Hot power cables snake through tunnels and channel under cities all around the world. All it takes is a fan/air coil to capture that heat for buildings. Researchers and a power company in the UK calculate that the essentially free heat could warm thousands of London homes. An anonymous Slashdot reader shares a report from IEEE Spectrum: Underneath London's bustling streets lie several kilometers of 2.5-meter-wide concrete tunnels lined with power distribution cables that can reach blistering temperatures. To cool the tunnels, vertical shafts spaced out every kilometer or two supply fresh air and eject hot air out into the open. Researchers at London South Bank University (LSBU) want to put that waste heat to use. A typical 1.8-km tunnel stretch between ventilation shafts produces 400 kilowatts of heat, enough to heat 100 homes or a small commercial office, they have found in a preliminary analysis done with the city's electricity network operator UK Power Networks. This heat recovery scheme would have a third of the carbon emissions of a gas boiler delivering the same amount of heat. The researchers presented this work at the International Congress of Refrigeration in August. [...] A heat exchanger installed at the supply shaft reduced cable and tunnel air temperatures by 8 degrees Celsius, but the amount of heat recovered varied from about 100 kilowatts in colder months to 460 kW in high heat. Installed at the exhaust shaft, the system produced around 400 kW during all six months.
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