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Lithium Hydride as energy source for Combustion Engines

  1. Jun 26, 2013 #1
    Lithium Hydride contains more hydrogen per unit volume than liquid hydrogen does, so what is stopping us from developing a Lithium Hydride storage solution to supply hydrogen to a vehicle's engine?

    The reactivity of the substance would throw up some substantial challenges, but compared to distributing gaseous Hydrogen, it seems to me that a solution that allows a solid substance to be used, with a higher energy density than elemental Hydrogen would be something worth looking at.

    An easily swapped out combination Reaction Chamber/Storage Unit would need to be designed that would allow for the LiH to be mixed with water to release the hydrogen content for use as a fuel, and some way to input measured amounts of the LiH to the reaction chamber, but surely, this is do-able.

    Lithium hydrides are white crystalline solids (m.p. 620 deg C), of generally salt-like physical character. The term "lithium hydride" may refer specifically to a compound of light hydrogen or may be used generically to refer any lithium-hydrogen compound regardless of hydrogen isotope. They are usually prepared by direct reaction between hydrogen and metallic lithium at elevated temperature. Lithium hydrides have low density (0.82 for LiH). Lithium hydrides have no known solvent. LiH reacts violently with water, producing hydrogen gas and have been used in the past for special purpose hydrogen gas generators, such as those used to inflate lifeboats. (Thanks to Corey Sublette for this detail).

    Granted, there are some proliferation concerns with enriched Li-6 and even natural Li-7, but I can picture a car pulling into a station and having a (large) fuel cartridge replaced by a robot in a few minutes, from the same spot that a gas tank already sits in and something of the same size.

    And all it spits out is water, so the greenies will be happy.

    Thoughts?
    Am I crazy?
    Cheers.
     
  2. jcsd
  3. Jun 27, 2013 #2

    Danger

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    I've never thought of lithium hydride in this context. I do know, however, from my research about 35 years ago, that magnesium hydride was being used as a solid hydrogen fuel tank with a storage density of over 1gm/cm3. If you chill a block of magnesium, it adsorbs hydrogen; when you heat it, it releases the hydrogen again in gaseous form.
     
  4. Jun 27, 2013 #3

    SteamKing

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    There's only so much lithium to go around. At one time, it was uncertain that enough lithium could be produced to supply the demand which would result from supplying batteries for all the electric or hybrid vehicles which would be manufactured to replace autos with conventional combustion engines. Besides batteries, lithium is also used for pharmaceuticals and as an alloying agent for lightweight metals, among other things.
     
  5. Jun 27, 2013 #4
    You said it yourself. The reactivity makes it extremely dangerous as a general purpose fuel. Moisture from the air could cause the powder from to self ignite. Firefighters do not have at their disposal any traditional method to extinguish a lithium hydride fire once started, and with car accidents what they are, that could pose serious problems for public safety.
     
  6. Jun 27, 2013 #5

    mheslep

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    The point from the OP is a reusable storage material. Unlike energy, the lithium would of course not be consumed, or likely even dispersed for such a use. 39 million tons estimated in global reserves.
     
  7. Jul 5, 2013 #6
    thanks mheslep, I saw some estimates of global reserves somewhere and I seem to remember that Lithium is one of the most common elements, though reserves with high enough % to be economical to mine are another thing.
    And thanks again, I didn't consider the re-usable aspect of the elemental Lithium, of course, it makes perfect sense.. Maybe all those tons of disposed Li Ion batteries could be recycled for this use.
    I envision something like a car wash setup, with a robot removing your used Fuel Cell and replacing it with a renewed one..
    Too bad I can't register on Kickstarter, I'm not in the USA..
     
    Last edited: Jul 5, 2013
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