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A hydrogen-powered air taxi flew 523 miles emitting only water vapor
(www.popsci.com)
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this post was submitted on 15 Jul 2024
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It's always important to remember that hydrogen is not harmless.
First, it normally comes from natural gas since it's less energy-intensive to produce it that way.
Second, even if we were to produce hydrogen from water, the cycle of electrolyzing, transporting and using hydrogen is associated with enormous energy losses, and we still have to get that extra energy from somewhere.
Third, even if renewables will fully cover the demands of such production, they are not completely harmless, either. They need to be manufactured and then discarded; they require intermittent energy storage, which either relies on batteries which are not eco-friendly, or again something like hydrogen which would necessitate a much more powerful source and commonly requires rare metals. Also, even in use, solar farms and windmills affect local ecosystems by the construction process, shadows, and, in case of windmills, noise pollution.
That's not to say renewables are bad - they are the best we've got - but any extra energy always comes at a cost, both financially and environmentally.
An air taxi is normally not a wise use of said energy.
Is it worse than hauling enormous batteries, though? I know hydrogen looses like half the energy on generation, but to me it sounds the same as if we do all-electric and spend the same amount of energy for just moving the batteries around. I'm too cooked atm, but is anyone up to do the research/math on this?
Batteries take up about 15-20% of the vehicle mass and have around 90% efficiency
Hydrogen cycle has, at best, 60% efficiency (assuming amazing logistics and fuel cell for hydrogen-to-energy conversion); also, hydrogen systems also weigh a lot, but even if they would weigh literally 0kg, they would lose on efficiency anyway.
Regarding transportation and storage, have a look into "LOHC", there's a lot of promising tech that is already beginning to solve these problems.
Will check out, thanks!
What are the advantages over compressed hydro on one side and metal hydride storage on the other?
Also, if I understand right, that does not address the issues of conversion efficiency.
So as far as I know, the benefit of LOHC is that compression/cooling is no longer required. Transporting/storing hydrogen becomes as easy as transporting any oil. There is an energy cost in the binding reaction, which is endothermic, but the unbinding reaction is exothermic so you get some of that energy back.
Unless you mean some other conversion?
I mean obtaining and using. You have energy losses converting water to hydrogen and hydrogen to energy, and those two compound nastily, even while using the most efficient tech.
Also, safety is a concern that can be addressed, but that was beyond my point. You still need to transfer hydrogen from point A to point B, and it is way more expensive and eco-unfriendly than moving electricity around. Or, if you want to put electrolyzers on each petrol station, you need to make sure the water supply is adequate and hydrogen storage is large enough to supply for peak demand, and that your station gets enough electricity, too (and you'll need more of it compared to a regular charging station).
There's always a lot of hatred for hydrogen in these threads but I'm yet to see a strong argument against it.
Hydrogen is not the solution to climate change in the same way nuclear energy is not the solution - it's probably an appropriate part of the picture in some instances. A lot of large, sophisticated companies and governments are heavily invested in hydrogen.
No one is talking about using hydrogen produced from fossil fuel extraction.
Yes cracking hydrogen from sea water is not efficient, but in places with an abundance of sun and wind but no population hydrogen might be a good way to store and transport energy.
I don't really understand your reasoning here. Yes producing energy requires resources. Using wind and solar to crack hydrogen from sea water does not require batteries nor "a much more powerful source". In the right environment (arid areas) it's easy enough to mitigate the impact on the environment.
1.That's where it normally comes from in the industry. I later made an assumption that this will maybe change 2-3.My point was, all energy has a cost, including environmental one. Even if you put it in an uninhabitable area, you still have to manufacture components and install the plant in a remote area (which is expensive and requires ton of landscape engineering and logistics with a very real and large footprint), and then transport hydrogen to the destination.
That's where it comes from presently because we haven't started producing significant amounts of green hydrogen yet. "This tech is useless because we aren't doing it yet!"
Constructing large solar and wind arrays in remote / uninhabitable areas is not free, but the land is "free" because in many cases it's not suitable for any other use. I think a lot of people dreaming of a wind & solar renewable future underestimate the physical area required to capture enough sunlight to power everyone's EVs.
Scaling mostly reduces economic costs, not environmental ones (latter primarily through better logistics).
Exactly! And we'll need even more if we want to use hydro. That's my point, besides the fact that building cars is extremely wasteful to begin with.