Marine Current Turbines, has successfully completed the first installation phase of the 1.2MW SeaGen Tidal System, previous post, the world’s largest grid-connected tidal stream system, into the fast-flowing waters of Strangford Narrows off the coast of Northern Ireland.
A crane barge safely positioned the 1000 ton structure onto the seabed in the early hours of Wednesday morning, 2 April, and released its four moorings on 3 April. SeaGen’s location is roughly 1km south of the ferry route between Strangford and Portaferry, approximately 400m from the shoreline.
When fully operational later in the summer, its 16m diameter, twin rotors, one shown above, will operate for up to 18-20 hours per day to produce enough clean, green electricity, equivalent to that used by a 1000 homes, four times greater than any other tidal stream project so far built.
“SeaGen is a hugely exciting project, as well as an historic achievement for both Marine Current Turbines and for renewables in the UK and Ireland. Tidal energy has the great advantage of being predictable and no other system can harness the power of the tidal currents in the way this one can. We take great pride and see enormous potential in the technology and hope it will eventually make a significant contribution to the future energy needs of the British Isles, Ireland and beyond.”
-- Martin Wright, Managing Director of Marine Current Turbines
SeaGen had its final assembly at a dockyard in Belfast. Here it was winched onto a crane barge and then transported to Strangford Narrows on Sunday, 30 March.
The quadropod section that sits on the seabed will now be pin piled. Each of the four pins that secure SeaGen will be drilled to a depth of around nine meters. The installation work is scheduled to take up to 14 days.
SeaGen will enter commercial operation after a commissioning phase of around 12 weeks and supply electricity to the local grid. ESB Independent Energy, the retail subsidiary of ESB, Ireland’s national electricity company, has signed a Power Purchase Agreement with MCT.
SeaGen is based on MCT’s experience with its predecessor, the 300kW Seaflow system installed off Lynmouth Devon in May 2003 and still thriving in open sea conditions.
The technology being deployed by MCT, known as “Seagen” consists of twin axial flow rotors of 15m 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 180o 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 sea level to permit safe and reliable maintenance.
The device is almost entirely submerged, and so has little visual impact, and it creates no noise audible to humans.
Environmental impact studies, carried out by independent consultants, suggest that the technology is most unlikely to pose a threat to fish or marine mammals, or the marine environment in which they live. SeaGen's rotors rotate comparatively slowly at around 10 to 15 rotations per minute, where as a ship's propeller by comparison typically runs 10 times as fast - and moreover Seagen’s rotors stay in one place whereas some ships move much faster than sea creatures can swim. The risk of harming marine wild-life is thought to be extremely small bearing in mind that virtually all marine creatures that choose to swim in areas with strong currents have excellent perceptive powers and agility, giving them the ability to successfully avoid collisions with static or slow-moving underwater obstructions.
MCT takes its responsibilities to the environment seriously. It has established a £2million program to closely monitor the environmental impact of SeaGen, involving scientists from the Queen’s University Belfast (QUB) and from the Sea Mammal Research Unit at St Andrew’s University (SMRU). The program includes the presence of a Marine Mammal Observer on SeaGen at all times during the commissioning phase, when SeaGen will only operate during daylight hours, to observe how the Lough’s marine life interacts with the structure. There is also a sonar system monitoring seal movements, operated by SMRU, which has been partly paid for by the Npower juice fund.
The next project is for a 10.5MW tidal energy farm off the coast of the Welsh island of Anglesey in a fast flowing patch of 25 meter deep open sea known as The Skerries. The project will consist of seven 1.5MW SeaGen turbines, each likely to stand approximately 9 meters above sea level. Studies are now underway and will last throughout 2008, with a consent application likely to be submitted in mid 2009. Construction and commissioning timescales will be subject to the length of the planning process, but it is anticipated this could take place between 2011 and 2012.
MCT and BC Tidal Energy Corporation plans to install at least three 1.2 MW turbines in Vancouver’s Campbell River by 2009, subject to gaining the necessary consents. It is estimated that the tidal energy potential in British Columbia is in the region of 4000MW, making it one of the best areas for tidal energy anywhere in the world
MCT has also signed an agreement with Canada’s Maritime Tidal Energy Corporation to harness the huge tidal currents of the Bay of Fundy in Nova Scotia, Canada. At mid-tide, the flow in Minas Channel north in the Bay of Fundy equals the combined flow of all the rivers and streams on Earth.
Another milestone for renewable energy. Although tidal and current energy are not the biggest sources of renewable energy, they can contribute a significant and very worthwhile amount of power to some areas of the world. Places around Scotland and Ireland, the Bay of Fundy and the west coast of Canada could supply massive amounts of power.