Hacker News Reader

there is loss from the atmosphere when you beam it down

yes, but you can concentrate the beam more than sunlight so that there's less atmosphere involved. You can also choose a beam technology (wavelength etc) based on it going through the atmosphere well, rather than having to stick with sunlight's properties.

Not much, typically.

I think 60% over a kilometer is the best efficiency thus far.

What is the "typically" you are referencing?

Microwave beams are attenuated in heavy rain. Typically, the beam is not going through heavy rain.

The 60% over a kilometer is not due to atmospheric absorption, it's due to losses at the transmitter and receiver (and beam spread exceeding the size of the receiver.) If microwaves lost 40% of their energy in a kilometer radar would have a hard time working.

Millimeter waves are more strongly absorbed in clear air, so they are not as good for this use case. They may be good for powering aircraft.

Reply on news.ycombinator.com