"The average temperatures on the Victoria line have risen by almost seven degrees since 2013 – nearly a *30%* increase.
Conversely, the increase in the average annual temperatures across all Underground lines from 2013 to 2024 was merely *seven percent*, placing Victoria’s temperature rise vastly above that."
Using percentages to talk about changes in non-Kelvin temperatures is crazy.
28 degrees Celsius is not 30% warmer than 21 degrees Celsius. This same stat rendered in Fahrenheit would say 70 degrees -> 82 degrees, or 17%. In kelvin it would be 294 -> 301, or 2.3%
Or we could invent a new measure indexed to Celsius but offset by 20 degrees, and declare a 1 -> 8 change, a whopping 700%.
Feynman was complaining about this error appearing in textbooks back in the sixties[0].
The trouble (of course) is that Celsius properly is not a proper unit, but a "scale", or a "unit of difference" (equal to kelvin), or even torsor[1].
The trouble with the kelvin here is that if you see the 7 kelvin increase as a proportion of the 295K starting temperature the you only get a 2% increase. Nobody is going to buy your newspaper if you're putting up weak numbers like that.
To make matters worse, not all ranges and percentages on that scale are equal, whether they're the same in absolute or relative terms. Humans have a narrow relevant "operational" temperature band. Even 20 degrees between 10-30C feel like nothing compared to the 5 degrees between 37-42C.
Humidity in London is also awful as the temperature gets closer to freezing. I found the damp cold in London to be common over the year and truly horrid (a reason to never live there).
At home (Christchurch, NZ) we often get dry cold which can be pleasant: however when we do get the occasional vile damp cold I personally call it "London cold" because it made so much impression upon me in my 20s.
Your upper band of 30C is making this Englishman sweat just thinking about it. Which I think proves your point about narrow operational temperature even further.
You’re right in principle but that’s probably the worst example you could have given. So bad an example that I think it could easily be argued to disprove your point.
For us people not living in Arabia or South Texas the difference between 37 and 42 Celsius is indeed quite important. 37 feels pretty hot, but yet livable, while 42 (and even 40 for me) means that nothing non-urgent should bring me out of the house.
Indeed. At 3C in London, the humidity seeps into every pore and settles into your bones. Riding a bike at 3C, unless you're wearing a balaclava and a ski mask, is an exercise in pure pain, as the wetness sublimating off your face has approximately the same effect on your facial nerves as being flayed.
Ok the other hand, -2C in London is crisp and invigorating and entirely preferable in every possible way.
There are few or no human scale situations where percentages of absolute temperature are meaningful, absolute zero is too far away and we live in a too narrow range of temperatures. Unless you're in a scientific context just don't use percentages on absolute temperature, only on rates.
It would definitely be crazy in Fahrenheit, but in centigrade I think it makes some sort of intuitive (if not scientific) sense. (Together with the sea-level assumption we always make in casual temperature discussion anyway.)
Maybe because I was brought up with centigrade it makes more sense to me. The centigrade number is how far you are from water freezing. If it goes up 100% then you are twice as far away. I'm not aware that doubling the fahrenheit number has a similar easy to understand meaning?
> The centigrade number is how far you are from water freezing
The Fahrenheit scale is how far your are from your own body temperature. It was designed that 100 is the temperature of a human. (Adjusted later to 98.6 due to inaccuracies.)
0 was designed to be as cold as you can get with ice and salt (also ended up being slightly inaccurate).
> Maybe because I was brought up with centigrade it makes more sense to me.
Yup. People brought up on Fahrenheit think it is superior. For temperature neither argument is objectively better. (In contrast to imperial distance measurement with non-powers of 10 and factions, where there are good arguments against it, with temperature both scales are ultimately arbitrary.)
The slope of the scales has no bearing on whether percentages are meaningful here. The problem with both systems when it comes to percentages is that neither system has 0 set to a natural 0. This leads to an entirely arbitrary point on the scale where decreases in the unit will approach a 100% difference and then suddenly start decreasing again.
If anything Fahrenheit should be less insane because at least the artificial 0 is likely to stay much further away in the data they're quantifying so the percentages stay reasonable.
The slope of the Fahrenheit scale matches that of the Rankine scale.
I would still say that the in the Rankine scale percentage increases make sense, and Fahrenheit changes to not.
The thing that matters isn't the slope, but the zero point; "X% farther from absolute zero" is a useful measurement, "X% farther from an arbitrary zero point" is not. Especially when negative or zero temperatures are involved.
In both it makes a sort of intuitive sense. 7% of the way from freezing to boiling is a meaningful way to visualise temperature; 7% of the way from ice melting in a bath of salt to slightly above Mrs Fahrenheit's armpit temperature is also meaningful, although perhaps a little idiosyncratic.
Edit: this comment was deeply stupid for obvious reasons and I regret trying to interact with other people when I should be asleep.
The issue is a percentage of a Celsius value is not that. For example, an increase from 1°C to 2°C is a "100% increase", but is only 1 percentage point from freezing to boiling.
You could say things like that with anything in percentages? 100% increase in your pension from 100k to 200k is only 10% (increase, to 20% total) of your target 1M, or whatever.
Yikes. I posted this, and I missed that, something I realised soon into my first year physics degree lab. I learnt more than just dipping calculators in liquid nitrogen for fun.
And they manage to make it even more crazy by also comparing it to average external temperatures.
==
The Victoria Line average temperature in August last year was 60% higher in temperature than the average external temperature that month, measured at 19.5 degrees.
==
Certainly for January it must have been hundreds of percent higher.
And what would the numbers be for e.g., the Moscow metro in winter months where the average outside temperature is negative?
I don’t know if I’m worried about it. While the measurement makes little scientific sense it makes intuitive sense, and, importantly, the intuitive implications are the scientific implications.
It’s a huge increase, if not for the reasons they describe.
Is it? I think it puts the Victoria rise in perspective to the other lines quite effectively.
Everyone knows where the zero is in Celsius using countries anyway and days in the negative are so rare in the UK you can discount them (plus they are none inside the tube).
> Historically, the Underground infrastructure offered a respite from warm weather, indicated in Austin Cooper’s ‘It is cooler below’ poster, issued in 1924 by the Underground group to promote a more comfortable experience of travel during warm weather.
A century of burrowing commuter-worms unfortunately managed to bake all the beautiful wet clay that kept the tunnels tolerable when the sun was shining about.
It seems straightforward to me that it would be enough to rehydrate the ground. Just need (approximately),
400km of track * 25m average depth * 3m tunnel width * 20% moisture content of wet clay
= 6 billion litres of water
Sounds like a lot but it's only about 1/300th of the yearly flow of the Thames.
