Space-based Solar Power: A Great Idea Whose Time May Never Come

The scene: A space-based solar power station called the Converter being commissioned some time in the Future. The characters: Two astronauts, Powell and Donovan, and a robot named QT-1 (“Cutie” to its human friends). The plot: The astronauts are training Cutie to take over the station’s operations, which involve collecting solar energy in space and then directing it as intense beams of microwaves down to Earth.

This is the backdrop for Isaac Asimov’s 1941 short story “Reason.” Most of the story centers around Asimov’s Three Laws of Robotics and the humans’ relationship with the robot. But the station itself is worth a second look. It’s pretty clear Asimov had no idea how a system like the Converter would actually work, except in the most basic terms. Here’s how Powell tries to explain it to Cutie:

“Our beams feed these worlds energy drawn from one of those huge incandescent globes that happens to be near us. We call that globe the Sun and it is on the other side of the station where you can’t see it.”

Harnessing the power of the sun in space is certainly an enticing idea. A decade ago we featured a project at the Japan Aerospace Exploration Agency that aimed to launch a 1-gigawatt solar station by 2031. As a step in that direction, JAXA says it will demonstrate a small satellite transmitting 1 kilowatt of power to Earth from an altitude of 400 kilometers next year. We’ve also reported on Caltech’s SSPD-1 demonstrator project and the US $100 million from a billionaire donor who funds it.

A space solar project would “waste capital that could be better spent improving less risky ways to shore up renewable energy, such as batteries, hydrogen, and grid improvements.”

And yet, space-based solar power remains more science fiction than science fact, as Henri Barde writes in “Castles in the Sky?” Barde should know: He recently retired from the European Space Agency, where among other things he evaluated space power systems. As Barde’s article makes abundantly clear, this clean energy would come at an enormous cost, if it can be done at all, “[wasting] capital that could be better spent improving less risky ways to shore up renewable energy, such as batteries, hydrogen, and grid improvements.”

For example, U.K.-based Space Solar estimates it will need 68 (!) SpaceX Starship launches to loft all the assets necessary to build one 1.7-km-long solar array in orbit. Nevermind that SpaceX hasn’t yet successfully launched a Starship into orbit and brought it back in one piece. Even if the company can eventually get the price down to $10 million per launch, we’re still talking hundreds of millions of dollars in launch costs alone. We also don’t have real-life Cuties to build such a station. And the ground stations and rectennas necessary for receiving the beamed power and putting it on the grid are still just distant dots on a road map in someone’s multimillion dollar research proposal.

Engineers are often inspired by science fiction. But inspiration only gets you so far. Space-based solar power will remain sci-fi fodder for the foreseeable future. For the monumental task of electrifying everything while reducing greenhouse gas emissions, it’s better to focus on solutions based on technology already in hand, like conventional geothermal, nuclear, wind, and Earth-based solar, rather than wasting time, brainpower, and money on a fantasy.

This article appears in the June 2024 print issue as “The Chasm Between Imagination and Feasibility.”

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