Hydrogen vs. Battery

[Aury]

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You can't just use random accidents involing hydrogen and start scare mongering people. SAE has a journal and has been detailing HFC safety measures since 2006, at least quote from there for accurate information.

What you're doing is like me saying Teslas are unsafe and posting a scary picture of an airplaine that crashed because the lithium battery caught fire, like this one, it's dishonest.

The reason some companies are actually looking at hydrogen as back up fuel is because unlike gasoline, hydrogen is not corrosive, and not toxic. So any accidents wouldn't have a long lasting effects on the operations of a plant.

To say hydrogen simply explodes or all you need is a spark or a pressure issue, is fear mongering, HFC have a strong shell, have compartments, the nossle is extremely secured to avoid leakage, and HFC have been through rigorous testing.

There are two sorts of Tesla fans I have noticed, people who embrace new technology, and people who will do anything to make other technology look outdated / dangerous / inferior, just because it's a different market than the one Tesla is in.

Your HFC isn't going to blow up, it's not going to cause an explosion, and they're safe cars that went through more testing than many other technologies. If a HFC car could blow up half a block, they wouldn't be on the road, they can't, don't suggest they can because that's dishonesty.

 

[Yggdrasill]

There will be explosions if hydrogen fuel cell cars are widely adopted. These explosions may happen in situations like the stolen Tesla, where the car is mangled beyond recognition, crushing the hydrogen tank and leading to rapid emptying of the hydrogen tank into an environment with numerous ignition sources. Some explosions may happen in garages, where suddenly there is a significant leak, the room fills up with hydrogen and then there is a spark.

Saying it's impossible for there to be a hydrogen explosion is like saying the Titanic is unsinkable. Sure, hydrogen is mostly safe, just like ships are mostly safe, but accidents can and will happen.

(Personally, my biggest worry is the hydrogen fueling stations that people are suggesting that you could install in your home. It's only a matter of time before improper maintenance and misuse leads to something going very very wrong.)

 

[MacroP]

Hydrogen usually doesn't explode or catch fire, since it evaporates upwards in seconds, for hydrogen to be dangerous you need the right concentration of oxygen and hydrogen, and it's rare that actually happens.

Hahaha and as far from the truth that I could think - Hydrogen has nearly the highest range of explosive limits. Rich or lean and mixed with air - it's going to go up very easily especially in a vehicle accident. I've worked with the stuff on a large scale as it's used for cooling in this particular task. Went you see Hydrogen gas alarms around the workplace you start to think. I can only think of one gas with a broader range of LEL and HEL and that's Acetylene and that's normally dissolved in Acetone to keep the cylinder pressure down. Hydrogen doesn't have that benefit.

Now strap this stuff in a cylinder, at a ultra high pressure, and put it into a car flying down the highway which wraps itself around the nearest power pole and watch the outcome.

Sure it can be used safely in a controlled work environment with all the HAZMAT and Safe work procedures but in an everyday car? - that will be very hard to maintain and control on a large scale. Even if it doesn't ignite in a vehicle accident - if the tank is ruptured - the outcome around it won't be pleasant. That's it down fall.

 

[JRP3]

Your HFC isn't going to blow up, it's not going to cause an explosion, and they're safe cars that went through more testing than many other technologies. If a HFC car could blow up half a block, they wouldn't be on the road, they can't, don't suggest they can because that's dishonesty.

The only thing that's dishonest is your claim that a 10,000 psi hydrogen tank can never blow up. Anything can and will eventually fail, especially in a vehicle. If it's something that's sitting at 10,000 psi when it fails it will likely be spectacular. You are clearly showing what type of "hydrogen fan" you are.

 

[Yggdrasill]

I was curious, so I ran the numbers on a large-ish two car garage. You would need to release in the area of 2-7 kg of hydrogen for the fuel-air mixture to be explosive. That means that if a hydrogen car parked inside such a garage were to rapidly release it's 5 kg of hydrogen, the fuel-air mix would be quite perfect for detonating.

A slower leak might reach the ideal fuel-air mix, but it depends on a large amount of variables. Detonation due to a slow leak would most likely only happen in a smaller garage, and probably wouldn't be as destructive as a rapid release.

 

[TonyWilliams]

You can't compare a hydrogen fuel cell to a hydrogen tank, the maginitude of the explosion has more to do with the evaporation rate than with the amount of hydrogen. It wouldn't be possible for a car to cause an explosion like that, it's dishonest to claim it could cause such an explosion, hydrogen is dangerous when it's released in a way that allows for the right oxygen to hydrogen concentration, only then is there a danger for explosions, and because of how HFC are constructed, that's not possible for passenger cars.

Complete BS.

The hydrogen fool cell vehicle absolutley has a very high pressure tank to store the hydrogen. The fool cell merely converts that stored energy to electricity and water.

