A better Vandegraaf generator?

[Ivan Seeking]

I have never gotten serious about this but I remember thinking the idea seemed promising. I thought this might make for good discussion; if feasible maybe an interesting science fair or even an undergrad project if it gets that interesting. We actually played with this a bit many years ago and we did get some encouraging initial results using a very crude apparatus, but we never got back to it.

The basic idea is this: Use particulates in place of a moving belt. We used an impeller style fan and motor from a vacuum cleaner. In our first run I believe the fan was grounded. This was used to drive talcum powder through a closed system designed to transfer charge as does the belt in a normal VDG generator. Keeping in mind that it has been a long time, IIRC, and if I was thinking properly, the capacity to transfer charge increases dramatically due to the total surface area available in a dense particle stream.

The end effect would be a high power device, surely much more lethal than a normal VDG if it worked as I was thinking. I believe, at least in principle it appeared that that the surface area for charge transfer could be scaled up by orders of magnitude using particulates as compared to the belt transfer method, and given approximately the same size generator column. I assumed that the total power is limited by the size of the fan motor used, insulation issues, and the efficiency of the charge transfer to and from the dust. What actual losses one might find…I couldn’t be sure. AFAIK, this would be very difficult to calculate. Lossy, yes. Too lossy, I don’t know. I kept thinking that I can always use more power and more powder, and more collisions for charge transfer, to beat many problems. Does this offer the means to simply "watt your way" thought the issues [so to speak]. For example, if too many restrictions are placed in the system and they are impedeing the flow of the particulates, use multiple stage fans to increase the pressure. The prices is simply more power in.

Note that any combustible materials should be avoided. This could cause an explosion such as we see in grain chutes from time to time. Dust explosions are very, very dangerous! In fact someone I knew of in Portland just died in one a few years ago. Dust had gotten into a high voltage panel and it exploded when he opened the door. Anyway, we believed that talcum power was probably safe, but honestly, we didn’t know for sure.

What do you think, could it work?

 

[Integral]

For the last several years I worked with sand blasters, we used a fine (25micron) aluminum oxide "sand" and had long (3" to 6' ) polyurathane hoses, when conditions were right, we would see sparks from 6" to 2' long inside the hoses. I am not sure how to collect the charge but we sure were generating it!

 

[LENIN]

It sounds like a gut idea for a science fair. The VDG would probably get charged up faster than with a belt. But I don't thin'k you could get a stronger charge than with a belt. Becouse as far as I know the limet is the insulation of the dome of the VDG which is limited to a few MW when placed in nitroge (I am not schure doe).

 

[Ivan Seeking]

I think the maximum potential may be increased a bit since the amount of charge leaking off might be offset by the increased supply, but aside from the possibility of quickly replacing charge lost, thus kicking up the voltage a little, I think you are correct. The minimum radius of curvature found on the capacitor [charge accumulator] is a strong determining factor for of the upper voltage limit, as is the insulating column height and dielectric properties.

Also, it turns out that 8 -12" diameter stove pipe sections connected to form a square loop works reasonably well for the capacitor, as opposed to the more difficult globe or ellipsoid option. This may also be easier to incorporate with the particle stream idea suggested here.

Different types of particulates will make better or lesser carriers for excess charge. Also, I believe that most particulates have an affinity for either positive, or for negative charge. So, the choice of particulates used here may be a most important one; in addition to safety concerns of course.

 

[Ivan Seeking]

One thing that I didn't mention - maybe other people will know if this is true. A very high potential, high power, DC device is difficult to come by. I thought that there may even be industrial applications for this idea.

The idea is that much more power can be generated at the same voltage, and without using a belt the width of a house. Again though watch out! If this is correct this thing could easily become highly lethal!