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Hydroelectric Power Plant – Classification, Working & Applications

Hydroelectric Power Plant harnesses the power of water in motion. Water has been a main source of power from thousands of years. Hydroelectric Power has been a significant source of energy across the globe since a long time. This post provides a detailed information about Hydroelectric Power Plant, its classification, working principle, applications, advantages and disadvantages.

What is Hydroelectric Power Plant

Hydroelectric Power Plant is a system in dams and works by obstructing the river flow which causes to increase and store water in the Dams. This is Potential Energy. The water is made to fall from a height which constitutes Kinetic Energy. This Kinetic Energy is then converted to Mechanical Energy by the Turbines. Generator is responsible in converting this Mechanical Energy from the Turbine into Electrical Energy.

Intro to Hydroelectric Power Plant

Fig. 1 – Introduction to Hydroelectric Power Plant

Hydroelectric Power Plants generates electricity for home consumption or business needs. The flexibility of generating the electricity usually is either in a large scale or in a smaller scale depending on the usage. In 1879, the first commercial Hydroelectric Power Plant was built at Niagara Falls. Although every passing year, there has been continuous improvements  doing rounds for safer and efficient utilization.

New Hydro (1)

Fig. 2 – Basic Block Diagram of Energy Conversion in Hydroelectric Power Plant

Classification of Hydroelectric Power Plant

The classification of Hydroelectric Power Plant is done with various criteria. Either by the storage capacity and the water flow or through the technologies applied. Let us go through both the criteria.

Hydroelectric Power Plant is classified based on:

  • Availability of Water Flow
  • Availability of Water Head
  • According to Load Type


Classification of Hydroelectric Power PlantFig. 3 – Classification of Hydroelectric Power Plant

Classification of Hydroelectric Power Plant Based on Availability of Water Flow

This is of three types. They are:

  • Run-Off- River Power Plant without Pondage
  • Run-Off-River Power Plants with Pondage
  • Reservoirs Power Plant

Run Off River Power Plant without Pondage

In this type, the water availability plays a very important role. Here the Power Plant works only when there is enough water since there is no storage or pondage facility available. The facility is placed where there is connectivity directly to the river or pond. The development cost of this plant is cheaper compared to the full time plant. The objective of such a plant is to utilize excessive water during the flood situation or the rainy season.

Run Off River Power Plants with Pondage

The pond is used as storage for the water along with increasing its capacity. This type of plant is used mostly during the fluctuating load period depending on the pondage size. These types of Power Plants save the conservation of coal.

Reservoirs Power Plant

Reservoir Power Plants are across the globe in maximum numbers. In this, the water is stored behind the dam which is available throughout the year. This Power Plant is used during the peak consumption of electricity as well as during the base period.

Classification of Hydroelectric Power Plant Based on Availability of Water Head

They are of 3 types:

  • Low Head Hydroelectric Power Plant
  • Medium Head Hydroelectric Power Plant
  • High Head Hydroelectric Power Plant

Low Head Hydroelectric Power Plant

The Propeller Turbines are used for the Low Head Power Plant. The dam is placed just ahead of the water resources such as the pond or the river. The water level is directed to the Turbine through the Penstock.

Low Head Power Plant

Fig. 4 – Working of Low Head Power Plant

Medium Head Hydroelectric Power Plant

This power plant has a Forebay created mainly to store water. They are the storage tank which taps the river water which goes to the Turbine through the Penstock. The Forebay serves as a surge tank.

Medium head

Fig. 5 – Working of Medium Head Power Plant

High Head Hydroelectric Power Plant

The dam constructed usually is for maximum reserve water level. The Surge tank stores the additional water which would be required during the peak load time with the supply to the Turbine.

High head

Fig. 6 – Working of High Head Power Plant

Classification of Hydroelectric Power Plant Based on Load Supply

There are 3 types of load supply types mentioned below:

  • Base Load Supply
  • Peak Load Supply
  • Pumped Storage

Base Load Supply

This type of Power Plant is a large capacity plant providing extensive supply. There is a Base portion to the load curve of the Power Plant. This sort of Power Plant is suitable for the constant load.