I don’t think the hydration of the clay is the important element here. Rather I suspect it’s simple just the sheer mass of clay, wet or otherwise, that’s involved.
There’s a reason why ground source heat pumps work so well. It’s because the ground is such a fantastically huge heat sink/source that in most scenarios we consider it capable of sinking or sourcing a practically unlimited amount of heat.
Unfortunately one of the scenarios where this breaks down, is when you stick a bunch of tunnels in the ground, then pump a crap ton of energy into those tunnels years round, and expect the ground to sink all the heat away. Turns out, if you do that, the ground itself starts heating up, and given that clay is a reasonable good insulator, it’s like wrapping all those tunnels in wool jumpers.
I would point out as well that all these tunnels are “deep level” tunnels running at an average depth of 24 meters and getting as low as 67 meters. The heat of the sun on the ground surface will have approximately zero impact on the tunnel temperatures. 24 meters of clay is a lot of insulation to work with.
<man walks into sauna room> Ooh, it's a bit hot in here! I better throw some water on these rocks to cool them down.
Joking aside, I actually don't know how dry it is in the underground, and therefore whether adding water for evaporative cooling would work. I would have assumed it was quite humid, but maybe not?
It seems implausible to me that the clay is dehydrated. The Victoria line was only built in the 60s and has a waterproof lining. (It's also built with asbestos cement, unfortunately, which is no doubt a problem when they need to cut it for whatever reason)
Unfortunately, hydrating clay is extremely hard to do. Clay is what you use as a water-tight material in dams, artificial lakes, waste dumps and stuff like that, because water doesn't really pass through it.
Looking at the temperature chart and the significant drop in 2020 during the pandemic, the source is certainly the trains and people themselves. (fewer trains moving, less heat added back then). At this point I expect the infrastructure is heat soaked and will need a prolonged period of cooling to bring temps down. i.e. don't expect instant results.
Moving more air through the tunnels, adding A/C systems - both have a problem of needing room up on the surface for blowers and compressors, something that is hard to do in modern London. Tough problem.
I wonder if they can carry hundreds of opened barrels of ice on open-bed trains through the tunnels at night, go slowly and let them melt to water (but kept in the buckets, because you don't want to flood the tunnels)...
I would expect them to already have some kind of drainage system, so if the line has some connection to some line that goes outside, just pulling cargo trains full of ice down there and dumping them might work.
That said, a typical shitty single-hose monoblock air conditioner has 9000-12000 BTU/h of rated cooling capacity. 12000 BTU/h is also known as "one ton". Sometimes, stupid units can be helpful, because "one ton" of cooling is what you get if you dump one ton of ice (short ton, of course) per day in the place. So you'd need a lot of ice, many tons per station, to make a significant difference.
Either way, since this is such an obvious idea, and they had a competition to solicit solutions, I'm sure this was evaluated and discarded - although it would be interesting to read the official analysis of the idea and learn why it wouldn't work.
Where there’s space, this has already been done. Unfortunately for many lines there simply isn’t space.
Just about every abandoned station, elevator shaft, and maintenance tunnel on the network is already fitted out with huge fans where possible.
TfL also runs a semi-continuous works project that looks a custom and novel one-off cooling solutions that can be retrofitted into whatever space is left. Including complicated hydronic systems that pump around huge quantities of water where the infrastructure allows for it.
Some parts of the London underground use passive energy recovery by locating stations nearer to the surface than most of the tunnel between them. Trains start by rolling downhill and when they approach a station, uphill.
The trains in London can be up to 50 years old at this point. Where the technology was available during the building of the trains, you can generally expect regenerative breaking. But it’s far from universally available unfortunately.
> If the line is unreceptive, braking energy is dissipated in on-board resistors
How many watts are dumped into onboard heat-generating resistors on the trains in the most heat-affected lines per week?
Should regenerative braking be disabled in aboveground trains when heat impacts reach uncomfortable levels in belowground tunnels?
> Regenerated braking energy is transmitted to the London Underground high voltage distribution network
If regenerative braking oversupply is inducing higher temperatures belowground through on-train resistors, then only an operational change to aboveground mode would be required to minimize that induced heating during times of thermal need.
(Obviously longer-term solutions with non-zero capital expenditure exist that could be pursued in parallel.)
> Should regenerative braking be disabled in aboveground trains when heat impacts reach uncomfortable levels in belowground tunnels?
It’s not that simple. You can’t just treat the entire line as some kind of perfect conductor that allows to you move unlimited amounts of energy around. In reality there’s issues with both the conductive capabilities of the lines themselves, but there’s also the simple problem that train lines aren’t generally electrically connected end-to-end for a few reasons.
1. You don’t want trains pulling power down more of the line than necessary, when it’s more efficient to draw power from other parts of the high voltage grid.
2. You don’t want a single track fault to cause your entire line to be forced to disconnect completely.
3. You don’t want your line to accidentally become a power carrier for electrical grid, just because the two ends of your line a physically located far enough apart that they experience different grid conditions.
As a result most train lines are broken up into electrically isolated segments, each with its own distinct power supply. So you could turn of regen on overground trains, but unless they happen to be sharing a section of track with underground trains, it doesn’t create any additional capacity to dump breaking energy into.
Even with isolated segments, the measurements performed with Southern found 10% of regenerative power was turned into heat as the line voltage was already at max threshold from other trains; if that holds true today, then there’s still opportunity to consider optimizations for ensuring that 10% is weighted towards aboveground rather than below.
To me, 'disable abovegound regen' feels like not likely to solve the problem, just from a feeling that those systems are not that closely coupled. Otherwise, it seems easy to just keep on doing regen and set up (maybe not even need to: run a cable up to) aboveground dissipation grids.
I will guess that the limit is how much regen current can be passed back from the train into the supply system through the power supply rails / pickup shoes.
If I were making (confess, yes, untrained outsider) suggestions, I'd add water tanks to the trains, use the resistive braking to heat the water (not ambient air) during the trip, then change out the now-hot water for cold at the destination layover points. Not thinking this is a particularly creative solution, sounds like the "pull trains full of ice" already noted. Also this is off-the-cuff, so welcoming critiques!
Speculate: district level heating (wikipedia entry: https://en.wikipedia.org/wiki/District_heating) using heat pumps to draw out the tunnel heat; not sure if that is too complex altogether, maybe it would work as a longterm maintenance process but not as a 'fix the current problem' one...?
So if I have this right, TfL is constructing a giant thermal mass, and therefore is banking heat energy. If we (for example) piped cold water through this, we'd get warm water. So in winter, this could reduce heating bills substantially for people connected to such a system.
