See the book The Case for Space Solar Power or NASA's SPS-ALPHA project. Basic idea is a phased array microwave trasmitter, a transmitter on the ground that se

See the book The Case for Space Solar Power or NASA's SPS-ALPHA project. Basic idea is a phased array microwave trasmitter, a transmitter on the ground that sends a reference signal, and a receiving station that's basically several square miles of antenna wire, contributing 0.7 cents/kWh to the total cost.