text: 
  Ultrasonic Power Transfer Investigated Using Data from uBeam Patent Filings - szczys
  http://hackaday.com/2015/10/20/the-curious-case-of-ultrasonic-power-transfer/
  ======
  Someone
  [http://ubeam.com](http://ubeam.com):
  
   _" The most recent paper to investigate the safety of ultrasound was just
  published [...] Of note is that this study used energy levels to tissue that
  were orders of magnitude higher than levels that uBeam’s system uses."_
  
  The abstract at
  [http://www.sciencedirect.com/science/article/pii/S0041624X15...](http://www.sciencedirect.com/science/article/pii/S0041624X15001973):
  
   _" Demonstrated in vitro, 0.6 W of transcutaneous ultrasound power transfer
  to an implant.[...] with an average RF input to electrical charging efficiency
  of 20%"_
  
  So, at best, 3W is "orders of magnitude higher than levels that uBeam’s system
  uses". That may charge your remote, but not your phone.
  
  ~~~
  Retric
  iPhone 5 has a 5.45wh battery. If you can place a "speaker" in your room and
  add 0.3w * 8 h while you sleep that's ~44% charge every night. Which could be
  fairly useful. Up the power or assume people spend more than 8h a day in there
  bedroom and plenty of people would spend up to say 200$ to have one less thing
  to worry about.
  
  ~~~
  szczys
  Sure, as long as it's right in the focus of the beam. If that means putting it
  in one particular spot, is there any benefit over inductive chargers? That
  method would be faster and more efficient.
  
  ~~~
  ChrisGammell
  Also, not to be the old guy...cables don't bug me THAT much. I'll take USB C
  and charge with 100W instead, thank you very much!
  
  ~~~
  darkmighty
  I'm with you. Investors/companies have to get into their heads that power
  transmission will never be as easy as data transmission. There's no power Wi-
  Fi, only some crude expensive approximations over mediocre distances with
  mediocre power levels. We could instead focus on improving _cables_ (and
  confined power in general) -- have them available everywhere, retractable,
  higher power. There's hardly any physical limit to confined power
  transmission; if you look at trends into the future you might expect device
  power consumption to actually rise a little, only furthering the divide.
  Cables are just so more elegant.
  
  Part of the problem not discussed here is the 'Absorption conflict': for
  efficient power transmission you need materials that are able to absorb very
  well the given form of power; but at the same time you want nothing to
  interact in the path of the unconfined flux. This can only be dealt with up to
  a point, since our everyday objects' configuration and atomic composition are
  not so different from the composition of a receiver. This applies to all
  technologies: even for resonant EM power transfer you are relying on a
  specific conductor geometry; thankfully there's no strong conductor in our
  bodies, but you will have to deal with metal parts everywhere.
  
  Wireless information gets around this kind of limitation because power ceases
  to important for the capacity of a channel [1] past a threshold (roughly when
  the signal PSD equals the noise PSD), while the determining factor is
  bandwidth. So you just use a few Ghz+ radiation and you have enormous
  bandwidth available; once that becomes insufficient we can move to Thz+ light;
  and so on without much environmental concerns (just medium concerns --
  atmosphere gets opaque), since power levels will be kept constant or lower.
  
  [1]
  [https://en.wikipedia.org/wiki/Channel_capacity#Example_appli...](https://en.wikipedia.org/wiki/Channel_capacity#Example_application)
  
  ~~~
  Retric
  I can think of a single highly popular counter example which used 100%
  wireless power over several miles.
  
  [https://en.m.wikipedia.org/wiki/Crystal_radio](https://en.m.wikipedia.org/wiki/Crystal_radio)
  
  RFID are often a short range example of the same idea.
  
  So, it's less that wireless power is useless As it is modern devices needing
  lots of power.
  
  ~~~
  darkmighty
  Crystal radio is an interesting concept -- but note I didn't claim it was
  impossible, just highly inefficient and with mediocre power/range (I couldn't
  find sources, but apparently it's typically 40uW with a ~1m? antenna).
  
  Remember that's for a (usually) 50kW station -- that's 1e-9 efficiency, or
  0.0000001%. Realistically I'd expect you to be able scale this to 10k's
  receivers to up to about 0.001%. It's not realistic to increase this power
  significantly due to health/electronics concerns for persons living close to
  the source and massive consumption -- bringing the power near a single station
  to 4W would consume 5GW, about 1% of total US power consumption!
  
