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%.
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
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.
The only upside is that your lips don’t split in winter.
From your comment I asked my brother and he said he agreed - something like he didn't like the Auckland 14° days that felt like 5°
Ok the other hand, -2C in London is crisp and invigorating and entirely preferable in every possible way.
Difference between 10 and 30 degrees C feels, way, way bigger than 37 to 42.
One goes from straight up cold to quite hot, while the other just goes from very hot to even more very hot.
At 42 degrees your body can’t cool down and this causes a lot of deaths or even the “casual” fainting described in the article due to hyperthermia. This goes way beyond your subjective feeling.
I thought this thread was discussing the subjective feelings of temperature.
Talking about relative temperature differences without anchoring to an absolute reference is meaningless. Using percentages is even worse.
It just takes a long time for your body temperature to increase, thus you have a while to find a cooler spot.
Celsius is more logical:
(1) the endpoints of Celsius are boiling/melting point of water (at standard atmospheric pressure). The lower endpoint of Fahrenheit is the lowest temperature Fahrenheit could achieve using a mixture of water, ice and ammonium chloride-using the freezing point of pure water is more logical than using the freezing point of an ammonium chloride solution-water is fundamental to all known life, ammonium chloride solutions don’t have the same significance (and why ammonium chloride instead of sodium chloride or potassium chloride? of the salts readily available to Fahrenheit, the ammonium chloride solution had the lowest freezing point)
(2) Fahrenheit initially put 90 degrees between his two “endpoints” (ammonium chloride solution freezing point and human body temperature), then he increased it to 96. Celsius having 100 degrees between its endpoints is more logical than 90 or 96
(3) while for both Celsius and Fahrenheit, there is error in the definition of their endpoints (the nominal values are different from the real values, because our ability to measure these things accurately was less developed when each scale was originally devised, and some unintentional error crept in)-the magnitude of that error is smaller for Celsius than for Fahrenheit
(4) nowadays, all temperature units are officially defined in terms of Kelvin - and Celsius has a simpler relation to Kelvin than Fahrenheit (purely additive versus requiring both addition and multiplication)
(5) Celsius is the global standard for everyday (non-scientific) applications, not Fahrenheit, and it is more logical to use the global standard than a rarely used alternative whose advantages are highly debatable at best
No, it is not. Americans say this only because they're used to it. The common arguments are that is that it is more precise, and 'you see temperatures from zero to one hundred degrees Fahrenheit throughout the year'.
Firstly, the problem with Fahrenheit is that its realisation is inaccurate by modern standards—which is why every single non-SI unit is now just an exact multiple of a corresponding SI unit with the same dimensions; the mediaeval and early modern definitions having been entirely forgotten. A bowl of salted ice and his own armpit? Truly an 18th-century invention.
Next, the extra precision that a difference of one degree Fahrenheit gives you is frankly useless. Within a single room one can experience a difference of over five degrees Celsius or more, depending on what's in the room—a radiator or air conditioner running, or the gas stove in a kitchen, or a high-end PC. Forget rooms. On the human body itself there can be a two to three degree Celsius difference between the extremities and the thorax/torso/head. Any field that requires extreme precision will naturally end up using SI units, so kelvin (or some related scientific unit). (Excluding the absolutely crazy bunch of American machinists who like using thousandths and ten-thousandths of an inch—at this point the joke writes itself).
As for climates, there are places that see very little difference in temperature, and definitely not the 'nice 0 – 100' range that Americans claim. Even in the US there are places like southern Louisiana and Florida that have borderline tropical climates, and don't really go below ~15 °C or above 35 °C.
All of this is not really logical either, and all end up being a manifestation of familiarity.
I’ve grown up with Celsius and never felt the need to use decimals in day to day weather discussion… Many air conditioners let you go up by half a degree C and that’s more than enough precision, more than I’ve ever felt was necessary in everyday conversation.
Again, not saying F is great, just that that one minor advantage is in fact real.
Countries that use Imperial for day to day use still do tend to use metric for a lot of purposes including many engineering tasks. (Imperial is terrible for certain types of engineering calculations--especially involving pounds and lets not get into slugs--but it's fine for cooking even if I tend to use grams for weight on my scale when baking.)
"Imperial countries" are actually pretty hybrid for the most part to greater or lesser degrees. UK is more SI than the US but they still commonly use a lot of Imperial units including some "odd" stuff like stones.
