London's Hidden Cable Tunnels Could Warm Thousands of Homes (ieee.org) 57
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.
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.
Heating a small business! (Score:3)
Now tell me *that* doesn't ... er ... blow your skirt up.
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Now tell me *that* doesn't ... er ... blow your skirt up.
What!? Subsidize small businesses the tax man deems *"the rich" with free heating!? Besides, who do you think we plan to be the ones financing a large portion of the costs for this system? Who do they think they are, being the largest employer, anyway? The nerve! Especially when large corporations are much easier for corrupt politicians to enter into a crony-capitalist relationship with to fleece the people more efficiently and assure re-election campaign donations, and today with the added bonus of the opp
when trying to solve a problem... (Score:1)
It may be good for some startup looking for money, a startup that may fail, but it won't fail to impress some people and get money "invested" in their not-so-cool (pun intended) idea.
Re:when trying to solve a problem... (Score:5, Insightful)
You're right, it's best to focus on low hanging fruit, like recovering wasted energy that already exists. Or do you also build a wind farm outside your house to power your AC rather than installing ceiling insulation?
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Re:when trying to solve a problem... (Score:5, Funny)
Just buy a damn ladder and pick whatever fruit you want.
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bullshit. the low hanging fruit is harvesting raw energy
You mean raw energy like heat? Yeah I agree. This really is low hanging fruit. I'm not sure what you're arguing about.
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Whether it's viable and successful or not I love that someone's had this thought and is properly exploring it.
This is like trying to get some fat from the beached whales that turn up every morning in your secluded cove. Sure, you're going to try and prevent them getting beached but in the meantime there's some lovely blubber to be had.
Re:when trying to solve a problem... (Score:4, Informative)
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What? There's already heat being generated and wasted, there are very nearby homes and businesses that need heat - and you want to build a wind farm *in London"? And this is somehow easier?
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..It's better to focus on the low hanging fruit (wind, solar, etc.) because it has the most returns.
The base problem there is that unless you locate the generation near to the homes it will be used in, you still need to transfer that power over transmission lines.
It's the transmission lines with the inefficiency, the generation method just has to generate more to deal with that fact.
At least with current tech, anything with the ability to generate enough power for baseline is already physically huge and can't practically be located near homes.
Solar panels are getting there the fastest, but even they need
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..It's better to focus on the low hanging fruit (wind, solar, etc.) because it has the most returns.
Does it really? How do you know? Have you done the testing and analysis needed to work out the cost per BTU of recovered heat, and the comparable cost for collecting, transmitting and converting wind or solar energy?
It makes perfect sense to test ideas like this to see how practical they are. If they turn out to cost more than adding wind/solar generation plus necessary transmission and conversion infrastructure, then they won't be implemented.
Benefits might be lower, and elsewhere (Score:2)
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The cables are already cooled. This isn't talking about changing that: just changing what happens to the air after it's cooled them.
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They were just future-proofing their infrastructure for when they'd need heated underground tubes.
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The current capacity of a cable given its resistance, cross section, cladding, environment, and maximum temperature has been very well established for almost 100 years. Operating temperatures which seem extreme to a layman are actually routine. If there was economic gain to be had, they would use thicker cables.
Because of cost (Score:3)
The problem with ask these kinds of schemes that involve new urban infrastructure are that it's very hard and expensive to do. The UK is terrible for it.
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Yep. The cost of getting this to those homes is probably hundreds of times what it costs to heat those homes. Plus they'd have to figure out how to charge money for it. Nobody will get it for free.
One plausible use might be to feed it into a hospital or something like that.
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The problem with ask these kinds of schemes that involve new urban infrastructure are that it's very hard and expensive to do. The UK is terrible for it.
Oh, the UK doesn't have a monopoly on this. Take a look at the Boston Big Dig [wikipedia.org] or Berlin Brandenburg Airport [wikipedia.org] for examples.
Could we maybe turn this into an Olympic Sport . . . ? Who can still run a project that is over budget and over time for how long . . . ?
Re:Because of cost (Score:4, Funny)
A company I did some work for once spent three years getting permission to install some small radio repeaters on lamp posts. The council didn't even have anything in place to deal with such a request when they started.
After three years they eventually got the go-ahead. Took another year to install the devices because they had to notify residents not to park in each road on that day while they did the work, in case they dropped one on someone's car.
Eventually they switched the system on and it worked well for about three months and then half the system went down, and a week later the rest of it. Sent someone to investigate and they couldn't find the devices, they were just gone.
Turns out the council had contracted someone else to replace all the street lights with new poles, and the old ones had been scrapped with the radios still attached.
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Turns out the council had contracted someone else to replace all the street lights with new poles, and the old ones had been scrapped with the radios still attached.
[John Cleese Fawlty Towers voice] Brilliant!
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So we will turn it off in the winter.
Missing context / big picture (Score:3)
Back of the envelope calculations indicate that office buildings with appropriate level of insulation would require active cooling in every season (average human is equivalent to a 90W heater, require about 15m2 of insulated building surface to counter the heat gain). However residential homes have a much larger ratio of external surface area to people than office buildings.
