Air Conditioning, Part 1

all making stuff colder technology that has ever existed. We're going to be focusing on the invention of systems primarily for cooling and removing humidity from interior spaces, primarily, but not exclusively, for the comfort of humans and other animals. Right that. Now that being said, we are going to mention some some some various cooling technologies and air circulation

technologies on the path to modern air conditioning exactly. So, I will say that I can speak from pre recent personal experience, actual actually multiple experiences, to say that if you are lucky enough who have air conditioning in your home, in your workplace, and the places that you dwell, especially in the hottest months of the year, especially if you live somewhere hot like in the American South or anywhere near the equator, I guess, or Atlanta or Hotlanta, as

they know that they do not call it. If you are one of these lucky people who has this technology, you should not take this blessing for granted. You should remember every sweltering day to be thankful for this luxury. I once lived in an upper floor apartment in an old house in North Carolina, as though there was an apartment below me, and I went the better part of a blistering summer there with no air conditioning. And you know, I don't want to over dramatize my my own struggles,

but I just remember, like my brain didn't work. I remember standing at the refrigerator with the freezer door open and my head stuck in it, which don't do that, folks. I mean, that's not energy efficient, but you know, it just short circuited all my rationality to be in this hundred degree apartment. I remember I would lie on top of my bed and try to sleep at night, just making like a human sweat angel, like a you know,

a human shaped sweat imprint on the top blanket. It was disgusting and and more recently actually just last year, our home air conditioning and it completely broke down. In the middle of summer, and it was several weeks before we get the problem fixed. And again, maybe I'm just a whimp, but I found that in a house that's like ninety degrees plus are close to a hundred degrees

with high humidity, my brain just broke. I remember sitting at a desk trying to do work with like a wet towel around my neck and a box fan propped up pointing at my head, and it just it never felt like enough. The hot, swampy summers down here can be brutal, and it really makes you appreciate again how lucky you are if you have access to this modern convenience,

especially in Hotlanta or swamp Planta. We can call it that, I guess, but I got to give a shout out to my A C guy, Mike, who Robert here referred me to. Yes, my Mike is great. Effects fixed mine up as well. And indeed, air conditioning is one of those things when when it's working properly, you you hardly notice it at all and you just take it for granted. When something goes wrong, that's when you start sweating, and in all possible ways. Uh, sweating at night getting the

proper terrifying night sweats on. And you know, one of the things is, is I get older, I do find that I enjoy the heat. Like I I love to read and write on my front porch, and I'll generally like push that as far as humanly possible in either direction. Like when it's colder, I'll bundle up as much as possible, but I can't quite bundle my fingers. And then at that point I'm driven inside and I have to come out when you know the warmer person portion of the day,

and then what is it gets hotter and hotter. Uh, you know, I'll do whatever I need to do to try and keep the mosquitoes away, you know, burning like um, you know, ritual citronella candles, and wearing more clothing than it's perhaps temperature appropriate, just to keep them from biting that sort of feasting of my blood, that sort of thing. But but but you know, I don't mind sweating out there. I can also, you know, bring out a fan if

I need to to keep the air moving. And of course, as is common with with a lot of you know, front porch scenarios, if you have a porch swing or a hammock on hand, like, that's ideal because you're able to keep the air circulating by keeping yourself in more or less continuous motion. Um. But then eventually you reach the point or I reached the point where I I have to come inside because it will just get too hot.

And I enjoy having the choice, the privilege of being able to come inside and enjoy the you know, the cooler air. And you know, it's not only a privilege of our modern age, it is a privilege in our modern age. Yeah, there are millions of people around the world in hot climates these days without air conditioning, and air conditioning does not come without costs, that's right. I should also say that on my front porch, having uh, you know, a readily refillable supply of ice water is

a must. And of course that's that the history of refrigeration is is right up there with the history of keeping spaces cool. Uh. So you know, both of these

are technologies that we take completely for granted. So many of us that are listening to this podcast you have not only um uh you know, cool air inside your home, but you have a miraculous machine that can turn liquid water into ice, perhaps automatically, and even if not automatically, like still very passively, you're not having to actually crank

it out. All right. Well, before we start talking about air conditioning systems or pre air conditioning systems for enclosed spaces, we always like to ask the question what came before? I guess the deepest you can go on what came before for air conditioning technology is biological cooling systems and thermoregulation in the body, right, and for us that means sweat and and this is going to be key to the methodology of all these various air conditioning and temperature

control UH technologies that we're going to discuss in these episodes. So, your body produces sweat and UH with the in sweat evaporates from the skin to cool the body. That's essential is the evaporation, right. It's kind of how in fact it works for anybody of water. Right. You can take a just a bucket full of water, and the evaporation off the surface of that water will cool the water in the rest of the bucket because that evaporation is an energy hungry phase transfer, and it as to suck