Isn't heat free energy in a place like London? I know very little about metro systems so please correct me if this is insane: wouldn't the people living above the tubes be happy to get a heat exchanger (passive) or heat pump (active, but takes more of the heat) that prewarms their hot water supply? People still take warm showers and boil tea and rice/pasta in summer, and in winter the purpose should be obvious. If the water comes in at 30 instead of 10 degrees C, you need to add only a few degrees for showers and floor heating
Heat is to energy as feces to food. It's not quite valueless by mass or by volume, but close enough that for most purposes the major issue is rejection.
A problem is the clay surrounding the tunnels insulates them - it traps heat because heat flows through it very slowly. So you drill down and put a heat exchanger pipe down there, you pump heat from 3cm of clay around the pipe and now no heat flows through the clay to your pipe even though there’s a lot of heat still down there.
Your pipe becomes a tiny worm of cold pipe in a big lump of hot clay and you’ve done very little to cool the underground or warm your water. That is, if heat moved easily through the stuff then the problem of heat buildup would be easy to solve but in that case heat wouldn't build up so there wouldn't be a problem; and vice-versa.
There is at least one on this line (north of Kings Cross) and one on the Northern line (north of Moorgate). It's for district heating or electricity generation.
>wouldn't the people living above the tubes be happy to get a heat exchanger (passive) or heat pump (active, but takes more of the heat) that prewarms their hot water supply
Ground source heat pumps are expensive to build, even more so in a dense area like London. So even if everything you said is true, I suspect the juice isn't worth the squeeze.
In this case, though, the excess heat is a major burden, so there is room to negotiate with a district thermal provider that pays that provider to absorb and redistribute the heat, as long as it's less than the cost to pump it out to the environment.
I'm not saying it's easy (it will likely be a bespoke solution). Given the organizations, I expect the difficulty to be as much business (setting the prices) and political (defending the prices set) as technical.
The entire issue is that the earth surrounding the tubes is acting as a giant buffer. Enough heat has been dumped into it over the years that it has permanently warmed up. Draw heat from it during the winter to warm up homes, and it'll be able to absorb more heat from the tunnel air during the summer.
And because it's permanently warmed up, the long term consequence is the line becomes a health hazard and has to be closed for increasingly long periods.
When wet bulb > body temp people start getting heat stroke, which leads to fainting and potentially death - a bad look for a public transport system.
The likely remedy is to install gigantic refrigeration units in the ventilation shafts and pump in cold air. This will be hugely expensive to build and run.
But the alternative is a tube line that can't be used. So there may not be much choice.
It won't be zero so spreading it across enough people might already solve it. If that still leads to insufficient demand during the hottest weeks, idk, it's energy, surely there's something useful you can do? Store it for next week, pre-heat water for the nearest steam engine (e.g. gas power plants are steam engines running on methane, so if they have to heat the water by fewer degrees.. The problem will be finding a steam engine close to the heat source), supply it to an industrial process that needs temperatures above ambient (egg breeding for vaccine production? Idk), create electricity from the temperature differential between this system and the Thames water using the Peltier effect
I've surely got a too naïve view of economics but if the goal were to not waste resources then there will be things you can do before dumping it into the hot summer air
Your are correct in principal, though implimenting your idea, now, is essentialy impossible as installing the plumbing after the fact might cost more than just starting over with a whole new line, and would in fact make things much worse durring the many years it takes to find out if the
added systems even work.
Given that there is only clay under London, it is by far better to start over and build a whole new line, and/or go all in on a mega high tech ,high pressure refrigeration systems for the human occupancy areas, and hope that there are no break downs in the "hot zones"
orrible mess
What if trains brought their heat with them instead of leaving it in the tunnels? I'm thinking some kind of large seal like thing in front of and behind trains that keeps the train surrounded by the same air. Stations serve as a spot to dump hot air and blow in cooler air. I guess the problem is it would take a lot of energy to push all that air around. Also the trains would be hotter.
Of a special tube train with blocks of ice. You’d need to have various pits dug in, and pumps to drain the water. Yes water and power electronics is “fraught”.
I just like the idea of trains trundling along, blocks of ice being carted out and gradually melting.
Another idea is to move mechs-bots via Underground in a post-apocalyptic scenario, but that’s not so relevant here.
Yep ... know people who commute on the Victoria and it doesn't sound fun. I've had to get it when my usual commute on the Northern line was impossible (only once, thankfully) and it was horrendous.
I dont quite understand what’s stopping them from just buying hundreds of chillers, putting them on the surface close to each station, and running chilled water loops down. Other than cost of course.
They're running trains. Trains use a lot of electricity, and they turn almost all of it into heat. You'd have to have as much chilling capacity as the current electricity demand of the entire tube line, which is quite a lot.
However, if the buildings above were to sink ground source heat pump loops into the warmed ground to heat the buildings in winter, this would basically be what you just suggested, and would be a win-win situation.
Huh? Modern modular air cooled chillers go up to 800 tons each and can remove multiple MW of heat load continuously pretty much 24/7.
500 of them could remove 1.4 GW of heat.
Of course there are many ways to improve efficiency, but even assuming the worst case it’s still technically feasible to remove many times more heat than the line generates.
And where is the energy to power all of them coming from?
GP is saying that you can approximate the energy going into the system by looking at the electricity consumption of the trains, as all then energy is eventually going to end up as heat.
A heat pump can have a CoP topping out at 5. So 1 unit of energy needed to move 5 units heat out. That means a “net zero” cooling system would consume a minimum of 20% as much energy as the trains themselves. Realistically it’s probably closer to a CoP of 3.5, so 28% more energy. For something like the underground that gonna be a 5-10% increase in there operational costs at a minimum. Where does the funding for all that come from? And that before we even look at the capital costs of heat pumps and various ancillary equipment needed to run them.
As a point of reference TfL underground trains have an average power consumption of 140MW continuous. Now only about 45% of the underground is actually underground, but that’s still 63MW in just the underground parts. At an optimistic CoP of 5, that means 12.6MW of additional energy needed to cool the tunnels using your approach.
Wholesale electricity prices in the UK are something like 7p per kWh. So over a year that’s an additional £17m of electricity, just for cooling.
> tunnel ventilation installations, chiller systems pumping chilled air into mid-tunnel shafts and regenerative braking to reduce heat generated by trains breaking
The hoops TfL jumps through just to not extend AC to the rolling stock in more lines are baffling. At least we finally got some AC in the new Piccadilly rolling stock.
You can redesign the signalling systems etc to work at even 40C, plenty of countries do it. You can't redesign humans to feel comfortable inside a stuffy carriage at 35C.
