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Sony Prototype Sends Electricity Through the Air
itwbennett writes "Sony announced Friday that it has developed a prototype power system based on magnetic resonance that can send 'a conventional 100 volt electricity supply over a distance of 50 centimeters to power a 22-inch LCD television.' Unfortunately, Sony's prototype wasted 1/5 of the power fed into it and additional losses 'occurred in circuitry connected to the secondary coil so the original 80 watts of power was cut by roughly a quarter to 60 watts once it had made its way through the system.'"
The wasted energy is most likely dissipated as high frequency RF energy. In most primary/secondary coil designs (for the less enlightened... think Tesla coil), the bulk (80-90%) of "lost" energy is dissipated as high frequency RF. The rest is dissipated as heat and light.
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What took us so long?
Already sold as a product. http://www.thinkgeek.com/stuff/41/wec.shtml
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Every new house is required to be wired for smoke detectors.
Perhaps every new house, but mine certainly isn't. I have to change the 9-volts regularly.
Honestly, I can only think of one application where not needing a power cord for a 50cm distance is all that helpful:
Take a walk through your house some time, and look at every last little gadget in the house, and count how many batteries (replaceable or rechargeable, embedded or removable) you find. I bet you'll be surprised.
a "charging pad" to recharge your mobile devices by just setting it on the pad, without having to mess with wires and connectors. However, I don't think this is likely to happen for a long, long time
Huh? That's already here. And inductive charging has been used in electric toothbrushes for ages. The difference for this is that you actually have range.
I just invaded Grammar Czechoslovakia and duped Grammar Neville Chamberlain; now it's on to Grammar Poland.
A typical lightweight power cord is 16 AWG. 60 Watts (assuming good power factor correction) is 0.5 A. 16 AWG wire is ~ 4 mOhm/ft. So 4 ft of wire (2 ft cord, supply and return) is 16 mOhm. That means you're losing 8 mV of your supply voltage, or 4 mW of power. That's about 99.993% efficient.
You have to get significantly longer extension cord and put a lot more current through it before the power loss is relevant. Even if you used a 12 ft cord, and drew a rather significant 4A, that's still only 1.5W out of 480, or 99.7% efficient. And most extension cords are 14 AWG or thicker.
Nikola Tesla invented wireless electricity transfer at the turn of the 20th (yes, 20th) century. He was trying to prototype it by constructing what was called the Wardenclyffe Tower. Of course, everyone during that time thought he was a nut and the funding ran out.
Tesla is a candidate for the title of "smartest person who ever lived," and without him we probably would not have alternating current, which probably means we would get zapped much more often from our PCs (or "PMFs", i.e. Personal MainFrames). Now, considering the way society neglects its heroes of innovation, just watch Sony finish this and claim to have brought "wireless power" to the world, without ever having mentioned Tesla. "Oh yeah, him? Well we figured this out on our own. We just read a lot of these old books on magnetic resonance and pieced it all together. So smart is we!"
The first thing I did when I bought a house, was replace the existing smoke alarms with AC-mains wired ones. And yes they have a battery for when power goes out.
Costs $10-15 for one, plus the cost of having someone qualified to string wire across the attic to the units. This is more than the $20 each the subthread-poster wanted, but for the peace of mind it is very much worth it. (The original ones weren't well-placed and not fully up to code either.) Plus not having to worry about what kinds of RF is being thrown about or what else will it interfere with, now or in the future.