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Wireless Power Over Distance: Just a Parlor Trick?

Soulskill posted about a year and a half ago | from the efficiency-is-a-harsh-taskmaster dept.

Power 215

Lucas123 writes "Companies like U.S.-based WiTricity and China-based 3DVOX Technology claim patents and products to wirelessly powering anything from many feet away — from smart phones and televisions to electric cars by using charging pads embedded in concrete. But more than one industry standards group promoting magnetic induction and short-distance resonance wireless charging say such technology is useless; Charging anything at distances greater than the diameter of a magnetic coil is an inefficient use of power. For example, Menno Treffers, chairman of the Wireless Power Consortium, says you can broadcast wireless power over six feet, but the charge received will be less than 10% of the source. WiTricity and 3DVOX, however, are fighting those claims with demonstrations showing their products are capable of resonating the majority of source power."

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215 comments

this rock you rounded off is useless (5, Funny)

Anonymous Coward | about a year and a half ago | (#41835845)

i mean, the amount of effort it took you to make that rock round and then roll a log over it? you could have carried 10 logs in that time. quit with the making new shit, gorg, it isn't useful at all and it isn't like anyone will ever find a way to improve on it. ...
oh, nice vette, gorg.

As it was before (5, Insightful)

MakerDusk (2712435) | about a year and a half ago | (#41835851)

Back in the day, Tesla had achieved even greater success. Though if you can charge from anywhere, how can you be billed? That is what will permanently stop this type of technology.

Re:As it was before (1)

ChasmCoder (1818172) | about a year and a half ago | (#41835867)

I was just getting on to comment about Tesla. Here Here!

Re:As it was before (2, Insightful)

Anonymous Coward | about a year and a half ago | (#41836485)

You mean "hear, hear".

Re:As it was before (4, Insightful)

CanHasDIY (1672858) | about a year and a half ago | (#41835889)

Back in the day, Tesla had achieved even greater success. Though if you can charge from anywhere, how can you be billed? That is what will permanently stop this type of technology.

Exactly.

It's not that wireless power distribution is a "parlor trick" - rather, the problem is that the profiteers are doing it wrong.

No it isn't (5, Interesting)

Sycraft-fu (314770) | about a year and a half ago | (#41836131)

The problem is inefficiency. Power drops with the square of distance. That means you need a bigass transmission source to get a small amount of power any distance away, hence why things like FM stations have 5 digit wattage transmitters.

Yes we have been able to transmit power wirelessly for a long time, no it is NOT practical or efficient. If you are enthralled with Tesla, spend some time reading some actual books on him, not just the silly piece by the Oatmeal. He was a fascinating man and worth your time to learn about, but you need to learn about him if you want to go spouting off.

He didn't invent some magic transmission technology we can't replicate, he invented an inefficient transmission technology that we can replicate, but don't, because he was not able to solve the efficiency problems (and it may not be physically possible to).

Re:No it isn't (2, Informative)

StripedCow (776465) | about a year and a half ago | (#41836281)

Power drops with the square of distance.

Not if you have a directed beam of energy.

The beam could be directed based on some set-up protocol between the energy-source and the energy-consumer.
And you can easily direct beams by using some antenna array.

Such direction-sensitivity could also be used to (partly) solve the billing problem.

http://en.wikipedia.org/wiki/Antenna_array_(electromagnetic) [wikipedia.org]

Re:No it isn't (1)

bug1 (96678) | about a year and a half ago | (#41836403)

Power drops with the square of distance.

Not if you have a directed beam of energy.

An Antenna array is lots of antenna, and in each one "Power drops withe the squar of distance".

Re:No it isn't (0)

Anonymous Coward | about a year and a half ago | (#41836509)

Power drops with the square of distance.

Not if you have a directed beam of energy.

An Antenna array is lots of antenna, and in each one "Power drops withe the squar of distance".

You have to take the effect of interference into account. That's what the concept is based on.

Re:No it isn't (3, Informative)

Anonymous Coward | about a year and a half ago | (#41836429)

Even directed beams drop off with distance squared once you get outside the near field. A directed beam is a lot more efficient than an omnidirectional beam, but for any given directional beam, power will drop off with distance squared, and narrowing the beam will require larger antennas setups.

Re:No it isn't (0)

Anonymous Coward | about a year and a half ago | (#41837219)

ever heard of lasers? how about a radio wavelength laser?

Re:No it isn't (5, Informative)

Anonymous Coward | about a year and a half ago | (#41837655)

ever heard of lasers?

Or optical masers, as they used to be called!

how about a radio wavelength laser?

So, regular masers, then?

Okay, cool.

Now go read about diffraction [wikipedia.org] , and see if you can realize that lasers, masers, etc. aren't magic, and that every finite beam loses power like 1/r^2 in the far field.

Re:No it isn't (0)

geekoid (135745) | about a year and a half ago | (#41836543)

It'd not a billing problem. Billing is easy, your just auto subscribed if you are in their area. It's wold be a flat rate adjust at the end of the year. Billing is trivial.
As such, it isn't a billing problem. Electric companies would LOVE not to spend money one cables, poles and linemen.

Another conspiracy killed by common cents.
heh.

And you "solution" only underlines your ignorance.

