Tides are caused by the effect of the Moon’s gravitational pull on the water of the world’s oceans. A bulge forms at the point below the Moon on the surface of the Earth’s oceans and as the Earth turns its land masses pass through these bulges - this is visible to us as daily high and low tides. The extent of these tides varies over the course of a lunar month but is entirely predictable. Bathymetric and geological coastal features can amplify the effect of these tidal variations leading to higher tidal velocities in certain locations. Many of these locations are well suited for the extraction of energy and the subsequent generation of low carbon electricity. Areas in which a significant tidal resource can be found include Western Europe, Canada, North and South America, China, Korea and Russia – highlighted in the map below.
In addition to its distributed nature tidal energy has some favourable characteristics compared to other renewable energy sources:
- Tidal energy is predictable years in advance, is not seasonally variable and is often available at times when wind or wave energy is not. Due to its predictable nature electricity generated from tidal currents can be expected to have a premium value with electrical utilities and grid operators.
- Electricity generated from the exploitation of marine resources benefits from considerable government financial support when compared with other forms of renewable generation (Renewable Obligation Certificates, Feed-in-Tariffs etc) both in the UK and further afield.
- Due to the high power density of tidal resources it is predicted that the opening costs of tidal energy can be similar to current levelized costs for offshore wind power. Utilising the most efficient technologies at the most resource endowed sites may well see costs below those of offshore wind as wind farms are located in deeper waters