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Ocean thermal energy

Tutormate > CBSE Syllabus-Class 10th Physics > Ocean thermal energy

05 Sources of energy



  • The energy available due to the difference in the temperature of water at the surface of the ocean and at deeper levels is called ocean thermal energy (OTE).
  • Tropics receive lot of sunlight which warms the surface of the oceans. Thus the temperature gradient increases.
  • The temperature difference in the oceans between the deep and shallow parts is maximum in the tropics, 20 to 25o
  • The water at the surface of the sea or ocean is heated by the Sun while the water in deeper sections is relatively cool as sunlight cannot penetrate deep into the water. .
  • This difference in temperature is exploited to obtain energy in ocean-thermal-energy conversion plants
  • The efficiency of the system depends on the temperature difference. The more the temperature difference, the higher is the efficiency.
  • The ocean thermal energy can be converted into a “usable form” of energy like electricity.


  • Warm surface water of ocean is used to boil a liquid like ammonia or a chlorofluorocarbon (CFC).
  • The high pressure vapours of the liquid (formed by boiling) are then used to turn the turbine of a generator and produce electricity.
  • The colder water from the deeper ocean is pimped up to cool used up vapours and covert them again into a liquid.
  • According to estimates, ocean thermal energy could contain more than twice the world’s electricity demand.


  • It can be used continuously 24 hours a day throughout the year due to sun and ocean currents.
  • It is a renewable source of energy
  • Its use does not cause any pollution.
  • Mixing of deep and shallow seawater brings up nutrients from the sea floor. The deep water is rich in nitrates and this can also be used in agriculture.

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