Slashdot Mirror
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."
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.
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.
Someone had to do it.
"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.
The Kruger Dunning explains most post on
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
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.
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.
SJW: Someone who has run out of real oppression, and has to fake it.
> 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.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"