Introduction about Marine Energy

Marine energy offers a clean and renewable power source from which to produce electricity. Oceans provide an enormous energy conversion potential: wave energy alone could technically reach a worldwide potential of 2 TW according to a 1993 estimate by the World Energy Council. The International Energy Agency believes that marine energy could play a sizable role in the world energy mix by 2030. Worldwide research is very active and accelerating. In Asia marine test centres are being set-up and regular conferences dedicated to Asian marine energy research and applications (e.g. AWTEC) focus regional and international researchers on the Asian issues.

Two kinds of energy are available in the ocean: thermal energy from the sun's heat, and mechanical energy from the tides and waves. The different ways to harness energy from the ocean are the following:

    Mechanical power:
  • Tidal Power: a dam can work with the water level difference between high and low tides. 'La Rance' barrage in France has been for long the largest tidal power converting station in the world (total capacity: 240 MW), containing a basin where the water level varies from 4m to 13.5m.
  • Tidal Currents: devices/turbines convert energy from currents in the same fashion as wind turbines, but submerged and converting energy from a water flow (instead of an air flow for wind devices).
  • Wave Power: the energy available from waves can be converted mechanically into electricity. Several projects are being funded for this promising technology, such as the 'Wave Hub' (England).
  • Salinity Gradients: also called 'Osmotic Power', energy is produced from the difference in the salt concentration between seawater and river water through an osmosis process. The commercial viability of this energy conversion method is still under study, the main problem being the membrane cost.
    Thermal power:
  • Ocean Energy Thermal Conversion (OTEC): covering more than 70% of Earth's surface, oceans act like gigantic solar collectors. The temperature difference between the warm surface water and the cold deep waters creates thermal energy. There is more heat in the ocean than what is needed to power the entire world.