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Wireless Power Over Distance: Just a Parlor Trick?

Posted by Soulskill on from the efficiency-is-a-harsh-taskmaster dept.

Lucas123 writes "Companies like U.S.-based WiTricity and China-based 3DVOX Technology claim patents and products to wirelessly powering anything from many feet away — from smart phones and televisions to electric cars by using charging pads embedded in concrete. But more than one industry standards group promoting magnetic induction and short-distance resonance wireless charging say such technology is useless; Charging anything at distances greater than the diameter of a magnetic coil is an inefficient use of power. For example, Menno Treffers, chairman of the Wireless Power Consortium, says you can broadcast wireless power over six feet, but the charge received will be less than 10% of the source. WiTricity and 3DVOX, however, are fighting those claims with demonstrations showing their products are capable of resonating the majority of source power."

53 of 215 comments (clear)

  1. this rock you rounded off is useless by Anonymous Coward · · Score: 5, Funny

    i mean, the amount of effort it took you to make that rock round and then roll a log over it? you could have carried 10 logs in that time. quit with the making new shit, gorg, it isn't useful at all and it isn't like anyone will ever find a way to improve on it. ...
    oh, nice vette, gorg.

  2. As it was before by MakerDusk · · Score: 5, Insightful

    Back in the day, Tesla had achieved even greater success. Though if you can charge from anywhere, how can you be billed? That is what will permanently stop this type of technology.

    1. Re:As it was before by CanHasDIY · · Score: 4, Insightful

      Back in the day, Tesla had achieved even greater success. Though if you can charge from anywhere, how can you be billed? That is what will permanently stop this type of technology.

      Exactly.

      It's not that wireless power distribution is a "parlor trick" - rather, the problem is that the profiteers are doing it wrong.

      --
      An enigma, wrapped in a riddle, shrouded in bacon and cheese
    2. Re:As it was before by Nidi62 · · Score: 4, Insightful

      Though if you can charge from anywhere, how can you be billed?

      Don't worry, I'm sure you'll be charged for the amount of power sent, and not the small amount of power received

      --
      The only thing necessary for evil to triumph is for it to be pitted against a slightly greater evil
    3. Re:As it was before by Anonymous Coward · · Score: 2, Insightful

      You mean "hear, hear".

    4. Re:As it was before by Randle_Revar · · Score: 4, Funny

      Yeah, and Tesla also cloaked a navy ship and accidentally sent it back in time! And the world is run by Illuminati Lizard-men!

      --
      Climate Progress - Hell and High Water
    5. Re:As it was before by geekoid · · Score: 4, Insightful

      No he did not.
      Tesla needs props, but the Tesla myth does not.

      --
      The Kruger Dunning explains most post on /. http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
    6. Re:As it was before by Anonymous Coward · · Score: 3, Insightful

      Well what's the equation for it?

      You mean like Maxwell's equations?

      Empirical observations and working technology mean nothing

      You mean like the metric fuck ton of empirical observations related to electromagnetism in every day life and engineering done for a huge swath of technology? I've seen people on the internet claim to found disagreement with Maxwell's equations. Although it seems really funny that things I've designed and built that would be orders of magnitude more sensitive to the various deviations they show work exactly as predicted. Some people don't realize how many things around them wouldn't work if such things were incorrect in such a simple manner (as opposed to say QED effects that only are possible in extreme conditions in atomic/astrophysical/particle physics).

      but the Slashdot hive mind wouldn't know it.

      Yeah, I guess they are supposed to ignore their collective empirical evidence and just pay attention to yours. Only sheeple distrust things they see on the internet.

    7. Re:As it was before by Telvin_3d · · Score: 4, Interesting

      If anyone went through with this kind of thing they SHOULD be charged by the power sent. It is, after all, taking that much power to charge your device. The wastage is your problem for being too lazy to plug in your phone.

    8. Re:As it was before by rok3 · · Score: 2

      I wish I still had some mod points. You are making too much sense to ignore.

    9. Re:As it was before by aquabat · · Score: 2

      Now, now!

      --
      A republic cannot succeed till it contains a certain body of men imbued with the principles of justice and honour.
    10. Re:As it was before by necro81 · · Score: 2

      If anyone went through with this kind of thing they SHOULD be charged by the power sent. It is, after all, taking that much power to charge your device. The wastage is your problem for being too lazy to plug in your phone.

