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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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Already sold as a product. http://www.thinkgeek.com/stuff/41/wec.shtml
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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!"