The rise and fall of water level due to tides can be harnessed to generate electricity; like hydropower it is a clean, reliable and long-lasting renewable and does not pro­duce carbon dioxide. Sites with a sufficient tidal range and area are limited and rep­resent only 10% of the energy that is available from hydroelectricity. One of the best-known tidal power stations was built at the River Rance, Brittany, in 1966 and has been working for over 40 years producing 550 MW (Charlier, 2007).

Wave power

Schemes for the harnessing of the rise and fall of waves are under investigation in a number of countries. Devices for the conversion of wave energy to shaft power or compression have been proposed and a number have been tested.