Ocean Energy 2005 – from the NRG Expert Historical Energy Data Series
Ocean energy is mostly in an experimental stage. Many ideas have been generated and a lot of experimental projects are being funded both by governments and commercially. These range from technologies and schemes which produce small amounts of energy for local, often dedicated use, to large scale projects which can or will be capable of supplying energy in quantities sufficient to feed into a grid. Energy can be harvested from the oceans in four basic ways, with a multitude of variations.
Most countries which have investigated the potential exploitation of tidal energy have concentrated on the use of barrages to create artificial impoundments 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. Tidal power works rather like a hydro-electric scheme, except that the dam is much bigger. A huge dam, called a “barrage”, is built across a river estuary. When the tide goes in and out, the water flows through tunnels in the dam. The ebb and flow of the tides can be used to turn a turbine, or it can be used to push air through a pipe, which then turns a turbine. Large lock gates, like the ones used on canals, allow ships to pass.
The largest tidal power station in the world and the only one in Europe is in the Rance estuary in northern France. It was built in 1966. A major drawback of tidal power stations is that they can only generate when the tide is flowing in or out – in other words, only for 10 hours each day. However, tides are totally predictable, so other power stations can be scheduled to generate at those times when the tidal station is out of action.
From the NRG Expert Historical Energy Data Series