Tidal turbines are very much like an underwater windmill where the blades are driven by consistent, fast-moving currents. The submerged rotors harness the power of the tidal streams to drive generators, which in turn produce electricity. Water is 832 times denser than air so consequently tidal turbine rotors are much smaller than wind turbine rotors generate equivalent amounts of electricity, and they can be deployed much closer together.
Devices that harness tidal stream energy present a unique set of engineering challenges in terms of design, installation and maintenance. During operation, the force of the tidal flow in Strangford Lough is equivalent to a 345 mph wind generating a 100 tonnes of thrust on the rotors.