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Tide

Orkney is home to the European Marine Energy Centre (EMEC) and this has placed us at the forefront of the development of marine-based renewables – technologies that generate electricity for homes and businesses by harnessing the power of waves and tidal streams. As the first centre of its kind to be created anywhere in the world, EMEC offers developers the opportunity to test full scale grid connected prototype devices in unrivalled wave and tidal conditions.

Tidal energy exploits the natural ebb and flow of coastal tidal waters caused principally by the interaction of the gravitational fields of the earth, moon and sun. The fast sea currents are often magnified by topographical features, such as headlands, inlets and straits, or by the shape of the seabed when water is forced through narrow channels.

The tidal stream devices which utilise these currents are broadly similar to submerged wind turbines and are used to exploit the kinetic energy in tidal currents. Due to the higher density of water, this means that the blades can be smaller and turn more slowly, but they still deliver a significant amount of power. To increase the flow and power output from the turbine, concentrators (or shrouds) may be used around the blades to streamline and concentrate the flow towards the rotors.

The World Offshore Renewable Energy Report 2002-2007, released by the DTI, suggests that while 3000GW of tidal energy is estimated to be available, less than 3% is located in areas suitable for power generation. Tidal current energy is therefore very site specific, optimised only where tidal range is amplified by factors such as shelving of the sea bottom, funnelling in estuaries and reflections by large peninsulas. However, tidal power has the distinct advantage of being highly predictable compared with some other forms of renewable energy which makes tidal energy development an attractive resource option.

Click here to view a description of how the different wave technologies work on the EMEC website.