Informal measurement of humans and beer is a nice quirk of the UK system, but in my experience it's not commonplace to use imperial units for anything where accuracy is important (except maybe jewellers, and arguably road speeds/distances).
See also, the monstrosity that is AWG: https://en.wikipedia.org/wiki/American_wire_gauge
That's not really the point.
0° F: It's cold outside. 100° F: It's hot outside.
0° C: It's cold outside but not really that cold. 100° C: Dead.
0 K: Dead. 100 K: Dead.
These things are the case for humans regardless of whether you live in a place that actually gets cold or hot outside.
Like people tell me that the US customary system is “more human scale and intuitive” but I literally cannot picture, say, 15 inches or ten feet - it just means nothing to me unless I mentally convert to centimetres or meters.
So much of these arguments boil down to “I grew up with this system so I can intuitively use it, so it must be superior”
This is essentially every American argument for USC or Imperial units. In fact, there are actually legitimate reasons why some legacy units are superior—for instance the duodecimal or sexagesimal systems which have many more factors than the decimal. But every other argument is a variation of 'it's better because I know it better'.
300K: beach weather.
350K: you're distilling your own moonshine right ?
(worksforme)
Home distilling is great fun, and sometimes it's even legal, but please have an accurate thermometer and try not to poison yourself and others unless absolutely necessary.
(These temperate levels are also humidity and altitide/pressure dependent, if your still is in the high Appalachies then just listen to your heart.)
Only highlighting that one can "humanly relate" to Kelvin-based temperatures. If one so wishes. And that "reference points" there needn't be any more "arbitrary" than for °F/°C.
> These things are the case for humans
Who says so?
0 °C is very cold by many people's standards. About half the human population lives within the tropics. In fact I'd like to see Americans walk around in the UK wearing just a T-shirt and bermudas when it's barely above freezing, and insist 'it's not really that cold, it's only 32 °F'.
The point is that F degrees seems a pretty human scale that doesn't usually need a lot of decimals or minus signs for routine purposes. That it doesn't correspond to a couple of water transitions at standard pressure/temperature is sort of irrelevant. Of course, I and many other people are perfectly happy with using Celsius/Kelvin degrees for various purposes.
When winter is coming, if it's 3 deg C outside, I typically don't need to worry about ice. If it's -3 deg C outside, I need to worry about ice.
When winter is waning, if it's been icy and it's -3 deg C outside, I typically don't need to worry about water on top of the ice. If it's 3 deg C outside, I typically do need to worry about water on top of the ice making it super slippery.
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.)
I think Celsius is objectively better in that:
(1) its endpoints–freezing and boiling point of water–are more natural / less arbitrary / more fundamental than Fahrenheit's–coldest temperature you can reach with salt and ice to average human body temperature. Water is a fundamental substance to all known life; the freezing point of pure water is much more fundamental than the freezing point of a water + NaCl mixture (actually apparently Fahrenheit used ammonium chloride not sodium chloride, which is arguably even more arbitrary than sodium chloride would be). If you imagine some extraterrestrial civilisation independently invents a temperature scale, they'd be more likely to come up with something close to Celsius than something close to Fahrenheit
(2) while both scales contain some error in that the nominal value of their endpoints differs from the real value, the error is greater for Fahrenheit
(3) According to Wikipedia, Fahrenheit didn't have 100 degrees between his two endpoints, he originally had 90 then increased it to 96 – given base 10 is the standard number base used by humans, 100 divisions is less arbitrary than 90 or 96
(4) nowadays, all other temperature scales are officially defined in terms of Kelvin – and Celsius has a simpler relationship to Kelvin than Fahrenheit does (for Celsius it is purely an additive offset, for Fahrenheit it involves both addition and multiplication)
(5) conforming to the global standard is objectively better than sticking with an alternative which lacks clearcut advantges
They're natural, sure, but not really natural in a way that directly affects the most common everyday use case for temperature: the weather.
Fahrenheit's 0-100 is for now approximately the range of "normal" weather for the continental US, which is a useful if accidental property for Fahrenheit as a weather temperature system. Celsius's use of water's boiling point as a value for 100 is a nice property from an aesthetic perspective but means that it doesn't use the full 100 degrees when representing any earth-based climate.
