Marine renewables refers to the endless source of reliable, clean energy carried by the ocean's waves and tides - the movement of water in the world's oceans creates a vast store of kinetic energy, or energy in motion - and, of course offshore wind must be counted in too. Great news for us all as this energy can be harnessed to create electricity to power our homes, transport and industries.
Marine renewables are also known as marine energy, marine power or ocean power. However, the term ocean energy is reserved for wave and tidal energy only.
Waves are created by the interaction of the wind with the surface of the sea. As the wind blows over the water, it creates ripples. When the wind continues to push against these ripples, it creates a snowball effect resulting in a wave. The size of the wave depends on the speed and duration of the wind and the distance of water it blows over (the fetch). The wave carries kinetic energy transferred from the wind; the bigger the wave, the more energy it holds. This energy can then be harnessed by a mechanical device (known as a Wave Energy Convertor or WEC) to produce electricity. So far, there is no consensus as to the most suitable approach(es) to Wave Energy Convertors and several different methods are being tried out including the Point Absorber and the Pressure Differential approaches.
Tides are created by the interaction of the gravitational fields of the earth, moon and sun. These gravitational pulls cause the coastal water level to fluctuate twice daily, alternately filling and emptying natural basins along the shoreline. Tidal barrages or dams can be used to trap and release large amounts of tidal water. By releasing this trapped water through a turbine, electricity can be generated.
The ebb and flood of the tides also create tidal streams - fast moving currents, which are formed when water is forced through narrow channels such as inlets or straits. The energy carried by these currents can also be used to drive tidal current turbines to create electricity. As with Wave Energy, there are several different ways in which Tidal Energy Convertors or TECs can be configured although there appears to be an emerging consensus around the Venturi Effect and the Horizontal Axial Flow methods.
Wind turbines operate on a simple principle:the energy in the wind turns two or three propeller-like blades around a rotor. The rotor is connected to the main shaft, which spins a generator to create electricity. Offshore wind energy involves turbines fixed to the bottom of the sea by a mooring - this technology is now mature and commonplace. MRIA deals with the new technology in offshore wind: floating turbines and, also, floating turbines linked with wave energy devices known as 'hybrids'.