CG: n
CT: Hydrogen is currently considered as the fuel with the highest energy per mass, although its contribution to sustainable energy transition depends on the energy source used for its production. The energy transmitted through hydrogen’s molecular form (H2) is usually classified accompanying the word with a colour representing the contamination level of the energy generation source involved in its separation and the alternative hydrogen division methods. This includes grey hydrogen, obtained from natural gas or other fossil sources such as oil and coal (although the latter is sometimes referred to as black hydrogen or brown hydrogen, depending on the colour of the carbon used as an energy source); blue hydrogen, if obtained in the same way as grey hydrogen, but capturing the carbon emitted during the hydrogen separation process; pink hydrogen (also known as purple hydrogen), from nuclear energy and through electrolysis; turquoise hydrogen, from natural gas, through the pyrolysis process (without CO2 emission); and green hydrogen, obtained by electrolysis and from renewable sources, such as solar, wind, sustainable hydroelectric energy, geothermal energy, and wave energy, among others. Moreover, hydrogen can be obtained from biogenic sources (related to biomass) by fermentation, gasification, reforming, pyrolysis, and bio-photolysis.
S: SDir – https://www.sciencedirect.com/science/article/pii/S2214629623002062 (last access: 22 January 2024)
N: 1. – hydrogen (n): colorless, gaseous element, 1791, hydrogene, from French hydrogène (Modern Latin hydrogenium), coined 1787 by G. de Morveau, Lavoisier, Berthollet, and Fourcroy from Greek hydr-, stem of hydor “water” (from suffixed form of PIE root *wed- (1) “water; wet”) + French -gène “producing” (see -gen).
So called because it forms water when exposed to oxygen. Nativized in Russian as vodorod; in German, it is wasserstoff, “water-stuff.” An earlier name for it in English was Cavendish’s inflammable air (1767). Hydrogen bomb first recorded 1947; shortened form H-bomb is from 1950.
– grey (adj): see gray. “of a color between white and black; having little or no color or luminosity,” Old English græg “gray” (Mercian grei), from Proto-Germanic *grewa– “gray” (source also of Old Norse grar, Old Frisian gre, Middle Dutch gra, Dutch graw, Old High German grao, German grau), with no certain connections outside Germanic. French gris, Spanish gris, Italian grigio, Medieval Latin griseus are Germanic loan-words. The spelling distinction between British grey and U.S. gray developed 20c. Expression the gray mare is the better horse in reference to households ruled by wives is recorded from 1540s.
2. Grey hydrogen is produced from fossil fuel and commonly uses steam methane reforming (SMR) method. During this process, CO2 is produced and eventually released to the atmosphere.
3. Currently, this is the most common form of hydrogen production. Grey hydrogen is created from natural gas, or methane, using steam methane reformation but without capturing the greenhouse gases made in the process.
4. The hydrogen rainbow:
Gray hydrogen: Made from fossil fuels, which release carbon dioxide and add to global warming.
Blue hydrogen: Same as gray hydrogen, but the carbon is captured and sequestered.
Green hydrogen: Made without carbon emissions by using renewable electricity to split water.
Gold hydrogen: Tapped from natural subsurface accumulations.
Orange hydrogen: Stimulated by pumping water into deep source rocks.
5. Grey hydrogen has the highest number of connected economies of the top 10, followed by biomass hydrogen. The connection between the United States and the Netherlands is the highest in grey hydrogen, biomass hydrogen and turquoise hydrogen.
6. Grey hydrogen accounts for roughly 95% of the hydrogen produced in the world today. The two main production methods are steam methane reforming and coal gasification. Both of these processes release carbon dioxide (CO2). If the carbon dioxide is released into the atmosphere, then the hydrogen produced is referred to as grey hydrogen. Grey hydrogen is not considered a low-carbon fuel.
S: 1. OED – https://www.etymonline.com/search?q=grey+hydrogen, https://www.etymonline.com/word/gray (last access: 22 January 2024). 2. HE – https://hydrogeneurope.eu/in-a-nutshell/ (last access: 22 January 2024). 3. TERMIUM PLUS – https://www.btb.termiumplus.gc.ca/tpv2alpha/alpha-eng.html?lang=eng&i=1&srchtxt=HIDROGENO+GRIS&index=alt&codom2nd_wet=1#resultrecs (last access: 18 January 2024). 4. Science – https://www.science.org/content/article/hidden-hydrogen-earth-may-hold-vast-stores-renewable-carbon-free-fuel (last access: 18 January 2024). 5. SDir – https://www.sciencedirect.com/science/article/pii/S2214629623002062 (last access: 22 January 2024). 6. EnEd – https://energyeducation.ca/encyclopedia/Types_of_hydrogen_fuel (last access: 18 January 2024).
OV: gray hydrogen (US)
S: JDP – https://www.jdpower.com/cars/shopping-guides/whats-the-difference-between-gray-blue-and-green-hydrogen (last access: 22 January 2024); GDT – https://vitrinelinguistique.oqlf.gouv.qc.ca/fiche-gdt/fiche/26561149/hydrogene-gris (last access: 22 January 2024); TERMIUM PLUS – https://www.btb.termiumplus.gc.ca/tpv2alpha/alpha-eng.html?lang=eng&i=1&srchtxt=grey+hydrogen&index=alt&codom2nd_wet=1#resultrecs (last access: 22 January 2024).
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CR: blue hydrogen, gasification, green hydrogen, green water, hydrogen, hydrogen refuelling station, sodium.
