Originally published on The Daily Flare.
KEY TAKEAWAYS
- Caltech’s MAPLE experiment demonstrated wireless power transmission from orbit in 2023, the first time solar energy collected in space produced a signal detected on Earth.
- Japan’s OHISAMA satellite, scheduled for launch in fiscal 2026, is designed to beam about one kilowatt of power from low Earth orbit to a ground station in Suwa.
- China, the UK, and ESA are all working toward orbital demonstrators, but launch costs remain the biggest obstacle between today’s tests and commercial power stations.
Space based solar power collects sunlight in orbit and beams it to Earth as microwaves, offering clean energy day and night, rain or shine. Here is how close the technology is to becoming real.
The idea is older than the International Space Station. In 1968, the engineer Peter Glaser proposed placing solar panels in geostationary orbit, where they would catch uninterrupted sunlight, convert it to electricity, and transmit it wirelessly to receiving stations on the ground. For decades it stayed in the realm of proposals, too expensive to launch and too difficult to aim. That is changing. Falling launch costs, lighter materials, and precise microwave beam steering have turned space based solar power from a thought experiment into an active engineering race involving the United States, Japan, China, and Europe. None of the projects has delivered meaningful electricity to the grid yet, but the first real demonstrations have now happened in orbit, and the next round of tests is already scheduled.
Understanding why the idea refuses to die starts with the limitations of solar panels on the ground. Terrestrial solar stops at night and dips under cloud cover, which is why grids pairing it with batteries need long-duration energy storage technologies to keep the lights on. A solar array in geostationary orbit, 36,000 kilometers above the equator, faces the sun almost continuously. Caltech’s team has estimated that such arrays could yield roughly eight times more power per panel than installations on the surface, an estimate that captures the core appeal: a baseload renewable source that never sleeps. The standard design converts sunlight to microwaves, transmits them through the atmosphere (which microwaves cross with low losses), and catches them with ground-based rectennas, rectifying antennas that convert the beam back into grid electricity.
First Proof It Can Work: The 2023 Caltech Demonstration
The most important milestone so far came from the Caltech Space Solar Power Project, a research effort started in 2013 and funded by donations from Donald Bren eventually exceeding $100 million. On January 3, 2023, the project’s first in-space prototype, the Space Solar Power Demonstrator (SSPD-1), launched aboard a Momentus Vigoride spacecraft. It carried three experiments, each targeting a different piece of the puzzle: DOLCE, a 1.8 meter by 1.8 meter structure testing how ultralight spacecraft frames deploy in orbit; ALBA, a collection of 32 different types of photovoltaic cells to see which survive the harsh space environment; and MAPLE, the Microwave Array for Power-transfer Low-orbit Experiment.
MAPLE was the centerpiece. It is an array of flexible, lightweight microwave transmitters driven by custom silicon chips, designed to fold up for launch and steer a beam without any moving parts, using precise timing to focus the energy on a chosen spot. In 2023 it demonstrated wireless power transfer between two receiver arrays inside the spacecraft, lighting up small LEDs with energy harvested in orbit. It then did something no hardware had done before: it directed its array toward Earth, and a receiver on the roof of the Gordon and Betty Moore Laboratory on Caltech’s Pasadena campus picked up the signal. Caltech called it the first demonstration of wireless energy transfer from space, a deliberately careful phrase. The Earth-side result was a detected signal rather than usable power, but it proved that beam steering works in the real space environment, surviving launch vibration, temperature swings, and radiation. Earlier, NASA’s PRAM experiment aboard the X-37B spaceplane (2020) had shown that sunlight could be converted to radio-frequency energy in orbit. Together, the two flights answered the field’s most basic question, whether energy could be sent down from space at all. The answer is yes, on a small scale, with much bigger engineering still ahead.
The Space Based Solar Power Race Goes Global
After Caltech’s demonstration, attention shifted to the next, larger tests. Japan is furthest along. Its OHISAMA satellite, developed by Japan Space Systems under a commission from the Ministry of Economy, Trade and Industry, is a 180 kilogram spacecraft about the size of a washing machine carrying a two square meter solar panel. It is scheduled to launch in fiscal year 2026 aboard the Space One company’s Kairos 5 small rocket into low Earth orbit, at roughly 400 kilometers altitude. Once there, it will convert sunlight into microwaves and beam them to a receiving station in Suwa, Nagano Prefecture, where 13 antenna arrays spread over 600 square meters will catch the energy and convert it into electricity. The expected output is about one kilowatt, enough for a small appliance, which is not the point. The point is to prove the entire chain, sunlight to microwaves to usable electricity on the ground, end to end, from orbit.
Japan’s motivation is unusually strong. The country imports more than 90 percent of its energy, and JAXA, the national space agency, has researched wireless power transmission since the 1980s, with space solar power in the national space policy since 2009. Japan Space Systems has also sketched the long-term vision: arrays 2.5 kilometers across in geostationary orbit, beaming to a four kilometer diameter ground antenna, with each unit generating about one gigawatt, described as more than ten percent of Tokyo’s annual electricity consumption. That concept is a proposal, not funded hardware, but it shows where the program intends to go. Readers should treat social media claims that Japan has already switched on an orbital power station with skepticism. OHISAMA is a technology demonstrator, not a power plant, and its value is proof, not output.