 

[rabar10]

If you think hydrogen is unsafe, you haven't seen accidents with regular gasoline yet

The vast majority of people have more familiarity with gasoline fires than with hydrogen fires/explosions.

Hydrogen usually doesn't explode or catch fire, since it evaporates upwards in seconds

Hydrogen gas cannot evaporate -- it's already a gas. It is lighter than air, so if unconfined would float up and away. But it has to "get away" before catching fire first -- see below.

for hydrogen to be dangerous you need the right concentration of oxygen and hydrogen, and it's rare that actually happens.

If by "rare" you mean hydrogen in air at any ratio between 4% and 75% will support deflagration (fire), then that's a very strange definition of the word. Only one other molecule -- acetylene -- is known to have a wider air-mixture burn ratio. Also, a hydrogen/air mixture has a very low ignition energy -- 1/10 of that required to light a gasoline(mist or vapor)/air mixture. So in any hydrogen leak event, fire can be considered very likely. Please see Wikipedia and its plethora of linked sources for references.

If the Hindenburg had been filled with gasoline instead of hydrogen,

...it would have never left the ground? (This is equally true of gasoline whether in vapor or liquid state, by the way)

The fact hydrogen evaporates so quickly is what makes it relatively safe during accidents, there are many many substances with low viscosity like gasoline that can be more dangerous than hydrogen.

This sentence is bordering on nonsensical. Gases are not liquids.

You can't compare a hydrogen fuel cell to a hydrogen tank, the maginitude of the explosion has more to do with the evaporation rate than with the amount of hydrogen. It wouldn't be possible for a car to cause an explosion like that, it's dishonest to claim it could cause such an explosion, hydrogen is dangerous when it's released in a way that allows for the right oxygen to hydrogen concentration, only then is there a danger for explosions, and because of how HFC are constructed, that's not possible for passenger cars.

The fuel cell in a HFCV is used to convert hydrogen and atmospheric oxygen into electricity, to drive the motors. But where is that hydrogen stored, I wonder? Oh yes -- in a 10,000-psi tank.

 

[CalDreamin]

Hydrogen usually doesn't explode or catch fire, since it evaporates upwards in seconds, for hydrogen to be dangerous you need the right concentration of oxygen and hydrogen, and it's rare that actually happens.

The right concentration of hydrogen in air to form an explosive mixture is anything between 4% H2 (the LEL) and 75% H2 (the UEL), one of the widest ranges between the LEL and UEL of any flammable gas. Hydrogen-air mixtures also have a very low energy for ignition, only about 1/10 the minimum ignition energy of gasoline-air mixtures. In the case of the hydrogen explosion industrial accident I referenced above, a hot motor bearing provided the ignition source.

The fact hydrogen evaporates so quickly is what makes it relatively safe during accidents, there are many many substances with low viscosity like gasoline that can be more dangerous than hydrogen.

Hydrogen stored in FCVs doesn't evaporate. It's always a gas, never a liquid. A gasoline fire in a car cannot explode with the blast energy that 6 kg of hydrogen mixed in air can cause because only the small fraction of gasoline that vaporizes can explode. Viscosity has little to do with it.

You can't compare a hydrogen fuel cell to a hydrogen tank,

I've been discussing the 10,000 psig H2 tank within a fuel cell vehicle, where the H2 is stored.

the maginitude of the explosion has more to do with the evaporation rate than with the amount of hydrogen. It wouldn't be possible for a car to cause an explosion like that, it's dishonest to claim it could cause such an explosion, hydrogen is dangerous when it's released in a way that allows for the right oxygen to hydrogen concentration, only then is there a danger for explosions, and because of how HFC are constructed, that's not possible for passenger cars.

Again, hydrogen doesn't evaporate in this scenario. It's already a gas. In a catastrophic rupture of 10,000 psig H2 (or 1000 psig H2), it does not have time to drift up. Instead it expands to a large volume with explosive decompression. This is likely followed by detonation since the difference between the LEL and UEL is so wide, and the energy of ignition is so low.

 

[Doug_G]

for hydrogen to be dangerous you need the right concentration of oxygen and hydrogen, and it's rare that actually happens.

Okay, that is simply dead wrong. Hydrogen is explosive in air in concentrations of 4% to 75%. In comparison gasoline vapor is explosive in concentrations from 1.2% to 7.1%. In short, Hydrogen is an order of magnitude worse. Hydrogen is already a gas so it does not need to vaporize, it only needs to leave the tank. Which it will do at extreme velocities if it is ruptured given the extreme pressure involved.

They're not talking about the fuel cell exploding, they're talking about the storage tank in the car exploding.

 

[rabar10]

So to summarize -- hydrogen gas, especially when pressurized, can be very dangerous.

