectric power plant:

The following disadvantages of Hydro Power Plant are:

  1. Initial cost of installation is very high.
  2. It takes several decades to make profit.
  3. It can be constructed only at a few sites or places where there is a good amount of water available. 

Application of Hydroelectric power plant:

  1. Hydro Plants are the most widely used (18-20% of global electricity consumption) form of renewable sources of energy according to a survey.
  2. A large amount of electricity can be produced by this Hydroelectric power plant with the use of Hydraulic turbines.
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