The ocean is also a powerful source of renewable energy. The energy of the ocean can be harnessed in three basic ways: using wave power, using tidal power, and using ocean water temperature variations.
Different types of waves are continuously generated in the ocean. The back-and-forth or up-and-down movement of waves can be captured to harness the wave power by using it to force air in and out of a chamber to drive a piston or spin a turbine that can power a generator. Kinetic energy exists in the moving
waves of the ocean. That energy can be used to power a turbine.
When the wave rises into a chamber, it forces the air out of the chamber. The moving air spins a turbine which can turn a generator. When the wave goes down, air flows through the turbine and back into the chamber through doors that are normally closed.
This is only one type of wave-energy system. Others actually use the up and down motion of the wave to power a piston that moves up and down inside a cylinder. That piston can also turn a generator. Presently in some cases the wave power is being used in small lighthouses and warning buoys.
The tidal energy of ocean can also be harnessed by trapping water at high tide and then capturing its energy as it rushes out and drops to low tide. When tides come into the shore, they can be trapped in reservoirs behind dams. And when the tide drops, the water behind the dam can be let out just like in a regular hydroelectric power plant. Presently, the power of the tides is being harnessed to produce electricity in Canada and France.
If you go swimming in the ocean and dive deep below the surface, you will notice that the water gets colder the deeper you go. It is warmer on the surface because sunlight warms the water. But below the surface, the ocean gets very cold. That is why scuba divers wear wet suits when they dive down deep. Their wet suits trap their body heat to keep them warm.
This temperature difference between deep and surface waters in the ocean is also used to extract energy from the flow of heat between the two. The process is called ocean thermal energy conversion (OTEC). Power plants can be built that use this difference in temperature to generate energy. Presently, it is being used in Japan and in Hawaii in demonstration projects.
The energy potential of an ocean, particularly tidal basins, is large. The ocean energy is preferable to that of wind because tides are constant and predictable and that water’s natural density requires fewer turbines than are needed to produce the same amount of wind power.
However, tidal energy systems can have environmental impacts on tidal basins because of reduced tidal flow and silt build up.