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Normally water molecules are electrically neutral. But I have seen somewhere ideas about electric energy generators mentioning that water droplets might be used in some applications as they are charged particles.

Is it really so?

I know that water droplets get charged due to friction in the bottoms of waterfalls producing static discharges. But is there some other more fundamental process which makes evaporated or sprayed water droplets become charged?

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clouds? en.wikipedia.org/wiki/Lightning –  anna v Apr 9 '13 at 14:12
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I believe that the charge of clouds is also explained by triboelectric effect. I've found a video where the general description of the process is given: youtube.com/watch?v=tqksCHWROBU It is clear that they are referring to some different way of obtaining charged water droplets. Sounds like just evaporating the water makes it ionized. –  BartoNaz Apr 9 '13 at 15:36
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up vote 2 down vote accepted

I believe that evaporative ionization is the opposite effect of what you're looking for, per the general discussion on ion processes in evaporated droplets.

This constrains the range of charge-transfer in droplets to the triboelectric effect, as you mentioned.

The Kelvin Generator, including discussion about charge formation that exceed models, may be more than triboelectric, due to ground effects - which is to say that charge may come from other sources that the system of droplet and atmosphere. The only way I could see a Kelvin Generator involve Electrospray Ionization is through corrosion or dissolving of the conductive cups that collect the water.

The AmSci group suggests that the charge arrives from slowing the water droplets' fall. Their model could align with the idea that ion-transfer from droplet to system occurs via Coulomb Fission.

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+ I think your mention of the Kelvin water dropper is right on target. –  Mike Dunlavey Apr 10 '13 at 2:53
    
@MikeDunlavey The Kelvin demo is good, but the underlying model is yet unclear. Coulomb Fission could lead to ion-transfer, but it may not be enough to speak to the streak-photos showing droplets flying upwards, in a field-pattern. This effect is important in the answer. –  New Alexandria Apr 10 '13 at 5:06
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