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It's widely believed that Nikola Tesla not only demonstrated wireless power transmission but his works in this field were very successful.

Wikipedia only says this

The electric energy transmitted by means of electrostatic induction can be utilized by a receiving device, such as a wireless lamp. Tesla demonstrated the illumination of wireless lamps by energy that was coupled to them through an alternating electric field.

but there's a lot of statements as in here

Nikola Tesla started the wireless energy transfer revolution almost 120 years ago.

and there're lots of fanatic claims about Tesla being able to transmit power wirelessly and later generations having lost his achievements.

Now wireless power transfer is possible but the efficiency is rather low. For example, Wikipedia has this statement (not backed up though)

For example, the Magne Charge system employed high-frequency induction to deliver high power at an efficiency of 86% (6.6 kW power delivery from a 7.68 kW power draw).

and Magne Charge charges an electric vehicle via a pad placed inside the slot on the car, so transmitter and receiver coils are very close to each other. Efficiency goes down quickly as distance increases.

Well, okay, let's just agree we've lost Tesla's secrets. Also I realize that if there was a detailed enough description of a machine for efficient wireless transmission of electricity someone would make use of it.

I don't hope to find anything like that. I'd be happy to just find trustworthy evidence of actual fact of transmission taking place with specific (hopefully miles) distance and specific efficiency.

Is there any evidence that Tesla was actually able to transmit power wirelessly with commercially reasonable efficiency?

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related: skeptics.stackexchange.com/q/10996/6876 –  Ryathal Feb 1 '13 at 15:41
    
If such proof were accessible to you or I, why wouldn't someone (in USA, Russia or China) have used it to create commercial products by now? –  RedGrittyBrick Feb 1 '13 at 15:42
    
@RedGrittyBrick: You've forgot about conspirancies and evil corporations who are not fond of gas car industry getting useless. –  sharptooth Feb 1 '13 at 15:54
    
@RedGrittyBrick: Actually I'm not asking about a constructive proof like "Tesla constructed this specific thing and the efficiency was this", I'd be happy to see a confirmed claim like "At date this Tesla transmitted power at gazillion miles with this efficiency". –  sharptooth Feb 1 '13 at 15:56
    
@Sharptooth: I believe he demonstrated illuminating partially evacuated tubes wirelessly (but this wasn't how his "World System" was intended to work). Some modern artists have replicated this on a larger scale by planting fluorescent light tubes below power pylons. –  RedGrittyBrick Feb 1 '13 at 16:25
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3 Answers

TL;DR;

Tesla's Patents and notebooks are available. Tesla was often interviewed and gave public demonstrations.

There's no convincing evidence that he had really discovered a means of transmitting power that could be commercially implemented in the way he envisaged in his "World System".

There's no evidence (that I can find) which proves his system could achieve the 99.5% efficiency he claimed.


Tesla's Secrets

we've lost Tesla's secrets.

By definition, that's impossible to answer, we've also lost Newton's secrets and Edison's secrets. If any. But we know that Tesla's US patent 1119732 for Apparatus for transmitting electrical energy is on public record.

Tesla wrote

I obtained convincing evidence of the feasibility of wireless power transmission on a vast scale for all industrial purposes.

The chief discovery, which satisfied me thoroughly as to the practicability of my plan, was made in 1899 at Colorado Springs, where I carried on tests with a generator of fifteen hundred kilowatt capacity and ascertained that under certain conditions the current was capable of passing across the entire globe and returning from the antipodes to its origin with undiminished strength. It was a result so unbelievable that the revelation at first almost stunned me. I saw in a flash that by properly organized apparatus at sending and receiving stations, power virtually in unlimited amounts could be conveyed through the earth at any distance, limited only by the physical dimensions of the globe, with an efficiency as high as ninety-nine and one-half per cent.

Nikola Tesla's Colorado Springs Notes were published as a book.


Wireless Transmission of Power

Is there any proof that Tesla was actually able to transmit power wirelessly with commercially reasonable efficiency?

Judging from the number of web-sites that cover this topic, a large number of people have looked for this. None of them seem to have found anything commercially exploitable so far.

Colorado Springs. 1899-1900.

Tesla had a lab in Colorado at which he is said to have demonstrated illuminating light bulbs at a distance.

  • illuminating light at a few hundred feet
  • illuminating light bulbs at a range of five miles

I have not yet found any reliable primary sources for these stories. The reports are brief and certainly contain no data concerning efficiency.

enter image description here(from PBS)

Caption in Century Magazine, June 1900, reads: "The photograph shows three ordinary incandescent lamps lighted to full candle-power by currents induced in a local loop consisting of a single wire forming a square of fifty feet each side, which includes the lamps, and which is at a distance of one hundred feet from the primary circuit energized by the oscillator."

