Wireless Extension Power Cord

[TTM77]

I was searching for extension power cord when I stumple on this.. oh wait, this have no cord. Excuse my 'stumple'. LOL

http://www.thinkgeek.com/stuff/41/wec.shtml

 

[TheoPetro]

i saw this and was pretty curious as to how exactly it works. it seems pretty inexpencive for an idea like that. if there wasnt some kind of huge problem with them then they would be used in many more diverse places than an extension cord. i guess im just pretty skeptical about them.

 

[keeleysam]

Add it to your cart.

 

[f95toli]

What is the power rating?
Transmisting power is easy, the problems starts when you want to transfer more than a few Watts. Not to mention transfer energy without losing most of it to heat in the process.
Moreover, IF that thing can transmitt more than a few watts it is probably illegal in most countries.

 

[Farmer]

It's a joke. Availability is "No suing."

Besides, people have been trying to use tesla coils for wireless transmission of current for about, well, I don't know, since Tesla himself.

 

[wellswarrior73]

this was a joke, and printed in CPU magazine. Heres a link about it

 

[FriedPixel]

wireless extension cord = very large tesla coil

 

[AgentJean]

Warning: Even though these microwaves are about as harmful as the leakage from an ordinary microwave oven (not much), do not put computers, televisions, other sensitive electrical equipment, food, liquids, paper, glass, flammable substances, magnets, or living things in between the base and satellite units. Just in case.

 

[ChAoTiCpInOy]

That was an April Fool's Joke. I can't believe your actually thinking about it and trying to decide wat it can do. Wow, I can't believe it still works even after all this time.

 

[TTM77]

I thought there were something fishy. But didn't have the time to fully check it out.

Now it could be possible if there is a huge lazer to shoot all those power to the other side, and get collected by something similar to a solar panel on the other side.

 

[BrunoPuntzJones]

Originally posted by: ChAoTiCpInOy
That was an April Fool's Joke. I can't believe your actually thinking about it and trying to decide wat it can do. Wow, I can't believe it still works even after all this time.

I know, I had to do a double take to make sure this was HT.

 

[Jeff7]

Originally posted by: f95toli
What is the power rating?
Transmisting power is easy, the problems starts when you want to transfer more than a few Watts. Not to mention transfer energy without losing most of it to heat in the process.
Moreover, IF that thing can transmitt more than a few watts it is probably illegal in most countries.

Then it might count as a "directed energy weapon" which would probably not be readily available at online retailers.

 

[f95toli]

True. However, there is nothing wrong with the principle and it might be safe enough if you limit the power to say 0.1W, this might still be enough to e.g. turn on a LED and might be a fun technology demonstrator. This is what I had in mind.

Now, this HAS been seriously considered on a larger scale. I know there have been a few studies where they have been looking at beaming power to/from satellites using microwaves. One very futuristic idea would be to have huge solar panels in orbit and then beam the energy down to large recivers. However, once again safety is an issue; if the antennas are misaligned you might end up frying something which is generally speaking not good.
The other way (earth->satellite) might be a useful method to e.g. charge batteries of satellites and safety is less of an issue. However, AFAIK this has never been demonstrated.

 

[Jeff7]

Originally posted by: f95toli
True. However, there is nothing wrong with the principle and it might be safe enough if you limit the power to say 0.1W, this might still be enough to e.g. turn on a LED and might be a fun technology demonstrator. This is what I had in mind.

Now, this HAS been seriously considered on a larger scale. I know there have been a few studies where they have been looking at beaming power to/from satellites using microwaves. One very futuristic idea would be to have huge solar panels in orbit and then beam the energy down to large recivers. However, once again safety is an issue; if the antennas are misaligned you might end up frying something which is generally speaking not good.
The other way (earth->satellite) might be a useful method to e.g. charge batteries of satellites and safety is less of an issue. However, AFAIK this has never been demonstrated.

And there are questions as to the effects of a powerful microwave beam piercing the upper atmosphere continuously.

Suddenly, the thought came to me too: birds. Just got one flying along, and suddenly it's incinerated.

 

[Talcite]

sorta off topic... but how do those electric toothbrushes charge? there's no contacts between the base and the toothbrush.

 

[Aluvus]

Originally posted by: Talcite
sorta off topic... but how do those electric toothbrushes charge? there's no contacts between the base and the toothbrush.

Inductance. They are essentially an air-core transformer IIRC.

 

[soydios]

Originally posted by: f95toli
Now, this HAS been seriously considered on a larger scale. I know there have been a few studies where they have been looking at beaming power to/from satellites using microwaves. One very futuristic idea would be to have huge solar panels in orbit and then beam the energy down to large recivers. However, once again safety is an issue; if the antennas are misaligned you might end up frying something which is generally speaking not good.

I remember something like that from SimCity 3000. I think that idea will remain in the realm of video game fantasy.

