Japan aims to beam solar energy down from orbit
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Concept artwork shows how an array of mirrors could collect solar energy and transmit it to the ground
Mafic Studios, Inc |
The Japanese space agency JAXA is developing a revolutionary concept to put "power stations" in orbit to capture sunlight and beam it to Earth.
The country has been looking for new power sources following the devastating earthquake and tsunami in March, 2011, that destroyed much of the north-east of the country and caused a meltdown at the Fukushima Daiichi Nuclear Power Plant.
Many of the country's nuclear reactors were closed due to stricter safety regulations after the emergency. Now JAXA is aiming to set up a Space Solar Power System (SSPS) by 2030. An array of mirrors would sit in geostationary orbit to collect solar energy and then transmits it to a power plant on the ground via microwaves or laser beams. There it could be used to generate electricity and hydrogen.
Proponents of the technology say that it would provide continuous energy without any worry that resources would be depleted. It would be unaffected by the time of day or weather and would provide environmentally friendly, clean energy.
Interestingly, the idea is not a new one. An American, Dr Peter Glaser, designed a similar concept in 1968 to deploy large solar panels in space to generate power and convert it into microwaves to transmit to the ground. Following studies by NASA and the US Department of Energy, the project was deemed too costly and it was never developed.
Similar studies have been carried out in Europe. The idea is also reminiscent of a Russian plan in the 1990s to use mirrors to beam sunlight to the ground at night. This had astronomers and environmentalists up in arms because of the light pollution it would have caused. The Japanese concept is different because there would be no stray light emitted from the beam.
Yasuyuki Fukumuro is leading research and planning for SSPS. He says: "We have not yet decided whether to use microwaves or laser beams with SSPS, or whether we will somehow combine them. We are currently conducting ground-based experiments to find the most efficient way to transmit energy.
"Regardless of which transmission technology we use, when we collect sunlight from outside the Earth's atmosphere, we can get a continuous supply of it, with almost no influence from the weather, the seasons, or time of day, allowing very efficient collection of solar energy.
"And since the energy source is the Sun, it's an endlessly renewable resource -- it won't run out as long as the Sun is there. Also, because the power is generated in space and carbon dioxide is emitted only at the receiving site, emissions within the Earth's atmosphere can be greatly reduced, which makes this technology very friendly to the environment."
Fukumuro admits the system has its challenges. He says: "When transmitting power by microwaves, a significant technological challenge is how to control the direction, and transmit it with pinpoint accuracy from a geostationary orbit to a receiving site on the ground. Transmitting microwaves from an altitude of 36,000 km to a flat surface 3 km in diameter will be like threading a needle."
Fukumuro suggests the technology will also be useful in disaster situations. In the event of a blackout, a collecting dish could be unfolded and deployed to receive microwaves from space for conversion into electrical energy.
JAXA is working with a collective of machining and engineering companies called Kyoto Shisaku Net to develop the array of reflectors that would be lifted into orbit by reusable shuttle-like spacecraft and then assemble themselves.
JAXA Engineer and Senior Researcher Katsuto Kisara says: "The biggest problem we've encountered with the project is developing solar mirrors that are incredibly lightweight. I think that there is certainly a way to do it, but it has presented quite the challenge."
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