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Marine (Ocean) Energy

The oceans have an incredible amount of power and energy potential. Even though the marine energy technology has not fully delivered on its potential, there has been, in recent time, a number of areas in marine energy that has kicked off. The UK is believed to be a leading player in Marine energy. Even though its capacity presently is only about 9megawatts, it is on course to deliver about 120MW by 2020. Two of these are Wave energy and Tidal Energy.

Wave Energy: How does it work?
Wave energy (WE) harnesses the kinetic energy in the up-and-down movement (waves) of water in the ocean. The waves are caused by wind action, and wind action is caused by the sun heating the surface of the waters, generating air pressure. This means as long as there is the sun, there will be wind and waves, even though its intensity may vary.

WE locations are best where there are strong winds traveling over very long distances. This makes places like the west coast of UK a great point, because of the winds over the Atlantic.

Wave Energy is captured by devices called Wave Energy Devices. There are several types of Wave Energy Conversion devices including the following:

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A. Point Absorber: This floating structure moves up and down and in all directions. With some conversion mechanisms inside it, power is converted and stored in a hub at the base.

B. The Attenuator:
This floating device also rides the waves, flapping like the wings of a bird, a movement caused by the pounding waves. The kinetic energy in the movement is converted into energy and stored.

C. The Oscillating Wave Surge Converter: This device extracts energy from the waves of the water. It is installed below the water surface, but the current is strong enough to cause it to oscillate.

How does Tidal Energy work?
Ocean tides are caused by the earth’s rotation, as well as the combined gravitational fields of the earth, sun and the moon. This combination shapes the gravitational pull on the earth’s oceans. The oceans tidal stream is even more powerful when wind air pressure systems get involved. Areas with greater current speeds, narrow straits and inlets, as well as channels between islands are perfect locations for installing tidal energy structures.

Some tidal structures (or devices) look a lot like wind energy blades, but this time, installed under water to harness the kinetic energy in the oceans currents. Unlike in wind turbines, the blades in tidal energy devices move a lot slower because of the high density of the medium (water). However, they carry a lot of power.

Some tidal converters work just like the wind turbines. Kinetic energy from the spinning of the blades, caused by the currents is tapped with the help of some converters inside of the spinning structures to generate electricity.

Examples of tidal energy converters include the Horizontal Axis Turbine, Vertical Axis Turbine and the Oscillating Hydrofoil.

The world’s biggest Tidal Power Plant is the Sihwa Lake Tidal Power Station in South Korea, with 254MW output capacity. There is also a 240MW output capacity plant in France called La Rance Tidal Power Plant.

What are the problems with Marine Energy?
Marine energy comes with its own problems and challenges.
For example, the unpredictable changes in wave patterns (extreme tides to very calm waters can cause huge structural damage.

It can also cause overload operation problems. There is also the lack of data and information on this new area, and many governments and businesses are less encouraged to jump on board.

Then there is also the environmental concern such as marine energy facilities may affect wave hydrodynamics, create artificial habitats, concerns with marine animals, noise and so on.

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