Everything You Need To Know About The Hydroelectric Energy

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

They are the second-largest power generation plants after the fuel-fired plants. The 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 the wide variety of characteristics such as the 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 comprise the reservoir with a dam, penstock, turbine, generator, and transmission lines.

A Dam is built near a lake or a big river to store water in a reservoir. The dam holds the water and increases the 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, the fall of water is used to spin the motor shaft.


When water is fed from the reservoir through tunnels on turbine blades, the turbine starts rotating in the direction of the 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 the 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

The Head of the water indicates the distance between the water surface and the turbine surface and it depends on the available water in the 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 in more power generation. Similarly, if the rate of discharge of the water is more, high power is generated since the amount of water falling is more and the rate of water depends on river capacities such as huge water or more water flowing in bigger rivers.

Parts/Components of Hydroelectric power plant

Hydroelectric power plant construction needs a high initial cost to build a 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 the water flow and to store the water in the reservoir. Dam collects and stores the water in rainy seasons and allows continuous operation of the plant even during summer seasons. It raises the 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 the 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 a higher rate to drive turbines. These are of long pipes which carry the water from the reservoir to the turbine house.

Water turbines:

water turbine
water turbine

The potential and kinetic energy of water from the 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. The 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 the 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, a portion of the water is diverted into canals from the river. These types of plants may not require a dam for the storage of water. The design and appearance of these plants are different from conventional hydroelectric plants. These are used to supply the power to baseload.

Run of river hydro plant
Run of river hydro plant

These plants use a small water pond called Forebay to meet the immediate loads for fewer periods. Forebay regulates the water flow to the 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 a dam to store the water in the reservoir. Dam facilitates increasing the head as well as the velocity of the water.

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

Pumped storage plants

In this, the reversible pump-turbine and penstock arrangement exchanges the water between the head (upper reservoir) and tail reservoirs. In the case of low electricity, demand water is pumped to the 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. The energy efficiency of these plants varies from 70 to 80 %. Due to the peak load supplying power at a 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 greenhouse 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 purposes and reduces the floods, droughts by storing the water. This is very useful because it overcomes the unnecessary wastage of water.

I hope you have had a clear understanding of the basic knowledge about hydroelectric energy and its working. Furthermore any queries regarding electrical and electronic projects, please write your suggestions and comments about this article in the comment section below. And answer this question if you are interested – Based on 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