Hi. I would like to build an electrostatic precipitator. I have a bug zapper, and was wondering if I could just hook the leads from that to 2 large plates, and put that in front of some grounded collector plates and a fan. I can't tell what voltage the bug zapper is using, but in general, do bug zappers put out enough to ionize the dust coming through? Its a zapper 40W bulb model btw, if anyone knows how much voltage it creates.
Also, the mesh of the zapper gave me an idea-could I just straighten out the 2 screens, and flow the air perpendicular to them? Or would the dust lose its charge after passing the second plates? Any advice or suggestions are appreciated.
Hi Adam. A typical bug zapper probably puts out between 5 and 15kV. A typical air ionizer works at around 7.5kV, so at first glance this looks possible. But, there are gotchas:
In electrostatic air precipitation, you want DC voltage, not AC. So on the outputs of your zapper, you'll need two 15kV-rated diodes. Once you have a high DC voltage, you want the negative lead to be the "emitter" and the positive lead to be the "collector." Electrons flow from the negative to positive terminals so this is why it's not the other way around. The emitter should be a fine wire - the smaller the diameter and longer, the more readily ions will jump off it and into the air. Take a long length of this wire and form a "grid" out of it. This puts "negative ions" into the air. (Be careful not to zap yourself, DC is very dangerous.)
As for the collector, you want a large surface area with no little to no sharp points - the opposite of the emitter. Rounded sheets of metal work well, like an oval shape. Flat metal sheet might work also, as will a (fine mesh) screen. A course-mesh screen would probably not work all that well.
Ions in the air are negatively charged. Most of these are strongly attracted to the positive plate and "dissappear." Sometimes the negative ions intercept a conaminant, and change its charge state. The positive plate is still strong enough to attract this ion, and thus the contaminant also. The end result is the positive plates get covered with gunk from the air.
Mark, thank you. I really appreciate your help. I went to home depot today and got the metal wires and sheets, but now I realize I have no idea which lead is positive and which is negative. I took the housing apart, and the transformer has no markings indicating anything, and both output leads are red. Is there any way I can test it to determine which lead is which?
I had an odd thought. Any ideas about building an electrostatic precipitator that would fit somewhere between the manifold and the exhaust pipe of an automobile? I've seen some cars burning enough oil to be visible and I was wondering if there might be a way to cut that down substantially, and at a fraction of the cost of tearing the engine down and replacing all the rings, turning large volumes of air pollution into smaller volumes of solid waste pollution.
Even a demonstration of feasibility would be interesting to try. But building something that can stand up to the abusive environment of the underside of a car seems like a daunting challenge.
For those in the U.S. who might recognize it, maybe the... Ronco muffler cleaner :) For those of you who do not recognize this, Ronco is a company in the U.S. that sells some of the more questionable inventions to consumers.
Well, to take one position, all the current emission control hardware and computer controlled compensation built into the recent cars seems like it isn't all that wildly different from what I'm suggesting here. I'm told an engine can be pretty far down the hill before the software just can't compensate for it anymore and you discover the problem.
On the other hand, the adjacent state has high license fees, based on the value of the car. I think I see a larger number of old beaters over the border.
It is easy to say what somebody else should do. But how many of those folks are going to pay a price equal to the majority of the current value of a car to get someone to tear an engine down to the ground and rebuild it? I question how much of car repair is cost justified.
I know someone who sank $1200 into getting her transmission worked on, when to be really brutally honest, the car probably wouldn't sell for that, either before the problem was discovered or after the work was done. It was her decision but I suspect that after it was over she probably regretted it just about as much as buying something else.
I suppose we could tell them that they really should do is go buy themselves new $48,000 car to fix the problem. This wouldn't be a problem when we all thought we were going to make more money every year off to infinity and we believed there would be no end to new cars. But as more and more sail off towards being part-time minimum wage, no-benefit employees I wonder where this is going to go. I fully admit that more and more are giving up maintenance to cover other bills.
I've been thinking about how this could be built to make operation dependable and maintenance feasible.
Another consideration is the major pollutants emitted by the engine. CO2 is probably the single largest emission (aside from heat) and electrostatics aren't going to touch it. If the exhaust gasses could be cooled to -98°F then the CO2 would precipitate out as "snow" - but even then, there is no place cold enough to store it for any period of time. The best solution might be to reformulate it into something else.
I'm not sure if simple hydrocarbons and nitrous oxides are heavy enough to be precipitated electrostatically. If this were the case, wouldn't electrostatic emissions controls already be in place?
-- "I can conceptualize what infinity is, but I cannot imagine it." MCJ 200406
I was limiting myself to particulates. For CO2, turning it into limestone is probably the best solution, but I wasn't considering that.
I was only considering particulate carbon/hydrocarbon. Gasses like hydrocarbons and nitrous oxides wouldn't be touched by electrostatics, unless they might perhaps be easily charged. And I didn't even realize there were electrostatic emissions controls already in place.
Thanks for the info. Are you sure that the precipitator would need to use DC current? I read that a corona happens more easily on AC current, that leads me to beleive that an AC current across the mesh screens would more easily charge any particles. I'm not concerned with directing the flow of the dust, I figure the fan behind the screens will be strong enough to keep things moving through the screens and toward the target plates.
I've built the system, it consists of a box with two parallel screens across the opening to the box, then several perpendicular copper plates that I've connected to house ground, then a bathroom ceiling fan which exhausts outside the box. I've ordered some diodes, but I was just wondering if I can hook the power supply up directly, right now, and if it would work.
Also, does anyone have any ideas on how to test this, to see if it really is capturing dust and any other airborne particles?
I know commercial precipitators use DC, I was just wondering if it would work with AC current. According to the ionic breeze patent, it uses pulsed DC in order to move the air without a fan. I'm using a fan, so I was wondering if I could just run AC current between the screens, and if that would be able to create a strong enough field to charge the dust particles flying between them.
"Real" pricipitators use pulsed DC; at voltages quite a bit beyond what the airgap will hold - one continuously measures the Corona-current to detect how long the voltage can be left on before there is a flashover and step the pulse with back a bit. The current rises exponentially 1-2 usec before flashover.
Usually it's an single-SCR resonant design where the resonant frequency is tweaked to adjust the pulse width and the trigger frequency is fixed, at about 1/3 of the resonance frequency - low enough to make the pulses discrete and to extinguish any flashover paths from the previous pulse..
I tested an air ionizer by putting it a clear plastic pitcher, blowing out a matches to make smoke in it, and shining a laser pointer through it. Sure enough, when I plugged the air ionizer in, the smoke in the pitcher became turbulent and started to clear up.
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