Compared with other renewable energy resources – take solar or wind power as examples – tidal energy is still in the first stages of commercial development. But as the world moves towards a greener economy, tidal power is becoming more in demand in the competitive renewables market.

Currently, the very few tidal power plants in the world are based in Canada, China, France, Russia, South Korea, and the UK, although more are in development. Experts predict that tidal power has the potential to generate 700TWh annually, which is almost a third of the UK’s total energy consumption.

How does it work?

Tidal energy is produced by the natural movement of ocean waves during the rise and fall of tides throughout the day. Generally, generating tidal energy is easier in regions with a higher tidal range – the difference between high tide, when the water level has risen, and low tide, when levels have fallen. These levels are influenced by the moon’s gravitational pull.

 

The moon’s gravitational pull is responsible for the rise and fall of tides. Image: Public Domain Pictures

We are able to produce energy from this process using tidal power generators. These generators work similarly to wind turbines by drawing energy from the currents of water, and are either completely or partially submerged in water.

One advantage of tidal power generators is that water is denser than air, meaning that an individual tidal turbine can generate more power than a wind turbine, even at low currents. Tides are also predictable, with researchers arguing that it is tidal power is potentially a more reliable renewable energy source.

What is tidal power and how does it work? Video: Student Energy

There are three types of tidal energy systems: barrages, tidal streams, and tidal lagoons. Tidal barrages are structured similar to dams and generate power from river or bay tides. They are the oldest form of tidal power generation, dating back to the 1960s.

However, there is a common concern that generators and barrages can damage the environment, despite producing green energy. By creating facilities to generate energy, tidal power centres can affect the surrounding areas, leading to problems with land use and natural habitats.

 

Fleet tidal lagoon in Dorset, UK. Image: Geograph

Since then, technologies in tidal streams and lagoons have appeared, which work in the same fashion as barrages but have the advantage of being able to be built into the natural coastline – reducing the environmental impact often caused by the construction of barrages and generators.

However, there are no current large-scale projects with these two systems, and output is expected to be low, presenting a challenge to compete with more cost-effective renewable technologies.