Half a croissant, on a plate, with a sign in front of it saying '50c'
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London's New Air Conditioned Underground

come on... there's £100,000 in it.
  [vote for,

Mr Ken Livingstone, Mayor of London, has offered £100,000 to anyone who can invent an air conditioning system for the tube (metro, subway)

I've noticed that no matter how good an idea posted to halfbakery is, there will be a bright spark who will improve upon it in some way.

So... let's invent a solution for Ken and share out the winnings.

First stab: Air is circulated brilliantly through the tube network via the trains. They push and pull air which does help soothe sweaty brows on hot days. The issue is that this air is neither cold or particularly fresh.

My idea is to line the inside of the tunnels - lets say the 10metres either side of stations - with a closed network of refridgerant gas tubes, like those you might find in a freezer. This might have the ability to cool the air in the tunnel to -22C. As the train enters the station, it would push this cool air onto the platform, as it leaves, it would drag further air from the refridgerant area. Maybe add a lovely lemon scenter to the system to help freshen it too.

So... its a first stab.... any better ideas or improvements

jonthegeologist, Jul 17 2003

(?) Ken's Reward Offering http://www.ananova....tory/sm_800026.html
£100,000 for the bakers [jonthegeologist, Oct 04 2004, last modified Oct 06 2004]

The Tube and air conditioning http://tube.tfl.gov...tent/faq/tipsac.asp
No mention of the prize on the official site. All talk? [bungston, Oct 04 2004, last modified Oct 06 2004]

Tube map with Thames overlay http://tube.tfl.gov...on_connnections.gif
[bungston, Oct 04 2004, last modified Oct 05 2004]

a few half-baked ideas in here http://london-under...ground_archive.html
[po, Oct 04 2004, last modified Oct 06 2004]

Ideas already posted to the BBC http://news.bbc.co....gallery/3088051.stm
recognise a few of these ideas [jonthegeologist, Oct 04 2004, last modified Oct 06 2004]

What about this? http://www.halfbake...lly%20the%20Penguin
[silverstormer, Oct 04 2004, last modified Oct 05 2004]

"Right, you can turn it off now." http://home.eunet.n...id-ice-tunnel-5.htm
[Amos Kito, Oct 04 2004, last modified Oct 06 2004]

Water body used as heat sink. http://www.halfbake.../Pool_20Heat_20Sink
[bungston, Oct 04 2004, last modified Oct 05 2004]

Cheap public transport air-conditioning Cheap_20public_20tr..._20air-conditioning
I sent this idea off to Ken, but didn't get a response... [hippo, Oct 20 2006]


       apparently, its more complicated in London because of the depth and size of the tunnels. Am no expert, but would have thought it easy. It clearly isn't, hence the reward.
jonthegeologist, Jul 17 2003

       spent ages looking for this the other day. go for it jonno.   

       hey, no this is a different idea. what happened to the one that used the space under the lines. which line should you avoid touching if you fall down there, by the way?
po, Jul 17 2003

       It’s still there [po] - ‘Tube aircon’.
Shz, Jul 18 2003

       Why is this a problem? Is it the sheer volume of air?
phoenix, Jul 18 2003

       What? Screw sharing. That money is mine. Just wait until I invent the disintegrating air conditioner...
DeathNinja, Jul 18 2003

       The only place in the tunnels there'd be any room for air conditioning or refrigerant lines is in the sumps. Otherwise the tunnels aren't much bigger than the trains.
supercat, Jul 18 2003

       The problem is the tunnels. If there weren't all those tunnels, it would be easy to air condition the stations. What is needed is a sphincter of some sort on the entry and egress orifices, to keep cool air in the station. Once you are in the train, the tunnel air doesn't matter - the train is air conditioned.   

