

Wireless Charging, at a Distance, Moves Forward for uBeam - sethbannon
http://bits.blogs.nytimes.com/2014/08/06/ubeam-technology-will-enable-people-to-charge-devices-through-the-air/

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scottlocklin
I have a hard time expressing how unbearably stupid "wireless charging" of all
kinds is, especially when it is touted as "green." The only viable use case
I've been able to come up with is charging my electric toothbrush by
induction, so we don't have to worry about corrosion on electrodes due to my
drooling on them. Otherwise; "golly, let's radiate lots of energy into the
ambient atmosphere so consumers can have a science fiction experience like
they're in the Jetsons."

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erkkie
I charge my phone wirelessly in the car, with a magnetic wireless charger
which doubles as a docking station (which automatically turns on
waze/navigation). Super convenient for getting in/out of the car without
needing to attach wires.

Also imagine embedded medical devices.

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johnward
When I had a nexus 4 I used the QI charging all the time. It's not really a
must have feature but it certainly is nice to you be able to throw my phone
down with out having to plug in wires.

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timdierks
I don't know a lot about specific engineering details, but a jet engine
(turbofan) produces about 1 kw of sound energy [1]. A cell phone has about 75
sq. cm of area on one side. Thus, with perfect efficiency and spherical
propagation, the available power to the phone for a user about 3m away would
be about 0.2 watt.

However, I'm skeptical that they can actually create a kilowatt of sound
energy, and while you can focus the power (certainly you could do something
more efficient than fully-spherical propagation), you're also going to have
significant losses.

All this for a charging rate that's about 1/5 of what you get from a 1 amp USB
charger.

[1]
[https://en.wikipedia.org/wiki/Acoustic_power#Table_of_select...](https://en.wikipedia.org/wiki/Acoustic_power#Table_of_selected_sound_sources)

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xgbi
Unless they are beamforming, which is highly unprobable, I think you're right.

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timdierks
Beamforming would be cool and might actually allow this to work, although I
don't know with what efficiency.

That said, the tech just to locate the phones in space to allow the
beamforming would be a significant accomplishment itself. But forming the beam
or multiple beams to charge multiple devices is probably quite feasible.

~~~
wlesieutre
A possibly effective option would be sweeping the beam around and having the
phone report when it hits. That should be easier than trying to accurately
locate the phone first so that you can aim a beam at it.

If you can also make a reasonable initial guess of it's location (to within a
few degrees) you could narrow down the guess and check search area
considerably.

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S_A_P
The safety question does need to be addressed. While there isn't any solid
evidence that ultrasounds are harmful to fetuses, there are some studies that
into question their safety[1]. I am curious as to how much power is really
being transmitted with these things.

1-[http://www.midwiferytoday.com/articles/ultrasoundrodgers.asp](http://www.midwiferytoday.com/articles/ultrasoundrodgers.asp)

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ceejayoz
Focused ultrasound ([https://en.wikipedia.org/wiki/High-
intensity_focused_ultraso...](https://en.wikipedia.org/wiki/High-
intensity_focused_ultrasound)) can be used to destroy tissue, too. If it's
_not_ focused, the vast majority of its output is wasted energy.

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PaulHoule
No mention of safety at all.

A system like this is going to have at least the energy density of sunlight
and that transfers enough heat into your body you can feel it.

I'd be particularly concerned if the thing somehow shot a beam right at your
eyes, which are the thing most vulnerable to damage from internally generated
heat (i.e. microwaves)

~~~
mcs
Ultrasound is widely considered safe.

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ceejayoz
For diagnostics, yes.

High energy focused ultrasound like you'd probably need to charge, less so.
It's used to destroy tissue. [https://en.wikipedia.org/wiki/High-
intensity_focused_ultraso...](https://en.wikipedia.org/wiki/High-
intensity_focused_ultrasound)

~~~
PaulHoule
I've seen demos where people use an ultrasound beam to light paper on fire, so
I think the dose makes the poison.

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dlhavema
nothing about the actual efficiency of the system? aren't wireless chargers
pretty inefficient to start with? I for one would love this to hit mainstream
and be a norm for gadgets... also, how would this affect bats or dogs?

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SigmundA
Yeah so ignoring the obvious absorption and occlusion issues,
[http://en.wikipedia.org/wiki/Inverse-
square_law](http://en.wikipedia.org/wiki/Inverse-square_law) would make such a
system exetremly inefficient at any distance right?

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duaneb
"Any distance" is a little much. I'd love this just to clear up wires on my
desk, and at that distance I can't imagine the inverse square law would be too
much of an issue.

Across the house? Yea, that'd be a huge problem, I think.

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SigmundA
No, I mean _any distance_ , if it put out 10 watts at 1 inch, it would be 2.5
watts at 2 inches and .625 watts at 3 inches. You would be wasting huge
amounts of power just to not have a few inches of wire. At 15ft you would need
like 5000W to to get .001W at your device.

This is not even thinking about the efficiency of converting electricity into
sound and back again.

You could focus the sound beam to improve things but then you lose the
convenience of putting the device anywhere.

~~~
thedufer
Your math is a little off. Inverse square law means that every doubling in
distance quarters the power, so it'd be .625W at 4 inches (or 1.111W at 3
inches).

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brt9957
" the ability to charge portable electronics, like cellphones and laptops,
wirelessly using ultrasound." is more exciting than finding life on other
planets?

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WhitneyLand
The life on other planets route has less stock options.

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mrfusion
Anyone know why induction can't go longer distances?

Could homes be built with a giant coil in the whole attic that could then
power things in the house?

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arcseco
I'll try to explain, forgive my peasant understanding (Single course on
induction motors and actuators in Uni years ago)

The limiting factor for distance of induction charging is the strength of the
magnetic field per unit area or flux. Technically you could create a magnetic
field large enough to pass through an entire house, I can think of two big
problems with that off the bat however. First, the Magnetic field strength
drops as the cube of the distance from the source. The further you are, the
less effective the charging at the same power rate. As well the magnetic
permeability of air is so small (µ_0 = 4π×10−7 V·s/(A·m)), this is the reason
why iron cores are used in transformers as you would lose a lot of flux to the
surrounding area unless it is channeled through a permeable material. The
second reason is that there would be unintended effects on other conductive
materials located within the magnetic field, eg computers, copper piping. The
energy losses by induction charging are usually very very high when compared
to charging by traditional means (Cable).

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mcs
I hope this stays a powering technology and it doesn't attempt to become a
data-channel company as well.

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WhitneyLand
Why not?

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sp332
uBeam's "Press Kit" is a 404. [http://ubeam.com/wp-
content/themes/ubeam/files/presskit.zip](http://ubeam.com/wp-
content/themes/ubeam/files/presskit.zip)

