Batman55 wrote:
It seems odd that as LUL attempts to cool down the tube, it is introducing
giant electric projectors at many stations, along with the illuminated
moving panels on the escalators. The stories in Railway Herald this week,
page 5 about cooling down, and page 6 about the heat producing equipment,
seem to show a lack of joined up thinking!

What might be more sensible is for equipment at every sub surface station to
be reviewed and every heat producing item examined to see how its heat
output could be reduced or eliminated. Every little bit might help!

MaxB


According to TfL, the heating effect arises because of the incremental
heating and cooling caused by each passing train's energy consumption.
The frequency of trains means the cooling of the tunnel walls is that
little bit less than the heating, so over the years the ground heats up
because it never gets a long enough break between trains. This is
rather borne out by the original Bakerloo Line claim that it was an
nice, cool way to travel in the heat of the summer - it was decades
before the effect was realised. Presumably if you could shut the tube
for a few years you could reverse it, but I can spot a couple of
problems with that idea.

I suspect, therefore, that things like lighting and electronics in
stations (which are better ventilated than the tunnels anyway) are of
minute benefit compared with reducing the heat produced in the tunnels
by each train by a little bit. Indeed, one of the ideas being looked at
is blowing cold air over the brakes of trains standing at stations, so
they don't take the heat into the tunnel when moving off. Obviously
this merely transfers it to the station, whence it can be removed
somewhere. Regen braking has a place here, too, if you can shove the
heat from the necessary resistors outside.

Tom