Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Hydrogen Cools Well, but Safety Is Crucial

power-eng.com

Post reply on HN
Print view View original

31–40 of 46 posts

Re: Hydrogen Cools Well, but Safety Is Crucial

#31

Post by spookie »

bell-cot wrote: post #8
kylec wrote: post #4

Earlier quoted context omitted.

Just wait until you hear about this explosive fuel called "gasoline" that is quite popular for powering cars too

Gasoline is an easily-contained liquid. Gasoline-vapor/air mixtures explode under relatively limited circumstances. Vs. hydrogen is a difficult-to-contain gas, the concentration range for hydrogen/air to be explosive is extremely wide, and triggering the explosion is extremely easy.

While I do not argue the explosive nature of it, safety can be improved by embracing how fast it disperses. Think Toyota went that path with interleaved fibers in their containers' outer enclosures, to augment that effect, so it isn't sufficient for an explosion to occur.

https://www.youtube.com/watch?v=jVeagFmmwA0

(Edit: added Toyota's test where they shot an hydrogen tank, you can see the fibers and the gas dispersion)

Re: Hydrogen Cools Well, but Safety Is Crucial

#32

Post by upofadown »

thsksbd wrote: post #27
flextheruler wrote: post #6

Earlier quoted context omitted.

Right since we haven’t already used an equal or even more so flammable substance for the past century As far as I’m aware gasoline ignites at much lower mixtures of oxygen than hydrogen. The Hindenburg can’t hurt you and if it was filled with gasoline vapors instead of hydrogen, well it would never get of the ground, but it would have been more dangerous.

Hydrogen is significantly more dangerous than gasoline; and gasoline is crazy dangerous as it is. Lower spark energy Broader range of combustibility Faster detonation speed (? [1]) It's only positive is it dissipated quickly, but that's not that great because it goes boom boom at 5% H2 -air. Everyone I know who has worked on combustion problems (I haven't myself, but colleagues have) give H2 a lot of respect. [1] thi…

>Lower spark energy. Broader range of combustibility ...

But not at the same time. That is important because H2 has such a wide ignition range. At the lower end of concentration it isn't much easier to ignite than other things. A readable discussion:

* https://h2tools.org/bestpractices/hydrogen-compared-other-fu...

Re: Hydrogen Cools Well, but Safety Is Crucial

#33

Post by standeven »

MPSimmons wrote: post #16

Hydrogen sucks to work with, from everything I've heard. In addition to the combustion risk when oxygen is introduced, there's the fact that hydrogen molecules are tiny and like to slip through otherwise solid materials, which is annoying if you're trying to fuel a rocket, but it's eventually catastrophic for containment vessels, due to hydrogen embrittlement[1]. As tempting as it is for its benefits, I don't see it…

I've worked with hydrogen (H2) quite a bit recently. Embrittlement and leakage are easy to work around, but here are the pain points I've seen:

1. H2 is still expensive. Most fuel cells require very pure H2 (five nines; 99.999%), or else it can damage the internal membrane. This pure H2 is not very affordable outside of a limited number of fuelling stations.

2. The rules around H2 use and transportation are still fuzzy. Despite being around for so long, regulations are still lacking or unclear.

3. H2 is light weight but takes up a lot of volume, limiting the usefulness of small-scale applications. Compressing it to liquid takes a lot of energy.

4. Fire/explosion risks, as you mentioned.

5. Fuel cells are expensive. If you look at financial statements for most fuel cell companies, they are selling them at a loss, meaning most fuel cells sold today are subsidized by government grants and investors.

6. The oil/gas industry is still pushing "grey" and "blue" hydrogen, which uses natural gas and emits carbon to produce H2.

I think H2 will play an important role, especially in decarbonizing steel making and large transportation applications, but people need to be aware of the limitations and longer timelines required for widespread adoption of green H2.

Re: Hydrogen Cools Well, but Safety Is Crucial

#34

Post by bell-cot »

spookie wrote: post #31
bell-cot wrote: post #8

Earlier quoted context omitted.

Gasoline is an easily-contained liquid. Gasoline-vapor/air mixtures explode under relatively limited circumstances. Vs. hydrogen is a difficult-to-contain gas, the concentration range for hydrogen/air to be explosive is extremely wide, and triggering the explosion is extremely easy.

While I do not argue the explosive nature of it, safety can be improved by embracing how fast it disperses. Think Toyota went that path with interleaved fibers in their containers' outer enclosures, to augment that effect, so it isn't sufficient for an explosion to occur. https://www.youtube.com/watch?v=jVeagFmmwA0 (Edit: added Toyota's test where they shot an hydrogen tank, you can see the fibers and the gas dispers…

True.

But a hydrogen / air mixture is explosive from 4% hydrogen to 74% hydrogen, Americans love their attached garages, and most attached garages feature a perfectly-placed electric spark detonator...er, I mean electric garage door opener...which is triggered daily.

