Marine Current Tuirbines Ltd is both first mover and world leader in its field.  The world's first tidal turbine, tested as long ago as 1994 in Loch Linnhe Scotland, has recently been donated by the Company to the Museum of Scotland.  From it have emerged first the 300kW Seaflow turbine installed in May 2003 and decomissioned in October 2009, and more recently the full-scale commercial system known as SeaGen which was installed in May 2008. 

SeaGen is by far the largest and most powerful tidal turbine in the world with twin rotors each sweeping over 200 square metres of flow.  It also uses the most efficient type of turbine rotors, namely axial flow pitch controlled rotors,  the technology of choice in the wind industry.  As such SeaGen's rotors can achieve over 48% efficiency over a broad range of current velocities and they also offer complete control over the machine - it can be shut down in less than three seconds even with the current at full flow. More details follow.

Tidal turbines such as those developed by Marine Current Turbines Ltd work much like submerged windmills, but driven by flowing water rather than air. They can be installed in the sea at places with high tidal current velocities, or in places with fast enough continuous ocean currents, to take out copious quantities of energy from these huge volumes of flowing water.

The commercial system under development by MCT is known as “SeaGen” .  The prototype is operational in Strangford Narrows, Northern Ireland, and uses twin 16m diameter rotors to develop a rated power of 1.2MW at a current velocity of 2.4m/s.  The system is accredited to OFGEM as an official UK generating station and regularly runs at full rated power.  It has the capability to deliver about 10MWh per tide, which adds up to 6,000MWh per year.  This is approximately the rate of energy capture that a wind turbine of about 2.4MW rated capacity can typically produce. So SeaGen shows that the tides are not only more prodictable than wind but twice as productive.

SeaGen is intended for widespread commercial use and future projects can use variants with twin axial flow rotors of 14m to 20m in diameter (the size depending on local site conditions), each driving a generator via a gearbox much like a hydro-electric turbine or a wind turbine. These turbines have a patented feature by which the rotor blades can be pitched through 180^o in order to allow them to operate in bi-direction flows – that is on both the ebb and the flood tides. The twin power units of each system are mounted on wing-like extensions either side of a tubular steel monopile some 3m in diameter and the complete wing with its power units can be raised above sealevel to permit safe and reliable maintenance.

SeaGen in Strangford Lough