Wireless Power Over Distance: Just a Parlor Trick?

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."

Comments

this rock you rounded off is useless

[Anonymous Coward]

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

[MakerDusk]

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

[CanHasDIY]

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.

Re:As it was before

[Nidi62]

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

[Randle_Revar]

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

[geekoid]

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

Re:As it was before

[Anonymous Coward]

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

[Telvin_3d]

If anyone went through with this kind of thing they SHOULD be charged by the power sent. It is, after all, taking that much power to charge your device. The wastage is your problem for being too lazy to plug in your phone.

Re:Tesla

[Pentium100]

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.

No it isn't

[Sycraft-fu]

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

[Anonymous Coward]

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

[tuck182]

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

[Anonymous Coward]

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, 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

[Electricity Likes Me]

Yes, but what if you could induce lightning in a certain location, and then convert it into energy ?
All we need is something that can absorb the energy , and give it back at a slower rate later.

Much more interesting than wireless electricity.

The trick is to collect it before it turns into lightning. Stop it doing all that work on the atmosphere.

Superconducting helium balloons connected to clouds which discharge the current build up as it occurs gives you more manageable levels of current. The average potential difference between stratosphere and the ground is something like 300,000 V at all times, so even in clear air conditions you'd get some power.

At this point though, the volcano powerplant makes more sense.

Re:No it isn't

[WolfWithoutAClause]

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

Wrong!

That's how radio works.

Actually the resonant schemes DON'T use radio, they use inductance; which is just magnetic fields; and they work at much lower frequencies.

By contrast, radio is a particular mixture of magnetic and electric fields that propagate to infinity, and you tend to lose them. That was the genius of Marconi, to get the mix right.

But magnetic fields on their own don't propagate, that's partly why magnets don't go flat. The energy hangs around the transmitter and can be absorbed by a suitable receiver.

Re:No difference between power and radio

[skids]

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:Tesla

[Nidi62]

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:What about the dangers? Does it cause cancer?

[GoodNewsJimDotCom]

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?

[metaconcept]

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:unintended consequences

[kidaxess]

They are actually using the technology to power pacemakers. http://www.alansonsample.com/publications/docs/2012%20-%20ProcIEEE%20-%20Powering%20a%20Ventricular%20Assist%20Device%20with%20FREE-D.pdf

Ask 'em to put another load nearby

[HizookRobotics]

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.

Tesla Worship

[elrous0]

Personally, I think the Tesla worship among geeks has gotten WAY out of hand in recent years. Yeah, I know the Evil Rich Guy Edison vs. the Poor But Plucky Tesla makes for a great literary narrative. And I don't discount the guy's work (particularly with alternating current, which he was right to argue for over DC as a practical means of long range electrical transmission). But he wasn't a god, he wasn't 100 years ahead of his time (as some recent hyperbole would have it), he didn't invent anything which subsequent engineers haven't since replicated and improved on, and he didn't certainly didn't invent EVERYTHING (the list of claimed inventions seems to get longer every year, in spite of the fact that he remains decisively dead).

I think we do him an honor to recognize his REAL work. But we do him a dishonor to exaggerate, or even mystify, his accomplishments.

Re:Tesla Worship

[JBMcB]

For the record, that would actually be *consistent* with the claim that his patents and notes have been seized and kept classified. If you want to debunk the claim that something is being kept secret, you have to do better than, "I've never seen it.".

I'm not debunking anything as I don't have to. Some of Tesla's personal effects were seized by the government after his death and released to his nephew a few years later. Some of his documents went missing. It's possible that the government kept and classified them. It's also possible that they were simply lost, or stolen by someone else.

Now you need some back story. Tesla was a believer in aether theory - a theory that there was undetected type of matter that energy could flow through. These theories were shown false around the same time relativity was becoming popular (Tesla rejected the theory of relativity.)

If Tesla's dreaded beam energy weapon was based on the concepts of aether theory, the possibility of it working is basically nil.

So, what's more likely - Tesla was smarter than Einstein, Lorentz, Feynman, Hawking, Hubble, and a few hundred other extremely bright guys, understood physics in a manner unknown to all of mankind, and it's dumb luck that all our modern gizmos that depend on special relativity to operate function as they should.
Or - Tesla was wrong about relativity, his beam weapon never worked, and the papers about this weapon were lost somewhere?

Tesla was a certified genius. His contributions to electrical engineering are incalculably important. That doesn't mean he was infallible.

Re:Tesla

[girlintraining]

There's only one problem with people like you: You're always wrong. Tesla did do exactly what I said he did. Sorry it took me so long to check in and see some moron had gotten +5'd for handwaving while I got -1'd for telling the truth guys. Hopefully the mods will read the link and attached pictures and realize that yes, Tesla did have wireless power in the 1890s. Oh, and I was severely understating the distance: "Furthermore, the power loss experienced by Teslaâ(TM)s pulsed, electrostatic discharge mode of propagation was less than 5% over 25,000 miles. Dr. Van Voorhies states, âoe...path losses are 0.25 dB/Mm at 10 Hz,â which often is difficult for engineers to believe, who are used to transverse waves, a resistive medium, and line-of-sight propagation modes that can dissipate 10 dB/km at 5 MHz."

I'm waiting for my apology.

Re:Tesla

[Areyoukiddingme]

The problem with Tesla's system is the frequency on which it operates. 10 Hz has a wavelength of 34.73 meters. Properly receiving power at that frequency requires an antenna sized to match. Needless to say, it's not going into a handheld device. Tesla intended his system to be used in relatively large scale fixed installations. You could power your house with it, but the individual pieces of equipment in the house would be wired to the receiver. So yes, in theory his system could eliminate the grid as we know it and that does indeed address "power over long distances" as the headline does (really long distances). However, it's solving a different problem, that of very long distances using very large equipment, rather than the handheld gear over tens of feet as the articles are arguing over.