Marine Energy

MARINE ENERGY

How to use marine power?
By capturing the power of waves and tides and by converting it into clean, pollution-free electricity with special buoys, turbines, and other technologies. Like other renewable resources, tidal and wave energy are variable in nature. Waves are produced by winds blowing across the surface of the ocean. However, because waves travel across the ocean, their arrival time at the wave power facility may be more predictable than wind. In contrast, tidal energy, which is driven by the gravitational pull of the moon and sun, is predictable centuries in advance.

Two other experimental principles:
the first is to use the temperature difference between the ocean surface and the depths.
The second is to use the difference in salinity between fresh water and salt water.

1) Tidal Power:
Tides are caused by the gravitational pull of the moon and sun, and the rotation of the Earth. Near shore, water levels can vary up to 12 metres due to tides.
Tidal power is more predictable than wind energy and solar power. A large enough tidal range (3 metres) is needed to produce tidal energy economically.
The tidal power plants at large use the energy of motion of the sea, whether it is the alternation of flow of the tides, permanent marine currents or movement of the waves. See "Tidal Power"

2) Wave power:
Waves are generated by wind passing over the surface of the sea. As long as the waves propagate slower than the wind speed just above the waves, there is an energy transfer from the wind to the waves.
The kinetic energy produced by the movement of the waves can be converted into electricity. The technology is new and developing, the operating environment is severe and the maintenance and repair costs can be very high. The electricity produced is small and intermittent and the commercial viability is not proven yet. See "Wave Power"

3) Thermal power:
The energy from the sun heats the surface water of the ocean. In tropical regions, the surface water can be much warmer than the deep water.
This temperature difference can be used to produce electricity with a heat pump device. The Ocean Thermal Energy Conversion (OTEC) system must have a large temperature difference of at least 25°C to operate, limiting its use to tropical regions.

4) Osmotic power:
Energy is produced from the difference in the salt concentration between seawater and river water through an osmosis process.  
See "Thermal & Osmotic Power"

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