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Short Stuff: Yakhchāls - Ancient Fridges · Stuff You Should Know

• 0:04
  Speaker 1: Hey, and welcome to the Short Stuff. I'm Josh, and
• 0:06
  Speaker 1: there's Chuck Jerry sitting here free Dave, and so this
• 0:09
  Speaker 1: is short stuff. How do you say this again?
• 0:12
  Speaker 2: Edition, Yeah, I'm gonna say it's pronounces spelled y ak
• 0:17
  Speaker 2: h you know, as most words are h A L.
• 0:22
  Speaker 2: I'm gonna say yakuls.
• 0:25
  Speaker 1: I'm going with the straight ahead yakh chaws. All right, Okay,
• 0:30
  Speaker 1: so you say your way throughout. I'll say it my way,
• 0:33
  Speaker 1: and I'm sure all inevitably unconsciously start saying it your way.
• 0:37
  Speaker 2: We'll see. But what we're talking about is the promise
• 0:40
  Speaker 2: from our refrigeration episode. A little bit more on these
• 0:44
  Speaker 2: ancient basically ancient refrigerators or cooling systems. They were found
• 0:49
  Speaker 2: across ancient Persia at least as old as four hundred BC.
• 0:54
  Speaker 2: This is modern day Iran, and this is these are
• 0:57
  Speaker 2: places where, I believe it or not, the climate enables
• 1:01
  Speaker 2: freezing of ice when you would not think you should
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  Speaker 2: be able to freeze ice.
• 1:07
  Speaker 1: Yeah, it's pretty amazing and apparently still today in Iran,
• 1:12
  Speaker 1: Afghanistan and to Jikistan, to jeek Stan. Yeah, I said
• 1:16
  Speaker 1: it right. The first time they called the refrigerators yak Chile's,
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  Speaker 1: which is how I would say it if I were
• 1:22
  Speaker 1: in Iran. But that's the name for the fridge, which
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  Speaker 1: means that at some point someone in Iran has gone
• 1:27
  Speaker 1: into a store and said, you got a smeg yak chaw?
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  Speaker 2: Yeah, exactly. And these have been the fascination of like
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  Speaker 2: everyone from engineers to historians to physicists over the years
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  Speaker 2: because they're just so kind of confusing and how they
• 1:46
  Speaker 2: actually work. And I'm still not entirely sure how it works.
• 1:50
  Speaker 2: It seems to be a little magic involved. One thing
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  Speaker 2: I know goes a long way toward keeping this ice.
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  Speaker 2: And we got to say some of this ice is
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  Speaker 2: mined from the mountains, brought down and preserved. Some is
• 2:01
  Speaker 2: made on site. We'll get to that, but one big
• 2:04
  Speaker 2: factor is the insulation of the structure itself, which is
• 2:08
  Speaker 2: made from a mortar called serrouge.
• 2:14
  Speaker 1: Was that how you're saying it?
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  Speaker 2: Sand, clay, egg whites, lime, goat, hair and ash quite
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  Speaker 2: a mixture.
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  Speaker 1: Some of these were several meters thick. Some of these
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  Speaker 1: yak chaws were. There was a study. We got some
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  Speaker 1: of this information from the engineering for Max Fordham and
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  Speaker 1: they did an analysis from twenty eighteen of yak Child's
• 2:35
  Speaker 1: and just how effective they might have been. And they
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  Speaker 1: found that the walls of a yak chaw had the
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  Speaker 1: same insulative properties as a wall of concrete three inches
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  Speaker 1: thick surrounded by a one foot thick wrapping of styrofoam insulation.
• 2:53
  Speaker 1: That's how effective these things were.
• 2:55
  Speaker 2: Sand, clay, egg whites, lime, and goat hair and ash.
• 2:59
  Speaker 1: I was gonna say, like the secret egg whites, but
• 3:02
  Speaker 1: who knows you throw goat hair in there, and yeah,
• 3:06
  Speaker 1: who knows what the secret? I think the secret is
• 3:08
  Speaker 1: the whole thing together, the whole say rouge mysture?
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  Speaker 2: Yeah, probably so so I mentioned that sometimes the ice
• 3:17
  Speaker 2: was brought in from the mountains and kept there throughout
• 3:19
  Speaker 2: the year. But usually what would happen is is they
• 3:23
  Speaker 2: would make ice, They would bring in water. They would
• 3:26
  Speaker 2: divert water from an aqueduct through these underground water channels
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  Speaker 2: called cannots, and they would channel them to the north
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  Speaker 2: side of this wall. It's another thing we haven't mentioned
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  Speaker 2: yet is they have these very very high walls that
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  Speaker 2: act as shade for these channels to keep you know,
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  Speaker 2: the wind off of it, because stuff isn't going to
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  Speaker 2: freeze as fast if it's moving, so to keep the
• 3:51
  Speaker 2: water still and to keep it cooler away from that sun.
