On the left: Part of the solar energy is lost on its way through the atmosphere by the effects of reflection and absorption.
On the right: Space-based solar power systems convert sunlight to microwaves outside the atmosphere, avoiding these losses, and the downtime due to Earth's rotation, experienced by surface installations.
This is what an artist envisioned the Solar Power Satellite would look like. Shown is the assembly of a microwave transmission antenna. The solar power satellite was to be located in a geosynchronous orbit, 36,000 miles above the Earth's surface.Nasa 1976