Why Only Hydrogen? Hydrogen as a fuel and carrier of energy
Why Only Hydrogen?
Historically, carbon has been the most practical carrier of energy. Fossil fuels are packed with more energy than pure liquid H2 of the same volume. The carbon atoms have classic storage capabilities and releases even more energy when burned with hydrogen. However, burning carbon base fuel (fossil fuels) and releasing its exhaust contributes to global warming due to the greenhouse effect of carbon gases which results in all the current problems related with the environment. Diverse domestic resources can be used for the production of H2 with the potential for near-zero greenhouse gas emissions, adding to the environmental benefits. H2 is an energy carrier that can transform our fossil-fuel dependent economy into a hydrogen economy, which can provide an emissions-free transportation fuel.
Hydrogen as a fuel
It lies in the first group and first period in the periodic table, i.e. it is the first element on the periodic table, making it the lightest element. This gas is so light, it rises in the atmosphere and is therefore rarely found in its pure form, H2. In a flame of pure H2 gas, burning in air, the hydrogen (H2) reacts with oxygen (O2) to form water (H2O) and releases energy.
2H2(g) + O2(g) → 2H2O(g)
(If carried out in atmospheric air instead of pure oxygen (as is usually the case), H2 combustion may yield small amounts of nitrogen oxides, along with the water vapour.)
The energy released enables H2 to act as a fuel. That energy can be used with relatively high efficiency in an electrochemical cell,. Since there is very little free H2 gas, H2 is in practice only an energy carrier, like electricity, not an energy resource. H2 gas always requires more energy for its production than that which can be retrieved from the gas as a fuel later on.
Table 1: Use of Hydrogen as a Transportation Fuel
|High energy yield (122kJ/g)||Low density (large storage volume)|
|Most abundant element||Not found free in nature|
|Produced from many primary energy sources||Low ignition energy (similar to gasoline)|
|Wide flammability range(hydrogen engines can operate on lean mixtures)||Currently expensive|
|Water vapour is a major constituent of emission|