  Interesting to imagine a system with sightly higher frequencies (20Mhz?)
  dedicated to power transmission. It'd essentially be a hugely wasteful system
  (and expensive with high powered antennas everywhere to mitigate invsq law)
  which however might be able to power ultra low power sensors and gadgets. Some
  clever phase distribution (pseudorandom modulation should do it) system would
  allow location with ~15m accuracy too (even working indoors, although building
  refraction and reflections might be a little troublesome).
  
  ------
  api
  "even some high-profile investors that include [Mark Cuban] have not seen the
  uBeam working."
  
  I don't understand how people can raise money like this. Investors usually
  like to actually see evidence that you are actually doing something, right?
  Right?
  
  ~~~
  jacquesm
  I've seen a few requests come in where I really wondered if the subject
  investors had any technical knowledge at all.
  
  Investor scams are unfortunately rather common.
  
  As soon as secrecy, a breakthrough and a very large market coincide the
  gullible and their money are soon parted. I personally don't think this is a
  bad thing because it keeps me employed, at the same time you'd wish that this
  sort of thing would stop because it most likely hinders genuine breakthroughs
  from being given the attention they deserve. Some of those get recycled a few
  years or decades later so not all is lost but still, a few cold fusions and AI
  winters and the tech industry as a whole suffers.
  
  As for the uBeam, ultrasound is a strange medium to choose for this particular
  job, ultrasound is fickle, has a ton of side effects, isn't particularly
  efficient and interferes with living creatures in all kinds of un-desirable
  ways. Going the electromagnetic route would seem to be the first thing to try
  (and some companies are doing this and have products, maybe not 'miracle
  class' but they'll do the job they're designed to).
  
  The best bet for getting rid of the charger cord are a strong reduction in
  required power for the phones, better battery technology, maybe micro fuel
  cells or some other exotic conversion technology.
  
  Populating the world with ultrasonic transmitters with about the same range as
  the charge cord they replace seems to fix one minor inconvenience by replacing
  it with a much larger one, not a company I'd bet on.
  
  ~~~
  api
  With the opening of seed investment to the general public, I unfortunately
  think you're going to see a huge increase in professional investor scams. I
  fully expect organized crime to get involved.
  
  Of course anyone can go blow their money at a casino and with a much lower
  odds of return than investing on AngelList, so I'm not sure it's an overall
  bad thing. Still I am concerned about loss of signal in noise and about
  'winters' as you say.
  
  ~~~
  jacquesm
  In plenty of places seed investments have been open to the general public just
  about forever and as far as I know there have not been any major differences
  between the number of scams purported there versus in countries where
  investors need to be accredited.
  
  Crowdfunding is currently doing a great job educating people on the risks of
  putting money up for vapourware but since those are not investments per se
  there is still a gap in that education that will surely be filled once the
  stops are pulled. Organized crime is already involved in investments, look no
  further than the LPs of some of the funds that have high visibility. That's a
  far quicker way to get a return than to bilk a few million out of the pockets
  of the gullible public at large.
  
  ------
  petra
  Why don't startbucks really buy usb charging ports or usb charging mats and
  put it on their shops , if that's so important ? why don't anybody big do it?
  
  ~~~
  bsder
  Because they don't want to encourage people to stay longer than they already
  are.
  
  ~~~
  zemvpferreira
  Actually, I think every Starbucks in the Bay Area has induction chargers built
  into several tables (along with a number of charging dongles to choose between
  for your particular phone connector):
  [http://www.digitaltrends.com/mobile/starbucks-pma-
  wireless-c...](http://www.digitaltrends.com/mobile/starbucks-pma-wireless-
  charging-launched/)
  
  ~~~
  Animats
  Their active area is so small that an ordinary USB-A power outlet would be
  more useful. You have to plug the rigid coil into your device, then place it
  exactly over the charging circle.
  
  ~~~
  zemvpferreira
  Induction is a very practical solution for when you don't have your USB
  charging cable with you. Plus, who's going to steal the coil to use at home?
  And it's a pretty magical experience when you use it.
  
  ~~~
  Animats
  That your phone can get position info from satellites is magical. That you can
  bring two halves of a transformer together and get power would not have
  surprised an electrician from a century ago.
  
