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Wireless power transmission

  1. Dec 5, 2009 #1
    How much practical is wireless power transmission, in the light of present days technologies??
    Are Laser based systems more efficient than Induction Based systems??
    How good are microwave based system??
  2. jcsd
  3. Dec 5, 2009 #2
    Seems like my question was vague. To be precise I would like to ask,
    Is there any method of wireless power transmission (for long distances of the order of kilometers) which is better than wired power transmission in efficiency and capital cost???
  4. Dec 5, 2009 #3
    We recently had a discussion of short range (1 to 2 M) wireless transmission systems - I'll search for a link.
  5. Dec 6, 2009 #4
    wireless power transmission using non resonant induction is not very efficient(e.g. normal transformers) but with resonant induction it is very efficient as compared to laser method. with resonant induction method we can transmit elctrical power up to a distance few times the radius of the coils which we have made.
  6. Dec 6, 2009 #5
    The chief problem with wireless power transmission is, IMO, independent of the technology you are using to acheive it - what is it going to do to people/animals/vehicles who get in between the transmitter and reciever?

    You can pick a wavelength, any wavelength, and several of them could be quite benign at low communications grade power, but when you have kilowatts coursing through the air, everything you care about had better be very very transparent to its passage. Otherwise, you are going to end up with non-trivial energy appearing in unwanted places, like your insides, or your electronic circuits.
  7. Dec 6, 2009 #6


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    It's a lot more complicated, expensive and inefficent than a wire.
    So you need a good reason or don't care the cost.

  8. Dec 7, 2009 #7
    A amateur experimentalist has recently developed a minor project on wireless power transfer using induction plus infrared-photocell method. It can only transfer tiny amount of power, not even enough to power a led. He is now boasting to media about its future possibilities on how it could be made more powerfull and how it could be used to displace traditional power transmission system.

    Can I safely tell him that wireless power transmission has no commercial future (at least in the light of present theories) and its more expensive, uneconomical and Hazardous?
  9. Dec 7, 2009 #8


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    Wireless power transmission is uneconomical, inefficient - and perhaps most significantly - liable to cause lots of interference with electrical devices all over the place. I think it's a bit speculative (and unnecessary) to say it's a health hazard though.

    A sanity check: While power transmission technology doesn't make many headlines or get much mindshare these days, quite a lot has happened since Edison and Tesla's day. (e.g. development of HVDC) It's a high-tech, billion-dollar industry. Companies like ABB and Siemens have hundreds if not thousands of electrical engineers doing power-transmission research.

    It's pretty unlikely an amateur is going to come up with some dramatic new idea that thousands of experts have somehow missed over the course of a century. (Yes, we've all heard the story of the person who "proved the experts wrong". What you don't hear is the other 99.99% of cases where the experts were entirely correct and the amateur a deluded crackpot)
  10. Dec 7, 2009 #9
    i am doing my final year project wireless power transmission. please tell me a suitable method to determine the resonating frequency of a helical coil.
  11. Dec 7, 2009 #10


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    Lasers are hideously inefficient, for a start, so I think we can discount them unless we have loads more energy than we know what to do with.

    'Wireless' transmission of small amounts of energy (computer mouse, TV remote) is easy to do but is it significantly better than using a 'dock' of some sort? Inductive coupling works ok for my toothbrush - but it is very close to the source. Any suitable frequency for an inductive supply within homes / factories would wipe out a large chunk of spectrum at some frequency which could be better used for communications (? questionable, perhaps; more Facebook and Forums).

    Transmitting large power levels over a significant distance would need high frequencies - to achieve directional receive / transmit antennae. These would still need to be huge, if you want to produce suitably directional beams. This applies to pretty well any frequency you care to name, at which you could produce vaguely efficient transducers each end.
    People talk encouragingly about generating electrical power out in Space and beaming it back to Earth but we are not short of Solar Energy down here and that could provide as much energy as we need without the expense of building spacecraft.

