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Power

Ultrasonic Power Transfer Investigated Using Data From uBeam Patent Filings (hackaday.com) 120

szczys writes: Transmitting power through the air using sound above the range of human hearing: that's the gist of ultrasonic power transfer. The promise is that you can sit in a coffee shop and use your phone like normal while it's recharged by invisible waves of energy. That's a future we all want — and one that uBeam has been promoting, but hasn't backed it up with proof. Physics is a cruel mistress, and this is no exception. Using the data found in uBeam's patent filings you can see that ultrasonic power transfer is a brutal engineering challenge. It's probably not impossible, but looking at what it would take for a widespread rollout of the tech makes it highly improbable.
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Ultrasonic Power Transfer Investigated Using Data From uBeam Patent Filings

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  • by DumbSwede ( 521261 ) <slashdotbin@hotmail.com> on Tuesday October 20, 2015 @04:45PM (#50768401) Homepage Journal

    ...But my EYES and EARS are bleeding.

  • by grimmjeeper ( 2301232 ) on Tuesday October 20, 2015 @04:49PM (#50768433) Homepage
    When are people going to learn that pushing power through air, in any form, is horribly inefficient and impractical for anything more than a science experiment?
    • oh? I think winding two or more sets of insulated wires around an inductor might be a way to push power through the air while altering EMF level for devices that need it at a different level, in a very efficient manner. We could call such a device a pusherformer.
      • There's a reason transformers don't have coils across the room from each other. Maybe someone smart already figured out how fast the energy drops off the further away you get... ;)
    • by sims 2 ( 994794 )

      100W of power to get 10W to charge my phone is acceptable if my phone will charge when placed anywhere in a 20x20ft room.

      As long as I still have to place my phone in a 0.5x0.5ft area to use a wireless charger i'll just stick with a cable.

      • Re:Ugh (Score:4, Insightful)

        by U2xhc2hkb3QgU3Vja3M ( 4212163 ) on Tuesday October 20, 2015 @05:09PM (#50768599)
        The whole planet is struggling to keep up with energy demands and you think it's acceptable to waste 90% of the energy you use?
        • What percentage of the energy in sunlight striking the Earth do you think gets wasted?
          • by Anonymous Coward

            What kind of a stupid rhetorical response is this?

            It's like asking "How much water does Niagra Falls waste?" in response to someone pointing out the stupidity of hosing down your pickup truck during a drought.

          • Outside of plants, about 95% of it.

            With plants, about 90% of it.

          • Actually: none.

            It hits the earth, so it has an effect ... what exactly did you want to say?

        • by sims 2 ( 994794 )

          If I am the one that is paying for it why should you even care?
          There are hundreds of thousands of outdated computers still in use today that have much worse power efficiency ratings compared to today's equipment. Their was a /. article about that a short while ago. http://hardware.slashdot.org/s... [slashdot.org]

          Energy demand problems in this country tend to be related to NIMBY. We need a new power plant but no one wants it in their backyard.

          I like energy efficient appliances up to the point that they no longer function a

        • The whole planet is struggling to keep up with energy demands and you think it's acceptable to waste 90% of the energy you use?

          The amount of power used to charge cell phones is negligible. So it doesn't really matter if it is inefficient. It is still negligible.

          I get into a similar argument with co-workers about water here in California. They wanted to save dishwater and use it to flush the toilet. Then I pointed out that we can flush the toilet twice a day for a year with the amount of water saved by eating tofu for lunch instead of beef ONE TIME.

          Keep some perspective.

        • The whole planet is struggling to keep up with energy demands and you think it's acceptable to waste 90% of the energy you use?

          Yes

      • Exactly. If I can't have charging as useful & accessible as wifi, then what's the point?

    • I like this. With the exception of Tesla, pushing anything through the resistance of air tends to look like lightning with all of the downsides.

  • it would already have been done. Obviously did not RTFA, but this probably has very bad efficiency and a lot of the power gets lost.
  • by Anonymous Coward
    People who think that you can run your entire house off a generator connected to a bicycle, or that putting a propeller connected to a generator on the hood of your car is 'free energy', are the same idiots who believe that 'wireless charging' is a good idea. The Inverse Square Law [wikipedia.org] fully applies to any sort of wireless charging because physics works, and no amount of wishful thinking or marketing bullshit is going to change that. Sitting there saying 'But it works, we have it right now' means Jack Shit beca
    • What people need are docking stations. No cable to handle and yet it's not wireless.
    • The Inverse Square Law [wikipedia.org] fully applies to any sort of wireless charging because physics works.

      I'm pretty sure the fact that most wireless charging systems operate in the near field and rely and near field effects means that the inverse square law doesn't "fully apply". Even if it does in a technical sense, the distance between transmitter and receiver is very small.

