SeaGen, the world's first and most powerful commercial-scale tidal energy turbine, has delivered its two millionth unit of electricity into the UK electricity grid.
The 1.2MW unit, located in the mouth of Strangford Lough, delivered its second GWh in five months of 24/7 operation.
It took from July 2008 until March this year to generate the first GWh, largely through licence restrictions imposed while its affect on marine life was assessed.
"It produces 1.2MW for all current velocities higher than 2.4m/s and remains the world's most powerful tidal turbine," said Peter Fraenkel, technical director of the manufacturer, Marine Current Turbines (MCT) of Bristol.
The firm claims that this is as much electricity as an average off-shore wind turbine of double the capacity, because tidal energy is more consistent and predictable.
Fraenkel added a defensive note:
"It is worth clarifying that the key factor, which fixes the energy capturing capability of a tidal turbine, is its effective rotor swept area; this gives a measure of the amount of the resource that the machine can capture energy from. SeaGen's twin rotors sweep 402m2 of cross-section of current which is much larger than other tidal stream systems which are claimed to be tested shortly."
He is probably referring to Atlantis Resources' AK-1000, which is soon to be installed near Orkney, and is rated at 1MW above 2.6m/s from its tandem mounted rotors which each sweep 250m2.
MCT is working with partners to develop a 10MW tidal farm off Anglesey and to deploy a single SeaGen system in Canada's Bay of Fundy.
It has approval to deploy an array of SeaGens between Orkney and mainland Scotland between 2017 and 2020, which is also where the AK-1000 is due to be installed.
SeaGen has twin power units mounted on wing-like extensions either side of a 3m diameter tubular steel column attached to the sea bed.
The whole wing with its power units can be raised out of the water for maintenance.
Depending on local conditions, SeaGens will be made with blade diameters from 14m to 20m in diameter.
Each turbine drives its generator through a gearbox, and the rotor blades can be pitched through 180° to allow them to operate in both ebb and flood tides.
