How does Hydropower Work?

Hydropower is merely generating electricity through moving water. The energy in streams and rivers can be quite powerful, making hydropower one of the oldest sources of energy on Earth.

Humans have used water as a source of power for thousands of years. Civilization’s earliest machines were water wheels that were used for grinding grain. The earliest reference to hydropower is in China between 202 BC and 9 AD. Later, waterwheels were adapted to drive sawmills, pumps, and bellows and to provide mechanical power for textile mills.

Then it became an electricity source in the late 19th century, when British-American engineer James Francis developed the first modern water turbine. And, the world’s first hydroelectric power plant began its operation in the United States in 1882.

Hydropower is one of the largest sources of energy, accounting for roughly 20% of the worldwide demand for electricity. In comparison with other sources of Energy, Hydroelectric Power is one of the cheapest, non-carbon emitting, non- polluting, and mature energy sources.

Many people are concerned that blocking the rivers by building huge dams can have severe social and environmental impacts. Some of the issues include blocking passage for migratory fish, changing the river’s average flow, and increasing the possibility of earthquakes and displacement of communities within the area.

How Does Hydropower Work?

To generate electricity, hydropower plants are built on riversides and use dams to collect or control the flow of water. Likewise, the water flows into the dam and goes through a spinning generator. The generator uses the water’s energy motion to produce electricity.

Then, at last, the voltage is passed into power lines and are used for various purposes like; lighting, using different kinds of electric equipment, running industries, etc.

A dam is built along the riverside that causes water to back up behind it, which eventually forms a human-made lake called a reservoir. Some hydropower plants are also called as a run-of-river plant, which means they do not cause water to back up behind them. A portion of the river or stream is channeled through a smaller power plant and later rejoins the river.

There are basically two factors that determine the amount of electricity that is generated, and those are the volume of water flow and the amount of hydraulic head.

The head refers to a distance between the water surface and the turbines. The head depends upon the amount of water in the reservoir. As head and flow increase, so does the electricity generated.

A hydropower system converts the kinetic energy in flowing water into other forms, such as mechanical and electrical energy. This transformation occurs when water flows past a turbine, waterwheel, and propeller.

Generally, hydroelectric power is measured in kilowatt-hours, which is a measure of energy that calculates the electricity used over time. The power output of a hydroelectric power plant is measured in megawatts or kilowatts.

Basic Components of Hydropower Plant

There are several important components of the hydroelectric power plant, which we will go over in this brief and informative article.


The hydropower plants rely on a dam that holds back water, creating a large reservoir. The dam is an essential component of hydroelectric power plants. Usually, the dam is built on a large river that has an abundant quantity of water throughout the year. It should be made at a location where it can get the maximum possible potential energy from water.


Intake is the gates that are built on the inside of the dam. The water from the reservoir is released and controlled through these gates. When the control gates on the dam open and gravity pull the water through the penstock, a pipeline leads to the turbine.


The penstock is the long pipe that carries the water flowing from the reservoir towards the power generation unit, which consists of the turbines and generator. The total amount of power produced in the hydroelectric plant depends on the amount of water flowing through the penstock and the height of the water reservoir. The control gates control the amount of water flowing through the penstock.


Water flowing from the penstock allowed us to enter the power generation unit, which houses the turbine and the generator. The force of water makes it turn the giant blades of a turbine, which is attached to a generator.

There are various kinds of water turbines available, such as the Kaplan turbine, Francis turbine, Pelton wheels, etc. A standard turbine has weighed as much as 172 tons and turns at a rate of 90 revolutions per minute.


The shaft of the water turbine rotates in the generator, which produces an alternating current (AC) in the coils of the generator. The rotation of the shaft inside the generator produces a magnetic field that is converted into electricity with the help of electromagnetic field induction.


The transformer converts the alternating current (AC) that the hydroelectric power generates into the higher-voltage current. The converted power supply that comes from the transformer is connected to the grid and distributed for industrial or domestic use.

Advantages and Disadvantages of Hydropower

Here are some points of advantage and disadvantage of hydropower are mentioned below:


  • Hydro energy does not require any fuel like most other sources of energy.
  • Low operating costs and little maintenance
  • Hydroelectricity does not produce any GHG emissions or cause air pollution
  • It is an attractive source of cheap, non-carbon dioxide producing electricity
  • Hydropower can be produced in almost any size from 1 MW to 10000 MW
  • Hydro power plants have a very long life of around 50- 100 years
  • Hydropower is much more reliable than wind and solar power


  • Hydropower can affect land use, homes, and natural habitats in the dam area.
  • The reservoirs may cover people’s homes, important natural areas, agricultural land, and archaeological sites.
  • It takes a lot of money, time, and construction materials in building a dam and reservoir to support hydroelectric power.
  • Hydroelectric power is the potential for droughts.
  • Low lying areas can become victims of floods due to possible strong water currents.
  • It blocks the passage for migratory fish and changes the river’s normal flow.

By now you must have had a basic knowledge on how a hydropower works. If you have any more concerns, do post it in the comments section below.