Golden Hydrogen

Hydrogen is a colorless compound to which symbolic colors are attributed to classify it according to the resources used in production, production processes, such as electrolysis, and energy vectors, such as solar radiation. Green hydrogen is produced mainly by electrolysis of water using renewable electricity from an electricity grid powered by wind, geothermal, solar or hydroelectric power plants. For grid-powered electrolyzers the tendency is to go larger to reach the gigawatt-scale. An evolution in the opposite direction is the integration of the photophysics of sunlight harvesting and the electrochemistry of water molecule splitting in solar hydrogen generator units, with each unit working at kilowatt-scale, or less. Solar hydrogen generators are intrinsically modular, needing multiplication of units to reach gigawatt-scale. To differentiate these two fundamentally different technologies the term ‘golden hydrogen’ is proposed, referring to hydrogen produced by modular solar hydrogen generators. Decentralized modular production of golden hydrogen is complementary to centralized, energy-intensive green hydrogen production. The differentiation between green hydrogen and golden hydrogen will facilitate the introduction of the additionality principle in clean hydrogen policy.