Re: Wasn't this in one of the Brosnan Bond films?
I think there will be three factors at play here; beam divergence, atmospheric attenuation, and collector efficiency.
If the beam divergence is kept low, and the collectors are wide enough to "catch" the whole beam, it’s not a problem. At the other end of the scale, if the transmission is omnidirectional, then the power drops off with the square of the distance.
Atmospheric attenuation depends on the wavelength used, the thickness of the atmosphere it will have to travel through (which will depend on the angle; directly above would be the lowest attenuation, and on the horizon the highest), and the weather - water vapour absorbs microwaves, to varying degrees, again depending on the wavelength, which is how a microwave oven works.
Collector efficiency is basically a measure of how much energy is captured by the receiver, which is effectively acting like an aerial. A quick google of the subject suggests that we can expect this to be better than 90%
So, judicious choice of wavelength, to avoid any major atmospheric absorption, and a well focused beam means it woudl hopefully be up to 90% transmission efficiency, which will be well above the actual efficiency of the solar panels themselves.
Biting the hand that feeds IT
