Researchers from the Japan Aerospace Exploration Agency (JAXA) used microwaves to deliver 1.8kW through the air with pinpoint accuracy to a receiver over a distance of 55 meters. In the experiment, conducted last week in Hyogo prefecture in western Japan, the microwaves were successfully converted back into dc power. While the overall efficiency of the power transfer was not revealed, once developed, this technology could pave the way for tapping the vast amount of solar energy available in space and use it here on Earth
If implemented, microwave-transmitting solar satellites would be set up approximately 35,000 kilometers from Earth. Researchers "are aiming for practical use in the 2030s," Dr. Yasuyuki Fukumuro, a researcher at JAXA, said. "This was the first time anyone has managed to send a high output of nearly two kilowatts of electric power via microwaves to a small target, using a delicate directivity control device," he said.
According to Dr. Fukumura, a receiver set up on Earth with an approximately 3-kilometer radius could create up to one gigawatt of electricity, about the same as one nuclear reactor. The relatively low density of the energy transmission is expected to make it safe for airplanes and birds. JAXA has been working on devising Space Solar Power Systems for years, he said.
Solar power generation in space may have many advantages over its Earth-based cousin, primarily the availability of energy, regardless of weather or time of day. While man-made satellites, such as the International Space Station, have long since been able to use the solar energy that washes over them from the sun, getting that power down to Earth has been the challenge. But the Japanese research offers the possibility that humans will one day be able to farm an inexhaustible source of energy in space.
The idea, according to Dr. Fukumura, would be for microwave-transmitting solar satellites—which would have sunlight-gathering panels and antennae—to be set up about 35,000 kilometers from the earth. "But it could take decades before we see practical application of the technology—maybe in the 2040s or later," he said. "There are a number of challenges to overcome, such as improving the transmission efficiencies of these systems, how to send huge structures into space, how to construct them and how to maintain them,†Dr. Fukumura concluded.
