Explanation:

Conventional energy source

• Conventional energy sources are natural energy resources that are present in a limited quantity and are being used for a long time.
• They are formed from decaying matter over hundreds of millions of years.
• These resources have been depleted to a great extent due to their continuous exploitation.
• If once they are depleted, we have to find a substitute for it as they cannot be renewed, and hence they are called as non - renewable energy sources. Currently, they are being used up more quickly than they can replace themselves.
• Examples of conventional sources of energy include coal, petroleum, biomass, natural gas, and electricity.

Non-Conventional energy source

• Non-conventional sources of energy are the energy sources that are renewable by natural processes.
• These cannot be exhausted easily, can be generated constantly so can be used again and again.
• These sources do not pollute the environment and do not require heavy expenditure. 
• They are called renewable resources as they can be replaced through natural processes at a rate equal to or greater than the rate at which they are consumed.

• The various non-conventional energy sources in which technological developments are under process to harness energy for power generation.
  • Solar energy
  • Wind energy
  • Energy from biomass and biogas
  • Tidal energy
  • Hydrogen energy
  • Ocean thermal energy
  • Geothermal energy
  • Fuell cells

Hence, Coal will be the odd one out since the rest all are non-conventional energy sources.