Cooling the Tube
Dealing with the heat on board the trains of London’s nearly 150-year-old Underground system has been a problem, especially in summer. The problem is that heat generated by conventional air-conditioning has to go somewhere.
Transport for London is working on multiple solutions, including improving existing ventilation shafts; tapping into underground aquifers to create water-based heat-exchange systems, and “hydro cooling,” using ice reservoirs and fan units.