Answer:

ENERGY OBTAINED FROM COMBUSTION AS GOOD SOURCE(THERMAL RADIATION)

For a good source of energy it should have a tendancy to give most of it WITHOUT giving out residue. Such as natural gas(basically methane about 75%) .

It should be more economically feasible, should be found in large quantities,easy to transport. For example charcoal, fossil fuels (but nowadays they limited due to irresposibleness).

It should have high calorific value. It should also obtained on earth in form free state(helps to extract them).It should not produces harmful air pollutants and should not produce more amount of greenhouse gases.

ENERGY OBTAINED FROM NATURALLY OCCURRING INCIDENTS IN NATURE.(BY CONVERTING INTO USEFUL SOURCE OF ENERGY AS A GOOD SOURCE OF ENERGY.

It should be a inexhaustible source of energy.The spot of harnessing should be found in large quantities. It should be technologically possible to harness the energy and economically feasible.

For example Wind, Solar,Geothermal,Tidal, hydro-power dams energy.

ENERGY OBTAINED FROM RADIOACTIVE ELEMENTS OR NUCLEAR ENERGY.

These are obtained from radioactive elements such as URANIUM ,Thorium,Plotonium etc.

They are good source of energy because they are required in little amount but gives out energy in

ENORMOUS amount. They are obtained basically from atomic fission and fusion but COST of providing a system to harness them is extremely expensive.

THINGS THAT COULD REVOLUNISE THIS WHOLE WORLD BUT STILL FAR TO PRONE FROM REALITY.

Such as using energy of thunderbolts, Converting infrared radiation into electricity.