      And I propose an additional surcharge of 100% for using such a ridiculously inefficient and wasteful technology.

  3. Re:Tesla by Pentium100 · · Score: 5, Informative

    You also have to consider the efficiency. Running a 1GW power plant just to light a 100W light bulb a few kilometers away does not seem a good idea.

    Yes, it is possible to transfer power without wires - radio has been doing it for a long time (a simple crystal radio set does not need any power other than what it gets from the antenna, but you'd better have some sensitive headphones, a big antenna and a station that is relatively close). The problem is transferring a lot of power efficiently and without huge antennas.

  4. Inductive charging pads by MichaelSmith · · Score: 2

    I think these are a great idea and I would not be surprised if Apple start to support them in the future. A phone could be built with no open connections at all. Just wireless data and inductive charging. But over longer distances the laws of physics catch up with up. Obviously the shorter the wavelength the less doffraction you get over a given distance so if you direct power with a laser and convert it into electricity with a photovoltaic cell then you could easily get more efficiency over a few metres than with induction. Maybe in the future it will be considered normal to transmit power that way.

    --
    http://michaelsmith.id.au
  5. You can transmit power wirelessly over distances. by Anonymous Coward · · Score: 2, Interesting

    ...but, the further you go the more it resembles eating your lunch sitting on power lines.

    At the one end, there is no measurable danger in charging handset on a pad charger. But do you really want to spend all your television watching hours in a room where 200 watts of power is being beamed to your TV (and 19x being radiated) from the wall to save you the bother of the unsightly cord?

    If you have magnetic wave energy, you have electric wave energy, which means you have RF. You can shape the way you transmit RF energy, but there are no perfectly absorbtive receivers, and splatter is a function of distance. So at contact distance (phone on the pad) it's pretty fine.

    The claim was "most"of the power gets there. Let's assume they are not full of crap. So 49% of the power is splatterd around. So your 1800 watt cordless hairdryer splashes 1730 watts around the bathroom? And people worry about .1 watt GSM transmitters in their phones?

    I guess I need you to trust an A/C on this point, the extra four orders of magnitude makes a difference.

  6. Re:Tesla by mike.mondy · · Score: 2

    You also have to consider the efficiency. Running a 1GW power plant just to light a 100W light bulb a few kilometers away does not seem a good idea.

    Yes, it is possible to transfer power without wires - radio has been doing it for a long time (a simple crystal radio set does not need any power other than what it gets from the antenna, but you'd better have some sensitive headphones, a big antenna and a station that is relatively close). The problem is transferring a lot of power efficiently and without huge antennas.

    Their claims are apparently that they can achieve better efficiency than had been thought possible.

    Anyone who wants us to believe differently should have independently verified proof. If you suspect parlor tricks, it's helpful to have a magician involved in addition to the scientist or engineer. "Extraordinary claims" and all that...

    Or maybe a bad summary? Almost 50% loss over a relatively short distance might match the claims of "majority of the power".

  7. No it isn't by Sycraft-fu · · Score: 5, Interesting

    The problem is inefficiency. Power drops with the square of distance. That means you need a bigass transmission source to get a small amount of power any distance away, hence why things like FM stations have 5 digit wattage transmitters.

    Yes we have been able to transmit power wirelessly for a long time, no it is NOT practical or efficient. If you are enthralled with Tesla, spend some time reading some actual books on him, not just the silly piece by the Oatmeal. He was a fascinating man and worth your time to learn about, but you need to learn about him if you want to go spouting off.

    He didn't invent some magic transmission technology we can't replicate, he invented an inefficient transmission technology that we can replicate, but don't, because he was not able to solve the efficiency problems (and it may not be physically possible to).

    1. Re:No it isn't by StripedCow · · Score: 2, Informative

      Power drops with the square of distance.

      Not if you have a directed beam of energy.

      The beam could be directed based on some set-up protocol between the energy-source and the energy-consumer.
      And you can easily direct beams by using some antenna array.

      Such direction-sensitivity could also be used to (partly) solve the billing problem.

      http://en.wikipedia.org/wiki/Antenna_array_(electromagnetic)

      --
      If Pandora's box is destined to be opened, *I* want to be the one to open it.
    2. Re:No it isn't by Anonymous Coward · · Score: 3, Informative

      Even directed beams drop off with distance squared once you get outside the near field. A directed beam is a lot more efficient than an omnidirectional beam, but for any given directional beam, power will drop off with distance squared, and narrowing the beam will require larger antennas setups.

