Q. Which of the following is the best fuel in terms of energy released per gram of fuel?
- Hydrogen
- Butane
- Ethanol
- Methane
Answer: Hydrogen
A fuel is any material that can be made to react with other substances so that it releases energy as heat energy or to be used for work.
Chemical fuels are substances that release energy by reacting with substances around them, most notably by the process of combustion. Most of the chemical energy released in combustion was not stored in the chemical bonds of the fuel, but in the weak double bond of molecular oxygen.
The amount of energy from different types of fuel depends on the stoichiometric ratio, the chemically correct air and fuel ratio to ensure complete combustion of fuel, and its specific energy, the energy per unit mass.
Chemical fuels are substances that release energy by reacting with substances around them, most notably by the process of combustion. Most of the chemical energy released in combustion was not stored in the chemical bonds of the fuel, but in the weak double bond of molecular oxygen.
General types of chemical fuels | ||
Primary (natural) | Secondary (artificial) | |
Solid fuels | wood, coal, peat, dung, etc. | coke, charcoal |
Liquid fuels | petroleum | diesel, gasoline, kerosene, LPG, coal tar, naphtha, ethanol |
Gaseous fuels | natural gas | hydrogen, propane, methane, coal gas, water gas, blast furnace gas, coke oven gas, CNG |
Energy capacities of common types of fuel | ||||
Fuel | Specific energy (MJ/kg) | AFR stoich. | FAR stoich. | Energy @ λ=1 (MJ/kg(Air)) |
Hydrogen | 142 | 34.3 : 1 | 0.029 : 1 | 4.140 |
Diesel | 48 | 14.5 : 1 | 0.069 : 1 | 3.310 |
Gasoline | 46.4 | 14.7 : 1 | 0.068 : 1 | 3.156 |
LPG | 46.4 | 17.2 : 1 | 0.058 : 1 | 2.698 |
Kerosene | 46 | 15.6 : 1 | 0.064 : 1 | 2.949 |
Ethanol | 26.4 | 9 : 1 | 0.111 : 1 | 2.933 |
Methanol | 19.7 | 6.47 : 1 | 0.155 : 1 | 3.045 |
Nitromethane | 11.63 | 1.7 : 1 | 0.588 : 1 | 6.841 |
1 MJ ≈ 0.28 kWh ≈ 0.37 HPh.
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