At last­ harnessing the awesome power of the sea to stop global warming

By Jim Kelsey, LPS Special Correspondent

Wavegen’s 500-kilowatt Limpet turbine captures wave energy and converts it into electricity. The technology is to be installed on the Scottish island of Islay to provide electricity for the Inner Hebrides. Photo – Wavegen.

British companies are engaged in exploiting Scottish seas as a renewable source of electric power. Long-term plans range from generating electricity from the waves to harvesting power from the tides. Pulled constantly by the moon’s gravity and warmed by thermal currents, the ocean’s energy is created by winds whipping across its surface. The greater the distances involved, the higher and longer the waves will be.

Energy is stored in the waves until they reach the shallows and beaches, sometimes with destructive force. If only two trillion watts of electricity could be harvested from the sea, it would be the equivalent of twice the world’s energy produced from nuclear, oil, gas, and coal-fuelled power stations.

One metre of a single North Sea wave front is strong enough to power 50 electric heaters. As a general rule, coastlines with an ocean “fetch” greater than 400 kilometres (250 miles), are suitable for exploitation. But even greater energy resources are available between latitudes 30 degrees and 60 degrees in the northern and southern hemispheres. Global warming and international conservation agreements to reduce “greenhouse gases” have encouraged industry to investigate how the oceans’ powerful energies can be exploited economically.

The Inverness-based Wavegen is installing its 500-kilowatt (kW) Limpet turbo generator on the Scottish island of Islay to provide electricity for the residents of the Inner Hebrides islands. Consisting of a collector and oscillating water column, the Limpet uses wave power to force air up through the collection chamber, spinning the pneumatic turbine. It is driven in the same direction regardless of the air flow, sucking the air down and creating electricity as the waves subside.

The company, which has been conducting successful experiments on the island for the past 10 years in collaboration with Queen’s University, Belfast (Northern Ireland), expects to begin feeding electricity to the island’s grid within a year. Wavegen turbines installed in the Azores are now supplying 400 kW of electricity to the islanders. The installation was backed with European Union funding and the company is developing a machine that will float on the sea to generate electricity.

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Queen’s University Professor Trevor Whittaker, who researched the tech nology for the initial trials, said: “Limpet is the culmination of 20 years of research that has been carried out at the university. It is very satisfying to be associated with its first commercial development which will contribute to ‘clean’ energy and reduce the depend ence on fossil fuels and the pollution they cause.”

Islay is also the location for two of Ocean Power Delivery’s wave-energy converters being installed under the 1999 Scottish Renewable Obligation bill in 2001. Called Pelamis and tested by London’s City University, the 375 kW units are similar to a floating “sausage” 12 metres in length and 3.5 metres in diameter. Inside are 10 steel drums connected by hydraulic hinges which pump fluid back and forth as the “sausage” oscillates on the waves. Fluid pressure is used to drive the generators. Pelamis will create more than 2.5 million kilowatts of electricity annually, enough to power 150 to 200 homes. The company is planning much larger units with a 700-megawatt (MW) capacity capable of supplying enough electricity for a small city.

A company called the Engineering Business exploits the moon’s pull on tidal streams to create electricity. The company’s active water column generator (AWCC) is similar to an upsidedown coffee cup sliding up and down a vertical metal pole. Positioned in the offshore seabed, the cup remains below the surface with its large angled wings protruding from either side. The tidal current pushes the cup down, trapping air that is squeezed out through a pipe to the surface.

Rushing upwards at high speed, the air passes through a turbine which does the same job as a windmill, turning movement into electricity. When the cup reaches the bottom of the pole, the wings flip over to be forced upwards by the tidal current sucking air in and generating a continuous power supply for the turbine.

For more information. Web site: www.wave2en.co.uk