Submitted by Hypx t3_10mdti7 in Futurology
Hypx OP t1_j62l7wj wrote
Reply to comment by Angry_Washing_Bear in Cryo-compressed hydrogen, the best solution for storage and refueling stations? by Hypx
It will likely just vent out quickly. Any fire would be brief. Hydrogen is safer than gasoline in a fire because it does not stay in place very long.
Angry_Washing_Bear t1_j62ltst wrote
That’s the point.
It explodes rather than burn off.
Which makes the consequences much higher even if the risk is the same or lower.
Throughout the entire article not a word was mentioned about consequence and risk in the case of unforeseen failure or accidents. To me this seems deliberate because the consequences are massive.
Hypx OP t1_j62mb9n wrote
An explosion is unlikely. You need a very thorough mix of air and hydrogen for there to be an explosion. It is not likely to happen in a conventional accident.
Angry_Washing_Bear t1_j62pxc4 wrote
With the thousands of accidents happening on roads every year something can and will happen with hydrogen based vehicles whether as fuel, transported or both.
To not even offer a word about risk and consequences in an article seems disingenuous. Even if the risk is low the consequences are major.
What happens if there is a fire in a parking garage and you have multiple hydrogen vehicles now being exposed to extreme heat over a long time?
Instead of burning off you now have a risk of a major explosion causing far more damage than burnout from liquid fuels or batteries.
Why are these concerns always omitted when it comes to articles and discussions surrounding the commercialized use of hydrogen?
Hypx OP t1_j62u350 wrote
Liquid fuels are also pretty explosive. So are li-ion batteries. We are not in any more danger.
BoredCop t1_j63cgpz wrote
Liquid fuels are nowhere near as explosive as compressed hydrogen gas.
For one thing, hydrogen has much wider explosion limits than gasoline so explosions can happen in a wider range of fuel/air mixtures.
The main difference, however, is that liquids are liquid while compressed gasses are compressed gases. By which I mean, if you spill gasoline on the ground it merely forms a very non-explosive puddle and slowly evaporates. It's the mix of vapour and air that is potentially explosive. If you get a hydrogen leak, the pressure makes it rapidly expand and mix with air so you get nearly complete mixing with air almost instantly. A liquid leak just drips down under gravity. A compressed gas leak jets out at high velocity and turbulently mixes with air. Big, big difference in explosion hazard.
Hypx OP t1_j63d0et wrote
Liquid fuels are considered more dangerous because they burn in place. It is not just a "non-explosive puddle." It is a carpet of flames if it ignites. This is a very dangerous situation since it can trap someone in a car during a fire.
A gas, especially one that is much lighter than air, will quickly dissipate. It will have a much lower chance of fire and any fire that does happen will not stay in place. The danger is only during the moments when gas is leaking.
BoredCop t1_j63ejdy wrote
Tell me you've never responded to a fire, without telling me you've never responded to a fire.
I'm a cop, I have seen the immediate aftermath of many fires including ones that involve flammable liquids and gases. And I've been around many a wrecked car with gasoline leaking out. The only times on my watch that we've had real ka-Boom explosive fires involved pressurised gases, such as propane. Conversely, we've had arsonists intentionally starting fires with gasoline only to have the fire self extinguish after using up the available oxygen in a room.
A gas that completely mixes with air in a second or two is much more likely to ignite than a puddle of fuel on the ground. Especially so when the gas in question has a very wide range of ignitable fuel-air mixtures, as is the case for hydrogen.
Sure, the hydrogen fire will "not stay in place". Nice euphemism for "blow up the whole garage".
Hypx OP t1_j63g264 wrote
Hydrogen isn't propane FYI. It is a lighter than air gas. Propane is heavier than air.
BoredCop t1_j63k2ed wrote
I'm fully aware of that. Makes no difference to degree of risk, only to wether it will accumulate along the floor or along the ceiling in a garage or a tunnel.
There are reasons why an old name for hydrogen in some languages is "knallgass" or variants of same, it translates as "bang gas" and refers to its explosive tendencies.
There are reasons for why you're supposed to connect and disconnect the charger or jumper cables in a certain order when dealing with a car that has a flat lead-acid battery, and make the final connection to chassis ground away from the battery. Such batteries can create and leak hydrogen via electrolysis, and explosions are a known hazard. The act of connecting jumper cables can create enough of a spark to set it off, as many people have experienced.
Basically, the explosive hazard of hydrogen gas is well known and has been for over a century. Your claiming otherwise cannot change the facts.
Hypx OP t1_j63kvb5 wrote
And yet it is fact that it is safer than gasoline. This is not actually a debate here. People have set both on fire and gasoline is a lot more dangerous:
BoredCop t1_j63nx60 wrote
That first one is laughable, it is from a biased source and is intentionally rigged to produce the desired result. They present it as if the overpressure relief valve is the only probable leak point, and set it up to immediately ignite before any real volume of gas has time to mix with air. It's like lighting a gas range in a kitchen immediately after opening the valve, and claiming this proves it would be safe to let gas leak out for half an hour and then light a match in the same kitchen. Of course you get no explosion when you carefully make sure the conditions needed for an explosion don't occur, by igniting immediately at the leakage site.