Re:No it isn't (0)

Anonymous Coward | about a year and a half ago | (#41836359)

How about we refuse to accept the obvious ``this will never work'' and assume that ``some clever engineering will make it work''? Wireless power transmission is not impossible... heck, lightnining is pretty damn destructive, and manages to push a ton current through the air (a pretty damn good resistor under normal circumstances)---and somehow manages to avoid that whole square-of-distance thing (once arc is established).

Re:No it isn't (4, Funny)

tuck182 (43130) | about a year and a half ago | (#41836495)

I don't have any interest in carrying a phone in my pocket that's recharged via lightning bolt from the wall.

Re:No it isn't (1)

Hognoxious (631665) | about a year and a half ago | (#41836553)

"Sufficiently clever engineering is indistinguishable from magic, and there's fuck all in the cupboard."

L. Ron Hubbard's mother.

Re:No it isn't (1)

Type44Q (1233630) | about a year and a half ago | (#41836679)

Sufficiently clever engineering is indistinguishable from magic, and there's fuck all in the cupboard.

Now I remember one of the reasons L. Ron creeped me out so much: nobody ever cussed in one of his novels (people who never cuss - this includes authors - often give me the heeby-jeebies).

Re:No it isn't (1)

Anonymous Coward | about a year and a half ago | (#41836529)

The problem is inefficiency. Power drops with the square of distance.

That is a big simplification. The reason power drops with the square is because the surface area of a sphere increases with the square of the radius.
This is also true for segments so a reasonably directional power transmission also have this problem but you get a nice multiplier since you don't drop power in all directions.
If you make it unreasonably directional you can ignore the square of distance problem.

In the end it will always be a compromise of how well you can guide the energy to how far you want to transmit it and how large receiver you are willing to have.

Re:No it isn't (1)

Anonymous Coward | about a year and a half ago | (#41836559)

And also how deadly the line between the transmitter and the receiver.

Re:No it isn't (1)

Jah-Wren Ryel (80510) | about a year and a half ago | (#41836713)

The problem is inefficiency. Power drops with the square of distance.

That's when the transmitter is essentially a point source radiating in a sphere. I have a tiny bit of experience with very high powered radars that use beam-forming to narrowly direct their transmission. In the past that sort of beam-forming required lots of bulky equipment, but apparently that's changed in the last decade or so. I wouldn't be surprised if something similar could be used to direct wireless power with much better efficiencies.

Re:No it isn't (0)

Anonymous Coward | about a year and a half ago | (#41837673)

And yet, in the far field, that beam still gets wider in both directions as it goes, giving you R^2 fall off.

Physics doesn't say you can't transmit X power at Y efficiency over Z distance -- it just says the required antenna size scales with Z and increases with increasing Y. IOW, TANSTAAFL.

Re:No it isn't (2, Interesting)

Anonymous Coward | about a year and a half ago | (#41837679)

Beam forming is just the correct use of interference patterns, and it is very useful for *information* transmission, and an useless piece of crap for *power* transmission: you still leak power like a sieve. The math is not even complex, in fact it is downright simple.

The only way to increase efficiency is to redirect the wavefront and concentrate it where you need it instead of letting all that power go somewhere else it is not useful. This means you need to *reflect* it, maybe *guide* it (using waveguides). This is _not_ called "beamforming".

These companies are just promoting a major waste of power for absolutely no good reason.

not buying even if true (2)

hurfy (735314) | about a year and a half ago | (#41836717)

Looked at one of the demo videos. There is a 4000watt transmitter (in middle of floor, nevermind the radiated power someone is gonna trip on it!) a few feet away from most of the stuff and i don't see 2000w worth of stuff.

Don't know how it works, don't care so much to look. I don't plan on adding a 4000watt transmitter to each room, seems like a half dozen power cords would be a bit cheaper. Not that i have any interest or hope for anything called 3D power...sigh.

But...Does the green carpet in the one vid play into it? The TV didn't come on til he touched the floor.
Wonder how good the wireless internet is 18 inches from that transmitter where he set the laptop down.....

What if i add this 4000 watt transmitter to my apartment, as does my neighbor, etc. Before we finish the complex we will enough power running to add a couple TV channels much less the recievers :O

Re:not buying even if true (0)

Anonymous Coward | about a year and a half ago | (#41836833)

Yeah, companies should stop doing R&D until they can make a product that consumers will want to buy.

Re:No it isn't (1)

circletimessquare (444983) | about a year and a half ago | (#41836855)

tesla was the genuine article: a mad genius

so there's the genius

but there's also the crazy part to

Re:No it isn't (2)

hoboroadie (1726896) | about a year and a half ago | (#41837495)

I thought the resonating magnetic field solved the efficiency problem for Tesla.
These guys aren't charging the planet at the right frequency.

Re:Patent Wrappers & Colorado Springs Notes (0)

Anonymous Coward | about a year and a half ago | (#41837559)

I used to have some cool books from Yugoslavia, wish I could find them. As I remember, the big problem was ground conduction, as far as the losses went. The New York shore looked promising. -hoboroadie

Re:As it was before (1)

hoboroadie (1726896) | about a year and a half ago | (#41837617)

... if you can charge from anywhere, how can you be billed? That is what will permanently stop this type of technology.

Exactly. ... the problem is that the profiteers are doing it wrong.

J.P. Morgan figured he'd stick with the General Electric/Westinghouse business model and eschew the more efficient new technology, as it would not provide the market needed for his copper business.

