Engineers at the University of Oxford have developed an innovative horizontal tidal turbine that promises to be significantly more effective than existing axial flow designs.

Their Kepler Transverse Horizontal Axis Water Turbine is a tidal energy “fence” consisting of a string of marine turbines that can operate in shallower and slower-moving water than current designs.

In the “fence” structure, the blades are configured so that the turbine rotor needs no enveloping supporting structure. This leads to low power losses and simple, cheap construction.

A 10 kilometre fence could generate 500-600 kilowatts of electricity.

The turbines sit horizontally beneath the surface of the sea and can be sited in water shallower than the 30 metre depth typically required by current designs. Because the water is slow-moving and the turbines rotate at only about 11 rpm, the company says that fish can safely avoid the turbines’ blades.

Theoretical analysis and modelling, confirmed by testing, has shown outputs several times higher than those achievable by vertical propeller type turbines placed in the same site. This advantage arises from the greater rectangular swept area of a horizontal rotor compared with the depth-limited circular area swept areas of multiple propeller type rotors.