London’s tube system is literally heating up the city – and that’s a problem. A hundred years ago their subway stations were places to cool down during hot summer days and people had to wear sweaters while commuting. Today, this is no longer the case. The trains are heating the earth which in turn makes the entire tube too hot.
Cooling the tube is now a pressing issue and nifty ideas are being tried. New systems being tested tend to be green and benefit other parts of the city. Basically they are trying to transfer the heat to places that want it to save costs.
An experiment in Islington is trying that very thing using heat from the tube tunnels to warm up a municipal heating service provided to a housing estate. The advantage of this scheme is that it can remove heat in winter when it’s needed above ground. It may seem mildly annoying that surface users don’t want heat in summer when you’d think the tunnels are at their most oppressive, but in fact removing heat in winter helps during the summer.
If the clay surrounding the tunnel can be cooled in winter, it has more capacity to absorb heat in the summer.
As it happens, at this particular trial, the fans can also be reversed so that during the summer months, they can suck cool night time air down into the tunnels as well.
Very interesting topic you bring up.
I was a graduate student in London from 1969 to 1974. In summer the Tube was almost unbearably hot even then, with everybody sweating pints and the body stink was pretty bad as well. So this is hardly a new problem.
Having experienced the Montreal Metro in the summer of 1967 for Expo and finding it unbearably hot, as an engineering student I hypothesized that the use of rubber tires with their inherent hysteresis, and thus heat generating properties (just like your car tires get hot from bending and flexing as they turn) was the source of the problem. That and the French design meant that the engineers over there had no idea how stinking hot Montreal could get in summer anyway, and so proper ventilation had never been considered.
I expected London with its much more efficient steel-on-steel rolling stock wouldn’t have been as bad as Montreal, but my assumption was incorrect. The much higher frequency of trains and the heat generated by electric motors and especially brakes plus thousands of passengers made up the difference of the rubber tires in Montreal easily. In London, there were times I wanted to scream it was so unbearable, like a form of torture.
So now, over 40 years later whatever entity it is that runs the Underground has finally woken up apparently. Amazing. It recalls the old adage about how many times you have to get hit on the head with a hammer before you notice enough to try and do something to alleviate the pain!