Japan Wants to Build a Giant Solar Ring Around the Moon That Will Beam Limitless Energy to Earth

In 2011, a Japanese construction giant quietly proposed wrapping the Moon’s equator in a belt of solar panels stretching 6,800 miles. The Luna Ring concept drew little notice at first. Then the Fukushima Daiichi nuclear disaster struck in March of that year, idling more than half of Japan’s 54 reactors and forcing the country to scramble for energy alternatives. Almost overnight, the Luna Ring found an audience.

Shimizu Corporation’s proposal is enormous in scale. Free from clouds, atmosphere, and night, a lunar solar belt could generate power continuously. In its published concept materials, Shimizu notes that Earth-based solar panels produce roughly one-twentieth of the energy an equivalent array yields in space.

More than a decade later, the Luna Ring remains a paper concept. No construction milestones or fresh funding have materialized. Yet the idea keeps resurfacing because it targets a stubborn problem that terrestrial renewables still cannot solve: how to generate clean, round-the-clock power at a planetary scale.

How Sunlight on the Moon Becomes Electricity on Earth

The mechanism is simple to describe but far beyond current engineering. A ring of solar cells along the lunar equator would face the Sun without break. The Moon has no atmosphere to scatter light, no weather to block it, and on the sunlit side, no night. One half of the equator always catches sunlight.

Cables buried beneath the surface would carry electricity to the Moon’s near side, the face locked permanently toward Earth. Transmission stations there would convert the power into microwave beams and high-energy lasers aimed at receiving stations on the ground. Specialized ground antennas called rectennas would capture the microwaves and turn them back into direct current for the grid. The system could also produce hydrogen fuel, forming what Shimizu calls a global hydrogen society.

“In space, there is constant light hitting the solar panels,” Tetsuji Yoshida, president of Shimizu’s space consulting group CSP Japan, told ABC News in July 2011. “When all the energy created from those panels reaches Earth, there will be no need to produce energy from coal, oil, or biomass.”

Robots and Lunar Soil Would Do Most of the Work

Launching millions of tons of material from Earth would cripple any budget. The Luna Ring proposal sidesteps this by leaning on lunar resources. Shimizu’s documents describe lunar soil as an oxide compound that, with hydrogen imported from Earth, can yield water and oxygen. The same regolith can be processed into concrete, ceramics, glass fibers, and the solar cells themselves.

Robots would handle nearly all construction tasks, tele-operated around the clock from Earth. They would level ground, excavate, and assemble equipment. A small astronaut crew would provide on-site support but play a secondary role. Self-propelled production plants would crawl along the equator, manufacturing solar cells from local materials and installing them as they moved, according to Shimizu’s detailed proposal. A dedicated transit route, with power cables buried underneath, would ferry supplies.

The solar belt would span anywhere from a few kilometers to 400 kilometers in width. Transmission antennas 20 kilometers across would beam power toward Earth, steered by wireless guide beacons to keep the energy on target.

Why the Luna Ring Hasn’t Left the Drawing Board

Money has kept the Luna Ring grounded. Yoshida admitted to ABC News that he had no concrete cost estimate. Beaming gigawatts across 238,855 miles with precision remains untested at any scale. The technology is still in the research phase.

Masanori Komori, an economist with the Institute of Energy Economics in Japan, didn’t mince words in the same 2011 report. “Lunar solar energy sounds good in theory, but costs too much,” he said. He pointed to geothermal power as a more realistic, cheaper alternative already within reach.

Yoshida countered that the basic pieces already exist: sunlight, solar panels, microwaves, lasers. “If we can continue to do the research,” he said, “we think there’s a huge chance this could become reality.”

Where Things Stand Now

Shimizu still lists the Luna Ring under its section for future concepts. No space agency has endorsed it. No development timeline exists. After the Fukushima disaster, the proposal drew a brief wave of attention, but no public updates have moved it past the conceptual stage.

NASA’s Lunar Science Institute website once featured the Luna Ring, giving it passing institutional visibility. That didn’t translate into momentum. Other Japanese groups have since pursued space-based solar power on a far smaller scale. The Japan Aerospace Exploration Agency, Mitsubishi Electric Corp, and Kyoto University have collaborated on trial satellite systems. Mitsubishi separately proposed its Solarbird concept, a fleet of power-generating satellites. None of these efforts approach a lunar ring.

The Luna Ring endures in the conversation because it addresses a real frustration with ground-based renewables: intermittency and land use. A solar plant that runs every hour of every day, untouched by weather, remains a powerful engineering target even if the path there stretches decades long.