Siemens has recently acquired Marine Current Turbines Ltd., the UK company based in Bristol, which develops and builds tidal power systems. The worldwide potential for power generated by tidal power plants is estimated at 800 terawatt-hours (TWh) annually. That is approximately 25 percent more than the total power demand of Germany and is equivalent to 3-4 percent of global power consumption. Coastal regions with strong tidal currents like those in the UK, Canada, France and East Asia offer major potential for the utilization of this technology.
Marine Current Turbines (MCT) has already implemented a commercial-scale demonstration project with SeaGen in Strangford Lough in Northern Ireland. Since November 2008, two axial turbines with a combined capacity of 1.2 megawatts (MW) have been providing power to approximately 1500 households. SeaGen has to date fed more than three gigawatt-hours of electricity into the grid. Further projects are at the planning stage, including the 8-MW Kyle Rhea project in Scotland and the 10-MW Anglesey Skerries project in Wales.
Tidal turbines generate electricity by utilizing tidal current flows. The SeaGen turbine is fixed on a structure and is driven by the flow of the tides. This technology is similar to a wind turbine, with the rotor blades driven not by wind power but by tidal currents. Water has an energy density that is 800 times higher than that of wind. Twin rotors turn with the tidal current and optimally track the direction and speed of flow thanks to blades which can rotate through 180 degrees. A key advantage is that the generated power is precisely predictable in the tidal cycle.