Re: Hydrogen Cools Well, but Safety Is Crucial

#35

Post by njarboe »

Tuna-Fish wrote: post #19
Karellen wrote: post #12

> Kilmartin said one of the questions he asked when he first got into the business was “who came up with this idea? He had to be a madman.” Kilmartin should spend more time around rocket scientists. After hearing a few tales of some of the stuff they've come up with in the name of performance - like a Hydrogen/Lithium/Fluorine(!) tripropellant engine (but you get an Isp of 542s!!!) - using Hydrogen for cooling will s…

Rocket science as a field moved out of exotic energetic fuels by the end of the 90's, because the juice wasn't worth the squeeze, and there is currently an ongoing industry-wide exodus from hydrogen to methane for the same reason. Getting the peak of performance sounds cool when you ignore costs, but in the real world with limited budgets, building a rocket twice as large is easily worth it if it means you never have…

Even more so in the era of re-usable rockets. Cheap fuel and reliability are now the focus.

Re: Hydrogen Cools Well, but Safety Is Crucial

#36

Post by infecto »

spookie wrote: post #29
zdragnar wrote: post #26

Earlier quoted context omitted.

Even if car registration was taxed completely commensurate with their road wear (i.e. weight) the difference wouldn't be enough to move people over from BEV given the lack of refilling options. Gas still has the infrastructure, but batteries are closer to having what they need than hydrogen for critical adoption. Unless you're in the upper Midwest and your car is one of those stuck at a charger unable to fast charge…

> Unless you're in the upper Midwest and your car is one of those stuck at a charger unable to fast charge because it's too cold and you didn't have an hours worth of time and energy to preheat it. You also have the problem where it is "too hot". Higher battery wear and all. Part of me feels the BEV revolution only considered half the northern hemisphere.

Tons of EVs on the roads in Texas. I realize there can be hotter places (Death Valley) or more humid but certainly if you can drive an BEV in the height of Texas summer that should fit more of the worlds use cases.

I think cold is a harder problem to solve, I think your delta T of environment temps and operating temps are much greater in cold weather.

Re: Hydrogen Cools Well, but Safety Is Crucial

#38

Post by foobarian »

phkahler wrote: post #9
flextheruler wrote: post #6

Earlier quoted context omitted.

Right since we haven’t already used an equal or even more so flammable substance for the past century As far as I’m aware gasoline ignites at much lower mixtures of oxygen than hydrogen. The Hindenburg can’t hurt you and if it was filled with gasoline vapors instead of hydrogen, well it would never get of the ground, but it would have been more dangerous.

Nope. Hydrogen is not just flammable, the article tells you it is EXPLOSIVE at concentration of 4 percent to 74 percent in air. If the Hindenburg was a hydrogen-air mixture, it would have leveled a large portion of the area rather than just burning where it fell. I've worked in areas where they were developing hydrogen fuel cell vehicles at major auto makers. The facilities are equipped with collectors, detectors, an…

One time I filled a Mylar balloon with H2 by electrolysis. It floated very nicely but I was too cowardly to keep it in the house. It made a nice fireball when lit outside but no particularly notable explosion.

Encouraged by this I filled one of those grocery store vegetable bags with H2 + O2 from the same electrolysis setup (combine both outputs this time). Stoichiometric mixture! The boom was so loud I thought it was going to break my windows from about 20 feet away.

Re: Hydrogen Cools Well, but Safety Is Crucial

#39

Post by willis936 »

If you want to get really nuts: consider that high temperature superconductors are a good match for hydrogen cryogen coolant. Hight temperature superconductors work with liquid nitrogen, but work best with liquid helium and there just isn't that much helium in the world compared to how much superconducting magnets we could use.

Re: Hydrogen Cools Well, but Safety Is Crucial

#40

Post by ViewTrick1002 »

standeven wrote: post #33
MPSimmons wrote: post #16

Hydrogen sucks to work with, from everything I've heard. In addition to the combustion risk when oxygen is introduced, there's the fact that hydrogen molecules are tiny and like to slip through otherwise solid materials, which is annoying if you're trying to fuel a rocket, but it's eventually catastrophic for containment vessels, due to hydrogen embrittlement[1]. As tempting as it is for its benefits, I don't see it…

I've worked with hydrogen (H2) quite a bit recently. Embrittlement and leakage are easy to work around, but here are the pain points I've seen: 1. H2 is still expensive. Most fuel cells require very pure H2 (five nines; 99.999%), or else it can damage the internal membrane. This pure H2 is not very affordable outside of a limited number of fuelling stations. 2. The rules around H2 use and transportation are still fuz…

I love the hydrogen ladder to visualize this concept. To decarbonize fertilizer hydrogen is unavoidable, for personal transports it has been uncompetitive the past decade.

https://www.linkedin.com/pulse/clean-hydrogen-ladder-v40-mic...

Post reply on HN