Using the ocean to create energy can yield incredible amounts of energy because of the ocean's size and power. Use of the ocean is also free, besides fixed costs, and inexhaustible.

Ocean-derived energy can be used for electricity production, desalination, and the pumping of water into reservoirs. 

Different types of ocean energy include wave, tidal, and ocean thermal.

  • Wave-

    Renewable energy analysts believe there is enough energy in the ocean waves to provide up to 2 terawatts of electricity. (A terawatt is equal to a trillion watts.)

     

      Offshore mechanisms use bobbing motion to power a pump, these mechanisms can pressurize water and then rotate a turbine. Onshore mechanisms extract energy from breaking waves.  Types of onshore technologies include the oscillating water column that creates pressure differential inside a column half-filled with water, the tapered channel system that creates elevated reservoirs of water, and the pendulor device that powers a hydraulic pump with the movement of a flap that hangs above the breaking wave.
  • Tidal- 

           Tidal energy utilizes barrages and turbines to take advantage of            large moving bodies of water. 

        Tidal energy has an efficiency of 80% in converting the potential             energy of the water into electricity.

        Shrouded tidal turbines (essentially underwater windmills) can               provide energy to remote communities where large civil                         infrastructures are not viable, do not harm wildlife, and have little         visual amenity impact.
 

  • Ocean Thermal- 

           Daily heat in the ocean is equivalent to 205 billion barrels of oil.            By placing warm ocean water in a low pressure container, water            becomes steam which then turns a turbine. This is called an open            cycle. A closed cycle uses warm ocean water to boil another low            pressure liquid, such as ammonia, to spin a turbine. 

PROS:

  • once built, low operation costs
  • essentially inexhaustible
  • huge potential output
  • "fuel" --seawater-- is free
  • can combine energy production with desalination (other social benefits) 

CONS:

  • wave power is low-speed and multidirectional, while most generators operate at high speeds and with constant, steady flow
  • cost protecting devices from storm damage/salt water corrosion
  • high total cost
  • lag time before investment return
  • high irreversible commitment

 

Sources:  

http://www.eere.energy.gov/consumer/renewable_energy/ocean/index.cfm/mytopic=50009

http://en.wikipedia.org/wiki/Wave_power