uBeam Ultrasonic Wireless Charging – A Familiar Fish Smell

In the last day there has been some buzz about the uBeam wireless energy charging device, which of course, like all great new inventions, does not actually exist yet, it  just needs the magic input of money.

It ticks all the media story hype boxes though – designed by a female graduate (in Astrobiology, of course), gets $1.7M venture capital funding from no less than Marissa Mayer (Yahoo’s CEO) and is about to get more, and solves all of our first world problems with charging our gadgets – it’s the “WiFi for energy!
And damn, they have patents pending, 18 of them, it must be a goer!

BTW, we have heard about uBeam before in 2011 when they got their first round funding. And also some technically laughable practical demonstration videos of the early prototype where she calls a Radio Shack analog multimeter a “power meter”. Maybe using the wrong test gear and the wrong test method cuts it at a consumer trade show, but you’d get laughed off the floor at any engineering trade show:


And you wouldn’t be an innovator without having given the obligatory TEDx talk, putting down engineers & experts, as if thinking outside the box is enough:

Where have we heard about this wireless gadget charging before? Oh that’s right:

The RCA Airnergy device created all the buzz in 2010, and was of course completely demonstrable grade A, gold plated Willy Wonka bullshit.
It disappeared without a trace jut as quickly as it was announced, gee I wonder why…

Of course wireless charging works, and there are many different kinds in the  energy harvesting space (yes, even via WiFi at very low power). But for charging our gadgets we need lots of power, and that only comes in the form of inductive (like used in some current phones), or, yes, ultrasonics like this uBeam product uses.

Inductive charging is here now, and with a few hiccups basically works quite well over short distances, in the order of 70-80% Efficiency. i.e. place your phone on a resonate charging pad and Bob’s your uncle.
And likewise ultrasonic power transfer is real and works, but pretty much isn’t that evolved commercially yet. But there appears to be a lot of research into it, and seems to have great promise for implantable devices and transmission through steel ship hulls and the like.
Indeed, for implantable devices, as you’d expect the transfer efficiency of ultrasonics exceeds that of  inductive coupling the further you get away from your transmitter.

So, this ultrasonic power transfer technology is real. If they can transmit through steel walls imagine what you can get through the air!

How Much Power?

So how much power can this system transfer? Well, they won’t tell you it seems, apart from it beams more power than we ever thought possible”

In an early demo video they clearly talk about using the ultrasonic transmitter to charge a battery pack which then charges the phone, just like our friend the RCA Airnergy!
A quick check of the patent shows this still seems to be the case:

The receiver transducer converts the ultrasonic waves back into electrical energy and stores it in an energy storage device, such as a battery, or uses the electrical energy to power a device. In this way, a device can be remotely charged or powered without having to be tethered to an electrical outlet.


Right there my I start to sniff trouble, just like on the RCA Airnergy device. If your power transfer is so great, why the need for the battery storage in the receiver unit?

It’s All About The Focus

Ok, so it’s real, but with a few seconds thought any design engineer will come to the conclusion that you canna beat the laws of physics captain.
If you have a wide bean power transmitter then you will have the exact same area capture problem that put the RCA Airnergy device in the dust bin of impractical ideas.
Watch the video above for the info and calcs on that.

What it comes down to is that if you have a transmitter source that goes in all directions (say you have a TX on your roof and you want to cover the room), then your captured energy becomes a simple problem about the square area of your capture antenna (ultrasonic transducer) at a set distance (ignoring losses through the air).

Ok, ultrasonics won’t be as bad as the WiFi’s  roughly Area=4*Pi*r^2 formula. But yeah, do the capture area math for a given transmitter and it still ain’t pretty. You could drop an order of magnitude at quite small distances even in the tens of centimeter range.

So obviously this thing must be  must used a focused system, otherwise it will be completely impractical right off the bat.

And sure enough, you take a look at some of their patents pending 1 2 3 4 5 6 you’ll find that they all mention a focused system.
Ok, so what’s the big deal with that?


So, they have claimed they want to have one of these ultrasonic transmitters in every Starbucks coffee house. That means you need a wide angle transmitter say on the roof covering X amount of square area.

Something does not add up here. You have two competing requirements. You need the sharp focus to get efficient power transfer, but you want to cover a wide area like a shop? Are they going to have a transmitter over every persons head for every chair in the shop? No, of course not, that would be silly!

A-ha!, a quick look at one of the patents reveals the magic:

“wherein the sender controller changes a steering parameter based on the signal received from the communications device.

Terrific!, the focused transmitter is steered based on some magic location detection voodoo from your gadget. Ok, you can get rough location data using various techniques (e.g. bluetooth tracking on a phone), but that doesn’t solve the problem of needing one per person in a shop if everyone wants to charge.

