Space solar power could offer a constant influx of green energy — but it may not be a sound investment

May 29, 2021

Solar power from space is the next frontier. Seen here, International Space Station solar array panels. (NASA)

Placing solar panels in outer space that beam energy down to Earth has become a topic of discussion among engineers, but economists are saying the idea is not fiscally responsible.

An analysis published May 12 in Acta Astronautica finds the concept cost-ineffective when compared with other electricity options — even in the best-case scenario of transporting building materials via SpaceX's reusable Starship and using the energy for expensive remote mining operations away from the power grid.

A concept first developed in the 1920s by Russian scientist Konstantin Tsiolkovsky — who also popularized the idea of space elevators — space solar power is slowly gaining interest among institutions such as the Japan Aerospace Exploration Agency, the European Space Agency and California Institute of Technology.

Scientists working for the Pentagon even sent a version of a space solar panel "the size of a pizza box" into orbit, but the energy-harvesting method's economic feasibility may be standing between the prototype and reality.

"This is a terrible time to think about space solar power because terrestrial electricity is getting cheaper," study author Ian Lange, an associate professor of economics and business at the Colorado School of Mines told The Academic Times.

Between 2009 and 2019, for example, the price of solar energy from panels planted on Earth has dropped by 89%. This type of energy is considered sustainable and green because the use of solar panels doesn't pollute the environment with fossil fuels — unlike energy from coal, for instance. A downside of some solar panels, however, is their negative impacts on natural habitats and water processes.

Although solar energy prices are dropping, and researchers are working to improve solar cells' efficiency, there are limitations to placing the panels on Earth — the primary one being that the planet generally only gets about six hours of direct sunlight per day, because the sun sets in the evening. The exact duration ultimately depends on location.

In space, however, there is no such thing as night. Solar panels in orbit could theoretically offer constant energy sourced from never-ending sunlight. The Earth's atmosphere also degrades some sunlight as the rays travel toward terrestrial ground, something that could be avoided if the panels themselves resided in space.

"But then," Lange explained, "you have to turn [the space solar energy] into a microwave and microwave it down to the Earth and turn it back to electricity. You've got to get permits for that."

On top of losing some energy along the way — meaning the efficiency may not be as high as expected — there are legal hurdles in the commercialization of sending energy down to Earth from the planet's orbit.

"It's going to be pretty expensive to start up a demand for electricity in space," said Lange, who was also a senior economist on the White House Council of Economic Advisers for one year under President Donald Trump. "Anyway, if we're going to get a bunch of stuff out there, then that [itself] demands electricity."

Using a typical discounted cash flow analysis to arrive at a valuation for the novel energy-collection tactic, the team found that transportation of materials accounted for a sizable portion of the necessary costs.

"What we tried to do here is be like, 'Let's find the most sympathetic case for space solar power,'" Lange said. "It's important that we consider all possible safe ways to get resources — including space. I feel like there's a lot of assumption that it's better if it's in outer space."

The most feasible and economically justified scenario the team came up would rely on two elements. First, transportation of materials would have to be via Elon Musk's reusable rocket, Starship. On May 5, following a few failed attempts that ended in crashes and one explosion, SpaceX sent a version of the Starship to an altitude of about six miles and then successfully landed it on Earth.

However, Musk declared in 2012 that he thinks space solar power isn't a good idea, partly due to low energy-conversion efficiency during the transfer process.

The researchers behind the new study also considered which field would most benefit from space solar power and decided on remote mining operations — which are off the grid, meaning they don't have access to public energy utilities.

"Grid power is really cheap because we have wind, we have solar, we have cheap natural gas that we can build at scale," Lange said. "If you're nowhere near a grid, it's really expensive."

But even after considering that the cost per kilowatt-hour of diesel, the standard fuel for such operations, would be on the higher end at 30 cents, the researchers' stance on the space solar power concept didn't change.

"We end up getting a negative total benefit," Lange said. "Right now, remote mining operations would probably be better to just ship out diesel."

However, Lange relayed that there may be a couple of cases in which space solar power is a viable option, the first being where there are several mines in one area off the grid that can collect power in bulk.

"Your cost of making a slightly bigger base-load power wouldn't rise at the same level if you could sell twice as much power," he explained.

Lange also said that, one day, if terrestrial power such as energy for satellites or mining on the moon becomes increasingly expensive and difficult to manage, then space solar power may have to be revisited.

"At some point, there'll be demand on the moon … and it'll be useful to have these things in outer space," he said. "But it's not to say that it's better to think about that than think about Earth — we have to start by thinking about everything on Earth."

The study, "Feasibility of space solar power for remote mining operations," published May 12 in Acta Astronautica, was authored by Nicholas Proctor, Ensieh Shojaeddini, Angel Abbud-Madrid and Ian Lange, Colorado School of Mines; and Peter Maniloff, North Carolina State University. 

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