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View Diary: The edible battery that's too good for electric cars (222 comments)

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  •  Uhhh ... maybe not ... (3+ / 0-)
    Recommended by:
    WarrenS, CTPatriot, jcrit

    The physical size issue, yes, I can see that. That's because a Na cell only generates 0.8V, so you need to stack 15 cells for a 12V battery, vs. 6 cells of 2V in lead-acid.

    But is physical size really a huge issue with a car? Especially an American car? You're talking 2000 liters (2 cubic meters) for a typical 50 KwH automobile. So it's a managable number, if the car is designed with that in mind.

    Regarding energy on a per-weight basis, Na is a bit worse that lithium, but lead is far, far worse than either one. Aqueous sodium isn't much more dense than water, either.

    We are all in the same boat on a stormy sea, and we owe each other a terrible loyalty. -- G.K. Chesterton

    by Keith Pickering on Sat Nov 12, 2011 at 10:24:54 AM PST

    [ Parent ]

    •  Size may not be a killer, but it'll maim (10+ / 0-)

      2 cubic metres = 2000 litres = 70.63 cubic feet

      I grabbed specs for a 2011 Hyundai Elantra out of thin air:

      Trunk capacity = 14.8 cu ft.
      Total interior volume = 110.4 cu ft.

      Presume the engine compartment is twice the size of the trunk, knock off 20% for things you'd need even with battery power, and you get 23.68 cu ft.

      So if the engine compartment and trunk space were completely used for the battery, you'd still need to find

      70.63-(23.68+14.8) = 32.15 cu ft

      of additional space out of the interior, leaving you

      110.4 - 32.15 = 78.25 cu ft

      or driver, passenger(s) & cargo. That's essentially the front seat plus a trunk. (Presuming the trunk space isn't counted in the interior volume; if it is, subtract  another 14.8 to leave 63.45 cu ft.--IOW, the front seat.)

      So if you wanted to build a car with aqueous sodium batteries that would have the carrying capacity of a smart car, it would end up the size of a 2011 Elantra. (Presumably you'd design the silhouette like a Chrysler PT Cruiser, with the battery in the rear, the passenger compartment shifted forward, & trunk in the front like an old Beetle. You'd probably have to make a rear-view video camera standard too...)

      So if you don't mind a vehicle the size of an Elantra or PT Cruiser that can only carry 2 people & maybe have a reasonable-sized trunk, then there's no a priori reason you couldn't use aqueous sodium batteries to power it. Unless there's another gotcha lurking in the ground clutter.

      snarcolepsy, n: a condition in which the sufferer responds to any comment with a smartass comeback.

      by Uncle Cosmo on Sat Nov 12, 2011 at 11:53:56 AM PST

      [ Parent ]

      •  Sure, because (4+ / 0-)
        Recommended by:
        Uncle Cosmo, Larsstephens, jcrit, Losty

        a Honda Civic is designed with a particular sized engine in mind, and a particular sized gas tank in mind.
        Would you drive a car that's twice as big as a Honda Civic if it cost you 5 cents a mile to run? Of course you would. It would be bigger, but cheaper by far than gasoline. And that's not even counting the environmental benefit.

        We are all in the same boat on a stormy sea, and we owe each other a terrible loyalty. -- G.K. Chesterton

        by Keith Pickering on Sat Nov 12, 2011 at 12:43:41 PM PST

        [ Parent ]

    •  The Whrs/Kg estimate just doesn't hold up (5+ / 0-)

      Take the example of 2000 liters.  Even if the batteries were only as dense as water (and I'm sure they're more dense than that, given the electrodes and packaging), 2000 liters of water weighs 2000 Kg!  That's 4400 lbs, just for the batteries.  Game over.

      But I'm glad you brought this story to my attention, because it's still great news.  As much as the world needs an inexpensive, high-performance battery for automobile usage, it may actually need fixed energy storage at power plants (or better yet, disbursed around the grid) even more, to eliminate probably the last legitimate technical/economic argument against solar and wind power.

    •  2000 liters of water weighs 2.2 tons. (2+ / 0-)
      Recommended by:
      Hayate Yagami, jcrit

      You won't be hauling that around in a Prius sized vehicle.

    •  keep track of the power not the voltage (1+ / 0-)
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      doesn't matter that you have to stack more cells to get the desired voltage.  it's power density that counts.

      doesn't matter if it's 10V or 12V, it's watt-hrs/m^3 and watt-hrs/kg that matter.

      whether you get to that power using 12V or 14V is not so important while keeping this caveat in mind: higher voltage is better.  lower voltage for the same power means more current so your I^R loss goes up.

      Realistically an electric car uses more like 70V not 12V for precisely that reason.

      big badda boom : GRB 080913

      by squarewheel on Sat Nov 12, 2011 at 09:53:25 PM PST

      [ Parent ]

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