Fighting Fires With Beams of Electricity

cylonlover writes "It's certainly an established fact that electricity can cause fires, but a group of Harvard scientists have presented their research on the use of electricity for fighting fires. In a presentation at the 241st National Meeting & Exposition of the American Chemical Society, Dr. Ludovico Cademartiri told of how they used a unique device to shoot beams of electricity at an open flame over one foot tall. Almost immediately, he said, the flame was extinguished. 'Such a device could be used, for instance, to make a path for firefighters to enter a fire or create an escape path for people to exit, he said. The system shows particular promise for fighting fires in enclosed quarters, such as armored trucks, planes, and submarines.'"

Comments

"beams of electricity"?

[oldhack]

Like streams of electrons or ions?

Re:"beams of electricity"?

[c0lo]

Like streams of electrons or ions?

No, positrons baby! Using those definitely has certain... fringe benefits.

FTFY

Anyone have any idea how it works?

[IICV]

Anyone have any idea how this thing actually works?

The best I could come up with is based on a very small part of the article:

But how does it work? Cademartiri acknowledged that the phenomenon is complex with several effects occurring simultaneously. Among these effects, it appears that carbon particles, or soot, generated in the flame are key for its response to electric fields. Soot particles can easily become charged. The charged particles respond to the electric field, affecting the stability of flames, he said.

So I guess what happens is that the electrical field charges the soot and other light carbony things generated in the fire, which causes them to disperse sort of like what happens with this toy? How does that help extinguish the fire, though? Wouldn't the outward motion of the carbon particulates just bring in more oxygen?

What other effects are going on?

Re:Anyone have any idea how it works?

[Penguinshit]

Perhaps the dispersion of the combustible particles disrupts the fuel/air mixture and halts combustion? It's a stretch but I guess possible. From what I learned in Hazmat class some years ago, you extinguish fire by depriving it of one of the following: Heat, Oxygen, or Fuel. Every extinguishing material does one or more.

REALLY want video!

[wisebabo]

If there's a story that is crying out for some audio-visual documentation, this had got to be it!

I mean electricity and fire (and maybe they use a laser to create an ionized channel for the electricity to go through).

Re:Magnesium

[ThunderBird89]

Let's see them take on a metal-fluoride fire! For those, I've always recommended a good pair of running shoes.

Some idea

[dackroyd]

Flames are ionised (i.e. charged) particles. If you have a strong enough electric field (which is really not the same as 'shooting electricity' as per the article) when the charged particles move through the electric field there will be a force on them perpendicular to their motion and to the field i.e. the flame will curve over into spiral.

If you could get this to happen on a large enough scale, the flame would suppress itself as instead of the flame moving away from the fuel it would hang around - stopping oxygen from reaching the fuel.

If this all sounds really unlikely, that's because it is. Here it a video showing an electric field affecting a small candle:

http://www.youtube.com/watch?v=6fKGeV4NrrA&feature=mfu_in_order&list=UL

It looks like you need an electric field on the order of 10keV per 5cm to get this effect. So if you wanted to do it on a fire that was say 5 meters across you'd need an electric field in the order of 1MV which while obtainable is not exactly an easy thing to setup - particularly when there's a fire going on.

Re:Some idea

[Prune]

Yet another poster that didn't bother to do an iota of research beyond the article. They use oscillating fields which separate the flame from the fuel and used no more than 40 kV (that's makes for a rather small current at 600 W): http://cosmiclog.msnbc.msn.com/_news/2011/03/28/6362578-fight-fire-with-a-magic-wand

Re:Firefighters are usually wet.

[Doc Ruby]

Except if firefighters use electricity instead of water to extinguish the flames, they won't be wet. Fire trucks seem like good places to keep a large mobile battery, or a capacitor for recharging from power lines nearby the disconnected building, or a transformer while the building is disconnected. Or maybe buildings will have fire suppression power equipment installed that uses this electric effect.

The point is that electricity replaces water, so they don't have to mix.

Electric and magnetic field confused

[PeterM from Berkeley]

Sir,

    You have electric and magnetic fields confused with each other. If you have a MAGNETIC FIELD, when charged particles move across (NOT along) it, there is a force on them perpendicular to their motion (and to the field, incidentally).

    In an electric field, the force on the charged particle depends on the orientation of the electric field, not on the orientation of the charged particle's momentum.

    I refer you to the Lorentz equation, which goes like this:
F = q (E + V cross B)
where capital letters denote vector quantities and "cross" is the cross-product operator. As you can see, the force from the electric field (q times E) is parallel to E. The force from the magnetic field (q V cross B) is perpendicular to both the magnetic field and the particle's velocity.

    I'm not sure whether the rest of your explanation holds water--when you have a rapidly changing electric field it is accompanied by a magnetic field, which WILL curve particles like you say. In fact, when you have both, you have what is called an "E cross B" drift, in which charged particles have a motion perpendicular to both the E and the B field. (Is that what you meant?)

And yes, IAAP.

--PeterM