A Japanese company is pitching an alternative energy plan that’s out of this world—and potentially the largest public infrastructure project in human history.
Our Sun is the primary power source driving life on Earth. It has enabled us to use massive flows of oil, coal, and natural gas burned with oxygen to provide approximately 85% of the 15 trillion watts of commercial thermal power that energizes the $60-trillion-a-year world economy.
Every year, more of this thermal power is converted into electricity. By mid-century, most power will be delivered as electricity. Since 1980, Japan and western Europe have achieved $42 trillion per year of gross national product for every 1 trillion watts of electric energy consumed. Two kilowatts per person of clean electric power can power economic prosperity. Ten billion people will need 20 trillion watts of power a year.
Our Sun is the only reasonable source for sustainable global-scale commercial power. But we cannot gather it dependably and inexpensively on Earth. Our biosphere interrupts the flow of solar power with varying day–night cycles, clouds, fog, rain, smoke, dust, and volcanic ash. These forces act with floods, wind, sandstorms, industrial chemicals, biofilms, animals, earthquakes, etc., to attack the necessary large-area solar installations. Extremely expensive, planetary-scale power storage, of indeterminable capacity, and global-scale power distribution systems will be required to deliver electricity somewhat reliably to consumers all around the world. Japan’s nuclear power plants deliver approximately 50 GWe of commercial power. An Earth-based station receiving solar energy from the Moon (a rectenna) could easily be built to produce that amount of power for commercial use. Moreover, such rectennas would never release radioactivity or CO2 and could be quickly replaced at low cost after a disaster.
For these reasons and others, solar power from the Moon is our best shot at meeting future energy demands. If the United States had stayed on the Moon during the 1970s, focusing on using the common lunar materials to manufacture at low cost the simple standard components of a lunar solar power system, then today, not only the United States but also the rest of the world would be green, prosperous, and secure. Such a system would pay for itself with 15 years of use.
Our primary challenge is mental. We must refocus our actions from battling each other and Earth for the declining resources within our limited biosphere and instead tap the Moon for solar power that is engineered to meet our needs.
‘Luna Ring’ – a new plan from Japan
The world is not short of far-fetched ideas for transformative zero-emissions power stations. But while airborne drone-supported windfarms and dubious cold fusion generators are certainly nice to haves, they’re not quite as bold as locating the power station itself outside Earth’s atmosphere.
That’s the essential idea behind ‘Luna Ring’ – a new plan from Japan which aims, one day, to turn the Moon into an enormous solar panel.
Shimizu Corporation’s ‘Luna Ring’ concept would essentially enclose the moon in a gigantic, 400km-wide and 11,000 km-long mirrored structure, which would capture solar energy in an extremely efficient manner, and beam it back to Earth with lasers.
The company points out that such a concept would eliminate inefficiency due to bad weather and achieve continuous, 24/7 power “for the infinite coexistence of mankind and the Earth”.
The Moon-Based Power Station
A solar collection satellite launched from Earth, even using the most advanced materials available in 2011, would weigh close to 10,000 tons, says Yoshida. This number, he later explained in an e-mail, is his estimation of the weight of a 1-million-kilowatt power plant in geosynchronous orbit.
“So heavy and hard to control, you will need so many rocket launch pads. Too much money.… So we chose the Moon as a power station,” he says. “We already have a natural satellite, one with minerals and resources. And it already receives sunlight across its surface area.”
The Moon’s face receives 13,000 trillion watts (terawatts) of solar power continuously. This is 650 times the amount of power the entire human population would need to continue to grow economically, according to space power expert. Solar collection on the lunar surface would be 10 times more efficient than it is on Earth, where our ozone and rich atmosphere make solar collection less efficient.
Here’s how the LUNA RING would work.
• Robotic staff. The lunar base would require some human personnel, but the bulk of the work on the Moon would be performed by robots that were remotely controlled. Japan has been conducting experiments with robotic giant arms in space since the 1997 launch of the ETS (Experimental Test Satellite) No. 7.
• Panels. Sending enough photovoltaic arrays to encircle the lunar equator would require a lot of costly launches and burn up a lot of rocket fuel. The LUNA RING plan calls for the robotic construction of those panels on the Moon directly from lunar soil. This increases the overall efficiency and energy savings of the program compared with others. It also bumps up the complexity level of the proposal considerably.
Photovoltaic panels are constructed from silicon, which makes up 23% of the lunar surface. The Moon also hosts aluminum and aluminum oxide, which factor into many solar cell designs. “Theoretically, we have enough materials on the lunar surface” to build solar panels, Yoshida says. But finding significant deposits of these minerals is a lot harder on the Moon than on Earth, where the formation and movement of oceans, rivers, lakes, and streams created accessible mineral stores. “There’s no concentration of these minerals,” says Yoshida, “so all these resources are spread over the lunar surface.”
Shimizu scientists are working on ways to derive sufficient quantities of the minerals they need using hydrogen deduction. But building solar panels from moon dirt (and doing so via remote-controlled robot) remains the most ambitious aspect of the plan.
Once constructed, those panels would produce a lot of power. A 4 × 400 km portion of the lunar solar belt would produce power equal to the energy consumption of Japan, says Yoshida. A 30 × 400 km portion would equal the energy consumption of India. Sixty by 400 km would power the United States, and a 400 × 400 km square would collect enough energy to satisfy the power needs of the entire human population, by Yoshida’s calculations.
• Laser transmission. Like those solar-based power plans from the 1970s, the LUNA RING would beam energy to Earth in one of two ways, using either a microwave or a laser.
Microwave transmission experiments have been ongoing since the 1960s and space laser studies since the 1980s. In that time, science agencies have demonstrated power transmission in space, between orbiting objects and the Earth and between planes and the ground. These, however, were low-level power exchanges. The most famous of these took place in Goldstone, California, on June 5, 1975; the NASA Jet Propulsion Laboratory successfully transmitted 34 kilowatts of power over a distance of 1.5 kilometers. A space-based power station would have to transfer a lot more power a lot farther. More tests will be conducted around the world between now and 2015, including in the Tokai region of Japan where researchers are working with a 2 kilowatt infrared laser. This isn’t a lot of power, either—not enough to run a car, but sufficient to boil water in a matter of seconds.
The ultimate test of spatial power-beaming could occur on the Moon itself. If NASA sets up a lunar base at either of the Moon’s poles—one of many projects under perennial consideration at the agency—a satellite flying around the Moon could conceivably power that base via microwave or laser transmission, thus proving the feasibility of using the Moon as a power station.
The LUNA RING station would beam 220 trillion watts (terawatts) to Earth on a yearly basis (the beaming would be continual). Of that, only about 8.8 terawatts would be usable on the ground. The rest would be lost in space.
