The satellite would convert the solar energy to microwave and beam it directly on line to receivers at certain main power plants, who would convert it to electricity and send it to regular power plants.
To transmit solar energy to space craft they propose using radio frequency or laser beams.
I couldn't find the reference to the beam to Earth being microwave, but I remember that was what was proposed back in the late 1980's when I was a sustaining member of the organization and helped fund their research.
Microwave energy beam from space solar satellite could heat water here on Earth and steam driven turbines could generation electricity to send to regular power stations, is what I recall.
Dr. Gerald O'Neill's untimely death in 1992 took a lot of the steam out of his drive to make these satellites a reality. He had invented a GPS system and was on the Ariane launch schedule to get a GPS satellite privately owned by SSI up in the early 90's to be a money maker to help fund the solar satellite project.
I don't know what happened to that all upon his death as I was deep into starting my own practice at that time and lost track of his work, and didn't hear of his death till years later.