Question

Ocean thermal energy is due to:
a) energy stored by waves in the ocean
b) temperature difference at different levels in the ocean
c) pressure difference at different levels in the ocean
d) tides arising out in the ocean

Answer 1

Hint: As the word ‘thermal energy’ refers to the energy in a system due to its temperature. Ocean thermal energy is caused due to non-uniform heating of different layers of the ocean.

Complete step-by-step answer:
We know that almost two-thirds of the Earth’s surface is covered by the oceans and the majority of solar radiations hitting the Earth is absorbed by them. The ocean behaves as a giant solar panel that receives the UV radiations from sunlight and due to which the excitation of surface water molecules of the ocean take place which in turn increases its temperature.
The albedo value of the ocean is around 0.6 which states that around $94\%$ of solar radiations that hit the surface of oceans get absorbed by it. The warm water layer near the surface becomes less dense as compared to the layer of cold water at depth.
These variations in temperature in different layers of the water of the ocean creates a temperature gradient between the top and bottom of the ocean which we refer to as the ocean thermal energy.
Hence, option b is the correct answer.

Additional information:
Ocean thermal energy has lately come as a source of clean energy by using the Ocean Thermal Energy Conversion to produce electricity by using the temperature gradient present between the warm surface waters and deep cold ocean water. OTEC plants run a power cycle and produce electricity by pumping large quantities of deep cold seawater and surface seawaters.

Note: As the surface water of the ocean receives the solar radiations or say the photos which get absorbed into it, and can also be confused as the reason for ocean energy but we should keep in mind the energy is due to the temperature gradient generated.