Apr 25 2023

Multipurpose Superconducting Highway

When it comes to technology (and also probably many things) there is a pyramid of ideas. At the very bottom of the pyramid is pure speculation, just throwing out “what if” ideas to feed the conceptual pipeline. A subset of these ideas will pass the sniff test enough to justify some kind of proof-of-concept evaluation. This could be just crunching numbers, or even an experiment to see if the idea can work in theory. A subset of those ideas that seem promising will feed a pipeline of research and development, translating these basic concepts into a pragmatic technology. And a subset of those will make it through the pipeline to produce some working technology. A still smaller subset will have all the features necessary to be a successful technology product – economically feasible and competitive, with some marketable practical utility.

When discussing any technology news it’s important to give this context – where in the pyramid are we and how likely is it to make it all the way to the peak? Unfortunately a lot of popular technology reporting treats ideas that are in the pure speculation phase, or perhaps just cracking into the proof of concept level, as if a working product is right around the corner. This leads to confusion and disillusionment. It can also bury news of true breakthroughs in a sea of pseudo-breakthroughs.

With that in mind, I would place this news item about superconducting highways into the pure speculation phase, with a small touch of proof-of-concept. The authors write:

“We envision combining the transport of people and goods and energy transmission and storage in a single system. Such a system, built on existing highway infrastructure, incorporates a superconductor guideway, allowing for simultaneous levitation of vehicles with magnetized undercarriages for rapid transport without schedule limitations and lossless transmission and storage of electricity. Incorporating liquefied hydrogen additionally allows for simultaneous cooling of the superconductor guideway and sustainable energy transport and storage.”

Starting with “we envision” is a good give-away. But here is the proof-of-concept:

Here, we report the successful demonstration of the primary technical prerequisite, levitating a magnet above a superconductor guideway.

So they can check one box in terms of a technical prerequisite, but one that was pretty well established already – you can levitate a magnet above a superconducting material. But they did it for a specific reason. Their primary idea is to reverse how a maglev car or train would work. Right now a maglev train contains cooled superconducting magnets, while the tracks contain conducting loops of material. The superconducting magnets on the train induce a magnetic field in the track, these magnets then push against each other resulting in both levitation of the train and forward propulsion.

The authors’ concept is to reverse this – put the superconducting magnets in the track, while what rides on top of that track can be either a simple magnet or just a conducting loop. The reason we don’t do this now is that the superconducting material used in maglev trains needs to be cooled to -268 C. Cooling the entire track to this temperature is not economically feasible.

This brings us to the second big idea in the paper – how to make a superconducting track economically feasible? The authors speculate that perhaps this system could work if we also used the track for other things, specifically as part of the electrical grid and also to transport liquid hydrogen. Liquid hydrogen is cold enough for the superconducting magnets and would be used to cool them anyway. This triple-purpose track may be economically feasible.

Use as a maglev system is of obvious utility. The US in particular is behind the rest of the developed world in building maglev infrastructure. There are multiple reasons for this. From what I have read it mostly has to do with the fact that the US is large and our main cities are far apart (compared to, say, Europe and Japan). But also such development would require an intimidating patchwork of rights of way that would be difficult to put together. In any case, having a high speed maglev train system in certain corridors of the US could be extremely useful, and even reduce road traffic or demand for short flights. This could also help the transition to electricity based transportation.

What if this same maglev system could double as a superconducting backbone to a new upgraded electrical grid? This could facilitate the sharing of electricity across long distances, something that makes intermittent energy sources more feasible. Superconducting transmission is essentially lossless, which adds efficiency to the grid.

But wait, there’s more. The same system could be used to transport hydrogen, not just use the hydrogen for cooling. I see how this would work in theory, but it is not intuitive to me where the hydrogen is being transported. Where is the hydrogen being made, and where is it being used? Why would this follow along a transportation route? I guess a hydrogen infrastructure could be build around such a system – deliberately build a hydrogen production facility next to a maglev track.

Although, part of the alleged benefit of such a system is that it can be built on top of existing railroad infrastructure, in order to avoid the problem of obtaining complex rights of way. I can see how such a design might work if we were starting from scratch. Imposing it on top of existing infrastructure may be challenging. I am also not convinced there will be a need for massive hydrogen transport, enough to support such a system.

Again – this idea is in the spitballing phase. It is an interesting idea, and generally I like ideas like this that try to gain efficiency in this way. Like all ideas at this stage, the chance it will actually work is quite small. There is a lot of winnowing that happens between the bottom and top of the pyramid. Mainly I would need to see a hard economic assessment. Commercial viability is likely to be the deal-killer here. I think the technology can work – it is built of pieces that we know all individually work. It could also work by fiat, if some government decided to pour a lot of money into something like this. But it won’t really have a significant impact unless it makes economic sense, and it just doesn’t seem likely that building hundreds, thousands or more miles of superconducting rail is going to be feasible.


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