Underwater turbine trial off Devon coast offers new hope in hunt for clean energy

The world's first underwater, rotating turbine that uses tidal energy to generate electricity has been installed off the coast of north Devon.

At peak output the turbine can produce enough electricity to power 300 kettles, although it is not due to be linked to the national grid until August.

Marine technologists estimate that a national network of similar tidal turbines installed off the coasts of Britain could generate about 20 per cent of the country's energy needs - roughly the combined output of the UK's nuclear generators. The ebb and flow of the tide spins the blades of the 16 metre-wide turbine at between 12 and 15 revolutions per minute, which is believed to be too slow to pose a hazard to fish and other marine wildlife yet fast enough to drive electricity generators.

Engineers have installed the 300 kilowatt turbine three kilometres (1.9 miles) north-east of the fishing town of Lynmouth as part of a test to see if the idea is practical and economically viable. Financed through the Government, the European Union and private investors, the £3m structure is mounted on a pile driven into the seabed. The turbine is immersed at a depth of more than 20 metres - deep enough not to be a danger to shipping.

George Gibberd, a senior engineer at Marine Current Technologies, a member of the consortium that developed, built and installed the tidal turbine, said the structure should have minimal impact on the environment. Mr Gibberd said: "There is no source of power generation that is without some sort of impact on the environment, but generally speaking this is a fairly benign machine.

"Now that we have it working, we are contracted to do a test programme to look at how it works and how it is affected by such things as marine growth and debris damage."

If all goes to plan, the next stage is to build a twin turbine on the same pile.

Eventually they could be the prototypes for a national network of between 8,000 and 10,000 machines generating about 10 gigawatts of electricity.

Unlike wind generators, which rely on the vagaries of the weather, tidal turbines have the advantage of producing highly predictable amounts of energy, although there will be about six or eight hours of each day when they fall idle as the tide turns.

Mr Gibberd said up to 30 sites off the coast of Britain were suitable for tidal turbines, which must be immersed in deep water where there is a strong tidal flow.

The economies of scale suggest that tidal turbines could be built and installed for about £1m - a third of the cost of the Lynmouth machine - making a national network a financially sound prospect.

The idea was the brainchild of Professor Peter Fraenkel, technical director of Marine Current Turbines.

He is a visiting fellow of Southampton University in the civil and environmental engineering department and has been developing tidal turbine technology for more than 20 years.