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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."
(Score: 2) by drussell on Monday September 16 2019, @02:24AM (1 child)
In dense downtown urban areas in locales where it gets cold in the winter, part of what keeps the streets clear of snow and ice in those areas is the radiant heat of things like underground distribution cables and transformers (usually vented through the sidewalk around here), plus the radiant heat of the buildings themselves, especially if they go down 7 stories into the ground for a car-park. :)
Of course, I suppose it also makes you sweat a bit more while walking around downtown in the summertime?
The "waste" heat could ideally probably be better managed than having any significant portion of it just dumped to the atmosphere, although that could be said for every heating or A/C unit anywhere that ever creates or moves heat. We could, in theory, sink all waste heat better to somewhere for storage but that is a practical implementation nightmare for most things. Maybe on a Mars or Moon base :)
(Score: 0) by Anonymous Coward on Monday September 16 2019, @04:08AM
Probably not until we get the space elevator working. Then, you'll need about a quarter million miles of pipe with a lot of flexing for ducting to the moon . . .