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Imagine you wake up and it’s raining outside. Your rooftop solar panels won’t be much help today. But you flick your lights on and start the coffee anyway, knowing the electricity reaching you through the grid is still powered by the sun — except via solar panels out in space. 

That’s the promise of space-based solar power: low-carbon, flexible and reliable electricity that could provide clean power even when the sun is not shining on Earth. It would act as a backup power source, like batteries, fossil fuel or nuclear plants, while also complementing existing clean energy sources in an energy-hungry world.  

The idea of powering the planet with energy from space is revolutionary and intriguing. Until recently, it seemed unfeasible. 

Now, though, with the increasing impacts of climate change, growing energy demand and a rapidly developing space industry, various international efforts are emerging to make the concept, once confined to science fiction storylines, a reality. 

Indeed, setting up a solar farm in space is no easy feat: it would involve assembling hundreds of thousands of photovoltaic modules as part of a mile-wide structure thousands of miles away from Earth while also building a massive receiver system on Earth in densely populated areas and integrating it into the country’s grid system. 

Space-based solar is a “disruptive technology on the cusp of being commercialized,” said Martin Soltau, co-CEO of Space Solar, a leading company in the field backed by the British government. It’s “really going to provide that global-scale clean energy we need,” he said. 

While Soltau’s enthusiasm is palpable, space-based solar power remains a hotly debated technology, with critics dismayed by the expense and uncertainty.  

“There have always been individuals in the space and energy community who are passionately opposed to space solar power; they just hate the words,” said former NASA physicist John Mankins, known as the godfather of space solar power due to his nearly three decades of work in the field. 

Changing math

The concept of sending solar power to Earth from space has been around for decades. NASA and the U.S. Energy Department investigated it “quite extensively” during the 1970s oil crisis as a way of finding “reliable clean energy that’s from an inexhaustible source,” explained Sanjay Vijendran, who leads Solaris, the space solar program at the European Space Agency (ESA), on a recent podcast.  

But researchers have consistently found one key problem with space solar: it was just too expensive.  

Those calculations are looking completely different today, proponents say. 

The cost of launching a rocket and the cost of making the necessary equipment have gone down by 99% over the last five to 10 years, said Mankins, who founded his own space-based solar company, Mankins Space Technology Inc, and leads a consultancy in the field. Mankins credited SpaceX’s reusable Falcon rocket for this cost drop “revolution,” adding that Falcon’s successor under development, the Starship, promises to lower costs further.

SpaceX CRS-13, a commercial resupply service mission to the International Space Station, launched on Dec. 15, 2017. The mission was contracted by NASA and was flown by SpaceX. It was the second mission to successfully reuse a Dragon capsule. Photo courtesy of SpaceX, shared by Space Center Houston.

These developments make space-based solar a feasible option both technically and economically in the near term, ESA’s Vijendran said. 

A 2022 cost benefit study by two United Kingdom consultancies found that a research and development program for space-power would cost $17.5 billion (€15.8 billion) and setting up a first-of-a-kind operating system would cost almost $11.1 billion (€10 billion). 

The analysis found space solar can be cost competitive with other renewable technologies at $76 per megawatt hour (MWh), referring to the average cost of electricity during the system’s lifetime, accounting for costs to build it, operate it and decommission it. Terrestrial solar costs around $50/MWh over its lifetime, while solar with storage costs around $120/MWh. 

Not everyone is convinced, however. 

While NASA doesn’t actively work in this field, earlier this year the agency released an assessment that found space-based solar designs “may have lifecycle costs per unit of electricity that are 12-80 times higher” than terrestrial solar systems. 

“Do you want to put all that money into the system if you could reap the benefits from using terrestrial energy right now?” Erica Rodgers, director of advanced programs for NASA’s Office of Technology, Policy and Strategy, told Cipher. 

Mankins and Soltau say the agency based its findings on conservative assumptions and has other reasons to avoid investing in this new clean energy source. “NASA doesn’t want to work on space solar power, they want to go to Mars,” Mankins said. 

Asked about the criticism, Rodgers said the agency’s conclusions might change depending on how technology advances in the future, she added. 

International enthusiasm

Several countries are pushing ahead with plans for space solar demonstrations in the coming years. Such pursuits must navigate a complex regulatory landscape covering space activity, safety, radiofrequency management and environmental concerns, but even more rules would have to be drawn up to manage the operation of the tech once up and running. 

Japan is preparing a small demonstration to transmit 1 kilowatt of power in 2025, enough to power a small appliance. China’s ZhuRi program — translated as “chase the sun” — plans to put a pilot power plant into orbit by 2035 generating 10 megawatts (MW) of electricity, enough to power a few thousand homes. 

Space Solar, which received about $3.9 million (£3 million) from the U.K. government and a grant from a Saudi-backed investment fund, is planning to commission the first commercial solar power satellite of 30 MW within the next six years and then gradually scale up to reach a gigawatt, Soltau said.  

The U.K. government also contributed to ESA’s Solaris, working with European industry to conduct initial research on the viability of space-based solar. European leaders will decide in 2025 whether to greenlight a full development program. 

In the United States, research is ongoing at the California Institute of Technology, funded by real estate billionaire Donald Bren. The U.S. Air Force Research Laboratory is also working on the tech for military reasons. 

Mankins said consistent government support is crucial to speeding up development of the industry. He cited SpaceX’s first successful rocket launch, which was largely funded by the U.S. government, for getting the venture capital community more interested in the space industry. But calls for that level of public investment has also invited criticism, given the uncertainty of the outcome.  

In an op-ed earlier this year, for example, retired ESA civil servant Henri Bardi wrote: “success clearly hinges on something that cannot be engineered: sustained political will to invest” in something that might eventually not work.  

 Soltau, among others, remains enthusiastic.  

 “We’ve got no rose-colored spectacles about how difficult this is going to be,” he said. “It’s ambitious. There are all sorts of challenges we’ve got to overcome. But there are no regrets because we’re going to be developing some really key technologies down the road.”