OK, you put in electricity and get hydrogen. So where are the efficiency numbers?
Just using an electrolyzer to break up water is about 70% efficient, in terms of energy out / energy in.
critically, the electricity here is not actually directly breaking apart the water into hydrogen, so you can't directly calculate an energy efficiency like you can for electrolysis. this company is using electrohydraulic fracturing to shatter ultramafic rocks and thereby increase the rate of natural geochemical processes like serpentinization or the Schikorr reaction in which rocks react with water to produce geologic hydrogen. the actual source of the free energy that drives the reaction is partially reduced Fe(II) species in the crust (olivine, wüstite, etc) that can absorb an oxygen atom from water to produce free H2 (2 FeO + H2O -> Fe2O3 + H2).
something like 3-6% of the Earth's crust is ferrous Fe(II) so in principle the quantity of hydrogen that could be produced in this manner is something ungodly like 1e15 tons. but the problem is the natural rate of formation is very slow because it's rate-limited by low rock surface areas and slow formation of new rock faces. hence shattering rocks with electricity to increase the reaction rate.
source: I worked on the 2024 us govt research effort that funded these guys
I realize there may not be an ideal oxygen mixture down there but wouldn’t there still be problems with using extreme heat in the presence of hydrogen???
I think there is literally no oxygen down there with the hydrogen. It’s the same with hydraulic fracturing of hydrocarbons. Plenty of methane COULD go boom, but there is no oxygen deep underground.
something like 3-6% of the Earth's crust is ferrous Fe(II) so in principle the quantity of hydrogen that could be produced in this manner is something ungodly like 1e15 tons. but the problem is the natural rate of formation is very slow because it's rate-limited by low rock surface areas and slow formation of new rock faces. hence shattering rocks with electricity to increase the reaction rate.
source: I worked on the 2024 us govt research effort that funded these guys
https://arpa-e.energy.gov/news-and-events/news-and-insights/...