Hydrogen is the most abundant element in the universe. It is part of every living thing, and without it, life could not exist.
In its pure form, hydrogen is a colorless, tasteless, odorless, non-toxic gas. More commonly,it is found in combination with other elements such as oxygen (in water) or carbon (in fossil fuels such as natural gas). As a result, before it can be used as a pure fuel, hydrogen must be manufactured from water in a process called electrolysis, or extracted from gases such as fossil fuels.
To most people, hydrogen seems like a new fuel. But it has actually been burning for thousands of years as a ‘clean’ component of fossil fuels. The energy in fossil fuels comes primarily from the hydrogen bound up in its chemical structure. Gasoline is a particularly efficient form of fossil fuel because it has a large amount of hydrogen energy bound up in a small volume. Unfortunately, burning gasoline produces a wide range of environmentally dangerous byproducts and contains carbon molecules which create greenhouse gas emissions. Gasoline and other fossil fuels are also non-renewable, leaving us dependent on a limited source of fuel.
The cleanest way to use hydrogen as a fuel is it in its pure form. Energy from hydrogen can be released either through combustion or through a controlled electro-chemical reaction in a fuel cell. However, combustion is not efficient for transportation applications, since much of the energy released is in the form of heat, which is not useful for propelling vehicles.
For transportation, and for many other applications, the best way to release energy from pure hydrogen is through the controlled electro-chemical reaction within a fuel cell. In this reaction, hydrogen and oxygen combine without combustion to form water and release electrical energy. This process produces much less heat than combustion, so more energy is available for useful work.