Japanese space agency hopes to harness solar power in 25 years

Mirrors in orbit would reflect sunlight onto huge solar panels, and the resulting power would be beamed down to Earth. John MacNeill/IEEE

By 2030, Japan hopes to have an idea operational that now seems to have its roots deep in science fiction -- a space-based solar energy farm.

According to a recent report by IEEE Spectrum, the Japan Aerospace Exploration Agency has proposed a plan to create a series of geosynchronous-orbiting satellites that could collect solar power, beaming it back to Earth. The agency also reportedly hopes to have it done within the incredibly ambitious timeline of 25 years.

The March 2011 tsunami that damaged nuclear power plants -- causing radioactive waste to leak at Fukushima -- led to a search for renewable energy alternatives that would allow the country to forgo nuclear energy. With Japan's scarce availability of land and natural resources, such as coal, a space-based solar electricity farm seems like the best idea, according to Susumu Sasaki, a professor emeritus at JAXA.

JAXA is working on several different models that could one day power the world's electricity. In one model, a one-sided photovoltaic-topped satellite's efficiency would decrease as the Earth turned away from the sun. In another model, two mirrors would reflect sunlight onto a two-sided photovoltaic-topped satellite, allowing for 24 hours of continuous energy.

This is the latest plan to cultivate solar energy through satellites since 1968, when American engineer Peter Glaser acknowledged the challenges of constructing, launching and operating these satellites -- as well as wireless power transmission, power generation and power management, Sasaki notes.

JAXA will focus its research on wireless power transmission, as transmitting power over long distances can be difficult. Sasaki says that this can only be accomplished through laser or microwave beam. Laser wavelengths, which have short wavelengths, can be transmitted and received by relatively small components -- perfect for satellites. However, short-wavelength lasers could be blocked by the atmosphere, and water molecules. Microwaves, on the other hand, have 80 percent efficiency and can penetrate the atmosphere.

Difficulties persist as scientists have to figure out how to transmit the power -- such as the size of the antenna and the correct microwave frequency -- but Sasaki remains optimistic.

"It would be difficult and expensive, but the payoff would be immense, and not just in economic terms," Sasaki writes. "If humanity truly embraces space-based solar power, a ring of satellites in orbit could provide nearly unlimited energy, ending the biggest conflicts over Earth's energy resources.

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