Wireless Power Over Distance: Just a Parlor Trick? 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."
Re:Tesla (Score:5, Informative)
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:No it isn't (Score:3, Informative)
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 (Score:3, Informative)
Re:What about the dangers? Does it cause cancer? (Score:5, Informative)
(Emphasis mine.)
Re:No it isn't (Score:5, Informative)
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:Tesla (Score:5, Informative)
I'm waiting for my apology.
Re:Tesla (Score:4, Informative)
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.