    Whilst people are considering the possible health risks of mobile phones (mW), how much more are they going to bleat about kW, high intensity, beams zapping above their heads?
  12. Dec 7, 2009 #11


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    You wouldn't use wireless anywhere that you can use wires - but there are lots of placs you don't want / can't have wire.

    VECSEL are upto 55% efficient, at a single wavelength you can make the receiving diode pretty efficeint.
    The big plus of lasers is that they can be conveniently pipped along fibre.
    People are looking at using laser to power undersea cable repeaters rather than running DC along the copper shield. This should make for lighter cable that is safer to handle.

    Might be worth it for novelty value on high end gadgets. Or convenience, rather than having to install a small awkward power plug on your new sleek phone just drop it on a mat.

    Inductive is great where you want to power s sealed unit - like a toothbrush or some medical device.
    It's also used in some precision instruments like theodolites where you need to get power into a rotating unit but don't want to use slip rings.

    True, other than possible solar satelite microwave power downinks over the ocean I can't see wireless power distribution catching on
  13. Dec 11, 2009 #12
    We have experienced a high demand for wireless power in several offshore and industrial applications. Wireless Power & Communication is a comapny that has a patented technology for wireless transmission of power. It can be used to transmitt several hundred watts with up to 95% efficiency. Due to uncertainties about health risk, we have focused on applications with transmission across a short distance. But if this is proven to be of no risk the technology can also be used for transmission across larger distances.

    See www.wpc.no for more information
  14. Dec 11, 2009 #13


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    That is an amazing claim. I watched the video, but it is in Norwegian, so I got nothing from it.

    What is actually happening with your system?
  15. Dec 11, 2009 #14
    This is the same idea tesla had back in 1899, its nothing new and has been tried before. The main problems are 1. It is vary inefficent 2.There is no way to meter the power being recieved, this is why tesla was forced to pull the plug on his own experiments when his investor realized that there was no way to make money off of it.
    3. It produces harmful radiation and can cause electronics to malfunction and even cause fires from current being induced where you don't want it to be (like in the nails in the walls of a home)
  16. Dec 14, 2009 #15
    It is a subsea connector for ROV tools. Wireless power makes it possible to unplug this connector in water without causing any short circuit. The connector enables ROV toolchanges down to 3000 meter. The connector delivers 160w, Ethernet, RS232/485 and analog video.

    The torch is the worlds only Ex approved torch which is approved for charging in hazardous areas zone 1.

    See link below for more information:
  17. Dec 14, 2009 #16


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    Does this system really provide truly "wireless" transmissio, in spirit, though? It still requires a 'connection' and would not work for many. Required applications.
    Very useful, of course, but it does not answer the question of the OP.
  18. Dec 14, 2009 #17
    In the sense of not using metallic connection for transmission of power, these product uses wireless transmission of power. Yes it is a very application specific example, but it shows that wireless power is a usefull technology.

    The distance which power is transferred across is limited, but it allowes both sides of the products to have plastic encapsulations which the power is transferred through
  19. Dec 14, 2009 #18


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    This sounds like the inductive charging cradle used for charging electric toothbrushes.
    Is it like that?

    When the toothbrush is put in its cradle, the combination of cradle and toothbrush form a transformer which is used to charge the battery in the toothbrush.

    Is your device like that? Or does it use concentrated ultrasonic power to drive a generator in the flashlight?
  20. Dec 15, 2009 #19
    Yes, the technology uses two inductors with cores to transmitt the enegry, but the amount of power and the efficiency differs from the toothbrush metode. Our technology can transferre several hundred watts with up to 95 % efficiency. If you feel the toothbrush it gets warm even though it is very little power that tis transferred. That is because the efficiency is very low.
  21. Dec 18, 2009 #20
    I think I read about this somewhere, what I read was that the umbilical is used as one conductor and the sea is actually used as the other. Except the one I was reading all the communications used fiber optics.
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