SeaGen was the world's first large scale commercial tidal stream generator. It was four times more powerful than any other tidal stream generator in the world at the time of installation. It was decommissioned by SIMEC Atlantis Energy Limited in summer 2019, having exported 11.6 GWh to the grid since 2008. The first SeaGen generator was installed in Strangford Narrows between

Strangford Strangford (from Old Norse ''Strangr fjörðr'', meaning "strong sea-inlet") is a small village at the mouth of Strangford Lough, on the Lecale peninsula in County Down, Northern Ireland. It had a population of 475 at the 2001 census. On th ...

and

Portaferry Portaferry () is a small town in County Down, Northern Ireland, at the southern end of the Ards Peninsula, near the Narrows at the entrance to Strangford Lough. It is home to the Exploris aquarium and is well known for the annual Gala Week Fl ...

Northern Ireland Northern Ireland ( ; ) is a Countries of the United Kingdom, part of the United Kingdom in the north-east of the island of Ireland. It has been #Descriptions, variously described as a country, province or region. Northern Ireland shares Repub ...

. Strangford Lough was also the site of the first known tide mill in the world, the Nendrum Monastery mill where remains dating from 787 CE have been excavated.

History

Marine Current Turbines, the developer of SeaGen, demonstrated its first prototype of a tidal stream generator in 1994 with a 15 kilowatt system in

Loch Linnhe Loch Linnhe ( ) is a sea loch in the Highland Council area, in the west of Scotland. The part upstream of Corran is known in Gaelic as (the black pool, originally known as Loch Abar), and downstream as (the salty pool). The name ''Linnhe ...

, off the west coast of

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

. In May 2003, the prototype for SeaGen, '', was installed off the coast of

Lynmouth Lynmouth is a village in Devon, England, on the northern edge of Exmoor. The village straddles the confluence of the West Lyn River, West Lyn and East Lyn River, East Lyn rivers, in a gorge directly below the neighbouring town of Lynton, w ...

North Devon North Devon is a Non-metropolitan district, local government district in Devon, England. Its council is based just outside Barnstaple, the district's largest town. The district also includes the towns of Ilfracombe, Lynton and Lynmouth and Sout ...

, England. Seaflow was a single rotor turbine which generated 300 kW but was not connected to the grid. SeaFlow was the world's first offshore tidal generator, and no larger turbines were installed until SeaGen. The first (and only) SeaGen generator was installed in Strangford Narrows between

and

, in April 2008 and was connected to the grid in July 2008. It generated 1.2 MW for between 18 and 20 hours a day while the tides are forced in and out of

Strangford Lough Strangford Lough () is a large sea lough or inlet in County Down, in the east of Northern Ireland. It is the largest inlet in Ireland and the wider British Isles, covering . The lough is almost fully enclosed by the Ards Peninsula and is linke ...

through the Narrows. During the commissioning of the system, a software error caused the blades of one of the turbines to be damaged. This left the turbine operating at half power until autumn 2008. Full power operation was finally achieved on 18 December 2008. Marine Current Turbines was sold to

Siemens Siemens AG ( ) is a German multinational technology conglomerate. It is focused on industrial automation, building automation, rail transport and health technology. Siemens is the largest engineering company in Europe, and holds the positi ...

in 2012. Siemens sold the company and technology to rival Atlantis Resources ( SIMEC Atlantis Energy) in 2015. The power generation system was shut down, decommissioned, and removed in stages between 2016 and 2019.

Technology

SeaGen generator weighed . It consisted of twin axial-flow rotors, each driving a generator through a gearbox like a hydro-electric or wind turbine. The gearboxes were three-stage, with two planetary and one spur, giving a 69.8:1 speed increase. The turbines rotated at around 12 rpm, each with a 16 m diameter (200 m² swept area). Adding two rotors doubled the power, for less than twice the cost. MCT were thus considering further multi-rotor systems in future, e.g. six 24 m diameter rotors were claimed to generate over 8 MW. The SeaGen turbines had a patented feature by which the rotor blades can be pitched through 180 degrees allowing them to operate in both flow directions – on ebb and flood tides. The company claimed a

capacity factor The net capacity factor is the unitless ratio of actual electrical energy output over a given period of time to the theoretical maximum electrical energy output over that period. The theoretical maximum energy output of a given installation is def ...

of 0.59 (average of the last 2000 hours). The power units of each system were mounted on arm-like extensions either side of a tubular steel monopile some in diameter and the arms with the power units could be raised above the surface for safe and easy maintenance access. The SeaGen was built at Belfast's Harland and Wolff's shipyards.

Environmental impact

SeaGen had been licensed to operate over a period of 5 years, during which it was accompanied by an

environmental monitoring Environmental monitoring is the processes and activities that are done to characterize and describe the state of the environment. It is used in the preparation of environmental impact assessments, and in many circumstances in which human activit ...

programme to determine the precise impact on the marine environment. No major impacts on marine mammals were detected in three-years of operational monitoring. Seals appeared to avoid the device, or transit passed at slack water when the turbine was not generating (i.e. not turning). While there was some small-scale displacement of marine birds, overall numbers in the Strangford Narrows did not change.

References

External links

Marine Current Turbines Ltd
{{Electricity generation in Ireland Tidal stream generators Tidal power stations in Northern Ireland Scottish inventions