Air conditioning will be introduced on the sub-surface lines, with a novel air-cooling system to be trialled on the deep tube lines.
Part of the PPP contract for the subsurface network upgrade (Circle, District, Metropolitan & Hammersmith & City lines) included an option for air-conditioning on the new trains to be rolled out across these lines. This option will be exercised as part of TfL's 5-year investment programme.
Air conditioning is relatively easy to introduce on these lines which have large tunnels where heat released from air-cooled trains can be dispersed.
The new trains will be delivered from 2009 starting on the Metropolitan line, and should be in service across all four lines by 2013.
Deep tube lines
Proper air conditioning of trains and underground stations on these lines is so difficult it would be prohibitively expensive. This is because there is no easy way of dissipating heat from air conditioning units - the tunnels (the oldest deep tube tunnels in the world) are generally too small.
The small size of the tunnels also means that air conditioning units cannot be fitted on the similarly-sized trains, unlikely more modern air-conditioned tube systems such as Singapore.
The geology of the area also means that some tube lines are insulated by the clay they were tunnelled through.
However, the Mayor ran a competition last year with a £100,000 prize for someone who could come up with a workable method of significantly cooling the deep tubes. As a result, London South Bank University is now working on a pilot project with London Underground to use the thousands of litres of ground water which must be pumped out of the deepest parts of the system every day.
The pilot system at Victoria station's Victoria line platforms involves using water pumped from the nearby underground River Tyburn. 200 litres per second will be drawn from the river and pumped between the platforms. Fans will draw hot air from the platforms across the pipes, cooling the air and heating the water. The heated water will be pumped out to the Thames where it will cool rapidly. The air cooling effect is predicted to be about 5°C.
A £100,000 prize which the Mayor offered to anyone who could come up with a workable solution for cooling the Tube in the summer has gone unclaimed, as none of the 3500 entries were deemed workable - although TfL are currently working on improved ventilation, and on a water-cooling project with London South Bank University.
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