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HodorFirstOfHisHodor t1_ix5hyv3 wrote

Reply to comment by drsnafu in Egypt inked deals on renewable energy, green hydrogen worth $119 bln by Wagamaga

Hydrogen can be grey, blue or green. The article says the electricity comes from renewable sources which makes it green hydrogen.

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The_Countess t1_ix64cm9 wrote

or red, which is a 'new' flavour they are developing in japan where its generated by heat from a nuclear reactor.

(A reactor that can't melt down because among other things, it doesn't use water for cooling, and can withstand temps up to 1800 degrees C. They have a test reactor up already, and they let it melt down deliberately, and nothing happened. The reaction stopped on its own.)

So far that's one of the few climate neutral large scale hydrogen generation techniques that has looked at all feasible to me. For everything else the efficiency just isn't there. For example if you use renewable electricity to create hydrogen to fuel a car (even a fuelcell powered one (60% efficiency), not ICE (25% at best), a battery car would go 2.5 to 3 times as far on the same amount of renewable energy.

efficiencies like that would always relegate it specific parts of the market were batteries are just too heavy (aviation) or near instant refueling is a requirement.

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Exotria t1_ix7r07l wrote

There's some interesting work being done with green hydrogen in ammonia production, which is used to make fertilizer. With recent innovations, ammonia production plants can be scaled at smaller sizes, so you've got the use case of an island with lots of solar being able to produce its own fertilizer without fossil fuel shipments.

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HertogJan1 t1_ix83tzo wrote

wouldn't it just be blue like regular nuclear power?

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The_Countess t1_ix8c7ut wrote

They went with red, because its the heat that separates the oxygen from the hydrogen.

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netz_pirat t1_ix8cubp wrote

Green hydrogen only makes sense if you scale your generation for winter needs, and therefore have excess in summer that you can't use otherwise.

And it only makes sense for stuff that you can't power otherwise. (ie efuel kerosene for aviation)

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einmaldrin_alleshin t1_ix8glyp wrote

Well with renewables, there's a lot of fluctuation all the time. If solar and wind are able to power the entire country on a calm and cloudy day, there's going to a lot of excess during windy sunny days. Green hydrogen generation would ideally utilize these peaks.

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