Of all renewable energy sources, marine energy (also called ocean, or maritime energy) is the one that still has the furthest to go to achieve commercial maturity. The most important advantage of marine energy is that it is a source of high energy density, which means that a large quantity of energy can be obtained from a small occupied surface area. The chief disadvantage is the the great difficulty in extracting the energy in such a hostile environment. Very little marine energy is currently being tapped, with total installed capacity limited to a few pilot plants located in a small number of countries. Marine energy stands at a position of technological divergence, with many ideas under development, none of which has proven a clear technological leadership. Marine energy takes different forms: Waves: Waves are caused by the action of the wind on the surface of the sea. They can travel hundreds of kilometres Tides and sea currents: The displacement of large masses of water caused by the gravitational pull of the sun and the moon causes locally periodical variations in the sea level and currents that can be used for energy purposes. Sea currents also lead to phenomena such as differences in the density and salt content of the water, differences in temperature, evaporation and rotation of the Earth Thermal gradient: Solar radiation on the sea causes differences in temperature between water at the surface and at the bottom of the sea of over 20ºC Saline gradient: At river mouths, there are major differences in the salt concentration between the sea water and the river water The only marine energy which can be harnessed in the Basque Country is wave energy: the intensity of the other phenomena is not sufficient to allow them to be used. In the field of wave energy, two global "firsts" are being implemented in the Basque Country: Mutriku Wave Energy Plant and bimep -- Biscay Marine Energy Platform

• published: 28 Mar 2012
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