    3. Re:No it isn't by tuck182 · · Score: 4, Funny

      I don't have any interest in carrying a phone in my pocket that's recharged via lightning bolt from the wall.

    4. Re:No it isn't by hoboroadie · · Score: 2

      I thought the resonating magnetic field solved the efficiency problem for Tesla.
      These guys aren't charging the planet at the right frequency.

      --
      They feared that it could be used to suppress protest or support unpopular rule.
    5. Re:No it isn't by Anonymous Coward · · Score: 5, Informative

      ever heard of lasers?

      Or optical masers, as they used to be called!

      how about a radio wavelength laser?

      So, regular masers, then?

      Okay, cool.

      Now go read about diffraction, and see if you can realize that lasers, masers, etc. aren't magic, and that every finite beam loses power like 1/r^2 in the far field.

    6. Re:No it isn't by Anonymous Coward · · Score: 2, Interesting

      Beam forming is just the correct use of interference patterns, and it is very useful for *information* transmission, and an useless piece of crap for *power* transmission: you still leak power like a sieve. The math is not even complex, in fact it is downright simple.

      The only way to increase efficiency is to redirect the wavefront and concentrate it where you need it instead of letting all that power go somewhere else it is not useful. This means you need to *reflect* it, maybe *guide* it (using waveguides). This is _not_ called "beamforming".

      These companies are just promoting a major waste of power for absolutely no good reason.

    7. Re:No it isn't by Evil+Pete · · Score: 2

      "radio wavelength laser" ... you mean a MASER, which is even older than the laser. Won't work. Although coherent radiation does not obey the inverse square law it does suffer divergence from diffraction effects (unavoidable) which is inversely proportional to distance. Also masers and lasers aren't very efficient so I don't think this is a solution either. Face it, Tesla was a great guy but on this he was plain wrong.

      --
      Bitter and proud of it.
    8. Re:No it isn't by __aaltlg1547 · · Score: 2

      Even directed beams drop off with distance squared once you get outside the near field. A directed beam is a lot more efficient than an omnidirectional beam, but for any given directional beam, power will drop off with distance squared, and narrowing the beam will require larger antennas setups.

      Yes, that can be done. But the collectors are very large if you want to catch most of the power. And they also suffer large efficiency losses compared to a wire and low frequency.

    9. Re:No it isn't by Electricity+Likes+Me · · Score: 2

      An under-expressed notion by the people talking about MASERs. A 100W focussed beam of microwaves might charge your laptop, but it's also going to happily start microwaving any incidental internal organs in it's path.

    10. Re:No it isn't by Neil+Boekend · · Score: 2

      Well that mainly depends on frequency. For these applications I'd advise NOT to use 2.4 GHz (the microwave oven frequency) for various reasons (not only does water and fat get heated, but also bluetooth and wifi a-g recievers have bad reactions). There are other frequencies that do fine. Preferably a lot higher (since this helps in the range). The fact that it doesn't need to transmit data (only power) means the transmitter doesn't have to be transistor based: magnetron or klystron based is easier. 40 GHz seems possible.
      These frequencies do not heat the human body, although I do not know if there is enough free bandwith available.

      --
      Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
    11. Re:No it isn't by Electricity+Likes+Me · · Score: 3

      Yes, but what if you could induce lightning in a certain location, and then convert it into energy ?
      All we need is something that can absorb the energy , and give it back at a slower rate later.

      Much more interesting than wireless electricity.

      The trick is to collect it before it turns into lightning. Stop it doing all that work on the atmosphere.

      Superconducting helium balloons connected to clouds which discharge the current build up as it occurs gives you more manageable levels of current. The average potential difference between stratosphere and the ground is something like 300,000 V at all times, so even in clear air conditions you'd get some power.

      At this point though, the volcano powerplant makes more sense.

    12. Re:No it isn't by WolfWithoutAClause · · Score: 3, Insightful

      > The problem is inefficiency. Power drops with the square of distance.

      Wrong!

      That's how radio works.

      Actually the resonant schemes DON'T use radio, they use inductance; which is just magnetic fields; and they work at much lower frequencies.