Re:As it was before (1)

Anonymous Coward | about a year and a half ago | (#41835913)

That type of technology was (is and will ever be) stopped by the inverse square law. But I think that is the summation of idiots is high enough even the universal laws of universe can be bend in favor of marketing team.

Re:As it was before (0)

Anonymous Coward | about a year and a half ago | (#41837091)

Light also follows the law of inverse square, yet we have lasers of focused light beam.

Anyways, I doubt charging over distance is efficient/ works.

Re:As it was before (1)

Anonymous Coward | about a year and a half ago | (#41837249)

yet we have lasers of focused light beam.

Kind of helps that visible light has a wavelength around million times smaller than radio waves, so you could in principle make a quasi-optical beam that goes a million times further before diverging into a cone than a radio wave beam of the same size...

Re:As it was before (0)

Anonymous Coward | about a year and a half ago | (#41835993)

Well what's the equation for it? It doesn't have an equation, therefore it doesn't exist. The theory has to be invented before the phenomenon can exist you know and the theory can only be derived from existing principles all developed in the first half of the 20th century or earlier. Empirical observations and working technology mean nothing and any demo is a scam. /sarcasm (but the Slashdot hive mind wouldn't know it.)

Re:As it was before (3, Insightful)

Anonymous Coward | about a year and a half ago | (#41836585)

Well what's the equation for it?

You mean like Maxwell's equations?

Empirical observations and working technology mean nothing

You mean like the metric fuck ton of empirical observations related to electromagnetism in every day life and engineering done for a huge swath of technology? I've seen people on the internet claim to found disagreement with Maxwell's equations. Although it seems really funny that things I've designed and built that would be orders of magnitude more sensitive to the various deviations they show work exactly as predicted. Some people don't realize how many things around them wouldn't work if such things were incorrect in such a simple manner (as opposed to say QED effects that only are possible in extreme conditions in atomic/astrophysical/particle physics).

but the Slashdot hive mind wouldn't know it.

Yeah, I guess they are supposed to ignore their collective empirical evidence and just pay attention to yours. Only sheeple distrust things they see on the internet.

Re:As it was before (4, Insightful)

Nidi62 (1525137) | about a year and a half ago | (#41836049)

Though if you can charge from anywhere, how can you be billed?

Don't worry, I'm sure you'll be charged for the amount of power sent, and not the small amount of power received

Re:As it was before (4, Funny)

Randle_Revar (229304) | about a year and a half ago | (#41836497)

Yeah, and Tesla also cloaked a navy ship and accidentally sent it back in time! And the world is run by Illuminati Lizard-men!

Re:As it was before (0)

Anonymous Coward | about a year and a half ago | (#41837467)

Is it fun on ATS?

Re:As it was before (4, Insightful)

geekoid (135745) | about a year and a half ago | (#41836513)

No he did not.
Tesla needs props, but the Tesla myth does not.

Re:As it was before (0)

Anonymous Coward | about a year and a half ago | (#41837409)

This is medium-range transmission. A couple meters at the most.

unintended consequences (1, Funny)

magarity (164372) | about a year and a half ago | (#41835859)

Have they tested its ability to charge the phone of someone with a pacemaker or other medical device? Sure, it charged the phone, but he was no longer around to make a call...

Re:unintended consequences (1)

Farmer Tim (530755) | about a year and a half ago | (#41835987)

Sure, it charged the phone, but he was no longer around to make a call...

[marketing] So dispense with cables and increase time between charges.[/marketing]

Tesla (-1)

girlintraining (1395911) | about a year and a half ago | (#41835869)

Tesla figured out how to broadcast power miles away, wirelessly, using technology available in the late 1800s. People around his lab routinely reported switching off the lights in their house, only to find they didn't turn off. Six feet? I'll be impressed when it's ten miles -- that was the standard at the turn of the last century.

Re:Tesla (5, Informative)

Pentium100 (1240090) | about a year and a half ago | (#41835933)

You also have to consider the efficiency. Running a 1GW power plant just to light a 100W light bulb a few kilometers away does not seem a good idea.

Yes, it is possible to transfer power without wires - radio has been doing it for a long time (a simple crystal radio set does not need any power other than what it gets from the antenna, but you'd better have some sensitive headphones, a big antenna and a station that is relatively close). The problem is transferring a lot of power efficiently and without huge antennas.

Re:Tesla (2)

mike.mondy (524326) | about a year and a half ago | (#41836059)

You also have to consider the efficiency. Running a 1GW power plant just to light a 100W light bulb a few kilometers away does not seem a good idea.

Yes, it is possible to transfer power without wires - radio has been doing it for a long time (a simple crystal radio set does not need any power other than what it gets from the antenna, but you'd better have some sensitive headphones, a big antenna and a station that is relatively close). The problem is transferring a lot of power efficiently and without huge antennas.

Their claims are apparently that they can achieve better efficiency than had been thought possible.

Anyone who wants us to believe differently should have independently verified proof. If you suspect parlor tricks, it's helpful to have a magician involved in addition to the scientist or engineer. "Extraordinary claims" and all that...

Or maybe a bad summary? Almost 50% loss over a relatively short distance might match the claims of "majority of the power".

Re:Tesla (1)

mZHg (2035814) | about a year and a half ago | (#41836159)

This has already been done, on few hundreds meters using big directional antenna in area where you can install wires. I just cant remember where it was.. A tv documentary I've seen 10 years ago at least. Somewhere in south America, to power some scientists observatories or alike.

