site banner

Small-Scale Question Sunday for October 9, 2022

Do you have a dumb question that you're kind of embarrassed to ask in the main thread? Is there something you're just not sure about?

This is your opportunity to ask questions. No question too simple or too silly.

Culture war topics are accepted, and proposals for a better intro post are appreciated.

7
Jump in the discussion.

No email address required.

Any thoughts on hydrogen powered cars? EU and German car industry seem to be quite serious about pivoting to it in the future. Which makes me doubt it has any real future. But difficult to find honest arguments for or against.

I am far from an expert on cars. However, my general impression is that hydrogen powered cars overcome many of the individual downsides of EVs--at the cost of reinstantiating many of the broader downsides of fossil fuel vehicles.

For example, you can fully "charge" a hydrogen car in 5 minutes, and its range will be close to that of many fossil fuel vehicles. Even with a "fast" charge, an EV is going to take 15+ minutes to get 200 miles of range, and more often you'll be charging it overnight (and never taking it on road trips). If you have the ill fortune to get caught in a blizzard, a hydrogen vehicle will be much safer than an EV, both in terms of staying functional and keeping you warm. But the technology is costly, charging stations are uncommon, and every new advance in battery technology brings EVs closer to parity with hydrogen performance.

The big picture, though, is that the charging infrastructure overhead for hydrogen (producing, transporting, and storing it) is basically the same as fossil fuels, minus the more complicated stuff that happens in refineries. Most current methods of hydrogen production are energy-intensive and carbon-positive. At best, you get the same problem as with EVs charging off coal; at worst, you're essentially selling EVs with an even higher carbon footprint (and increased thermodynamic waste along the way).

So, basically, in an alternate universe where we already built out a bunch of hydrogen charging stations and brought the cost of production on hydrogen fuel cells down through mass production, people might be wondering why anyone would want a slow-charging, short range EV! But I suppose it's possible the EU intends to subsidize that world into existence, and is counting on fusion or renewables to make electrolysis a more economical approach to hydrogen production. There are definitely possible futures where hydrogen cars are far better than EVs, but I'm skeptical that we'll bring any such future to pass.

It should be feasible to directly produce hydrogen with reactors soon, but the stuff is such an everloving bitch to store and use that even rockets are moving away from it, despite its incredibly high specific impulse. The idea of hydrogen tanks at gas stations just seems ridiculous.

I think any realistic use of hydrogen will involve turning it into synthetic natural gas (or ammonia). Although short term storage of nuclear-produced hydrogen for daily peaking power would be amazing.

I understand hydrogen is more difficult to store than regular gas but is it difficult enough that it's ridiculous to store at gas stations? FWIW, there are already some gas stations with hydrogen in Europe Here's a map and I know there are some hydrogen buses being used as well in public transportation. Maybe it will turn out to be too impractical or to expensive to scale it up to the point where everybody rides hydrogen cars or something. I don't know enough about it to tell you how successful these initiatives have been so far, but there are some serious initiatives which currently implement hydrogen as fuel for motor vehicles, both public transport and for private use.

It requires either extremely high pressures or extremely low temperatures to store an appreciable amount of energy per volume. That's why rockets use super-cryogenic liquid hydrogen and vehicles use expensive COPV vessels capable of containing thousands of PSI. These problems in themselves are not deal-breakers, but the other hydrogen fuel cells needed to utilize it effectively have stubbornly refused to come down in price, namely I think due to the inability to find a suitable replacement for the platinum catalyst.