Can power be transmitted?

[sram]

Can we transmitt power efficiently? Meaning(for example) if I have a light bulb, is there a way I can light it from a power source that is not connected to it through wires?

 

[Hero999]

Yes but it isn't save, it involves high levels of RF radiation.

 

[justDIY]

sure it's possible. is it efficient? generally no.

go to the library and get books by / about Nikola Tesla and learn about the work he accomplished nearly 100 years ago

 

[Nigel Goodwin]

sure it's possible. is it efficient? generally no.

go to the library and get books by / about Nikola Tesla and learn about the work he accomplished nearly 100 years ago

Step over the dead sheep on the way or is that being a little cruel?.

 

[Papabravo]

After spending billions on directed energy weapons in the 1980's as part of the strategic defense initiative or 'Star Wars', the defense establishment decided instead to bet on "smart rocks" and "brilliant pebbles".

They just could not direct sufficient power from an orbiting platform to all the ICBMs, estimated at 6-10 thousand in a Soviet first strike, to destroy them almost surely.

The problem is keeping energy focused in a narrow beam. It wants to spread out as it travels. So if you start with 100,000 watts you may end up with 100 microwatts at the load. That's only 90 dB path loss; not very impressive when you consider copper wire as the alternative.

 

[justDIY]

another thing to consider, since the OP didn't specify how much distance was involved.

OSRAM Sylvania makes a bulb and ballast kit called the ICETron which is a magnetic induction bulb ... the ballast output coils clamp around sections of the bulb, and power is trasmitted, wirelessly, into the bulb.

I believe it was originally designed for wet / hazardous / inaccessable enviromental applications where exposed metal contacts might get destroyed in short order and/or servicing the bulb due to electrode burn-out would be very costly.

 

[phalanx]

You will be hard pressed to remotely light a lightbulb from any appreciable distance. Another possibility would be to use the RFID approach of using magnetic induction to power the pass cards. You will not get much power but it is enough to power a very simple microcontroller based circuit. Microchip has RFID application notes available on their website that details antenna design and range in addition to several other factors that need to be considered. It is a good read if you have the time.

**broken link removed**

 

[The Mad Professor]

Here's a nice link for a brief history in the field of microwave power transmission ...
**broken link removed**

 

[dknguyen]

Passive Power

RFID tags are the only passively powered devices I have ever heard of (although they are working on medical chip devices that are passively powered). They use electromagnetic induction to power them...I think that's so cool.

But other than that, the only other way is to shoot lightning bolts to your light bulb...which is dangerous to say the least. Well I guess an appropriate solar panel and a super laser beamed at it would work...wouldnt be efficient though. That's still in the realm of sci-fi right now. Why won't batteries work?

 

[Hero999]

Build a flyback transormer with an output of >10kV, hold a fluorescent tube near it and see what happens. . .

 

[Russlk]

When I was an instructor in basic electronics, one of my demos was a transmitter (two #10 tubes in push-pull) connected to a dipole antenna. The "receiver" was a dipole antenna with a small lamp. The lamp could be lighted for about 20 feet.

 

[Oznog]

Don't look to the Tesla books for real information. The truth is his wireless power experiments were not well documented in a technical sense. A lot of wild claims were made at the time. We do understand the capacity for broadcasting power the exact way he wanted to do it (no magic here) and know the whole idea is impractical, and the stories are probably- well, exaggerated. Since then people have added a lot to the stories, like the wireless electric Pierce Arrow car, which have no basis in Tesla's work at all. That wireless car was totally a made-up story, for one, the principle character is supposed to be a relative of Tesla but we know he didn't even have such a relative. Tesla's known works never claimed to have worked on anything like this, and if he'd had such a practical success you'd think he would have capitalized on it.

 

[docel]

wireless charger

The nearest commercial equal is the Patented "Wireless" cell phone charger. Just a transformer without the iron! An old gimmick that someone has "patent'ed now.

For some general interest...
https://www.firstscience.com/site/articles/solar.asp

 

[kjennejohn]

Another example of 'wireless power transfer' would have to be the rechargeable toothbrush. The whole thing is a transformer. The base has the primary winding, while the tootbrush body contains the secondary winding. Enough coupling exists between the two to charge batteries sufficiently over the long period of time between brushings.

End two cents.
kenjj

 

[HarveyH42]

Don't look to the Tesla books for real information. The truth is his wireless power experiments were not well documented in a technical sense. A lot of wild claims were made at the time. We do understand the capacity for broadcasting power the exact way he wanted to do it (no magic here) and know the whole idea is impractical, and the stories are probably- well, exaggerated. Since then people have added a lot to the stories, like the wireless electric Pierce Arrow car, which have no basis in Tesla's work at all. That wireless car was totally a made-up story, for one, the principle character is supposed to be a relative of Tesla but we know he didn't even have such a relative. Tesla's known works never claimed to have worked on anything like this, and if he'd had such a practical success you'd think he would have capitalized on it.

