Space-based solar power: Techniques
Giant mirror satellites, flat arrays and tiny test craft
What this tab covers The methods used to capture this energy: how each works, and how they compare on efficiency, cost, life-cycle emissions, maturity and scale.One technique with several design variants: large geostationary satellites beaming microwaves to kilometre-scale ground antennas, and small low-orbit demonstrators, some using lasers. Only small demonstrations have flown.
Comparison
| Method | Efficiency | Cost | Life-cycle emissions | Maturity | Scale |
|---|---|---|---|---|---|
| Geostationary microwave satellite with reflectors (NASA RD1, CASSIOPeiA-type)123 | About 13% sunlight to grid (calculated); 99.7% capacity factor. | NASA baseline USD 610/MWh (FY2022 dollars), 12 to 31 times projected 2050 terrestrial renewables; USD 30-40/MWh if all optimistic assumptions hold. UK study: GBP 50/MWh p50 (GBP 35-79, 2018 prices). ESA study: EUR 106-206/MWh for a first unit at a 20% hurdle rate. | 26.6 g CO2e/kWh baseline (about 3.8-3.9 optimistic), excluding upper-atmosphere launch effects. | research | None built. Designs deliver about 1.4 to 2 GW each. |
| Geostationary planar microwave satellite (NASA RD2)1 | Same conversion chain; 60% capacity factor. | NASA baseline USD 1,590/MWh (FY2022 dollars); USD 80/MWh optimistic. | 40.4 g CO2e/kWh baseline (4.3 optimistic). | research | None built. |
| Low-orbit demonstrators (Caltech MAPLE, Japan OHISAMA, Aetherflux)567101112 | Not reported for demonstrations. | Aetherflux raised USD 60 million in total by April 2025. | No life-cycle study found. | pilot | Milliwatts to watts demonstrated; kilowatt-class tests pending. |
Cost estimates differ more than tenfold: NASA's 2024 study puts baseline costs at USD 610-1,590/MWh, while the UK and ESA studies, assuming cheap reusable launch and learning, find about GBP 50/MWh and EUR 89-206/MWh. The gap is driven mostly by launch cost (71-77% of NASA's system cost) and hurdle rates. Baseline emissions of 27-40 g CO2e/kWh sit within NASA's range for terrestrial renewables (13-43).
How each method works
Geostationary microwave satellite with reflectors (NASA RD1, CASSIOPeiA-type)Mirrors concentrate sunlight onto solar panels on a satellite 35,786 km up, above one point on Earth. A phased array forms a 2.45 GHz microwave beam aimed at a ground rectenna, a field of small antennas and diodes that turns it back into electricity.123
Geostationary planar microwave satellite (NASA RD2)A flat solar array without mirrors transmits at 5.8 GHz to five 4 km ground sites. Simpler, but with a lower capacity factor.1
Low-orbit demonstrators (Caltech MAPLE, Japan OHISAMA, Aetherflux)Small satellites test the key steps. Caltech's MAPLE (launched January 2023) beamed power to receivers about a foot away and sent a detectable signal to a Caltech roof. Japan's 180 kg OHISAMA aims to beam about 1 kW of 5.8 GHz microwaves from about 400 km to Suwa, Nagano; as of September 2026 it had not launched (target FY2026). Aetherflux, renamed Cowboy Space in May 2026, launched its kilowatt-class laser satellite Reason-1 on 1 October 2026; no results had been reported by October 2026.567101112
Sources
- Space-Based Solar Power (Office of Technology, Policy, and Strategy) NASA, 2024
- Space-Based Solar Power: final report (cost-benefit study for ESA SOLARIS) Frazer-Nash Consultancy, 2022
- Space Based Solar Power as a Contributor to Net Zero, Phase 2: Economic Feasibility Frazer-Nash Consultancy for UK BEIS, 2021
- Scientists beam solar power to Earth from space for 1st time ever Space.com, 2023
- Space-based solar power: Japan's OHISAMA project aims to beam solar energy to Earth Notebookcheck, 2025
- Space solar startup Aetherflux raises $50M to launch first space demo in 2026 TechCrunch, 2025
- JEO 20: News Roundup, 16 Sept 2026 (OHISAMA status) Japan Earth Observer, 2026
- Our First Mission Takes Flight (Reason-1) Cowboy Space (formerly Aetherflux), 2026
- Cowboy Space puts orbital power beaming to the test with Reason-1 Highways Today, 2026