The battle to dispel smog, cut greenhouse gases and solve the energy crisis is moving to space.
Chinese scientists are mulling the construction of a solar power station 36,000 kilometers above ground.
If realized, it will surpass the scale of the Apollo project and the International Space Station, and be the largest-ever space project.
The power station would be a super spacecraft on a geosynchronous orbit equipped with huge solar panels. The electricity generated would be converted to microwaves or lasers and transmitted to a collector on Earth.
In 1941, U.S. science fiction writer Isaac Asimov published the short story "Reason", in which a space station transmits energy collected from the sun to various planets using microwave beams.
Wang Xiji, an academician of the Chinese Academy of Sciences (CAS) and a member of the International Academy of Astronautics, says Asimov's fiction has a scientific basis.
U.S. scientist Peter Glaser published an article in the journal Science in 1968, claiming a feasible design for the space solar power system.
After devoting more than half a century to space technology research, Wang, 93, is an advocate for the station: "An economically viable space power station would be really huge, with the total area of the solar panels reaching 5 to 6 square kilometers."
That's equivalent to 12 of Beijing's Tian'anmen Square, the largest public square in the world, or nearly two New York Central Parks.
"Maybe people on Earth could see it in the sky at night, like a star," says Wang.
Researchers in many countries have drawn dozens of designs, with square, round and bowl-shaped stations.
But why build a power station in space? Wang says the electricity generated from the ground-based solar plants fluctuates with night and day and the weather, while a space-based generator can collect energy 99 percent of the time.
Space-based solar panels can generate ten times as much electricity as ground-based panels per unit area, says Duan Baoyan, a member of the Chinese Academy of Engineering (CAE).
"If we have space solar power technology, hopefull we could solve the energy crisis on Earth," Duan says.
The world has recognized the need to replace fossil fuels with clean energies. However, the ground-based solar, wind, water and other renewable energy sources are too limited in volume and unstable.
"The world will panic when the fossil fuels can no longer sustain human development. We must acquire space solar power technology before then," Wang says.
"Whoever obtains the technology first could occupy the future energy market. So it's of great strategic significance," Wang says.
"Construction of a space solar power station will be a milestone for human utilization of space resources. And it will promote technological progress in the fields of energy, electricity, materials and aerospace," says Wang.
Countries such as the United States and Japan have studied a space solar power station. Japan is leading in the development of wireless power transmission technology.
Some Chinese research institutes and universities have also conducted studies related to space solar power technology in recent years.
Members of the CAS and CAE wrote a report in 2010, suggesting that China should build an experimental space solar power station by 2030, and construct a commercially viable space power station by 2050.
However, many huge hurdles lie ahead.
For instance, a commercially viable space power station would weigh more than 10,000 tons. But few rockets can carry a payload of more than 100 tons to low Earth orbit.
"We need a cheap heavy-lift launchvehicle," says Wang, who designed China's first carrier rocket more than 40 years ago.
"We also need to make very thin and light solar panels. The weight of the panel must be less than 200 grams per square meter."
He also points out that the space solar power station could become economically viable only when the efficiency of wireless power transmission, using either microwave or laser radiation, reaches around 50 percent.
However, he is confident that China can build a space solar power station.
Li Ming, vice president of the China Academy of Space Technology, says, "China will build a space station in around 2020, which will open an opportunity to develop space solar power technology."
The space station could surport experiments on the key technologies of constructing space solar power station, Li says.
China is also expected to develop a new generation heavy-lift launch vehicle, he adds.
"When space solar energy becomes our main energy, people will no longer worry about smog or the greenhouse effect," says Wang.
"The development of wireless power transmission technology will be a great advance. After the technology is applied, power cables will not be needed anywhere in the world. Just imagine what a world it will be," he says with a smile.