Underground river to cool the London tube

The "Cooling the Tube" competition in 2003, promising GBP 100 000 to those finding a workable solution to cool the Tube, received 3400 entries. Modern systems with large tunnels and surface lines can be cooled using air-cooling systems. However, with deep lines, the heat cannot escape from the system because there are too few ventilation shafts and the tunnels are surrounded by clay, a very good insulator. One method, researched by London Underground's engineering department and the South Bank University, and to be tested at Victoria station, is to draw on the millions of gallons of cold ground water pumped out of the deep tunnels each day. The water, extracted at 14°C, will be piped through the tunnels into heat exchangers; fans will blow hot air from the stations across water pipes, causing the water temperature to increase by a few degrees as it extracts heat from the air. The cooler air will then be blown back onto the platforms and the water pumped into the Thames. Summer rush-hour temperatures are expected to be reduced by 5-6°C.