Column There is a fine line between madness and magic in technology. Unless you’re talking about wireless power transmission, where the woo trumps the watts every time.
It all started with Tesla – Nikola, not the automaker – who got down to the idea at the turn of the 20th century and built a giant tower to test it out. He spent all the money and never got it to work, although his followers still cling to the wreckage. Not that anyone has learned.
Since then, there has been a constant stream of startups promising to push power through the ether to distant gadgets. Neither of them can make it work, either – the physics are about good enough for small-scale demonstrations for the crowdfunding video, but goofy afterwards. Consider supplying a city with water from high-pressure jets projected into the air – and that’s a lot smarter than the radio equivalent.
There is one respectable area: satellite power plants. Europe, America and Japan have been refining the idea regularly for decades – another demonstrator is expected to fly in 2023.
Space is a great place for solar power, with a clear line of sight to the Sun. The physics aren’t that bad for a single big fixed microwave link: think of the waterfall. With the world gagging for clean renewables, a permanent supply from heaven is too good to be missed. But will he fly?
There are two main aspects to this question, economic and technical. The European Space Agency has put its finger in the exosphere [PDF] some time ago and this space power may be competitive with terrestrial renewables at different scales, with an ideal area of around 150 gigawatts. This represents between a third and a half of the average European electricity consumption.
That’s a nice thought, not just because of the savagery that would drive the 5G Wingnuts, which go nuts down to a few milliwatts. However, security is not an obstacle; you can design ground antenna farms for overall power densities in accordance with applicable safety guidelines.
The heat now is a problem. The 150 GW deliverable power is a beast. Do the math on the conversion efficiency to collect solar electricity and turn it into radio waves, and you get about 20%. That means 600 GW of heat to remove and forget about cooling towers. The only way to get rid of heat in a closed vacuum system is to diffuse it, which will require a heat sink. Did you think Alder Lake was warm?
Then there is the question of where to park your smoking sputnik. To be good, a Powersat must point its panels towards the Sun and its antennas towards the ground. In medium or low Earth orbit, the satellite moves in the sky, which means that it must rotate one of the two. Have you ever tried to design a rotary joint that can handle gigawatts of power for about 20 years? No you don’t. Many have tried. It does not happen.
So let’s get Hotsat One into geostationary orbit. It stays in one place in the sky, which makes things a lot simpler. It’s in almost permanent sunlight – don’t worry about the 90 equinoctial days with eclipses of up to 80 minutes. If you design your panels to be a giant mosaic of tiny solar cells, transmitters and antennas integrated on all surfaces, it doesn’t matter that the orientation to the Sun is constantly changing.
But if all of your surfaces are active, what about the heat? Plus, it turns out that the cold is just as much of a problem, as the panels bordering the sun get very cold, much colder than the electronics would like. Huge thermal swings aren’t good for reliability, and if you want to do something that’s hard to fix, put it in space at 7,375 km.
Then there is the ladder. With about 10 times the solar line available in space relative to the ground with its weather, atmosphere and nightfall, you don’t need as much solar panel space up there as you do here. . You still need several square kilometers of tiles which need to be smoothed out, put together and moved to the correct orbit. And if you think radio astronomers are unhappy with Starlink’s little two-way radios, wait until those sensitive dishes get full power from a powerhouse pointed directly at them. It’s a whole new area of electromagnetic compatibility, right there.
Even though these problems and the value of an asteroid are fixable, it will take decades of expensive and painful work to get close. Meanwhile, the real activity of building solar power plants in the field where we can tour with a van, and creating better storage and transmission technologies that we can deploy with an excavator, continues. We are getting very good at it, and we are getting better every year.
The bottom line is that the Law of Commercial Wireless Power holds in orbit as well as it does in Omaha: you can build a technology demonstrator that’s good enough to extract more funding, but you’ll never make it useful. It’s even worse than fusion. If you’re still tempted, keep one final thought in mind: Any idea so crazy that even Elon Musk avoids can be found on the Hyperloop Express for Wibble City. The train is coming ! Woo woo! ®