Question

Which of these is a renewable source of energy?

• A. coal
• B. CNG
• C. petroleum
• D. solar energy

Answer 1

The correct option is D

solar energy

The explanation for the correct option:

Option D: Solar energy

1. The sources of energy that are inexhaustible, i.e., which can be renewed in a short interval of time are called renewable sources of energy.
2. The earth receives energy from the sun in the form of heat and light throughout the year. Solar energy can be used directly in two ways -
   1. It can be used by converting sunlight into heat. Solar heating devices have been designed to store sunlight over a large area. For example – A solar cooker is a device that uses solar energy for cooking food.
   2. It can also be used by converting sunlight into electricity.
      1. The solar panel is a device that converts solar energy into electric energy.
      2. Solar panels are used to run the instruments on a satellite in space.
      3. It is also used to run street lights and water pumps.
      4. Solar cells are used for operating electronic watches and calculators.

The explanation for the incorrect options:

Option A: Coal

1. The sources of energy that are exhaustible, i.e., which cannot be replaced or renewed in a short interval of time are called non-renewable sources of energy.
2. Coal, petroleum, and natural gas are called fossil fuels because they are formed from plants and trees which were once living organisms.
3. Coal is formed over a period of millions of years. Generations of trees that died were gradually buried.
4. The high temperature and pressure inside the earth slowly converted the buried vegetation into coal.
   1. Carbon, hydrogen, and oxygen are all found in coal. Nitrogen and sulphur are also found in small levels.
   2. When coal or oil is burned, the chemical energy held is released.
   3. This energy is utilized to heat water in order to make steam, which is used to power the turbines.

Option B: CNG

1. Natural gas, a fossil fuel, is found with petroleum. It mainly contains methane.
2. In the compressed form, it is called compressed natural gas or CNG. It is now being used as non-polluting fuel for vehicles.
3. It is a non-renewable source of energy.
   

Option C: Petroleum

1. Petroleum gas is obtained as a by-product during the fractional distillation of petroleum. It mainly consists of butane.
2. Butane can be easily liquefied under high pressure.
3. It is supplied in liquid form in cylinders for domestic use. Cooking gas cylinders used in our homes contain liquefied petroleum gas (LPG).
4. It is also a non-renewable source of energy.

Thus, solar energy is a renewable source of energy and all others are non-renewable.

Hence, option (D) is correct.