Regarding the heat generated from braking. I was surprised to find out that in our (very small) subway system the stations are higher than the rest of the track. This slows down the train as it is approaching the station and helps it regain speed when it leaves the station. A quite obvious idea, but must admit I might have not thought about it.
In some cities they are building district cooling [1] (comparable to district heating). Might be quite a difficult solution in densely built areas of course.
In some cities they are building district cooling [1] (comparable to district heating). Might be quite a difficult solution in densely built areas of course.
[1] https://en.wikipedia.org/wiki/District_cooling