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Thread: The oil crisis may soon be over

  1. #25

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    *Wonders what is more explosive, compressed air or lithium-based batteries*

  2. #26
    Cardiac Nurse JB_OrchidGuy's Avatar
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    Quote Originally Posted by phissionkorps View Post
    Yes it needs oxygen to be combustible, which is why when the tank ruptures an explosion ensues.
    PK I am not talking about that. Give me a little credit. I am not a doofus. I know that hydrogen and O2 are combustible, but what I am saying is it has to be in a certain ratio to be that way. If there is too much hydrogen then it is not flammable from what I have read. or too much O2 it is not flammable. That is what I am saying.

    I was asking if that is true or if I am going to have to find what I read from BMW site.

    I agree whole heartedly about the rail system. It needs to be used more often. The rail company claims to be able to move 400 tons of freight 400 miles with one gallon of fuel. I think i have my numbers wrong but it is a very very high one. Trucks should only be used for local deliveries.
    JB
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  3. #27
    Doing it wrong until I do it right. xvart's Avatar
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    I was thinking more along the lines of a pressurized explosion. Like if you puncture a pressurized container it will "explode out" and the pressure is equalized. No flames, but significant shrapnel, noise, and damage.

    xvart.
    "The tragedy of life is not that every man loses; but that he almost wins."

    "Quis custodiet ipsos custodes?"

  4. #28
    Cardiac Nurse JB_OrchidGuy's Avatar
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    no the tanks for liquid hydrogen are ridiculously dense and built to withstand an wreck supposedly.
    JB
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  5. #29

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    I agree with you on the part about not being emission free because currently we do get out hydrogen from fossil fuels. Yet the storing of hydrogen storage in cars I disagree with. BMW has made a hydrogen powered combustion engine. Not a fuel cell, but it actually burns the hydrogen making water. They store liquid hydrogen in a tank behind the seat. They crash tested the tank and it is VERY strong. They dropped a full tank from a ridiculous hight and it didn't rupture. I read it on the BMW site. Also hydrogen has to be in certain proportions with O2 to be combustible, or so I am told. Is that wrong?
    Basically, the real question is "can you make the tank strong enough without it weighing too much?" Back in the 70's when they produced the SR-71 Blackbird (that big, long, flat black plane with huge engines capable of reaching over Mach 3), they rejected hydrogen as a fuel because of the possibility of explosion. However, a) it was in an airplane, therefore had much narrower weight restrictions and b) it was long before modern composite materials.

    Now, with composites, BMW could do it easily, but composites are not simple to make. Metal you just pour in a mold, but for woven-fiber composites (the best kind), hand assembly is still required for the vast majority of applications (I've actually worked doing so once). So the question is, "can they make enough of them at reasonable cost"?

    Finally, there's another problem with composites, which is delamination. Because there are numerous layers, failures can occur by the layers separating. This is exacerbated by extreme temperatures (heat or the extreme cold of liquid or compressed hydrogen) and simple duration.

    Maybe I'm not giving them enough credit, but I would only trust it if they loaded with H2, unloaded it, repeated the cycle a good 100,000 times (nothing that can't be done via machine in a few weeks), filled it again, *then* dropped it.

    It's not impossible, but with alternatives such as batteries, metal hydrides, and compressed air, I'm skeptical of whether it's worth the bother.

    Mokele
    \"With malleus aforethought, mammals got an earful of their ancestor's jaw.\"
    --J. Burns, on the evolution of auditory ossicles.

  6. #30
    Cardiac Nurse JB_OrchidGuy's Avatar
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    Ok maybe the liquid hydrogen was not a good idea. It seems now more stuff is out about BMW's car and I don't like it. Because the hydrogen7 is tuned to run on hydrogen and gas its economy stinks for both. when storing the liquid hydrogen in the tank, if you don't use it it will slowly evaporate out the tank because as it warms the tank automatically vents the pressure. In 7-10 days your hydrogen tank is empty. It only gets like 4.7 miles per gallon on hydrogen too. So far I like Honda's clarity that runs on a fuel cell. It is being released in Cali for a lease of $600 a month for 3 years and has limited areas to fill its hydrogen tank. Honda is still looking to build a home fueling system, but what I see it is trying to get all the hydrogen from natural gas too. That is not good. Why not solar power?

    I need to get off my butt and buy the parts I need to build my prototype. If it works it will be able to be expanded upon to power a car for free. It is jus not supposed to work. I have to be hardheaded and try it anyway.

    Hydrogen 7
    JB
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  7. #31
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    It doesn't really matter here, but the lower explosivity limit (LEL) for hydrogen is 4% and the upper explosivity limit (UEL) is 75%. Basically, if you have an atmosphere which is 4% to 75% hydrogen by volume, it's explosive. If hydrogen is below or above that range, the atmosphere isn't explosive. Those are for hydrogen in air, not oxygen, by the way, and also at standard temperature and pressure, for the detail-oriented amongst us. For comparison's sake, gasoline has an LEL = 1 and UEL = 7.

    On to the real issue, I agree with Mokele, although I'm not sure dropping a tank 100,000 times is enough of a test. I'd also like to know how it and all the downstream components handle long-term exposure to hydrogen. Hydrogen is bad stuff because it is highly reactive and can cause all kinds of chemical and structural mayhem. That's bad news for composites.

    Don't trust manufacturers - a lot of underground piping installed at gas stations during the 80s-90s was damaged by contact with gasoline. The internal liner was resistant to gasoline, but the outer layer, which provided the piping's strength, swelled and came apart if exposed to gasoline. Unfortunately, the stuff was used in previously contaminated sites and new spills aren't uncommon. I'd like to think hydrogen tank design & construction would get more forethought, but experience says it won't. Especially when companies contract out the manufacture to the lowest bidder.
    Bruce in CT

    Madness is something rare in individuals but in groups, parties, peoples, ages it is the rule. Friedrich Nietzsche

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