Tidal barrages consist of a large, dam-like structure built across the mouth of a bay or estuary in an area with a large tidal range. As the level of the water changes with the tides, a difference in height develops across the barrage. Water is allowed to flow through the barrage via turbines, which can provide power during the ebb tide (receding), flood tide (allowing water to fill the reservoir via sluice gates during flood tide), or during both tides. This generation cycle means that, depending on the site, power can be delivered twice or four times per day on a highly predictable basis [1].
Tidal barrages represent the oldest and most mature of all the ocean power technologies. The 240 MW tidal barrage at La Rance in northern France has been in operation since 1967. The new 254 MW tidal barrage at Sihwa Lake near Seoul in the Republic of Korea will begin operations in 2011.
The substantial capital costs associated with construction and concerns over adverse environmental impacts make the technology somewhat unappealing in contrast to tidal current technologies.
REFERENCES:
[1] Jean Pierre Frau. (2005) La Rance, a successful industrial scale experiment,, IEEE Transactions on Energy Conversion, 1993, vol. 8: pp. 552-558.
[2] Kwang-Soo Lee. (2006) Tidal and Tidal Current Power Study in Korea, pp. 6-27, 36-43. [Online].Available: http://www.pugetsoundtidalpower.com
