What a lame premise. Copper is a whole lot more than 20% efficient. I am also wonder what happens to living things when the beam passes through them. And any object could block the beam.
Living things? If it’s a strong beam, they’ll die. Unfortunately, the same fate awaits birds who fly into windmills. Any object can block the beam, and any numbnuts can move the object or move the beam.
I shorted copper yesterday afternoon. So far, no joy nor sorrow.