It seems Tesla's focus was on demonstrating feasibility. It seems unlikely he was especially concerned about efficiency at this stage.

Tesla envisaged that his "World System" would be able to transmit power across thousands of miles, point to point, through the earth, with negligible power losses. It would also be able to power aircraft and ships.†

Wardenclyffe. 1900-1917

Tesla's backers provided funds for a long-range communication system, but Tesla was mainly interested in demonstrating the feasibility of his "World System" for wireless power distribution.

Since Tesla's Wardenclyffe Tower never became operational, Tesla was unable to demonstrate the system of power transmission he planned for his "World System"

The failure of this project suggests that Tesla was unable to provide his financial backers with convincing proof that the idea was commercially exploitable.


Efficiency

Is there any data on how efficient Tesla wireless power transmission was?

We've seen above that Tesla claimed 99.5% efficiency.

I haven't read much of the Colorado Springs notes, I have the impression that his demonstrations didn't measure efficiency of power transfer.

I believe his "World System" was intended to work on slightly different principles. In a 1927 article Tesla contrasts his system with power transmission by short wave broadcasting.


Conclusion

For all the reasons given above it seems unlikely that Tesla provided experimental results that demonstrated commercial feasibility with the technology of the day.


enter image description here
(Tesla wireless power - but not his "World System") enter image description here
(also not Tesla's "World System")


Miscellaneous references

1 2 3 4 5

Footnotes

(Frankly I find his writings and reported interviews somewhat confusing, but I'll try to provide references for this paragraph in a later edit)

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I'd dispute the last assumption as Wardenclyffe was an extremely complicated technical undertaking, saying that it failed provide proof would be like saying that the LHC failed to provide proof o the Higgs boson before the it was started. Since Wardenclyffe was never fully operational we can't say it was a failed experiment either. –  rob Feb 1 '13 at 16:11
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Also, with regards to the commercial feasibility, if the power is going to be transmitted through the air, it's inherently not very commercially feasible as you don't have a means of billing people for usage. :) –  rob Feb 1 '13 at 16:13
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@Rob: I'm suggesting 1) The Patent apparently is not such proof. 2) T lacked proof to convince backers. 3) Since W was never completed, the proof (by demonstration) it was intended to provide does not exist. 4) Therefore the proof the Q seeks probably didn't exist in Tesla's lifetime. –  RedGrittyBrick Feb 1 '13 at 16:19
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@Tim: Google isn't free, they charge their customers (the advertisers) quite a lot. It's true they don't charge their product/meat (you and I) for being sold. That would be like Hormel charging pigs to be put into cans. The free bait is tasty though. –  RedGrittyBrick Feb 2 '13 at 11:00
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@TimQuinn - It's a mater of semantics that can trip people up though. If you say the experiment failed then people tend to assume that the hypothesis was invalid. If you say that the experiment was never completed then people tend to assume that the status of the hypothesis is currently unknown pending further investigation. –  rob Feb 3 '13 at 0:15
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The reason it failed was that Tesla could generate the eletricity, send it out into the air, but he could not control where it went, like a bolt of lightening from a storm. Are their people still trying to create wireless power transmission...yes. They are attempting to control the path of the electricity using certain gasses, but it is not feasible for the real world...yet.

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Welcome to Skeptics! Please provide some references to support your claims. –  Oddthinking Feb 2 '13 at 6:10
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This post does not cite any references or sources. Please help improve this post by adding citations to reliable sources. Unsourced material may be challenged and removed.

There are a few people who set out to rebuild Tesla's invention in the last years. Davor Emard rebuild a bit of Tesla's technology and presented it at 26C3.

Today there a company called Witricity that tries to bring such technology to market. There a TED talk that explains that they use magnetic fields that are in resonance with each other and can transfer electricity that way.

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I'm unclear if this answers the question. –  Oddthinking Feb 1 '13 at 20:02
    
Yes, magnetic fields that " are in resonance with each other" to provide power transmission would be called induction and, as I said above, that is the central discovery of the electrical revolution, not anything earth shattering or new. This is marketing talk. –  Tim Quinn Feb 2 '13 at 7:19
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I'd like to add that "in resonance with each other" has the admirable quality of not meaning anything in particular. It can be defined to mean something quite mundane or left to the imagination to be something fascinating and revolutionary. –  Tim Quinn Feb 2 '13 at 7:22
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