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  Speaker 1: Yeah, And so the channel has a little diversion into
• 4:00
  Speaker 1: a trench or a pit or like a very shallow
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  Speaker 1: like rectangular pond usually, and it they'll divert water in
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  Speaker 1: there to fill it up, and then they let it
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  Speaker 1: freeze overnight. Over the course of a few nights, it'll
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  Speaker 1: continue to freeze and freeze and freeze in layers. And
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  Speaker 1: the what they're taking advantage of, you know, like when
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  Speaker 1: it snows and then the temperatures heat up and all
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  Speaker 1: the snow melts, but there's a little pile of snow
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  Speaker 1: like in a shaded corner of your yard that never
• 4:29
  Speaker 1: gets direct sunlight. Yeah, and it just takes forever to melt.
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  Speaker 1: There can be advantage of the same thing. They're building
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  Speaker 1: that big old that big old wall to keep it
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  Speaker 1: shaded and to just let this ice grow and grow
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  Speaker 1: and grow. And then once it reaches I think fifty centimeters,
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  Speaker 1: which is like about a half a meter thick, then
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  Speaker 1: they'll cut it into blocks and they put it in
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  Speaker 1: the yac shell and they store it through summer. Like
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  Speaker 1: this stuff will stay frozen for an entire summer. So
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  Speaker 1: in in that sense, these yak chails are built to
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  Speaker 1: store cold throughout the course of a year, even when
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  Speaker 1: the summer comes around still cold.
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  Speaker 2: Yeah. Another way that helps us out is that dome shape.
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  Speaker 2: It's not domed because they like domes, even though domes
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  Speaker 2: are nice. It's conical because that optimizes what's called the
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  Speaker 2: solar chimney effect. Is that's when you create a convection current,
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  Speaker 2: letting that heat go up, up, up and out through
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  Speaker 2: these openings at the top and bringing in that cool
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  Speaker 2: air from the bottom.
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  Speaker 1: They also have wind catchers that they call bad geers,
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  Speaker 1: and they actually take win and direct it downward into
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  Speaker 1: the yakchaw dome. And so the air that hits it
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  Speaker 1: is cooled by that ice, and the air that's not
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  Speaker 1: cool by it, or cooled enough, like you said, that
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  Speaker 1: chimney effect takes it up along the curve sides toward
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  Speaker 1: the hole in the top, and it says, see you later,
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  Speaker 1: don't come back.
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  Speaker 2: That's right, And that feels like a good time for
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  Speaker 2: a break, and we'll come back and talk about what
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  Speaker 2: the heck they're doing with all this ice. This all right,
• 6:27
  Speaker 2: So they're making ice, they're preserving ice. What are they
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  Speaker 2: doing with all this ice? One of the things they're
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  Speaker 2: doing is using it as a refrigerator. You know, they'll
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  Speaker 2: store food in there that they don't want to go bad,
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  Speaker 2: and just using it as a as a cold house.
• 6:43
  Speaker 2: They will also just use the ice to eat in
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  Speaker 2: a treat. They have something called Feluda over there, to
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  Speaker 2: Persian traditional dessert has thin vermicelli noodles made from cornstarch,
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  Speaker 2: and then you mix that up with a little semi
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  Speaker 2: frozen sirr of sugar and rose water, and then serve
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  Speaker 2: it up with a little lime juice and maybe some
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  Speaker 2: ground pistachios. And it's like a little Persian icy.
• 7:09
  Speaker 1: That has to be better than it sounds, don't you think?
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  Speaker 2: Oh I think it sounds great.
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  Speaker 1: I think the pistachos are where of throwing me off.
• 7:16
  Speaker 2: Oh yeah, you don't like pistashios.
• 7:18
  Speaker 1: Or I do like pisachos. It just they don't seem
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  Speaker 1: to go with the rest of the ingreen eent. But
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  Speaker 1: like I said, I'm sure it's delicious. I mean, it's
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  Speaker 1: a traditional Persian dessert. It's got staying power. So yeah,
• 7:29
  Speaker 1: who am I to question for luda exactly?
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  Speaker 2: I bet it's delicious.