energy out of the heat from the rest of the water. Yeah, basically, liquid water evaporates into vapor using the thermal energy in the air, resulting in a lower air temperature. The water in sweat absorbs your body's heat energy and then evaporates, lowering your temperature in the process. That is evaporateate of cooling. Yeah, evaporate of cooling is one of the really cool things about chemistry when you really think about it. Here's the

questions kind of similar. Um, how come when you boil a pot of water on the stove and it reaches the boiling point, the entire pot of water doesn't transform into steam all at once? Do you even think about that? Yeah? I was wondering about this one time, one one contemplates while watching the pot of water boil. Right, one of the most entertaining of activities. But yeah, it can. It can raise some interesting questions in your mind. And I think the way this works is that as water boils,

some of that liquid water is turning into steam. That's a phase transition. It's the same thing that's happening on your skin. Liquid water in your skin is turning into water, vapor into steam and coming off of your skin. But as that happens in the pot, as that water is turned into steam. The pot of water loses energy in that process because it's a massively energy hungry process to

turn water into steam. And so as the water is turning into steam, the water is constantly cooling back down and you have to keep putting more energy into the bottom of it to keep it boiling. And because it's largely a good thing, because I'm thinking about scenarios in which in which like large portions of water um are turned to steam instantly, and you're generally talking about an explosive situation. You're talking about an expansion of steam that

can you can have, you know, catastrophic effects. You wouldn't want the pot of water you're boiling for spaghetti to suddenly become steam all at once, No, I mean you need massive energy inputs for that kind of thing to happen, just because it takes so much energy to turn water into steam. And again that's a good thing for your body.

Taking that energy from the body cools the body off. Now, when we turn to technological solutions for cooling a space, there were actually tons of brilliant inventions or little innovations and tweaks in the design of homes and buildings, UH for this purpose before the invention of modern like electrical

air conditioning using heat pumps or refrigeration or anything like that. Yes, the accumulation of all these little tweaks, all these little advantages that all add up to make hot temperature environments more bearable. It reminds me of like, you know, the the argument that you you you win a battle of all the small, little advantages to your side, you know, and it's very much that the case with you know, waging war against a hot climate. Let's talk about some

of these little innovations throughout history. The first is I would say the absolute most dirt simple probably doesn't even need to be mentioned, but won't mention it anyway. How about a roof that's having having a top level covering provides shade and that blocks the radiation heating from the sun. So that's one of the most important innovations in designing a cooler space. Yeah, in the same way you would take you might take comfort beneath the tree or you know,

by the side of a cliff, some naturally occurring shade. Uh, we are able to construct our own shade as well. But of course, by having a house that has a roof on top if all else fails for keeping the house cool at night, one option you would sometimes have in the ancient world as you could go out and you could sleep up on your roof. This seems to have been common, for example, in ancient Egypt, where a significant amount of living and sleeping happened on people's rooftops.

That's right. In in past episodes of No I honestly can't remember it was this show or stuff to blow your mind, we talked about some of the ancient cities. I think this was in our toilets episodes. We're talking about the archaeological remains of cities in which you know there were entrances on all the roofs um. But also we can look to ancient accounts, say Herodotus writing of the hanging gardens of Babylon, or in Jewish lore, King David glimpsing Bathsheba bathing uh while resting on the roof

of the palace. Yeah, I guess the idea is probably that it was like nice and cool out in the open air on the roof and where also you're going to be. But there are tons of other little ways that once you go beyond just having a structure with a roof to block the sun. And you start building houses with openings and windows and different hallways and rooms, there is uh, there's all this investment in the architecture

of a house to help aid in cooling. And this would include the positioning of windows or other openings, the shape of rooms and floors that allow ventilation of the inside and encourage cross breeze is to pass through. Also, something that I feel like is is less uh is thought about less in modern home design is the positioning of windows away from direct sun or in the shade.

I think because houses are designed with the idea of air conditioning in the mind often these days that there's less planning put into Okay, where where are the windows, What kind of light are they going to get? Is there a tree to shade the window? And so forth. Yeah,

we'll definitely come back to this in the future. But we we we see this, uh, this this trend where all these tiny advantages were discussing in the With the advent of modern air conditioning, so many of them were just abandoned because they weren't seen as useful anymore as necessary to keep a cool uh you know, habitat, and part of the problem then, is when the air conditioning goes away, or when the electricity goes away, whatever is disrupting things, you have to fall back on a habitat

or building that is not built with any of these advantages in place, or even if you're not talking about using your air conditioning, if you're just considering energy efficiency. I mean, I think that there are some houses that are designed without proper thought about energy efficiency for heating and cooling in the house, even if you have modern heating and cooling devices. Yeah. I mean when you're when you're a kid and you're around air can I remember

just loving it. I was like, I just love the smell of the air conditioning and just wanted on all the time. You know, when you're adult and you're actually paying the bills, you don't necessarily want the air conditioning all the time. It would be nice if it went

off a few times during the month of August. Uh So, yeah, you know, it would be nice to have so many of these other little, um, you know, design advantages in place as well to just reduce you the necessity of running the a C. Here's another design advantage that predates modern air conditioning. How about construction that takes advantage of the fact that warm air rises, also known as the chimney effect. So one example of this might be high ceilings.