> (2) ... (3)
Both of these aren't really advantages if you treat the scales as arbitrary, which in either case you are for most real-world uses of either scale. Water's boiling point at sea level is totally irrelevant when you're measuring the temperature of the outdoor air, a human body, or a steak.
> (4)
Only matters if you're actually doing work that needs to translate to and from Kelvin, which most people will never do in their entire lives.
> (5)
Standardizing would be helpful for sure, but it's not obvious that it would be worth the headache of making the switch given that the only real advantage to Celsius for most use cases is the mere fact that it's a standard.
Only if you live in the continental US - and even the continental US has parts where that generalisation doesn’t hold true. From a global perspective, there’s nothing special weather-wise about 0 Fahrenheit or 100 Fahrenheit-where I live, it has literally never been that cold (our record daily minimum is positive even in Celsius), while days of 38 Celsius or above are infrequent but far from exceptional. As a global standard, Fahrenheit has no meteorological advantage over Celsius - and indeed, Celsius is the global standard for meteorology, used by >95% of the planet
> Standardizing would be helpful for sure, but it's not obvious that it would be worth the headache of making the switch given that the only real advantage to Celsius for most use cases is the mere fact that it's a standard.
You are ignoring all the costs incurred by immigrants and international travellers having to learn to juggle two different systems in their heads, the obstacle it poses to international communication (e.g. “40 degree day” means radically different things in American vs Australian English), products having to support both units and then having configuration settings to change them, people being inconvenienced when they can’t work out how to change the units setting, publications forced to include both units to ensure all readers understand, etc. Those costs are ongoing and cumulative over time, whereas the cost of switching is a once-off which most of the world has already paid
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.
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.
Kelvin is refined measurements used to relate to a wider scale of temperatures. Celsius is a metric human scale subset of Kelvin.
Edit: this comment was deeply stupid for obvious reasons and I regret trying to interact with other people when I should be asleep.
The equivalent would be saying that going from 600k to 700k was a 100% increase... compared to 500k.
It's not completely meaningless, to be fair. Saying 10°C to 20°C is a 100% increase has the meaning of "it's twice as far from freezing", which isn't totally meaningless (kind of like saying Everest is twice as high as Mont Blanc, which really means "its summit is twice as far from sea level").
If your ”whatever” target instead was 50k, is the argument that going from 100k to 200k would be 400%?
If the argument was saying there's something special about 100% being 100 quantity then.. no? I don't really know where to go from there, what I said still holds with a 100k target, but I'm not going to be able to give 'another' example where the 100 quantity is meaningful because it isn't for degrees either. It's the freezing point at 0 that makes it work better for centigrade than Fahrenheit, imo.
== 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 apologise.
This is done when people rate the efficiency of home heating: SCOP is a function of the heat pump's ability to hit a particular temperature, for instance.
I'd guess the baseline temperature on the tube should be 21C maximum. Percentages don't make sense here, but 7C over the target temperature (for instance) is pretty bad in those terms. I'd be surprised if TfL hadn't set that somewhere.
Also worthy of note is that it sounds like the tube is a prime source of heat for a district heating system. Win win, perhaps.
If you go from freezing water to boiling, it's only 37% hotter!
It’s a huge increase, if not for the reasons they describe.
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).
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.
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.)
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.
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?
Additionally you’re making the assumption that line voltages are stable and constant, and can be tweaked as needed. They’re not, they’re some of the most noisy, electrically unpleasant power systems in the world, with voltage bouncing up and down as trains accelerate and decelerate, consuming up to a MW each under peak load.
Power distribution companies hate providing power to train systems because you need so much infrastructure to handle the noise and prevent the train line from seriously degrading the local power grid. The substation that connect train lines to the power grid are constantly having their switchgear trip in and out as the huge spikes in demand cause the equipment to momentary disconnect to protect downstream equipment.
So creating headroom for extra regenerative breaking isn’t a simple thing to do. When each train can instantly consume as much power as 10 households all maxing out their power supply, electrical systems stop behaving anything like “normal”.
see https://tfl.gov.uk/corporate/transparency/freedom-of-informa...
Seems not trivial to just put extra batteries and the circuitry for regen breaking charging in.
It may be better to install such batteries somewhere on each track circuit as fixed stations, that can vent their charging and dispersal heat away from passenger tubes, rather than mobile — assuming that onboard emergency power needs are already met.
