1. Coal is a type of fossil fuel where trapped solar energy in dead and decaying plant matter has been compressed over a period of time to give its current form. It is burned to provide the necessary energy which is converted further into thermal power, fuel and various other raw materials for industries.

2. ‘Oil’ or petroleum is a naturally occurring inflammable liquid that is primarily composed of hydro-carbons. It has high economic importance as it is used for transportation, generation of electricity, power industries etc.

3. Hydroelectricity is the electricity generated from hydropower which is the power generated by utilizing the energy potential of running water.

The following table will provide a comparative study of all three energy sources –

From the above table, we can observe that the advantages of hydroelectricity far outweigh the disadvantages of the same in comparison to coal and petroleum energy resources. With technological advances, it is possible that hydroelectricity will one day replace the more conventional power sources of coal and petroleum.