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The Lynmouth Marine Turbine

The need for the world to use renewable energy to meet the demand for electricity during the 21st century is apparent. Development of wind, wave, and solar power is crucial to help conserve the world’s resources and reduce global warming. However, the power issued by some of these elements is not constant. In particular, the large structure and propeller noise of wind installations intrude on Britain’s decreasing rural environment and power output is unreliable due to variable wind speeds.

The speed of tidal currents is generally low but the volume of water that flows is large and tide movement is regular. Unlike the wind, predictable currents are created when coastal features or islands squeeze the flow although current speed is reduced when the tide turns. These factors and the use of unobtrusive submerged turbines, suggest the marine current installation is an ideal method of creating renewable power. Although a small structure rising above the sea is necessary with these installations their intrusion near Britain’s coastline seems an ideal compromise.

From 800 sites that were considered around Britain’s coastline, a point 1.9 miles (3 km) off the coast in Lynmouth Bay was identified as a perfect location to install the world’s first tidal current turbine. The strong current travelling around the most northerly part of Devon at Foreland Point created the ideal conditions. Experimental devices have been built previously but the Lynmouth turbine was the first commercial installation to be sited in a working environment. The Department of Trade and Industry, the European Union and the German Government with a number of private companies have contributed to the £3.5 million project.

The Lynmouth turbine lowered in operational (right) and raised for maintenance (left) with artist’s impression shown below surface.

Although working on the same principal as a windmill, the marine current turbine does not have to move as fast as a wind turbine. Water is denser than air and is therefore more efficient. On August 28th 2001 a Seacore Ltd rig arrived in Lynmouth Bay to start installation of the turbine. A large hole was drilled in the seabed and reinforced with a steel sleeve. The 80-ton pile structure was lifted by a barge crane and positioned in the sleeve. Concrete grout was pumped between the pile and casing to fix it permanently.
The turbine started generating electricity on 30th May 2002. At a depth of 65-ft (20 m), it presents no danger to shipping. The 52-ft (16 m) blades revolve at between 12 and 15 rpm ensuring there is no interference with marine life. It is made from a composite material and can be reversed by pitching the blades through 180 degrees in order to operate with the current in either direction. Although sitting at least 10 ft (3 m) below the surface, the turbine can be raised above water for maintenance and repair without the assistance of divers.

The control system works automatically and is only attended for maintenance duties but it can be controlled by satellite signals from offices in Bristol and Germany. Managed by Marine Current Turbine Ltd, Bristol, the turbine is a research and development project that has been installed to monitor its behaviour under working conditions. Initial results have exceeded expectations by 27% (2005). The 300 kW generated by the turbine is fed to a dump load ballast situated in the housing on top of the pile and also charges batteries that power the self-contained control system. Because of cost, a cable to land allowing generated current to be connected to the National grid was not installed.
As the Lynmouth Power Station made history with its development of hydroelectricity in the late 19th century, the resort has taken its historic place in the development of renewable energy in the early 21st century.

This is an Excerpt form A Notable History by kind permission of Tim Prosser who has many more interesting and informative publications for sale in the local shops and TIC
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© Tim Prosser




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