       I envision a mauve, HR Giger type construct as the ideal, but you could do a poor man's version of this with thick, clear overlapping plastic strips which hang to occlude the tunnels. These would tend to keep cool air in the station, and would be easily bashed out of the way by the train.
bungston, Jul 18 2003

       Or use automatic doors and air curtains, like supermarkets.
Worldgineer, Jul 18 2003

       I just read tube.com. They want to air condition the trains themselves. The problem is that the heat is pushed into the stations which are so small and old they might overheat. I thought it was the stations they needed to cool. Hmmm...
bungston, Jul 18 2003

       In that case I think their approach is wrong. Cool the stations, and you'll defacto cool the trains. If that's not enough you can always cool the trains as well, and since the stations are conditioned there's no heat migration problem.
Worldgineer, Jul 18 2003

       Refrigerant lines parallel to the tracks? I'm thinking Peltier-effect surfaces, but you still need to dump the heat. A series of water or refrigerant pipes parallel to the tracks?
phoenix, Jul 18 2003

       What about putting the heat exchanger of carriage AC units on the undersides of the carriages and having nozzles squirt water onto them. Water would then collect in the sump where it would be in contact with the iron walls of the tunnel, losing heat until the water was pumped out, filtered, and recirculated through the nozzles again.
supercat, Jul 19 2003

       The trains are already supplied with electricity and the idea is to cool as little volume as possible - hence carriage cooling.   


       * London Underground trains are very small and each car is isolated - this leaves little space for cooling equipment.   

       * If you have a heat exchanger, it'll pump out heat into the tunnels which would heat up and blast the stations which have poor ventilation as it is.   

       * It's difficult to ventilate the tunnels between stations because all of London is overhead.   

       * You could put platform doors in, like Singapore, but some stations have very curved platforms and the trains don't stop in precisely the same position.   

       * Significantly upgrading the trains' power usage _might_ affect system stability.   

       All this engineering would cause delays and cost several fortunes.   

       My solution:   

       * You need to cool the trains without exchanging heat into the tunnels. I propose converting half or one whole carriage as a pump and coolant tank unit.   

       * The tank would be filled with chilled water that would be circulated through insulated chilled water pipes to split-type a/c units in the carriages. The A/C units would be mostly passive and pull in fresh air from outside the train.   

       * The tank would be split into two halves to allow passengers out through the driver's cab in an emergency. Only one side would be full at any one time. At the terminus, one tank would be filled with chilled water while the other was drained of warm water. This would minimise turn-around time. Chiller water would cleaned and be recycled.   

       * All the plant would be contained at the line terminuses, achieving super-efficiency through economies of scale.   

       * An alternative solution would be large blue gel ice packs with a built-in heat exchanger that could be fork-lifted into the side of the lead/trailing carriage. This would minimise turnaround time and additional weight, but would be technically more complicated.   

       * Also, I know that some lines spend much of the time above ground. Maybe it's possible to have cooling units on the trains that use conventional ambient air heat exchangers above ground to cool carriages of a chilled water tank, and switch to tank water only underground.   

       I figure this is the minimum cost solution that requires the least capital outlay, alteration of existing systems, and delays/ inconvenience to passegners.   

       The only problem I can identify is the balancing issue of having one side of a carriage full of water and the other empty. This could be solved with partitioned, isolated tanks that allow atlernate ones to be filled.   

       I hope that some engineering firm picks this idea up and claims to prize. All I ask is that we at the Bakery get due credit. It would be nice to see some good publicity.
FloridaManatee, Jul 19 2003

       perhaps we should cool the *people* right down as they buy their tickets (no idea how exactly) then as they travel they take up the heat and take it away with them when they leave.
po, Jul 19 2003

       London doesn't need aircon on the tube. We could do what they did in NYC, but then you've got freezing trains (great) and ridiculously warm platforms (d'uh). Rather than waste our resources on this, we should make more cycle lanes to treat the problem, not the symptoms.
neilp, Jul 19 2003

       cycle lanes down the underground? sounds dangerous to me.
po, Jul 19 2003

       // What is needed is a sphincter of some sort //   

       Would we need to paint the cars brown?
RayfordSteele, Jul 19 2003

       How much longer could trains be without causing major signalling and switching problems? I know that on the Picadilly the trains are already longer than the stations (the public-access doors of the cars are over the platforms even though the cars themselves extend beyond). I think the idea of having a cooling car at one or both ends of the train might be a good one, especially if the car can "store" coldness [e.g. with a large block of ice]. I wonder how large a block of ice would be required to cool the train during one round-trip circuit?
supercat, Jul 19 2003

       [fogfreak], let's say you need to remove the heat produced by a train load of people.*   


       Human Resting MR = 1.5kcal/min;
x average 50 pax (ish) per car;
x 6 cars;
x 1.5 hours per trip x 60 mins
= 40,500 kcal (Kilocalorie = 1 Kg water by 1degC)

       Assume 1 degree C water raised to 21 deg C (20 deg C increase)   

       => 2,000Kg
= 2.0 Metric Tonnes (about 27 UK-sized adults or one empty family saloon) or 2 cubic metres

       Maybe there'd be some thermal leakage and other inefficiencies, but you're still ball-park OK if you're under 4MT.   