Another is top side ventilation including passive roof vents or more recently, an attic fan, and so that this can be paired with windows to create this ideal airflow situation where cool air flows in through open windows on the lower floors and then is drawn up through the house in a sort of air column that goes up towards the attic and towards the roof, creating pressure that pushes the warm rising air out through vents in the upper

floors or in the ceiling of roof. Yeah, well, I have one of these attic fans in my house, and it's it's it's like being a spaceship, you know, because you can just especially if you have only like one window open, you can just create this terrific flow of air through the house, which can make a huge difference of you know, you get kind of like it's gotten a little warm, it's got a little hot inside the house, and you have a like a nice comfortable temperature drop

outside of the house. You can easily equalize things like that a couple of other things would just be what do you make the house out of, Is it insulated in the proper way, something that's not going to heat up and pass heat from the outside to the inside. And then another thing would be the outside color ration of the house that can affect how it absorbs heat. Do you live in a like a black obelisk or do you live in uh, you know, some sort of a white reflective uh domicile, And it's gonna make a

huge difference. And back to your point about a heat rising uh you know this also you see this in designs of you know, older houses with high ceilings. Obviously it's not the heat is going to rise out of the area in which you were living. But also you look at a lot of modern houses and the reliance on a c and where do you see the master bedroom. You see it on an upper floor, right like it becomes more of a selling point of you're you know, saying, okay,

it actually has a master on the main floor. And a lot of that has to do with, you know, individuals get older. It's nicer to not have to go up a flight of stairs in order to get to your bedroom. But but also you have to to realize it's going to take more to keep that cool up there like it's it's it's ultimately from a temperature standpoint, perhaps it's better to have the master bedroom on the

main floor. Yeah. Absolutely. The one thing I think we shouldn't forget is how common I mean we mentioned people sleep being on the roofs. You shouldn't forget that in hot climates, it used to be extremely common for people to sleep outside. Oh yes, I was reading about this, and in times before air conditioning, and in places where

there's no air conditioning. Now it's just very common for people to sleep on porches in front of their home, or on the deck behind their home, or in or just up on the roof for somewhere out in the yard. I mean, this remains a way to stay cool at night. So we've talked to you about a number of examples of passive cooling design, uh, you know, far different from the active cooling system that you may have in your

home or your apartment window. But we also have to just consider that many of humanities, the oldest civilizations, they resided in some pretty sweltering places. And while perhaps you know, such people's were less coddled by temperature control technology. Uh, you know, they still had to do what they could to keep things chill. So I ran across a very

insightful article. This was This was an in g conservation and management in two thousand and eight and it was a paper by um Hatamapur and A. Betty and it considers it concerns the town of the city of Bosher in southern Iran. This is a region where today you see more than of total annual power consumption going to power a c window units. But people have been living in this region for at least five thousand years. And in this paper the authors point out the various strategies

that were utilized to keep things cool. Some of these we've already discussed, but but just to you know, tie them to a specific location in a very long habited habitat region of the Earth. They pointed out that the buildings were constructed closely together but with spaces for circulation around each and they were built in the direction of seasonal fresh and cold winds. The lanes were narrow for the generation of circulation, and they employed ventilation shafts, balconies, terraces.

The separation of heat generating spaces such as kitchens. Uh, that's another key one, you know, I think about because I think a number of us have probably noted, especially during the summer, just how hot it gets in the kitchen when you're just doing something like cooking, you know, frozen pizza. You could keep things a lot cooler if you made sure that your your kitchen was somewhere else,

was located in an adjacent building. I mean, I think it's one of the appeals of grilling in the summer, like it's nice to be out in the in the nice weather while you're cooking, but also the thing that gets hot is not inside your house. Yeah, I think

it's a great point. Um Also balconies, coverings for direct sunshine, windows and walls, trees planted for shading, colored glasses in the windows, and wooden screens outside the windows, high roofed buildings, light roof colors, and low conductivity materials like gypsum for

shell walls. So so yeah, I found that, you know, again insightful considering that you know, this is a region that uh, people have been living in for at least five five thousand years, and throughout that five thousand history, most of it has been without the aid of a modern a C unit, but instead of having modern electrical air conditioning, they had this sort of army of other little ingenious design solutions to help keep things cool. Yeah,

