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What is tidal energy?

Tidal energy is a source of energy powered by the movement of the sea as it rises and falls with the tides.

In this article you can learn:

  • What causes tides
  • How tides are used to generate electricity
  • Where tidal turbines work best
  • What the advantage and disadvantages of tidal energy are

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

Video - What is tidal energy?

Find out about tidal energy and what the advantage and disadvantages of tidal energy are in this short video.

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What causes tides?

Image caption,
Tides are the rising and falling levels of the ocean鈥檚 surface caused by the gravitational pull of the moon. The change between high and low tide happens twice a day.

in the ocean are caused by the of the moon pulling the Earth towards it.

Where oceans face the moon, the water is pulled most and builds up in a bulge. This is a high tide. The Earth is pulled towards the moon more than the ocean on the opposite side of the planet. This causes another high tide.

As the moon moves around the planet, these tides move around with it, causes two high tides and two low tides each day. This moving water has a lot of that can be used to generate electricity.

Learn more about tides and the power of the sea with Isla and Connor: Coastal erosion: What are tides?

Image caption,
Tides are the rising and falling levels of the ocean鈥檚 surface caused by the gravitational pull of the moon. The change between high and low tide happens twice a day.
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What is gravity?

Gravity is a force that pulls objects towards each other. Earth鈥檚 gravity is a bit like a magnet which keeps our feet on the ground and is the reason we don't float away. into space when we jump.

It is quite a weak force for small objects but gets much stronger for larger objects. We only really notice the gravity of massive objects like the Earth, moon, Sun or other stars and planets.

Gravity is an important force in the solar system and universe. In our solar system, the Sun is the biggest object and has the strongest gravity. This keeps all of the planets in their orbit around the Sun.

The moon is much smaller than the Sun. The reason its gravity is strong enough to cause tides is because the moon is about 400 times closer to us than the Sun.

Not sure what gravity is? Find out with this short video.

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How do the tides create electricity?

The rise and fall of the tides causes water to move back and forth. This can be used to turn the blades of tidal . Each turbine turns a which converts the kinetic energy of the movement of the water into electrical energy. This electricity is then passed through underwater cables and is then used to power homes.

Image gallerySkip image gallerySlide 1 of 5, A tidal turbine out of water, in Scotland, A tidal turbine being prepared for installation near Nigg, Scotland. (arild lilleb酶 / Alamy Stock Photo)
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Where do tidal turbines work best?

The Pentland Firth
Image caption,
The Pentland Firth is known for the strength of its tides, which make it a good location for a tidal power plant. (Doug Houghton Orkney / Alamy Stock Photo)

The best place to put tidal turbines is somewhere with strong tides.

Tides are stronger where the sea narrows between different areas of land. This means lots of water has to pass through a small gap. More moving water has more kinetic energy to spin the turbines, so more electricity can be generated.

The Pentland Firth between the north coast of mainland Scotland and Orkney is home to a number of tidal turbines.

Visit the Pentland Firth with Isla and Connor as they explore features of coastal erosion on a journey from Stromness in Orkney to Scrabster in the north of mainland Scotland: Coastlines: erosion

The Pentland Firth
Image caption,
The Pentland Firth is known for the strength of its tides, which make it a good location for a tidal power plant. (Doug Houghton Orkney / Alamy Stock Photo)
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The advantages and disadvantages of tidal energy

Advantages of tidal energy

  • Very reliable. There are two high tides and two low tides every day of the year, everywhere in the world, no matter what the weather.
  • Unlike renewable energies that rely on the wind and sun, tidal power is constant as the tides are always changing and will never stop.
  • It is a clean and renewable source of energy.

Disadvantages of tidal energy

  • Constructing a tidal power plant can be very expensive.
  • Tidal power plants can have a negative effect on the environment and marine life.
  • Tidal power plants can only be built in locations where there are strong tides, meaning their locations are limited.
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Key words about tidal energy

鈥 These are the rising and falling levels of the ocean鈥檚 surface caused by the gravitational pull of the moon.

鈥 An invisible force which pulls objects towards each other. It is only noticeable for large objects like stars and planets鈥 The Earth鈥檚 gravity is what makes things fall and what keeps us on the ground.

鈥 Gravitational pull is the force that pulls objects towards planetary bodies such as planets and moons.

鈥 Energy that an object possesses because of its movement. A ball being thrown through the air has kinetic energy because it is moving. When water moves this is also an example of kinetic energy.

鈥 A simple turbine has a shaft and blades that turn movement into 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.

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Test your knowledge

Quiz

Challenge

Challenge

What would you ask a scientist?

Imagine you get the chance to ask three questions to the world鈥檚 leading tidal wave scientist.

Think of three questions you would ask him or her about tidal energy.

Can you find the answers to your questions?

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