Post with wireless electricity is it possible?

  • #1
A post, each which connected without a wire, is it possible in a brief future?
 

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  • #2
russ_watters
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A post, each which connected without a wire, is it possible in a brief future?
Not in a significant way.
 
  • #4
sophiecentaur
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A post, each which connected without a wire, is it possible in a brief future?
Do a search with Wireless Electricity Transmission.You will find many hits but there appears to be nothing that you can actually buy - except for the tooth brush charging system. There are various systems on the horizon for charging your personal devices on a table top but, to make them worth while considering, a smartphone manufacturer would need to be involved seriously with a compatible mod for charging a phone. But that is hardly more than another form 'non-contact' charging as with the tooth brush.
I saw a YouTube demo showing a TV that was claimed to be powered by a source which was a few metres away but nothing available to buy.
These days, the DIY opportunities are a bit limited for busting frontiers in technology so I do wonder just what the possibilities could be for your idea.
Anyone who links two devices with a high Power Energy Link would need to satisfy some stringent RFI (interference) requirements.
Read around, if you want a good grounding in this and do not believe anything you read that's too optimistic. It may be entertaining for you.
 
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  • #5
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Many years ago, Popular Science magazine had an article about a guy who powered his radio from the energy in a broad spectrum of ambient radio waves.

Also, brilliant inventor Nikola Tesla poured himself into trying to make the wireless transmission of electrical power work, but ultimately failed.
 
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berkeman
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  • #7
anorlunda
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You can also power your radio from narrow-band energy in the AM radio spectrum... :smile:
That picture reminds me of my grandfather. During the depression, he supported his family by making and selling radios like that one using Quaker Oatmeal boxes as the cylinder. I think I heard that he got $0.25 each for radios.
 
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  • #8
CWatters
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Contactless smart card readers send wireless power over short distances and communicate both ways.
 
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  • #9
sophiecentaur
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Contactless smart card readers send wireless power over short distances and communicate both ways.
Also the transponders in some car keys are contactless.
All these examples are about self powering devices - the crystal set operates over many miles and that's still the winner by many orders of magnitude, I think. But there is an enormous step involved to take useful power across a gap for 'general purpose' applications. The numbers, as in all Engineering, really do count and, despite the fact that he failed, Tesla's idea still rules in the minds of his followers.
 
  • #10
CWatters
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The crystal set is unidirectional which makes it easier.
 
  • #11
anorlunda
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A while back, we had a thread about the many uses of smart phones. We came up with a list more than 200 long. We might be able to something similar in this thread, thinking of the many ways to use wireless electric power transmission. Let's make it a challenge to supply at least 12 examples.

But the difficulty is the word useful (or significant). But we could use a self-defining meaning. Anything which has been manufactured and sold (like crystal radios, or RFID chips) is useful and significant by definition. Unfulfilled dreams like Tesla's, are not useful by definition.

To keep it fun, we also need to restrict examples to electric origins and destinations for the power. Mouth to microphone is wireless transmission but the mouth sound origin is not electric. But speaker to microphone is an example of wireless transmission. But is speaker-to-microphone contrived, or has is been used commercially? Also exclude destinations that need other supplemental sources of power (such as a battery powered radio, or a photo detector in a security system).

So far in this thread we have:
  1. Batteries (as in the electric toothbrush)
  2. Crystal radio.
  3. RFID chip.
 
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  • #12
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What do you make of this? https://en.wikipedia.org/wiki/Resonant_inductive_coupling

There was a company Witricity that went viral a few years ago claiming efficiencies in the order of 98% over distances of like 2m, which seems extraordinarily high.


My skepticism is largely based on the simplicity of the idea. I would have thought most high frequency transformers would be resonantly matched to some extent, so it seems natural that someone ought to have tried an air core one and experimented with the distances between the primary and secondary.

It feels like I'm missing something here. Why are inductive chargers for phones so relatively poor? Resonant inductive coupling circuits are quite simple, yet it was only discovered in 2006? Tesla spent many years trying to send power wirelessly at high efficiencies.
 
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  • #14
anorlunda
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Somebody pointed out that there is no limit on how short the gap can be. Therefore, I added 4-6
  1. Batteries (as in the electric toothbrush)
  2. Crystal radio.
  3. RFID chip.
  4. Wireless Chargers (as for phones etc.)
  5. Maglev trains.
  6. All transformers
Should we count the anode-cathode current in vacuum tubes?
 
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  • #16
bob012345
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Power can be broadcast. I saw it done in the show The Avengers from the 1960's! But seriously, that's the whole basis for microwave transmission of power from solar power satellites. A demo was done many years ago where a small helicopter was powered by beamed microwaves from the ground.
 
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  • #17
sophiecentaur
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P.S. Are you familar with Tesla's theories?
Unproven Hypotheses, rather than Theories, mostly. And I am aware of his many failures. Full marks for the ideas about Electrical Power generation and distribution but there was an awful lot of dodgy, unproven stuff.
I can't help thinking that David Bowie got it right in his portrayal in the Prestige (apart from the actual working model in the film).
 
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  • #18
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It feels like I'm missing something here. Why are inductive chargers for phones so relatively poor? Resonant inductive coupling circuits are quite simple, yet it was only discovered in 2006? Tesla spent many years trying to send power wirelessly at high efficiencies.
Resonant inductive coupling? Like a Tesla coil? :)
 
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  • #19
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The problem with "wireless" power transfer is something needs to carry the energy flux. That something is usually the magic of the electromagnetic force, unless by wireless transfer of power you are throwing mass at a thing that converts kinetic energy.