      • by Khyber ( 864651 )

        "Even if it does in a technical sense, the distance between transmitter and receiver is very small."

        Induction charging, even at its best, is only about 40% efficient and that's practically touching coils together.

        • Induction charging, even at its best, is only about 40% efficient and that's practically touching coils together.

          Sure, but that loss isn't due to any inverse square law, is it? Like you said, the coils are practically touching. The op was implying that all wireless charging is stupid because loss increases with the square of the distance. I'm saying (with no research and little expertise in the area) that all of the wireless charging I've seen operates in the near field; and while I don't know how much that 40% efficiency number you gave could be improved upon, I doubt that the dominating factor in the loss is distanc

          • by Khyber ( 864651 )

            "Sure, but that loss isn't due to any inverse square law, is it?"

            A good deal of that loss is inverse square (or inverse cube in the case of omnidirectional transmission.) Doesn't matter if you're doing millimeters, centimeters, inches, whatever. Whatever you're getting at 2mm distance is half (or less) what you'd get at 1m distance. That's how great the inverse dropoff effect is.

            • Cool, does that mean I can get infinite power out of it as long as I can get the receiver and transmitter arbitrarily close to each other? Sounds like each time I cut the distance in half I get twice the power. Zeno saves the day!

              If distance=0 represents a theoretical "full power", then how do you double that distance to get the half (or quarter) power according to the inverse law? If some distance > 0 represents "full power", then getting the TX and RX that close ought to be free of this nasty inverse s

              • If distance=0 represents a theoretical "full power", then how do you double that distance to get the half (or quarter) power according to the inverse law?

                You're halfway across the bridge.
                You're three quarters of the way across the bridge.
                You're seven eighths of the way across the bridge.
                You're fifteen sixteenths of the way across the bridge.
                You're thirty-one thirty-seconds of the way across the bridge.
                You're sixty-three sixty-fourths of the way across the bridge.
                You're one hundred twenty-seven one hundred twenty-eighths of the way across the bridge.
                You're two hundred fifty-five two hundred fifty-sixths of the way across the bridge.
                (and so on, and so on..)

                A

              • by sims 2 ( 994794 )

                After you get so close the wires touch and then its not wireless power anymore. :P

              • by KGIII ( 973947 )

                Yup. In fact, you can already do that. You just plug it in and contact is made. Tada! You now have wireless power - except for still having the wires, of course. But you get much greater efficiency. (Reduction starts immediately - as soon as you have even the smallest of gaps.)

      • For linear attenuation of sound, Stoke's Law [wikipedia.org] is more appropriate for a back of the envelope estimate. More searching will yield more refined models. That being said, no planar transducer propagates only linearly, and there is decay in the x and y directions (considering z as the normal vector).

        I was scratching my head when I read about this idea because I work with ultrasonics a bit and we have a heck of a time with maintaining energy density over short distances.

  • by bobbied ( 2522392 ) on Tuesday October 20, 2015 @05:02PM (#50768543)

    Any technology which attempts to push power though a transmission medium where you have to worry about the "Inverse of the Square" of the distance is going to fail on it's face. Sound though air is such a problem. Magnetic and electric fields though air/vacuum is another. Power transfer may be possible, but the amount of losses means it will never be practical unless you have HUGE amounts of power to waste.

    In this case you may not be able to hear ultra sonic frequencies, but that does NOT mean it cannot harm your hearing at the SPL's required to get any kind of power transferred.

    • by sims 2 ( 994794 )

      For the small amount of power required I feel 10% efficiency is acceptable. I doubt any wireless charging tech will ever be energy star certified. Wireless charging tech will always be less efficient than wired. But I think you will find most people are willing to pay for convenience.

      • by Khyber ( 864651 )

        "For the small amount of power required I feel 10% efficiency is acceptable."

        When it comes to SPL, your efficiency means nothing. We're still dealing with sonic ranges, here. For you to get enough sound energy to charge your wireless phone in an hour inside of a room, the ultrasonic energy would be such that it would fuck with you if you spent more than ten minutes in proximity to it.

        How acceptable is it when your brain and hearing is getting turned to shit? 7 watts at audible ranges is enough to make you d

        • by sims 2 ( 994794 )

          That would be a unacceptable sacrifice in safety.

          If that were acceptable we would have microwave based.. http://www.thinkgeek.com/stuff... [thinkgeek.com] wireless charging today.

          Wifi is only safe because it is so low power even though it operates at the same frequency as your microwave.

      • Consider this..

