Wave phenomenon is complex. When wind blows over water, portion of the energy is imparted on the water interface. The continuation of this process keeps on adding momentum to the water body. As a result, the huge waves are formed which swell further when approaching shallow waters. Most of wave power potential is concentrated around coast of Australia, New Zealand, Chile, South Africa, northern coastline of UK and North Western America. This has been verified in a study by Gunnar Mork et al (see the picture).
In the picture only coastal power has been shown. It should be noted that wave power can be collected near shore, off shore and far off shore.
The underlying physics of waves is complicated and can be described as multiphase flow with two distinct phases with a free surface interface. Because of a multitude of random factors, (including wind speed ) that influence waves, it is difficult to predict the size and shape of the wave. In mathematical terms it can be best described as a Stochastic process. However, if we find out the mean values (height of waves, wave period, length of wave front), to some extent wave energy can be estimated.
As wave energy is simply kinetic energy of a moving fluid, the wave energy formula is simply an extension of the well known formula:
K.E = 1/2 *m*v2
The mean value of the height of the waves, time period between the wave are factors that help in simplifying the formula for wave energy. Wave power is measured in Watt/ m or Watt/km. Wave power potential of less than 5 kW/m is considered unfeasible to tap.
P = Power of a wave in deep water, measured in watts
Ρ=Density of seawater (1,025 kg/m3)
g = Acceleration due to gravity (9.81 m/s2)
T= Wave period—the time between successive peaks, in seconds
H = Wave height—distance from trough to peak, in meters
L =Length of wave front (perpendicular to direction of travel, across), in meters
π is the mathematical constant 3.1416
Because the high density of water (800 times more than air), sea waves have the highest energy density among the other renewable energy sources. Under lab conditions, studies by Prof Salter from University of Edinburgh showed that over 81% of wave power can be converted into electricity.