Peak Load Supply

As the name suggests, the Power Plant is suitable for the peak load curve. This needs a big capacity water storage facility.

Pumped Storage

The demand for the electricity is never on a decline. However, the consumption changes during the day and the night with the use of electricity. To match this demand the pumped storage method is utilized. Here, the water is kept in reserve for the high demand periods which comes from the Turbines to back up a storage pool which is situated above the power plant. This is done during the night when the consumption is low. The water is let back out when the demand is high usually during the day.

How does Hydro Electric Power Plant Work

The concept of how the Hydroelectric Power Plant works is straightforward and simple, however the operation of the same is quite complex. The Plant is usually custom made according to the plant priority and capacity. They are usually relied on the monitor, the control system and the improvement conditions to the smooth operation of the plant.

Complex systems like the monitoring, control and improvement of conditions which ensures the smooth running of the Power Plant. The moving parts go through a rigorous wear and tear which is minimized by the bearing and the lubricating systems. The hydraulic systems are in charge of opening and closing the pen-stock gates. To keep the temperatures in control, the cooling systems are monitored to prevent overheating of the transformers, the cables and so on.

Working Of Hydro

Fig. 7 – Operation of Hydroelectric Power Plant

The Hydro Electric Power Plant consists of a Dam, Reservoir, Turbines and Generators. The main concept is that the reservoir stores the water (fuel) and under controlled conditions, the water is fed as input to the Turbines. This also serves as a Decanter.

The water from the Reservoir is transferred through the Dam Gates and the Pen-stock to the Turbines. With all the water processing taking place, there is a Filtering system which ensures a clean and relatively free of suspended solids which could damage the Turbine’s blades. The Hydraulic systems play an important role, consisting of the governor (controls the flow of water through the turbine), brakes, gates which help in the inflow and the outflow of the water to the reservoir.

The conversion of the Kinetic energy into Mechanical energy from the movement of the water fall is done through the Turbine. The Turbines are connected from the Shaft to the Rotor of the generator which converts to the Electricity from the mechanical energy. Turbines are usually custom made according to the needs of the Hydro Electric Power Plant.

Applications of Hydro Electric Power Plant

The applications of Hydroelectric Power Plant include:

  • Unlike other source of energy, Hydroelectric Power Plant helps in generating Eco Friendly Energy.
  • They help in creating Recreational Facilities.
  • It also helps in Flood Risk Management.
  • The water from the dam is used for Agricultural Irrigation Facility.
  • It helps in generating revenue as the location of the Plant creates a tourist spot.

Advantages of Hydro Electric Power Plant

The advantages of Hydroelectric Power Plant are:

  • Supply of electric power is maintained consistently.
  • The water can be stored and used when the demand is high.
  • The longevity of the dams is high which helps in generating electricity at lower cost.
  • While constructing the dam, a lake is formed from the reserve water. This can be converted into a tourist attraction or for water sports.
  • The Hydroelectric Power generation is renewable and is eco-friendly.

Disadvantages of Hydro Electric Power Plant

The disadvantages of Hydroelectric Power Plant are:

  • The constructions of dams are very expensive since it’s in a large scale and has to be well protected. Any slight damage will create a huge destruction not just in the dam but also around its vicinity.
  • The returns on the cost invested on the dams can only be got after a long time. Hence the dam has to be operational for many years to be profitable.
  • At the time of building a hydroelectric power dams, the habitants in and around the area are moved out of their houses and the business. This creates a disturbance.
  • Construction of these dams creates geological damages. Eg, During the construction of Hoover Dam in USA, there was a lot of damages through earthquake and depression on the earth’s surface.
  • Dam’s create a kind of disturbance with neighboring states or countries which connects the rivers. Since the dams are created by blocking the river which creates an irregular supply of water.
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Priya Salian
Priya Salian
Priya is an MBA graduate and has 10 years of work experience in Business Analysis in various MNCs. She is an author, editor and partner at Electricalfundablog.
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