Hydrogen is a colourless, odourless and inflammable gas that produces a large amount of energy, while undergoing combustion. It is the lightest gas on Earth.
The calorific value of hydrogen is 141,790 kJ/kg. It is the highest for any fuel.
Hydrogen is the most abundant element in the universe. About 75% of all known matter in the universe is hydrogen. On Earth, hydrogen is found in abundance in combined form.
Today several automobile giants are performing extensive research on how to use hydrogen as a fuel source in automobiles. Some have already succeeded in producing hydrogen powered vehicles.
The Honda FCX Clarity (pictured below) is a 100 kW hydrogen powered fuel cell vehicle introduced by Honda Motor Company, Ltd.
If hydrogen is properly harvested and utilized, it can be used as an alternative energy resource in automobiles.
Production of Hydrogen:
Hydrogen can be produced in many ways. The two main ways of production of hydrogen are:
- Electrolysis of Water
- Steam reforming
1. Electrolysis of Water:
Electrolysis is a process in which direct current is used to drive a non-spontaneous chemical reaction. In electrolysis of water, electricity is passed into water to split water molecules into hydrogen and oxygen molecules. The hydrogen molecules obtained thereby can be used to drive the engine of a vehicle.
2. Steam Reforming:
In steam reforming, methane (or other suitable hydrocarbon) along with steam is passed over a catalyst, in a steam reformer. Hydrogen gas is separated from the steam-hydrocarbon mixture in the chemical reaction, that takes place in the steam reformer. Steam reforming is often used for mass production of hydrogen.
Apart from the above two methods, many other methods like thermal splitting, biological decomposition are used to produce hydrogen.
In hydrogen powered vehicles, hydrogen may be used to directly power internal combustion engines or it may be used in fuel cells.
A fuel cell is a device that produces electricity by combining hydrogen and oxygen in air. In the Honda FCX Clarity (pictured above) hydrogen powered fuel cells are used.
Advantages of using hydrogen as fuel in automobiles:
- Hydrogen has very high calorific value.
- When hydrogen is oxidised, only heat and water are produced. Hence, hydrogen powered vehicles are pollution free.
Disadvantages of using hydrogen as fuel in automobiles:
- Though hydrogen has high calorific value, it has low energy content per unit volume.
- Production, storage and transport of hydrogen is complex and expensive.
- Hydrogen gas is highly inflammable.