Strangford Lough Tidal Turbine, United Kingdom

The world's first commercial-scale tidal turbine is now being commissioned in Northern Ireland's Strangford Lough. The 1.2MW SeaGen project has been developed by Marine Current Turbines (MCT), uses two 600KW turbines, and costs around £8.5m. SeaGen has already briefly delivered 150KW of electricity into the grid while it was being commissioned in July 2008.

However, two turbine blades were damaged during commissioning, and these have been removed from SeaGen's rotor hub for inspection. The damage is thought to have been caused by a fault in the control system, and MCT reports that it came from a combination of circumstances that can only arise during commissioning. Eventual operation should therefore be unaffected, and full capacity is expected at the end of the summer of 2008.

Once fully operational, SeaGen's 1.2MW will supply the equivalent of 1,000 homes. Irish energy company ESB Independent Energy is purchasing the power for its customers in Northern Ireland and the Irish Republic. The grid connection is being undertaken in partnership with Northern Ireland Electricity.

SeaGen uses two rotating blades SeaGen was installed in Strangford Lough in May 2008. It was towed to the mouth of the Lough by a barge. The turbine as a whole weighs 1,000t, and is 43m wide from tip to tip. Designed by engineer Peter Fraenkel, the rotors drive a generator that sends energy along a cable that then links into the national grid across the Lough in Strangford village.

SeaGen has a mobile cross arm on a single supporting pile 3m in diameter and 9m above the average sea level. The twin rotors begin to generate electricity once the tide runs faster than 1m/s. At maximum speed, the tips move at around 12m/s – around 1/3 of the average wind turbine speed. The two rotating blades turn at 14rpm and drive a gear box system.

Built at Belfast's Harland and Wolff's shipyards, the birthplace of the Titanic, SeaGen takes around 14 days to install with the system literally being bolted onto the Lough's bed. The process takes so long because the team putting it into place has to overcome the very tides they are hoping to harvest for the national grid.

Technical challenges to tidal wind farm

The marine environment poses a number of unique technical challenges, not least installing SeaGen in an extremely aggressive tide race. The UK government granted £5.2m towards the project SeaGen works much like an 'underwater windmill' with the rotors driven by the power of the tidal currents rather than the wind.

Strangford Lough has a highly energetic tide race and so is recognised as one of the main tidal 'hotspots' in UK and Irish waters. Other areas are the waters off Anglesey, the Pentland Firth and the Channel Islands.

Marine Current Turbines has established a £2m programme to monitor SeaGen's environmental impact, involving scientists from the Queen's University Belfast and from the Sea Mammal Research Unit (SMRU) at St Andrew's University.

The programme 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 it interacts with the Lough's marine life.

There is also a sonar system monitoring seal movements, operated by SMRU, which has been partly paid for by the npower juice fund.

Northern Ireland Electricity has provided funding of £500,000 for the project as part of NIE Smart. NIE Smart (Sustainable Management of Assets and Renewable Technologies) encourages the development of renewable energy and energy efficient alternatives throughout Northern Ireland.

Project planned for Anglesey

It is claimed that tidal power could supply up to 10% of the UK's energy within ten years, and SeaGen is the world's first commercial tidal stream energy generator. It is more than four times as powerful than the world's second most powerful tidal current system, the 300KW SeaFlow that was installed off Lynmouth on the north Devon coast more than five years ago.

The system will act as a prototype for even larger installations. Based on the Strangford Lough experience, the company plans to scale up the technology to build a 10MW tidal power farm within the next three years and wants to have 500MW of tidal capacity by 2015. Marine Current Turbines' next project, announced in February 2008, is a joint initiative with npower renewables to develop a 10.5MW project using several SeaGen devices off the coast of Anglesey, north Wales.

It is hoped the tidal farm will be commissioned around 2011 or 2012. The company is also investigating the potential for tidal energy schemes in other parts of the UK, and in North America.

Marine Current Turbines is based in Bristol, England. The company was established in 2000 and its principal corporate shareholders include BankInvest, ESB International, EDF Energy, Guernsey Electricity and Triodos Bank.