“It sounds like a science-fiction cartoon, but solar power generation in space may be a significant alternative energy source in the century ahead as fossil fuel disappears,” said Kensuke Kanekiyo, managing director of the Institute of Energy Economics, a government research body.
Japan is developing the technology for a 1 GW solar station, fitted with four square kilometres of solar panels, which it hopes to have up and running within three decades. According to researchers, as the solar station will be in space, it will generate power from the sun regardless of weather conditions, unlike earth-based solar generators which lose performance on cloudy days. The satellites will then convert sunlight into powerful microwave (or laser) beams aimed at receiving stations on Earth, where they will be converted into electricity.
The trade ministry and the Japan Aerospace Exploration Agency, which are leading the project, plan to launch a small satellite fitted with solar panels in 2015, and test beaming the electricity from space through the ionosphere, the outermost layer of the earth’s atmosphere, according to a trade ministry document.
The government hopes to have the final version of the solar station, which will supply enough electricity to power around 500,000 average Tokyo homes, fully operational in the 2030s. Nevertheless, many solutions still have to be found. Transporting panels to the solar station 36,000 kilometers above the earth’s surface will be prohibitively costly, so Japan has to figure out a way to slash expenses to make the solar station commercially viable, said Hiroshi Yoshida, Chief Executive Officer of Excalibur KK, a Tokyo-based space and defence-policy consulting company.
Microwave power transmission
A research group representing 16 companies, including Mitsubishi Heavy Industries Ltd., will spend four years and around 2 trillion yen (€14.5 billion) developing technology to send electricity without cables in the form of microwaves.
JAXA will take a step closer to this goal in February when they begin testing a microwave power transmission system designed to beam the power from the satellites to Earth. In a series of experiments to be conducted at the Taiki Multi-Purpose Aerospace Park in Hokkaido, the researchers will use a 2.4-meter-diameter transmission antenna to send a microwave beam over 50 meters to a rectenna (rectifying antenna) that converts the microwave energy into electricity and powers a household heater. The researchers expect these initial tests to provide valuable engineering data that will pave the way for JAXA to build larger, more powerful systems.
“Humankind will some day need this technology, but it will take a long time before we use it,” Yoshida said.
According to a 2007 report by the US National Security Space Office, in the US the National Aeronautics and Space Administration and the energy department have spent $80 million (€55 million) over three decades in sporadic efforts to study solar generation in space.
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