every little advantage. And later in the episode we're going to talk about one really ingenious system that you see especially in ancient Persia. This this city was in ancient Persia. But maybe we should take a break now and then when we come back we can talk about ancient Egyptians

and ancient Romans. All right, we're back. So the ancient Egyptians were known to have employed a simple but really kind of ingenious system for for cooling their interior habitats, and that was they utilized wet mats of reeds that they hung in windows. Water evaporated from the wet mats, reducing air temperature in the process, and then a breeze is blowing through the window and uh and moving through

these mats, lowering the indoor temperature. This is the same principle that we see later in stuff like the swamp cooler, right that uses like evaporation in a window in order to do this, And that there are places where this is still a pretty common way of cooling your house. Actually just like hanging a wet towel and a window, maybe in conjunction with a fan. Yeah. I've also read that it has been common if you're if you have laundry that you're drying, you hang them in the window,

and then you're killing two birds with one stone. Yeah. Of course the ancient Romans got in on the act in large part thanks to you know, the aqueducts. Uh. They had many advances in plumbing, which we've covered on the show before and regards more to sewers, but it also meant the Romans had the ability to channel water through indoor pipes in certain homes, cooling them in the process. Yeah, it seems like they had a few strategies that were

based on water and evaporation of water. Uh. This next thing, it's hard to confirm that this story is true, but it's reported it in ancient sources, including the Latin text known as the Historia Augusta or the Augustine History, that the third century Roman emperor Ella Gabalus had snow carried down from the mountains to his palace so that it could be piled up in a in a mountain of snow in his orchard to help keep it cool in

the summer. Now, I do have to say that that this sounds like just an ethically Roman emperor thing to do. But but I do want to point out that in the seventy grade Inventions of the Ancient World, Brian and Fagin points out that in az Tech markets you would have found mountain ice brought down from the mountains and it would have just been available to purchase, at least if you were Aztec nobility. Uh, you could purchase it. But you know, that's got another like non Roman example

of of ice as a regional commodity. Oh yeah, and this does appear to be in smaller quantities, something that

did definitely go on in the Roman world. Now, as for having the snow brought down from the mountain to make a mountain of snow in his garden, you know, as with many allegations about the decadent behaviors of particular Roman emperors, I think sometimes it's hard to know if you're reading something that's based in fact, or if it's just libel against an unpopular figure or a historical adversary

of the author. I think there are a lot of Roman histories that are full of allegations like this that may or may not be true, right, and it also had it has an air of the unsensible to it, you know, like they're going to be extremely diminishing returns from trying to produce a pile of snow, uh you know, in your palace or wherever. Whereas having a small amount of ice, a small amount of snow, uh you know, certainly what whatever would be able to survive the journey

could be utilized in an intelligent manner. Potentially. Well, it does appear to be totally true that in smaller quantities, ice and snow transported down from the mountains were stored in special cold cellars and sold as a luxury item or just used as a luxury item in ancient Rome, though most of the other references I was reading two imported snow seemed to be about people eating it, not making a mountain out of it in their pleasure garden.

So some wealthy ancient Romans, including the Emperor Nero, are said to have eaten snow, sometimes allegedly sweetened with honey or with fruit juice or other flavors, of making snow cones. Yeah. This this has turned up in preliminary research for a potential episode on ice cream. Oh, we gotta do ice cream,

So yeah, we'll come back to that. But I've also seen references to snow being a luxury ittem for Romans just to be melted down and drunk like water because they believed it was very pure and cold or used to chill wine. So yeah, if you you know, you were rich and you could shell out for some fresh snow from somebody's seller that they had imported down from

the mountaintop, you know, go for it. Well, yeah, it would have been exotic, it would have So much of our appreciation of various beverages has to do with the story of it, right, And it's like a it's like a fine bottle of wine. It's the lore of the wine to a large extent that you're drinking and tasting

and contemplating. And if you're adding that with the you know, the properties of watching the snow melt in the in the glass, certainly in this era or in a later era, potentially having like a piece of an iceberg, you know, in your beverage. You know that kind of thing. It has bizzas. You can't blame them for being into the idea.

I think I was reading somewhere that the philosopher Seneca wrote with disdain about youths when they're snow eating, as if he was talking about always on their iPhones, always eating snow. Either way, carrying snow down a mountain I think, and dumping it in a pile in your house is not a super efficient way to stay cool overall, considering all the work needed to hauld the snow down. But I was wondering, well, would making a big pile of snow actually be effective at cooling your palace. I think

the answer is potentially yes. Having a large, massive snow or ice in a room can actually cool the room as the snow melts and then eventually evaporates those phase transitions like we were talking about before, or will suck energy out of the surrounding air, which will cool the air in the process. I'm not sure this would do much good just sitting there in an open air orchard.