  ------
  rjdagost
  When I first heard of uBeam and their goal I did some back of the envelope
  calculations. Setting aside the safety issues (which are not settled, start-up
  CEO claims to the contrary), the biggest problem is conversion efficiency.
  Using some optimistic assumptions about conversion efficiencies and beam
  steering accuracy, I don't see how they're going to achieve even a 10% net
  conversion efficiency at useful distances. So I've been very skeptical about
  the prospects of success, yet I am very interested to be proven wrong on some
  of my assumptions. But the longer this product launch gets stretched out the
  more skeptical I get that this will ever be a product that anyone would want
  to buy. This is starting to feel like Theranos- the time has come to put up
  some real evidence.
  
  ------
  rootedbox
  If you have a room filled with speakers basically.. You are going to have
  phasing issues.
  
  ~~~
  jacquesm
  And you're going to have the sum and the difference frequencies to deal with
  as well if the transmitters aren't perfectly synchronized. And those
  differences may very well be within the audible range.
  
  ~~~
  beamatronic
  If nothing else, now you've created a new type of Active Denial System
  
  ------
  jimrandomh
  [http://predictionbook.com/predictions/125891](http://predictionbook.com/predictions/125891)
  (entered back in July)
  
  ------
  Animats
  Those articles mention uBeam's patent filings, but don't actually cite them.
  You can look at their patent applications.[1]
  
  The overall system is described in their patent application #20120300593. This
  shows the overall plan: focus big transmitting transducers tightly on small
  receiving transducers. This resulted in a patent, #9094111. But to get the
  patent, they had to narrow the main claim to include "a receiver
  communications device adapted and configured to send input to the sender, the
  input comprising a power requirement that causes the sender to change a dwell
  time of the sender on the receiver". That's not an essential component of such
  a system, so it's not a broad patent.
  
  There's an application on beam-steering, #20140281655. That's a known
  technology, and the USPTO has sent back a non-final rejection based on prior
  art. But that tells us the plan - big phased array of ultrasonic transducers
  aimed at a tiny target. Direct line of sight is necessary between transmitting
  array and pickup array.
  
  How could they generate 155dB of ultrasonic energy? They applied for a patent
  on their transmit transducer, application #20140265727. That has an image of
  the sending transducer. It's a piezoelectric device with a silicon membrane,
  with a vacuum behind it. (The vacuum in back is to avoid pumping half the
  energy back into the device itself.) A "thin film" piezoelectric element makes
  the membrane vibrate. Devices like that have been built before, and the USPTO
  accordingly just sent them a final rejection. There's no new feature there
  which allows generation of more audio power than existing devices. So assume
  their device has performance roughly comparable to existing devices.
  
  Here's a product list from American Piezo, a commercial supplier of high-power
  air ultrasonic transducers.[2] Their highest power unit that transmits into
  air is 119dB. uBeam is claiming 155dB. That's 36dB more, or 4000 times as much
  power. That device needs 30V into 2K ohms to power it, or about half a watt.
  So uBeam's transmitter would need about 2 kilowatts, comparable to a small
  clothes dryer, spread over a large number of transmitting transducers. An
  array 64 square would do it. The American Piezo transducer is 16mm across, so
  the transmitting array needs to be about a square meter. That's a big
  transmitting array, with 4000 elements, each with its own drive electronics.
  All that energy, or as least as much as they can focus, gets aimed at a tiny
  target.
  
  The parent article discusses the attenuation problem. This gets worse with
  frequency.[4] Measured values of attenuation in air at 1MHz at 20C are between
  160-165dB/m. This is huge. 1m from the transmitter, all the power is gone,
  used to heat the air. uBeam wants to operate in the megahertz range, but no
  way will that work. At 50KhZ, where most air ultrasonic systems work,
  attenuation is only 2dB/m. Their demo system (with about 1 foot range) used
  off the shelf 40KHz transducers.
  
  This thing might work in the 50-100KHz range, with a rather large and
  expensive transmitter array, when the target device was facing the
  transmitter. Safety remains an issue; if they actually built a 155dB system,
  they'd have a steerable ultrasonic welder.
  
  They could potentially build a nice demo system. Build a meter square array of
  off the shelf transducers running in the 50-100KHz range and mount it in a
  large picture frame. Cover it with speaker grille cloth, maybe with a picture
  silk-screened on so it looks like a framed picture. Have it scan at low power
  until a cooperating device reports a signal. Then focus the beam and turn the
  power up to full.
  