Re:Tesla (2)

mZHg (2035814) | about a year and a half ago | (#41836433)

"Wireless high power transmission using microwaves is well proven. Experiments in the tens of kilowatts have been performed at Goldstone in California in 1975 and more recently (1997) at Grand Bassin on Reunion Island. These methods achieve distances on the order of a kilometer."

http://en.wikipedia.org/wiki/Wireless_energy_transfer#Microwave_method [wikipedia.org]

Re:Tesla (0)

Anonymous Coward | about a year and a half ago | (#41835977)

Did his plan not come to fruition? If you notice, earth return power systems travel miles and miles and miles through the ground without wires to get back to the source (aka the power plant). I can go to the local airport and view information regarding large amounts of power emitted out into the air, which is called radar.

Re:Tesla (0)

Anonymous Coward | about a year and a half ago | (#41835983)

Tesla didn't have to worry about FCC regulation on how much RF power he could transmit on his coils back then in the dark ages before wireless communication,

Re:Tesla (0)

CanHasDIY (1672858) | about a year and a half ago | (#41836039)

Tesla didn't have to worry about FCC regulation on how much RF power he could transmit on his coils back then in the dark ages before he invented wireless communication,

CTFY

[Clarified That For You]

Re:Tesla (2)

geekoid (135745) | about a year and a half ago | (#41836643)

he didn't invent wireless communication.
look up photophone (1880)
or
David E. Hughes 1889
or
  Heinrich Hertz
or
Chandra Bose

One popular comic ass talks about Tesla, makes factual wrong statements about Tesla, and every self proclaimed 'nerd' starts repeating it like it's actual fact.

hah, my bad for forgetting (0)

geekoid (135745) | about a year and a half ago | (#41836689)

Marconi and Braun, Nobel prize winners. Tesla was like 10 when they did this.

Re:Tesla (0)

Anonymous Coward | about a year and a half ago | (#41836051)

We can do the exact same thing now if you want to waste power. Actually, there's an article about that, right above. Tesla didn't discover some kind of black magic no one knows about. The physics he used are well understood today.

Re:Tesla (0)

Anonymous Coward | about a year and a half ago | (#41836283)

Source? Don't believe it.

Re:Tesla (0)

Anonymous Coward | about a year and a half ago | (#41836287)

Yes !
A technology lost and locked down.
Why was his info "Illegally Seized " a at the time of his death and is still not known today ? Tesla was experimenting with Plasma, the arc from which has a tiny resistance which can carry huge Currents short distances , This however ,Tesla accomplished over huge distances .
Today this is done inside Gas filled discharge tubes like Xenon and Neon lamps , except Tesla figured out how to ionize the air (Nitrogen/oxygen) into a plasma over huge distances in a controlled manner like Lightning on demand.

Re:Tesla (1)

Lunix Nutcase (1092239) | about a year and a half ago | (#41836331)

How was it lost? We know exactly the physics behind his transmitter. There was nothing magic about it.

Re:Tesla (0)

Anonymous Coward | about a year and a half ago | (#41836521)

It was Lost.
We don't know it.
  The textbook physics we learn in school may not be what Tesla accomplished.

Re:Tesla (1)

Desler (1608317) | about a year and a half ago | (#41837337)

Yeah because he used some different form of physics not available in our time, right?

Re:Tesla (4, Funny)

Nidi62 (1525137) | about a year and a half ago | (#41836557)

Why was his info "Illegally Seized " a at the time of his death and is still not known today ?

I'm not saying it was aliens....but it was aliens.

Re:Tesla (0)

Anonymous Coward | about a year and a half ago | (#41836799)

Assuming you could ionize air in any shape on demand, at no cost for control circuitry or inefficiency for getting that shape, consider making just a 1 meter long, 1 mm square section of plasma. You would need a joule of energy just to strip the electrons off about 1% of the nitrogen to get the ionization typically seen in an arc (more would lower the resistance), without any power going into heating or radiated light (which is actually a large percentage of the power used in an arc). If we are very generous and give a recombination time of about a millisecond for such a thin strip of plasma in air, you would get a need of about 500 W just to keep it ionized. This is going to cut into your efficiency and gets worse with longer distances. You could try to save some power and go with short bursts instead of a constant DC discharge, still having to pay for the ionization every time (plus heating and radiative loses in the real world). If you wanted to limit your loses to about 10%, you would need to send ten times as much as the ionization energy every burst, and be done before it recombines much... using the above numbers, you would need to transmit in bursts of at least 10 J/ms -> 10 kW. That is going to add a few more layers of complexity and potential loses to your setup, even ignoring a bunch of other sources of inefficiencies already stated above, and others.

Re:Tesla (1)

Lunix Nutcase (1092239) | about a year and a half ago | (#41836299)

Yeah and? You realize that most of the power was lost before being received over that long distance, right? Tesla didn't break the laws of physics despite what his modern-day, rabid fans would have you believe.

Re:Tesla (2, Insightful)

geekoid (135745) | about a year and a half ago | (#41836589)

"Tesla figured out how to broadcast power miles away, wirelessly, using technology available in the late 1800s. "
STOP IT. this is a false statement. Tesla went bat shit crazy, and made shit up.
Yes he was a genius and found out how to do some great stuff. Lets celebrate that and not the Bullshit myth.

