Ocean waves generate huge amounts of energy and are one of the most omnipotent forces known to mankind. Close to 75% of the earth’s surface is covered by water and if fully exploited, about 40% of the world’s power demand can be satisfied by this – equivalent to the energy produced by as much as 700 average nuclear power plants. This is different from the tidal energy, a kind of energy which is drawn from the equipments placed underwater that capture the movements of the ocean currents resulting from the Earth’s rotation and gravity.
How is Wave Energy created?
When the winds hits the ocean surface, some of the motional(Kinetic) energy of the wind is transferred to the ocean waves. This is the basic method how waves are created and how energy is imparted to them. Wind energy forms due to the high and low pressures created by the Solar energy. Hence wave energy as well as the wind energy are grouped under the list of Renewable energy sources.
How does Wave Power Works?
Wave energy can be extracted in different ways depending on the type of waves. Onshore and Offshore waves are these types of waves and different methods need to be employed for each to get energy from them. Onshore waves are the waves that are present near the shore. Offshore waves are those waves in the middle of the ocean and move in an up and down motion rather than crashing over themselves.
There are over a thousand different methods which have received patents, but less than 1% of these methods have been successful. In reality, there are two main methods employed and are the most promising of all. They are:
Oscillating Water Column: This is an onshore device which draws energy from the waves hitting the shore. An oscillating water column is lowered partially into the water. It has a hollow upper part filled with air and is open below the water surface. When the waves crash into the shore, the water level rises up and decreases with the level of waves. When the level of water rises up, the air in the upper portion is compressed and is pushed out of the device. A turbine Well’s turbine is located in the path of air-flow which is rotated by the air and produces power. On the other hand, when the water level falls down, vacuum is created in the chamber and this sucks the air into the device. The air which is sucked also flows through the turbine and rotates it. Hence power is produced during both the motions. A Well’s turbine is a specially designed turbine whose shaft rotates in the same direction no matter which direction the air flows. A generator is located at the powerhouse which converts this mechanical energy into more useful electrical energy.
Line Absorber: The Line absorber consists of a series of cylindrical structure, floating on the surface of the ocean rising up and down along with the motion of the waves. This assembly can be best visualized as a giant snake floating on water. Hinges are used to connect the individual units together. Cables are used to attach the device to the seabed, holding it in one place. As the wave approaches the assembly, the unit which touches the crest of the wave (the upper half) rises up and the unit in contact with the lower half goes down. The hinges between the cylinders are connected to pumps present in them. The pump pumps oil through pipes to a hydraulic motor as the cylinders move and electricity is generated. This electricity is carried to the land via cables attached to the seabed.
Buoyancy Point Absorber: The buoyancy unit is one which floats on the surface of the ocean and follows the vertical movements of the waves. This floater is linked to a cam-like device which converts the reciprocating movement to rotational movement of the shaft which produces power. This is by-far the easiest way to extract energy offshore.
How effective is Wave Power?
As of now, wind energy is mankind’s biggest renewable source of energy. All ocean energy resources combined would create energy 800 times more powerful than wind. That said, ocean energy is definitely the only hope of mankind’s fast depleting energy resources. When averaged over a square meter, solar energy yields 150 watts, wind energy gives 300 watts while wave energy has the potential to create over 30,000 watts of energy.