Fuel takes many different forms and there are a variety of different processes which we can apply to it to release it's energy. Obvious examples are Petrol, Uranium, Hydrogen or BioFuels.
We can classify Fuels in a number of different ways, Firstly, we can consider the process that we have to apply to release its Energy. The most common method here is Combustion—that is, we burn it—or other form of Oxidative reaction.
There are also a some functional properties of Fuel that we need to consider. These might include
- Density - Safety - Reliability