I'll be impressed when you idiot can start to separate fact from fiction.
And before you replay, if such a device existed, billing would be trivial. IT's like people really ignorant of electrical engineering and Billing practices came together to fall under a conspiracy theory instead of ACTUAL THINKING about it.

There are many ways to bill, but I will sum up with an example:
I pay for sewer, yet there is no Sewer meter on my sewer line.

Re:Tesla (1)

Desler (1608317) | about a year and a half ago | (#41837343)

But...but...the Oatmeal guy said it so it must be true!!!

Re:Tesla (0)

Anonymous Coward | about a year and a half ago | (#41836653)

Is this really true? If so why has no-one else worked this in a whole century?

Also would you want you lights to be on permanently and presumably all your delicate consumer electronics constantly being wrecked from all the induced current?

Not a Parlor Trick (0)

Anonymous Coward | about a year and a half ago | (#41835877)

Very cool actually, if we can ever direct magnetic waves into a coherent beam like form cheaply and conveniently. Right now wireless power charging radiates much like light from a lightbulb, the amount of energy your device receives drops off exponentially as you move away from the charging coil. And any of that energy that's not charging something is wasted.

If we can, so to speak, target individual devices, and bring the resulting energy transfer up to acceptable levels of efficiency at a good distance then we'll be good. Because if you have to have your device sitting very close to specific spot then there's not really much point in not just plugging it in.

Still... (1)

Anonymous Coward | about a year and a half ago | (#41835879)

... the marketing department and the vaporware wizard are trying to mess with inverse-square law.

Re:Still... (1)

archshade (1276436) | about a year and a half ago | (#41836745)

The inverse square law only holds if the the transmitted signal is divergent. If you imaginge a singlepoint that transmits power in all directions equally then you can imagine the power delived as being a series of concentric spheres then the the total power is equal for each sphere. but the power density is the total power divided by the area of the sphere.
ie.
collectable power = (area of pick up device*Power transmited)/4*Pi*distance from the transmitter^2
However if you can make a beam like transmission path the then the area never diverges your power density will never drop. I have no idea how you would even start to do this but if you had a transmitter that sent out a cone rather than a sphere then you could make significant improvements.
collectable power (area of pick up device*power transmitted/Pi (Tan(1/2 theta) * distance to transmitter)^2.

This would all work with an infinatly big plane.

Re:Still... (1)

Anonymous Coward | about a year and a half ago | (#41837011)

An infinitely long, non-divergent beam in homogenous material is incompatible with Maxwell's equations. Beyond some problem specific distance, all forms of electromagnetic transmissions will drop off with inverse square or worse. Typically, that distance is on the order of a wavelength or two, or the Rayleigh length in some better designs that using antennas/optics many times larger than the wavelength.

Re:Still... (1)

Jeremi (14640) | about a year and a half ago | (#41837647)

However if you can make a beam like transmission path the then the area never diverges your power density will never drop. I have no idea how you would even start to do this

I believe the device you're thinking of is a laser.

Bloody Parlor Trick! (0)

Anonymous Coward | about a year and a half ago | (#41835885)

at least until there's a patent on it. *runs, ducks*

No difference between power and radio (0)

Anonymous Coward | about a year and a half ago | (#41835911)

Give or take a few details, radio waves and wireless power behave pretty much the same. For a signal source that broadcasts in all directions, the signal strength necessarily will drop proportionally to the square of the distance. The only thing that can prevent this is when the signal is made to be directional, e.g. by broadcasting it from the focal point of a parabola and aiming it at another parabola where it's collected at the focal point again. If you don't make your power signal directional, most of the power is just gonna leak away into the atmosphere.

With regards to using a parabole to make the signal directional... note that a parabolic shape may not necessarily be needed. Since the power signal is an electromagnetic wave, perhaps the power signal can be made directional using the electromagnetic equivalent of a fresnel lens. So I wouldn't be as fast as to discard the possibility straight away.

But accomplishing high efficiency by simply embedding a run-off-the-mill charging pad in a concrete wall? Fat chance.

Re:No difference between power and radio (5, Insightful)

skids (119237) | about a year and a half ago | (#41836269)

If you don't make your power signal directional, most of the power is just gonna leak away into the atmosphere.

This is not how these devices are supposed to work... that is to say, this is not the same as radio. It's a near-field, not radiative, effect. Most of the power that does not go into the receiver returns to the transmitter as part of the resonant oscillation (via a collapsing magnetic field.) Some will be lost to fringing, but the percent lost to that per oscillation is much lower than the percent absorbed by a properly tuned receiver, by design.

Not that I'd advocate this for consumer use, it will still be less efficient than a wire, and I'd rather see consumers suck it up and run a wire where appropriate instead of finding yet one more way to waste energy and pile ruin on our planet. However there may be some very productive niche uses.

Re:No difference between power and radio (2)

Lehk228 (705449) | about a year and a half ago | (#41836395)

the only way to make this efficient is to make the format mandatory and exclusive, every single device must be compatable with every other, that way battery powered devices no longer need charging cables packed in, the expectation is that you have a charging mat.

no more car chargers, no more wall wart chargers, no more devices disposed of due to worn out charger connections.

make sure all are compatable, or near compatable with only variability being amperage output, clearly marked on chargers and minimum to charge marked on all devices.

Re:No difference between power and radio (0)

Anonymous Coward | about a year and a half ago | (#41836805)

So you want your mobile phone charger to be compatible with charging your electric car!?