  It's not going to be totally silent, because some harmonics will get through
  and some objects in the target area will vibrate with the ultrasonics and
  resonate at a lower frequency. But it probably wouldn't be noticeable at a
  noisy trade show.
  
  You probably don't want to be near the focus of this thing.
  
  [1] [http://www.faqs.org/patents/assignee/ubeam-
  inc/](http://www.faqs.org/patents/assignee/ubeam-inc/) [2]
  [https://www.americanpiezo.com/standard-products/air-
  transduc...](https://www.americanpiezo.com/standard-products/air-
  transducers.html) [3]
  [https://en.wikipedia.org/wiki/Ultrasonic_welding](https://en.wikipedia.org/wiki/Ultrasonic_welding)
  [4]
  [http://www.ndt.net/article/ultragarsas/63-2008-no.1_03-jakev...](http://www.ndt.net/article/ultragarsas/63-2008-no.1_03-jakevicius.pdf)
  
  ~~~
  the8472
  So, bottom line is, if the charging part doesn't work out it can still be used
  as an expensive steerable space heater / killing device?
  
  ~~~
  Animats
  It might "work", for small values of "work". With a big emitter, at moderately
  short range, and a receiver on the back side of a laptop screen, it might
  work. Modest sized conference rooms with art on the walls, for example. Small
  classrooms. Maybe even a Starbucks.
  
  Emitter panels on the ceiling could charge mobile devices placed face-down for
  charging. A car-based system could charge devices of people using phones while
  driving, if you had enough short-range emitters around the car.
  
  The line of sight limitation, though, makes it only slightly more convenient
  than a power cord. The electromagnetic charger people have the same problem,
  but they're mostly thinking "put mobile devices on charging pad on bedside
  table", which works but isn't selling.
  
  ~~~
  the8472
  > The electromagnetic charger people have the same problem
  
  they can just build those into tables and mark the area that charges instead
  of having to tile an entire room with those transducers.
  
  Having a human slightly adjust his behavior (place laptop on one of the
  rectangles) in exchange for reliable charging should be far less frustrating
  than a supposedly automatic system with lots dead zones that the user can't
  see.
  
  ------
  hatsunearu
  [http://www.eevblog.com/forum/projects/the-ubeam-
  faq/](http://www.eevblog.com/forum/projects/the-ubeam-faq/)
  
  Here's an extremely in-depth analysis of this new snake oil.
  
  ------
  rootedbox
  One other thing.. Look at all there demo videos, and pictures. The size of the
  amp they are using to produce this volume of sound is pretty insane.
  
  So..
  
  1\. This is going to add to your monthly electric bill considerably.
  
  2\. I wonder what kind of EM those amps are putting out.
  
  ------
  sandworm101
  If these people want to milk some billionaires for whom shelling a few million
  is easier than taking the time to understand a technology, I say more power to
  them. So long as they aren't receiving taxpayer support, nor draining the
  lifesaving of retires, then they can sell their dream for as long as dreamers
  have deep pockets. Is it really any worse than homoeopathy?
  
  A fool and his money.
  
  ~~~
  jacquesm
  > Is it really any worse than homoeopathy?
  
  That depends on whether or not the inventors are aware of the fact that their
  tech likely will never work.
  
  In that case it is fraud. In the other case it is simply some group of people
  that are very much ready to believe their own story and successfully
  transmitting that enthusiasm to investors. I've seen a couple of cases like
  that and it always makes me sad that reality will shatter the dream ('wouldn't
  it be nice if?', yes, but that does not automatically mean that it is
  possible...).
  
  More often than not charisma plays an important role in these exercises in
  wishful thinking.
  
  If the purveyor of new, unproven tech is aware that it does not work there is
  yet another class of character, the ones that think they're only 'faking it
  until it will inevitably work'. Just one more little kink to work out and
  _then_ all the reasons to fake it will disappear.
  
  The only ones I have no compassion with are the cold hearted fraudsters who
  dream up their schemes knowing full well they'll never deliver. Those are -
  fortunately - quite rare.
  
  ~~~
  sliverstorm
  I am reminded of:
  
  [https://www.youtube.com/watch?v=DkGMY63FF3Q](https://www.youtube.com/watch?v=DkGMY63FF3Q)
  
  