[DennisP]

Based on a book I read on the subject, there's a way to make a phase-array microwave transmitter, which achieves the required focus by tuning into a reference signal from the receiving station on Earth. Using this system, if you try to transmit to an arbitrary spot you'll have a much more diffuse beam, and even the tight beam is only concentrated enough to raise the temperature several degrees. The receiving station is about the size of a ground-based solar array, but cheaper because it's just microwave antenna.

Another approach is to use a laser, at a frequency that gets absorbed by the atmosphere. Beam it to a high-altitude receiver station, which beams microwaves to a receiver directly below. But that way is a lot more expensive.

https://www.amazon.com/Case-Space-Solar-Power-ebook/dp/B00HN...