Europe took a different path. At the end of 2022, ESA launched SOLARIS, a three-year preparatory programme to assess whether space based solar power could help Europe’s net zero goals. It commissioned concept studies from industry teams including Thales Alenia Space and Arthur D. Little, looking at microwave and laser transmission, and even a concept that simply reflects sunlight down to ground solar farms. A decision on whether to start a full development programme was expected around the end of 2025. ESA’s subsequent position, though, was that the technology still needs more maturation before a demonstration mission, and SOLARIS is not proceeding in the form originally imagined. The agency continues technology development instead. That sounds like a setback, but for a program this capital intensive, a careful “not yet” is arguably the right answer. ESA’s commissioned studies put the net present value of a European system at hundreds of billions of euros over the coming decades, which explains why the agency is still in the game. More background is on ESA’s SOLARIS research page.
The United Kingdom, meanwhile, is pushing from the private sector side. In 2026 the Space Energy Initiative, a public-private partnership, published a whitepaper calling on the UK government to co-fund a first orbital demonstrator. The group backs Space Solar’s CASSIOPeiA satellite architecture and argues the technology could deliver electricity at around £30 per megawatt-hour at today’s launch costs, falling toward £10 as launch prices drop. Those are the initiative’s own projections, and they depend on very optimistic assumptions about manufacturing at scale. The proposed timeline is aggressive: an orbital wireless power demonstration in 2027-2028, a megawatt-scale orbital pilot in 2029-2030, and a commercial demonstration above 100 megawatts in 2032-2035.
China is thinking biggest of all. Its Zhuri program, led through Xidian University, has published a staged roadmap: a low Earth orbit test satellite in 2028 generating 10 kilowatts and testing microwave transmission over 400 kilometers; by 2030 an array above 100 kilowatts testing medium-power laser transmission across 36,000 kilometers; by 2035 a 100 meter antenna with 10 megawatts of generation; and by 2050 a commercial station generating two gigawatts with a roughly one kilometer antenna assembled in space. The veteran engineer Long Lehao compared the concept to moving the Three Gorges Dam into geostationary orbit. These are planning targets from published roadmaps, not binding schedules, and the 2030s dates will likely slip, as large space programs do. But they show that Beijing treats orbital power as strategic infrastructure, not just research.
| Milestone | Organization | Year | Status |
|---|---|---|---|
| PRAM RF conversion test | NASA | 2020 | Demonstrated |
| MAPLE wireless power demo | Caltech | 2023 | Demonstrated |
| SOLARIS feasibility programme | ESA | 2022-2025 | Completed |
| OHISAMA satellite demo | Japan Space Systems | FY 2026 | Planned |
| Orbital wireless power demo | UK Space Energy Initiative | 2027-2028 | Proposed |
| 10 kW LEO transmission test | China (Zhuri) | 2028 | Planned |
| Megawatt-scale orbital pilot | UK Space Energy Initiative | 2029-2030 | Proposed |
| 100 kW array, GEO-range test | China (Zhuri) | 2030 | Planned |
| 2 GW commercial station | China | 2050 | Long-term plan |
What’s Next for Space Based Solar Power
The next three years will decide whether the field keeps accelerating or stalls. Japan’s OHISAMA test is the most important near-term event: if it delivers usable electricity from orbit, it will be the first end-to-end proof that the whole chain works outside a lab. China’s 2028 satellite and the UK’s push for a funded demonstrator are the follow-ups to watch. Behind the hardware, the real race is economic. A 2021 NASA study estimated that space solar could be roughly ten times more expensive than terrestrial renewables, with launch costs, in-orbit assembly, and maintenance doing most of the damage. Every project’s business case assumes those costs keep falling as reusable rockets fly more often and satellites get lighter and cheaper to build.
There are also questions that have nothing to do with engineering. Beaming microwaves from orbit raises safety and regulatory issues: the beams are designed to stay at low, non-harmful intensities, but large-scale systems will need international agreements on spectrum, orbital slots, and liability, the same kind of slow diplomacy that governs satellites today. Public acceptance matters too. A gigawatt-scale beam is safe by design, but it will need to be proven safe in public, not just on paper. Countries with the heaviest fossil fuel dependence may be the most motivated to accept the technology, since orbital power promises exactly what they lack: a domestic, always-on, zero-carbon source.
The honest picture in 2026 is this: the physics is proven, the small-scale engineering is demonstrated, and nobody has shown it can be affordable. Space based solar power is not about to replace ground solar, and how green hydrogen is advancing shows there are other strong contenders for cleaning up hard-to-electrify energy use. But the concept has moved from viewgraphs to flight hardware, with four major programs running real tests or concrete roadmaps. The 2020s were about proving a signal can reach the ground. The 2030s will be about proving a power station can pay for itself. If OHISAMA works, the next question will no longer be whether the sun can be harvested from space, but whether anyone can afford to do it.
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