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: 1, Touché) by Anonymous Coward on Monday September 16 2019, @01:46AM
Just like SDG&E getting free power from everyone's excess home solar panels but jacking up the rates saying they're not making enough profit.
(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 . . .
(Score: 1) by sfm on Monday September 16 2019, @03:04AM (2 children)
Finding a use for the waste heat is good, 400kW is nothing to sneeze at.
Might be worth looking at the economics of larger cables/higher voltages
for these power cables? Effectively turning waste heat into high quality
usable electricity.
(Score: 2) by legont on Monday September 16 2019, @03:48AM (1 child)
Last time I checked, it takes 36,000 kWh to mine one bitcoin. https://steemit.com/bitcoin/@penguinpablo/how-much-energy-does-it-take-to-mine-one-bitcoin-march-2018 [steemit.com]
"Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
(Score: 2) by kazzie on Monday September 16 2019, @08:11AM
So, does that mean we're looking at under-floor heating for roads and pavements?
Why, in London the streets are thawed with bitcoin!
(Score: 2, Funny) by jmichaelhudsondotnet on Monday September 16 2019, @03:29AM
See, I've been telling everyone we need to hook everyone together with tubes and yes, they laughed. Until today.
This entire time free cable tunnel waste heat has been 100 feet away, you just didn't upgrade your tubes like someone living in 2005 or something. 2019 people know the criticality of open air tube connectivity. Get with the program.
Of course this will make it a lot easier for the nanobots to get to you while you're sleeping so that's a downside.
(Score: 0) by Anonymous Coward on Monday September 16 2019, @03:47AM (1 child)
Alluded to at the end of tfs, "...you could put a pipe next to it to absorb heat." For safety, I don't want to share the same air that goes through the cable tunnel, if there is a fire or other nasty release down there it should stay down there and not come into my house!
(Score: 2) by FatPhil on Monday September 16 2019, @01:16PM
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2) by progo on Monday September 16 2019, @02:56PM
"Several kilometers"? You don't say.