Why is wireless electric current not possible?

August 8, 2004 6:42 AM

If we can have wireless voice communication and wireless data transfer, why can't we have wireless electric current?
posted by PrinceValium to science & nature (16 answers total)

we can...however, it takes a lot of energy, so they tend to use microwaves for it.
posted by taumeson at 6:45 AM on August 8, 2004

Proximity communications.
posted by bingo at 6:58 AM on August 8, 2004

Size of the transmission and reception components seems to be one of the big factors. There's a very interesting set of slides here (original in PowerPoint, Google HTML). The powerpoint slides have some mockups of the antennas. Kilometer diameters are blythely mentioned.

Interestingly, it looks like the Japanese are seriously trying to build a usable space-based microwave transmission system.
posted by bonehead at 7:30 AM on August 8, 2004

wireless electric current. Will remind you of some of the problems that inhere.
posted by jfuller at 7:44 AM on August 8, 2004

Interesting.. but what about short-range solutions? Could microwave technology be useful for airport hotspots, in-home networks, and schools? I'm thinking something that would transmit current from a grounded source to a receptor on your device, either continuously powering your machine or recharging your battery.
posted by PrinceValium at 8:03 AM on August 8, 2004

Sure, Prince V, so long as you don't kind getting cooked in the process.
posted by jaded at 8:29 AM on August 8, 2004

Wireless current is a transfer of energy. Would you like that as a focused beam, or as a general field?
posted by mischief at 9:32 AM on August 8, 2004

Current (as opposed to microwaves) needs to flow through a conductor. Air is great insulator and poor conductor. So wireless "current" is not practically possible. Energy can be sent via electromagnetic waves. Radio waves, such as in a wireless network, transmit energy and induce current in the antenna. The energy is pretty minimal. With shorter and more focused beams you can transmit more energy, but if you get in the way you may get cooked a burrito in a microwave oven.
posted by caddis at 9:44 AM on August 8, 2004

Well if there was a general field that didn't cause ill effects or interference with non-electric objects, and devices had receptors that could slowly capture the charge from the surrounding area, it might seem workable. I understand the concepts of lightning and burritomaking, but I figured that there could be some low-impact way to achieve this - or at least ideas on how energy transfer could be accomplished.
posted by PrinceValium at 10:35 AM on August 8, 2004

I'm sure Nikolai Tesla was doing this.
posted by scarabic at 11:55 AM on August 8, 2004

Sure you can. There are some technical problems like EM pollution. "Hey why doesn't my wifi network work anymore?!" A strong microwave transmission would interact with water and could hurt crops, animals, people, etc.

I believe its doable in many different ways, but good luck getting investors. Once you solve the transmission problems how are you going to control who gets to leech and who doesn't?

I would love to see little "energy zones" where you can put your cell phone, laptop, etc and let them recharge. A shielded area in an airport would probably get lots of use. Imagine a microwave (or some other freq) beam shooting down at some location with a laser pointed device so you can "see" where you might get burned, or at least where not to put the baby. Lay your phone/laptop there and watch the battery indicator rise.

Err, if you steal my idea I'll get you!
posted by skallas at 12:38 PM on August 8, 2004

It's not really interference with non-electric (organic) objects, it's a direct effect of having too much EM radiation in the area.

You need high energy fields for this to work, and organic tissues cannot tolerate high energy EM fields, it's not a side-effect type problem, it is more fundamental. Maybe a focused beam could work, or some new thing that wasn't EM, but that is too much physics for me.
posted by rhyax at 12:43 PM on August 8, 2004

Some of the links above mention that a choice frequency for power transmision is 2.4GHz. It works well---it's away from the water-resonant frequencies, so no cooking of the consumer occurs, but it's realtively easy to do cheaply (technology is well developed) and efficiently (in the ball park of 60%). However, it's also the one used by cordless (home) phones, hand radios and, most importantly, wifi (b and g flavours).
posted by bonehead at 12:44 PM on August 8, 2004

It's Sunday, I just woke up, and am too tired to google for this. Mainly because it'd involve wading through an ocean's worth of fringe weirdo geocities sites. :) But it'll whet your whistle so you can google. (Experts: Feel free to correct this, as it is apocryphal and just vaguely remembered.)

Tesla (among others) was indeed working on this, and supposedly had working models.

AFAIR, it wasn't the standard microwave beam recovered through inductance model, it involved some sort of mega tesla coil device, probably highly modified from your "standard" tesla coil, and some sort of trickery with "earth ground".

However, I can't even imagine what sort of complications this kind of scheme would create if it was applied on a large scale. It would probably interfere with radio transmissions something fierce, just for starters.

Keep in mind Tesla was also reportedly working on doomsday devices that utilized similar ideas. Namely pumping "earth ground" full of energy, weird ionospheric effects and more.

I Am Not an Electrical Engineer. But some of the tales surrounding tesla coils, especially the large and badly designed ones, are astounding. CRT and flourescent tubes exploding, power grids going out, etc.
posted by loquacious at 1:51 PM on August 8, 2004

Those darn wires @ Dan's Data.
posted by snarfodox at 3:37 AM on August 9, 2004

Some of the links above mention that a choice frequency for power transmision is 2.4GHz. It works well---it's away from the water-resonant frequencies, so no cooking of the consumer occurs

Most microwaves operate at 2.45GHz, so cooking will definitely happen. The Straight Dope says that they operate at this sub-optimal frequency so food can be cooked more evenly throughout.
posted by zsazsa at 6:25 AM on August 9, 2004