        You won't get 10% unless you are within a very short distance, lets say 1 foot is that distance, lets also say that the collection surface is 1 square foot, which is big for a phone, but is about right for a large tablet. Charging takes 1 hour. If you assume an isotropic radiation pattern from the emitter, a 1 foot sphere has a surface area of 4*Pi*(square of (1)) or about 12 square feet. My phone has a 12 Watt/Hour battery, so assume 1 square foot generates 12 watts, and my huge phone w

    • It 3 dimensional, therefore inverse cube, not inverse square. But agreed, losses are phenomenal over even short distance with an omnidirectional point source. an array of transmitters in the ceiling would be slightly more efficient, but in that case, why not use infrared transmitters and photovoltaics? Or, here's a twist: use sunlight?
      • It is inverse square, not cube.
        We are talking about the area the beam is hitting, not the volume of space it is occupying.

      • The issue is not about the volume, but the energy passing though the surface of what ever geometry the radiator emits energy into. Of course the "isotropic" radiator is the theoretical device that puts out equal amounts of energy in all directions and makes the math simple because we can use a sphere. The surface area of a sphere is (4*Pi* Radius Squared).

        I've run the numbers elsewhere, but if you have a 1 foot collection area about 1 foot away from an isotropic radiator, you will get about 1/10th of the

    • Magnetic and electric fields though air/vacuum is another. Power transfer may be possible, but the amount of losses means it will never be practical unless you have HUGE amounts of power to waste.

      Not true. Microwave power transfer with rectennas can have efficiencies up to 90% or so...

      https://en.wikipedia.org/wiki/... [wikipedia.org] https://en.wikipedia.org/wiki/... [wikipedia.org]

      • Which is NOT practical approach, even for what is intended.

        Microwave power transfer requires very high frequencies amd very large transmission antennas which can successfully keep all the energy from the transmitter in a narrow beam. Even then, the receiving end of this arrangement requires a receiving array kilometers in size because no antenna can perfectly produce a beam of energy and going though the ionosphere, atmosphere, clouds, dust, wind and rain causes a drop off on the cohesiveness of the beam

        • Not practical NOW, no. But your statement was that this type of thing would NEVER be practical, and as far as I can see, all of your objections are simply engineering problems, the concept and theory is solid and has been proven in the lab and experimental implementations.

          The only issue is in refinement of methods and equipment, which as I said, is just an engineering issue, so your NEVER modal qualifier is simply false.

          • This isn't an engineering problem it's a physics problem, and it's the physics that make it impossible. Technology and engineering cannot change the physics, but must work within the rules that physics provides.

            All lab experiments aside, the physics of the problem mean it will not work on an industrial scale at any reasonable distance for a price anybody can afford. Why? The structures required are HUGE, literally kilometers in size, both in space and on the ground and this size is driven by the physics. B

            • ...will not work on an industrial scale at any reasonable distance for a price anybody can afford. Why? The structures required are HUGE, literally kilometers in size, both in space and on the ground and this size is driven by the physics.

              "reasonable distance for a price anybody can afford"? You keep watering down your definition of practical. So it's only practical if you can have one today, in your garage? You know that we build structures of this magnitude already, right? Space telescopes, particle accelerators... etc

              Building such structures, while conceivable and possible, is VERY expensive and VER"Y time consuming, especially in space. (Lots of money) X (Lots of time) = Never going to happen.

              The building of these structures, in terms of materials and time, is precisely the engineering problem I was referring to, so this just confirms what I already said. Sure, it may be time consuming and expensive NOW, but reduc

              • You are engaged in wishful thinking. It will NEVER be economically possible to put structures together in orbit that are measured in kilometers, espically ones that will need to be aligned to tolerances in the micrometers. It's too expensive to get the materials into orbit that would be required to build the transmitting array and it would take too long to assemble and align an array for any useful amount of power to get transferred to the surface. You cannot make smaller arrays because of the physics inv

                • You are engaged in wishful thinking.

                  Maybe, but you keep repeatedly missing the point.

                  It will NEVER be economically possible to put structures together in orbit that are measured in kilometers,...

                  I disagree, this is nothing but speculation on your part.

                  ...espically ones that will need to be aligned to tolerances in the micrometers. It's too expensive to get the materials into orbit that would be required to build the transmitting array and it would take too long to assemble and align an array for any useful amount of power to get transferred to the surface.

                  Every single one of these objections are engineering problems. Tolerances? Find better sync algorithms, better materials with less "give" in the relevant properties etc... Too expensive to get materials into orbit? Work on more efficient transport mechanisms, more efficient use of materials, or develop better/lighter materials to use, or use material from the moon, asteroids or comets etc... that you do

                  • LOL... I think you are missing the point. These theoretical things are sized by the physics and they are literally too big to fly. This isn't hubris on my part it's wide eyed practicality that's driving my preannouncements on this. These devices are KILOMETERS in size and anything that size is going to be pretty heavy. Big and heavy are the two things which are very difficult and thus expensive when you want to throw them into space, even in LEO. The amount of energy required to lift this stuff into orb

                    • Big and heavy are the two things which are very difficult and thus expensive when you want to throw them into space, even in LEO. The amount of energy required to lift this stuff into orbit will exceed what it can return as power.

