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Today we're looking at one of the most ambitious energy proposals ever put on paper, a Japanese construction firm's plan to ring the entire Moon in solar panels and beam the power back to Earth. It sounds wild, but the science behind it holds up better than you'd expect.

Let's get into it.

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In 2013, Japanese construction giant Shimizu Corporation published a formal proposal for something they called the Luna Ring, a continuous belt of solar panels stretching 11,000 kilometers around the lunar equator, collecting sunlight and transmitting the energy back to Earth as microwave beams and high-energy lasers.

The concept had been developing inside Shimizu for years before that, but the 2011 Fukushima Daiichi nuclear disaster gave it a sudden urgency, because with more than half of Japan's 54 nuclear reactors shut down after the meltdown, a country that had relied on nuclear power for 30 percent of its electricity supply was suddenly forced to think very differently about energy.

Shimizu is not a fringe outfit, and that matters when you're evaluating how seriously to take a proposal like this. The company has been operating continuously since 1804, making it over 220 years old, and its portfolio includes skyscrapers, tunnels, dams, and major infrastructure projects across Japan and abroad. When a firm with that kind of track record publishes a technical proposal, it deserves a closer look before being dismissed.

How It Works

The core logic of the Luna Ring starts with a straightforward fact that most people don't think about, which is that solar panels on the Moon's surface would be roughly 20 times more productive than equivalent arrays on Earth.

There is no atmosphere to absorb or scatter sunlight, no cloud cover, no weather, and no night on the sunlit side of the lunar equator, meaning one side or the other is always receiving full, unfiltered solar radiation around the clock.

The energy would travel in stages. Solar cells installed along the 11,000-kilometer equatorial belt convert sunlight into electricity, and underground cables carry that electricity to the near side of the Moon, the face that permanently points toward Earth.

From there, microwave transmission antennas 20 kilometers in diameter would beam the energy across the 238,855-mile gap between the Moon and Earth, with high-energy laser beams serving as a secondary transmission method. On the ground, specialized receiver antennas called rectennas capture the microwaves and convert them back into usable electricity for the power grid.

The belt itself would range from a few kilometers to 400 kilometers wide at its maximum, and Shimizu estimates that a fully completed Luna Ring could generate up to 13,000 terawatts of continuous power, which is roughly 500 times current global electricity consumption.

Tetsuji Yoshida, the head of Shimizu's space consulting group, told to a news channel that if all of that energy could reach Earth, there would simply be no reason left to burn coal, oil, or biomass.

The Construction Plan

Building anything on the Moon means solving problems that humanity has never faced at scale, and Shimizu's answer to nearly all of them is robotics. Almost all construction would be carried out by tele-operated machines controlled from Earth 24 hours a day, performing tasks like excavating the lunar crust, leveling terrain, and assembling equipment modules that were transported from Earth and lowered to the surface from orbit. A small number of astronauts would support operations on site, but human presence on the surface was always envisioned as minimal.

To keep the cost of launching materials from Earth as manageable as possible, Shimizu's plan relies heavily on the Moon's own resources as construction material. Lunar regolith is rich in oxide compounds, and by importing hydrogen from Earth, workers could extract both oxygen and water directly from the surface.

That water could be combined with lunar soil to produce concrete for foundations and transport routes, while the same soil can also be processed into glass fiber and ceramics for structural use.

Self-propelled robotic manufacturing plants would move progressively along the equatorial belt, producing solar cells from local materials and installing them as they traveled.

The Cost Problem

This is where the proposal runs into its most honest obstacle, and Yoshida himself has not tried to hide it. He admitted in interviews that he has no concrete cost estimate for the project, and independent analysts who have examined the numbers have put the figure conservatively above $100 billion, with most observers suspecting the realistic total would run several multiples higher than that.

Masanori Komori, an economist with Japan's Institute of Energy Economics, told ABC News that the concept sounds appealing in theory but is far too expensive to be practical, and that Japan should focus on more accessible alternatives like geothermal power that are already available and far cheaper to develop.

Beyond money, there are other unresolved questions that the proposal has not fully answered. International space law does not clearly define construction or ownership rights on the Moon, which creates genuine legal uncertainty about who can build what and whether other nations would accept it.

And beaming gigawatts of microwave energy across 238,000 miles with enough precision to reliably hit a specific rectenna on Earth is a feat that has never been attempted at anything close to this scale, while the entire value of the system depends on that transmission chain working continuously and safely for decades.

Where the Field Is Today

The Luna Ring itself has not moved beyond Shimizu's concept page, as the company has not secured funding, no space agency has endorsed it, and no active development timeline exists. But the broader idea it represents, collecting solar energy above the atmosphere and beaming it to Earth, has made genuine progress in the years since Shimizu first published their proposal.

In January 2023, Caltech launched a small orbital demonstrator carrying an experiment called MAPLE (Microwave Array for Power-transfer Low-orbit Experiment), and in March of that year MAPLE became the first system ever to wirelessly transmit power in space using flexible, lightweight structures, with its signal detected at a ground station at Caltech.

The power levels involved were tiny, but the proof of concept was real, and Caltech's president noted after the mission concluded that commercial-scale beamed power from space remains a future prospect while adding that the mission demonstrated it should be an achievable one.

Meanwhile, the UK-based firm Space Solar completed a government-funded feasibility study in 2025, and Japan's space agency JAXA has been running space-based solar power research under the country's 2023 Space Security Initiative, which explicitly tied lunar development to national energy security. The Luna Ring is no longer sitting in isolation as a curiosity from a single company's website, it sits at the far end of a spectrum of increasingly serious, increasingly funded research into the same underlying idea.

The Bottom Line

The Luna Ring is not being built, and it may never be built on any timeline most of us will live to see, but it is also not a joke, because the physics are sound, the technology components are real, and the underlying problem it tries to solve is one the energy world is actively grappling with.

What Shimizu put on paper in 2013 is essentially the most extreme version of space-based solar power anyone has seriously proposed, and as smaller-scale demonstrations like Caltech's MAPLE experiment prove that individual pieces of this actually work, the distance between that extreme and practical reality gets a little shorter each year.

Category: Research and Analysis

"I'm researching [technology or infrastructure concept] and want to understand it clearly. Give me the strongest argument in favor of it, the strongest argument against it, and the one technical problem that would need to be solved before anything else could move forward, all in plain language without hype."

The Luna Ring is the kind of idea that sounds absurd until you sit with the numbers for a few minutes, at which point it starts to feel more like a very expensive engineering problem than an impossible one.

Shimizu has been in continuous operation for 222 years, and they are still treating this as a serious long-term proposal rather than a thought experiment, which says something worth taking seriously about how they read the future of energy demand.

Whether humanity ever needs power badly enough to build a plant on the Moon is a question that belongs to the future, but it is no longer a question that belongs purely to science fiction. Hit reply, I read every response.

See you in the next one.

— Vivek

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