Ultrasonic Power Transfer Investigated Using Data from uBeam Patent Filings
hackaday.com
hackaday.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...:
"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.
Then you have to contend with any orientation offset. If the receiver is off by 90 degrees or more, there is zero energy received. If your hand blocks half the surface area, that's another 50% power loss.
If you boost the power above 140 dB safety limit, you can burn your hands or cause other problems. At 140 dB at 2 meters, the theoretical best case with 100% efficiency transmitter and receiver will deliver 0.85 watts. You obviously lose even more than that.
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.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.
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).
PS: I suspect the real issue is making a receiver fit into a reasonable cellphone case.
Let’s read a bit more:
”the power levels beamed are more than 50 times lower than the lowest ultrasound imaging exposure limits set by the FDA for medical imaging”
The lowest limits I could find in http://www.fda.gov/RegulatoryInformation/Guidances/ucm070856... is 20 mW/cm^2 (“A simple conservative approach for pulsed Doppler FHR monitors is to use 20 mW/cm2 as a guide for the maximum spatial-average pulse-average intensity at the transducer face”)
Dividing by 50 for the ”more than 50 times lower than the lowest ultrasound imaging exposure limits”, and multiplying for (ballpark) 100 cm^2 receiver area (about what one can get in a mobile phone), I get 40 mW of power received.
http://www.fda.gov/downloads/MedicalDevices/DeviceRegulation... gives 17 mW/cm^2 for ophthalmic use, so 20 mW/cm^2 isn’t even strictly the lowest limit set by the FDA.
There may be a useful product here, but if so, I don’t see how all of what they say can be true.
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?
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.
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.
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.
Or, and this is really out there, larger batteries?
Which elfin focus group told everyone that a phone's weight should be measured in carats? I'd sacrifice a few extra ounces for a doubling in battery life without adding new devices.
Also, a common trajectory is shooting for something impossible, but discovering possible and useful things along the way which turn into great businesses. So even if you're 100% sure the idea is impossible, it might still be a good investment.
What is the point then? Plug in your phone, so you don't have to plug in your phone?
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/ [2] https://www.americanpiezo.com/standard-products/air-transduc... [3] https://en.wikipedia.org/wiki/Ultrasonic_welding [4] http://www.ndt.net/article/ultragarsas/63-2008-no.1_03-jakev...
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.
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.
Here's an extremely in-depth analysis of this new snake oil.
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.
A fool and his money.
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.