A team of engineers from Oxford University has come up with a new design for underwater tidal turbines which they believe will be more robust, more efficient and cheaper to build and maintain than anything in operation today.

The tidal turbines in operation today are like underwater windmills, with their blades turning at right angles to the flow of the water. In contrast, the Oxford team’s device is built around a cylindrical rotor, which rolls around its long axis – like the blades of a manual lawnmower –  as the tide ebbs and flows. A pair of these rotors would be connected with a generator in the middle. A turbine with a rotor 10 metres in diameter and 60 metres long could produce around 12MW of power.

"To do that, you only need three foundations and one generator," said Martin Oldfield, senior research fellow of engineering science at Oxford University. "To do that with a [windmill design] would require five foundations and 10 generators."

The device is mechanically far less complicated than anything available now, making less expensive to build and maintain. "The manufacturing costs are about 60% lower, the maintenance costs are about 40% lower," said Malcolm McCulloch, head of the electrical power group at Oxford’s engineering department.

The researchers have successfully tested a one-tenth scale version of turbine. They are now planning to build a half-sixze version that could generate electricity for the grid. Farms of the devices could be in production by 2013.