Why sustainable energy matters
Why sustainable energy matters

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

Why sustainable energy matters

4.3 Non-solar renewables

4.3.1 Tidal Energy

The energy that causes the slow but regular rise and fall of the tides around our coastlines is not the same as that which creates waves. It is caused principally by the gravitational pull of the moon on the world's oceans. The sun also plays a minor role, not through its radiant energy but in the form of its gravitational pull, which exerts a small additional effect on tidal rhythms.

The principal technology for harnessing tidal energy essentially involves building a low dam, or barrage, across the estuary of a suitable river. The barrage has inlets that allow the rising sea levels to build up behind it. When the tide has reached maximum height, the inlets are closed and the impounded water is allowed to flow back to the sea in a controlled manner, via a turbine-generator system similar to that used in hydroelectric schemes.

The world's largest tidal energy scheme is at La Rance in France, which has a capacity of 240 MW.

Figure 37: The 240 MW tidal barrage installed at the Rance Estuary in France

There are a few other, smaller, tidal plants in various countries, including Canada, Russia and China. The United Kingdom has one of the world's best potential sites for a tidal energy scheme, in the Severn Estuary. If built, its capacity would be around 8600 MW, much larger than any other single power plant, and it could provide about 6 per cent of current UK electricity demand. But the scheme has not yet been implemented, mainly due to its very high capital cost and concerns about the effects on wildlife in the Severn estuary.

Another, newer tidal energy technology involves the use of underwater turbines (rather like submerged wind turbines) to harness the strong tidal and oceanic currents that flow in certain coastal regions. A 10 kW prototype tidal current turbine was tested at Loch Linne, in Scotland, in 1994, and a larger, 300 kW prototype was tested off the Devon coast in 2002.

The technology is still under development, but its prospects are promising.

Figure 38: Artist's impression of an array of undersea tidal current turbines. The twin-rotor turbines can be raised to the surface to avoid the need for underwater maintenance
T206_1

Take your learning further371

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses372.

If you are new to university level study, we offer two introductory routes to our qualifications. Find out Where to take your learning next?373 You could either choose to start with an Access courses374or an open box module, which allows you to count your previous learning towards an Open University qualification.

Not ready for University study then browse over 1000 free courses on OpenLearn375 and sign up to our newsletter376 to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371