An unusual wave-power system that pumps high-pressure water to an onshore hydroelectric plant recently began feeding electricity into the U.K.’s national transmission system. The 315 kW “Oyster device” is the world’s only functioning hydroelectric wave-powered plant, claims its Edinburgh-based developer, Aquamarine Power Ltd.

Photo: Aquamarine Power Ltd.
The 200-tonne 315-kW wave-power device was installed in Scotland for six months of full-scale demonstration trials.

Oyster’s hydraulic pumping power is generated at the hinge of a seabed-mounted flap that moves with waves. The 10-m-long by 18-m-wide steel flap rises from the machine’s 4.5-m-deep base. Set in 13 m of water, the flap projects above the water surface. For maximum efficiency, “it is really important that the flap penetrates the entire water column and [rises] out of the water,” says the company’s chief technical officer, Ronan Docherty. Maintenance is easier on the Oyster system than on conventional wave-power generators , because the hydoelectric plant is onshore, rather than underwater.

The 200-tonne machine is undergoing about six months of full-scale demonstration trials about 500 m offshore at the European Marine Energy Centre’s (EMEC) proving facility, on Scotland’s Orkney islands. Aquamarine at the same time is designing a device with 26-m wide flaps. Three such 750-kW machines are planned for EMEC in 2011, says Docherty.

Aquamarine has secured an agreement with Dublin-based utility Airtricity Ltd. to co-develop up to 1,000 MW of Oyster sites around the U.K. and Ireland, says Docherty. The company aims to get the Oyster competitive with offshore wind by 2020. With the Scottish government’s relatively generous wave-power incentive scheme, the device should be competitive in that country by 2012-2014, he adds.

Aquamarine acquired rights to the Oyster device from Queen’s University, Belfast, where it was conceived. After several years of development costing over $30 million, the demonstration unit was built last year and installed this summer.

Oyster is EMEC’s only current device, says the centre’s marketing manager, Eileen Linklater. It follows trials three years ago of the similar WaveRoller machine, developed by Finland’s AW Energy, Vantaa. WaveRoller also has a seabed-mounted, hinged wave catcher, but its generating equipment is offshore. Last month, AW secured a $4.5-million European Commission grant to demonstrate a 300 kW device off Portugal, says its chief executive officer, John Liljelund.