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Swell builds for wave power

Wave power has still to be proved as a viable renewable energy source on a large scale. But its promise is growing, writes Ian Lewis

WAVE POWER has still to be proved as a viable renewable energy source on a large scale. But its promise is growing, as a variety of imaginative schemes undergo demonstration-scale tests in anticipation of improved funding, following last month's climate change talks in Copenhagen.

One of the latest technologies to hit the water is the Oyster, a hydro-electric wave device developed by Scotland-based Aquamarine Power, based on research carried out at Queen's University, Belfast. The device became operational at the European Marine Energy Centre (EMEC), Orkney Islands, off the north coast of Scotland in November.

Wave devices such as those being developed by UK company Pelamis and US/UK firm Ocean Power Technologies (OPT) generate electricity at sea by bobbing up and down on the surface of the ocean, with the electricity then being sent to shore by cable. The Oyster, however, sits on the seafloor in water around 10 metres deep, producing power through the movement of a mechanical hinged flap reaching up to the surface, which is pushed back and forth by the motion of the waves. The flap drives hydraulic pistons on the seabed to send high-pressure water through a pipeline to an onshore turbine, where power is generated.

Utility-scale wave farms

Aquamarine says the device could be used in utility-scale wave farms with a capacity of 100 megawatts (MW) or more of power. However, at this early stage of development, the sole Oyster in use at the EMEC has a maximum capacity of about 2 MW. Backed by funding from the Scottish government, the next generation Oyster 2 is expected to be installed within two years.

A device using a similar principle is also being developed in the US by Independent Natural Resources (INRI). Its Seadog pump also sits on the seabed, but uses the motion of the waves to drive a piston moving vertically, which powers a pump on top of the device. This pump can then be used either to send water for power generation or for other uses such as seawater desalination. Based on tests in the Gulf of Mexico, INRI estimates a 1 square mile field of its pumps could generate 50 MW to over 1.5 gigawatts, depending on wave conditions.

The development of OPT's floating Powerbuoy device also received a boost in November, when the Australian government awarded the company a A$66.5m ($61m) grant to develop a utility-scale project off the coast of Victoria. The company plans to start building the 19 MW project before mid-2010 and says that amount of power could serve the needs of around 20,000 homes.

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