But if you were to pair snow or ice with moving air, especially so maybe you've have people constantly flapping big fans at the pile of snow, especially in an indoor space, I think you could actually get significant cooling effects. Even if if you don't have air conditioning in your house, you can probably somewhat cool room several degrees by like setting up a fan and putting a bottle of frozen

water in front of it. This sounds kind of crude, but it actually does work to to circulate colder air, and in fact, there are even many large facilities these days, such as large office buildings, that have in recent years replace their traditional electric air conditioning systems with ice based cooling systems. I mean on on. On the surface, it can seem completely backwards, right, like you're stepping back into a more primal, sort of pre a c means of

cooling your place. But this is actually, in some cases a more energy efficient and more cost effective way to cool a large building. So how on earth would this work well? The ice based cooling system takes advantage of a principle known as load shifting, because energy cost from an electrical grid isn't just about the amount of energy

you use, it's about when you use it. So during the daytime on a hot summer, there are these periods of peak demand on power grids when too many people are all trying to draw lots of electricity at the same time to power their energy hungry building cooling needs, and it's going to result in what like rolling brownouts, right or yeah, I mean it's in any case, it's like it's putting more demand on the system, and so at these times of day there's more energy and efficiency

and higher costs instead. Now, many large buildings use this ice cooling method, which switches it's the building's maximum energy consumption for cooling purposes to night time off hours, and the buildings what they do is they have giant water tanks that can hold thousands of gallons of water, and at night, when electricity demands are low, when power is the cheapest, they use that power to freeze the water

into ice. Then in the daytime they use that ice that they made in the night time to chill air that is blown throughout the building's ventilation system. The ice melts gradually throughout the day turns into water. Then the melted water is frozen again the next night when power is cheap again. That is impressive. Yeah, I would, I would love to. I mean, of course, one of the issues isn't you know we made very well then in

buildings they use this and just was not aware. Yeah, we might not know, uh, And and it works because what water is actually an extremely powerful thermal energy storage medium. You can think of these giant tanks full of ice as kind of like a thermal battery which can be charged whenever energy and puts their cheapest and you charge it by freezing it. But of course these ice based methods need to be paired with like fans to circulate the chilled air. So we should mention general fan based

cooling effects, which also go way back into history. Yeah. I mean the simplest version of a fan, of course, as if you have any kind of like suitable fan shaped object that you can just flutter with your hand, big leaf or something. Yeah. And and I think that that's one of those things where it's at some point to humans figure that out just basic tool use. Some of the more one of the more elaborate, but still

simple and elegant in its simplicity. Uh. One of the devices that certainly comes to mind is the punka fans used in India uh from about five b C onward it seems. And these are large sales that are hung

from the ceiling and they're flapped manually to circulate air. Um. I imagine most of you have seen like some version of this, if not like an image of one used in India or in a depiction of say British occupied India, then then you also see them in other historical settings as well, you know, particularly hanging above like a din or table is of a prime example of what you might see one. Yeah, fans can be a fantastically useful and very energy efficient way to make a room feel cooler.

I mean, there's a reason you see fans all throughout the world and all throughout history. But the interesting thing about fans is I sometimes even forget this myself. Fans And let's well, so, if a fan is moving air in or out of a room, it can change the temperature in a room, right, if you're exchanging with an outside system. If you have like a fan, uh, you know, positioned in a window. Yeah, and the and the temperature in the outside is different from the inside, that can

actually change the temperature in the room. But fans inside a closed room do not change the temperature of the room. They don't actually cool the room. In fact, and in most cases they probably slightly increase the temperature in the room because you're running an electrical device from the room, and that's heating up somewhat, and so it's probably emitting some heat, so it's moving the air around, but it's

not actually making the or any cooler. So why are fans, even in a closed room, so good at cooling us down if they don't actually lower the temperature in the room. This is like a fun little if you want to pause and try to figure this out yourself, if you don't already know the answer. I don't know if it's too didactic, but I had fun trying to figure this

last night while I was thinking about it. It's because speeding up airflow increases the rate of evaporation from a body of liquid like water, and essentially you're a water bag. Your body is a bag of water, and your body, as we were talking about earlier, cools by evaporation of sweat. So in order for a fan to cool something, that thing actually probably needs to be wet. And I did an experiment like this in my house just last night, using a desk fan and a high accuracy instant read

kitchen thermometer. So I set the desk fan going on the kitchen counter, and I held the thermometer out in front of the fan. And even though standing in front of a fan makes us feel cooler, holding a thermometer in front of a fan does not really change aange the temperature that the thermometer registers. For me, the naked thermometer probe just hovered around room temperature. Even though I held it there for a long time. It didn't do anything. But then I wrapped the thermometer probe in a wet

paper towel. Now this naturally dropped the temperature of the thermometer already just because the water is cooler, right, and so the water contact drops it down. Then it's stabilized. And when you put the wet paper towel thermometer in

front of a fan, the temperature plummets. It drops down as the circulation created by the fast moving air of the fan speeds up the evaporation of water from that wet paper towel, And the faster the water evaporates, the colder the paper towel gets because it's stealing the energy from the rest of that water. This rapid air flow robbed the water of energy, made it cooler, and thus you get a nice, icy cold paper towel. So when you've got a fan running on you in a room.

