Could we use flowing air as a capacitor dielectric?

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Discussion Overview

The discussion revolves around the feasibility of using flowing air as a dielectric material for capacitors, particularly in the context of energy storage for aircraft. Participants explore the theoretical implications, practical challenges, and historical examples of capacitors utilizing air as a dielectric.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Bob Clark proposes using flowing air as a dielectric for capacitors in aircraft, suggesting that it could eliminate the weight of a traditional dielectric while maintaining capacitance as long as air density remains constant.
  • Bob Clark questions whether the flowing air would cause the capacitor to discharge and if the leakage would be unacceptably high.
  • Another participant mentions the existence of open-air capacitors used in old radios, suggesting that while air can be a dielectric, flowing air may not maintain the necessary dielectric constant for effective capacitor function.
  • Warren expresses skepticism about the energy storage potential of such a system, labeling it as an "incredibly tiny" energy source.
  • Bob Clark acknowledges a significant error in his earlier calculations regarding energy storage potential, admitting that he omitted a critical factor, which drastically inflated his estimates.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the viability of using flowing air as a dielectric, with some expressing skepticism about its effectiveness while others explore the concept further. The discussion remains unresolved, with no consensus on the practicality or efficiency of the proposed idea.

Contextual Notes

Bob Clark's calculations were noted to be flawed due to missing a key factor, which raises questions about the reliability of the energy storage estimates discussed. The implications of air density and flow on dielectric properties remain uncertain.

RGClark
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I wanted to use air as the dielectric for a capacitor for energy storage for aircraft. My thinking was that we could charge the capacitor on the ground and leave the capicitor open to the flowing air in flight. As long as the density of the flowing air remained the same, the capacitance would stay the same.
Capacitors usually don't offer significant advantages over chemical batteries per weight because you have to consider the weight of the dielectric that must be carried along. This is true even when the dielectric is air that is enclosed and must be carried along. But I thought an open air dielectric wouldn't have this problem as you're just using the surrounding air as the dielectric.
The question is would the flowing air cause the capacitor to discharge?
Would the leakage be unacceptably high in this case?


- Bob Clark
 
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There are open-air capacitors. Old-style radios used a set of aluminum(I think) plates that would variably mesh in between a set of non-moving plates, with ambient air as the dielectric.
At the time, I think they were called "variable capacitors" and are probably still available today.

But, I don't think that "flowing air" would work well, if at all, because the flowing air would not retain a dielectric constant necessary for a capacitor to work properly But that's just my quess.
 
It'd be an incredibly tiny (read: insignificant) energy source.

- Warren
 
chroot said:
It'd be an incredibly tiny (read: insignificant) energy source.

- Warren


Yeah, you're right. I did a rough calculation that led me to believe I could store significant energy in an air capacitor if the plates and distance between them were at the ten's of meters scale.
Unfortunately I left out the factor 8.85 x 10 ^-12 out of the calculation for capacitance. So my calculation was nearly 10^11 too big!


- Bob Clark :redface:
 

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