While it is certainly possible to engineer systems around high-pressure H2 to provide the required safety factors, the cost and weight of these systems work to make hydrogen-powered vehicles more expensive and less efficient.

This is in addition to the questions of sustainability vs. efficiency in sourcing hydrogen gas, and the need for an extensive distribution/refueling infrastructure.

 

[green1]

The biggest safety issue I see here is around maintenance and inspection. High pressure cylinders require periodic inspection, sure, during the warranty period on a FCV this is likely to happen, but imagine the 20 year old FCV that some teenager bought used and is planning to drive in to the ground... If his gasoline tank rusts out and fails it's a minor environmental issue, if his H2 tank fails... well he could take quite a few innocent people with him.

 

[CalDreamin]

You can't just use random accidents involing hydrogen and start scare mongering people. SAE has a journal and has been detailing HFC safety measures since 2006, at least quote from there for accurate information.

I chose this particular industrial accident to illustrate the blast damage from an explosion of 3.5 - 7 kg of hydrogen in air, the same amount of hydrogen that would be stored onboard a H2 FCV.

The reason some companies are actually looking at hydrogen as back up fuel is because unlike gasoline, hydrogen is not corrosive, and not toxic. So any accidents wouldn't have a long lasting effects on the operations of a plant.

That's not correct, there are several mechanisms of material damage and failure caused by hydrogen.

To say hydrogen simply explodes or all you need is a spark or a pressure issue, is fear mongering, HFC have a strong shell, have compartments, the nossle is extremely secured to avoid leakage, and HFC have been through rigorous testing.

The barriers can fail, through a range of failure scenarios. At that point one is left with potential consequences that can be 1-2 orders of magnitude more severe than a gasoline car fire. This isn't fear mongering, it's a fact.

Your HFC isn't going to blow up, it's not going to cause an explosion, and they're safe cars that went through more testing than many other technologies. If a HFC car could blow up half a block, they wouldn't be on the road, they can't, don't suggest they can because that's dishonesty.

The probability of a FCV hydrogen explosion is low, probably lower than a gasoline fire from an ICE. But the consequences can be very high, much worse than a gasoline car fire. If there are hundreds of thousands or millions of FCVs on the road, catastrophic hydrogen explosion incidents involving them will likely happen.

 

[Johan]

Aury get your science straight. You just got p0wned.

Thanks all others for good insight on the explosiveness of hydrogen.

 

[roblab]

Aury get your science straight. You just got p0wned.

Thanks all others for good insight on the explosiveness of hydrogen.

This guy sounds like one of our California Representatives. He believes with all his soul whatever the CARB and Fuel Cell Partnership people tell him, and all the rest of us just don't know the facts. We are always wrong, fear mongering, against change (!), against competing technologies. No matter what anyone points out, whether it's the pollution, the misappropriation of funds, the dangers, the complexity, the transport problems, we are all just biased against FCVs. Same as Aury.

Our Rep has been arguing this way for years now, and no one can change his opinion. I don't hold out much hope of anyone convincing Aury, either. Some people just don't WANT to get it.

 

[Reykjavik]

I'm not convinced that hydrogen is more dangerous than gas.

There was an industrial accident that demonstrates the magnitude of the consequences from an explosion involving 3.5 - 7 kg of hydrogen -- which is coincidentally the amount of H2 in one FCV tank.

From the article linked: "The total mass of the hydrogen was estimated at 10 to 20 kg hydrogen."

That means somewhere between 1/6 and 2/3 of the hydrogen actually burned in the explosion. And not all of the hydrogen in the system escaped. To get 3.5-7 kg of hydrogen into the air, it has to come out of the tank, which will drop the pressure significantly. There is definitely a danger of a large explosion, if the tank is full and ruptures, but I think the frequency of dangerous fires and explosions may be less than with gas.

The reason is that gas pools, evaporates, and burns. The range of fuel/air mixtures that burns for gas is smaller, but because it can pool and continually evaporate under normal conditions, it can have a fume cloud in a burnable state for quite some time, and once it gets started it burns hot for quite some time. Gasoline is very dangerous, and a well engineered tank and safety system for a FCV may well be less risky than having gasoline everywhere in relatively unprotected tanks. In a typical car accident with a hydrogen tank, it is less likely that the tank will fail at all, and if it does, it will probably be a small enough leak or a safety valve that releases hydrogen slowly enough that ignition won't be catestrophic.

On average, the relatively high frequency of gas fires causing deaths may be worse than the low frequency of catastrophic H2 tank failures.

Of course, hydrogen is still very dangerous, especially compared to batteries, which so far, even when crashed into things at a 100 mph just sizzle for a few minutes, more than enough to get out of the car in most cases, and then the resulting fire isn't as energetic as either a gas fire or hydrogen explosion.

