Picture a vast field of solar panels, ranging in an unbroken array across nearly a square mile of land. Now shift that image into outer space, with the giant structure sitting tens of thousands of miles above Earth’s surface, and you have a sense of what space-based solar power seeks to achieve.
The drive for this energy source comes not just from its advantages over land-based solar, but also from characteristics that set it apart from most other energy sources.
Proponents say it can help power parts of the world that struggle to tap into more traditional forms of energy – either because of their remote location, or because the related infrastructure simply doesn’t exist.
Why We Wrote This
Solar panels in space have potential to bring power to remote locations or to areas hit by natural disaster. Private companies and others are working to refine the technology.
“Solar, fusion, nuclear, coal – you name it – you have to have a plant somewhere and provide infrastructure to support it,” says Paul Jaffe, a former electronics engineer at the U.S. Naval Research Laboratory. “With space solar, you have potential to redirect the energy from a satellite to anywhere on Earth.”
Technology is advancing
In a sign that the technology is stepping beyond the realm of science fiction, Space Solar, a British startup, recently penned a world-first partnership with an Icelandic energy company to supply solar power from space by 2030 – envisioning satellites sufficient to power around 3,000 homes.
Space Solar has also blazed past another milestone in being the first to demonstrate 360-degree power beaming technology – meaning solar panels can beam energy back to Earth, no matter how they rotate to continue facing the sun.
A California-based startup, meanwhile, says it will launch a constellation of orbiting mirrors by 2025 to extend the hours of available sunshine to solar panels on Earth.
And last year, a prototype from the California Institute of Technology gathered solar energy in space and beamed back a detectable amount for the first time. China and Japan have plans to follow suit – by 2028 and 2025, respectively.
“I’m very optimistic indeed,” says Martin Soltau, co-CEO and co-founder of Space Solar. “There are much more complicated robotics in space at the moment, like the Mars rover – we don’t need anything near as complicated as that.”
The idea of space-based solar is to harvest the sun’s energy far beyond the vagaries of our planet’s weather systems, and so high up that the solar panels’ view of the sun is almost never eclipsed.
The energy captured by these solar arrays would be converted to radio waves (or, in some cases, lasers) and beamed to a receiving station on Earth, using a concept of wireless power transmission, where the radio waves would, in turn, be converted into electricity.
In some versions, the hardware would simply act as giant mirrors, reflecting the sun’s rays down to solar panels on the planet’s surface, allowing them to convert energy into electricity before the sun hits them directly in the mornings, or deep into dusk.
These sunlight-harvesting structures would be incomparable in scale to anything currently in orbit: 3,000 times the area of the International Space Station, according to a NASA study of representative designs.
Cost is the biggest hurdle. Indeed, the NASA report found that space-based solar could be 12 to 80 times more expensive than terrestrial alternatives. But the report says it had to make assumptions because the technology is so new.
“We found that cost is really dominated by launch and manufacturing,” says Erica Rodgers, director of advanced programs for NASA’s Office of Technology, Policy, and Strategy, and lead author of the report.
With respect to launch costs, a boost came in mid-October, with the fifth test flight of SpaceX’s Starship, the most powerful rocket ever built. In a world-first, the booster section reached the edge of space and then descended to be caught by two steel arms at the launchpad tower.
A repeat effort in November was less successful, but the smaller SpaceX Falcon rockets have already demonstrated reusability. However, those rockets return to platforms out at sea and need to be towed back to land and refurbished over a course of weeks. The Starship’s aspiration of relaunching within hours, along with its enormous capacity, could significantly reduce the cost of accessing space.
“Starship is the sort of capability that’ll be needed,” says Mr. Soltau of Space Solar. “We need to have a number of launch providers for resilience and to keep them competitive, but rapidly, that market is evolving.”
One worry some critics cite is the level of greenhouse gas emissions that would be produced by putting a space-based solar power system into orbit. But the NASA report concludes that, per unit of electricity generated, emissions are likely to be in line with those produced by the construction of ground-based clean energy systems.
And, though it is likely to be expensive, space-based solar’s capabilities could mitigate the cost.
For example, a remote mining operation, far from any electric grid, would have to pay much more than average for its power. It could prove cheaper to build a receiving station for space-based solar power, rather than forking out for the infrastructure to either connect to the grid or to generate its own power.
Equally, in the wake of a natural disaster, when the grid has suffered catastrophic damage, temporary receivers could be shipped in to source energy from space-based solar installations.
It is in such scenarios, say some, that this technology could find its initial niche, even if costs remain high in the early days.
Concerns include effect on human health
But even if the price tag is acceptable and the technology develops smoothly, there are still issues that cause concern.
Setting up international regulation and standards will be critical for a variety of reasons. One, says Mr. Soltau, is to ensure interoperability “so that a country in Africa, for example, can build an antenna and know that it’s built to the standard so they can receive power from any solar power satellite.”
Other concerns include whether beaming energy to Earth will cause interference with communications, for example, or harm to human health.
Frequencies used by space-based solar radio waves can be set on a bandwidth that will cause minimal disruption to other systems. Operators can ensure the equipment used emits a maximum beam intensity well below anything that would be harmful. Space Solar, for example, states that its technology could transfer nothing more powerful than one-quarter of the sun’s intensity at midday.
“The analogy here is if you have an electric drier in your house, the electricity coming into that would obviously be very dangerous if you didn’t have insulation and regulations,” says Dr. Jaffe, now at the Defense Advanced Research Projects Agency. “We may have to do something similar for space-based solar.”
