Space Mirrors

Sunlight, with a broad spectrum of much shorter
wavelengths that those used for power transmission, is
scttered by interaction with dust and H2O in earths
atmosphere, thereby severly reducing the amopunt of
energy that actually makes it to the earths surface.
Light intensity above earths atmosphere is 1450 watts
per square meter. By the time it makes it all the way
to the surface, on a clear, cloudless day, it's
reduced in intensity to about 1/4th that value. With
clouds it drops much furthur. Short radio waves are
not so absorbed, with better than 90% of the beamed
energy making it to the earth based receivers.