Sure, but that means the stations will also have 40C air. Can the humans handle that? And it's going to be 42C the next year, 44C the year after, and so on...
What do you do if some incident halts full trains (possibly depowering them but for things like emergency lighting) near the midpoints of longer sections of 40 degC deep tunnels?
You can survive a few hours at that temperature, so not an immediate catastrophe. You should be still able (though not comfortable) to walk to the next emergency exit or station.
Is there a reason why they can't drill a couple bowling ball sized holes at strategic intervals and put some high speed extraction fans in?
Stations entrances are open to outside so if you create enough negative pressure the hottest parts in the tunnels it'll pull in air. Do that long enough and presumably ambient & clay cools?
Presumably engineers dismissed this already, but why?
They have added ventilation to the tunnels, it's mentioned in the article. It's more than just a couple bowling sized holes, but apparently still not enough
Unfortunately, hydrating clay is extremely hard to do. Clay is what you use as a water-tight material in dams, artificial lakes, waste dumps and stuff like that, because water doesn't really pass through it.
I think people might object to TfL drilling a bowling ball sized tunnel in the middle of their house/garden/park/road/driveway/swimming pool/historic monument.
Remember the deep level network is some 23m down, and runs under buildings. At lot of it doesn’t follow roads, or have any kind of conveniently clear space on the surface above it.
> Temperatures hiked as high as 31.1[C] degrees in August 2024 [...]
So, I can imagine that this is a long-term problem, but it seems odd that the panic is setting in already, when some platforms in the NYC subway regularly exceed 40C / 104F every summer? This article seems in a similar genre to the breathless advice to remain inside in Britain when the outside temperature might get above 27C / 81F, otherwise known as a not-particularly-warm spring day in much of the US in most years.
> This article seems in a similar genre to the breathless advice to remain inside in Britain when the outside temperature might get above 27C / 81F, otherwise known as a not-particularly-warm spring day in much of the US in most years.
It’s really not breathless, because high temperatures and how to handle them is completely absent from the cultural baggage. I don’t live in the UK, but in a place which similarly does not have much in the way of high temperatures historically and low AC penetration, and during heat spikes I see a significant fraction of my neighbours with windows wide open at 4PM.
Habituation is also a significant factor. The UK does not get a smooth transition into higher normals, it gets heatwaves.
I live in the UK and a lot is down to the tabloid newspapers trying to get some sales with 'Horror Heatwave!' type headlines when it's 27C. Brits go on holiday to Spain, we are familiar with heat.
Statistically we know that humans who live somewhere that you'll just die in the regular environment due to climate behave very differently from humans who live in a temperate climate like the UK when the actual temperature warrants the same behaviour. If you live in Nunavut or the Iran / Pakistan border you already knew that you can just die from temperature extremes and so you need to ensure you stay at a survivable temperature, in Wales it's quite unexpected.
As a result you actually get many more deaths from extremes in countries where the usual climate is temperate like Britain, even when the actual temperatures aren't as extreme as in countries where that would be more common.
Surely that says more about how NYC than it does about London?
If I had to suffer overcrowded trains with standing room only, people’s armpits in my face and all, at 40C temperatures everyday in the summer, then I wouldn’t be laughing at London for trying to avoid the same fate. I’d be complaining that my own city isn’t taking their problems seriously enough.
I'm only in London occasionally but I can confirm that some lines are unbearably hot, in the summer I have no idea how people commute in that heat every day. And I'm originally from a much hotter country than the UK.
This problem is also an illustration of the potential of geological thermal energy storage.
The thermal time constant of a lump of matter scales as the square of its linear dimensions (for a given geometry). This can easily reach many years for large enough chunks of underground stuff. This is why geothermal energy works at all; the heat energy flowing up from the deep earth is stored for many thousands of years at reachable depths and can be mined. And, if one has excess energy, it could be reinjected underground as heat and later recovered.
"The average temperatures on the Victoria line have risen by almost seven degrees since 2013 – nearly a *30%* increase.
Conversely, the increase in the average annual temperatures across all Underground lines from 2013 to 2024 was merely *seven percent*, placing Victoria’s temperature rise vastly above that."
Using percentages to talk about changes in non-Kelvin temperatures is crazy.
Yep. That 30% is a bad use of statistics.
28 degrees Celsius is not 30% warmer than 21 degrees Celsius. This same stat rendered in Fahrenheit would say 70 degrees -> 82 degrees, or 17%. In kelvin it would be 294 -> 301, or 2.3%
Or we could invent a new measure indexed to Celsius but offset by 20 degrees, and declare a 1 -> 8 change, a whopping 700%.
Feynman was complaining about this error appearing in textbooks back in the sixties[0].
The trouble (of course) is that Celsius properly is not a proper unit, but a "scale", or a "unit of difference" (equal to kelvin), or even torsor[1].
The trouble with the kelvin here is that if you see the 7 kelvin increase as a proportion of the 295K starting temperature the you only get a 2% increase. Nobody is going to buy your newspaper if you're putting up weak numbers like that.
[0] https://mathematicalcrap.com/2024/03/05/the-feynman-story/ [1] https://math.ucr.edu/home/baez/torsors.html
To make matters worse, not all ranges and percentages on that scale are equal, whether they're the same in absolute or relative terms. Humans have a narrow relevant "operational" temperature band. Even 20 degrees between 10-30C feel like nothing compared to the 5 degrees between 37-42C.
Not to mention that wet bulb temperature, measuring the effect of humidity, is actually the most important measure in those temperature ranges.
Humidity in London is also awful as the temperature gets closer to freezing. I found the damp cold in London to be common over the year and truly horrid (a reason to never live there).
At home (Christchurch, NZ) we often get dry cold which can be pleasant: however when we do get the occasional vile damp cold I personally call it "London cold" because it made so much impression upon me in my 20s.
Your upper band of 30C is making this Englishman sweat just thinking about it. Which I think proves your point about narrow operational temperature even further.
You’re right in principle but that’s probably the worst example you could have given. So bad an example that I think it could easily be argued to disprove your point.
For us people not living in Arabia or South Texas the difference between 37 and 42 Celsius is indeed quite important. 37 feels pretty hot, but yet livable, while 42 (and even 40 for me) means that nothing non-urgent should bring me out of the house.
And, inversely, the five degree drop from, say, 3C to -2C represents means water can and will freeze, which is another massive change in livability.
Indeed. At 3C in London, the humidity seeps into every pore and settles into your bones. Riding a bike at 3C, unless you're wearing a balaclava and a ski mask, is an exercise in pure pain, as the wetness sublimating off your face has approximately the same effect on your facial nerves as being flayed.
