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.

Automated summary

Hydrogen is classified and labeled based on the resources and processes used in its production, such as electrolysis, and energy sources, such as solar radiation. Green hydrogen is primarily produced through the electrolysis of water using renewable electricity from wind, geothermal, solar, or hydroelectric power plants. Solar hydrogen generators, which integrate sunlight harvesting and water molecule splitting, are more modular and operate at a smaller scale. The term "golden hydrogen" is proposed to differentiate hydrogen produced by modular solar hydrogen generators. Decentralized modular production of golden hydrogen complements centralized and energy-intensive green hydrogen production. The distinction between green hydrogen and golden hydrogen can help promote the additionality principle in clean hydrogen policies.