this post was submitted on 13 Nov 2023
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[–] [email protected] 36 points 1 year ago (5 children)

A hydrogen engine is so much worse for efficiency than a hydrogen fuel cell, and even that is not good compared to batteries. I'd estimate the round trip efficiency of a hydrogen engine to be about 10-15%. So for the same energy that could be used to drive a battery EV 100km, this car from Toyota could drive 12km.

Additionally, hydrogen is not very energy dense per volume. A compressed hydrogen tank that replaces the boot/trunk of the car would have enough hydrogen for about 100km of range.

Please let me know if I'm wrong about any of these numbers. For Toyota's sake, I really hope I'm wrong.

[–] [email protected] 14 points 1 year ago* (last edited 1 year ago)

I thought they were using ammonia powered vehicles and calling them hydrogen just because ammonia contains hydrogen. Wasn't there a bunch of hype a few months ago about Toyota inventing an ammonia internal combustion engine that was so efficient it would "make electric cars obsolete"? The article just mentioned liquid hydrogen though. So I don't know what to believe anymore.

[–] [email protected] 3 points 1 year ago (1 children)

I think the biggest thing that people forgot in the efficiency debate is cost. What will hydrogen actually cost to go 100km compared to electricity

[–] [email protected] 3 points 1 year ago* (last edited 1 year ago)

The current cost to drive a car with green hydrogen from electrolysis (not blue or grey hydrogen from methane reforming) is roughly equivalent to $50/L (AUD) for petrol, or $120/Gal (USD) for gas. This is one of the reasons most hydrogen today is made from fossil fuels.

[–] [email protected] 2 points 1 year ago

and you have to use it up within a week or two, or your fuel disappears

[–] wooki 1 points 1 year ago* (last edited 1 year ago) (1 children)

And yet here we are breaking new ground with brand new (within the year) solid hydrogen projects.

The alternative is the slow charging and short life high cost lithium battery. We need better and efficiency matters not when it’s being pulled from the air in huge stand alone stations now being built.

[–] [email protected] 1 points 1 year ago

The alternative is the slow charging and short life high cost lithium battery.

I've seen nothing suggesting a short life. Solid state batteries also should result in short charging times