Renewable energy is expected to play a major part in future energy supplies, both to reduce the impact on the world climate and also to make up for any shortfall in conventional energy sources. Ocean energy has the potential to make a significant contribution to future renewable energy supplies as identified in recent reports from the Intergovernmental Panel for Climate Change and the International Energy Agency. Ocean energy is an emerging industry sector and there are a number of promising developments under way. Significant commercial deployments in the gigawatt range are envisaged over the next 10 to 20 years in Europe, USA, Asia and South America.

The tides, generated by the revolution of the earth in the gravitational fields of the sun and moon, are an enormous resource of renewable energy. Moreover, the times and heights of tides can be accurately predicted well into the future. However, tidal ranges in the oceans vary from 50cm or less to over 10 m, and it is the largest tides that represent the best energy source. This book describes how large tides develop in particular places and how the energy could be extracted by building suitable barrages. The principal features of a barrage and possible methods of operation are described in detail. Although a tidal power barrage would be non-polluting, the resulting changes in the tidal regime would have important environmental effects. These are discussed together with the economics of tidal power. Methods of assessing the likely cost of electricity from any site are set out and applied to possible sites around the world.