A Bold Plan to Beam Solar Energy Down From Space

Whether you’re covering deserts, ugly parking lots, canals, or even sunny lakes with solar panels, clouds will occasionally get in the way—and every day the sun must set. No problem, says the European Space Agency: Just put the solar arrays in space. 

The agency recently announced a new exploratory program called Solaris, which aims to figure out if it is technologically and economically feasible to launch solar structures into orbit, use them to harness the sun’s power, and transmit energy to the ground.

If this concept comes to fruition, by sometime in the 2030s Solaris could begin providing always-on space-based solar power. Eventually, it could make up 10 to 15 percent of Europe’s energy use, playing a role in the European Union’s goal of achieving net-zero carbon emissions by 2050. “We’re thinking about the climate crisis and the need to find solutions. What more could space do to help mitigate climate change—not just monitor it from above, as we’ve been doing for the past few decades?” asks Sanjay Vijendran, who heads the initiative and plays a leading role in the agency’s Mars program as well.

The primary driver for Solaris, Vijendran says, is the need for continuous clean energy sources. Unlike fossil fuel and nuclear power, solar and wind are intermittent—even the sunniest solar farms sit idle the majority of the time. It won’t be possible to store massive amounts of energy from renewables until battery technologies improve. Yet according to Vijendran, space solar arrays could be more than 90 percent efficient. (The remaining 10 or so percent of the time, the Earth would be directly between the sun and the array, blocking the light.)

The program—unrelated to Stanisław Lem’s sci-fi novel with the same name—is considered a “preparatory” one, meaning the ESA has already completed a pilot study, but it’s not yet ready for full-scale development. It calls for designing an in-orbit demonstration of the technology, launching it in 2030, developing a small version of a space solar power plant in the mid-2030s, and then scaling it up dramatically. For now, ESA researchers will begin by investigating what it would take to robotically assemble the modules of a large solar array, for example while in geostationary orbit at an altitude of about 22,000 miles. This way, the structure would remain continuously above a particular point on the ground, regardless of the Earth’s rotation.

For the project to go forward, Vijendran and his team must determine by 2025 that it’s indeed possible to achieve space-based solar in a cost-efficient way. NASA and the Department of Energy explored the concept in the 1970s and ’80s, but sidelined it because of the expense and technological challenges. Still, much has changed since then. Launch costs have dropped, mainly thanks to reusable rockets. Satellites have become cheaper to mass-produce. And the cost of photovoltaics, which convert sunlight into electricity, has fallen, making solar power in orbit more competitive with terrestrial energy sources.