SeaGen: A close look at the industry growing in our waters
In the words of John F. Kennedy: “A rising tide lifts all boats”. Originally a statement about the changes America was going through in the early 1960s, it takes on another meaning when talking about tidal power.
Marine Current Turbines, a British company, has developed a turbine that will capture this powerful natural force much like those used to harness the power of the wind. Their design, SeaGen, was recently given the go-ahead to operate off the coast of County Down, Northern Ireland, in one of the UK’s best areas for capturing tidal energy.
Their turbine sits below the waterline and uses its high torque low speed power to rotate massive blades and transfer that kinetic energy into around 1.2 megawatts of consistent energy.
Moon power some might call it, but for all intents and purposes it is simply harnessing the abundant energy of the oceans. Unlike wind turbines current turbines harness the power of millions of tons of water being pulled by the moons gravity as it circles the earth. As the Moon moves over an area of our planet its gravity pulls the ocean towards it and then when it reaches the other side pulls the earth away from the ocean in the simplest sense, we may not feel the force pulling us towards space but the signs are there to see.
Unlike wind power which is fully dependant on having the right weather, SeaGen works like clockwork, the tides come in and out generating a uniform level of power every day and night at the same times. In fact the only variable is the slight variations in the moons orbit although that has been calculated and monitored for years now. So the main be befit of tidal power is its predictability in both time and force.
I had some questions about the project and was fortunate enough to get arrange an interview with David Ainsworth, project manager of SeaGen, who was very forthcoming and clearly proud of the development he oversees.
What percentage of Britain’s energy could reasonably be provided by Tidal turbines?
“Estimates vary – Tidal turbines could produce 20.6YWhr/annum as stated in the Carbon Trust report CTC799.”
Do tidal turbines produce more energy than wind turbines, when you take the effort of creating and maintaining an underwater device into account?
“It depends on the location, higher energy locations will yield more energy than the same capacity wind turbines (i.e. Strangford), but there are other locations where the yield per MW installed will be the same.
“The installation costs will be comparable as the installation methods are broadly similar.
“Maintenance should be the same at a wind turbine. Our devices are designed to be maintained by low cost vessels, similar if not less expensive than offshore wind.”
Do they generate more energy due to the torque the blades generate rather than speed?
“Correct, sea water is over 900 times more dense than air, the tip speed ration in water is limited by physics, so they cannot exceed significant speeds. The power thus comes from the torque which is a produce of density, velocity and rotor swept area.”
Has anyone considered them to be as much of an eyesore as wind turbines?
“Tidal energy and wind turbines are all part of the energy mix require for energy security and reduce fuel cost volatility leading to high consumer electricity prices. We are unaware of any complaints relating to visual amenity, even in Strangford Lough which is an Area of Outstanding Natural Beauty.”
What has the report on its environmental impacts found?
“There have been no changes in abundance of either seals or porpoises detected which can be attributed to SeaGen; seals and porpoises are continuing to swim past SeaGen, demonstrating a lack of any concern or hindrance.”
I’m told the tides the current SeaGen has been subject to are some of the strongest around Britain. What would be the lowest amount of energy worth harvesting with a water turbine and will that limit the number that can be built and their placement?
“The lowest amounts are purely down to the project economics. As the technology matures the manufacturing and installation costs will reduce and lower energy sites will become economically viable, currently the higher energy sites are deemed the most appropriate for development.”
Were there logistical problems with creating a reliable mechanism that would spend so much time under water?
“The environment in which SeaGen exist has driven the design process, material specifications, cathodic protection and detail. SeaGen has been designed so that the costs of underwater maintenance could be avoided and energy generation maximised; the device is equipped with a hoist that lifts the blades and rotor above the surface of the water for ease of repair and maintenance.”
I have also been confused about the power output; most reports say that it generates 1.2mw or the equivalent of powering 1,500 homes. Does that figure take into account the fact it has not been activated at night or would the actual output once it begins to operate 24/7 be greater than that?
“When it generates 1.2MW it is sufficient for 1,500 homes. It does generate 24/7 and has done so since April 2010.
“The lowest amounts are purely down to the project economics. As the technology matures the manufacturing and installation costs will reduce and lower energy sites will become economically viable, currently the higher energy sites are deemed the most appropriate for development.”
What is the immediate future of the SeaGen project?
“The FEPA license for SeaGen expires in February 2013, MCT will be applying for a 5 year extension.”
Have you been given any other contracts?
“MCT is working on three of their own sites – 10MW Anglesey Skerries, 8MW Kyle Rhea, both for 2014/2015 development and 100MW site at Brough Ness, Pentland Firth.
“MCT would welcome approaches from developers to provide their technology into other projects.”
In the words of MCT, the tides are truly changing on energy production. With several other projects in the pipeline, including deep sea turbines, reliant on currents caused by things much like the North Atlantic drift and other powerful forces of nature, we may come to truly thank the ocean for the plethora of benefits it brings: the most diverse life forms on the planet, infinite discovery, enough food to sustain half the human race, and now, power to light our way into the future from the murky depths of polluted waters and skies.
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