Energy from the Ocean – Different Forms and Limitations

Energy from the Sea

Introduction:

The oceans cover almost 71% of the surface of the Earth, and the enormous amount of water present in them not only acts as a big collector of solar heat energy but also stores large amounts of it due to its high specific heat. In this session, we are going to learn how to harness this energy and its limitations.

Explanation:

Energy from Oceans:

Ocean water can be used as a renewable source of energy. The main forms of ocean energy are described below.

i) Ocean Thermal Energy:

The energy available due to the temperature difference between the deeper levels and the surface of an ocean is called ocean thermal energy.

ii) Ocean Tidal Energy:

The rise of ocean water due to the attraction of the moon is referred to as high tide and its fall as low tide. The enormous movement of water due to high and low tides provides a large amount of energy known as ocean tidal energy. This tidal energy can be utilized by constructing a tidal barrage or dam.

iii) Sea Wave Energy:

The energy obtained from the high-speed sea waves is referred to as sea wave energy. In fact, these high-speed sea waves have a lot of kinetic energy associated with them, which can be used to drive dynamos that convert kinetic energy into electrical energy.

iv) Energy from Salinity Gradient in Seas:

The difference in the concentration of salts in the water of two or more seas is called a salinity gradient. This salinity gradient is nowadays used to obtain energy with the involvement of suitable techniques.

v) Energy from Sea Vegetation or Biomass:

Sea vegetation or biomass is another direct source of energy because the enormous amount of seaweed present in the seawater provides an endless supply of methane fuel.

Limitations of Energy from Oceans

The limitations of energy that can be obtained from the oceans are:

1. Tidal energy: Very few suitable sites are available for the construction of dams, and the power generation is intermittent and not very large.
2. Wave energy: Power output is variable, and the presently available technologies are very expensive.
3. Ocean thermal energy: The conversion efficiency is low (3% – 4%), and a lot of capital investment is required.

Questions and Answers

Question 1: What is the principle of working of the following device in the ocean? Also, mention the energy being used.

Answer: Sea wave energy is being used here. The energy obtained from the high-speed sea waves is referred to as sea wave energy. In fact, these high-speed sea waves have a lot of kinetic energy associated with them, which can be used to drive dynamos that convert kinetic energy into electrical energy.

Question 2: Mention the minimum temperature difference required between surface water and water at a depth of up to 2 km in an ocean thermal energy plant.
Answer: The temperature difference between the warmer water at the surface and colder water at depths up to 2 km should be 293 K (20°C) or more.

Question 3: Explain which energy from the seas is being harnessed here.

Answer: The difference in the concentration of salts in the water of two or more seas is called the salinity gradient.

This salinity gradient is nowadays used to obtain energy with the involvement of suitable techniques.