      By contrast, radio is a particular mixture of magnetic and electric fields that propagate to infinity, and you tend to lose them. That was the genius of Marconi, to get the mix right.

      But magnetic fields on their own don't propagate, that's partly why magnets don't go flat. The energy hangs around the transmitter and can be absorbed by a suitable receiver.

      --

      -WolfWithoutAClause

      "Gravity is only a theory, not a fact!"
  8. Re:No difference between power and radio by skids · · Score: 5, Insightful

    If you don't make your power signal directional, most of the power is just gonna leak away into the atmosphere.

    This is not how these devices are supposed to work... that is to say, this is not the same as radio. It's a near-field, not radiative, effect. Most of the power that does not go into the receiver returns to the transmitter as part of the resonant oscillation (via a collapsing magnetic field.) Some will be lost to fringing, but the percent lost to that per oscillation is much lower than the percent absorbed by a properly tuned receiver, by design.

    Not that I'd advocate this for consumer use, it will still be less efficient than a wire, and I'd rather see consumers suck it up and run a wire where appropriate instead of finding yet one more way to waste energy and pile ruin on our planet. However there may be some very productive niche uses.

    --
    Someone had to do it.
  9. Propagation, Dissipation, and Inductance by some+old+guy · · Score: 2

    I'm as big a Tesla fan as anyone, but I'm also a practical electrical engineer.

    Someone above already raised the end-point billing issue the utilco's will have, so we needn't bother with the bean-counter side of things. MBA's, rest easy. Your obscene profits are safe.

    However, going from a theoretical ability to blast x amount of joules across an air gap to capturing a useful fraction of x without frying the adjacent wildlife and neighbors is quite another thing. As TFA points out, they seem impressed with a 10% capture rate, which to an engineer means a 90% loss of efficiency.

    There is also this unpleasant fact of biophysics: sufficiently strong electro-magnetic fields, regardless of frequency, are inevitably fatal. The required grounding, shielding, etc. would be so outrageously expensive that the cost of copper wires pales.

    Some science fiction does eventually become science fact. However, Thermodynamics, biochemistry, and basic engineering discipline relegate most of it to forever remaining fiction. Sorry, no Nobel Prizes here.

    --
    Scruting the inscrutable for over 50 years.
  10. Re:No difference between power and radio by Lehk228 · · Score: 2

    the only way to make this efficient is to make the format mandatory and exclusive, every single device must be compatable with every other, that way battery powered devices no longer need charging cables packed in, the expectation is that you have a charging mat.

    no more car chargers, no more wall wart chargers, no more devices disposed of due to worn out charger connections.

    make sure all are compatable, or near compatable with only variability being amperage output, clearly marked on chargers and minimum to charge marked on all devices.

    --
    Snowden and Manning are heroes.
  11. Re:Tesla by mZHg · · Score: 2

    "Wireless high power transmission using microwaves is well proven. Experiments in the tens of kilowatts have been performed at Goldstone in California in 1975 and more recently (1997) at Grand Bassin on Reunion Island. These methods achieve distances on the order of a kilometer."

    http://en.wikipedia.org/wiki/Wireless_energy_transfer#Microwave_method

  12. Re:Tesla by Nidi62 · · Score: 4, Funny

    Why was his info "Illegally Seized " a at the time of his death and is still not known today ?

    I'm not saying it was aliens....but it was aliens.

    --
    The only thing necessary for evil to triumph is for it to be pitted against a slightly greater evil
  13. Re:Tesla by geekoid · · Score: 2, Insightful

    "Tesla figured out how to broadcast power miles away, wirelessly, using technology available in the late 1800s. "
    STOP IT. this is a false statement. Tesla went bat shit crazy, and made shit up.
    Yes he was a genius and found out how to do some great stuff. Lets celebrate that and not the Bullshit myth.

    I'll be impressed when you idiot can start to separate fact from fiction.
    And before you replay, if such a device existed, billing would be trivial. IT's like people really ignorant of electrical engineering and Billing practices came together to fall under a conspiracy theory instead of ACTUAL THINKING about it.

    There are many ways to bill, but I will sum up with an example:
    I pay for sewer, yet there is no Sewer meter on my sewer line.