       *Actually, it's not even so bad. Some heat is lost to ambient (tunnel) air and the surrounding rock even without a thermal accumulator unit. You're just adding a bit of extra cooling. And besides, if you ran a vapor-compression cycle unit when the train was above ground, you'd cut the necessary duration of the heat-accumulator cycle to maybe 45 min.   

       No need to extend the trains. No need to worry about forklifts, pumps, etc. You won't bake the stations. And it won't cost a fortune.
FloridaManatee, Jul 20 2003

       The link above says that the problem lines are the Piccadilly, Northern and Jubilee. The map linked above shows that the Piccadilly line crosses under the Thames river at at least 2 points. The river would have a huge capacity to carry away waste heat. Perhaps an air conditioner could be made which has heat loss fins protruding up from the river bottom? Maybe they could protrude all the way up to the surface, appearing as a school of freshwater dolphins? Or you could pipe water down along the tracks, into a reverse-radiator type device, then back up to the river - multiple cool riverwater pipes should cool the air fairly well, and if they went downstream the water would flow thru them without energy input (a siphon). Probably the reason that the Piccidilly is hot is that it has to be deep enough to get under the river. Deep = hot because of less air exchange; also possibly closer proximity to Hell.   

       Of course this does not help the lines distant from the river.   

       Finally, I would love to see a link showing how one can actually answer the prize challenge. I found loads of news reports, but nowhere to send ideas.
bungston, Jul 21 2003

       //Deep = hot because of less air exchange; also possibly closer proximity to Hell.//   

       From the "Tube" map, I notice that the Northern Line runs through Elephant & Castle and the Jubilee Line serves the East End. Perhaps they could simply reroute?   

       //Finally, I would love to see a link showing how one can actually answer the prize challenge. I found loads of news reports, but nowhere to send ideas.//   

       I failed to find a link too. I figure a real competition would have lots of details and rules (such as how detailed the proposal must be; does it need technical plans and engineering analysis or simple ideas like the above). It's an interesting theory that it might be a publicity exercise to show that they face insurmountable difficulties but remain open to ideas.   

       OTOH, if an engineering consultant were called in to solve the problem, I expect the fees could be an order of magnitude higher then the GBP100k 'reward'.
FloridaManatee, Jul 21 2003

       I think the trains accommodate more than 50pax/car during rush hour, but was wondering whether it might be possible to have semi-portable ice/brine units placed into the unused "interior" motorman compartments. Ice has much more thermal capacity than water, so one 1MT unit in each unit should provide enough cooling capacity for a round-trip.
supercat, Jul 21 2003

       Could the staff not just hand out free "Chilly the Penguins"?
silverstormer, Jul 23 2003

       how about a watering system that sprays porous cement walls "the tubes"(grooved would be best for surface area) and add some minor chemicals to prevent mold and a scent for smell and as the cars work back and forth through the system wella an evaporetive cooler. Its not a air conditioner but stored earth would provide a good cheap cooling system   

zimbob, Nov 26 2003

       zimbob: At least the older parts of the deep underground are built of cast iron pipe. I'm sure they're already exposed to moisture, but I wouldn't want to add to it.
supercat, Nov 30 2003

       I believe there is simple answer. What you have to do is utilise the energy that is already wasted and convert it into useful work. With the trains travelling through the tunnels a large amount of air is "pumped" forward and the temperature is increased trough friction etc. It has already been shown that a 9 deg reduction in tunnel temperature will result in a 6 deg reduction inside the trains. My solution is that some of the air forced through the tunnel is channelled into large water /air heat exchangers along the tunnel wall (or under the track) at each station. Also at each station is a "vortex" style water cooler. (Did you all know that water cools in a vortex) The energy inputs to the cooler is the air movement itself as well as the energy contained in the "higher" temperature water. When conversion is made to the energy in a vortex, the system becomes self sustaining. THERE NEEDS TO BE NO OTHER ENERGY INPUTS In fact there is likely to be more than enough energy generated by the system that would provide for the platform lighting reducing wastage even further.
tasman, Jul 13 2004

