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Wireless power transmission test video

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Let's do a little math. The surface of a 4.1km radius sphere (=4 pi r^2) is about 211 million m^2. If the transmitter is putting out 50kW then the flux at 4.1km is 50kW/211 million m^2 = 0.2 mW/m^2. He's clearly not covering a square meter of air, so he's probably generating a few tens of microwatts.

Solar flux at earth orbit is 1.4kW/m^2 (I think, I'm getting that number from memory). Lots of that is lost in the atmosphere, and half of it happens at night, plus Seattle's at 47 degrees latitude, so it loses some due to the light coming in at an angle. Say that 10% makes it to his rooftop, averaged over a year. That's still 140W/m^2, or a little less than a million times the RF he's getting. So using a standard calculator-style solar cell and some storage to handle night (probably a cheap capacitor, since it doesn't have the charge/discharge lifecyle problems that batteries do and would be storing only a couple of joules total) would be a much more sensible solution.

But, as stunts go, it's still pretty cool.
 
Antron, wireless power is different from that of the "free energy scamsters."

There is nothing (that I know of) that can beat the efficiency of energy transit through the wire. When wireless gets up to 90 - 97% efficiency, then it's good. Too bad it will not, for any practical distances to replace power lines. Using it to "wirelessly" charge your gadget by placing your gadget on a coil is not wireless, but more like plug-less.
 
I agree with you Anton. But the emphasis here is different. The point is that the devices use so little power than they can run off radio waves in the air. As dpeilow says, it's like the crystal radio kits we used to build as kids. You could listen to the radio with no internal power of amplification.

Not that it's terribly practical, but it is a neat trick.
 
I don't think it makes a whole lot of sense for a stationary, semi-permanent installation like a wall mounted TV set. Run the power in the wall if you really want that clean look. I can see the convenience factor for certain devices, though. Palm Pre is an example.