                      ...and completely ignoring the idea of building using materials already outside the gravity well, or development of alternative lift methods that are more efficient. Rockets are at best like 70% efficient for lifting loads into orbit (under ideal circumstances, in practice it's lower). You're saying it's *impossible* to *ever* do better? I won't deny it might be difficult to do better, but claiming it's impossible is short-sighted.

                      Big is irrelevant, heavy is the issue. If you think it will NEVER be possible

    • by khchung ( 462899 )

      Power transfer may be possible, but the amount of losses means it will never be practical unless you have HUGE amounts of power to waste.

      Waste itself is not the biggest problem, if you are rich enough, waste becomes unimportant.

      *Unintended absorption* will be the killer. Whatever means you use to send energy, "wasting" 90% means 90% of the energy would be absorbed by *something else*.

      Probably something that is near the phone you want to charge, such as your body. Tinfoil hat should be provided to all customers.

    • Hearing is one thing, I dont want my cornea to get unglued

  • Assuming the project isn't essentially fraudulent, and is technically feasible- why? It would have worse performance than inductive charging and would require a specific alignment of an extra peripheral towards the sound source.

    Anyway, there's another link in the article to a take-down of the product that goes over basic physics and sound level safety requirements [eevblog.com] that suggest this project is fraudulent. One thing you do see in there, however, is talk about Ubeam's 25 year old CEO, Meredith Perry. A googl

  • i feel like the obvious question is, why use ultrasonic frequencies that lose half their power in a meter of air, when we could be using ultra low frequencies that travel much further before losing power - and are also much better at penetrating obstacles? something like 5hz or 10hz?

    anyone care to dig into the physics or biology of why that wouldn't work either?

    • Because a device as small as a cell phone can not pick up a wave that is several meters long?

      (facepalm)

      • looking at the size of various sound waves, it looks like for instance a 50hz soundwave has a wavelength somewhere around 30 feet. yet that is within the range of human hearing - somehow our tiny eardrums are able to hear 30ft soundwaves? so its a little more complicated than you make it out to be

        • Of course it is ... closer to 25 feet actually ... but that does not change the fact that small devices are bad with long wavelengths.

          E.g. you mainly hear low frequency sound because your body is picking it up and transports it to your head. That is the reason why your ears are not able to detect the origin(direction) of low frequency sounds.

    • by GuB-42 ( 2483988 )

      Low frequencies carry less energy per unit of amplitude.
      So to charge a phone with a 5-10 Hz frequency, you need something really loud. Loud enough for you to feel it through your body and to rattle things.

      Additionally, because of impedance mismatch, low frequencies are hard to transmit through air, that's why subwoofers are so big and powerful.

  • Doesn't "sound" very pet-friendly to me. Perhaps some evil genius is looking for a way to fund the development of his doomsday device.

  • I'd love to see this implemented. Then I'd get some popcorn and stay the heck away from the area cause once the soundwaves bounce off enough surfaces, they'll lose enough energy to fall into hearing range, and suddenly you feel like you're back in the 80s, surrounded by TVs with failing transformers.

  • If their beam-steering is actually something new and quick, then it might have applications elsewhere - medical ultrasound is a pain in the ass partly because the tech has to fool around a lot to get a good image. If you could steer the beam and do the ultrasound equivalent of auto-focus, you could make some ultrasound studies quite a bit faster and therefore easier on the patient.

    But in a Starbucks? Forget it. Install 5V USB outlets on every table and call it a day instead.

    • by sims 2 ( 994794 )

      Is there a reason why they can't use the same autofocus algorithms on ultrasound? Other than the fact that the autofocus in cameras has the bad habit of picking everything but what you want to take a picture of to focus on. What's worse is most cameras today don't even have a manual focus option.

  • Of course it will work; this is exactly what an ultrasound transducer does; it converts electrical energy to acoustic energy via mechanical strain in response to said electrical energy, then converts acoustic energy back to electrical energy via mechanical strain when impacted by the returning acoustic bounceback. Well and truly settled issue. The problem is the power loss over distance, as has already been pointed out. So while it will work, it will work poorly, be expensive, and is overly complicated. It
  • Isn't this similar to what Nikola Tesla wanted to do in order to provide free electricity to the masses?

    How can this be patented? Prior art must be all over the place.

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