It’s starting to sound rather complicated…

And based on the latest photo of the prototype it looks like it’s steered by, well, her hands. Hmm, jut need some more funding, they’ll figure out the steering and location detection stuff later…

So I can’t help but think if you have to have a convoluted steerable focused transmitter on your roof and matching receiver with (fairly accurate by necessity) location detection technology, then why not just use existing charging Qi-type mats that many current phones support on the table the people are sitting at? or at home? No mess, no fuss, work every time with just a couple of resonate coils, cheap and fairly efficient.

But wait, you can use beam forming, after all that’s how you can get those neat 3D pictures of babies from ultrasound machines. But how good is this over the span of meters through all with all it’s losses, what is the beam area to antenna capture area ratio? And what happens when you flood a Starbucks with dozens of units? It’s the stuff engineering practicality nightmares are made of.

Perhaps I’m blind, but I can’t see any possible way that uBeam is going to be practical for the claimed situations of use in homes and businesses in open space. And certainly not a match for the simplicity, low cost, and efficiency of existing inductive charging systems.

Remember, ultrasonics suck if you get anything in the way, like yourself, other people, objects etc, and air is a horrible medium to transfer ultrasonics though. I can picture people trying to do the uBeam stance to find the sweet spot. “Come on, I’m over here you stupid steerable transmitter!”

Standby Power Consumption

Another big thing to ask is, what is the standby power consumption of this ultrasonic magic?
The inductive Qi charge can get in the order of 100uW with almost instant receiver detection time.
What does the uBeam offer in this regard? Obviously it would have to match this in some regard, you know, because of all that energy star saving the planet stuff which is kinda really really important for mass consumer technology.

They would obviously have to have some form of detection system in the transmitter to know when a device is within range so they can switch on the transmitter, otherwise you’d be just pissing away vast amounts of power 24/7. My first thought would be a small ultrasonic transmitter or maybe IR LED  (what a cop-out, ultrasonics for the win!) in your gadget in order to switch the transmitter on. Or maybe an app in your phone and use your WiFi to transmit to the transmitter to tell it to turn on?, or maybe old-school 1970’s data transfer by flashing your phone screen to send a few bytes. Scratch those last two, they suck.

But another look at the patent tells:

wherein the sender controller causes the sender transducer to emit the ultrasonic waves based on the proximity of the sender transducer to a receiver transducer.

So how are they doing this exactly? Maybe some form of reverse ultrasonic ping? The patent diagram just shows a magic ether between the two controllers.

It seems they have thought of dynamic TX power output presumably based on a signal level value from the receiver.

It seems they have thought of everything, except possible how practical it might be in the real world.

Oh, BTW, if they haven’t thought of my ideas yet, then those ideas above are hereby public domain. (Google Keywords: Patent Prior Art)

Health Effects

Then there are of course the obvious health impacts of flooding rooms with high energy ultrasonics.

I don’t know much about this, but you’d have to keep it to safe enough levels (120dB? uBeam claim 155dB max) which then impacts your attenuation vs distance of course. And then what about beat frequencies between units? This is how ultrasonic directional speakers work.


Yes, ultrasonic power transfer technology can work, and work well. But just like inductive charging, it only really works efficiently within a properly designed and controlled environment. I can’t see any way it can work with any sort of requisite efficiency in uncontrolled open spaces like they claim. It’s going to be way too fiddly with focused steerable transmitters and comms technology. And possible health impacts give me the willies. This has to compete with inductive charging, and well, I can’t see how it can possibly do it.

On one hand you have a couple of resonate coils of wire, some clever circuitry, in a cheap controllable and efficient low power standby system. On the other hand you have hurdle after hurdle of practical engineering challenges in what will ultimately be not very well controlled environment, with high power transmitters, transducers, comms systems, steerable elements (how?), and the inescapable higher cost that goes along with it all.

The problem with ideas like this is that they sound great on the surface, and can generate a great deal of media hype and funding without anyone stopping to think if the claims are viable or practical, and if any limitations are solvable with more research and funding. So this is my attempt to ask the genuine engineering questions that I think needs asking on this. And I’ll add to this post as things come to hand.

And just like Solar Roadways, I posit that no amount of funding is going to fixed an idea that has fundamental engineering limitations and problems, when an existing simple, cheap and proven technology already exists. I want it to work, I really do, but the design engineer in me says this one will ultimately fail, and everyone will have wasted their money. But hey, it’s the investors money to waste, but the only problem with that is it encourages further investment in ridiculous ides that a competent engineer can show will be impractical on the back on the napkin.

But as always, these are my initial engineering thoughts on this, and I stand to be corrected. Perhaps Meredith Perry would like to explain why my doubts are unfounded?