       Not bad Tasman. I will have to look into the vortex cooling system. Your idea has the marked advantage that it doesn't need lots of technology, expense and engineering. I don't know how many people in this thread travel on the tube - sounds like a few of you do, but it must be remembered that it was built around 600BC by the Romans, has had approximately £1.37 spent on maintainance and investment since then, and is currently walking the usable/not usable knife edge. As for //How much longer could trains be without causing major signalling and switching problems?// there are already major signalling and switching problems. No idea will work that involves taking up valuable carriage capacity or vast expenditure (the estimates for bringing the tube up to the standard we need are all in the multi-billion-£ area). I'm backing the 'use the Thames' ideas, the 'use the sumps' ideas and Tasman's 'use the air pressure of the moving trains' idea.
wagster, Jul 13 2004

       Sorry to dig this topic out after so long, but something's been bugging me for ages, and I'm sure someone here will be able to tell me why my idea wouldn't work (or would...). I'm no engineer, so I'll keep it brief. Each tube carriage has (at a guess - I never remember to count) at least 8 wheels. If a dynamo were fitted to each wheel, the electricity generated could power chiller units built into the roof of the carriage. I've searched the web for this type of solution to the problem, but couldn't find anything similar. Comments?
jtp, Oct 19 2006

       [jackthepickle], let me get this right, you want to fix an electric motor (dynamo), to 'harvest' the energy wasted by an electric motor (the wheels), in order to power an air conditioning unit ?   

       Rather than point out the obvious foolishness around fitting a dynamo to a motor (when you could just take the electricity from the power supply of the train itself), I choose instead to ask what happens when the train stops. Do your dynamos just stop going round ? so you turn on and turn off your air conditioning maybe 2,000 times a day.   

       Bonus points for the extra heat generated by your new dynamo set up.
neilp, Oct 19 2006

       [neilp] like I said, I'm not an engineer, but maybe I have used incorrect terminologies. When I was a kid, I had a light on my bike that was powered by the rotation of the wheel. Could a similar device not be fitted to each wheel on the train, and instead of powering a light, they power some type of cooling unit? In an earlier anno someone mentioned that "Significantly upgrading the trains' power usage _might_ affect system stability" which is why I was looking at alternative methods. Sorry if I appear thick!
jtp, Oct 19 2006

       [neilp] is right, but could have been a bit nicer about it. Then again, perhaps it was fair of him to assume that you would know this.   

       <aside> everyone is getting a little bickery of late, me included. why? It's not like it takes any more effort to be polite...</aside>   

       I don't know if each wagon has an electric motor, or if there are "engine" cars. Either way, each car has power, and therefore could be retrofitted to have sufficient power for individual airconditioning units per wagon. Your solution suggests installing a mass of dynamo's, just to generate some electrical power to run aircon. You are simply proposing an inefficient method of transporting energy from the motor carriage to each wagon, which could be far more easily implemented by running an AC cable to each wagon. we still have to solve the problem of small reliable efficient AC units per wagon.
Custardguts, Oct 20 2006

       //It's not like it takes any more effort to be polite// nothings for free at halfbakery...
po, Oct 20 2006

       There needs to be an efficient method of storing or converting the extracted heat from the carriages. Simply venting it into the tunnels won't work for reasons sited by FloridaManatee who seems to understand the problem well. There must be a more efficient method of storing and reclaiming heat energy than tanks of water.   

       My own "solution" is to permanently connect the trains with a moving connector to an extraction pipe running along the track between the rails.   

       The connector would be in the form of a rotating drum wheel with protruding valves that line up with corrresponding holes on the flat profile pipe, so that the hot air is blasted through the wheel, and into the holes in the flat pipe. Only valves on the wheel in contact with holes on the pipe would be open, so there would be no escape of hot air....   

       Think of a toothed wheel running along a flat pipe with indentations that match the teeth. Now think of the "teeth" as short tapering pipes with a valve on each end that the rotation controls. I may draw it up if anyone is interested.   

       That was an easy one - can I have the £100,000 now please ?
xenzag, Oct 20 2006

       Impressive & highly original. The cheque's in the post.
jtp, Oct 20 2006


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