The second one is more interesting. Here, they do in fact allow the gas to mix with air for a few seconds before ignition. However, these tests used liquid hydrogen at a much lower temperature than the gaseous phase cold compressed hydrogen we are discussing here. Liquid hydrogen is seriously cold, and only boils off to gas phase at a slow rate depending on how much heat energy it can absorb from the surroundings. In that sense liquid hydrogen it is rather similar to liquid gasoline; it's the gas that burns not the liquid. You'll note none of the spill experiments in that video involved pressure vessels rupturing or pressurised fuel lines breaking, it was all liquid hydrogen at atmospheric pressure. That makes a huge difference in how rapidly it mixes with air. The very low temperature also slows down the reaction when it is ignited, compared to igniting gas that's a hundred degrees warmer.
DonQuixBalls t1_j62xibj wrote
Bro. It's a no.
TheAnonFeels t1_j63xoe5 wrote
Sure, hydrogen can dissipate quickly..
It can also ignite faster. Fill the area around or in a car in under a second, it wont dissipate fast enough.. You could argue it would dissipate oxygen too, but it'll already get mixed with the air before that happens. All it takes is a ignition point before the gas can dissipate, and there would be no fire, because there would be no car left.
Hypx OP t1_j65ckam wrote
It's lighter than air. It won't stay very long. And no, that's not how a hydrogen flame would work.
TheAnonFeels t1_j65kgay wrote
Video 1: That's like one i commented earlier, where it burns straight up from under the driver seat, thanks for the laugh again.
Anyway, video 1: That's only if it's ignited as it vents, they didn't give the gas time to vent without a flame cause...explosion.
Video 2: Most of these are Liquid hydrogen which acts much more safe than gaseous hydrogen as countless people have pointed out.
If you can, point me to a segment that is gaseous hydrogen.
For clarity, yet again, liquid hydrogen stays liquid until i can get enough heat to vaporize. Also, because of that, it doesn't mix with air well.
We don't drive hydrogen cars with liquid hydrogen, its difficult to work with, being cryo.
Brings me to the part of Video 2 where they show what happens when hydrogen mixes with air: https://youtu.be/7bFJK5kU_UQ?t=443
TheAnonFeels t1_j65m1qt wrote
Here's a balloon full of hydrogen in a cardboard box, gaseous.
Hypx OP t1_j65mak5 wrote
It most likely won’t ignite at all even when vented. There needs to be an ignition source. In most cases, the hydrogen just dissipates completely.
You’re simply ignoring the other side of the video: What happens when a gasoline cars catches on fire. That is significantly more dangerous. And we already accept that danger. It’s pointless to fearmonger about something less dangerous.
TheAnonFeels t1_j65o4cp wrote
I'm not fear mongering but you're ignoring the other side too... I'm ignoring the gasoline cars because we're all accustomed to it.
What do you mean most likely wont ignite?????? Hydrogen is the single most dangerous gaseous atom we have.
Ignition source? crashes are full of them, what about the gasoline fire from the car that hit you? Or the time you open kick your door open and it scrapes the pavement making a spark? roads, garages, and crashes are full of ignition sources..
I just see us having a car sitting in a garage overnight, and a switch turns on, or a natural gas furnace kicks on and the building is gone.
I'm all for the attempt at hydrogen vehicles, but i don't see it as a fix all. I wouldn't drive one, hell i dislike my gasoline powered car. But you gotta accept that hydrogen can ignite after mixing. That balloon video ignited after mixing, how do you think a ruptured tank is going to look?
Hypx OP t1_j65ovnu wrote
You still need an ignition source for a fire. Not to mention how fast it leaves the vehicle. It also doesn’t explode. You are basically ignoring the videos and substituting your own imagination here.
A balloon isn’t a fuel tank. It is already premixed with air. Even sugar will explode in the right setting.
Again, it is safer than gasoline. This is not a debate anymore. The evidence already made this clear.
TheAnonFeels t1_j65q39q wrote
Did you not read my responses to those videos? about how they're all LIQUID hydrogen? Which is completely different...
We have 15k hydrogen vehicles on the road, yes. And their tanks can withstand the harshest impacts. I get this. I get their safer, but the catastrophic failures of gasoline vs hydrogen are completely different. And these will happen. Hydrogen is the leakiest material we have, and ever will have.
My only point through ALL of this, has been about how you keep talking about liquid nitrogen and don't understand the difference.
It doesn't explode?!
Hydrogen can explode.
Wanted to drop some stats before you stopped listening, but here they are anyway.
