by Allen Gates

Created on: January 10, 2011

There are a variety of ways the ocean can be used as a source of energy. The size of the ocean makes the potential seem limitless and appealing in some cases. The technology available is the only practical limit to the amount of energy that can be captured from the ocean.

The ocean is subject to tides from the gravitational forces primarily of the moon. The rise in sea level is a repeatable phenomenon that can be used to capture and distribute energy. This is an appealing source of energy because it can be done on land, which reduces energy transmission costs. As the sea rises to its highest level, reservoirs are opened to capture water and store it at that elevation. When the tide reaches its lowest level the captured water is released through a controlled flow that turns a series of turbines to generate electricity.

Ocean waves can be used to generate electricity in a way similar to the tides. Ocean waves can be captured at the peaks and released at sea level to turn turbines. This output is dependent on the size of the waves which can vary greatly in storms or because of earthquakes. The sea floor can also have wave inducers embedded into the sea floor. The resultant wave can also be allowed to flow into a tube which forces a flow of air to generate the spinning action of turbine. A coast would need many of these, but could produce a sizable portion of consistent energy    

Since the ocean is a large reservoir of water where temperature is dependent on depth, it can be used as part of a heat engine. The closed system consists of a working fluid that is heated by the warmer surface temperature water in a heat exchanger. As a result the working fluid expands and spins a turbine which produces electricity in a generator. The working fluid is subsequently cooled in a second heat exchanger which uses water pumped from the depths of the ocean where it is much cooler. The difference in temperatures is what determines the potential power output of the system. The major challenges are the lack of efficiency of the heat exchangers due to the corrosive nature of the sea environment.

The nature of the ocean is unpredictable with storms, marine life on piping, and how corrosive the water is. Advancement in materials that are resistant to corrosion but that have good heat transfer properties will lead to better efficiencies in the heat engine system to make it more effective in dealing with energy demand. Some sites are naturally equipped for the development of a particular technology. Considerations such as maintenance, construction costs, and potential energy output help to determine which technology should be used when considering the ocean as a source of energy.

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