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OptimalConcept143 t1_iwpgktt wrote

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

Hydrogen is the only fuel source that can replace fossil fuels for basically every use. The only reason it isn't doing so right now is because it requires too much energy to produce. If something like nuclear fusion finally happens, this wouldn't be an issue and it would by far be the most efficient and green fuel source possible, and that's from a physics perspective.

https://en.wikipedia.org/wiki/Energy_density#In_chemical_reactions_(oxidation)

As you can see here, hydrogen has more energy density than any other common fuel source, including fossil fuels. It's not a matter of "if" hydrogen becomes our main fuel source, but "when".

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real_grown_ass_man t1_iwpkaup wrote

Energy density per weight, yes. Energy density per volume is about the same as a lithium ion battery. On top of that, hydrogen is difficult to store at length.

For this reason, hydrogen will remain an energy carrier in very specific niches, where large volumes are no problem and where the necessary safety precautions are acceptable.

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OptimalConcept143 t1_iwpo0v5 wrote

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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UniversalMomentum t1_iwppclc wrote

We can dream, but I'll have to see real world LCOE stats before I start accepting Fusion as a cheap option. Until then it has horrible LCOE because it's all investments and no power output.

Nuclear has such a long history of claiming much cheaper costs than it winds up producing and with such high complexity I have my doubts it willproduce wind/solar level cheap energy.

Same thing happened with fission. On paper it was much cheaper than averaged real life costs. Plus nuclear LCOE doesn't take real long term waste storage or inevitable accidents into account. They are cheating LCOE pretty hard on the nuclear side just like the fossil fuel side and all it's externalized long term costs.

Also the problem of just convincing a country that can't build nuclear reactors to switch a huge chunk of its power generation over to nuclear reactors and then be completely dependent on one or a handful of countries that can maintain those reactors. As well as venting the countries making Fusion reactions to export to developing nations.

On Paper those obstacles might not look huge, but I'm pretty sure they are.

Of fusion can produce a levelized cost of energy around $25 per megawatt hour then it will at least be a good option for the handful of countries that can build the reactors, but I doubt it will scale out globally.

Try to think about it like you're the developing country and America has highly proprietary power plant design that it wants you to invest in and will require you to basically stay in America's favor or not be able to fix your own power plants.

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