Gasoline flamability limits in sea level atmosphere: 1.4%-7.6% (cannot ignite outside that)
Hydrogen: 4%-75%
Detonability of hydrogen in air are 18.3% to 59% by volume.
Hypx OP t1_j65qi2x wrote
Again, you need an ignition source. And for an explosion you need a proper fuel mix. In reality, it will just float away immediately in most cases. A fire would hardly be dangerous compared to what a gasoline fire looks like. You're entirely ignoring actual data.
Like I said, you are just fearmongering. You already are in more danger driving a regular car.
TheAnonFeels t1_j65r41w wrote
dude, really.. Stop for a second.. A proper fuel mix?
Detonability of hydrogen in air are 18.3% to 59% by volume. There's the fuel mix for an detonation. Explosion is 4% to 75% ...
You're ignoring my entire comment.
Hypx OP t1_j65re8i wrote
And it's all just bullshit. Hydrogen is lighter than air. It doesn't have time to stay mixed. It's literally what they showed in the video.
Like I said, you are substituting reality with your own imagination here.
TheAnonFeels t1_j65s3op wrote
I've said multiple times that's liquid hydrogen.
My own imagination here is that i can convince you my only point here was telling you hydrogen COULD ignite...
Not saying hydrogen cars are more dangerous or less.
Not saying gasoline is safer.
I've only given you facts about hydrogen and how it could possibly ignite in a crash, you keep denying time and time again. Because of those videos, which again, were liquid nitrogen, the only gaseous hydrogen they showed was in a ball tank that..exploded.
Listen, i don't care what is safer, i feel its too early to tell, and so far they're doing great. I'm waiting for when the rare event happens that levels peoples homes comes up. Until this conversation i was under the impression that no way would people park these in garages but that opinion has changed.
Hypx OP t1_j65tes6 wrote
If you are admitting that gasoline is not safer, then what's the point of this conversation?
TheAnonFeels t1_j65tzxh wrote
Not admitting anything is safer...(Last paragraph of latest comment, if you forgot already)
The point?
- My own imagination here is that i can convince you my only point here was telling you hydrogen COULD ignite...
idek what to say anymore.. You literally aren't comprehending anything i type, even just conversational statements... This is so difficult to repeat myself and now I learn you still don't know my point...
I honestly wish, I wish so hard, my brain was like yours. Life would be easy.
Hypx OP t1_j65und1 wrote
Then your posts are total gibberish. You are trying to say something while admitting that you aren't trying to make a point at all.
There is nothing to comprehend in your posts. It's just word spam.
TheAnonFeels t1_j65ve6x wrote
>Then your posts are total gibberish.
Is it that hard to understand?
The comment I first made, was only talking about ignition, you keep telling me i'm against hydrogen cars.. I keep going back to informing you hydrogen can ignite, and dangerously.
I see where you got confused.. You thought i was conflicting with your world image.
Hypx OP t1_j65vug4 wrote
Which is stuff I admitted from the very first post. Yes, it can ignite. With an ignition source. Yes, it is dangerous, but less so than gasoline.
But of course you went off with multiple posts of pure spam and fearmongering before admitting that there is no real danger.
You're plainly trolling at this point. Time to stop and move on.
TheAnonFeels t1_j65xrbn wrote
Sorry we couldn't have an actual conversation but seems you don't know how.
BoredCop t1_j63bqup wrote
Explosions have already happened in hydrogen refueling stations.
Hypx OP t1_j63bua7 wrote
You mean fires, not explosions. Also, many things have exploded or caught on fire. Including existing gas stations.
BoredCop t1_j63ddkn wrote
Nope, I mean explosions. A chain of hydrogen stations in Norway got temporarily shut down for safety reasons after one exploded in 2019, that's the one I could find info on quickly.
Hypx OP t1_j63dwrf wrote
You one caught on fire? These things aren't report very accurately.
BoredCop t1_j63ivq7 wrote
Exploded. Pictures in media show parts of the station that got thrown some considerable distance by the blast. Investigative reports also call it an explosion.
Hypx OP t1_j63kn89 wrote
Fires can have pressure waves, but that is not an explosion. And if you do call it an explosion, than there are thousands of gasoline explosions all time.
BoredCop t1_j63l199 wrote
Are you conflating the terms explosion and detonation? Because you can absolutely have the former without the latter. When a mix of fuel and air between the lower and upper explosion limits for that fuel ignites, you get an explosion. Not all explosions are high order detonations.
Hypx OP t1_j63lfp9 wrote
Explosions technically imply detonation. But if you are going to call all big fires explosions, then gasoline explodes too. You cannot have it both ways.
Anyways, it's already proven that hydrogen is safer than gasoline because people have actually set them on fire before. You're just fearmongering on this.
BoredCop t1_j63oahs wrote
You might wish to read up on the definition of "explosion". And I've already commented on those videos.
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