Everything You Need To Know About The Hydroelectric Energy

As the largest renewable energy source, hydroelectric energy accounts for 22 percent of world’s electricity and generates more power than other renewable sources like solar energy system, wind, geothermal sources.

They are second largest power generation plants after the fuel fired plants. Hydroelectric plant is constructed to produce electric power for base or peak loads and in some cases it carries both loads.

These power plants provide reliable electricity due to wide variety characteristics such as capability of load tracking, peak load supply, quicker operation from start, etc.

Working of Hydroelectric Power Plant

Hydro electric power plant

Hydropower is generated from water flowing from the rivers or some man made constructions in which water is available or stored. Hydro plants comprises of reservoir with dam, penstock, turbine,generator and transmission lines.

A Dam is built near a lake or a big river to store water in reservoir. Dam holds the water and increases pressure of water at the bottom level. It is constructed at higher heights to increase the flow rate.

working of hydroelectric power plant
working of hydroelectric power plant

Water from the reservoirs is carried through penstocks which are huge tunnels to carry water. In these plants, fall of water is used to spin the motor shaft.

When water is fed from the reservoir through tunnels on turbine blades, turbine starts rotating in the direction of water force. Since this turbine is coupled to alternator shaft, electrical energy is produced by the alternator.

Here kinetic energy of the flowing water is converted to electricity which is further transmitted to substations via transmission lines as shown in above figure.

Amount of electricity depends on two factors which are

1. Head of water
2. Rate of water flow of discharge of the water

Head of water indicates distance between water surface and turbine surface and it depends on the available water in reservoir and size of the reservoir. If the head is more, water from a larger height falls with more force, causing increases in turbine rotation.

This results in more results to more power generation. Similarly if the rate or discharge of the water is more, high power is generated since amount of water falling is more and rate of water depends on river capacity such as huge water or more water flowing in bigger rivers.

Parts/Components of Hydroelectric power plant

Hydroelectric power plant construction needs high initial cost to build dam, reservoirs and power house. But once it is started needs a less maintenance charges compared to fuel fired plants.

Some of the main parts or components of hydro plants are described below.



These are the structures built on rivers to stop water flow and to store the water in reservoir. Dam collects and stores the water in rainy seasons and allows continuous operation of plant even during summer seasons. It raises head of the water so the height of water falling increases.

Intake or control gates:

These are used to release or stop the water from dam. Water from the reservoir is released through these gates to the turbine unit. Water gets potential as well as kinetic energies while it flows through control gates.



It helps to increase the velocity of water at higher rate to drive turbines. These are of long pipes which carry the water from reservoir to the turbine house.

Water turbines:

water turbine
water turbine

Potential and kinetic energy of water from reservoir fed on the hydro turbine is converted into rotational motion. When water strikes turbine blades, it starts rotating in the direction of the net force of water.

Different types of turbines include Kaplan, Francis and Pelton wheel turbines. Francis turbine is the most common turbine used in various hydro plants. Type of turbine depends on the head or quantity of water and capacity of the electric power generation.


These are also called alternators where the rotor shaft is coupled with the turbine shaft. Therefore while turbine rotates, it causes to rotate the generator shaft. This rotation generates the electric power which is further transmitted to the substations via transmission lines.

Types of Hydro plants

Hydroelectric power plants are classified into three basic types according to the way they are operating. These generating methods are Run-of-River, storage and pumped storage plants and are briefly explained below.

Run-of-River hydro plants

It is also called diversion type of plant. In this, portion of the water is diverted into canals from the river. These types of plants may not require dam for storage of water.The design and appearance of these plants are different from conventional hydroelectric plants. These are used to supply the power to base load.

Run of river hydro plant
Run of river hydro plant

These plants use small water pond called as Forebay to meet the immediate loads for less time periods. Forebay regulates the water flow to turbine unit so the net power generated is also varied.It reduces the need to construct large reservoirs for high head or surge of water so the initial cost is reduced as compared to storage plants.

Storage hydro plants

This is the most common type of hydro plant that requires dam to store the water in reservoir. Dam facilitates to increase the head as well as the velocity of water.

Penstocks carry water from dam to turbine unit so the power generated depends on the supply of water from reservoir. These are used as base as well as peak load plants. Net power generated is more than the run of river plants.

Pumped storage plants

In this, reversible pump turbine and penstock arrangement exchanges the water between head (upper reservoir) and tail reservoirs. In case of low electricity demand water is pumped to tail pond to the head pond by hydraulic machines. This is done by utilizing the power which is generated from fuel fired plants.

Pumped Storage Plant
Pumped Storage Plant

During peak hours or loads, water is released back from the head pond to the tail pond through penstocks. Energy efficiency of these plants varies between 70 to 80 %. Due to the peak load supplying power with low cost, revenue is increased.

Advantages of hydroelectric power plants

Low operational cost: Once the dam is constructed, electricity is produced at a constant rate because no fuel is required.

• No pollution: A hydroelectric energy plant doesn’t produce any harmful wastes or green house gases; thereby the pollution of the atmosphere is less as compared to thermal and nuclear plants.

Economical power: power is generated with renewable energy, so no fuel cost is required while generating it. This makes the low cost of electricity as compared to hiking prices of fossil fuels.

Storage of water: This plants’ construction also facilitates water for irrigation purpose and reduces the floods, droughts by storing the water. This is very useful because it overcomes the unnecessary wastage of water.

Hope you have had a clear understanding of the basic knowledge about hydroelectric energy and its working.Furthermore any queries regarding electrical and electronic proejcts, please write your suggestions and comments about this article at comment section below. And answer this question if you are interested – On the basis of capacity how hydro plants are classified?

Photo Credits:

Dam on River by wikimedia
Penstocks by wikimedia
Water turbine construction by snowyhydro
Run- of -river plants by wikimedia
Pumped storage plant by tva

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