The energy from the sea can be obtained mainly in three forms:
Tidal energy,
Wave energy, and
Ocean thermal energy.
TIDAL ENERGY
WHAT ARE TIDES?
The alternate rise and fall of sea levels due to the gravitational forces of the sun and moon along with the rotation of the earth are known as tides.
It usually occurs twice on a lunar day at a particular place.
High tide is the rise of the sea level and low tide is the fall of sea level.
WHAT IS TIDAL ENERGY?
The phenomenon of the level of water in the sea rises and falls is called as high and low tides and the difference in sea-levels gives us tidal energy.
Tides are a regular phenomenon and can be predicted well in advance over months and years.
So, the energy from the massive movement of water can be harnessed and converted into usable form.
Tidal energy is harnessed by constructing a dam or tidal barrage across a narrow opening to the sea.
A turbine fixed at the opening of the dam converts tidal energy to electricity.
During high tide, when the level of water in the sea is high, sea-water flows into the reservoir of the barrage and turns the turbines o produce electricity.
During the low tide, when the level of sea-water is low, the sea-water stored in the barrage reservoir is allowed to flow out into sea.
This flowing water also turns the turbines and generates electricity.
Thus, as sea-water flows in and out of the tidal barrage during high and low tides, it turns the turbines to generate electricity.
ADVANTAGES OF TIDAL ENERGY
It is an inexhaustible and environment friendly source of energy.
It is highly predictable.
The energy density is high.
It has low operation and maintenance costs.
LIMITATIONS OF TIDAL ENERGY
There are very few sites around the world which are suitable for building tidal barrages.
The rise and fall of sea-water during high and low tides is not enough to generate electricity on a large scale.
The construction costs are high
It has a negative influence on marine life forms.
The sea wave intensity is variable.
WAVE ENERGY
The waves are generated by strong winds blowing across the sea.
Wave energy is obtained by the kinetic energy possessed by huge waves near the seashore to generate electricity.
A wide variety of devices have been developed to trap sea wave energy for rotation of turbine and production of electricity.
