What is Tidal Power? Tidal Energy Explained

Tidal energy is formed by the rise and fall of the tides. This creates a surge of water from one location to another. What tidal power does is tap into the energy of this flow of water.

Energy from the tides is completely renewable. This means we can use it again and again, each and every day. It will never run out, unlike other sources of energy such as oil, coal, and natural gas.

How Tidal Energy Works

There are three different ways of generating power from the tides. These involve the use of either tidal turbines, tidal barrages, or tidal lagoons. Let’s now take a closer look at each of these technologies.

Tidal Turbines

Tidal turbines are the most common. They are very similar to wind turbines, only they are placed underwater a short distance from the coast. This type of device is also sometimes referred to as a tidal stream generator.

A tidal turbine generating power from the tides.
Multiple turbines are often used to increase power capacity.

As the turbines harness the energy of flowing tides, they begin to turn. This energy is then transferred to a generator which produces the electricity. Cables are run back to the coast for the electricity to travel along.

Tidal Barrages

Tidal barrages are large structures built across the full width of a river. At high tide, gates known as ‘sluice gates’ are opened to allow water to pass through the barrage. As the tide starts to fall, the gates are closed, trapping seawater behind the barrage.

When barrages trap large bodies of water, they act in a similar way to hydroelectric dams. Engineers can release water through the structure to drive turbines contained within it. The movement of the turbines can then be used for power generation purposes.

A tidal barrage power station built across the Rance river in France.
A tidal barrage power station built across the Rance river in France.

The benefit of a tidal barrage is that electricity generation can be controlled. Engineers can manage the flow of water through the barrage to meet spikes in energy demand.

Tidal Lagoons

Tidal lagoons are natural or manmade bodies of seawater. The process of generating power from a lagoon is very similar to that of a tidal barrage. Turbines are placed around the outer structure and will turn as the tides rise and fall.

This type of tidal power plant is less common than barrages and tidal stream generators.

Environmental Impacts of Tidal Power

Whilst tidal power is still in its infancy, there is already some concern surrounding its impact on the environment. Some of these concerns include the following:

  • Tidal barrages disrupt the natural flow of water in and out of estuaries. This can have an effect on marine life, disrupting life cycles and spawning.
  • Underwater turbines have the potential to kill marine life, much like wind turbines kill birds. This concern is valid amongst all tidal power plants, but larger marine life is likely to only be affected by tidal stream generators.
  • Tidal power produces electromagnetic interference and acoustic disturbances. There is growing evidence to suggest this can alter the migratory path of some marine life. However, this issue isn’t just limited to tidal power. Shipping and sonar technology is the main focus of such research.


There is a huge amount of energy contained within tidal flows. As water levels rise and fall, we can tap into this kinetic energy to generate clean and renewable electricity.

The main ways we can generate electricity from the tides is by using either tidal stream turbines, tidal barrages, or tidal lagoons. Each of these involves the use of turbines powered by the flow of water.

All tidal energy systems have environmental concerns. These mostly relate to the disruption of marine life.