Space-based solar power

Collectors in orbit that would beam energy down to Earth; experimental.

Capture · Emerging · No. 49

• Capture
• Output: Electricity (experimental)

A satellite 35,786 km up could catch sunlight 99.7% of the time and beam it to Earth as microwaves.

Chart: Illustration: Space-based solar power

Where it comes from

Chart: Map of where it comes from

In geostationary orbit the Sun almost never sets. Mirrors concentrate sunlight onto panels, and a phased array beams the power down at 2.45 GHz to a ground antenna.

Three things to know

1. Caltech's MAPLE satellite, launched in January 2023, beamed power to receivers about a foot away in orbit.
2. A 2 GW reflector design would need about 11.5 km² of solar panels in orbit and a ground antenna 6 km across.
3. Rocket soot holds heat almost 500 times better than soot from other sources, so thousands of launches raise atmospheric worries.

The journey

1. 1 Sunlight in orbitAlmost no night or cloud
2. 2 Solar panelsMirrors focus light; cells make DC
3. 3 TransmitterPhased array forms a microwave beam
4. 4 BeamCrosses 36,000 km and the atmosphere
5. 5 RectennaKilometre-wide antenna turns microwaves into DC
6. 6 GridPower fed to users

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