Re:No difference between power and radio (1)

skids (119237) | about a year and a half ago | (#41837599)

no more car chargers, no more wall wart chargers, no more devices disposed of due to worn out charger connections.

However this problem could be fixed without ever leaving the wired space. To some extent, it is already being fixed with USB, but for higher power devices, PoE/PoE+ might be a good thing to encourage, even for non-networked devices.

Now if we could just get them to stop changing the damn connectors all the time.

Re:No difference between power and radio (0)

Anonymous Coward | about a year and a half ago | (#41836669)

For a signal source that broadcasts in all directions, the signal strength necessarily will drop proportionally to the square of the distance. The only thing that can prevent this is when the signal is made to be directional, e.g. by broadcasting it from the focal point of a parabola and aiming it at another parabola where it's collected at the focal point again.

Directional broadcasts are subject to the inverse square loss too at some point, as an infinitely long, non-divergent beam is not a valid solution of Maxwell's equations. Once you get beyond about the Rayleigh length (or a wavelength, if larger) from an antenna, it is going to look pretty much conical in shape and drop off with square of distance. For a ten centimeter antenna setup with something like 2.4 GHz wireless, you would get inverse square drop off beyond 10-20 cm (or say beyond 10 m for a 1 m antenna setup).

Inductive charging pads (2)

MichaelSmith (789609) | about a year and a half ago | (#41836009)

I think these are a great idea and I would not be surprised if Apple start to support them in the future. A phone could be built with no open connections at all. Just wireless data and inductive charging. But over longer distances the laws of physics catch up with up. Obviously the shorter the wavelength the less doffraction you get over a given distance so if you direct power with a laser and convert it into electricity with a photovoltaic cell then you could easily get more efficiency over a few metres than with induction. Maybe in the future it will be considered normal to transmit power that way.

Re:Inductive charging pads (0)

Anonymous Coward | about a year and a half ago | (#41836243)

inductive charging coils might become a standard feature, I hope. I know my hp touchpad does it, and so does the new nexus 4. The mats themselves aren't cheap, which could be why the tech is so slow to be adopted.

You can transmit power wirelessly over distances. (2, Interesting)

Anonymous Coward | about a year and a half ago | (#41836017)

...but, the further you go the more it resembles eating your lunch sitting on power lines.

At the one end, there is no measurable danger in charging handset on a pad charger. But do you really want to spend all your television watching hours in a room where 200 watts of power is being beamed to your TV (and 19x being radiated) from the wall to save you the bother of the unsightly cord?

If you have magnetic wave energy, you have electric wave energy, which means you have RF. You can shape the way you transmit RF energy, but there are no perfectly absorbtive receivers, and splatter is a function of distance. So at contact distance (phone on the pad) it's pretty fine.

The claim was "most"of the power gets there. Let's assume they are not full of crap. So 49% of the power is splatterd around. So your 1800 watt cordless hairdryer splashes 1730 watts around the bathroom? And people worry about .1 watt GSM transmitters in their phones?

I guess I need you to trust an A/C on this point, the extra four orders of magnitude makes a difference.

What about the dangers? Does it cause cancer? (1, Troll)

GoodNewsJimDotCom (2244874) | about a year and a half ago | (#41836355)

They've seen people who live under high voltage power lines seem to have a higher rate of cancer [stanford.edu]

So I would think it would be possibly dangerous to come close to fields where energy is passing through your body. The more energy involved the worse off I'd think people would be. I don't tend to worry much about low energy fields like cell phones or wifi. Yet if a job powered all the computers with remote energy so I'm exposed all day long, I'd have to decline that job. No sense risking cancer for any amount of money.

Re:What about the dangers? Does it cause cancer? (0)

geekoid (135745) | about a year and a half ago | (#41836651)

" The more energy involved the worse off I'd think "
sigh. Do you lack all critical thinking capability? DO you often speculate about things you are ignorant about? Just say in thing that pops into your head?
Do you even know what energy is?
Sheesh.

Re:What about the dangers? Does it cause cancer? (3, Interesting)

GoodNewsJimDotCom (2244874) | about a year and a half ago | (#41836729)

Watts = Volts x Amps. Watts is energy per unit time... My thinking is that higher Watts(higher energy) is worse for you than low energy transfer like radio/Cell/Wifi.

My reasoning is that people who live near high power lines develop cancer at a higher rate than the general populace, while people using regular electronics and in home wiring systems don't get impacted as bad.

Re:What about the dangers? Does it cause cancer? (0)

Anonymous Coward | about a year and a half ago | (#41837503)

That reasoning would be great if it didn't rely on data that doesn't exist. You might as well say that your reasoning is that people who masturbate go blind at a higher rate than the general populace. I mean, that's not true either, but it sounds good right? No?

Re:What about the dangers? Does it cause cancer? (5, Informative)

metaconcept (1315943) | about a year and a half ago | (#41837001)

From the very PDF you link to, Question 1, right at the beginning:

  • the more recent epidemiological studies show little evidence that either power lines or "electrical occupations" are associated with an increase in cancer (see Q19);
  • laboratory studies have shown little evidence of a link between power-frequency fields and cancer (see Q16);
  • an extensive series of studies have shown that life-time exposure of animals to power-frequency magnetic fields does not cause cancer (see Q16B);
  • a connection between power line fields and cancer is physically implausible (see Q18).