    --
    The Kruger Dunning explains most post on /. http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
  14. Re:Tesla by geekoid · · Score: 2

    he didn't invent wireless communication.
    look up photophone (1880)
    or
    David E. Hughes 1889
    or
      Heinrich Hertz
    or
    Chandra Bose

    One popular comic ass talks about Tesla, makes factual wrong statements about Tesla, and every self proclaimed 'nerd' starts repeating it like it's actual fact.

    --
    The Kruger Dunning explains most post on /. http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
  15. not buying even if true by hurfy · · Score: 2

    Looked at one of the demo videos. There is a 4000watt transmitter (in middle of floor, nevermind the radiated power someone is gonna trip on it!) a few feet away from most of the stuff and i don't see 2000w worth of stuff.

    Don't know how it works, don't care so much to look. I don't plan on adding a 4000watt transmitter to each room, seems like a half dozen power cords would be a bit cheaper. Not that i have any interest or hope for anything called 3D power...sigh.

    But...Does the green carpet in the one vid play into it? The TV didn't come on til he touched the floor.
    Wonder how good the wireless internet is 18 inches from that transmitter where he set the laptop down.....

    What if i add this 4000 watt transmitter to my apartment, as does my neighbor, etc. Before we finish the complex we will enough power running to add a couple TV channels much less the recievers :O

  16. Re:What about the dangers? Does it cause cancer? by GoodNewsJimDotCom · · Score: 3, Interesting

    Watts = Volts x Amps. Watts is energy per unit time... My thinking is that higher Watts(higher energy) is worse for you than low energy transfer like radio/Cell/Wifi.

    My reasoning is that people who live near high power lines develop cancer at a higher rate than the general populace, while people using regular electronics and in home wiring systems don't get impacted as bad.

    --
    God spoke to me
  17. Confusing magnetic resonance and radiated RF power by kidaxess · · Score: 2

    There seems to be some confusion on this thread between magnetic resonance, which is the type of power transfer used by WiTricity and others, and radiative RF which is the radio technology we are used to. For example, received power does not fall off with the square of distance in the case of magnetic resonant systems. There are definitely a ton of challenges to this technology, but it is good to keep in mind that they are NOT talking about transmitting a high power RF signal and having it received at range. Here is a link to a paper that describes both types of systems so you can understand the implementation and trade-offs. The author's have achieved 80% efficiency over a few meters using magnetic resonance. Experimental Results with two Wireless Power Transfer Systems http://sensor.cs.washington.edu/pubs/WISP-WARP.pdf Video and other good info: http://www.alansonsample.com/research/wrel.html

  18. Re:What about the dangers? Does it cause cancer? by metaconcept · · Score: 5, Informative
    From the very PDF you link to, Question 1, right at the beginning:

    • the more recent epidemiological studies show little evidence that either power lines or "electrical occupations" are associated with an increase in cancer (see Q19);
    • laboratory studies have shown little evidence of a link between power-frequency fields and cancer (see Q16);
    • an extensive series of studies have shown that life-time exposure of animals to power-frequency magnetic fields does not cause cancer (see Q16B);
    • a connection between power line fields and cancer is physically implausible (see Q18).

    ... Overall, most scientists consider that the evidence that power line fields cause or contribute to cancer is weak to nonexistent.

    (Emphasis mine.)

  19. Re:Confusing magnetic resonance and radiated RF po by kidaxess · · Score: 2

    The referenced paper actually describes two systems based on RF power transfer. Here is one on magnetic resonance: http://www.alansonsample.com/publications/docs/2010%20-%20TIE%20-%20Magnetically%20Coupled%20Resonators%20for%20Wireless%20Power%20Transfer.pdf

  20. Re:unintended consequences by kidaxess · · Score: 3, Insightful

    They are actually using the technology to power pacemakers. http://www.alansonsample.com/publications/docs/2012%20-%20ProcIEEE%20-%20Powering%20a%20Ventricular%20Assist%20Device%20with%20FREE-D.pdf

  21. Ask 'em to put another load nearby by HizookRobotics · · Score: 3, Insightful

    There are a lot of hard engineering problems to overcome, even if the system was efficient... For example, a second resonant load nearby severely de-tunes the system, antenna mounting considerations are of supreme importance (good luck putting one on a laptop full of metal), and antenna alignment is absolutely crucial! The whole WiTricity concept might be sound in theory, but the engineering challenges are monumental.