• 7:34
  Speaker 1: One of the cool things about this is that yak
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  Speaker 1: charles I mean, and there's some still around. I think
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  Speaker 1: there's one in Kerman, Iran that's about the size of
• 7:45
  Speaker 1: a five story building. So you would think, of course,
• 7:48
  Speaker 1: obviously this was reserve for royalty. You would be dead wrong,
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  Speaker 1: because not only were yakchels open and available to the public,
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  Speaker 1: there are some that people just built for their houses
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  Speaker 1: that were a private use of as well.
• 8:00
  Speaker 2: Yeah, for sure, they would make those delicious falluda. They
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  Speaker 2: would make surbets and preserve them and then nuts, fruit
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  Speaker 2: and ice and they would put them on a donkey
• 8:11
  Speaker 2: and go sell them at market and stuff like that.
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  Speaker 2: They would sell ice directly from those places sometimes. And
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  Speaker 2: you know, one of the things they're also taking advantage
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  Speaker 2: of is the greenhouse effect. You know, the earth is
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  Speaker 2: going to stay fairly warm at night because of the
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  Speaker 2: greenhouse effect trapping those gases in the atmosphere. But if
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  Speaker 2: it's low humidity and if it's a really clear night,
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  Speaker 2: that effect is going to be weaker and that heat
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  Speaker 2: can dissipate and disappear more readily. And so that's when
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  Speaker 2: they discovered, like, hey, we can make these little thin
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  Speaker 2: layers of ice and kind of build, you know, day
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  Speaker 2: by day, night by night on these clear, low humidity nights,
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  Speaker 2: eventually to get you know, some pretty significant ice.
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  Speaker 1: And once they figure that out, someone said, go get
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  Speaker 1: the donkey. Exactly, it's time to sell some Subert and
• 9:00
  Speaker 1: harvesome goat hair. One other thing I saw in that
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  Speaker 1: Max Fordham analysis, they figured out that they could make
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  Speaker 1: about what would be equivalent to three million ice cubes
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  Speaker 1: a season.
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  Speaker 2: Wow.
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  Speaker 1: Yeah, which is a lot. But they were like, you'd
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  Speaker 1: think it'd be more, and I was like, it seems
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  Speaker 1: pretty good to me, especially in four hundred BC.
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  Speaker 2: You know, it depends on how big those cubes were.
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  Speaker 2: Were they big fancy cocktail cubes. That's a lot more
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  Speaker 2: ice than a ice nugget.
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  Speaker 1: That's right, You're absolutely right. I expect that they're probably
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  Speaker 1: all donkey head size. So three million donkey head size
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  Speaker 1: ice cubes, that's big. Think about the poor donkey that
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  Speaker 1: had to cart those around. I know, no fun, you
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  Speaker 1: got anything else?
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  Speaker 2: Yeah, I mean these went away obviously because of modern
• 9:46
  Speaker 2: refrigeration came on the scene. And also one thing that
• 9:50
  Speaker 2: was happening was they were making this ice kind of
• 9:51
  Speaker 2: out in the open, and a lot of it would
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  Speaker 2: get contaminated with dust and it wasn't like the healthiest
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  Speaker 2: ice in the world. And so that combined with modern
• 10:00
  Speaker 2: refrigeration coming along, they're like, maybe we should just not
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  Speaker 2: have these much anymore. But like you mentioned, there is
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  Speaker 2: one still around, at least in Kerman, and there are
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  Speaker 2: groups there that are trying to preserve this way of
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  Speaker 2: life and at least keep it, you know, not like
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  Speaker 2: a chief refrigerating method, but like, hey, we can't lose
• 10:20
  Speaker 2: our culture, and so let's work to take some of
• 10:23
  Speaker 2: these old ones and restore them at least, even if
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  Speaker 2: only for like museum and touring purposes.
• 10:28
  Speaker 1: For sure, but also there's a lot to learn from them,
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  Speaker 1: especially when we're trying to advance like passive cooling and
• 10:33
  Speaker 1: other things that require less energy to cool things down.
• 10:37
  Speaker 1: Yak Chaal's are something to turn to and say how
• 10:40
  Speaker 1: do we do this? And someone says, go get the
• 10:43
  Speaker 1: goat here.
• 10:44
  Speaker 2: That's right, we'll get some egg whites too. No one
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  Speaker 2: likes this.
• 10:48
  Speaker 1: What do we do with all these yokes? Yeah, well,
• 10:51
  Speaker 1: I think that's it for short stuff, right, Chuck?
• 10:54
  Speaker 2: I think so?
• 10:55
  Speaker 1: Well? I mean short stuff is that.
• 11:00
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