WAVE ENERGY Wave energy can be considered as a concentrated form of solar energy.
Winds are generated by the differential heating of the earth and, as they pass
over open bodies of water, they transfer some of their energy to form waves.
Energy is stored in waves as both potential energy (in the mass of water
displaced from the mean sea level) and kinetic energy (in the motion of the
water particles). The amount of energy transferred and hence the size of the
resulting waves depends on the wind speed, the length of time for which the
wind blows and the distance over which it blows. Power is concentrated at each
stage in the transformation process, so that the original solar power levels of
typically – 100 W/m
2
can be transformed into waves with power levels of over
1000 kW per meter of wave crest length.
Wave energy converters extract energy from the sea and convert it to a
more useful form, usually as fluid pressure or mechanical motion. This requires
an interface where the force (or torque or pressure) of a wave causes relative
motion between an absorber and a reaction point. There are over 1000 patents
for very varied designs of wave energy converters. However, several
comprehensive reviews of wave energy show that wave energy is mainly at the
27
R&D stage, with only a small range of devices having been tested or deployed
in the oceans. Of these, the main types are: