Tidal power

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.

 Tidal Barrages:

Operating principle of a tidal power plant

A simple generation system for tidal plants involves a dam, known as a barrage, across an inlet. Sluice gates on the barrage allow the tidal basin to fill on the incoming high tides and to empty through the turbine system on the outgoing tide, also known as the ebb tide. There are two-way systems that generate electricity on both the incoming and outgoing tides.

A potential disadvantage of tidal power is the effect a tidal station can have on plants and animals in the estuaries. Tidal barrages can change the tidal level in the basin and increase turbidity (the amount of matter in suspension in the water). They can also affect navigation and recreation. 

     
Tidal Fences:

Operating principle of tidal fences

Tidal fences can also harness the energy of tides. A tidal fence has vertical axis turbines mounted in a fence. All the water that passes is forced through the turbines. Tidal fences can be used in areas such as channels between two landmasses. Tidal fences are cheaper to install than tidal barrages and have less impact on the environment than tidal barrages, although they can disrupt the movement of large marine animals.

SeaGen Tidal Turbine

Tidal Turbines:

Tidal turbines are basically wind turbines in the water that can be located anywhere there is strong tidal flow. Because water is about 800 times denser than air, tidal turbines have to be much sturdier than wind turbines. Tidal turbines are heavier and more expensive to build but capture more energy.

Photo credit: subseaworldnews.com

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