London’s Hidden Cable Tunnels Could Warm Thousands of Homes
Fnord666 writes:
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.
"It's very difficult to identify exactly how many cable tunnels there are in the world," says Graeme Maidment, an LBSU professor of air conditioning and refrigeration engineering who led the work. But cable tunnels lie below most major cities. Several tunnels are now under construction in London, and the UK likely has tunnels spanning several hundred kilometers, he says.
[...] But capturing heat from underground cable tunnels provides an extra-strong business case, Maidment says. Not only could the power distribution company sell the waste heat, but "cooling the cables reduces their resistance so you can put more juice through them."
[...] "We now need to take this from a desk study to some practical demonstrations," Maidment says. "There are lots of high voltage cables so there is safety and risk that needs to be considered." But, he points out, "what we're proposing doesn't necessarily need a large cable tunnel. It could be any power cable running in the ground and you could put a pipe next to it to absorb heat."
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