Waves are generated by wind blowing across the sea surface, and wave energy is thus a concentrated form of solar energy. The amount of energy in waves depends on the wind speed and power. Deep ocean waves with large amplitude in particular, contain considerable amounts of energy. The strong winds blowing across the Atlantic Ocean, and creating large waves, make the western coasts of Europe ideally suited for wave energy. Other wave-rich areas in the world include the coasts of Canada, Northern United States, Southern Africa and Australia. Wave energy is a relatively new technology and is still in the research & development and demonstration stages, which was pursued vigorously in the 1970s and 1980s. A wide variety of designs have been proposed to harness wave energy with many different extraction methods. However, only a fraction of them have actually been deployed and tested as demonstration units. Wave energy can be converted into electricity in both onshore and offshore systems. A number of onshore systems have been built in Scotland, India, Norway, Japan and other countries using mainly three different designs: (i) systems that funnel waves into reservoirs; (ii) pendulor systems driving hydraulic pumps; and (iii) oscillating water column systems that use waves to compress air within a container . The mechanical power created with these devices is then used directly or via a working fluid, water or air, to drive an electric turbine/generator unit. Shoreline systems have the advantage of being easier to maintain, but the energy potential is higher in offshore locations where several systems have also been tested. Recently, construction of the first commercial wave-farm was started in Portugal , with electricity being generated by devices called Pelamis, named after a giant sea snake in Greek mythology. The name comes from their shape, a series of connected cylindrical modules with a total length of 150 m and a diameter of only 3.5 m. In the initial phase of the project, three of these machines, with each a capacity of 750 kW, will be located 5 km off the coast. The global wave power resource is estimated in excess of 2 TW, with the potential of generating more than 2000 TWh annually (about 10% of the world's present electricity consumption). However, like tidal power, wave power - despite continuing cost reduction - is unlikely to be economically competitive with other power sources in the near future except in special cases such as isolated coastal communities far from any electric grid.
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