Solar Power from the Moon
By Patrick Tucker
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.
The year is 2050 and it’s morning on the Moon. The Sun is rising over a landscape that is bleak and featureless with one exception: a wide belt of photovoltaic panels that cuts across the ash-gray lunar surface like a straight river. Not a single astronaut is in sight, but a troop of robots is busily making repairs to the installation where tune-ups are needed. Beneath the panels, superconducting cables are ferrying the Sun’s power to transmission centers. The power will be beamed to a receiving station near the Earth’s equator, and from there, it will be distributed to energy-hungry cities and towns across the globe where it will keep the lights on in offices, hospitals, and schools.
Meet the LUNA RING, the brainchild of Tetsuji Yoshida and his colleagues at CSP, the research arm of Shimizu, one of the largest construction firms in Japan. The LUNA RING is an idea that could only come from the land of the rising sun, a country boasting many of the world’s best-known technology companies, like Sony, Hitachi, and Panasonic, but also saddled with a shortage of natural resources.
The LUNA RING speaks to a future global need that’s keenly felt in the present in Japan, a nation now also coping with the impacts of the devastating March 2011 earthquake on its nuclear power capacity.
It’s also an example of planning in the long term.
“My very optimistic forecast is 25 years,” Yoshida told me when I visited the company headquarters in Tokyo last November. He explained that this is the time required before they could even begin the lunar-surface activity, assuming that Japan, the United States, or some other investor was actually willing to fund the project. “The scale is so huge; I don’t know how long it would take to construct. We may have to adjust the plan and the scale,” he says.
If the most exciting part of Yoshida’s job is coming up with bold engineering concepts, the most difficult part, except for the math, is keeping people’s expectations realistic. Shimizu’s company president, Yoichi Miyamoto, was hoping to pitch the project to potential investors with a start date on the Moon of around 2035. Yoshida sees this as ambitious, to say the least. The technical, practical, and monetary obstacles to building a solar laser power station on the Moon are unprecedented.
But the LUNA RING is buildable. Photovoltaic panels, remotely guided robots, and microwave transmission and lasers are already proven technologies. The project is simply raising the proverbial bar on the current state of innovation—raising the bar to the Moon.
“It’s very challenging, a good project for a company like Shimizu. So this is a type of campaign for us,” says Yoshida.
A Feat of Futurism
To the jaded technology watcher, the LUNA RING may read not so much bold as old-fashioned. In the project’s size and scope, the faith it expresses in large-scale and long-term government-funded initiatives, it harkens back to the 1970s, a decade synonymous with many things, not least of which was U.S. space program euphoria. It was during the 1970s that the U.S. Department of Energy and NASA first conducted a series of studies on the feasibility of sending energy to Earth from satellites.
These studies, called the Satellite Power System Concept Development and Evaluation Program, were nothing less than an exercise in super-futurism, with a group of scientists from around the world writing back and forth in reports, letters, and journal articles, trying to design something in the distant future using tools and technologies that did not exist in the present.
The proceedings of the program note more than a few major obstacles to collecting and transmitting power in space. “The space infrastructure requirements were projected to be significant,” John C. Mankins, the manager of the Advanced Concepts Studies Office of Space Flight, told Congress in 1979, in what might be considered something of an understatement.
The program explored a variety of concepts, design plans, and scenarios. One proposal emerged as a leader: a network of dozens of satellites working together to catch solar energy and beam it to Earth, rather than a single satellite. But even with a network, the objects and their solar arrays would need to be enormous to do the job: large enough to collect and transmit 5 gigawatts of power each, according to Mankins’s testimony. (They would be transmitting power for use in the United States exclusively.) Sending objects into orbit becomes more costly and complicated as the size of the satellite increases. These wouldn’t be simple Sputniks, either, but rather floating power stations a kilometer or so in diameter—far larger and more complex than any communications satellites in space today.
The ongoing maintenance costs of the network would thus be enormous. Mankins testified that the cost to build the system would be more than $250 billion in present-day dollars. The program concluded in 1979, leaving many questions unanswered. Then, between 1980 and 1981, the U.S. energy crisis ended, and interest in space-based solar power hit a wall.
Fifteen years later, NASA initiated a three-year Fresh Look Study. A brief Exploratory Research and Technology Program followed. The agency found that many of the technical obstacles it first faced decades ago no longer seemed so insurmountable. Photovoltaic arrays in the 1970s could convert into power roughly 10% of the solar energy that struck them. By 1995, they were far more efficient and much lighter. New ideas were on the table, such as satellites that used inflatable trusses rather than metal to decrease object weight.
Mankins himself ditched the dispersed satellite network scheme and came up with a new idea for designing, building, and launching satellites. In his 1995 plan, many thousands of smaller, identical solar-gathering modules come together to form a much larger whole, the same way that thousands of similar ants come together to form colonies and millions of quite similar Web sites and Web servers form the Internet—a “super-organism,” Mankins calls it. The logistics of building and launching a type A mini-satellite 9,000 times (then type B, then type C) is less daunting than figuring out how to launch a few extremely complex, independently functioning machines. Mankins calls this realization his eureka moment. “It led me for the first time to believe that space-based solar power was technically possible,” he says.
Despite this encouraging progress, the question remained: How do you conduct tens of thousands of satellite launches, keep the devices working together collecting and transmitting energy safely, and keep the maintenance costs under control?