Ok the other hand, -2C in London is crisp and invigorating and entirely preferable in every possible way.
There are few or no human scale situations where percentages of absolute temperature are meaningful, absolute zero is too far away and we live in a too narrow range of temperatures. Unless you're in a scientific context just don't use percentages on absolute temperature, only on rates.
Then just don't use percentages, and rely on people realizing that a 7 degree difference is big!
It would definitely be crazy in Fahrenheit, but in centigrade I think it makes some sort of intuitive (if not scientific) sense. (Together with the sea-level assumption we always make in casual temperature discussion anyway.)
It makes just as much intuitive sense in Fahrenheit as it does in centigrade.
Reading this quote made me finally realize why the name centigrade exists. It’s a gradient scale of 100.
Reading this comment about the previous quote made me finally realize why the name centigrade exists.
Maybe because I was brought up with centigrade it makes more sense to me. The centigrade number is how far you are from water freezing. If it goes up 100% then you are twice as far away. I'm not aware that doubling the fahrenheit number has a similar easy to understand meaning?
> The centigrade number is how far you are from water freezing
The Fahrenheit scale is how far your are from your own body temperature. It was designed that 100 is the temperature of a human. (Adjusted later to 98.6 due to inaccuracies.)
0 was designed to be as cold as you can get with ice and salt (also ended up being slightly inaccurate).
> Maybe because I was brought up with centigrade it makes more sense to me.
Yup. People brought up on Fahrenheit think it is superior. For temperature neither argument is objectively better. (In contrast to imperial distance measurement with non-powers of 10 and factions, where there are good arguments against it, with temperature both scales are ultimately arbitrary.)
Why? The slope of the Fahrenheit scale is different to the Celsius and Kelvin scales, but the slope of the latter two does match.
The slope of the scales has no bearing on whether percentages are meaningful here. The problem with both systems when it comes to percentages is that neither system has 0 set to a natural 0. This leads to an entirely arbitrary point on the scale where decreases in the unit will approach a 100% difference and then suddenly start decreasing again.
If anything Fahrenheit should be less insane because at least the artificial 0 is likely to stay much further away in the data they're quantifying so the percentages stay reasonable.
Ah right, okay, that makes sense.
The slope of the Fahrenheit scale matches that of the Rankine scale.
I would still say that the in the Rankine scale percentage increases make sense, and Fahrenheit changes to not.
The thing that matters isn't the slope, but the zero point; "X% farther from absolute zero" is a useful measurement, "X% farther from an arbitrary zero point" is not. Especially when negative or zero temperatures are involved.
Ok. Then please explain what % does the temperature rise when going from 0 Celsius to 5 Celsius!
Or -1 to 1 Celsius, for that matter.
Obviously it's -200%, which means that going from -1C to 1C is a drastic decrease in warmness!
Early measurements were done by individuals and they were idiosyncratic to the process of discovery/calibration.
Kelvin is refined measurements used to relate to a wider scale of temperatures. Celsius is a metric human scale subset of Kelvin.
In both it makes a sort of intuitive sense. 7% of the way from freezing to boiling is a meaningful way to visualise temperature; 7% of the way from ice melting in a bath of salt to slightly above Mrs Fahrenheit's armpit temperature is also meaningful, although perhaps a little idiosyncratic.
Edit: this comment was deeply stupid for obvious reasons and I regret trying to interact with other people when I should be asleep.
The issue is a percentage of a Celsius value is not that. For example, an increase from 1°C to 2°C is a "100% increase", but is only 1 percentage point from freezing to boiling.
You could say things like that with anything in percentages? 100% increase in your pension from 100k to 200k is only 10% (increase, to 20% total) of your target 1M, or whatever.
But in your example, the 10% has nothing at all to do with the increase of 100%.
If your ”whatever” target instead was 50k, is the argument that going from 100k to 200k would be 400%?
Yikes. I posted this, and I missed that, something I realised soon into my first year physics degree lab. I learnt more than just dipping calculators in liquid nitrogen for fun.
I apologise.
And they manage to make it even more crazy by also comparing it to average external temperatures.
== The Victoria Line average temperature in August last year was 60% higher in temperature than the average external temperature that month, measured at 19.5 degrees. ==
Certainly for January it must have been hundreds of percent higher.
And what would the numbers be for e.g., the Moscow metro in winter months where the average outside temperature is negative?
I don’t know if I’m worried about it. While the measurement makes little scientific sense it makes intuitive sense, and, importantly, the intuitive implications are the scientific implications.
It’s a huge increase, if not for the reasons they describe.
So how many decibels louder is it now?
Is it? I think it puts the Victoria rise in perspective to the other lines quite effectively.
Everyone knows where the zero is in Celsius using countries anyway and days in the negative are so rare in the UK you can discount them (plus they are none inside the tube).
I logged in just to give this an upvote :-)
> Historically, the Underground infrastructure offered a respite from warm weather, indicated in Austin Cooper’s ‘It is cooler below’ poster, issued in 1924 by the Underground group to promote a more comfortable experience of travel during warm weather.
A century of burrowing commuter-worms unfortunately managed to bake all the beautiful wet clay that kept the tunnels tolerable when the sun was shining about.
It seems straightforward to me that it would be enough to rehydrate the ground. Just need (approximately),
Sounds like a lot but it's only about 1/300th of the yearly flow of the Thames.I don’t think the hydration of the clay is the important element here. Rather I suspect it’s simple just the sheer mass of clay, wet or otherwise, that’s involved.
There’s a reason why ground source heat pumps work so well. It’s because the ground is such a fantastically huge heat sink/source that in most scenarios we consider it capable of sinking or sourcing a practically unlimited amount of heat.
Unfortunately one of the scenarios where this breaks down, is when you stick a bunch of tunnels in the ground, then pump a crap ton of energy into those tunnels years round, and expect the ground to sink all the heat away. Turns out, if you do that, the ground itself starts heating up, and given that clay is a reasonable good insulator, it’s like wrapping all those tunnels in wool jumpers.
I would point out as well that all these tunnels are “deep level” tunnels running at an average depth of 24 meters and getting as low as 67 meters. The heat of the sun on the ground surface will have approximately zero impact on the tunnel temperatures. 24 meters of clay is a lot of insulation to work with.
At a couple of stations a river passes by and that is used to cool the station.
I think Oxford Circus is one.
<man walks into sauna room> Ooh, it's a bit hot in here! I better throw some water on these rocks to cool them down.
Joking aside, I actually don't know how dry it is in the underground, and therefore whether adding water for evaporative cooling would work. I would have assumed it was quite humid, but maybe not?