Your body is that paper towel. You're that wet paper towel, accelerating evaporation off the top of your skin. Now the scenario you're again, you're using a desk fan, you using a rotary fan. Uh So it's interesting to dive into just you know, briefly the history of the rotary fan, and it seems that the earliest example of this goes all the way back to the Han dynasty in China.

Han dynasty engineer Ding Juan created a manually operated rotary fan with seven wheels around one a d c uh and then later on during the Tang dynasty of the eighth century, hydraulic power was apparently added to this innovation as a way of uh basically for use in blast furnaces for industrial you know, um air movement circulation. So flowing water powered the spinning of a fan to circulate air, yeah,

into a blast furnace. Now, but in Ding Juan's original idea, it would have required, uh, you know, a little human power, like somebody would have been turning a crank or or something in order to manually operate all of these rotary fans. Uh. So Juan's initial invention here was reported in the text Mental Miscellaneous Records of the Western Capital and excavations from a former Han tomb in seems to show the necessary

parts to carry this out. So the seven fans, so there have been ten feet or three meters in diameter, were connected so that one person could power them all. Uh. And this is, of course, UH is another more elaborate means of just circulating airflow, which can can make all the difference in a stuffy room. Right. Uh. Now, it's not evaporative cooling, though I've seen at least one wiki

lit listing that says Ding Juan had an evaporative cooling system. Uh. Decided sources that I ran across on those wikis did not support it. Uh, that they were just talking about what I'm talking about, just air circulation. Uh. So there's no evaporation beyond what's happening on your skin. Correct. And I didn't see it mentioned in um Ian Inkster's The

History of Technology, which discusses this. But of course it's entirely within the room of possibility that he can bind a fan system with something like the Egyptian read Matt scenario that we discussed earlier. Having some sort of you know, wet fabric in front of it, but I could not find direct reference to that myself. By the way, Ding

Juan also allegedly invented something like a zoo trope. According to Lance Day and Ian McNeil in Biographical Dictionary of the History of Technology, it was a quote zootrope lamp which had a thin canopy bearing veins at the top that were caused to rotate by an ascending current of warm air from the lamp. The canopy bore images which if the canopy were rotated fast enough, gave the impression of movement. Wow, it's like a it's like a fan

for your eyes. Yeah. Uh, you know. It also shows that like this is an individual who was clearly interested in, uh, you know, the combination of of rotary machinery and the movements of air. Uh. And also then just throughout Chinese, ancient Chinese technology, you also see some other interesting advancements in refrigeration, which maybe we'll come back to later on. All right, we're gonna take a quick break, but when we come back, we shall return to Persia. All right,

we're back. One genre of ancient cooling technology for buildings is i think a really deeply ingenious solution, and we find some great examples in ancient and medieval Persia, which would be in modern day Iran. So this is going to be the idea of wind catchers and a paired technology known as connots. And we can start with a simple version of the wind catcher that's just focused on

air flow. So I want you to picture a building with towers reaching up above the roof on each side, and each of these towers has four ports that can be opened and closed, and each of these towers is hollow and it connects down to the occupied space within

the building. So if the wind is blowing from the west, you would open the west facing ports on the west side of the building to accept the incoming air flow into the towers, and then on the other side, you would open only the east facing ports on the east side of the building, so that would be the ports

facing away from the wind. Now, due to a couple of quirks of fluid dynamics, if you have a shaft like this that's only open on the side facing away from the wind, air will naturally be pulled up from inside the house through that shaft to flow out in the same direction as the prevailing wind. I've seen this attributed to both the Quanda effect and the Bernoulli effect.

I have to admit my fluid dynamics knowledge is not sharp enough to evaluate whether these characterizations are correct, but at least several have definitely attributed it to what's known as the Kwanda effect, which just describes a property of

air flow and certain scenarios. But anyway, if you've got towers on each side of a building, with towers on one side accepting the prevailing wind and and routing it down into the house, and then towers on the other side with a negative pressure allowing wind to be sucked up from the inside to blow out with the prevailing wind, it creates a complete circuit of air flow where air is sucked down into the house on one side and sucked up out of the house on the other side.