According to Yoshida, this is the wrong series of questions.
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 David Criswell. 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. “I don’t think [it will be] a big problem to control the robots on the Moon,” Yoshida says.
• 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.
“Because there is no population on the Moon, it’s a good test spot for laser tests,” Yoshida says. “On Earth, it’s too dangerous. We have to spread out the energy concentration.”
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.
Over the Moon
Reaction to the LUNA RING among space experts whom THE FUTURIST contacted was optimism tempered by skepticism.
“It’s good that a major corporation is considering the Moon as a platform for gathering solar power and providing it to Earth,” said David Criswell, the director of the Institute for Space Systems Operation at the University of Houston, in an e-mail. “I’ve argued for years that the Moon [is] the only means to provide adequate commercial power to Earth to enable sustainable prosperity.”
Criswell is a long-time advocate for using the Moon as a power station. Although he’s a cheerleader, he acknowledges that much more research needs to be done before a Moon-based power plan can attract serious consideration. Much of that research would have to take place aboard the International Space Station, which, according to Criswell, presents something of a problem. “The fully staffed International Space Station will be hard pressed to do its few authorized experiments in low-Earth orbit and keep the station operating. It doesn’t have the capability to support the logistics for a major lunar infrastructure project or the staff to monitor lunar surface operations,” he said. “However, the station does provide the operational experience for building other specialized facilities in orbit about the Earth and Moon and on the Moon for power production.”
Power from the Moon would have to travel 10 times farther to get to Earth than would the same juice collected from a satellite. Mankins believes that a giant wireless transmitter floating in space would need to play a part in sending microwave or laser power from point A to point B. Robots building solar arrays out of lunar dirt? Maybe one day, Mankins says, but he insists that, when space-based solar power comes to light, it will have to use hardware built on Earth, at least initially.
“I believe that the first [space-based power] pilot plant could (with funding) be on orbit within 10–15 years; waiting for a lunar base to be established first would delay the availability of space solar power by decades,” he wrote in an e-mail. “From time to time, Shimizu develops a very visionary future large-scale engineering concept that they then articulate to a broad audience. Their LUNA RING concept is only the latest of these.”
John Hickman, a member of the board of advisors of the MarsDrive project and author of Reopening the Space Frontier (Common Ground Publishing, 2010), is known as a space-policy realist. He’s argued that the problem with most super-large space projects is that they require too much from potential investors: too much up-front capital, too much patience, and too much faith.
“If attracting capital for projects using proven technologies like communications satellites remains difficult, imagine the difficulty of attracting sufficient capital to construct a mining facility on the Moon or terraforming Mars or Venus,” he wrote in his 1999 essay, “The Political Economy of Very Large Space Projects,” a critical analysis of why mega-scale space schemes almost never get off the ground.
Hickman says that the LUNA RING boasts a few advantages over other similar projects. It could provide returns within a reasonable time frame, but would probably make for a better investment if ownership of lunar real estate were part of the deal. He suggests that Shimizu obtain legal title to the land on which it plans to build. “Unfortunately, the 1967 Outer Space Treaty made the Moon an international commons. That means that Shimizu would be constructing the LUNA RING on land ‘owned’ by all of the states on Earth,” he wrote in an email. But Japan could withdraw from the treaty and “claim the lunar equator as its sovereign national territory.”
Hickman is curious about what funding streams the company may draw upon but thinks the LUNA RING would probably need a large public investment to be economically viable.
The project is well suited to Japan, he says, in that it makes use of the country’s expertise in public works construction and robotics. But that doesn’t mean Japan is a good funding source. Japan carries more debt than almost any other highly industrialized country: almost 200% of the country’s GDP. Financially, Japan is in a terrible position to sponsor a project of this size.
“For Japanese decision makers to commit the capital necessary to launch construction of the LUNA RING would be a demonstration of unusual political will,” says Hickman.
The United States is another potential investor, if not for the LUNA RING, then for some competing space-based solar power program, perhaps of the sort that Mankins has suggested. The Obama administration has made repeated statements in favor of alternative-energy research initiatives and big public works. But the administration is also facing record deficits, a Congress fighting to repeal its signature health-care program, a retirement wave of historic proportions, and reelection in two years. Pitching a speculative and fantastically expensive lunar energy project to the American people under such conditions would be a loser.
“National political and economic decision makers in every advanced industrial democracy are especially risk averse at present about government expenditures for new projects,” Hickman points out.
Ask Yoshida about cost and he’ll shake his head and cross his arms tightly across his chest. “It’s always cost,” he grumbles. “Cost is a problem.… But price is a human tool for exchanging goods. Maybe this type of project could be out of range of cost considerations. We would have to find a new word for it?”
An energy plan beyond the realm of cost considerations? It’s an optimistic idea, even more so than sending robots to the Moon to build solar panels. In broaching it, Yoshida is also acknowledging that the greatest impediment to space-based power isn’t rockets or robots or physics; it’s a dearth of public resources. A project of such size and scope would require the willingness of hundreds of millions of souls to reembrace government-funded space programs. It would require sacrifice in the form of higher taxes, cuts in other areas, or both. At present, this seems beyond the capacity of the developed world.
But then, not long ago, we said the same thing about reaching the Moon.
About the Author
Patrick Tucker is the senior editor of THE FUTURIST magazine and the director of communications for the World Future Society.
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