But from the TEDx video, it sounds like a classic case of belief over engineering, and pushing on and on to make the technology work regardless of how impractical, inefficient and cost in-effective it is. Like a dog with a bone, these “ideas innovators” will never give up their dream and admit their idea is not practical. They’ll just keep pushing down an engineering death spiral until the money runs out. And of course in the end it will be someone else’s or something else’s fault instead of being a brain dead idea from the get-go. And this is what will happen when this project falls on it’s arse.

But hey, engineers are really easy to convince, just show us the data!

Oh, and if you want to know Ms Perry’s views on physics and the laws of thermodynamics, here you go.

Forum discussion HERE

UPDATE on new funding and the impossibility of it all HERE

Here is a comprehensive FAQ on the issues with uBeam

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  1. Facepalm. This reminds me of a conversation I had with a friend in college if we could use lasers to transmit electricity. Original electricity has to be converted into laser light (nowhere near 100% efficiency), laser has to travel through medium (some losses there), and be converted back into electricity with a solar cell (again, nowhere near 100% efficiency). It just makes no sense since you are going to be wasting so much power, so stick with the wires. I might be more intrigued if this was a way to collect power from the ambient noise (plenty of that in the city), but still the numbers don’t come close to adding up.

  2. I think the problems with the Starbucks scenario could be solved by having a transmitter at each table, with an old-fashioned power button that you push when you want fo charge your device. It could turn itself off automatically after 15 minutes or so. Although, it seems simpler to just have a standard 5V charger at each table 😉

  3. Some people and their ideas simply amaze me.

  4. Energy cannot be created nor destroyed, it just changes from one form, to another..

  5. Did you guys see that giant 3d phased array wireless power transfer device? That thing was badass

  6. Sniff'n the crotch

    What do you mean with “A Familiar Fish Smell”.
    I can only remember the smell of dead fish in norway.

  7. 155db relative to what? On the same scale as that used for audio sound pressure level, 155db is apocalyptic. It will cook you and/or shake everything to pieces. Like you say, Dave, this is wishful thinking coupled with not enough technical knowledge to realise that you have had a stupid idea.

  8. So based on her TED talk, it’s all of us engineers who are the problem. We spend our days preventing the great thinkers of the world from solving the worlds most important problems.
    How evil we are. And engineers never come up with any fresh ideas because we only think in binary ( will it work or not).
    Of course when she needed to build a prototype she got an engineer to spend two weeks of his own time so she could tell everybody “I” got it working 2 weeks before the show. Then got top engineers to work for her, no wait with her, (so is she paying them for their experience and expertise or are they doing it for free). But it’s her thinking that is the magic not the years of experience and experimentation and hard work these engineers did for many years to enable her idea she discovered “in 2-days on google” ( reading what evil engineers placed there for her to read) to become reality.

    It’s so great to have such great thinkers solving our worlds greatest problems such a wirelessly charging her cell phone. I really don’t know what we would do without them.

    • The TEDx talk was hilarious. Who wrote all those wikipedia articles she read for the ideas? Some of those linearly constrained experts perhaps? I admire drive and resourcefulness, but the recent $10M funding round sounds like a case of hot money pouring into a poor idea.

  9. Did I see some mention of using this to charge implanted medical devices such as pacemakers? Would that be practical? My dad has a pacemaker and it had to be replaced because the battery was at end of life. Would have been nice if it had been rechargeable so he could have avoided that surgery (not inconsequential for someone pushing 90!).

    I worked on check reader/sorters back in the 70s and 80s (yes, I’m a geezer). We used ultrasonic transducers to monitor the checks in the processing path. Optical sensors are subject to problems due to the large amounts of paper dust in this environment. The sonics operated at 40 KHz and were pretty much impervious to dust. We did tests with 1/8 to 3/16 inches of dust piled up on them and saw little or no signal degradation. It was interesting work and I suppose was pretty much “leading edge” technology at the time.

  10. This looks completely impractical to me. The tradeshow demo showing transmitting of some energy via ultrasonics over about a foot proves nothing. OK, so we get 10 volts on the “power meter”. How many mA of current do we have? Not much I’ll bet. And if you are a foot away from the transmitter you might as well just slap your phone on an inductive charger, that would be far more efficient.

    If the ultrasonic waves are going to be focused, how will the focusing work? Will you then need N ultrasonic transmitters to charge N devices?

    If you can get $10M funding this easily then sign me up…

  11. AndrogynousAutomaton

    Ever occur to you that their engineers might be smarter than you?