How could anybody capitalize on wireless power? Wouldn't anybody with a reciever be able to access the power, without a meter or anything to measure usage? It costs money to generate the electicity, but how would you charge the people using it? Now, if you are raking in huge profits on the poly-phase system (also Tesla), why scrap it for a zero-profit, high cost system, or even allow someone to develop or impliment one?

Now, Tesla's wireless power is high frequency and high voltage, so not much you can do with it. I don't recall seeing any down converters in all his patents or lab notes, so guess he had planned on all new motors and stuff, probably just to screw a bunch of rich guys over...

I have a small Tesla coil, and did many different experiments (haven't fired it up in many years). The plans say 10-14" arcs, closer to 8", its 250,000 volts.
A flourecent tube will glow (not fully or brighter than the arcs come off the coil) 10-15 feet away. I made sort of a helicopter from a "Z" shape piece of tin. It was only suppose to spin, didn't expect it to take off, pretty cool. I kind lost interest after a while, little worried about it messing up other electronics, computer, TV... And yeah, got zapped a bunch of times. It's not painful, or really dangerous, just kind of creepy, kind of like thousands of ants crawling all over your arm.

Personnally, I believe that Tesla worked to make this better for everyone, not to make a lot of money. His A.C. system and induction motors haven't changed very much in 100 years, and still the most popular. Tesla spent many years commited to wireless power, don't think he would have wasted so many years on something that couldn't work.

 

[The Mad Professor]

Personnally, I believe that Tesla worked to make this better for everyone, not to make a lot of money. His A.C. system and induction motors haven't changed very much in 100 years, and still the most popular. Tesla spent many years commited to wireless power, don't think he would have wasted so many years on something that couldn't work.

I concur Tesla's motives were far removed from his comercially minded contemperies it appears. His work I grant you is poorly documented, much of what we know comes only from journalists of the period for he shunned the scientific community and even to this day make only passing reference to him.

What would the world be like today without his efforts ? , for the likes of Marconi learnt much from him , AC power lines supply the very energy you are using to view this thread.

 

[Oznog]

Tesla sort of lost his focus in his later years. That's sort of a nice way of saying he was going nuts.

It's not an issue of whether you can charge for it. The first problem is that RF energy is not very efficient to capture with an antenna. Second is that an antenna is only exposed a miniscule amount of a non-directional broadcast. Like if you wanted to make a huge light source only 100 feet away, how much of that could you capture with a 6" solar cell? The solar cell's area can only intercept an incredibly small fraction of a percent. It's not like an antenna is a vacuum that sucks in RF energy from a large radius around it. Note that if you have one radio picking up a weak radio station, putting another radio next to it tuned to the same station does not weaken the signal. The energy captured by an antenna is so low it does not even affect signal levels very near it.

Third prob is what all the uncaptured RF energy does. It's likely that power levels required to actually *power* devices could cause significant biological effects to all living things in the serviced area. Every wire in every unshielded electronic device becomes a small antenna and it will induce such powerful levels of current that it's unlikely many modern devices could function in this field, could even be damaged.

There are cases where directional microwave energy- which we try to focus into a beam though the focusing is imperfect to say the least- can send power to a tuned microwave receiver. Not very efficient but it has been shown to be interesting because the receiver can be light and run indefinitely. However, you need a clear line-of-sight and either a fixed relationship between tx and rx or a very sophisticated tracking system. If it's a fixed tx and rx then logically just a wire would make a lot more sense. The tracking system has its uses but powering a light bulb or cell phone is not one of them. The tx can only focus on one device and you don't want to be anywhere near that beam yourself unless you're covered in tinfoil.

 

[docel]

Here is another gem of a technology:
https://www.electro-tech-online.com/custompdfs/2006/05/Dresden_Kathy_OBrien.pdf
And if superconductors (@NTP) are a reality, then...?!!

(Tnx to kathleen O'Brien )

 

[HarveyH42]

Tesla's wireless power goes beyond RF transmissions. The idea was to us the planet as a capacitor. The earth surface and upper atmosphere being the conductive plates. There is a frequency at which the earth resonates (sp). Basically, once the upper atmoshere was charged up, power could be drawn anywhere on the planet. His 'Colorado Springs Notes' goes into way more technical details then I could understand, a lot of higher math. He did demonstrate the resonant frequency of the planet, in New York, in which he was blamed for an earthquake-like situation. Stopped when the device was destroyed...