It seems implausible to me that the clay is dehydrated. The Victoria line was only built in the 60s and has a waterproof lining. (It's also built with asbestos cement, unfortunately, which is no doubt a problem when they need to cut it for whatever reason)
Have you thought of suggesting this to TfL? There has to be something here.
Unfortunately, hydrating clay is extremely hard to do. Clay is what you use as a water-tight material in dams, artificial lakes, waste dumps and stuff like that, because water doesn't really pass through it.
Yes, people whose day job is to explore all possible options have surely missed this extremely obvious idea.
Alright smart arse.
Looking at the temperature chart and the significant drop in 2020 during the pandemic, the source is certainly the trains and people themselves. (fewer trains moving, less heat added back then). At this point I expect the infrastructure is heat soaked and will need a prolonged period of cooling to bring temps down. i.e. don't expect instant results.
Moving more air through the tunnels, adding A/C systems - both have a problem of needing room up on the surface for blowers and compressors, something that is hard to do in modern London. Tough problem.
I wonder if they can carry hundreds of opened barrels of ice on open-bed trains through the tunnels at night, go slowly and let them melt to water (but kept in the buckets, because you don't want to flood the tunnels)...
I would expect them to already have some kind of drainage system, so if the line has some connection to some line that goes outside, just pulling cargo trains full of ice down there and dumping them might work.
That said, a typical shitty single-hose monoblock air conditioner has 9000-12000 BTU/h of rated cooling capacity. 12000 BTU/h is also known as "one ton". Sometimes, stupid units can be helpful, because "one ton" of cooling is what you get if you dump one ton of ice (short ton, of course) per day in the place. So you'd need a lot of ice, many tons per station, to make a significant difference.
Either way, since this is such an obvious idea, and they had a competition to solicit solutions, I'm sure this was evaluated and discarded - although it would be interesting to read the official analysis of the idea and learn why it wouldn't work.
Ice blocks were trialed in the past. https://en.wikipedia.org/wiki/London_Underground_cooling#cit...
They could flood the tunnels with an appropriate amount of liquefied air.
Big fans to pull surface air down into the tubes when the tubes are warmer than surface ambient ? Cool the tunnels, warm the surface.
Where there’s space, this has already been done. Unfortunately for many lines there simply isn’t space.
Just about every abandoned station, elevator shaft, and maintenance tunnel on the network is already fitted out with huge fans where possible.
TfL also runs a semi-continuous works project that looks a custom and novel one-off cooling solutions that can be retrofitted into whatever space is left. Including complicated hydronic systems that pump around huge quantities of water where the infrastructure allows for it.
This. Brake friction pumps heat into the ground at a higher rate than it could dissipate away.
Aren't they using regenerative braking?
Some parts of the London underground use passive energy recovery by locating stations nearer to the surface than most of the tunnel between them. Trains start by rolling downhill and when they approach a station, uphill.
The trains in London can be up to 50 years old at this point. Where the technology was available during the building of the trains, you can generally expect regenerative breaking. But it’s far from universally available unfortunately.
Yes.
https://tfl.gov.uk/corporate/transparency/freedom-of-informa...
> If the line is unreceptive, braking energy is dissipated in on-board resistors
How many watts are dumped into onboard heat-generating resistors on the trains in the most heat-affected lines per week?
Should regenerative braking be disabled in aboveground trains when heat impacts reach uncomfortable levels in belowground tunnels?
> Regenerated braking energy is transmitted to the London Underground high voltage distribution network
If regenerative braking oversupply is inducing higher temperatures belowground through on-train resistors, then only an operational change to aboveground mode would be required to minimize that induced heating during times of thermal need.
(Obviously longer-term solutions with non-zero capital expenditure exist that could be pursued in parallel.)
> Should regenerative braking be disabled in aboveground trains when heat impacts reach uncomfortable levels in belowground tunnels?
It’s not that simple. You can’t just treat the entire line as some kind of perfect conductor that allows to you move unlimited amounts of energy around. In reality there’s issues with both the conductive capabilities of the lines themselves, but there’s also the simple problem that train lines aren’t generally electrically connected end-to-end for a few reasons.
1. You don’t want trains pulling power down more of the line than necessary, when it’s more efficient to draw power from other parts of the high voltage grid.
2. You don’t want a single track fault to cause your entire line to be forced to disconnect completely.
3. You don’t want your line to accidentally become a power carrier for electrical grid, just because the two ends of your line a physically located far enough apart that they experience different grid conditions.
As a result most train lines are broken up into electrically isolated segments, each with its own distinct power supply. So you could turn of regen on overground trains, but unless they happen to be sharing a section of track with underground trains, it doesn’t create any additional capacity to dump breaking energy into.
Even with isolated segments, the measurements performed with Southern found 10% of regenerative power was turned into heat as the line voltage was already at max threshold from other trains; if that holds true today, then there’s still opportunity to consider optimizations for ensuring that 10% is weighted towards aboveground rather than below.
https://railknowledgebank.com/Presto/content/GetDoc.axd?ctID...
Also:
> A super capacitor is being used in a substation by Docklands Light Rail in London, UK
So at least they were considering what to do about this fifteen years ago. I wonder if they've made progress?
Why don't they use batteries to buffer between consumption / regen and the upstream power?
To me, 'disable abovegound regen' feels like not likely to solve the problem, just from a feeling that those systems are not that closely coupled. Otherwise, it seems easy to just keep on doing regen and set up (maybe not even need to: run a cable up to) aboveground dissipation grids.
I will guess that the limit is how much regen current can be passed back from the train into the supply system through the power supply rails / pickup shoes.
If I were making (confess, yes, untrained outsider) suggestions, I'd add water tanks to the trains, use the resistive braking to heat the water (not ambient air) during the trip, then change out the now-hot water for cold at the destination layover points. Not thinking this is a particularly creative solution, sounds like the "pull trains full of ice" already noted. Also this is off-the-cuff, so welcoming critiques!
Speculate: district level heating (wikipedia entry: https://en.wikipedia.org/wiki/District_heating) using heat pumps to draw out the tunnel heat; not sure if that is too complex altogether, maybe it would work as a longterm maintenance process but not as a 'fix the current problem' one...?
Believe regenerative breaking is used to supplement Oxford Circus’ electricity supply
So if I have this right, TfL is constructing a giant thermal mass, and therefore is banking heat energy. If we (for example) piped cold water through this, we'd get warm water. So in winter, this could reduce heating bills substantially for people connected to such a system.
Is TfL not monetising this thermal mass? Why not?
Steam heat at 30°? In London? Can't imagine...
30 degree water isn’t warm enough for direct residential heating but with a geothermal system it’d be great.
