What it is
Space-based solar power (SBSP) would collect sunlight in orbit and send energy to Earth as microwaves or lasers. In January 2023 Caltech’s MAPLE experiment on the SSPD-1 mission showed in-orbit wireless power transfer to Earth — milliwatts, not megawatts. ESA’s SOLARIS study and JAXA microwave work are the public research lines. This is not a power plant.
Problem it targets
Night and weather limit terrestrial solar. Orbit can see the Sun more of the time. The catch is launch mass, assembly, beam safety, and the cost of every kilogram.
How it works
A large photovoltaic or concentrator array feeds a phased-array transmitter. A rectenna on the ground turns the beam into electricity. Efficiency and land for the rectenna are ordinary engineering; cheap, frequent heavy lift is not ordinary yet.
Status and players
Caltech Space Solar Power Project (MAPLE / SSPD-1, 2023); ESA SOLARIS; JAXA long-running microwave demos; a few startups. NASA and IEA treat SBSP as exploratory, not a 2030 wedge.
Risks and limits
Cost per watt, orbital debris, beam control, and science-fiction slides. A successful milliwatt demo is not a terawatt industry. Keep this card next to fusion: serious research, not a home generator.
Sources
Caltech MAPLE / SSPD-1 January 2023 release; ESA SOLARIS pages; JAXA wireless-power research summaries.