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this post was submitted on 07 Aug 2023
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A mag lev train doing 500+mph is going to need a lot more energy than a normal train. It will probably be less than the plane but I'm thinking it won't be as much less as you might think.
Thae train is also doing those speeds at sea level vs the plane doing them at 35,000ft or higher, where there's less than 1/4 the atmosphere to fight.
It's way less than planes wayyy less than lots of cars. In fact maglev trains use less energy than normal trains. This is because they do not make direct contact with the track, and less energy is required to pull them.
How much is required to keep it floating?
At 480 km/h (about 300 mph) 0.4 megajoules per passenger mile, all things combined including power to track, according to Stanford. Also apparently the energy needed increases at lower speeds due to something about lift.
For reference https://vaclavsmil.com/wp-content/uploads/2019/03/January2019.pdf says
So 6x is still a big difference. Not sure what I expected, but maybe this is smaller.
Trains don't leave exhaust in the upper parts of the atmosphere, though, and depending on how the electricity was created, it could be neither did its energy source—though I suppose there's no avoiding that manufacturing any kind of plant and the train itself did cause emissions.
@flux @QuinceDaPence Concrete and steel (for stations, track, etc) matter. So does the electricity used to maintain stations, not just propel the train. So lifecycle emissions of a train are immensely complicated, plus then you get into how to route a new rail line without destroying too many ecosystems.
Even so, clean electricity is the easy bit compared to making planes clean. More trains please.
@flux @QuinceDaPence The other common gotcha with new train lines (e.g. HS2) is:
What if we get a modal shift from internal flights to trains? If air demand is constrained by supply (i.e. landing slots), that means there will be more long-haul flights, and overall emissions increase!
There is some truth in this. But it just means we need to drastically reduce our aviation capacity, and increase prices, at the same time as building more train lines. We could start with a frequent flyer levy.