Isn't heat free energy in a place like London? I know very little about metro systems so please correct me if this is insane: wouldn't the people living above the tubes be happy to get a heat exchanger (passive) or heat pump (active, but takes more of the heat) that prewarms their hot water supply? People still take warm showers and boil tea and rice/pasta in summer, and in winter the purpose should be obvious. If the water comes in at 30 instead of 10 degrees C, you need to add only a few degrees for showers and floor heating
Heat is to energy as feces to food. It's not quite valueless by mass or by volume, but close enough that for most purposes the major issue is rejection.
A problem is the clay surrounding the tunnels insulates them - it traps heat because heat flows through it very slowly. So you drill down and put a heat exchanger pipe down there, you pump heat from 3cm of clay around the pipe and now no heat flows through the clay to your pipe even though there’s a lot of heat still down there.
Your pipe becomes a tiny worm of cold pipe in a big lump of hot clay and you’ve done very little to cool the underground or warm your water. That is, if heat moved easily through the stuff then the problem of heat buildup would be easy to solve but in that case heat wouldn't build up so there wouldn't be a problem; and vice-versa.
[dead]
The problem isn’t so much finding uses for the heat, it’s getting the heat out of the tunnels to begin with.
These are some of the deepest tunnels going under some of the most built up parts of the UK.
I wonder if an extremely tall subterranean windcatcher [0] with its bottom at the top of a tunnel could passively cool the tunnel.
[0] https://en.wikipedia.org/wiki/Windcatcher
These basically already exist around the network. But that simply isn’t even close to moving enough energy to make a difference.
There is at least one on this line (north of Kings Cross) and one on the Northern line (north of Moorgate). It's for district heating or electricity generation.
>wouldn't the people living above the tubes be happy to get a heat exchanger (passive) or heat pump (active, but takes more of the heat) that prewarms their hot water supply
Ground source heat pumps are expensive to build, even more so in a dense area like London. So even if everything you said is true, I suspect the juice isn't worth the squeeze.
I think you are correct.
In this case, though, the excess heat is a major burden, so there is room to negotiate with a district thermal provider that pays that provider to absorb and redistribute the heat, as long as it's less than the cost to pump it out to the environment.
I'm not saying it's easy (it will likely be a bespoke solution). Given the organizations, I expect the difficulty to be as much business (setting the prices) and political (defending the prices set) as technical.
What do you do in the summer when the homes don’t want the heat?
That doesn't have to be a problem in practice.
The entire issue is that the earth surrounding the tubes is acting as a giant buffer. Enough heat has been dumped into it over the years that it has permanently warmed up. Draw heat from it during the winter to warm up homes, and it'll be able to absorb more heat from the tunnel air during the summer.
And because it's permanently warmed up, the long term consequence is the line becomes a health hazard and has to be closed for increasingly long periods.
When wet bulb > body temp people start getting heat stroke, which leads to fainting and potentially death - a bad look for a public transport system.
The likely remedy is to install gigantic refrigeration units in the ventilation shafts and pump in cold air. This will be hugely expensive to build and run.
But the alternative is a tube line that can't be used. So there may not be much choice.
It won't be zero so spreading it across enough people might already solve it. If that still leads to insufficient demand during the hottest weeks, idk, it's energy, surely there's something useful you can do? Store it for next week, pre-heat water for the nearest steam engine (e.g. gas power plants are steam engines running on methane, so if they have to heat the water by fewer degrees.. The problem will be finding a steam engine close to the heat source), supply it to an industrial process that needs temperatures above ambient (egg breeding for vaccine production? Idk), create electricity from the temperature differential between this system and the Thames water using the Peltier effect
I've surely got a too naïve view of economics but if the goal were to not waste resources then there will be things you can do before dumping it into the hot summer air
People still take hot showers and use hot water
Your are correct in principal, though implimenting your idea, now, is essentialy impossible as installing the plumbing after the fact might cost more than just starting over with a whole new line, and would in fact make things much worse durring the many years it takes to find out if the added systems even work. Given that there is only clay under London, it is by far better to start over and build a whole new line, and/or go all in on a mega high tech ,high pressure refrigeration systems for the human occupancy areas, and hope that there are no break downs in the "hot zones" orrible mess
What if trains brought their heat with them instead of leaving it in the tunnels? I'm thinking some kind of large seal like thing in front of and behind trains that keeps the train surrounded by the same air. Stations serve as a spot to dump hot air and blow in cooler air. I guess the problem is it would take a lot of energy to push all that air around. Also the trains would be hotter.
Also you'd blow everyone off the platform, up the escalator, and a hundred feet in the air at each station stop.
At what point does it become illegally warm?
I thought 30°C was the limit for office work in the UK.
I recall when there was a terrorist bombing for the Stratford Olympics that emergency service people had to work in a tunnel at 60°C.
I avoided the deep tube for several years after that.
In case you also couldn’t guess the “f” in TfL, it’s Transport for London.
https://tfl.gov.uk/
https://en.wikipedia.org/wiki/Transport_for_London
You can blame Blair, I think, for the fashion of putting “for” into the names of administrative organisations.
In case you missed the 4 places it's made explicit in the graphs, or 'London' in the URL.
I had an idea, perhaps a weird fantasy.
Of a special tube train with blocks of ice. You’d need to have various pits dug in, and pumps to drain the water. Yes water and power electronics is “fraught”.
I just like the idea of trains trundling along, blocks of ice being carted out and gradually melting.
Another idea is to move mechs-bots via Underground in a post-apocalyptic scenario, but that’s not so relevant here.
This was actually tried: https://www.theguardian.com/uk/2007/jun/05/transport.world
This would also increase the humidity to swamp-like levels.
Not if it was kept separate a metal box with fins could absorb the heat without leaking any humidity.
Besides at that temperature, more water can be absorbed in the air, so not just latent heat of melting, but heat absorbed in evaporation too.
Of course that would have to be wafted out, and not pumped were it just water.
Yep ... know people who commute on the Victoria and it doesn't sound fun. I've had to get it when my usual commute on the Northern line was impossible (only once, thankfully) and it was horrendous.
And the Northern line is no picnic either.
This is a generational buildup of heat, being tackled seasonally.
TfL must run its cooling operations in the winter as well as the summer.
It’s about net energy difference over the whole year.
Finding cold air in the winter will also be substantially cheaper
I dont quite understand what’s stopping them from just buying hundreds of chillers, putting them on the surface close to each station, and running chilled water loops down. Other than cost of course.
They're running trains. Trains use a lot of electricity, and they turn almost all of it into heat. You'd have to have as much chilling capacity as the current electricity demand of the entire tube line, which is quite a lot.