  22. wat by shiftless · · Score: 2

    .....? So how many of Heinlein's novels did you have to read before finally concluding his non-cursing creeps you out? Was it a growing sensation, a feeling of unease slowly building inside you, nibbling away at your very soul as you shifted restlessly on your seat, brow furrowed in discontent? I can just imagine you sitting there with feet kicked back in your overstuffed blue armchair by a cozy fire, suddenly shooting straight to your feet when it dawns on you: "Holy shit! Now I realize what's been bugging me the fuck out about this crazy ass novel! It's been six chapters now and not the first fucking sign of a cussword. I'm starting to think the guy is a goddamn prude, honestly. There sure as hell better really be something lewd or crude in this incestuous intra-family love triangle / murder he's currently setting up, or I just might throw this book across the room......before hurriedly snatching it up and continuing reading to confirm that he did indeed not curse once. By God if I have to suffer through every single one of his bullshit Puritanistic preachings to get my satisfaction I will! And if I don't get it.....? Well I suppose Heinlein is a really fucking creepy guy."

  23. Tesla Worship by elrous0 · · Score: 4, Insightful

    Personally, I think the Tesla worship among geeks has gotten WAY out of hand in recent years. Yeah, I know the Evil Rich Guy Edison vs. the Poor But Plucky Tesla makes for a great literary narrative. And I don't discount the guy's work (particularly with alternating current, which he was right to argue for over DC as a practical means of long range electrical transmission). But he wasn't a god, he wasn't 100 years ahead of his time (as some recent hyperbole would have it), he didn't invent anything which subsequent engineers haven't since replicated and improved on, and he didn't certainly didn't invent EVERYTHING (the list of claimed inventions seems to get longer every year, in spite of the fact that he remains decisively dead).

    I think we do him an honor to recognize his REAL work. But we do him a dishonor to exaggerate, or even mystify, his accomplishments.

    --
    SJW: Someone who has run out of real oppression, and has to fake it.
    1. Re:Tesla Worship by JBMcB · · Score: 2

      Allright...

      >but he was not even known until the media started there conspiracy over his Monster Tower

      Utterly false - he had a famous exhibit with Westinghouse at the 1893 World's Fair. He was quite well known at the time.

      > A lot of his patents and notes have been seized and kept classified

      I've heard this claim over and over. I've never seen anyone provide any proof.

      --
      My Other Computer Is A Data General Nova III.
    2. Re:Tesla Worship by JBMcB · · Score: 3

      For the record, that would actually be *consistent* with the claim that his patents and notes have been seized and kept classified. If you want to debunk the claim that something is being kept secret, you have to do better than, "I've never seen it.".

      I'm not debunking anything as I don't have to. Some of Tesla's personal effects were seized by the government after his death and released to his nephew a few years later. Some of his documents went missing. It's possible that the government kept and classified them. It's also possible that they were simply lost, or stolen by someone else.

      Now you need some back story. Tesla was a believer in aether theory - a theory that there was undetected type of matter that energy could flow through. These theories were shown false around the same time relativity was becoming popular (Tesla rejected the theory of relativity.)

      If Tesla's dreaded beam energy weapon was based on the concepts of aether theory, the possibility of it working is basically nil.

      So, what's more likely - Tesla was smarter than Einstein, Lorentz, Feynman, Hawking, Hubble, and a few hundred other extremely bright guys, understood physics in a manner unknown to all of mankind, and it's dumb luck that all our modern gizmos that depend on special relativity to operate function as they should.
      Or - Tesla was wrong about relativity, his beam weapon never worked, and the papers about this weapon were lost somewhere?

      Tesla was a certified genius. His contributions to electrical engineering are incalculably important. That doesn't mean he was infallible.

      --
      My Other Computer Is A Data General Nova III.
  24. Re:Tesla by girlintraining · · Score: 4, Informative
    There's only one problem with people like you: You're always wrong. Tesla did do exactly what I said he did. Sorry it took me so long to check in and see some moron had gotten +5'd for handwaving while I got -1'd for telling the truth guys. Hopefully the mods will read the link and attached pictures and realize that yes, Tesla did have wireless power in the 1890s. Oh, and I was severely understating the distance: "Furthermore, the power loss experienced by Teslaâ(TM)s pulsed, electrostatic discharge mode of propagation was less than 5% over 25,000 miles. Dr. Van Voorhies states, âoe...path losses are 0.25 dB/Mm at 10 Hz,â which often is difficult for engineers to believe, who are used to transverse waves, a resistive medium, and line-of-sight propagation modes that can dissipate 10 dB/km at 5 MHz."

