Tube aircon

London Underground say they can't install aircon on their tube trains for a myriad of reasons, including that the trains aren't big enough to install aircon units, that aircon will only succeed in redistributing the heat, etc.

I have an idea for a scheme which might be a technical challenge to implement, but it could work.

There isn't enough room on trains for aircon, but there is plenty of room at stations. Under the track at stations, there is a "suicide pit". This is become less necessary as some stations (new ones anyway) start to get platform edge doors. The suicide pit can be used to install refrigeration units that take air from the station, cool it, and compress it for storage. When a train arrives at the station, the cold air is released as a quick blast into the train, giving welcome refreshment to the passengers. Since trains would arrive at a new station about every two minutes, they'd get a regular supply of colder air (better than nothing at the moment). More air could be cooled at stations in between trains. The hot air produced by the aircon units at stations would be expelled through the usual ventilation systems.

The difficult bit would be getting the cold air into the trains. Maybe the trains could receive the cold air somehow and gradually release it into the train through the ventilation systems. But if they could make mailtrains that grab post bags off posts as they speed by 100 years ago, I'm sure this isn't an insurmountable problem.