Energy sources are classified as follows:
o Renewable source: They can be regenerated in nature. E.g. Sun, wind, moving water, biomass, etc.
o Non-renewable source: They cannot be regenerated in nature. E.g. Coal, petroleum, natural gas, etc.
Non-renewable resources are Exhaustible.
o Exhaustible sources: They will get depleted after a few hundred years. E.g. Coal, petroleum, etc.
o Inexhaustible resources: They are unlimited and will not exhaust in future. E.g. Biomass, sun etc.