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OptimalConcept143 t1_iwpo0v5 wrote

Reply to comment by real_grown_ass_man in Overhyping hydrogen as a fuel risks endangering net-zero goals by filosoful

Not true. The energy density of liquid hydrogen ranges from 4.5 MJ/L for low pressure hydrogen gas to 10 MJ/L for high pressure liquid hydrogen. Lithium Ion comes in around 0.93-2.63 MJ/L. You can see that on the Wikipedia article linked in the previous comment.

For vehicles such as airliners there simply isn't another alternative fuel that can replace kerosene, it will be hydrogen.

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real_grown_ass_man t1_iwps4p1 wrote

The article you quote has 10 MJ/L as HHV for liquid hydrogen. This is at 20k and 1bar. You will need to account for the cooling device to give a realistic number for volumetric energy density.

4,5 MJ is at 690 bara, which i am confident to classify as very high pressure. Lower pressures are also used, and i’d say that this is in the same ballpark as batteries (in volume). This all follows from your article.

I’d say hydrogen fuelled aircraft are a one of the niches where the high volume and safety measures might prove practical, although hydrogen might also be used to form CH4 or longer C chains from CO2 and turned into a traditional but green fuel.

For home heating or transportation I don’t think hydrogen is very practical. But who knows. I hope i am proven wrong.

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OptimalConcept143 t1_iwptosi wrote

If we had the ability to create cheap hydrogen you'd probably have enough electricity to just heat homes that way. Especially when systems like heat pumps can get well over 100% efficiency.

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RSomnambulist t1_iwpw3vu wrote

This also isn't taking into account battery advances like solid state. Amptricity is preselling home batteries now.

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OptimalConcept143 t1_iwpxljn wrote

Batteries can't chemically be as energy dense as hydrogen or fossil fuels. They will improve, but not significantly.

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jeffreynya t1_iwpxo6h wrote

the cost!! holy Crap!

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RSomnambulist t1_iwpy3do wrote

Yeah. They look to be about 2x-3x as expensive as just an LI battery, but there are insurance savings to take into account and the fact that they are significantly safer and more efficient and should last about 10-20y longer. I think the cost is worth it, but they're also the first people on the scene. I expect competition to make them close to LI cost.

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sawlaw t1_iwq54tt wrote

I try not to get too hyped for things just because there are a few pre sales. Once production begins in Ernest and there are a few thousand happy customers I think I'd be ready to make the move, until then it's something for people with money to burn and gamble.

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RSomnambulist t1_iwq6lcf wrote

I'm not spending my money on it, but I'd say that based on preproduction and existing samples and manufacturing that is online already--solid state is further along than HCV mainly because there is so few HCV infrastructure.

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