
“Superlens” may solve wireless charging dilemma - jjude
http://techpageone.dell.com/downtime/superlens-may-solve-wireless-charging-dilemma/#.Ut4mWmS6b-k
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namuol
The problem is that our devices need frequent charges, not that plugging in is
especially inconvenient; this battle will be won on the battery-life front.

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venomsnake
On the speed of charge front. Current battery capacity is fine. What we need
is the ability to charge it for 30 seconds. So maybe supercap based batteries?

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rplnt
> Current battery capacity is fine.

If it is, then consumption is too high. Few hours of use is not "fine". Sure,
if I use it as just a phone it can last week.. but once I use it as a
computer, it drains pretty quickly.

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venomsnake
If I have 30 second charge time, any battery lasting longer than 2 hours on
usage is fine.

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dspillett
Really? You _never_ use (really use, not just have on standby) your phone for
two hours or more between there being convenient charging options? Even with a
30 second charge I'd want much longer active life than that.

I'm not sure that I actually get with everything blaring (the quickest I
uncharge my phone is when I have both radios going as I have a tablet using it
as a tether) though it sometimes isn't so I carry an "emergency" battery
charger with me when travelling.

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makomk
Of course, part of the reason convenient charging options are so few and far
between is that, because charging is slow, any public charging station is
going to (a) be occupied for long periods of time and (b) will require you to
leave your phone there for an annoyingly long period of time, meaning you're
either stuck there or risk having your phone stolen whilst you're gone.

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cincinnatus
The whole push to wireless charging feels like a bad idea. We already are
deeply in need of reductions in total global power use or at least efficiency
improvements, and wireless charging wastes a huge amount of power. Unless they
can figure out how to bring the efficiency in line with direct contact we're
better off with clever direct contact without a plug schemes.

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HillRat
This -- the fact that even highly-optimized inductive charging is about 85% as
efficient as direct-contact DC seems to get ignored a lot.

Having said that, I actually understand the appeal of charging mats and the
like, because they replace a small but persistent friction (find a charger,
plug in the charger, plug in the phone, unplug the phone, plug the phone back
in...) with a near-frictionless experience, if you don't count the cost. I'd
like to see better _conductive_ charging designs, but it looks like inductive
has won out.

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option_greek
Sounds like a fresnel lens for electromagnetic waves.

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tlarkworthy
Does anybody know how people come up with the metamaterial designs? Do they
just try lots of aesthetically pleasing symmetries out until they find one
that works?

Or do they have some forward model to predict the outcome before they build
it, but given the often inexplicable results that doesn't seem possible.

Where do the ideas come from?

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triplepoint217
Yes, we do have some pretty good theories for designing metamaterials. From
what I can remember (and quickly look up on the net), one of the leading
theories is called transformation optics, and finding a coordinate transform
to a coordinate system where the path you want light to take is a straight
line. You can work out what your metamaterial has to look like from that
coordinate transform.

I probably have some of the details of the technique wrong, I am trying to
remember a talk from a year ago. If you want more detail, look at John
Pendry's papers (he is probably the leading theorist in metamaterials).
[http://www3.imperial.ac.uk/people/j.pendry](http://www3.imperial.ac.uk/people/j.pendry)

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tlarkworthy
oh hot. Thanks a lot. Sounds like another win for eigenvectors :p

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svantana
I don't see how transmitting the power 10 inches would make charging any
easier.

The MIT spin-off WiTricity has been working on a better(?) solution since
2007, they have been consistently overpromising and underdelivering, but
recently they showed this nice-looking device:
[http://gigaom.com/2014/01/09/video-wirelessly-charging-
your-...](http://gigaom.com/2014/01/09/video-wirelessly-charging-your-
iphone-5s-over-a-distance-is-nearly-here/)

Personally I believe it would need a few meters' range before it becomes
really useful - the point where you rarely need to consciously charge your
phone because it is always charging when you're at home.

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rjdagost
I was really interested in Witricity and read a few related papers on their
technology. There are a few problems that they are not so keen to publicize:

(1) If the receiver loop isn't "inside" the transmitter loop along the normal
of the loop area then efficiency falls a bit (2) Efficiency depends a lot on
the orientation of the device being charged. If the receiver loop isn't very
nearly coplanar with the transmitter loop, efficiency bombs (3) Range is
fairly limited (4) When you have multiple devices charging concurrently,
efficiency falls for every individual device being charged as magnetic
resonance cannot be achieved nearly as well for more complicated multi-body
flux loops

Witricity has been trying to push electric car charging as for that
application these downsides don't matter as much. But even there, you get
something like 50% efficiency. Do you want to nearly double your electricity
costs just to avoid plugging in a cable? Interesting technology, but it
doesn't see like a worthwhile proposition to me.

General purpose wireless power transmission is a really difficult problem. I
was interested in the ultrasonic acoustic approach that uBeam is pursuing but
that has its own slew of problems.

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qq66
Seems like the type of problem that will be solved in order to sell products
to those too lazy to plug in their phones, but in doing so open up entirely
new possibilities in medical devices, remote sensing, and other areas.

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nardi
Does anyone know what happened to magneto-resonance? That sounded like the way
wireless charging was going to go a few years ago.

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zymhan
I had no idea Dell had a blog with actual writers.

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exo762
Dilemma, really?

noun noun: dilemma; plural noun: dilemmas 1\. a situation in which a difficult
choice has to be made between two or more alternatives, esp. equally
undesirable ones.

#firstworldproblems

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cmdli
Dilemma, noun (3b): a difficult or persistent problem.

[http://www.merriam-webster.com/dictionary/dilemma](http://www.merriam-
webster.com/dictionary/dilemma)

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interstitial
Seems like we can all just unshield our microwave ovens and fry two birds with
one dosage of cancer-inducing electromagnetic waves. Honey, dinner's ready and
your phone is charged. Little Alex is vomiting again and his hair is all over
my new dress!

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david927
That's what jumped out to me as well -- I have a huge concern for the
potential ill effects to the human body. Plugging in a device is not a huge
hardship and is vastly over-shadowed by the potential health risks.

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XorNot
It really isn't. For one thing, your body doesn't respond to magnetic fields
_at all_.

