Christopher Tidy wrote:

https://en.wikipedia.org/wiki/Kelvin_water_dropper

Interesting. It relies on flow in droplets, though, doesn't it? It's hard
to make droplets go upwards. Single air bubbles which bridge a narrow
pipe, with short regions of oil in between, might work, but I think the
implementation and adjustment would be difficult.

Thanks to everyone for the ideas.

Chris
Well, I think there might be a way to make it work with pumped oil. But, as
I mentioned before, charge is usually stored on SURFACES. So, if you mixed
air with the oil, so it was a stream of bubbles in the oil, that might
enable it to carry charge. You could use metal screens that the oil/air mix
flowed through to inject/extract the charge.

Jon