From: https://www.london.gov.uk/site... [london.gov.uk]
"The main consumers of heat in London are the residents of London, who consume energy for the heating of homes and for their domestic hot water needs. There are other consumers such as commercial buildings, offices, community centres, schools and hospitals. Overall, as a city we consume 66 TWh/year for our heating needs, while there may be as much as 50 TWh available from existing heat sources in and around London to supply our heat networks."
So this is part of taking heat from A to warm up B - where B could be apartment blocks.
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If the building is designed to take advantage of physics rather than fighting it, it won't take any energy at all to get the heat out of the building, since heat rises. You just open some shutters...
220kw/kilometer ?!?! (Score:4, Interesting)
That's a massive amount of of wasted energy!
So, back of the envelope... I'm going to oversimplify and assume a single major cable carrying electricity: we're talking about 220 watts per meter of cable. Assuming a wholesale electricity price of $0.05, that's $100 of electricity per meter per year. Do nothing more than putting in a parallel cable, to cut resistance in half, and you save $90 per meter per year, plus whatever savings you get from the reduced cooling effort. A quick search shows that high voltage power transmission cable costs around $20 per meter per conductor.
Seems like it would be worthwhile, no?
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$1.5 million/mile for a new 69 kV underground line (https://www.power-grid.com/2013/02/01/underground-vs-overhead-power-line-installation-cost-comparison/).
Closer to $1000/meter installed - the installation is the big cost not the actual conductor. A 10 year payback seems about right for that kind of infrastructure.
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$1000/meter installed? Does that cost include all the digging or tunneling for a completely new installation, or is that the cost to run new cables in existing tunnels?
No. Undergrounding [wikipedia.org] is typically more expensive because of installation labor costs and cable insulation requirements, but it's only approaches $1000 a meter through existing conduit if the contractor is the mayor's brother-in-law, or some such.
One calculation:
Above ground lines cost around $10 per foot and underground lines cost in the range of $20 to $40 per foot.[7] In highly urbanized areas the cost of underground transmission can be 10–14 times as expensive as overhead.
New construction is another matter:
A typical new 69 kV overhead single-circuit transmission line costs approximately $285,000 per mile as opposed to $1.5 million per mile for a new 69 kV underground line (without the terminals). A new 138 kV overhead line costs approximately $390,000 per mile as opposed to $2 million per mile for underground (without the terminals).”
Not viable. (Score:2)
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So perhaps use the waste heat to heat water, as people generally want hot water for cleaning etc even during the summer.
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Hot (Score:3)
If you look at large older buildings in cities, often they are heated by steam piped in from power generation plants' excess heat. That's the source of steam coming out of manhole covers.
Almost like Olden Times Chicago (Score:2)
Communication tunnels under Chicago, ages ago, provided cool air for theaters and other businesses. Not sure if it helped in the winter, but it should have.
remember the steam pipes (Score:2)
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Tax anyone that lives near the tunnels on the off chance they might benefit from the waste heat near their building being absorbed.
And such tunnels are often full of asbestos. (Score:4, Interesting)
And such tunnels are often full of asbestos. OLD asbestos materials, that are breaking down.
Add bowers to push more air past it and then through my house or office? No, thanks!
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I thought the same thing until I saw they intended to use heat exchangers to avoid this. Likely not as efficient as just blowing that air into a building but avoids the problem of sucking in whatever foul odors might be in the tunnel.
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Add bowers to push more air past it and then through my house or office? No, thanks!
What on earth makes you think they would pump stale air from underground into a building? Here's a tip in the future. If there's something so offensive about a proposal that the very idea instantly makes you freak out and say "no thanks" including exclamation mark then there's a good chance you didn't actually understand the proposal, or in this case, didn't even read TFS.
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What on earth makes you think they would pump stale air from underground into a building?
Good point. The summary refers to heat exchangers, while TFA mentions the ones in the study were air-water (with a several degree heat loss).
I'd be OK with air-water for a working system, delivering the heat as heated water (or similar fluid) - and taking another temperature hit when again heat-exchanging with building air or pool/plumbing water..
Air-air, though, while an improvement on blowing tunnel air through inhab
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Examples of air-water heat exchangers are automotive radiators, automotive heater cores, hot water baseboard radiators, and the like. No heat pump. Just a water (or other working fluid) pump and maybe an air blower.
Counter-current heat exchangers, where the fluids (both liquids and gasses are "fluids") flow in opposite directions, are the btest at transferring the heat from one fluid to another. If the two fluids are pumped at equal heat capacity per second, they come close to exchanging their temperatur
Have they screened for Radon yet? (Score:2)
I would be pretty wary about piping air from deep underground tunnels directly into people's houses, lots of bad trapped gases could originate... maybe if they took the air to some kind of heat exchanger to warm water or something for radiators it would be better.
Not good for everyone (Score:2)
I'm sure the homeless people who hang out around the current vents will love losing their heat source.
Crypto miners did this first (Score:2)
I remember seeing "heating" services, where they would install a crypto mining machine at your home (completely sealed) and granting you free service (in return for hosting the device).
I was a bit unlucky, when I experimented with them it was the spring-summer time. I had the opposite problem of trying to get rid of heat. However if the crypto craze had gone into the winter time, I was looking forward to some free heating for myself.
Other appliances at home might have similar effects. The oven, dishwasher e