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."
You can transmit power wirelessly over distances. (Score:2, Interesting)
...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.
No it isn't (Score:5, Interesting)
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:What about the dangers? Does it cause cancer? (Score:4, Interesting)
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:No it isn't (Score:2, Interesting)
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.
Re:As it was before (Score:5, Interesting)
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.