Harnessing the power of oceanic waves For decades researchers have tried to harness the power of the ocean to generate electric power. Waves and tides constantly release gigantic amounts of energy. These have, as yet, barely been tapped. According to estimates arrived at by the World Energy Council (WEC) in London, wave power stations could satisfy around fifteen per cent of global energy demand. According to research estimates, Europe’s coastline alone is pounded each year by waves with an aggregate energy clout of around a billion megawatt hours. Properly exploited, this energy could cover five to ten per cent of power con-sumption in the EU countries. And this would be possible without producing any climate-killing CO2. Renewable, non-polluting and climatically compatible, this energy source is sure to trigger growing interest in harnessing water power in the years ahead. Electricity produced from wave power currently costs up to ten euro cents per kilowatt hour - about twice as much as for windgenerated current. The goal within the next ten years is to get the price down to the level of coal and gas, which is still below that of wind energy. To achieve that, enormous technological progress must be made and vari-ous methods are employed to turn wave power into energy. Pelamis, the steel sea snake The method developed by the Scottish company Pelamis Wave Power Ltd. (PWP) sounds unabash-edly simple. Four gigantic steel cylindrical sections are linked together by means of hinged joints. Floating snakelike on the surface of the water, the joined sections are moored to the seabed in such a way as to always bear the full force of oncoming waves. The rise and fall of the waves causes the individual cylindrical sections to react against themselves sequentially. Hydraulic cylinders located in three power modules situated between the floating sections absorb the movement. Their pistons pump a special fluid through the hydraulic system, powering six hydraulic generators to produce 750 kilo- watts of electric power. A seabed cable links the off-shore power station to the power grid on land. Pelamis, as the steel sea snake is called, converts as much as eighty per cent of the wave force ab-sorbed into electrical energy.The offshore power station performs most efficiently at a distance of five to ten kilometres from the coast. The sea there is about fifty to a hundred metres deep and the waves are three to six metres high, optimum conditions for this kind of energy generation. At the same time, the cost for the seabed cable is lower here than it would be if the station were located further out. PWP uses ContiTech Air Spring Systems technology in its Pelamis power station.The bellows provide an ultra-flexible and hard-wearing seal between the steel cylinders and the hydraulic units. Bernd Stöter, responsible for the project at ContiTech, explains: "The demand was for oil- and sea-water-resistant bellows with stainless steel connecting parts. Bellows like that are something com-pletely new." In developing these special bellows, engineers at ContiTech Air Spring Systems were able to draw on the experience gained with and the range of materials used for another product family, namely that of expansion joints. "Working together with PWP, we were able to hold to a very tight de-velopment schedule for the desired bellows." Since 2004 a 120-metre-long fire-enginered monster has been surfing the waves off the coast of the Orkney Islands. In endurance tests conducted here, at the northernmost point of Scotland where the North Sea meets the Atlantic, the Pelamis prototype has demonstrated its performance capability and durability. At the moment, three such sea snakes - each 140 metres long and weighing 750 tonnes - are being installed off the coast of Povoa de Varzim in northern Portugal; it marks the first instance of commercial use of the energy generation system. If Pelamis measures up to expectations, 28 additional machines will be joining those already in service. And Scottish Power will be setting up the world’s biggest wave farm off the coast of Orkney. Speed Link InfoService Request more information by e-mail Reader Service No. Reader Number Email Address 01233    Tell a friend about this article:
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