Lubbe et al. Curr. Opin. Green Sustain. Chem. 2023; 39: 100732 | Highlighted on Fuelcons
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. This review article by Lubbe et al. proposes the category “golden hydrogen”, which is produced in such dedicated solar hydrogen generators.
Solar hydrogen generators integrate all the processes required to produce hydrogen from water using solar energy and are typically small-scale, modular, and autonomous. Golden hydrogen is distinct from green hydrogen, as it relies solely on solar energy and cannot be produced by other energy sources. The modular nature of golden hydrogen production units allows for scalability, reducing financial risks and facilitating innovation. These units can be placed close to end-users, creating hydrogen prosumers and increasing the resilience of the energy system. Golden hydrogen can also improve energy system robustness, especially in the face of geopolitical developments.
Source: Lubbe et al. Curr. Opin. Green Sustain. Chem. 2023; 39: 100732
Comment (4 Oct 2023):
Here comes another definition of golden hydrogen:
https://www.alicat.com/knowledge-base/gold-hydrogen/
https://www.goldhydrogen.com.au/
There is obviously no established consensus behind hydrogen color codes.