... Overall, most scientists consider that the evidence that power line fields cause or contribute to cancer is weak to nonexistent.

(Emphasis mine.)

Re:What about the dangers? Does it cause cancer? (1)

MangoCats (2757129) | about a year and a half ago | (#41837449)

Or, maybe they're happier [nih.gov] ?

Propagation, Dissipation, and Inductance (2)

some old guy (674482) | about a year and a half ago | (#41836387)

I'm as big a Tesla fan as anyone, but I'm also a practical electrical engineer.

Someone above already raised the end-point billing issue the utilco's will have, so we needn't bother with the bean-counter side of things. MBA's, rest easy. Your obscene profits are safe.

However, going from a theoretical ability to blast x amount of joules across an air gap to capturing a useful fraction of x without frying the adjacent wildlife and neighbors is quite another thing. As TFA points out, they seem impressed with a 10% capture rate, which to an engineer means a 90% loss of efficiency.

There is also this unpleasant fact of biophysics: sufficiently strong electro-magnetic fields, regardless of frequency, are inevitably fatal. The required grounding, shielding, etc. would be so outrageously expensive that the cost of copper wires pales.

Some science fiction does eventually become science fact. However, Thermodynamics, biochemistry, and basic engineering discipline relegate most of it to forever remaining fiction. Sorry, no Nobel Prizes here.

Re:Propagation, Dissipation, and Inductance (0)

Anonymous Coward | about a year and a half ago | (#41836603)

Everyone is going right to power over miles. Think smaller. The problem with electric cars is battery tech. Why not embed these in the roads and put a capture plate (or whatever it's called) on the bottom of the car? You'd have a battery for when the connection wasn't good or what have you, but you wouldn't need a ton of batteries. The distance wouldn't be much.

The cost counting is an issue. However, why not use a device like Geico uses? It would just read the amount of power you use and uploads it via cell signals and keeps count. If you tamper with it or damage it the result is the same as if you damaged your power meter on your house. Basically, it's a huge cost to you regardless of what you used.

Re:Propagation, Dissipation, and Inductance (1)

geekoid (135745) | about a year and a half ago | (#41836663)

There is no billing issue. Billing would be easy.

RFID powers at 30 +ft (0)

Anonymous Coward | about a year and a half ago | (#41836459)

The error in the critics is that they are talking about magnetic/induction.
RF information (and thus power) can travel over E fields as well.

As for focusing the beam - that is called antenna gain. Higher gain antennas have greater focus.

Higher frequency is easier to focus than lower frequency.

In the case of RFID, at 900Mhz, 1 Watt of power, and 6db gain antenna, you can power an RFID tag at 90ft! - a larger 6x6" tag - with a metal back plain.
Yes there is loss - lots of it in fact - but it can work. The more common, 10cent tags are on the order of 20ft (same chip - just efficiency of the receiving antenna).

There are practical limits on how much gain a planer antenna can have.

Go back and read that web site again (0)

Anonymous Coward | about a year and a half ago | (#41836615)

>Menno Treffers, chairman of the Wireless Power Consortium, says you can broadcast wireless power over six feet, but the charge received will be less than 10% of the source.

He is correct, although you don’t provide any details of his exact statement. If you built a complete sphere around the transmitter you could theoretically get far more than 10% of the source, but he is probably assuming a much smaller antenna 10 feet from the transmitter. Most of the power from the transmitter is not going anywhere near the antenna and therefor can’t be transmitted even if the antenna is 100% efficient.

>WiTricity and 3DVOX, however, are fighting those claims with demonstrations showing their products are capable of resonating the majority of source power.

I don’t think you read the page you linked to very carefully. Where does 3DVOX say anything about “resonating the majority of a source power?” They are just stating they can power some household electronics and make no claims whatever about the efficiency of their system. The Witricity doesn’t make any claims about efficiency either. If you want to buy their “Prodigy” system for a thousand bucks and light up some low-power LEDs a few feet from a transmitter, you go right ahead. Even there promotional page just says you can send power through a “desk top, glass window, (or) a brick wall.” That’s quite easy. Sending it though 10+ feet of space, that’s the hard thing.

In my book, lighting up a few LEDs is exactly the kind of thing I consider a nice "parlor trick."

Sounds like the typical scam gobble-de-gook (0)

Anonymous Coward | about a year and a half ago | (#41836655)

"...capable of resonating the majority of source power."

Where are the "hyperreality" and "quantum continuity" marketing scam words so popular on other idiotic claims?

Are there no "ethereal vibrations" or "ionized ions" or "magic ponies" in the announcement?

I guess it's time I throw away my EE texts...and, for that matter, Physics texts, eh?

lasers (0)

circletimessquare (444983) | about a year and a half ago | (#41836871)

why can't they transmit it with lasers

(mental image of toddler looking into the power transmitter)

never mind

Re:lasers (0)

Prof.Phreak (584152) | about a year and a half ago | (#41837297)

Hmm... how about a laser beam of much longer wavelength---like radio, or even much lower (e.g. say 60Hz---but just as directional as a laser)?

