Mobile and stationary hydrogen applications in the energy transition

Although dihydrogen gas has been known since the 16th century, its use on an industrial scale only really took off in the 19th century. The first applications quickly evolved from the beginnings of aeronautics (inflating aerostats) to the exploitation of its calorific value, first as a lighting gas, then as a fuel for gas engines. It was then used as a chemical reagent for various syntheses (including that of ammonia using the Haber process in 1909), as well as in various petrochemical treatment processes (catalytic reforming, various hydrogenations, hydrodesulfurization, etc.). These processes are still in use today. Dihydrogen has also been chosen as a fuel for aerospace launchers. Its isotopes are the fuel of future nuclear fusion reactors. Today, it is the best candidate for ensuring the energy transition aimed at reducing carbon dioxide emissions into the atmosphere, thus helping to combat global warming. The Paris agreements, signed in 2015 by several countries around the world, force us to make an unprecedented commitment and migrate towards an economy free of greenhouse gas emissions. This first step can be achieved by replacing fossil fuels with green dihydrogen. A second, even more ambitious step would be to move towards a hydrogen civilization in which hydrogen isotopes would become the fuel in their own right via nuclear fusion. In this case, the question of global energy supply would also be answered for many years to come. After a brief review of dihydrogen's properties, the article looks at its current applications. A distinction is made between stationary and mobile applications. Particular emphasis is placed on the stationary energy applications offered by dihydrogen in electrical energy storage processes. Hydrogen is practically non-existent in its natural state. It can therefore only fully fulfill its role as a substitute for fossil fuels if its production is not accompanied by greenhouse gas emissions. The transition from energy carrier to fully-fledged fuel is also discussed here.