That's not really the problem; the problem is there is _no space_. Ever been on a London Underground train? You certainly wouldn't want the interior getting _smaller_.
I'm sure they'd consider the worst-case scenario, and at present that's probably some serious arcing within a motor causing a fire. Cutting the track power (easily done by the driver) then makes that a fire that can be handled with water and/or foam.
Smoke from large batteries would be very hazardous.
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...?
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.
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.
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
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.
[0] https://www.mdpi.com/2571-8789/8/2/47
(I don't think my comment implied that the sunshine makes it hot in the tunnel, only that when it's hot above ground it's nice to be cool below, like in the poster. And I did include a figure of 25m for average depth, I've spent enough time on their endless stairs to know that the TfL delved to greedily and too deep. This spiral staircase has 320 steps, I shudder.)
So the ground can take up more heat, but it can't do it quickly enough.
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?
There's a nice article here which goes into more detail: https://www.ianvisits.co.uk/articles/cooling-the-london-unde...
I think Oxford Circus is one.
As I see it, it is just a marketing problem with easy solutions.
There is psychology and reverse psychology. You could fool people into embracing the heat by redecorating the stations and trains to make it a 'journey to hell, via the centre of the earth'. The stops south of the river could be marketed as Dante's inferno and hellish.
Or you could go the other way, to make it kitch Hawaiian themed, so people expect the heat and to embrace it as a mini-holiday.
Or, the stations could be redecorated as if it were a trip to the Antarctic, so people see images of penguins braving the ice, with murals from the Shackleton days, to imagine they are cold.
In places like Moscow the underground train stations give the impression that people are in splendid palaces, this works pretty well. As I see it, TfL just need to up their decor game, problem solved.
As I posted in a cousin comment, I found this nice blog post examining some of the more serious ideas, including water-cooling: https://www.ianvisits.co.uk/articles/cooling-the-london-unde...
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.
> WILL THIS GEOTHERMAL PANEL SYSTEM COOL MY UNDERGROUND SPACE?
> No, the Enerdrape system primarily draws its energy from the ground. This does not affect the comfort of people using the underground space.
These are some of the deepest tunnels going under some of the most built up parts of the UK.
To build enough windcatchers to move the needle on tunnel temps, you'd need to buy many plots in one of the most expensive cities in the world.
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.
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.
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
There is a minor fandom controversy over the Ministry of Magic in the Wizarding World and whether the "Ministry for Magic" and "Minister for Magic" are valid alternate terms, but I have only identified one instance where JK Rowling wrote it this way, and it was outside the novels. Canonically, Harry turned 17 in 1997, so I suppose Tony Blair's reforms wouldn't apply post-Voldemort. However, Platform 9¾ is now "properly labelled" in the Muggles' King's Cross Station.
https://commons.wikimedia.org/wiki/File:Cmglee_London_Kings_...
Travellers should also mind the gap between "TfL" and "TLF Travel Alerts", a defunct account which was part of Weird Twitter, and somewhere I hope I can dig up an archive, because the daily alerts were comic genius in 140 characters or less.
https://commons.wikimedia.org/wiki/File:Paddington_Bear_Stat...
The arrival of Paddington Bear from Darkest Peru may be partly explained by the heating of the Tube stations. He surely would be right at home in a dark, humid and warm environment. My mother encouraged me to read about Paddington Bear, and in 2008 I was privileged to have a layover in Westminster, where I passed through Paddington Station and totally missed out on visiting the Paddington Bear statue therein. But I was able to purchase a refrigerator magnet bearing the "MIND THE GAP" official logo, which I presented to her in gratitude.
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.
And now you've got this wild 19th century Jules Verne-esque icepunk world in thermal runaway all built up for a hell of a novel-to-be.
There's probably more efficient materials to use, big lumps of supercooled metal. Someone else mentioned liquid air, that could just be evaporated in the tunnels and stations.
Of course, generating liquid air costs a lot of energy too. I'm sure the problem is easily solved if you assume infinite and free energy.
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.
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.
In safety engineering you do have to think about low-probability events.
I'm sure that this is probably one of those stupid suggestions that shows a lack of understanding of the problem, but could skipping stations help help this? Something like the following gets you 1/3rd less braking energy released into the tunnels:
Station ABCDEFGH
Train1 .. .. ..
