(a) Ocean waves:
The winds blowing due to sun’s energy over the ocean surface sweep its surface and produce waves.
The movement of ocean waves is associated with a large amount of kinetic energy. It is estimated that 2-3 million megawatts could be generated from the power of waves that strike the shorelines across the world.
However, there are only limited sites where this energy can be harnessed. The areas with an average density of 40 MW per kilometer of coastline are considered economically viable for generating electricity from ocean waves.
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(b) Ocean thermal energy:
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This type of energy arises because of difference in temperature of sea surface heated by sun and colder waters found at ocean depths.
To harness this form of energy devices known as Ocean Thermal Energy Conversion (OTEC) Power Plants are used. To use this plant a difference of 20°C or more between the temperature of surface waters and water at depths of 1000 metres is required.