MeyGen ^{The Tide of Change in Caithness}

Marine Power

There is often confusion regarding the different types of tidal power, and indeed between tidal current power and wave power. To summarise:

• Wave energy converters harness the motion of waves generated by wind and swell.
• Tidal lagoons and tidal barrages use barriers to create an enhanced difference in the height of the water surface as the tide enters or exits an enclosed area.  The water on the high side can then be released through turbines in the barrier to generate electricity.
• Tidal current turbines are powered by the natural horizontal flow of water as our seas and oceans move in response to the interaction of the Earth, the Moon and the Sun. Unless taken to extremes, it does not require blocking of any waterways, and hence does not have the adverse environmental effects that can be associated with tidal barrages.

Sea water is 832 times denser than air and so a 5 knot ocean current has more kinetic energy than a 350 km/h wind.  Therefore ocean currents have a very high energy density and a smaller device is required to harness tidal current energy than to harness wind energy.

Tidal current energy takes the kinetic energy available in currents and converts it into electricity. As oceans cover over 70% of Earth’s surface, ocean energy (including wave power, tidal current power and ocean thermal energy conversion) represents a vast source of energy, estimated at between 2,000 and 4,000 TWh per year, enough energy to continuously light between 2 and 4 billion 11W low-energy light bulbs.
Both the U.S. and the U.K., for example, have enough ocean power potential to meet around 15% of their total power needs.

For tidal current energy, there is an estimated 50,000MW or approximately 180TWh per year of economically exploitable resource available worldwide.

For more information on both tidal and wave energy within the UK please click on the RenewableUK website, link below:

http://www.bwea.com/marine/index.html