4 ms·

But wouldn't this make the problem even worse? Air conditioning will dump even more heat into the tunnels.

• Symbiote 3y ago
  See the 10th paragraph of the article.
  • ocharles 3y ago
    For those who won't bother to RTFA: the trains run cooler than other trains, so they are taking advantage of the difference such that the net result is the same temperature in tunnels, but the interior of trains can be cooler.
    • onetimeuse92304 3y ago
      Oh, so this is exactly like budgeting. It does not matter a lot how much something costs, what matters is where the money came from. Here we improve the trains to emit less heat and immediately spend it on air conditioning. In the meantime the debt (tunnel excess heat) continues to rise and somebody else in the future will have to pay for it.
      • NamTaf 3y ago
        It's more like budgeting at a home level, in that you have a set limit of heat that you can spend, and choosing to spend it less on equipment like brakes, traction motors, etc. and more on air conditioning means still remaining in budget. Their overall limit of heat output by the trains remains the same. The tunnels won't be any hotter than they are now, thanks to savings found in other systems.
        • onetimeuse92304 3y ago
          No, it is more like government spending. It is like saying, "we need to be fiscally responsible and that means only spending no more than 160% of what we are earning". The tunnels are getting hotter and hotter. Saying "the tunnels won't be any hotter" is completely unfounded in reality.
          • NamTaf 3y ago
            Reading a bit more into this, I'm still not sure whether the tunnels are actually continuing to meaningfully increase absent external changes to the system. Is it at a steady-state heat flux between the inputs (passenger, vehicles, infra) and output (into the surrounding earth), or is the surrounding earth still not effectively saturated? I know heat inside the tunnels fluctuates with time of year, but I can't tell if year-on-year the tunnels are getting e.g. 1xx% hotter and, critically, what the causes are (more tph will obviously, global warming will, more pax will).
• cjrp 3y ago
  Given that the trains stop at the platforms within quite a small area, I wonder if they could store that heat between stations and then dump it into a sort of extractor which takes it to the surface (or uses it to heat buildings, etc.)
  • onetimeuse92304 3y ago
    That would be very complex and expensive. Technically, you could just pump out hot water and pump in some cold water, on every station. But achieving reliable coupling between the train and any kind of piping system would be complex. Remember, there is electricity involved already and you don't want to mix leaking pipes and electricity. When you realise you have to do something very reliably on every train stop, on every car a more passive solution like piping cold water through the rock might be cheaper long term.
    • hlandau 3y ago
      I was just thinking about something like this. I'm not sure you'd actually need to have physical coupling from the train to the platform. Train lavatories used to just dump their contents out of the track. Given that tube trains are already required to stop at a very precise location on the platform, perhaps the hot water could just be dumped into a funnel built into the ground underneath the track beneath the rails. Getting cold water onto the train would be harder. Perhaps a big funnel on the top of the train underneath a pipe? ;)
      • cjrp 3y ago
        For the cold water, fill them on top like a steam train!