I would say we already take advantage of "wireless power", all radios work because the transmitter is sending a small amount of power to the receiver, its in probably in the u or nw range but none the less there is some power there other wise it wouldn't work. You wake up to wireless energy every morning. The giant ball of nuclear fire we orbit is transmitting oodles of power via the electromagnetic magic of photons to heat our planet and make electricity in solar panels.

If we want to reproduce that, we can, eg microwave beams and lasers. The problem is the energy flux, if you want to beam 1MW of power (ignoring inefficiency for now) you have 1MW micro wave beam, needless to say that would be problematic for anything crossing it, probably including air.

Doing it over large distances with something that cannot be focused will be immensely ineffective and inefficient while likely cooking everything in the vicinity, its what the sun is doing (~point source) so the portion of energy flux its throwing into space vs what we get is a number with a lot of zeros on the end of it, ie not something you would do if you had to pay to generate all that power.

Wires are just so much better at actually moving significant joules per second.
 
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  • #20
sophiecentaur
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Resonant inductive coupling circuits are quite simple,
I can't help thinking that there is a flaw in the concept. A good resonance requires a High Q (quality factor), which implies low resistive loss. That means there can only be low Power involved. Passing significant power into a load would immediately kill the resonance peak.The demos that I have seen (like the Video above) show lamps being lit and modern LEDs are very efficient, showing lots of light and requiring very little electrical power input. The demonstrator used the term "Electricity" which puts his credibility as an Engineer, way down in my estimation.

There was a video, some while ago, that showed a TV that, apparently, was powered from a coil, a couple of metres away. Nothing was mentioned about the power being transmitted or about the power being put into the transmitter. I must say that, if I had a really viable system to sell, I would say "Look. It is feeding 90W into that TV and the transmitter is only using 110W (or 95W?). As with all these schemes, no one ever seems to quote actual figures.
 
  • #21
The problem with "wireless" power transfer is something needs to carry the energy flux. That something is usually the magic of the electromagnetic force, unless by wireless transfer of power you are throwing mass at a thing that converts kinetic energy.

I would say we already take advantage of "wireless power", all radios work because the transmitter is sending a small amount of power to the receiver, its in probably in the u or nw range but none the less there is some power there other wise it wouldn't work. You wake up to wireless energy every morning. The giant ball of nuclear fire we orbit is transmitting oodles of power via the electromagnetic magic of photons to heat our planet and make electricity in solar panels.

If we want to reproduce that, we can, eg microwave beams and lasers. The problem is the energy flux, if you want to beam 1MW of power (ignoring inefficiency for now) you have 1MW micro wave beam, needless to say that would be problematic for anything crossing it, probably including air.

Doing it over large distances with something that cannot be focused will be immensely ineffective and inefficient while likely cooking everything in the vicinity, its what the sun is doing (~point source) so the portion of energy flux its throwing into space vs what we get is a number with a lot of zeros on the end of it, ie not something you would do if you had to pay to generate all that power.

Wires are just so much better at actually moving significant joules per second.
What is the nw and u range?
 
  • #23
n=nano
u=micro
Ahhh, I didn't realize it.
Thanks, Essen!
 
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  • #24
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I can't help thinking that there is a flaw in the concept. A good resonance requires a High Q (quality factor), which implies low resistive loss. That means there can only be low Power involved. Passing significant power into a load would immediately kill the resonance peak.The demos that I have seen (like the Video above) show lamps being lit and modern LEDs are very efficient, showing lots of light and requiring very little electrical power input. The demonstrator used the term "Electricity" which puts his credibility as an Engineer, way down in my estimation.

There was a video, some while ago, that showed a TV that, apparently, was powered from a coil, a couple of metres away. Nothing was mentioned about the power being transmitted or about the power being put into the transmitter. I must say that, if I had a really viable system to sell, I would say "Look. It is feeding 90W into that TV and the transmitter is only using 110W (or 95W?). As with all these schemes, no one ever seems to quote actual figures.
It does seem too good to be true, but that alone isn't a great reason to dismiss something. I have heard rough figures being quoted, since it's very simple to measure and demonstrate high efficiency.

The TV demonstration is in the original TED talk, which is probably a better ambassador than that youtube video I linked.

https://www.ted.com/talks/eric_giler_demos_wireless_electricity

There are some papers on the topic as well. It feels like there might be something to it all, but I can't reconcile the fact that it was only "discovered' recently, and that it isn't ubiquitous.

http://witricity.com/wp-content/uploads/2016/12/White_Paper_20161218.pdf
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4052675/
http://www.ijritcc.org/download/1438243846.pdf
http://www.ijritcc.org/download/1435302043.pdf
 
  • #25
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This link gives you an indication why its not ubiquitous.

40-50% effy driving the 60W light bulb.

This inductive resonant power transfer works on the same principle as a tesla coil. You ring a high Q primary like a bell, that high Q oscillation creates a oscillating magnetic field, which you can then draw energy from with a receiving coil. The idea being that you "drain" the energy in the high q tank with your receiver before it dissipates.

It does have its applications, but it is highly unlikely that it will ever replace wire for any significant power.

In wiki there was mention of a bus, but you read a bit more about that its got to park on a pad and then lower its receiving coil and then they got what 10kW accross at something like 80%.

Then, these things work at high freq (the link above its 5Mhz) so any metal near it will reduce the Q of the sender (eddy current loss), plus there is an EMI standard or two the will probably take issue with how these work.
 

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