 

[Doug_G]

Gasoline is not really very flammable. It is one of the reasons it was chosen as an automotive fuel. It takes very specific conditions to create an explosive mixture. If you drop a match in gasoline it will go out. It's the vapor that has the potential to explode, and only under very specific conditions of concentration and temperature, and it takes a fair bit of a spark to set it off. Yes the liquid will burn, but it takes a little while to get a fire going. Actual explosions in an automobile are extremely rare because of all of the above, even though fires are commonplace.

Hydrogen is explosive in air under a far greater range of conditions, and takes far less energy to initiate the explosion. It has to be stored at a pressure that is in itself explosive should the containment fail. I expect that hydrogen incidents will be less common (hopefully!) but far more serious than gasoline incidents. Just wait until some terrorist figures out what you can do with it.

 

[Aury]

Relative to diesel, gasoline is quite flammable, that's one of the reasons we drove diesels in the army.

As far as hydrogen cars exploding, you guys need to give it a rest with the fear mongering, it's petty and childish to see people like this. Most Tesla drivers I know aren't like this at all.

 

[Yggdrasill]

Yeah, diesel is a lot less flammable than gasoline. Still, diesel cars burn as well.

And this is not fear mongering. We are merely discussing the realities of hydrogen vehicles.

 

[Reykjavik]

Gasoline is not really very flammable. It is one of the reasons it was chosen as an automotive fuel. It takes very specific conditions to create an explosive mixture. If you drop a match in gasoline it will go out. It's the vapor that has the potential to explode, and only under very specific conditions of concentration and temperature, and it takes a fair bit of a spark to set it off. Yes the liquid will burn, but it takes a little while to get a fire going. Actual explosions in an automobile are extremely rare because of all of the above, even though fires are commonplace.

It isn't that hard to get a mixture that will burn. Explosions are rare, fires are not. In a bad crash, fire is a real danger, the gas leaks out of fuel lines or the tank, flows and drips its way to the ground, forms a pool, and then starts to evaporate. Gas evaporates pretty easily, and the concentration of fuel vapor right at ground level above the liquid is high, as you go up it gradually decreases as the vapor starts to diffuse into the air. If it catches fire, and it often does, the source of the flame is directly below the passengers if they are trapped in the vehicle.

On the other hand, most hydrogen fires will be jets coming directly out of the tank. If it isn't pointed at someone or directly below them, the harm is likely to be less.

As for explosions, hydrogen is more dangerous, but it is not at all clear what the frequency of explosions will be, and there is not enough evidence to demonstrate that hydrogen will actually be more dangerous than gas, which causes deadly fires all too frequently.

 

[adiggs]

What's the "right" answer for large commercial vehicles though? BEV tech would be too costly and recharging times too high for commercial trucks and buses. Is Hydrogen a better answer there?

BYD brought a BEV city bus to the "Celebrate Hillsboro" day back in July. I believe they've run it as a demo vehicle / bus on local Tri-Met bus routes as part of a demonstration project. Outside of the BYD sales person being a <unprintable>, the info on the bus sounded amazingly good to me. Enough battery range that the bus can routinely run for 8-15 hours (depends on the route mileage, with I believe a preference for shorter/slower routes for the battery bus). It sounded like for many bus routes, it would be completely reasonable to start the bus off with a full charge at the beginning of the day, drive it all day on the route (probably changing drivers along the way), and then bring it back to the barn at the end of the day to charge overnight.

That's a usage model for city bus transport that sounds amazingly good. I didn't get more info about the bus though - for some reason, the BYD sales person, upon learning that I drive a Tesla and was showing it elsewhere, seemed to have the impression that (a) I worked for Tesla, (b) his bus and my Roadster were competing in the market with each other, (c) BYD and Tesla are competing for the bus business in the greater Portland area, and/or (d) the effective way to build up his product / technology was to denigrate the "competition". (I was speechless - just left).

Anyway - if the mileage for the day is closer to 100 - 150 miles (which apparently is common for bus routes), then I've stood inside of a BEV bus in the last month or so that claims the ability to do exactly that.

- - - Updated - - -

The state of California never really promoted DC fast charging infrastructure like they will do for hydrogen. There are many reasons for that, but the bottom line is that Washington and Oregon both actually did build a West Coast Electric Highway. You can drive a short range car like a LEAF just about any place you want to go.

That's what California could have done, too.

http://www.westcoastgreenhighway.com/pdfs/WCEH_infrastructure.pdf

West Coast Green Highway: Home

And I've seen the WCEH at work in Washington / Oregon during the BC2BC rally last year. It was easy for me, as a Roadster owner/driver, to make the case that I'd have been better off covering Washington and Oregon in a Leaf than the Roadster. Over those longer distances, charging times dominate.

Obviously the Supercharger moved the goal posts again, making all of the rest of us slow compared to the Model S.