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Comment by thow-58d4e8b | Hacker News Reader

> hydrogen being much more efficient than believed

God/Allah/Nature obviously don't understand disruption, growth mindset and can-do-spirit. facepalm

There are hard physical limitations that no amount of human ingenuity can do anything about. 237kJ/mole is the theoretical minimum of energy required for water electrolysis. energy->electrolysis->energy round-trip efficiency won't exceed 45%, even if everything, from the energy source to the car wheel spinning, is perfectly frictionless and operating at peak theoretical efficiency. No, you cannot use existing gas pipelines for transporting hydrogen.

For passenger cars, EVs today are already better than what physics allow hydrogen cars to ever be.

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Except you can extract 237 kJ/mole from hydrogen. A fuel cell is a battery and can approach the efficiency of a lithium-ion battery.

> No, you cannot use existing gas pipelines for transporting hydrogen.

You absolutely can. In fact gas companies are already planning this exact thing.

> For passenger cars, EVs today are already better than what physics allow hydrogen cars to ever be.

Your "physics" is entirely pseudoscience.

I thought too you can but it's only theoretically, not absolutely. See for example: https://youtu.be/vrKvj2MHLVw

It is fully viable: https://www.siemens-energy.com/global/en/news/magazine/2020/...

I prefer opinion of independent expert over that of technology vendor soliciting EU's investment. But even they say "won't be before 2030" anyway.

It will likely be a transition from blended hydrogen before reaching 100% hydrogen later. Just because it won't happen all at once doesn't mean it hasn't already started.

I am not against hydrogen, but seems to me as if nobody in the space is noticing the disruption what electrical batteries already are. If battery trends continue by 2030 the value of refitting infrastructure to hydrogen easily becomes questionable [note], when there's a way to both transport and store energy more efficiently and at the same price if not cheaper. There are no signs of battery improvements to stop anytime soon or price to stop dropping.

[note] for pure hydrogen eventually everything except the pipelines will have to be replaced

I think those people are simply living in the past. It is hydrogen disrupting batteries, not the other away around. In fact, I see a flattening of the pace of battery improvements, meaning the speed of this disruption event should be moving faster than expected. By 2030 the battery "revolution" might have already collapsed and left for obsolescence.

It's important to remember that hydrogen fuel cells are batteries too. There is no reason for the metal lithium to have magic properties over other battery technologies.

Thinking about it, indeed lithium charge/discharge efficiency over 90% is kind of magic :) and not even needing high pressure or cryogenic vessels.

All close cycled cells have the same properties. Ultracaps are even better.

Nope. Both NiMH and lead acid batteries are less efficient in this regard. And supercaps have lower energy density, although they are improving quickly too.

NiMH is around 90% efficient too. Lead-acid around 85%. Also, li-ion don't do well under high discharge rates and can drop to <70%. It's not a perfect cell technology by any means.

Does hydrogen get added back into the fuel cell as the car breaks?

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