
Demo of Short-Range Wireless Power Transfer - saycheese
https://www.disneyresearch.com/publication/quasistatic-cavity-resonance-for-ubiquitous-wireless-power-transfer/
======
jf
If you're having trouble loading the page, here is the direct link to the PDF:
[https://s3-us-west-1.amazonaws.com/disneyresearch/wp-
content...](https://s3-us-west-1.amazonaws.com/disneyresearch/wp-
content/uploads/20170215220933/Quasistatic-Cavity-Resonance-for-Ubiquitous-
Wireless-Power-Transfer-Paper.pdf)

Here are the YouTube videos:

[https://www.youtube.com/watch?v=gn7T599QaN8](https://www.youtube.com/watch?v=gn7T599QaN8)

[https://www.youtube.com/watch?v=pkMbZmwhpDc](https://www.youtube.com/watch?v=pkMbZmwhpDc)

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saycheese
TLDR: Demo shows that in a 54 m3 specially designed room that it is possible
deliver power to small coil receivers in nearly any position with 40% to 95%
efficiency — and 1900 watts can be transmitted to a coil receiver enabling
safe and ubiquitous wireless power.

~~~
seanxh
from what I observe after work in high power radio wave industry, there is a
possibility that long time exposure to high power radio wave can have effect
on people's chromosomes, not quite sure what will happen if someone expose too
long to this type of device

~~~
nardi
In this device, power is not transmitted via electromagnetic radiation, but
via oscillating magnetic fields. It's completely safe for humans and any
electronics not connected to an antenna tuned to the resonant frequency.

EDIT: Obvious in retrospect, but alternating current like this is exactly how
you make EM/radio waves, so my comment above is misleading.

However, that's the cool part about this research. They are generating
quasistatic magnetic fields, and decoupling the magnetic field from the
electric field—similar to how near-field charging pads work, but at room
scale. So they are producing very little in the way of EM radiation. From the
paper:

> For example, radiative transfer methods have tightly coupled electric and
> magnetic fields that propagate over long distances and are typically used
> for radio communication. These far-field wireless power techniques have not
> found wide spread use, since they are limited to delivering only a few
> milliwatts of power due to health and safety concerns. In contrast, non-
> radiative transfer systems such as inductive charging cradles and resonant
> charging pads can safely deliver 10s-100s of watts of power by loosely
> decoupling the magnetic fields–which are used to transfer power–from the
> potentially harmful electric fields. However, near-field coupling is a
> highly localized phenomenon and transfer efficiency drops off rapidly as the
> source and receiver are separated by more than a coil diameter. Likewise, it
> is not possible to strongly couple coils of drastically different sizes.

> Drawing upon recent work using far-field standing electromagnetic waves to
> generate uniform field patterns in a metallic chamber, we introduce
> quasistatic cavity resonance (QSCR); which can be used to create near-field
> standing waves that fill the interior of the resonant structure with uniform
> magnetic fields, allowing for strong coupling to small receivers contained
> within.

~~~
jfoutz
> power is not transmitted via electromagnetic radiation, but via oscillating
> magnetic fields

I don't think you can have one without the other, can you?

~~~
nardi
That's probably true. I admittedly am pretty bad with basic EM physics. Would
love someone to explain this to me like I'm five.

~~~
aidenn0
A varying magnetic field produces an electrical field.

A varying electrical field produces a magnetic field.

Therefore if you produce either a varying electrical field or a varying
magnetic field, you will generate the other, which will then propagate out;
this is EM radiation.

I only did a quick read of the paper, but this looks like they are generating
a standing wave (think like a guitar string, where the amplitude of motion is
fixed at any point along the string) with a wavelength much larger than the
size of the room; this lets them capture the electrical field in capacitors in
the center of the room while still having a moving magnetic field throughout
the room, thus effectively separating the two, which allows for a moving
magnetic field (which the receivers can convert to an electric field) without
having a high-magnitude electrical field in the free space of the room.

~~~
msravi
Seems to me more like they used the big copper tube in the center of the room
and the aluminum walls of the room itself to guide the current flow. It's as
if the copper tube and the room are a big conductor through which electricity
flows (actually oscillates) - this changing electric field in the conductor
creates a magnetic field in the space around it, i.e., the room. So the
electric field is contained and guided through the conducting walls of the
room, while the magnetic field permeates the space in the room itself.

~~~
aidenn0
Yes, the walls and ceiling conducting are important to this (otherwise there
would be a large induced electric field outside the room).

There are capacitive elements in the pole which is important for allowing it
to be resonant at a wavelength much larger than the room (the wavelength used
is over 200 meters).

The very long wavelength means that, in theory, one cuold design a room with
less of the perimeter conductive (a wire mesh would certainly work; they
suggest that doors and windows, or even conductive panels that are connected
could work).

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wyldfire
Avg whole body SAR limit they use is .08W/kg. For reference, IEC 60601 governs
the SAR limit for MRIs at 2-10W/kg [1]. Also, FCC limits cell phones to
1.6W/kg [2].

[1]
[https://en.wikipedia.org/wiki/Specific_absorption_rate#MRI_s...](https://en.wikipedia.org/wiki/Specific_absorption_rate#MRI_scanner_SAR_testing)

[2]
[https://en.wikipedia.org/wiki/Specific_absorption_rate#Mobil...](https://en.wikipedia.org/wiki/Specific_absorption_rate#Mobile_phone_SAR_testing)

~~~
Gravityloss
You could also heat humans, much more energy efficient than heating the whole
apartment or house.

