Tidal Energy Potential

Most countries which have investigated the potential exploitation of tidal energy have concentrated on the use of tidal barrages that can be used to control the natural tidal flow, which is directed to drive turbines.

Only around 20 sites in the world have been identified as possible tidal power stations. Three countries have tidal energy schemes in operation: France, with the 240 MW tidal barrage at Rance, the largest tidal power station in the world and the only one in Europe, built in 1966; Canada, with the 20 MW Annapolis tidal barrage; and China, with an 11 MW tidal power scheme of small tidal plants.

Experimental tidal energy projects are being tested in Russia, UK, Australia, USA, Argentina, Canada, India, Korea, and Mexico. Potential sites for tidal energy stations are few and far between, but a number have been identified in the UK, France, Eastern Canada, the Pacific coast of Russia, Korea, China, Mexico, and Chile. Other sites have been identified along the Patagonian coast of Argentina, Western Australia, and Western India.

Tidal ranges along the west coast of England and Wales are unusually large, averaging 7 to 8 metres on the spring tides in several estuaries and as much as 11 metres in the Severn. The Severn estuary is the site for the most ambitious tidal barrage that has been proposed for the UK so far, and it has been discussed for many years.

Tidal energy is expensive to install, costing UK£1.5 /US$2.4 million per megawatt, compared with about US$1 million per megawatt for wind turbines. It also has environmental problems including effects on tidal waters and ecosystems. On the positive side, it is cheap to maintain once installed and the electricity output is completely predictable.

Tidal energy barrages would modify existing estuarine ecosystems to varying degrees, and environmental considerations are some of the barriers which have to be overcome to develop them.