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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