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Limitations to the practical use of atmospheric electricity?

  1. Nov 5, 2012 #1
    "In fine weather, the electric potential increases with altitude at about 30 volts per foot (100 V/m)................."

    what hinders its practical application as a source of power, as a battery?
     
  2. jcsd
  3. Nov 5, 2012 #2
    what are you quoting?
     
  4. Nov 5, 2012 #3

    berkeman

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    Staff: Mentor

    Most likely it is the very high source impedance associated with the resistivity of air. Even if you put a metal plate on the valley floor with the resistive load, and ran a cable to a plate on the top of a nearby mountain, the current has to flow through the air to complete the circuit.

    I Googled his quote, and it looks like Wikipedia is the origin:

    http://en.wikipedia.org/wiki/Atmospheric_electricity
     
  5. Nov 6, 2012 #4

    K^2

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    Science Advisor

    Because to generate electricity you need two things. You need a voltage differential and excess charge that can flow across that differential. Battery continuously provides you with excess electrons on the -ve pole. That's what gives you the voltage differential to begin with. Simply having a constant field around you does not allow you to construct a closed circuit where electricity is consistently pushed one way around the circuit.

    Of course, there is some amount of charge responsible for the above voltage differential, but it's static electricity, so the quantity of that charge is small. You can estimate it as a parallel plate capacitor.

    [tex]C = \epsilon_0 \frac{A}{d} = \frac{q}{V}[/tex]

    So if we are looking at d=10km, you only have 8.9x10-6C/m². That gives you 8.9 J/m² of energy, and once used up, it will take some time to regenerate. In contrast, solar power provides you with up to 1000 J/m² every second without having to build an antenna that's many kilometers high.
     
  6. Nov 6, 2012 #5

    Bobbywhy

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    Gold Member

    This is from “The Lightning Discharge” by Martin A. Uman, Dover Publications, 2001, pages 29-30:

    “Thunderstorms and lightning play a role in maintaining the fine-weather electric field, about 100V/m pointing downward, that is due to the negative charge on the earth and the positive space charge in the atmosphere (e.g., Israel, 1971; Pierce, 1974). A drawing showing how such a balance might occur is found in Fig. 1.18. The electrical conductivity of the atmosphere increases with height. The atmosphere is a good conductor to slowly varying signals at about 50 km, a level known as the electrosphere. The value of conductivity necessary to reflect radio waves occurs somewhat higher, in the region known as the ionosphere. The voltage between the Earth and the electrosphere in regions of fair weather is about 300,000 V. To maintain this voltage the earth has about 10º C of negative charge on its surface, an equal positive charge being distributed throughout the atmosphere. In regions of fine weather, atmospheric currents of the order of 1000 A are continuously depleting this charge. The charge is apparently replaced by the action of thunderstorms including lightning. The thunderstorm system acts as a type of battery to keep the fine weather system charged.”

    Seems to me the OP should propose how to harvest some of this energy.

    Cheers,
    Bobbywhy
     
    Last edited: Nov 6, 2012
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