Train2 .. .. .
Train3 . .. ..
(You could get around that by running the trains further apart, but that would be a critical loss of capacity).
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
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.
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.
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.
To put this in perspective, Sadiq Khan already runs the system at a massive loss. They just about cover their operating costs at the momemt, and rely entirely on grants from the rest of the country to do upgrades of any kind. So cooling efforts have to be very cost efficient. Also the UK grid is very supply constrained. New nukes are being built but there have been the expected massive cost overruns and problems, so any large new energy demands in the UK just aren't happening anytime soon. It's actually been deindustrializing due to very high electricity costs.
Also the underground is funded pretty much entirely by fares paid. Past UK governments have cut any tax payer subsidies for TfL to zero for day-to-day operational costs, and there’s zero indication that’s going to change any time soon.
I didn’t claim all technically possible solutions would be politically acceptable.
Update:
There’s not a huge amount, but with careful search term tweaking I did find this on the Elizabeth line thermal loads:
https://learninglegacy.crossrail.co.uk/documents/the-design-...
> This paper for a possible energy segment installation was written during the design phase but the proposal was not implemented.
Bleah.
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.
Energy can be dumped in during the summer for cooling, and taken out during winter for heating.
It would be more efficient that ground source geothermal as it's a closed loop system, so heat won't leak away.
My house needs around 2500kWh per year, so you'd need a tank of around 100,000 litres. That is 8x8x1.5 metres - basically a small basement. To get that energy out youd need to heat it to 60c in the summer, and it would cool to 30c in the winter. You could even do that with passive water flow, no heat pumps needed.
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?
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.
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.
Was there? I don't recall the event, and can't find references on google.
I had assumed that it was infamous enough not to require much more detail, has it really been that long ago that people didn’t know about it.
https://www.btp.police.uk/police-forces/british-transport-po...
It seems I had muddled the name, I meant to say the tunnel by Russell Square tube station.
Coming up to years ago in a few months…
20 years
I've never heard 7/7 associated with the olympics before.
And the Northern line is no picnic either.
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.
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.
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.
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.
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.
London Tube trains largely do not have AC, so heat in the tunnels is a big problem.
If NYC Subway has AC then it’s silly for the GP to compare the London Underground to the Subway.
If pumping water up and down that distance is infeasible, then make the primary coolant loop use a phase change refrigerant. Much easier to pump long vertical distances. Condensed fluid would flow down with gravity, evaporated gas would flow up.
Is TfL not monetising this thermal mass? Why not?
Heating and cooling benefits from remarkably small differences in temp. Thats how heat pumps work. And, lifting the input temp by only 5-10 degrees C can make a huge difference to the energy required to get to the next level.
It takes about 200Kj to heat 1L of water from 10C to 60C and 125Kj to heat it from 30C to 60C -A 37.5% saving in energy inputs. You better believe a corporate would seek a 1/3 reduction in energy input costs.
(my sarcasm meter is broken sorry if I ruined a joke)
The line is itself a giant distribution system and is pretty much designed to retrofit pipes into.
The commercial premises would merely have to tap into something which is within a few tens of metres of their basements, and in some cases they very probably have access hatches already.
You are heating your working fluid to a temperature equal to what's ambient within the heat exchanger, which takes the longest possible time of any heating this exchanger can perform. (Think it over.)
For the exchanger to operate continuously - that is, to sustain outflow at final temperature equal to inflow at initial - this means you need a lot of piping, because however many CFM of water at 10° (or whatever) come in, you need to supply exactly that many CFM at 30° out.
All that piping takes volume, which has to be excavated out of the clay in which has been sunk the heat we're striving to remove. There's no moving that without some heat exchanger, after all. So we're still stuck expressing time basically as volume, which is perhaps the worst possible misfortune when working underground. (Caissons can be built and pumped dry, where earth must be dug.)
Perhaps you're thinking of a cooling jacket lining the tunnel bore. This would make sense but will only operate at a net energy cost, because to sustain livability you're going to need to exchange heat outside the system and supply, effectively, refrigerant. From plants all over town...
https://www.bbc.com/news/articles/cy9xxlky2pno (2024)
> Phone signal goes live on 25% of underground Tube
It's one of the oldest metro (retrofit cooling), it's deep, high usage, it's surrounded by isolating clay, dense city.