> "Don't worry about getting zapped: Hall assures that the magnetic fields used to transfer energy are "perfectly safe" -- in fact, they are the same kind of fields used in Wi-Fi routers."
LOL. power transmitted by a Wifi router ~= mW. Power required for, even a low energy light bulb ~= 10W. The current draw in modern homes is so big that EM transmission, especially at sensitive wavelengths like microwaves, is highly likely to cook things (and people).
They may well have found a real way to make it work. But saying "it's the same as wifi" shouldn't convince anyone.
Also, static magnetic fields are conservative. You can't get energy out of them. The only way to get energy out of a magnetic field is by letting it change, which necessarily creates an electric field.
I sympathize with the need to find a way to explain how this could be safe, but they're stretching the truth. I hope it doesn't come back to bite them when somebody puts up a youtube video of cooking eggs on copper foil or something.
True, but its remarkable how constant the amount of electricity the 'typical' home draws, even as the things in it draw less. Things like the TV went from several hundred watts to only a couple of hundred, and then we added a home computer. I agree with the grandparent that you're not going to send a few kW of power into a house like this.
The other aspect that wireless power folks face is that any conductor now has a much more serious voltage potential on it. This can cause weird things to happen when dissimilar metals are suddenly energized. Electro transport can cause otherwise strong welds/connections to vanish.
> Dr. Hall, CTO WiTriCity:
> "We just don't think about it anymore: I'm going to drive my car home and I'm never going to have to go to the gas station and I'm never going to have to plug it in.
Count me as a wireless electricity skeptic, in general. But this claim is astounding to me.
I believe that if you placed a properly resonant circuit into an MRI device, for example, you could charge a decent sized battery (but probably not a vehicle propulsion battery) at a reasonable rate.
But it would be horribly inefficient and your car (and everything else in your garage) shouldn't be made of ferrous metal.
Cell phone batteries on little charger pads, sure. Maybe even via ambient EM, though I'm not convinced you could get regulatory approval above a certain emissions level (which, critically, has an inverse-square relationship to available current delivery capacity at the device).
But the article also talks about lighting and televisions, and cars. WiTricity has investors to fluff, clearly, but is this not absolute crazy talk?
The claim on their wiki page was a light bulb at 90% efficiency at 3 feet. If it's more efficient when closer, you could put one in the bottom of your car and one just below the surface of your garage, and you'd probably only have a separation of about 1 foot.
> But the article also talks about lighting and televisions, and cars. WiTricity has investors to fluff, clearly, but is this not absolute crazy talk?
They've apparently already powered lighting, and the TED talk supposedly had them powering a TV [0]
From what I've seen of their demos (going off memory), they focus on power transfer to a single device. Their efficiency drops to near 0% when multiple devices are being powered.
I have a hard time getting excited about these guys' work, but will readily admit they are excellent about generating publicity. There is a lot of _very_ closely related work in resonant energy transfer and use of time reversal or lensing currently being looked at around academia. Hopefully one day it will pan out, but it is never going to be as efficient as running a wire. For some applications wireless power is a great enabling technology, but powering a light or a tv in your home? That's a hard sell for the "convenience" of moving your tv versus the extra costs in energy inefficiency.
Ok, sure. If you can control the proximity carefully, you can achieve reasonable efficiency. Transformers work.
But it's still a super high powered magnet. There are more places than not where that's just a bad idea. Garages are high on that list. Also carports, kitchens, living spaces in general...offices, sleeping spaces..bathrooms. All bad.
LED lighting gets you pretty far down the current draw curve, but I don't see a small, easily moved coil generating enough resonant current to be useful in many common consumer electronics. That coil has to be plugged in to the mains, remember -- invalidating the promise of wireless power, even at three feet.
And ambient charging has all of those problems, squared.
Also, can't magnets interfere with pacemakers? "Oh, you have a pacemaker? Ya, don't come over or you will die... I don't want to have to plug in my lamps."
For cars is way more feasible just having two electrical-charged metal bars that always touch the underside of your car when is in the garage, and if they are far apart it's complete safe (i.e: children can't touch both at the same time)
Children may have pieces of metal such as bicycles, or they may walk across such bars while holding hands. I bet there are way more failure modes with such an approach (kids never drop buckets of water inside garages, for example)
You can also have a 4 heavy switches under the 4 wheels, that way a very heavy object (the car) must be there over all of them to turn on the electricity.
This looks interesting, but the conjectures people are making about pcell (the frontrunner for 5G cellular) being used for wireless power describe a more attractive solution.
They would provide power only to the area of space where the receiver is which first and foremost makes it inherently safer than a system which doesn't focus the power. I'm not going to claim I know much on the topic, but intuitively it would seem that the ambient power produced by the pcell transmitters would scale logarithmically with the power being transmitted.
But I trust that Witricity's produce is safe for most people since these things are highly regulated for safety. Perhaps more important to adoption is that the nature of Witricity's technology makes it impossible to selectively transmit power. Therefore, it would be impractical to charge a fee for using a power source. Pcell can do this, because it has to to be useful as a cellular technology.
I don't see a world where electric cars are charge wirelessly by beacons on roadsides, not at current electricity prices and the loss that would be involved, but I can imagine low power devices such phones and laptops becoming much more elegant through wireless power.
You can use a Crystal radio to power an LED, or a lot of things, the stronger the RF source, the more power you can extract. The problem is they aren't efficient if you are using them as a power source. When you are pulling "free" energy out of the airwaves they are cool, all that wasted AM band, but if you are broadcasting just to power your cell phone they are about .1% efficient. That's not a very eco-friendly.
Couldn't the wireless signal used to transmit energy be used to transmit data as well?
Anyway without a solid power source WiTricity would seem to be kinda non applicable for larger areas, but it's still good enough for small home chargers and stuff.
From what I remember about Tesla claiming that he would either use the ionosphere as a way to either amplify or bounce the signal. It's hard to separate fact from fiction with that man.
This is a very complicated problem. The length and orientation of the leads, type of pacemaker etc are all factors. And one mistake is one too many. This applies to a growing list of implants. Spinal cord stimulators, sacral nerve stimulators, deep brain stimulators, implantable defibs, cochlear implants, some hearing aids. Its a very long list. The possible complications are not just possible induced currents, but also heating. Many of the problems are covered here (although with MRI in mind) http://www.mrisafety.com. It's a great resource but is absolutely terrible to use and everything takes 20x longer than it should to find.
LOL. power transmitted by a Wifi router ~= mW. Power required for, even a low energy light bulb ~= 10W. The current draw in modern homes is so big that EM transmission, especially at sensitive wavelengths like microwaves, is highly likely to cook things (and people).
They may well have found a real way to make it work. But saying "it's the same as wifi" shouldn't convince anyone.