236
Why are maglev trains still rare?
(lemmy.ml)
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
this post was submitted on 08 Sep 2023
236 points (94.4% liked)
Asklemmy
43773 readers
1379 users here now
A loosely moderated place to ask open-ended questions
If your post meets the following criteria, it's welcome here!
- Open-ended question
- Not offensive: at this point, we do not have the bandwidth to moderate overtly political discussions. Assume best intent and be excellent to each other.
- Not regarding using or support for Lemmy: context, see the list of support communities and tools for finding communities below
- Not ad nauseam inducing: please make sure it is a question that would be new to most members
- An actual topic of discussion
Looking for support?
Looking for a community?
- Lemmyverse: community search
- sub.rehab: maps old subreddits to fediverse options, marks official as such
- !lemmy411@lemmy.ca: a community for finding communities
~Icon~ ~by~ ~@Double_A@discuss.tchncs.de~
founded 5 years ago
MODERATORS
The same reason supersonic passenger jets are rare.
The extra speed comes with a massive increase in costs.
Travel 30% faster than high speed rail for 10-20 times the cost.
Is the claim about "10-20 times the cost" true? The internet says Shanghai maglev cost $1.33 billion for 30.5 km, i.e. less than $44 million/km. Compare https://transitcosts.com/new-data/ or https://transitcosts.com/high-speed-rail-preliminary-data-analysis/
Secondly, if it is true, why would it be true? Why would it be more expensive to build something with fewer moving parts?
Supersonic passeenger jets require more energy. Maglev trains require less energy.
all the other complex and important factors aside, air restistance is a formula of speed squared. Meaning for example if you bump speed up by 40% you double air resistance, and therefore double the energy cost of transport.
Isn’t that only applicable for identical trains? For sake argument, if you had two identical trains designed with poor aerodynamics, one at 100mph and one at 140mph then you can double the energy cost. But if you take two different trains with one designed to be more aerodynamic, at the same speed they wouldn’t have the same energy cost as the second has a better profile?
Plus theres less friction from needing to be on a rail.
So I think saying its double the cost of transport is too simplistic to be meaningful in this discussion
It's more than that - doubling air resistance only doubles the energy use if it's the only inefficiency on the train (e.g., no losses in the magnets, HVAC, lighting, etc.). Add onto that the fact that you're basically eliminating rolling resistance from traditional trains when switching to maglev, and the expected outcome should be much less than double.
Finally, the most important part, each high speed rail route of any meaningful distance has the opportunity to displace a certain amount of air travel, so big picture, HSR results in a significant decrease in overall energy consumption.
Is that factoring in the always on cooling of the magnets?
Here's an article about the subject, paper linked at the bottom of the article: https://phys.org/news/2010-12-high-speed-pollute-percent-traditional.html
Thx, as I understand it, this is calculated for traditional railway technology and does not have anything to do with to maglev.
Maglev requires superconductors to work. They must be cooled to just a few degrees above absolute zero (typically ~ -270 celsius) and if they ever warm up beyond their critical temperature, catastrophic failure is the result. (this is called quenching which can destroy the superconductor permanently) So not only can you only drive maglev trains (which are expensive themselves) on maglev track and can only drive mag lev trains on maglev track, its far more expensive to build and maintain superconducting infrastructure than it is to lay down some steel rails. Maglev trains are used because the only friction that they experience is from air resistance. Theyre much faster than normal trains but it takes a lot of energy to keep the superconductor that makes them work cool, costs a lot more to build and requires a lot of electricity to get them up to speed. (They can use regenerative braking to recover much of this but its still an energy intensive process)
fwiw LN superconductors that operate at much higher temperatures are already being built https://eandt.theiet.org/content/articles/2021/01/superconducting-maglev-train-unveiled-in-china/
Also, China manages to charge only $8/ticket for the shanghai maglev, so evidently it can be done cost effectively.
If you subsidize anything enough it can be cheap for people to buy. That doesnt mean that its actually cheap to build and maintain. And the reason why temperatures are kept far below the critical temperature is due to the critical magnetic field and critical current decreasing as temperature increases even below the critical temperature
Is the Shanghai maglev perhaps subsidized?
Japan is in the late stages of developing a maglev section of the Shinkansen. It has liquid helium cooling for semiconductors and lots of considerations to make sure the cabin and surroundings aren't exposed to very strong magnetic fields. It's just more expensive to do all that.
After Japan rolls this out and works out the kinks, it might get cheaper since a lot of they've done a lot of the development.
Maglev's top speed record is just 5% faster than conventional train speed record. Thus if Maglev is more than 5% more expensive, then it doesn't make any sense to build them.
Speed records aren't usually representative of regular use top speeds, are they?
Well, if we look at actual maglev deployments in the real world, then they are much slower than conventional trains. All of them top out at 160kph, while conventional trains going below 200kph don't even count as high speed. There's only one Maglev line in the world which actually goes fast. So if we want to talk about regular speed representation, maglevs are slow and useless.