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Cheap, green hydrogen would be a breakthrough in clean energy

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Re: Cheap, green hydrogen would be a breakthrough in clean energy

#121

Post by ncmncm »

katmannthree wrote: post #108
ncmncm wrote: post #99

Earlier quoted context omitted.

Hydrogen embrittlement is always hyped to the sky. It is not a serious problem unless you are trying to keep warm, gaseous hydrogen under high pressure. So, don't. Furthermore, aluminum is quite resistant to embrittlement. Of possibly greater moment is that it leaks, and has ~200x GHG over CO2 (including secondary effects). Leaks are not dangerous in the open, or in confined places with positive airflow, but punishme…

> trying to keep warm, gaseous hydrogen under high pressure Which of course nobody would do? Unfortunately, those are the circumstances in which H2 is made from fossil fuels and likewise the circumstances under which it is combusted in turbines. You can't just handwave materials compatibility away.

Keyword is "keep". Hydrogen will not be penetrating and weakening turbine blades.

Re: Cheap, green hydrogen would be a breakthrough in clean energy

#123

Post by ClumsyPilot »

causi wrote: post #18

It's too late for hydrogen. For hydrogen to be green is has to either A) be more green than storing the generating power in batteries and using it from there or B) be created with something other than electricity. It's too late for A, batteries are already too good. As for B), feel free to come up with some kind of metamaterial that can produce hydrogen mechanically and in doing so bypass the efficiency loss of elect…

You are missing storage capacity - you could install a cheap storage tank and store enough hydrogen to last months. With batteries thats impossible - if you did it fir a house, it would cost 10x more than the house.

Re: Cheap, green hydrogen would be a breakthrough in clean energy

#124

Post by avmich »

ClumsyPilot wrote: post #116
Barraketh wrote: post #52

Ammonia has been mentioned a few times in this thread, but I will expand a bit, because I believe it is the most promising hydrogen-based approach. Essentially, the idea is to use ammonia directly as fuel. There is an ARPA-E funded project (that I'm currently failing to find) that cracks ammonia into hydrogen and nitrogen using heat. They claim that they can create a mixture of H2 and ammonia that will burn at any re…

From what I read, the efficiency of ammonia production is like 16%, which is well below hydrogen at like 40% or whatever. Even with cheap renewables that is terrible amount of losses even before you get to use the fuel.

Let me quote Clark, from Ignition! https://library.sciencemadness.org/library/books/ignition.pd...

> the nature of the chemical industry being what it was, and is, one could be confident that it would come down to a reasonable figure when anybody wanted it in quantity.

Re: Cheap, green hydrogen would be a breakthrough in clean energy

#125

Post by photochemsyn »

Using hydrogen made from electrolysis of water (using solar/wind inputs) as a fuel for electricity generation is basically a futile cycle, and the only advantage would be temporal storage. For short term storage (hours/days) batteries are far more efficient. For long term storage, hydrogen is a bad idea other than as feedstock for production of longer-chain hydrocarbons (Fischer-Tropsch synthesis) or methane (Sabatier reaction).

The more obvious immediate use (not mentioned in article) is for steel production by the H2-DRI-EAF method, the direct reduction of iron in an electric arc furnace.

https://bellona.org/news/industrial-pollution/2021-05-hydrog...

> "Iron ore is reduced with hydrogen while in a solid state, hence the name direct reduction, to produce direct reduced iron (DRI) called sponge iron. Sponge iron is then fed into an EAF, where electrodes generate a current to melt the sponge iron to produce steel. Some carbon is needed so that steel can be produced. This carbon can come from pulverized coal, biomethane or other biogenic carbon sources."

The other obvious use is as a replacement for natural gas feedstocks for ammonia production via the Haber-Bosch process, and there are similar uses in traditional petrochemical production where hydrogen is often used in various large-scale organic chemistry transformations with names like 'hydrocracking' (breaking apart long-chain molecules) and 'dearomatization' (converting benzene to cyclic hydrocarbons), see:

https://www.linde-gas.com/en/processes/petrochemical-process...

Direct air capture of carbon dioxide and conversion to methane via addition of hydrogen (Sabatier process) as a means of making rocket fuel for Starship, that's also an idea Musk should take up. That's how you'd have to fuel a spaceship on Mars as well.

Re: Cheap, green hydrogen would be a breakthrough in clean energy

#127

Post by katmannthree »

ncmncm wrote: post #121
katmannthree wrote: post #108

Earlier quoted context omitted.

> trying to keep warm, gaseous hydrogen under high pressure Which of course nobody would do? Unfortunately, those are the circumstances in which H2 is made from fossil fuels and likewise the circumstances under which it is combusted in turbines. You can't just handwave materials compatibility away.

Keyword is "keep". Hydrogen will not be penetrating and weakening turbine blades.

The turbine blades are downstream of the combustion chamber so they handle combustion products not hydrogen-rich gas. The turbine combustion chambers, fuel handling system, and high pressure H2 compressors[0] _do_ have to function in a high pressure high temperature H2-rich environment.

0: Take a guess as to what those look like inside.

Re: Cheap, green hydrogen would be a breakthrough in clean energy

#128

Post by oh_sigh »

cagenut wrote: post #66
oh_sigh wrote: post #51

Earlier quoted context omitted.

Right, but the problem is really with hydrogen handling, and all the complexities that would be pushed onto, say, every vehicle. Keeping a hydrocarbon in a container is much, much easier than keeping a single hydrogen atom in a container.

once again we are not talking about cars

Who isn't? I'm talking about cars(among other things). I know the article discounts cars as being solved by lithium ion batteries, but there is still a huge group pushing for hydrogen vehicles.

Re: Cheap, green hydrogen would be a breakthrough in clean energy

#130

Post by mytwocentsworth »

The second paragraph of TFA passingly mentions liquid fuels, then fails to elaborate. A blockbuster point is thereby deprived of appropriate emphasis.

According to Wikipedia[1], "Electrofuels, also known as e-fuels or synthetic fuels, are a type of drop-in replacement fuel. They are manufactured using captured carbon dioxide or carbon monoxide, together with hydrogen obtained from sustainable electricity sources such as wind, solar and nuclear power."

I'm not against other approaches (such as vehicles using compressed hydrogen and fuel cells), but the implications of a drop-in replacement fuel are surely immense. As a short-term solution, synthetic fuels would allow us a slower and gentler transition away from our existing fleet of cars and trucks... and, where aircraft are concerned, e-fuels may even be a solid solution for the long term.

I'm sure there are challenges involved, so please no complaints that I'm expecting a miracle. But it disappoints me that so many discussions about hydrogen revolve around the same old topics... stuff like the energy losses associated with electrolysis, or the embrittlement of tanks used to store compressed hydrogen. With due respect, these are valid subjects... but it seems to me that HN readers (and Mr Gates) ought to find synthetic fuels a subject worthy of a great deal more ink. Darn! -- am I the only one who thinks this is exciting??

[1]https://en.wikipedia.org/wiki/Electrofuel

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