Beijing (CNN) - China says it is working to develop a solar energy plant in space that could one day beam enough power back to Earth to light up an entire city.
If scientists can overcome the formidable technical challenges, the project would represent a monumental leap in combating the Earth's addiction to dirty power sources which worsen air pollution and global warming.
A space-based solar power station could also provide an alternative to the current generation of earthbound and relatively ineffective renewable energy sources.
Scientists had previously thought space solar plants (SSPs) would be prohibitively expensive.
But with Beijing pledging to invest 2.5 trillion yuan ($367 billion) in renewable power generation -- solar, wind, hydro and nuclear -- by 2020, China might just have the financial firepower.
The state-owned China Aerospace Science and Technology Corporation hopes to be operating a commercially viable solar space station by 2050, according to a recent report in the country's official newspaper Science and Technology Daily.
Energy could be beamed to Earth via microwaves or lasers. But Pang Zhihao, a researcher at the China Academy of Space Technology, warned that the hazards potentially posed to humans, plants and animals by that process must be examined.
While an endless source of renewable energy is the holy grail in tackling climate change, some fear that lasers produced at an SSP could potentially be weaponized to give Beijing a lethal military instrument.
China was late to the space race -- it didn't send its first satellite into orbit until 1970 -- but its program has seriously matured in the past few years, hitting milestones including a manned spaceflight and the landing of a rover on the far side of the moon, a historic first.
But under President Xi Jinping, it has invested billions in building up its space program, while aggressively asserting its influence back on Earth, pursuing the "great rejuvenation of the Chinese nation."
The plans are getting more ambitious by the day. At the 2019 opening of the Chinese People's Political Consultative Conference on Sunday, the chief designer of China's lunar exploration told of plans to send a rover to Mars.
"Over the past 60 years, we've made a lot of achievements, but there is still a large distance from the world space powers. We must speed up our pace," Wu Weiren said, claiming a probe would be sent to the red planet in 2020.
Space solar energy is the biggest potential energy source available to humans and could supply nearly all the electrical needs of every person on our planet, according to the United States National Space Society (NSS).
The technology for harnessing solar power in space has been around since the 1960s, says Peter Schubert, director of the Richard G. Lugar Center for Renewable Energy at Indiana University-Purdue University Indianapolis.
But there are several technical hurdles, he says.
These include finding a low-cost, environmentally friendly launch vehicle to take the solar plant into space, combating the huge in-orbit operation and construction costs, and working out how best to transmit the power back to Earth.
One solution to the first issue could be 3D printing.
"Additive manufacturing is now widely available for the aeronautics industry," says Nobuyoshi Fujimoto, a spokesman for the Japan Aerospace Exploration Agency (JAXA), the country's equivalent of NASA.
"Therefore, this new manufacturing technology will be used for SSPs as well."
The NSS believes the necessary technologies are "reasonably near-term" and the costs involved are smaller than paying the price of global warming -- particularly when the long-term environmental benefits are considered.
A solar power plant floating 36,000 kilometers above our heads, for example, wouldn't be subject to the vagaries of generating solar power back on Earth.
Instead, it could be receiving the sun's energy and generating power 99% of the time, only going offline when the Earth eclipses the sun.
Furthermore, the sun's rays wouldn't be weakened by their journey through the Earth's atmosphere. Such a plant would be up to six times more efficient than comparable technologies on Earth, the Science and Technology Daily report says.
How it works
Components, including solar panels and technology for converting electricity for transmission, would be blasted into space where they would be assembled.
The completed solar farm would be placed in a geostationary orbit over a receiving station on Earth. It would transmit the energy -- either in the form of a laser or as microwaves -- to the Earth base, where it could be reconverted to electricity and distributed via the grid.
Experts estimate that a fully operational solar array would have to be huge -- at least 2 square kilometers (0.8 square miles) -- to produce 1 gigawatt of power, JAXA's Fujimoto says.
Its construction would also present huge logistical issues.
"(An) SSP would be assembled piece-by-piece over repeated launches and dockings," according to the JAXA. "The construction of the structure by crew members would be prohibitively expensive and unsafe. A key phase of the program will be to develop robotic systems capable of assembling all of the components of the large orbital structure autonomously."
China Aerospace Science and Technology Corporation plans to launch small solar satellites that can harness energy in space as soon as 2021. Then it will test larger plants capable of advanced functions, such as beaming energy back to Earth via lasers.
A receiving station will be built in Xian, around 500 miles northeast of the Chinese city of Chongqing. The city is a regional space hub where a facility to develop the solar power farms has been founded.
By 2050, the company plans that a full-sized space-based solar plant would be ready for commercial use, the Chinese media report said.
"The approach that the Chinese have announced looks very reasonable to me," says Schubert. "Because the ultimate goal of this is to get very large power stations, doing that all in one go is not practical -- there are a lot of things you learn along the way."
Li Ming, director of the Technology Committee of the Fifth Institute of China Aerospace Science and Technology Group, told Chinese media that if Beijing continues to invest and develop in the emerging technologies, it "could be the first country that has a utility value solar power space station," according to the Science and Technology Daily.
The US hasn't looked into developing SSP technology since 2003, Schubert says.
"A challenge in the US is the influence of energy companies for which SSP would be a disruptive technology," he says. But he adds that if the technology proves viable, the US would "likely be a fast follower-then-leader," similar to how it played catchup to the Soviet Sputnik project before overtaking it to land a man on the moon.
"In my opinion the scale is such that Chinese-American collaboration would be the best path to success," he adds. However, current laws prohibit NASA from cooperating with China on aerospace technology."
Laser power ... and threat
While experts believe the microwaves beamed from the solar farms would be about as intense as the sun's rays on a summer's day, Pang says more research is needed into the potential long-term effects on the ecology, atmosphere, and organisms.
In addition to providing constant renewable energy to the planet, a space solar power plant could, in theory, focus its beam outward and power spacecraft, obviating the need for solar cell wings and greatly increasing power levels and control accuracy.
The energy beams could also direct power to remote areas or even dissipate destructive weather systems like typhoons.
But there is a potentially more worrying application.
"Coherent radiation from a laser is so far different from the microwave or radio wave approach -- (if weaponized) a laser could burn a city to the ground in a matter of minutes or hours," says Schubert.
Schubert says that a satellite in geostationary orbit has a view of about one third of the Earth's surface, which would present a huge tactical advantage -- the ultimate "high ground," he says.
"It is my opinion that no large nation would allow another nation to put a 5 GW laser in (goestationary orbit). As everyone knows, there is no such thing as an unhackable system. Huge power lasers are just too much of a risk to put in space."
Still, with governments around the world battling to hold back climate change, some feel space solar technology can't come soon enough.
"When we look at ... carbon emissions globally, they're on the increase -- as developing nations improve their standard of living they're burning coal even though we know about climate change," says Schubert.
"If we could get spaceborne power to get going quickly, that would address the root cause of the problem and provide us a carbon-free energy source that's reliable around the clock. In my mind, it's the most important technology for the future of mankind."