Brett,

If you just charge a conductive liquid, you won't have a capacitor. You need two oppositely charged conductors. Can you perhaps explain your appliction a bit more?

Overcoming the friction experienced by the insulator balls and the fluid in the insulated pipe would expend far more energy than that which will arrive at the far end in the form of tiny amounts of electrical charge.

The liquid would leak around the ball because there is no seal. I can see where you would think a ball is a good idea because it would in theory act like a ball bearing and not have much friction. The problem is that a normal pipe isn't as smooth as you might think so the only way the ball can reduce friction is if the liquid acts as a lubricant but you don't want that because you are trying to use the ball as a separator. A piston might work but you would run into the same problem with the inside of the pipe not being smooth enough. As well as the piston adding a hugh amount of friction. I do like your idea about the ball though. I've been trying to come up with a way to separate nitrogen from an oil and a ball just might do the job.

Good luck and I hope you solve your problem.

I had considered an air table effect by having air seeping onto the pipe walls but couldn't understand whether the charge could therfore utilize the air to discharge; but if the air hole pipe was a intermittent capillary then the air bubbles could remain disconnected from the source.

I think it is a very good idea to separate the fluid with air gaps. It may polarize the air but still air will be like an insulator. Fluid should not be conducting type as wetting the walls will be a problem due to conduction.