Air conditioning on deep level Tube

I presume you're talking about TfL's press release which can be read at www.tfl.gov.uk/tfl/press-centre/press-releases/press-releases-content.asp?prID=358

Certainly there's reference to air cooling in the new Sub Surface lines trains, but air cooling and air conditioning aren't necessarily the same thing. Time will tell.

Heat extraction on the SSL's is relatively simple - there's many areas where the lines are open to the 'outside' so the build up that occurs on the deep tube lines (see below) isn't the same issue.

As for the deep tube lines, this is an altogether more complex problem. OK, they may technically be able to air cool the trains (and again presumably that would be in the new stocks whenever they arrive) but the problem in the deep tube sections is the dissipation of the heat once it's taken away from the trains. This builds up in the stations and tunnels and in turn leads to even more heat build up!

As you'll have read from the press release they're looking at ways of improving ventilation and extraction, and this will help, but as the press release suggests by the results (or lack of) of the competition which was held it's all incredibly complex.

When I was on the Berlin S-Bahn the stock with double glazing had, on the inside at the bottom of each window, a perforated grille that let cool air enter the car while in motion The air was brought up through trunking between the two car skins from under the car. This was very effective and brought a nice cool breeze in the hot weather.

My own thought would be to have new SSL stock with the same body design/seating plan as the old Tanks (F Stock) brought up to date with moder equipment and double glazing. The large square vents on the rooof of the tanks were so effective they had to be blocked off.

Another way to ensure adequate ventilation is the old style clerestory roof as on the older stocks of years gone by. Hot air rises (except in the Commons) and the clerestory was excellent for venting it. If fans were used in conjuction with it the problem MAY be solved. It may look old fashioned but the old guy knew a thing or two.

As for stations there is a way and that is to install extractor trunking on the platforms and run the trunking to the surface via the lift/escalator shaft. These fans could be boosted by the over-current from the regen brake on the trains. I.E. the fans run at traction current voltage and and speed up when a train in section pumps juice back in to the rail.. Only an idea.

I remember reading something about this last year as a result of the contest for cooling the tube by the mayor.

It was either an idea which used water from the thames or an aquifer.
It's possible to take heat from the tube and store it in an underground aquifer (waterbearing layer deep below ground) during the summer and extract it during winter for heating buildings, or just let it dissipate into the air via a heat-exchanger. I've visited a project where they did this with a number of large officebuildings.