  12. Yes, here in Russia we already passed the times of Usonic wash mashines.

  13. Dave what are your thoughts about cota wireless charging from ossia ?


  14. I just want to point out that locating a device is actually pretty simple if there is also a line-of-sight requirement. You can do what the Wii and it’s sensor bar does but in reverse. You just need an IR camera on the transmitter and the device in question with IR LEDs in a specific pattern.
    Note: I also don’t believe that Ultrasonics powering devices due to the power requirements and inefficiencies involved. Just wanted to point out that locating something in the real world can actually be fairly cheap.

  15. “the attenuation at 100 kHz would be about 3-4 dB per meter. If we assume that the transmitter is 100% efficient, the receiver is 100% efficient, the beam is 100% straight, the receiver is perpendicular to the beam, there are no obstacles between the receiver and transmitter (discussed in Question #8), and there are no nonlinear effects (discussed in Question #10), uBeam will still be only about 10% efficient at a distance of 2 meters”

    If it’s 4 dB per meter, then 2 meters is 8 dB loss due to atmospheric absorption. 8 dB loss is 15.7% efficiency on the worst end. Best case of 6 dB loss at 2 meters means it is 25% efficiency. How did you come up with the 10% efficiency? I concede that it is probably far worse than 10% efficiency when other factors are accounted for, but you are specifically talking about absorption loss.

    • That was a mistake, now fixed. It doesn’t change the basic conclusion, but numbers ought to be accurate.

      • George, no offense intended. I really appreciate your work and absolutely agree with you. I just wanted to make sure there were no mistakes in your work so that nobody can poke holes in it.

        What’s crazy is that they claim 15 foot range. Since we don’t want to kill bats, they will need to use 120 KHz which has even higher attenuation. Assuming 4 dB atmospheric absorption per meter, we’re talking 98.5% loss just from heating up the air! That’s before we even count beam dispersion, misalignment, poor orientation, hands blocking signal, and receiver conversion loss!

      • Did you see Techcrunch accusing you of “blind cynicism” even though he basically confirmed all the suspicions. The only thing new is that Ubeam has switched to 45kHz to 75kHz audio to try to disprove the criticism of 100 GHz attenuation. I guess they don’t care about dogs and cats, much less bats.

      • Here’s UBeam’s latest claimed operating parameters.

        * uBeam has developed a high-powered air-coupled ultrasonic transducer to transmit and receive sound waves at a single frequency within the range of 45kHz to 75kHz with an output of 145dB to 155dB (or 316 W/m2 – 3kW/m2)”

        * uBeam can charge multiple devices simultaneously within a range of up to a 4 meter radius from a single transmitter

        I looked up the attenuation curves for 75 KHz despite the
        fact that it would severely injure cats. 75 KHz has slightly lower attenuation at 1.1 dB/ft versus 1.6 dB/ft for 100 KHz.

        So at their claimed operating range of 4 meters or 13 feet (they used to claim 15 feet), we’re still talking 96.3% atmospheric absorption.

        But there are many more additional efficiency losses to deal with.

        * We have 70% loss for receiver conversion
        * 93.75% loss due to signal spread if the beam coverage is 4 times wider than the receiver. Since UBeam claims to be able to charge multiple devices at the same time, this loss is likely far greater.
        * 50% loss due to obstacles like hands. If you’re forced to put the phone facing down to receive a signal from the ceiling, the phone useless. If you’re forced to place the phone facing up, we can get much better performance with Qi chargers.
        * 30% loss due to sub-optimal angular alignment. This could easily be 100% loss if the angle is greater than 90 degrees.

      • George Smith, you really need to question Energous’ claims.

        “Energous is a publicly traded company (stock symbol WATT). Their website describes a charging technology called WattUp, which transmits power via radio waves[51]. Energous’s website says that each WattUp transmitter can reach a range of 15 feet, and charge 12 devices at once[51]. Energous has signed a partnership agreement with a “tier one consumer electronics company”[52], likely Apple or Samsung[53], to include its technology in cellphones. uBeam’s website claims that “RF [radio] and microwaves also both require impractically large transmitters and receivers to send power over distances greater than a meter”[1], but this appears to have been proven false by Energous’s CES demonstration[8].”

        Here is the only article raising questions.

        Energous claims 16W at 5 feet using 5.7 GHz.

        Even assuming 100% efficiency and zero inverse square loss, the FCC transmit max is 1 watt and we all know EIRP doesn’t actually mean more energy. If Energous did focus the energy, they’d have to drop 1 dB transmit power for every 3 dBi antenna gain. Either way they’re likely going to face more than 99.99% beam spread loss.

        Energous seems to be pulling the same stunt as RCA.

  16. Manuel ✓Straight, Cis-gender

    You sure called this one out early. I’m glad the mainstream media is starting to recognize this one as “the next Theranos”. About time!

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