Though it would heat any water or fat lying around.

~~~
mirimir
It's an old idea: [https://www.newscientist.com/article/mg15220615-500-not-
cook...](https://www.newscientist.com/article/mg15220615-500-not-cooking-but-
warming-serious-researchers-are-turning-themselves-into-living-radiators-by-
walking-into-giant-microwave-ovens-pete-moore-wonders-why/)

very far infrared == very short microwave

~~~
rm_-rf_slash
It was also a joke on the first season finale of Silicon Valley.

~~~
tekromancr
I remember seeing that and thinking it was actually a solid idea

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Animats
From the article: _" While QSCR enabled spaces do require purpose-built
structures, as the walls must be conductive, it offers a substantial
improvement in the tradeoff between range and the magnitude of power that can
be safely delivered."_

Think theme park and sound stage, not home and office.

~~~
glitch003
Until we start offering conductive walls as an option in new homes :)

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jacquesm
Neat stuff!

Notes:

\- pacemaker warning sign on the edge of the doorframe

\- Frequency smack in the middle of the AM band (1.32 MHz)

\- demo'ing very low power consumers

\- very directionally sensitive (just like any other radio transmitter)

\- room is set up like a Faraday cage

~~~
bowmessage
If you watch the video, they have a 3-coil power receiver that is not
directionally sensitive!

~~~
pinewurst
It's 3 coils, each at a different orientation. For something like a
smartphone, constrained in thickness, it might be difficult to do more than 2
orientations (L x W).

~~~
maemilius
You should still be able to do all three. Consider a block around the height
of the device and around half the width. You could have one set of coils going
around the small edge, one around the middle width-wise, and one around the
middle length-wise.

Unless I'm mistaken, that should give you 3 orthogonal coils.

~~~
randyrand
You are both correct and mistaken.

That does give you 3 orthogonal coils, technically, but the other 2 orthogonal
planes will get very little power.

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saycheese
Core issue with the solution appears to be that the faraday cage used by the
room would require any wireless wifi/cell access points be inside the room,
otherwise they would be blocked.

~~~
m-j-fox
That and the lack of windows might not be to everyone's taste.

~~~
comex
FTA:

> Finally, the high Q-factor and sub-wavelength operation of the QSCR room
> permits the inclusion of windows and doors, without significantly altering
> system performance.

But there may be limits on how much area can be covered by windows...

~~~
jacquesm
Thin enough silver layer on glass is transparent.

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beamatronic
What could you do with this? A small drone that hangs in the air indefinitely?

~~~
david-given
A huge swarm of flying drone manipulators in a manufacturing facility.

There are already demos of this:

[https://www.youtube.com/watch?v=JnkMyfQ5YfY](https://www.youtube.com/watch?v=JnkMyfQ5YfY)

...but drones use so much power that it's unsustainable beyond demos. Beaming
power to them suddenly makes this useful because you can keep them flying
indefinitely.

I'll predict that if Disney actually have this working beyond a prototype,
we'll see demos of drone swarms building complex objects out of children's
bricks within a year, and prototypes of tool-wielding drones actually doing
assembly within another.

~~~
bane
It also increases the weight of the payload they can move around since they
wouldn't have batteries (unless the weight of the receiving coils overwhelms
that).

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flukus
Just what the world needs, less power efficiency.

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ge96
Man that is awesome. Wouldn't mind that. I guess although you'd only use a
quarter of it, that pole wouldn't look bad in a corner of a room. But they did
say they could shrink it. Maybe you'd just tape some wires on your walls that
blend in to the color of your walls for that pole part.

I wish them well.

~~~
dawnerd
Im sure they could mask the pole by using a dividing wall or something.

~~~
ge96
Couldn't they setup wires in the corners of walls though or just in the walls
too. Is that pole's diameter a contributing factor?

I don't mean literally in the wall like behind sheetrock, I mean if you scored
a line in the sheetrock and placed the thick 12 gauge wire in there or
whatever.

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jwatte
40% efficient, so let's just generate 2.5x as much electricity! (Oh, and
remove all of that extra heat with more air conditioning, too!)

Even at 95%, I wouldn't want a 1900W cool near my body for fear of burns.
(Compare 100W light bulb)

Finally, what do other electronics do within this field? It's not like there
aren't already lots of coils (inductors) that would now have to worry about
significant RF back power!

~~~
IanCal
It depends heavily on what you're doing though, as to what the tradeoffs are.
A simple example: remote controls use very little energy and the extra energy
required at 40% efficiency would probably easily pay for the energy cost of
creating / replacing the batteries. Phones, similarly, use very little actual
energy.

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madengr
Pretty neat demo, sitting inside a loaded cavity resonator. Probably not very
practical, but still cool.

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w8rbt
Tesla would be proud.

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supremesaboteur
From the uBeam discussions, I thought this was impossible

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manarth
uBeam's USP was charging via ultrasound, rather than wireless charging per-se.

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ricardomspires
This don't have any harm to health?

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unusximmortalis
this is all cool, but those fields created all around the room could affect
(charge?!:) us as well; we are after all electrical beings before we are
biological beings; so how is the presence of such fields all around us for
extended number of hours daily for a lifetime (or half of lifetime) is
affecting human health?

~~~
glitch003
The electric field is contained by using capacitors in the pole in the middle
of the room. The magnetic field is what propagates around the room to power
devices.

But I suppose you'll say we are magnetic beings or something?

