What Is Tidal Energy?

Tidal energy is power that’s created by harnessing the ocean tides. As water levels rise and fall we can convert this movement into electrical energy. Tidal power is inexhaustible, safe and predictable - a great renewable energy source.

The first tidal power generators were built more than 50 years ago, but tidal energy is still a relatively minor contributor to renewable energy production. In this article we’ll explore how tidal power works and why it could become much more important in the near future.

How Does Tidal Energy Work?

Tidal energy works by using moving water to drive power turbines. There are several different techniques that we use to achieve this.

Tidal Stream Generators

Narrow inlets and straits often create fast-flowing tides. Where the water is already moving quickly we can use it to generate power simply by installing turbines in the water.

These can be set up under bridges or underwater so that they don’t get in the way, and are very effective. Because water is much denser than air, a relatively low speed can still create a lot of power. A 10 mph tidal stream can create as much power as a 90 mph gale.

The main drawback to this type of system is that fast-flowing tidal streams are not found everywhere. This limits the number of places where tidal stream generators can be installed.

Tidal Barrage

How Does Tidal Energy Work?

Many places around the world experience tidal activity that isn’t fast enough to drive a turbine. In these situations, we need to create an artificial flow of water by “trapping” the high tide and releasing it later.

The first step is to create a long barrier in the water. This barrier is fitted with sluices which can be opened or closed to allow water through. As the tide comes in it’s allowed to pass through the sluices, so the water level behind the wall rises.

When the tide is at its peak, the sluices are closed. Then, as the tide begins to ebb, the water level outside the wall drops while the level inside it remains the same. Now when we open the sluices, the water inside the wall rushes out quickly enough that we can use it to drive turbines.

Tidal barrage generators are reliable and have been installed in many locations around the world. In fact, the first ever tidal energy power plant was a tidal barrage, built in 1966 in France.

Future Technologies

Tidal barrages and tidal stream generators have been used for decades, but there are new technologies on the horizon that promise to revolutionise tidal energy production.

The first of these is Dynamic Tidal Power. This works by harnessing tidal activity in the ocean itself, rather than on the coast. The technology requires an extremely long (30-50 km) wall to be extended into the sea, which then harnesses the difference in tidal activity on either side of the wall.

The second upcoming technology is the Tidal Lagoon, which operates in a very similar way to existing barrages. However, rather than creating a single straight wall, a tidal lagoon would enclose an area of coastal seabed within a large circular barrier (or even up to three separate barriers). This could enable more efficient energy generation, but no plants of this type have yet been constructed.

Advantages Of Tidal Energy

Inexhaustible Energy Source

The tides are caused by the moon’s gravity, which means no matter how much tidal energy we use there’s no danger of running out.

Reliable, Predictable Power

Unlike solar and wind energy, our tides can be perfectly predicted. This means we’ll always know how much power we’ll be able to make, so we can handle demand much more easily.

Clean Energy

Tidal energy is very clean, even compared to other renewable energy technologies. It produces no emissions, no exhaust fumes, and releases no chemicals into the environment.

Low Production Cost

Once the costs of installing a tidal energy plant have been recouped the cost of energy is very low. It can take several years for the plant to pay for itself, but major installations like the Rance tidal barrage in France have already proven cost-effective.

High Energy Density

Tidal energy requires a relatively low volume of “fuel”, since water drives turbines more effectively than air. This means we’d need to create fewer plants to generate the same level of power.

Drawbacks of Tidal Energy

Environmental Concerns

Tidal energy installations can be detrimental to marine life. Fish can be sucked into turbines or struck by blades, while barrages can cause an enormous impact on the ecosystem by altering the natural flow of water.

No Consumer Options

Unlike installing solar panels on your home there’s no way for everyday consumers to get on board with tidal energy. This makes it harder for people to see the impact it has on their daily life.

System Maintenance

Saltwater can quickly corrode metal parts and marine life such as seaweed and barnacles will often grow on underwater installations. Tidal energy plants can’t simply be left alone once constructed; they require regular maintenance to ensure continued operation.

High Upfront Costs

As with all relatively new technologies, tidal energy plants are still expensive to build. This high initial cost helps to explain why tidal energy is still a relatively minor contributor to renewable energy globally.

What Is The State Of Tidal Energy In The UK?

As an island nation, the UK is well-placed to become a major player in the world’s tidal energy industry. In fact, a recent study identified only 20 places in the world where large scale tidal power arrays could be installed; 8 of these were in the UK.

In addition to this, Scotland is home to the world’s first tidal energy research and testing facility, the European Marine Energy Centre, located in Orkney.

The UK’s tidal energy industry is up-and-coming, and the Government estimates that it could eventually provide as much as 20% of the country’s electricity requirements.

The MeyGen Tidal Project is already under construction, and is predicted to produce almost 400MW of energy by 2021. This would make it the largest tidal energy plant in the world, although proposed projects like the Severn Barrage, which could potentially produce 5% of the UK’s total power requirements.

What’s Next For Tidal Energy?

There are plenty of reasons to believe that tidal energy is the future.

Not only is it reliable and clean, but it is also easily scalable to produce large volumes of electricity.

The new and upcoming technologies outlined in this article, combined with the UK’s excellent tidal energy locations, means that tidal energy could well become one of our country’s most important energy sources.


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