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What is hydroelectric power?

Hydroelectric energy is a type of energy that uses the power of moving water (hydropower) to generate electricity.

In this article you can learn:

  • What hydroelectricity is
  • What happens inside a hydroelectric dam
  • How energy is transferred from one type to another
  • What the advantage and disadvantages of hydroelectric energy are

This resource is suitable for energy and sustainability topics for primary school learners.

Video - Hydroelectric power

In this video, learn about hydroelectricity and how hydroelectric power works.

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Why is hydroelectricity useful?

In 2020, hydropower generated 58% of the world鈥檚 electricity. Renewable types of energy are better for the as they don't run out or produce harmful emissions that damage the .

Hydroelectricity is Scotland鈥檚 second largest energy type (after wind) and is used to produce electricity that can power homes. Scotland generates 85% of the UK鈥檚 hydroelectric power.

How do hydroelectric dams work?

Hydroelectricity is generated at a hydroelectric dam.

Image gallerySkip image gallerySlide 1 of 3, Cross section of a hydro dam with energy transfer: potential to kinetic to electrical, Water stored at a hydroelectric dam has potential energy. When it runs through the dam this turns to kinetic energy. The kinetic energy of the moving water is used to generate electricity.
A dam's water reserve
Image caption,
When blocked behind a dam, water has potential energy. (Pillip / Alamy Stock Photo)

A dam鈥檚 job is to block the flow of a water source, such as a river, creating a large reservoir of water. As the water has nowhere to go, a large amount of water pressure builds up. This generates as the water, if released, will rush down through the dam.

A dam's water reserve
Image caption,
When blocked behind a dam, water has potential energy. (Pillip / Alamy Stock Photo)
Lubreoch Dam
Image caption,
When it is moving, water has kinetic energy. (DGP_Scotland / Alamy Stock Photo)

When it is released, the water travels from the reservoir through a tunnel in the dam called the .

Because the water is now moving, it changes from having potential energy to . This kinetic energy turns the quickly, which then turn the .

Lubreoch Dam
Image caption,
When it is moving, water has kinetic energy. (DGP_Scotland / Alamy Stock Photo)
Inside a hydropower station showing a row of generators and two workers
Image caption,
These are generators in a hydropower station. As generators are turned, they generate electrical energy. (GANG ZHAO / Alamy Stock Photo)

When the generators turn, they convert the kinetic energy into electrical energy.

The then adjust the electricity's voltage so that it can travel long distances through power lines without losing lots of energy. Other transformers then reduce the voltage to a safer level before the electricity enters our homes, schools or workplaces.

Inside a hydropower station showing a row of generators and two workers
Image caption,
These are generators in a hydropower station. As generators are turned, they generate electrical energy. (GANG ZHAO / Alamy Stock Photo)

Hydroelectric dam examples

Image gallerySkip image gallerySlide 1 of 3, Lubreoch dam in Scotland from further down the river, Lubreoch Dam and Power Station in Perthshire, Scotland Lubreoch Dam next to Loch Lyon is one of many dams generating hydroelectric power in Scotland. ( David Paterson / Alamy Stock Photo)
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The advantages and disadvantages of hydroelectricity

Advantages

  • Hydroelectric energy is renewable. Find out what renewable energy is here: What is renewable and non-renewable energy?

  • It is a reliable energy source. Unlike wind and the sun, we know that stored water can provide a 24/7 source of kinetic energy.

  • Once built, it does not produce harmful emissions. This means it does not contribute to the production of greenhouse gases and climate change.

Disadvantages

  • To create a hydroelectric dam, you need to flood an area of land, which damages local environment and animal habitats.

  • In some cases, people may be forced to move home if they live on land that is to be flooded or developed due to the construction of a hydroelectric power plant.

  • Building hydroelectric dams is expensive and uses lots of concrete, which releases greenhouse gases when it is made.

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Key words about hydroelectric energy

鈥 Something that does not run out when used.

鈥 The usual conditions of weather (temperature, wind, rainfall etc.) on Earth over a long period of time.

鈥 Our physical surroundings on Earth, including all living and non-living things.

鈥 Electricity that is produced by the movement of water.

鈥 A large body of water, often man made, that has been created by stopping the natural flow of water.

鈥 A large pipe or tunnel that carries water from the reservoir down to the turbines in the hydro-electric power station.

鈥 A simple turbine has a shaft and blades that turn movement in to energy. Usually water or air push the blades and turn the shaft. Turbines are used to turn the generator.

鈥 A machine that is used to make electricity. When the generator head is turned, this energy is converted to electrical energy.

鈥 An electrical device that is used to transfer electrical energy from one electrical circuit to another.

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Test your knowledge

Quiz

Challenge

Challenge

Draw a diagram of the inside of a hydroelectric dam

Label the working parts using information from the video and key words list.

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