    I'm waiting for my apology.

    --
    #fuckbeta #iamslashdot #dicemustdie
  25. Re:Tesla by Areyoukiddingme · · Score: 3, Informative

    The problem with Tesla's system is the frequency on which it operates. 10 Hz has a wavelength of 34.73 meters. Properly receiving power at that frequency requires an antenna sized to match. Needless to say, it's not going into a handheld device. Tesla intended his system to be used in relatively large scale fixed installations. You could power your house with it, but the individual pieces of equipment in the house would be wired to the receiver. So yes, in theory his system could eliminate the grid as we know it and that does indeed address "power over long distances" as the headline does (really long distances). However, it's solving a different problem, that of very long distances using very large equipment, rather than the handheld gear over tens of feet as the articles are arguing over.

  26. It depends entirely on the range of course by dbIII · · Score: 2

    The magnetic field drops off rapidly with distance. At very close range, south American monkey in treetops near the line during winter range, there is so much induction that there is enough heat to be felt so the monkies kept warm. A field strength that high was the cause of many miscarriages among women that used poorly shielded RF plastic welding machines in the USA in the 1950s-60s. You've got to be almost close enough to worry about arcing to get that much RF from a power line, but there are known problems. Where things get odd is people insisting that twenty metres from a line is a problem, when at that range you'd be getting a tiny percentage of what you'd get from an electric blanket.

  27. Re:Still... by MickLinux · · Score: 2

    Or a wave tube. There are various things that are readily available, that will serve: for visible light, try those little fiber optic thingies. For radio and microwave, try steel pipe or conduit. For electric, try a strip of drawn copper wire, isolated with either air or polyester/pvc/nylon.

    --
    Correct Horse Battery Staple: 72 bits of entropy. Enter "Correct H" into google. When it generates the phrase, that's
  28. Re:Tesla by Hast · · Score: 2

    I looked into that article and the guy who wrote it. The quote you're quoting comes from a book he wrote himself (although the quote is from a chapter written by some other guy.)

    Unfortunately I couldn't find an online reference however, so it's impossible to know just how the measurements "Dr Van Voorheis" mentions were made. So far I've had a hard time to find any examples of people who have actually reproduced the large scale effects that Tesla claimed to achieve.

    If you look for the author of the article (Thomas F. Valone) you find some YouTube clips where he's presenting a talk about UFO power sources. And he seems to be part of a MUFON which is apparently a group of UFO hunter enthusiasts. Now there's nothing really wrong with that, but it does mean that I'm not likely to take his claims at face value. And even he doesn't claim that the Tesla stuff is real, he only quotes other people (mostly Tesla himself).

    Meanwhile you have an article at IEEE (http://spectrum.ieee.org/green-tech/mass-transit/a-critical-look-at-wireless-power/0) which seems to support the common understanding of wireless transmission of power. Basically that you can transmit power on roughly the same distance as the diameter of your coils. So a "charging pad" works, but powering a ship on the other side of the Earth doesn't.

    To summarize I have to say that I'm quite convinced that if Telsas "World Wireless System" would have worked the results would have been reproduced today. The economic benefits are way to large for it not to. I'm sure the military would have loved to have remote powered drones and stuff like that if it was possible.

  29. Re:Tesla by girlintraining · · Score: 2

    If it's an isotropic antenna radiating the power, then yes... the amount of received energy decreases as a square of the distance. But tesla wasn't using isotropic antennas. In fact, he was basically using giant coils to induce current flow in the Earth's magnetic field. By coupling it to the already-existing magnetic field, he could transmit power over very long distances at low losses... but it required a very low frequency (7.8hz) and a massive amount of input energy to run the process. It was definately not a mobile technology, and it depended on having a massive several-story tall coil as a receiver, again due to the very low frequency above.

    You're not going to be powering drones using Tesla's technology... but you could transmit power from coast to coast rather than just regionally using our existing grid.

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    #fuckbeta #iamslashdot #dicemustdie