Originally posted by: f95toli
The other way (earth->satellite) might be a useful method to e.g. charge batteries of satellites and safety is less of an issue. However, AFAIK this has never been demonstrated.

Microwaves directed at a satellite would also fry its electronics. Try putting a CD in the microwave. Or fly a plane too close to an Aegis missile cruiser putting out full power on the main radar panels. Same thing happens in both circumstances: it sizzles.

 

[f95toli]

I think I actually read about it in New Scientist (or a similar magazine) a few years ago, but now when you mention it I also remeber seeing it in Sim City.
It might be futurustic. However, solar panels in space is a nice idea. You can make HUGE panels without problem (especially if you use a flexible panel which you can simply "inflate", then you only need to balance out the radiation pressure) and since there is no atmosphere the energy density is somewhat higher than on the ground. BUT, you need some way to get the energy back to earth.

About microwaves: I don't think you would neccesarily fry the satellite. If you use a relatively high frequency (say 20 GHz) it is quite easy to shield the electronics (after all it is much easier to shield out 20 GHz than e.g, 20 MHz, some kitchen foill would be enough).
That said, it would still be a very inefficent way to transfer energy but in some applications it might be worth it.

 

[silverpig]

There is some interesting research going on in wireless power transmission. I'm working on a project now which relies heavily on sending power via a beam and converting it to electricity.

This is the competition I'm involved in.

In doing research for this, we found that there was a successful flight of a remotely powered airplane using a microwave beam and a rectenna.

 

[silverpig]

Originally posted by: f95toli
I think I actually read about it in New Scientist (or a similar magazine) a few years ago, but now when you mention it I also remeber seeing it in Sim City.
It might be futurustic. However, solar panels in space is a nice idea. You can make HUGE panels without problem (especially if you use a flexible panel which you can simply "inflate", then you only need to balance out the radiation pressure) and since there is no atmosphere the energy density is somewhat higher than on the ground. BUT, you need some way to get the energy back to earth.

About microwaves: I don't think you would neccesarily fry the satellite. If you use a relatively high frequency (say 20 GHz) it is quite easy to shield the electronics (after all it is much easier to shield out 20 GHz than e.g, 20 MHz, some kitchen foill would be enough).
That said, it would still be a very inefficent way to transfer energy but in some applications it might be worth it.

Apparently some rectennas are up to 90% efficient in microwave->electricity conversion...

 

[YahoKa]

The problem with transmitting on the electromagnetic specturm is the combination of these two things: it carries energy in the wave/photons, and waves diffract (en.wikipedia.org/wiki/Huygens-Fresnel_principle)... thus you capture a fraction of what you sent. You could have almost perfectly efficient wireless transmission with a magnetic field (capture flux), but then you need really, REALLY big magnets, and you get rather obvious problems with that.

 

[f95toli]

I don't that is the biggest problem. You can create very narrow microwave beams if you know what you are doing. If the frequency is hight enough you can actually use a system of lenses (made from teflon) to shape the beam.

 

[YahoKa]

I'm not up on my quantum physics, but bascially isn't it impossible to focus it in a direct line? That is, won't the wave propagate in every direction anyways?

 

[theslickvik]

this is too funnay!

 

[Born2bwire]

Originally posted by: YahoKa
I'm not up on my quantum physics, but bascially isn't it impossible to focus it in a direct line? That is, won't the wave propagate in every direction anyways?

Microwave frequencies can be satisfactorily described using classical EM. But still, the fact that we can direct a laser into a coherent beam line is proof positive that we can direct a microwave into a beam line. More specific examples of this with antennas would be simple dipole arrays or parabolic dish antennas. If you want to talk about the Quantum EM physics, then you can get something along what you are talking about. In the Terahertz range and visible light where we have lazers, the light can be described as a Gaussian Beam using the paraxial wave equation. Now, even in free space the Guassian beam will spread out, however, you could use lenses to refocus and compensate for the spreading of the beam. But again, this is in a frequency range that is above what is being discussed.

The problem with transmitting on the electromagnetic specturm is the combination of these two things: it carries energy in the wave/photons, and waves diffract (en.wikipedia.org/wiki/Huygens-Fresnel_principle)... thus you capture a fraction of what you sent. You could have almost perfectly efficient wireless transmission with a magnetic field (capture flux), but then you need really, REALLY big magnets, and you get rather obvious problems with that.

Diffraction is not a very big problem unless you want to start transmitting through thick dielectrics (which really aren't something you find in everyday environments). The efficiency of power transmission is really going to lie in the efficiency of the receiving and transmitting antennas and your ability to focus the radiation pattern. These are really just engineering problems and a classic real world example is a crystal radio. A crystal radio derives all its power from the received signal. Still, I do not think that it is really a viable means of transmitting power. But as we are able to generate low power electronics, we are seeing some systems that are powered via radio transmissions. For example, RFID's work by retransmitting the power it receives from the transmitter.