Marine renewable energy, comprising wave and tidal energy, is a massive untapped resource in the UK. Europe holds 20% – 30% of global tidal resources, 80% of which is located in and around the coastlines of the UK and France. Estimates suggest that, if fully exploited, wave and tidal power could supply at least 10% of the UK’s electricity. If utilised, wave and tidal power has the potential to make significant contribution to the mandatory target set by the EU of 15% renewables contribution to total UK energy consumption by 2020.
Wave Power
The power of the waves is readily visible on nearly every ocean shore in the world. Much research has gone into developing technologies to harness the power of these waves energy and transform it into electricity for domestic and commercial use. These technologies fall broadly into three categories:
Machines which channel waves into constricted chambers. As the waves flow in and out of the chamber, they force air in and out of the chamber. These airflows are in turn channelled through a specialised turbine, which is used to drive a generator. This type of machine is principally designed for use on or near the shore, or for incorporation into breakwaters. Commercially, this kind of machine is the most advanced and is particularly advantageous when incorporated into coastal protection.
Fixed or semi-fixed machines which utilise the pressure differential in the water that occurs at a submerged point as the wave passes over that point. The pressure differential is used by a variety of means to cause a fluid to flow in a circuit, which is then used to drive a turbine and generator.
Machines which utilise their buoyancy to cause movement in a part of the device as it moves up and down in the wave. The movement is used either directly or indirectly to drive a generator.
Tidal Stream Energy
Tidal power can use either conventional or new technology to extract energy from a tidal stream. It is usually deployed in areas where there is a high tidal range. Typically a barrage with turbines is built across an estuary or a bay. As the tide ebbs and rises, it creates a height differential between the inner and outer walls of the barrage. Water can then flow through the turbines and drive generators. Some tidal barrages operate on both the rising and falling tide, but others, particularly estuarine barrages, are designed to operate purely on the falling tide.
It is also possible to make use of the tidal flow that occurs between headlands and islands or in and out of estuaries. It is this application that is the focus of much research and development, and new products for this purpose are now being commercialised. These “in-flow” tidal turbines can be arranged singly or in arrays, allowing a range of power outputs to be produced.
For more detailed information and to find out more about this technology please see the REA’s Ocean Energy Group.
