

Toyota Fine-S Concept hydrogen fuel cell vehicle

Toyota Highlander-based fuel cell vehicle
Toyota expects the market to be small, but avaialble











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RE: News Flash: May 6, 2011
By Lord 666 on 5/7/2010 11:00:54 AM , Rating: 2
Your kidding right? If a Toyota hydrogen car bursts into flames and crashes, the cause of death will be more than likely blunt trama or burns. However the root cause would be the hydrogen.

Same thing would happen if you keep smoking that crack; the cause of death would be a heart attack, but the root cause is your drug habit.

RE: News Flash: May 6, 2011
By HotFoot on 5/7/2010 11:32:24 AM , Rating: 1
There are a lot of theories as to what actually caused the fire to break out on the Hindenburg. A hydrogen gas fire is one of the least plausible, in my opinion. Hydrogen-air mixture is only combustible within a certain range of concentration, and explosive within a very small range of concentrations. Hydrogen gas diffuses at a phenomenal rate compared to heavier molecules, such as those that make up gasoline or diesel. A hydrogen leak has a very small risk of causing a fire or explosion compared to other fuels.

RE: News Flash: May 6, 2011
By porkpie on 5/7/2010 11:43:12 AM , Rating: 3
"Hydrogen-air mixture is [only] explosive within a very small range of concentrations"

This isn't correct:

RE: News Flash: May 6, 2011
By HotFoot on 5/7/2010 11:51:04 AM , Rating: 2
Excellent reference. I'm going to keep a copy of that for work. We've also had a good deal of debate about the placement of H2 purge interfaces. I'm arguing that, other than very locally to where a leak/ruptured tank is, the H2 purge interfaces don't necessarily need to be high up in a room, because I'm under the impression that only concentrations of H2 will tend to rise. On the other hand, diluted H2 I think will need to be purged from the whole volume. This is compared to our more normal heavy-fuel vapour purge interfaces, which we place lower in the room.

RE: News Flash: May 6, 2011
By cpeter38 on 5/7/2010 12:16:09 PM , Rating: 2
However, the definition of "explosion" in the various tests in that study is that the flame propagates. While that may be a nice experimental way to define an "explosion", I have a hard time equating that with a real explosion.

There are only two things that concern me about atmospheric hydrogen combustion:
1. The flame is very difficult to visually detect.
2. If there is a large amount in a contained space (such as a blimp full of hydrogen), the oxidation event could cause a significant pressure wave.

Here are a few things that make me feel much more safe about hydrogen powered vehicles:
1. The amount of energy contained in 1 kg of hydrogen is about the same as 1 gallon of gas. The typical hydrogen powered vehicle has significantly less than 10 kg of hydrogen when completely full (the long range of fuel cell vehicles is possible because the conversion to mechanical energy is MUCH more efficient than gasoline to mechanical energy).
2. If all safety systems failed and there were a fire, hydrogen fires radiate very little energy. There is almost no damage if the flame does not directly contact something else.
3. Hydrogen does not stay in the local area unless it is intentionally contained with engineered components. It is actually very difficult to keep hydrogen contained. Typically, precision machined components and seals are required. Therefor, any leak would rapidly dissipate into the atmosphere.
4. The safety systems on FCVs are much better that the safety systems on conventional cars.

RE: News Flash: May 6, 2011
By porkpie on 5/7/2010 1:58:49 PM , Rating: 2
"However, the definition of "explosion" in the various tests in that study is that the flame propagates"

Deflagration vs. detonation, to be precise. That's how all lower/upper explosivity limits are defined, even for gasoline. Still, a confined deflagation generates enormous pressures, and even an unconfined one can break 100psi.

If you prefer to work off detonation limits, they are, for H2, 18-59%, whereas gasoline operates at 1.1-3%. For H2, an unconfined detonation can generate an order of magnitude higher overpressures.

RE: News Flash: May 6, 2011
By geddarkstorm on 5/7/2010 1:24:51 PM , Rating: 1
Actually, reading that paper shows just how safe hydrogen is over gasoline!

