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A lot of comments about heat sources in cities. I learned something interesting yesterday, when I came into work soaked and complained about how hot Boston's P

A lot of comments about heat sources in cities. I learned something interesting yesterday, when I came into work soaked and complained about how hot Boston's Park Street Station is. An older (70s) coworker mentioned that when he was young, Boston subway (T) stations were the place you went to cool down, as they were underground. Once they added AC to the subway cars, they dumped all their heat... into the stations. And now they're a furnace.

paganel 13y ago
Thanks for this, now I understand why Barcelona's subway stations felt so hot to me (while the subway cars themselves were cool). I live in an European capital more to the East where the subway stations are still a very nice refuge when temperatures reach 38-40 degrees in summer.
twistedpair 13y ago
They also use dynamic breaking resistors to the convert kinetic energy of the trains into heat energy. Fans then blow across the resistors to cool them. In Park Street, this just ads to the inferno. It is at least 120F in there in the summer. I'll bring in a theromometer one of this summer afternoons.
- tanzam75 13y ago
  > They also use dynamic breaking resistors to the convert kinetic energy of the trains into heat energy. Fans then blow across the resistors to cool them. On subways, the electricity generated by dynamic braking is sent back into the third rail (or the overhead wiring). It does not get wasted in resistive grids. The resistive grids that you're thinking of are used by diesel locomotives, which do not have a convenient electric grid to dump the electricity into. Thus, they have to send it out into the atmosphere as heat.
lmm 13y ago
Here in London the tubes aren't air conditioned, but are still exceedingly hot. I'm told that new tunnels are cool but over thirty or so years they gradually warm up, and so there's a noticeable difference between the older lines and the newer ones (less so at the moment as we haven't built a new line for thirty years, but that's another discussion). It also causes some interesting engineering challenges as the clay slowly dries and bakes around the tunnels.

paganel 13y ago

Thanks for this, now I understand why Barcelona's subway stations felt so hot to me (while the subway cars themselves were cool). I live in an European capital more to the East where the subway stations are still a very nice refuge when temperatures reach 38-40 degrees in summer.

twistedpair 13y ago

They also use dynamic breaking resistors to the convert kinetic energy of the trains into heat energy. Fans then blow across the resistors to cool them. In Park Street, this just ads to the inferno. It is at least 120F in there in the summer. I'll bring in a theromometer one of this summer afternoons.

tanzam75 13y ago
> They also use dynamic breaking resistors to the convert kinetic energy of the trains into heat energy. Fans then blow across the resistors to cool them. On subways, the electricity generated by dynamic braking is sent back into the third rail (or the overhead wiring). It does not get wasted in resistive grids. The resistive grids that you're thinking of are used by diesel locomotives, which do not have a convenient electric grid to dump the electricity into. Thus, they have to send it out into the atmosphere as heat.

lmm 13y ago

Here in London the tubes aren't air conditioned, but are still exceedingly hot. I'm told that new tunnels are cool but over thirty or so years they gradually warm up, and so there's a noticeable difference between the older lines and the newer ones (less so at the moment as we haven't built a new line for thirty years, but that's another discussion). It also causes some interesting engineering challenges as the clay slowly dries and bakes around the tunnels.