Renewable Energy 5 – Ocean and Tidal Energy Generation

Before I begin, I will freely acknowledge that this option is not really great for Colorado or anywhere else in the middle of the Continental USA without expensive electrical  transmission systems.  Having admitted that, it is useful to note that according to the National Oceanic and Atmospheric Administration (NOAA) the official shoreline of the USA is estimate to be 95,471 miles.  That is a lot of constant renewable energy waiting to be tapped.  Unlike coastal wind towers that stand above the water’s surface capturing variable wind currents, most ocean power lies out of sight (an important consideration for those people worried about esthetic vistas) below the surface – wave power may be more visible depending on the technology used.   Again, this is pollution free energy generation once the technology has been built and set in place.    There are three energy sources from oceans:

  • Tidal power: The twice-daily flow of tides (rising and falling of seas due to the moon’s constant gravitational pull) creates energy of motion that can be converted to electricity. Even on a calm day the tides roll in and out with rhythmic constancy (predictable and stable).  Current technology has three different ways to utilize tidal energy: tidal streams, barrages, and tidal lagoons. In essence, what this means is that tidal rises and falls are captured in a system that resembles hydroelectric power, but unlike terrestrial falling water hydro, the incoming and outgoing tidal energy can be utilized.  For most tidal energy generators, turbines are placed in tidal streams and since water is more dense than air, tidal energy is more powerful than wind energy for spinning underwater turbines.
  • Wave power: This is very similar in many ways to tidal power, in that the ocean energy is used to spin a turbine, but in this case the actual wave energy is usually used as an indirect motion to spin the turbine. The incoming waves can enter a chamber where the waves compress the air in the chamber, which is then forced through an opening to spin the turbine in a housing above the water level (often on the edge of the shore).  The air forced in and then pulled back by the wave power can spin the turbine with a gearing shifter that keeps the turbine spinning in the same direction whether the air is moving in or out of the chamber.  Wave energy is produced when electricity generators are placed on the surface of the ocean. The energy provided is most often used in desalination plants (an important potential for clean fresh water in coastal regions), power plants and water pumps. Energy output is determined by wave height, wave speed, wavelength, and water density.
  • Thermal power: This technology exploits differences between warm water (usually at the surface) and cold water (usually down below 15 meters). While not yet commercially developed, the potential is enormous.  The technologies under study can use warm surface water that is piped into facilities where it evaporates volatile substances (e.g., ammonia) to turn turbines.  Cold, deeper water is then used to condense the substances and start the cycle again.  Ocean Thermal Energy Conversion (OTEC) project research has been run in Hawaii and elsewhere, but there are no commercial operations yet, but The OTEC plant located in’s Hawaii’s NELHA plant (in Kailua-Kona) could become commercially operational in the near future.

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