However, if the buildings above were to sink ground source heat pump loops into the warmed ground to heat the buildings in winter, this would basically be what you just suggested, and would be a win-win situation.
Huh? Modern modular air cooled chillers go up to 800 tons each and can remove multiple MW of heat load continuously pretty much 24/7.
500 of them could remove 1.4 GW of heat.
Of course there are many ways to improve efficiency, but even assuming the worst case it’s still technically feasible to remove many times more heat than the line generates.
And where is the energy to power all of them coming from?
GP is saying that you can approximate the energy going into the system by looking at the electricity consumption of the trains, as all then energy is eventually going to end up as heat.
A heat pump can have a CoP topping out at 5. So 1 unit of energy needed to move 5 units heat out. That means a “net zero” cooling system would consume a minimum of 20% as much energy as the trains themselves. Realistically it’s probably closer to a CoP of 3.5, so 28% more energy. For something like the underground that gonna be a 5-10% increase in there operational costs at a minimum. Where does the funding for all that come from? And that before we even look at the capital costs of heat pumps and various ancillary equipment needed to run them.
As a point of reference TfL underground trains have an average power consumption of 140MW continuous. Now only about 45% of the underground is actually underground, but that’s still 63MW in just the underground parts. At an optimistic CoP of 5, that means 12.6MW of additional energy needed to cool the tunnels using your approach.
Wholesale electricity prices in the UK are something like 7p per kWh. So over a year that’s an additional £17m of electricity, just for cooling.
£17 million doesn't sound that unreasonable for climate control for a system as large as London's
> tunnel ventilation installations, chiller systems pumping chilled air into mid-tunnel shafts and regenerative braking to reduce heat generated by trains breaking
The hoops TfL jumps through just to not extend AC to the rolling stock in more lines are baffling. At least we finally got some AC in the new Piccadilly rolling stock.
AC will only make the problem worse in the long term. Picadilly got AC because it has above-ground sections.
You can redesign the signalling systems etc to work at even 40C, plenty of countries do it. You can't redesign humans to feel comfortable inside a stuffy carriage at 35C.
Sure, but that means the stations will also have 40C air. Can the humans handle that? And it's going to be 42C the next year, 44C the year after, and so on...
What do you do if some incident halts full trains (possibly depowering them but for things like emergency lighting) near the midpoints of longer sections of 40 degC deep tunnels?
You can survive a few hours at that temperature, so not an immediate catastrophe. You should be still able (though not comfortable) to walk to the next emergency exit or station.
how many times has this scenario happened in last 20 years?
Is there a reason why they can't drill a couple bowling ball sized holes at strategic intervals and put some high speed extraction fans in?
Stations entrances are open to outside so if you create enough negative pressure the hottest parts in the tunnels it'll pull in air. Do that long enough and presumably ambient & clay cools?
Presumably engineers dismissed this already, but why?
They have added ventilation to the tunnels, it's mentioned in the article. It's more than just a couple bowling sized holes, but apparently still not enough
Unfortunately, hydrating clay is extremely hard to do. Clay is what you use as a water-tight material in dams, artificial lakes, waste dumps and stuff like that, because water doesn't really pass through it.
I think you replied to the wrong comment?
Yes, sorry.
I think people might object to TfL drilling a bowling ball sized tunnel in the middle of their house/garden/park/road/driveway/swimming pool/historic monument.
Remember the deep level network is some 23m down, and runs under buildings. At lot of it doesn’t follow roads, or have any kind of conveniently clear space on the surface above it.
> Temperatures hiked as high as 31.1[C] degrees in August 2024 [...]
So, I can imagine that this is a long-term problem, but it seems odd that the panic is setting in already, when some platforms in the NYC subway regularly exceed 40C / 104F every summer? This article seems in a similar genre to the breathless advice to remain inside in Britain when the outside temperature might get above 27C / 81F, otherwise known as a not-particularly-warm spring day in much of the US in most years.
> This article seems in a similar genre to the breathless advice to remain inside in Britain when the outside temperature might get above 27C / 81F, otherwise known as a not-particularly-warm spring day in much of the US in most years.
It’s really not breathless, because high temperatures and how to handle them is completely absent from the cultural baggage. I don’t live in the UK, but in a place which similarly does not have much in the way of high temperatures historically and low AC penetration, and during heat spikes I see a significant fraction of my neighbours with windows wide open at 4PM.
Habituation is also a significant factor. The UK does not get a smooth transition into higher normals, it gets heatwaves.
I live in the UK and a lot is down to the tabloid newspapers trying to get some sales with 'Horror Heatwave!' type headlines when it's 27C. Brits go on holiday to Spain, we are familiar with heat.
Statistically we know that humans who live somewhere that you'll just die in the regular environment due to climate behave very differently from humans who live in a temperate climate like the UK when the actual temperature warrants the same behaviour. If you live in Nunavut or the Iran / Pakistan border you already knew that you can just die from temperature extremes and so you need to ensure you stay at a survivable temperature, in Wales it's quite unexpected.
As a result you actually get many more deaths from extremes in countries where the usual climate is temperate like Britain, even when the actual temperatures aren't as extreme as in countries where that would be more common.
Surely that says more about how NYC than it does about London?
If I had to suffer overcrowded trains with standing room only, people’s armpits in my face and all, at 40C temperatures everyday in the summer, then I wouldn’t be laughing at London for trying to avoid the same fate. I’d be complaining that my own city isn’t taking their problems seriously enough.
NYC Subway trains have AC. They feel like refrigerators in the summer. Platforms get hot but can be avoided if you time carefully.
London Tube trains largely do not have AC, so heat in the tunnels is a big problem.
I'm only in London occasionally but I can confirm that some lines are unbearably hot, in the summer I have no idea how people commute in that heat every day. And I'm originally from a much hotter country than the UK.
I commute on the northern line 3 times a week ... it's not fun, but it's bearable ... just.
The trick is, if the window at the end of the carriage isn't open, make a beeline and open it, as the air moving past does help keep you cooler.
Losing the battle or not even trying to fight? It's
This problem is also an illustration of the potential of geological thermal energy storage.
The thermal time constant of a lump of matter scales as the square of its linear dimensions (for a given geometry). This can easily reach many years for large enough chunks of underground stuff. This is why geothermal energy works at all; the heat energy flowing up from the deep earth is stored for many thousands of years at reachable depths and can be mined. And, if one has excess energy, it could be reinjected underground as heat and later recovered.
Using the London subway is an adventure.
https://www.bbc.com/news/articles/cy9xxlky2pno (2024)
> Phone signal goes live on 25% of underground Tube
[dead]
[dead]