Electric cars are a pipe dream

Discussion in 'General Science & Technology' started by Syzygys, May 20, 2010.

  1. ElectricFetus Sanity going, going, gone Valued Senior Member

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  3. elte Valued Senior Member

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    Car makers are in some trouble when it comes to their future viability. I have long said that they should try to leverage technological advancements to make cars cheaper, more reliable and low maintenance. The younger generation wants something as trouble free as an electric skateboard. They don't want a car that owns them rather than them owning it.
     
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  5. billvon Valued Senior Member

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    So does NH3 production*. As I am sure you are aware, NH3 is produced from CH4. I think it's easier just to use the CH4 as-is rather than going through the energy-wasting steps required to produce NH3.

    Why not obtain it from pig poop (or equivalent waste) in that case?

    (* - NH3 production actually releases 3 CO2 molecules for every 4 NH3 molecules produced.)
     
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  7. ElectricFetus Sanity going, going, gone Valued Senior Member

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    I think the great advantage of CH4 is its cheap price thanks to fracking. Of course this Cheap CH4 comes with the cost of all the environmental damage cause by fracking, as well as that fracking CH4 from the ground to exhausts releases more green house gasses then burning coal by simple fact that methane leaking from fracking outdoes more efficient energy conversion of CH4 and then some.

    Ammonia as an energy storage system is nice in that if it was made for hydrogen and air its clean, less combustible then other fuels and easier to store then hydrogen gas, the problem is all the inefficiency in converting hydrogen to ammonia.

    I personally like metal fuels like Zinc or Magnesium: there recycling energy efficiency makes them competitive with hydrogen yet they are far easier to store, the only problem has been the limited amount of research in developing metal-air flow cells.
     
  8. SciGuy500 Registered Member

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    what if i want to drive at night
     
  9. SciGuy500 Registered Member

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    or drive long distances, usa is a big country
     
  10. billvon Valued Senior Member

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    Turn your lights on
     
  11. SciGuy500 Registered Member

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    wait a second, im thinking of solar-powered cars
     
  12. SciGuy500 Registered Member

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  13. ElectricFetus Sanity going, going, gone Valued Senior Member

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    Solar power cars would certainly get you across the USA: their range is technically infinite! The only problem is having to stop to let them charge up when batteries drained.
     
  14. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    An interesting angle to consider:
    Which is greater, the work done to compress CH4 to liquid state on hot summer day (say 35 C), or to convert CH4 into NH3? I'm no chemist, but as I recall the Haber process production of Nh3 is actually exothermic and that heat release is at high enough temperature to generate electric power, but as the Haber process requires even higher pressure than just making CH4 stay liquid on a hot summer day, so it is tough to call just by guessing - all by memory.

    Any Chemist reading willing to do the full analysis for deciding which wastes more energy to produce per mile of car driving down the road?

    Can NH3, via Haber's exothermic reaction make the electric power needed to compress more reactants into the reactor? Like the crushed sugar cane can make more, much more, heat than the distillation of alcohol requires- so much more heat that even after supplying distillation's thermal energy, about 5% of Brazil's electric power is produced with the excess heat. (if not 5% now, it soon will be when almost all distillation facilities have added the small steam-electic generators.)
     
  15. billvon Valued Senior Member

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    Hmm. Before we answer that a few notes:

    1) Almost no vehicles out there will use LNG outside of a few very demanding applications (like aircraft or spacecraft.) So 99% of the vehicles won't need to compress it to LNG. About the only common reason to do it nowadays that I know of is long distance transport; it takes less energy to liquefy methane, store it in big tanks and then transport it via ship than it would take to compress it into much larger tanks and then move the much bigger/heavier ship.

    2) Natural gas pipelines typically operate at about 500psi, which is a pressure that is easy to design pipelines to handle. A natural gas adsorber can store enough methane at those pressures to give you a decent range (200 miles or so in a reasonably sized tank) - thus no compression required.

    3) 99% of vehicles today use compressed natural gas, and per the NREL, it takes between 2% (good station compressor) and 5% (small home compressor) of the energy in natural gas to compress it to 3600psi. So if you fueled your car at home with 50 pounds of natural gas it would require 2.5 pounds of additional natural gas to run the compressor.
     
  16. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    that is true except for last four words. Yes compression is required, but not by the car owner or the filling station. Who does it does not enter into the question of which has more energy waste.

    Also that is why I posed the question "waste per mile driven down the road" I.e. that "natural gas adsorber" if the typical metals are used, may weigh more than the tank full of gasoline and you carry it around 100% of the time, not like gasoline tank that may average less than half full and it weighs less, even when full. As car get lighter an extra 200+ pounds to carry around 100% of the time, becomes more important in the waste energy analysis.
     
  17. billvon Valued Senior Member

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    That's a fair point, since natural gas when it comes out of the ground does so at pressures between 0-150psi, so you'll always need to compress it to send it off down the pipeline. (True of oil as well, although all the energy in moving oil comes from overcoming friction in the pipe rather than compressing anything.)
     
  18. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Yes but then the CH4, I think, would win the "Least energy wasted per mile driven down the road" contest. Now that CH4 is several times cheaper than it was less than a decade ago, no one will be using H2 to make NH3.

    Also I doubt it is economically feasible to avoid the loss of energy (waste) when 500 psi CH4 fills a pressure tank at 3600psi or even greater loss when it is mainly just absorved a little above atmospheric pressure. Answering my question is deceptively complex problem, I think
     
  19. KitemanSA Registered Senior Member

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    Today it is, but it need not be. Given sufficient cheap electricity like we can get from Liquid Fluoride Thorium Reactors, it would be quite easy to obtain both the N2 and the H2 from carbon free sources, air and water. These combine via several viable processes (my favored is SSAS - solid state ammonia synthesis) without carbon being involved.
     
  20. billvon Valued Senior Member

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    If we have the energy to spare it would best be put towards usage directly, via EV's. (In general using any form of energy directly is preferable to converting it to other forms.)

    However if we have reactors that can reach water thermal dissociation temperatures, then we have a ready source of hydrogen. From there it's fairly easy to make either NH3 or CH4 (via the Sabatier process) for usage as fuel.
     
  21. KitemanSA Registered Senior Member

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    If you want to get picky about the Waste down the road, you need to include the practically total waste of the solar energy that went via photosynthesis into making the CH4 in the first place.

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  22. KitemanSA Registered Senior Member

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    As may be but the sub discussion was NH3 vs CH4.
     
  23. ElectricFetus Sanity going, going, gone Valued Senior Member

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    Well if we burned Methane in a combine cycle power plant and charge electric cars on that we would get much further then burning it in a ICE power car directly.
     

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