And you can use this method to help drive hot air out through the roof for the highest level of the house, taking advantage of this chimney principle we discussed earlier in the episode. Now, of course, at this stage what I've described so far, this would still just be circulation of hot air from outside. Right now, we know that even if airflow doesn't actually cool a room, it can help cool your body if just you you keep the air moving because it replaces the air around your

skin and helps you evaporate faster. But you can also greatly improve on the wind catcher design and generate a true space cooling effect by pairing it with an underground reservoir or subterranean water channel called a cannot. Oh wow, So this it's it's almost like we're getting into the like the creation of an artificial cave system kind of

to cool the air. So cannot is a chamber of underground water resting or flowing deep in the earth, surrounded by dense layers of rocks, so the water stays cool even on the hottest days, and it can be used for several things. I think from what I've seen, it seems like it's most often used to sort of help channel water down underground from from higher level water tables up in higher elevations so that the water can be brought down for irrigation in lower lying areas. But in

any case, it's underground water. It's a channel of underground water, and the water stays very cool because it's deep underground, so like even when the sun heats up the top of the Earth's surface, it's not heating up that deep bedrock below. Now picture this. You've got one shaft leading down from the surface down into the cannot that looks like it works like an intake shaft, and this can be outside the house, drawing in dry air from the desert.

And then there's another shaft leading up from the same cannot into the house, into the inside of the house or whatever space you want to cool. And this is paired with an outflow wind catcher facing away from the wind, which naturally sucks air up from the inside of the house.

So the circuit created here pulls air from the outside down through the first shaft through the cannot to flow over and around the cold water down there in the deep earth, and then up the second shaft into the house, and the dry air passing through the cold humid environment of the cannot becomes much cooler as it travels, and the result is that you have cold air pulled up into the house and flowing, which I think it's just brilliant. Yeah, I mean, it's a it's it's one of these systems

that is um it's it. It's at once kind of simple when you when you have it all explained to you, but it is especially considering, you know, ancient buildings we were talking about it, but pretty elaborate system here. And you know, I've actually, I don't know if you ran across any modern uses of this, but I read a couple of references to UH designs for like large sports facilities that utilize at least some version of this to try and keep air circulating through um, you know, through

through the uh the sports arena. Oh okay, well, because right if you've got like a sports arena, it sounds crazy to try to like air condition that with like with just electric air condition so just the sheer scale if the building might require you know, a more you know, less you know, electricity dependent method, and perhaps I don't know, it seems like the kind of thing that that could potentially be utilized in large industrial spaces as well, But

I didn't run across any examples of that. Well, I don't know about the scalability of this kind of technology, but maybe, yeah, I I just don't know, but I do know they're they're ancient examples where things like this were used pretty effectively to keep some sellers and basements and and dwellings very very cool, and even to the point where they could be used to store ice in

hot places like in Persia. Now we mentioned India earlier on the subject of fans uh, but I want to return to India once more, particularly to the use of step wells and also step ponds. So as Morna Livingstone and Milo Beach point out in the book Steps to Water, the Ancient step Wells of India quote, the alternating absence and abundance of water is crucial to Indian life, and the step wells and stepped ponds generated by the use

of water are especially imaginative. So basically what they're saying is that much of the subcontinent is subject to intense months, soon seasons and intense dry spells, and during the dry spells people need communal access to water UH. And during the wet spells, the places they would go for unal access, of course they're going to be likely to flood and UH and greatly. And so this communal UH connection with

water is an important aspect of Indian life. A prime example of this is it would be there the stepped access that you see to the Ganges River in urban areas U and think everyone's probably seen images of that, you know, especially with religious rights and so forth taking place close to the water. But a far less famous, less visited and even less preserved example would be the

step ponds and the step wells. Uh. These are beautiful, by the way, if you've never looked up images of them, it is some of the most just sort of like eye rending architecture I've ever seen, and it's actually not all that complicated, is just like geometrically dazzling. Yeah. I like to think of it this way. A mountain is to a canyon as a ziggurat or a Mesoamerican pyramid

is to an Indian step. Well, it looks like there's a hole in the ground and someone like took a zigaratt out of it and left a ziggarat shape in the earth descending into the earth inverted zigaratte. Yeah. So like imagine these many lattices or steps going down, uh to a ridiculous degree. Yeah. Yeah, they're essentially deep holes in the earth, dug down to the water table and then built out. So there's you know, generally a tear there's terrorist access with stairs leading down to it um.

