Question

What is calorific value of a fuel? Why is hydrogen not used as a fuel though it has the highest calorific value?

Answer 1

The amount of heat liberated, when one kg of a fuel is completely burnt in sufficient supply of oxygen, is called the calorific value of the fuel.

Hydrogen is not used as fuel despite the highest calorific value because:

• It is lighter than air; thus, it is not easily available.
• It cannot be used in liquid form because its melting point is $-$253⁰C.
• Hydrogen gas in external air may spontaneously ignite.
• Hydrogen fire, while being extremely hot, is almost invisible; thus, it can lead to accidental burns.
• Hydrogen poses unique challenges due to its ease of leaking, low-energy ignition and wide range of combustible fuel-air mixtures.