Survey of Energy Resources 2007
Tidal Country Notes
The large tidal range along the west coasts of England and Wales provides some of the most favourable conditions in the world for the utilisation of tidal power. If all reasonably exploitable estuaries were utilised, annual generation of electricity from tidal power plants would be some 50 TWh, equivalent to about 15% of current UK electricity consumption.
Of six identified sites with mean tidal ranges of 5.2-7.0 m, feasibility studies have been completed for two large schemes: the Severn estuary (8 640 MW) and the Mersey estuary (700 MW) and for smaller schemes on the estuaries of the Duddon (100 MW), Wyre (64 MW), Conwy (33 MW) and Loughor (5 MW). A governmental programme on tidal energy (1978-1994) concluded that given the combination of high capital costs, lengthy construction periods and relatively low load factor (21-24%), none of these schemes was regarded as financially attractive.
Plans have often been formulated for the development of a Severn estuary scheme but to date nothing has ensued, largely owing to ecological concerns.
In recent years much work has been undertaken on the furtherance of tidal stream technology. The Stingray prototype was installed in Yell Sound in the Shetland Islands in September 2002. The 150 kW plant was successfully tested twice and a 5 MW tidal farm was planned for 2005-2007. However, during 2005 the project was suspended, as it was felt to be commercially unviable.
Following preliminary development work during 1999-2002, Phase 1 Seaflow, (2002-2006), the first commercial-scale tidal stream project in the UK, began in mid-2003. An experimental 300 kW turbine was installed 3 km offshore from Lynmouth, Devon by Marine Current Turbines (MCT). Although capable of grid connection, it has used a dump load during the testing period. A large amount of data will have been gathered by the time of decommissioning (3rd/4th quarter 2007 / early 2008).
Building on the experience of Seaflow, Phase 2 SeaGen, (2004-2007), is intended to cover the development of a twin-rotor 1.2 MW grid-connected Commercial Demonstrator. In December 2005 MCT received permission to install a 1 MW grid-connected plant in Strangford Narrows, Northern Ireland. Installation, due to begin in late-2006, was postponed and is now likely to occur in the second half of 2007, taking some six months to complete.
Again, building on the experience of SeaGen, Phase 3 SeaGen 2 is a plan to develop about 10 tidal farms of 5-10 MW capacity. The farms, in part self-financing through the sale of electricity, would ultimately be owned by the utility companies with the power fed to the UK grid. Concurrently, SeaGen 2- type turbines could be used as demonstrator projects in North America (on both Atlantic and Pacific coasts of Canada and the USA), southeast Asia and possibly New Zealand.
A plan for a 10 MW grid-connected tidal farm - the Lynmouth SeaGen Array - has now been 'put on the back burner' in favour of a tidal farm off the coast of Anglesey. In mid-2006, the company announced a feasibility study for 7 units (SeaGens) as a grid-connected tidal farm totalling 10 MW. The site has the potential to be expanded in further phases, possibly up to 100 MW. An Environmental Impact Assessment (EIA) is currently being conducted but once the necessary approvals are granted, an array could be operational by 2009, providing electricity for 4 000 - 6 500 homes on the island.
Study has shown that the island of Alderney has tidal ranges ideally suited to being harnessed. It has been estimated that the island's coastline has a power potential of between 750 MW and 3 GW. In March 2007 it was announced that Alderney Renewable Energy Ltd (ARE) and the OpenHydro Group, an Irish energy technology company, had signed an agreement to carry out the testing and deployment of the Channel Islands' first tidal turbines. Deployment is expected to take place in 2008/2009. As well as providing electricity for the local market, one major aim of a tidal scheme would be to export power to the French national grid.
The European Marine Energy Centre (EMEC) announced in December 2006 that OpenHydro had successfully completed the installation of a tidal turbine. EMEC's Tidal Test Facility is located off the south-western coast of the island of Eday, Orkney. Testing of the system will be undertaken during 2007. The extensive infrastructure will be connected to the local electricity grid and test results sent directly to EMEC's data centre in Stromness.
In February 2007, it was announced that the Scottish Parliament had awarded OpenHydro grant support towards the deployment of a second turbine at the EMEC.
The Government White Paper Meeting the Energy Challenge (May 2007) mentions that the Sustainable Development Commission is carrying out a major study, examining the issues relating to harnessing tidal power in the UK. A wide range of locations and technologies will be taken into consideration, including the possibility of utilising the tidal potential of the Severn Estuary. The report is expected to be published in September 2007.