Hydrogen

Hydrogen is the most widespread element in the universe: it is the main constituent of the sun, giant planets like Jupiter and Saturn, most stars and interstellar and intergalactic matter.

On earth, hydrogen is most often combined with other elements to form molecules such as water, hydrocarbons or even more complex molecules such as proteins or carbohydrates. Also, the H ₂ or dihydrogen molecule, although observed, in emissions from certain ridges, exists very little in its natural state. To be used, therefore, the element hydrogen must first be separated from its host molecule to be recombined into dihydrogen molecules, which is generally a very energy-intensive operation. In short, it has to be produced. To date, hydrocarbons are the main source of industrial hydrogen, via mature production processes such as steam reforming, with the disadvantage of co-producing carbon dioxide. Hydrogen plays an important role in the chemical industry, in oil refining and petrochemicals, and to a lesser extent in the production of certain materials. Today, however, its use as an energy carrier is very limited. However, because of its non-polluting combustion, it is also seen as a potential energy carrier of the future, provided that its production itself is non-polluting. The industry's expectations therefore focus first and foremost on clean, economically viable production. Hydrogen storage and distribution are two key points in the use of hydrogen as an energy carrier.

The aim of this article is to describe the entire hydrogen chain. It begins with an overview of the market, then describes existing technologies for hydrogen production and purification, as well as those under development. As the production of hydrogen from hydrocarbons is accompanied by carbon dioxide emissions, CO ₂ capture and storage solutions are discussed. Hydrogen storage, transport and distribution methods are then discussed, as these are the three essential links in the chain between production and use. Finally, this article gives some background on the safety issues associated with the use of this molecule and the standards in force.