Confusing magnetic resonance and radiated RF power (2)

kidaxess (634347) | about a year and a half ago | (#41836993)

There seems to be some confusion on this thread between magnetic resonance, which is the type of power transfer used by WiTricity and others, and radiative RF which is the radio technology we are used to. For example, received power does not fall off with the square of distance in the case of magnetic resonant systems. There are definitely a ton of challenges to this technology, but it is good to keep in mind that they are NOT talking about transmitting a high power RF signal and having it received at range. Here is a link to a paper that describes both types of systems so you can understand the implementation and trade-offs. The author's have achieved 80% efficiency over a few meters using magnetic resonance. Experimental Results with two Wireless Power Transfer Systems http://sensor.cs.washington.edu/pubs/WISP-WARP.pdf [washington.edu] Video and other good info: http://www.alansonsample.com/research/wrel.html [alansonsample.com]

Re:Confusing magnetic resonance and radiated RF po (2)

kidaxess (634347) | about a year and a half ago | (#41837041)

The referenced paper actually describes two systems based on RF power transfer. Here is one on magnetic resonance: http://www.alansonsample.com/publications/docs/2010%20-%20TIE%20-%20Magnetically%20Coupled%20Resonators%20for%20Wireless%20Power%20Transfer.pdf [alansonsample.com]

Chapter 4 of the ARRL Handbook (1)

calidoscope (312571) | about a year and a half ago | (#41837521)

Chapter 4 of the ARRL Handbook has a section on coupled resonant circuits. The critical coupling coefficient is equal to the inverse of the geometric mean of the loaded Q's of the two resonant circuits. With the coupling coefficient dropping with the 6th power of the spacing, once the spacing significantly exceeds the radius, the required Q's really quickly become unrealizable.

Re:Confusing magnetic resonance and radiated RF po (0)

Anonymous Coward | about a year and a half ago | (#41837637)

No matter what kind of technology is used in the antennas a local RF magnetic field is produced. This will necessarily cause induction currents in any exposed conductors. In MR systems these currents are always supressed by special traps inserted over all electrical conductors in the proximity of the transmission coils. A cable without supression devices can become a focussing device for RF fields and cause high SAR. Why should we accept high SAR from this tech but at the same time be wary of SAR effects from cell phones?

A home equipped with long distance wireless power transfer antennas would need to have supression devices inserted on any and all cables that can be brought near the transmission antennas. This is impossible to guarantee. A mismatching or non-supressed cable could become a fire hazard due to uncontrolled induction heating. I have seen this happening in MR systems.

some basic scienc (0)

Anonymous Coward | about a year and a half ago | (#41837165)

If you want to avoid 1/r^2 effects you need a beam. You won't get that with 60 cycles/sec power; wavelength is too long and a transmitting array will be too unwieldy. Microwaves can be beam-formed. However, if your beam is carrying, say, 1KW of power in a narrow beam, the power density is going to become large. You like to run your microwave oven with the door open? No? Right: the power density could become dangerous. You'd need some way to power your computer, lights, engines, whatnot, with no coupling of that power to flesh. That's tough: we conduct electricity pretty well at most any frequency. Then too these narrow beams need to be aimed at whatever is to be charged. You don't just carry your devices into the house and they magically get power.

If you can do the "get power anywhere" trick, they're not using a directional beam. They won't survive distance power loss either, and you would want to be careful about spending time in the area. If they can do distance, the energy must be concentrated into a beam or narrow area. (It is easier to achieve this with the technical marvels called "wires".) If the beams are sent through free space, caution is advised in crossing such beams. Remember the microwave open-door example again...those devices work by dumping lots of EM energy into a region of space. A power beam would be such a region.

It could get hot to be in such. Might ignite walls too.

Coming soon (0)

Anonymous Coward | about a year and a half ago | (#41837277)

Wireless power extension cords.

Ask 'em to put another load nearby (3, Insightful)

HizookRobotics (1722346) | about a year and a half ago | (#41837397)

There are a lot of hard engineering problems to overcome, even if the system was efficient... For example, a second resonant load nearby severely de-tunes the system, antenna mounting considerations are of supreme importance (good luck putting one on a laptop full of metal), and antenna alignment is absolutely crucial! The whole WiTricity concept might be sound in theory, but the engineering challenges are monumental.

MR imaging, SAR limits and patient burns (0)

Anonymous Coward | about a year and a half ago | (#41837547)

Anyone interested in wireless power transfer should look into Magnetic Resonance imaging systems. They are doing excatly the same thing ie transferring large amounts of rf energy through air into the patients undergoing examinations. One of the most difficult problems is keeping the patients cool during the imaging. The rf fields cause local induced rf currents in patients and is some cases these result in burns. The fields are generated by antennas similar to the ones they are using for wireless power transfer.

It requires a lot of work to supress the induced rf currents even in the highly controlled environment of a MR imaging system. No external conducting wires are allowed anywhere near the transmitting coils. This includes conducting surgical equipment etc. There is a lot of education for the nurses before they know what can and what cannot be done inside the volume exposed to rf fields. Anyone claiming that the same problems would not appear in home or office environments is lying or does not know what he is talking about. I have seen sparks flying and plastic insulaton of the cable melting when a cable without rf supression devices was used...

I have designed rf coils in MR systems for > 10 years. If there was an easy way of handling these problems I'd heard about it by now. Ask them about the SAR http://en.wikipedia.org/wiki/Specific_absorption_rate for humans close to the wireless transmission coils. Does the system fulfill the SAR limits for general public? Do not accept anything but specific and definite answers to the regulatory questions before even considering to invest into this kind of tech.

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