Japanese scientists have figured out how to collect solar energy in space and send it wirelessly to earth

Imagine if, instead of covering suburban roofs and swathes of desert with solar panels, we could just send on big one up into space, to collect energy from the sun and send it back to us.

This faintly science fiction-y idea is exactly what space research groups all over the world are trying to do – and, amazingly, thanks to the work of two Japanese research groups, it might actually be within reach. 

Japanese firm Mitusbishi and JAXA, the country’s space program, announced this month that they’ve succeeded in sending power collected from solar panels wirelessly to a receiver using microwave beams. This is a major breakthrough: the trickiest part of collecting energy on satellites 36,000km above earth is getting it back down again so we can use it for things like laptops and lawnmowers. If it works, space-based solar technology could collect energy at any time of day, and in any weather, making it far more efficient than solar panels on earth. 

This diagram from JAXA gives a rough idea of how the technology would work. Orbiting solar panels attached to a geostationary satellite (one which always hovers above the same point on earth) and collect the sun’s energy. They then convert it into microwaves and beamed to solar receivers on farmland. This energy is then sent into grid.

The two groups have managed the seemingly impossible on two rather different scales, however. JAXA sent a 1.8kW beam to a receiver 55m away, while Mitsubishi managed to send 10kW over half a kilometre. This chart compares the two experiments:

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To put this into context, 10kW is about enough to power a set of kitchen appliances, while 1.8 kW could power a vacuum cleaner. That’s not very much energy, and it’s not been sent very far.

But this is just the beginning – hopefully, the same technology could be developed to send more energy over much longer distances. A JAXA spokesman told Phys.org that practical application of the technology in space could come by the 2040s.

One of the reasons Japan has invested in this sort of research, incidentally, is that it has struggled to fill the energy gap left by the shutdown of its nuclear reactors in the wake of the Fukushima nuclear incident in 2011. It’d be great if something good could come of that disaster.