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ELECTRICITY FROM OCEAN CURRENTS

The oceans of the world constitute an important renewable energy source. There are various types of ocean energy. These include wave energy, hydrothermal energy, tidal energy and ocean current energy.

     

      Wave energy is really concentrated wind energy and can be used to produce electricity or be directly coupled to the drive of the prime mover, as in the case of wave-powered desalination. The Eastern Caribbean can be classified as a low to medium source of wave energy and there is significant potential along the eastern and northern coasts of the chain of  islands.

      

      Hydrothermal energy requires a significant temperature differenntial which is used to drive power plants similar to those used in steam power plants. It becomes feasible only where the sea is quite deep and hence has limited applications in the Caribbean area.

      

      Tidal energy arises from the gravitational pull of the sun and the moon and the tidal currents are used to drive a turbine to produce electric power. In the Caribbean area, tidal variations are not significantly high.

      

      Ocean currents are driven by wind and the heating, by the sun, of the waters near the equator. It may also occur from variations in water density and salinity.Some examples of ocean currents include the Gulf Stream, the Florida Straits current and the Guiana current which flows past T&T. Unlike tides and waves, ocean currents are relatively connstant and flow in one direction only and hence the complexity of design is reduced in that the input forces and flows are fairly constant.

      

      The very variable nature of renewable energy sources like solar, wind wave and tidal makes the system design difficult due to storage and matching requirements’ though these challenges are being overcome as solar and wind have become commercial technologies and there are several promising pilot projects in the lattter two.

      

      Ocean current energy technologies are being investigated in the USA, EU, Japan and China. The total worldwide power in Ocean currents has been estimated to be approximately 5,000 GW (gigawatts). One kilowatt is 1,000 watts. This can be viewed as the power required to light 1,000 hundred-watt bulbs. One megawatt is 1,000 kilowatts and one gigawatt is 1,000 megawatts, the equivalent of five trillion hundred-watt bulbs. To put this resource in further perspective: at a 40 per cent overall efficiency, this source of energy can provide each person in the world today with the energy to light up approximately 320 hundred -watt bulbs.

     

      Of course there are serious  issues to be resolved before largescale applications can be considered. These include the impact of such installations on marine ecology, maritime boundaries, shipping and fishing and the impact of slowing the ocean currents (due to energy extraction).

      

      Ocean current speeds are generally lower than wind speeds but the density of water is over 800 times that of air.  By way of example, the energy available in a 12 miles per ocean current is equivalent to that contained in wind blowing at 110 miles per hour (hurricane force wind). Unlike wind which varies in geography, magnitude and direction, ocean currents are relatively

     

THOUGHTS

. Ocean current is a large renewable energy resource available to T&T.

. A renewable energy policy needs to be developed that focuses on offshore renewable energy technologies.

. The expertise and resources to research and develop ocean current energy extraction technology is available locally.

constant in location, speed and direction which lead to a high capacity factor (capacity factor is the fraction of time the turbine is actively generating energy).

     

      Unlike windmills, for instance, and solar dishes the water turbines used to generate energy from the ocean currents are located below the surface of the water and hence have minimal visual impact and are significant1y less affected by hurricanes. T&T is directly in the path of the Guiana current which ranks as one of the most powerful ocean currrents in the world.The southern channel, between Trinidad and Venezuela, acts as a nozzle for the flow of the sea water (a nozzle increases the flow velociity; think garden hose nozzle) and this nozzle effect is enhanced by the outflow of the Orinoco River. The result is an increased speed of outf1ow into the Soldado area of the Gulf of Paria. This southwest Soldado area is thus an ideal area for the application of an ocean current extraction system.

      

      Several pilot projects are being considered worldwide including the Bahamas, which two years ago announced plans that it would purchase renewable energy to be generated from ocean currents.A 110 kilowatt prototype is to be deployed off the coast of South Korea. The experience and data obtained from this prototype will be used to inform a planned power station project that, in the medium term, will generate several hundreds of megawatts.  T&T is endowed with both finite petroleum and infinite renewable resources.

     

      Due to the limited (translated small) size of the land mass, it should pursue as a matter of policy the utilisation of offshore renewable technologies for power generration. Of course residential and special applications of wind and solar should also be pursued for direct residential applications. As ocean current teclnology is in its infancy, we have a wonderful opportunity to develop this techhnology as the commercial benefits are significant. We do have the necessary expertise and resources for this venture.

 

Prof Prakash Persad is the director of Swaha Inc



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