And one of the points that the author's made in this book is that while generally you think of like a journey into the deep earth, you know, like it would be it would be claustrophobic, it would be frightening. But that's not the sense you get when you look at the photographs of stepwells, like it is. It is open, it is inviting, it is It's not a sense of the earth closing around you, but instead one of opening

up like a flower. They're yeah, they're beautiful, and why do I get kind of an m C. S sure sense from them? Yeah, there is kind that I think part of it is that sort of inversion scenario you get. It is like an inverted ziggarat when you look at it, and yet you're you're you're sort of climbing up, but you're climbing down. Um. So. The main distinction though, between step ponds and step wells, according to Livingston and Beach, is that step ponds were used for bathing and step

wells were use more for daily water use. Now, many of these have fallen into disrepair or have been abandoned in in recent years, in part because of falling water table. You know, which renders them dry and useless, but also due to the period of British colonial rule in which the British condemned them as being you know, potential disease

of vectors and so forth. But there has been increased interest in them in recent years to preserve their cultural importance, but also, you know, to preserve them as potential water sources and a changing climate. Now, obviously these things are architecturally beautiful and you can see their importance as a commune a water source, but how do they relate to

the idea of air conditioning or cooling of spaces. Well, you know, some of them are more out in the open, you know, get kind of a sense of almost like a you know, it's like a you could easily mistake them for some sort of ornate swimming pool sort of you know, construction. But others are other step wells are part of temple palace or other urban complexes. So they're

part of this other, this, this larger structure. And here you know, they were, of course a means of access in cool water, which in and of itself is a cooling resource. Livingstone and Beach point out that splashing one's face with cool water is a standard Indian means of coping with the heat. A step well affords this cooling method. It also affords one the ability to enjoy the shade via the terraces. Or if you've got like hot dry air,

you could also have evaporative cooling there. Yeah. Yeah, Also you can rest against the cool stone. That was That was one example they brought up that I didn't think of in the early portion of the podcast. Is it It's You can also just like if you find some cool rock to lay upon, that can be used as a very primitive form of air conditioning. But they have they have a wonderful quote in the book about uh

evaporative cooling via the step well quote. In dry weather, the step wells pool provides some evaporative cooling, but in high humidity, cooling happens only through contact with water. Unlike a running fountain, still water and step wells evaporates little. A moisture saturated layer forms over the water surface, and if it is not ruffled by a breeze or broken by splashing, it acts as a vapor barrier. Thus, in hot humid weather, the body does not get cooled as

quickly in a step well as it does in air conditioning. Indeed, step well air feels breathlessly still. Okay, so if it's humid outside and the air isn't moving, the step well isn't gonna have much of a cooling effect. But if you had like hot, dry air and a breeze blowing through moving the air along the surface of the step all, if it was moved by humans somehow, then it sounds like you're in business right. However, the humidity is gonna also serve to conserve the water, so it has that

going forth at any rate. These are again we do encourage you to do a Google image search on uh Indian step wells and take a look at something. There's also some wonderful like top ten step well images. Uh there. It makes for some just wonderful architectural photography. We'd love to also hear from anyone who has had the chance to visit. These are some of the resources I was I was looking at pointed out that you know these

are these have at least in recent years. I don't know if it's changed, but in the past it's been a situation where these places, despite just how beautiful they are, they haven't been a sought out by tourists uh and and and sightseers in India. But perhaps that is changing again as as more conservation has been directed at them and perhaps just more just sort of appreciation for what they are. Yeah, all right, well, I think that probably

does it for today. But the next episode, in part two of our exploration of air conditioning, we're gonna get more into the modern air conditioner that's based on refrigeration chemistry. Right, but we've hopefully we've we've laid the groundwork for those innovations, Like like we've shown you what was possible in the age before these new technological advancements, and it's pretty impressive, you know. I think I think a lot of us are going to be surprised because we have we are

so coddled by modern air conditioning. We think that the different that there's basically a distinction between having a C and just sweltering, and we don't realize that there are all these uh these smaller things that can and have been done to help ensure a less sweltering environment. Yeah. So so many people now live in an a C tamed world. If the a C is cut off, they don't have all of the normal coping mechanisms that you would have to to get around that heat. It's a

fundamental softening of our defenses against the evil sun. We will return to air conditioning in the next episode of Invention. In the meantime, check out past episodes at invention pod dot com and indeed let us know you know what, what is your relationship with air conditioning and particularly what is your relationship with some of these these alternative methods of dealing with the heat. Do you still employ some

of them today? Uh? Perhaps you have. You know, older members of your family have told you about how they used to do things before air conditioning. We would love to hear about any of that. Huge thanks, as always to our excellent audio producer Seth Nicholas Johnson. If you would like to get in touch with us to send feedback on this episode or any other, to suggest a topic for the future, to join the Committee to Extinguish the Sun, or just to say hello, you can email

us at contact at invention pod dot com. Invention is production of iHeart Radio. For more podcasts from my heart Radio because the iHeart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.