The explosion pressure ratio to starting pressure conditions, at the highest, most explosive hydrogen point of 35% hydrogen, was only 8. That means, the pressure went up by 8x in the vessel over what it was set at originally. 8 atm by the way is only 117 PSI.

Moreover, the higher the operating temperature, the lower the explosive pressure. Higher storage pressure of the hydrogen also decreases the range at which hydrogen can be explosive, albeit not by much.

Finally, they used high voltage to spark the hydrogen (except one test which used a fusing, exploding, wire). And, since hydrogen has nearly 3000x less energy per volume as liquid gasoline in calorific measure (that is, explosive potential in this study), you are hardly going to get even a fizzle out of it relatively compared to the gasoline you cart around in your vehicle.

Really, the only "explosive" danger of hydrogen is the sudden decompression of a hydrogen storage tank. Furthermore, unlike gasoline, hydrogen isn't going to sit around and burn for a prolonged period of time since it'll diffuse. And it's that constant fire that is really what's dangerous to a person anyways. Hydrogen will be a flash and a bang, and that's about it., at worst. Only if it ignites some other source is it truly dangerous (or again, a really really high pressure storage tank explosively decompressing would also be extremely dangerous).

RE: News Flash: May 6, 2011
By porkpie on 5/7/2010 1:53:18 PM , Rating: 3
"That means, the pressure went up by 8x in the vessel"

I'm sorry, but it doesn't work the way you think it does. Explosion overpressures are low for pretty much all flammable fluids and gases....they only "explode" if they're contained. This is in direct contrast to the so-called "high explosives", which do not need containment to generate a large explosive force.

Gasoline's explosive pressure is actually about 80% lower than that of H2. H2 is higher than gasoline, and about 4X higher than something like propane or methane.

"since hydrogen has nearly 3000x less energy per are hardly going to get even a fizzle"

That isn't the proper comparison, as the lower volumetric energy density at STP means you must compress much more H2 into a given volume. Hydrogen actually has higher energy per unit mass...but that isn't a valid comparison either.

The proper way to compare is to calculate the explosive yield per unit stored energy. If you do this, gasoline comes out slightly ahead of H2...but only slightly.

RE: News Flash: May 6, 2011
By sleepeeg3 on 5/7/2010 7:16:18 PM , Rating: 1
Hydrogen safe? Think again.

Take a look at the YouTube videos of exploding hydrogen balloons:

My chemistry teacher did this experiment in a small lecture hall with a balloon twice as big. I was about 30 feet away and it was about as loud as a shotgun blast, plus a hot compression wave.

Now imagine an accident and a compressed tank full of that igniting. Body parts everywhere! DailyTech even had an article showing that some companies even want to switch to fragile glass tubes!!!

Safe like the Hindenberg...

RE: News Flash: May 6, 2011
By porkpie on 5/7/2010 10:14:00 PM , Rating: 3
"Take a look at the YouTube videos of exploding hydrogen balloons:"

Try the same experiment with gasoline. Youtube is a poor source for scientific knowledge.

The real facts are this. Gasoline and hydrogen both are far, far safer than the real danger for moving vehicles -- the kinetic energy of the car itself. Arguing over which is safer is essentially like standing on a cliff with vaseline-coated feet, wondering if that splinter in your finger is going to give you a nasty infection.

RE: News Flash: May 6, 2011


RE: News Flash: May 6, 2011
By Silver2k7 on 5/10/2010 10:33:54 AM , Rating: 2
well if you find a way to put water in the tank, and then slowly on demand split the water into hydogen and oxygen.. then you would have a tank full of water if crashing.

hopefully there are some people working on this.

welding machines wich used water to make a mixture of oxygen and hydrogen wich they called HHO comes to mind.. not sure how fast it made the mixture or how much electricity it takes to make it.. but should be worth looking into.

RE: News Flash: May 6, 2011
By porkpie on 5/10/2010 11:33:23 AM , Rating: 2
I don't mean to be rude, but I got a nice chuckle out of this. Splitting water takes energy. If you have that energy on board your car with you, why would you want to make hydrogen with it...just to burn that hydrogen and get only part of that energy back? Just use it directly to power your vehicle.

