H2 is a secondary energy carrier which can be produced in different ways from fossil and renewable sources. At present, more than 90% of the industrially needed hydrogen is produced from natural gas and heavy oil; furthermore, it occurs as a by-product of the chemical industry, for example from gasoline reforming and ethylene production. A large scale production of hydrogen from biomass does not currently exist.
As a basis for a renewable and sustainable hydrogen economy, it is thus necessary to produce hydrogen from renewable energy sources. In this case, the process known as water electrolysis is given great importance. Various organizations and companies research worldwide on practices and technologies for large industrial applications.