The Japan Aerospace Exploration Agency has a technology road map for orbiting solar panels that could provide power for Earth. According to an in-depth article in the IEEE Spectrum, a combination of technical and social factors is fueling the plan.

Recent advances in wireless power transmitters allow moving antennas to coordinate to send a precise beam across large distances. And of course, the concern over greenhouse gases emitted from burning fossil fuels is causing nations to seriously consider alternative sources of energy.

Space-based solar collectors in geosynchronous orbit could generate power 24 hours a day. The Spectrum article looks at the history of studies of space-based solar power and delves deeply into how the orbital solar farm would work.

JAXA is looking at several models that would fly in geosynchronous orbit 36 000 kilometers above their receiving stations. With one model, the photovoltaic-topped panel’s efficiency would decrease as the world turned away from the sun. An advanced model would feature two mirrors to reflect sunlight onto two photovoltaic panels. This model would be more difficult to build, but it could generate electricity continuously, according to the Spectrum.

In either model, the photovoltaic panels would generate DC current, which would be converted to microwaves aboard the satellite. The satellite’s many microwave-transmitting antenna panels would receive a pilot signal from the ground, allowing each transmitting panel to separately aim its piece of the microwave beam at the receiving station far below. Once the microwave beam hits the receiving station, rectifying antennas would change the microwaves back to DC current. An on-site converter would change that current to AC power, which could be fed into the grid...(IEEE Spectrum)

JAXA’s plan calls for work to begin on a 100-kW SPS demonstration around 2020. Engineers would verify all the basic technologies required for a commercial space-based solar power system during this stage.