This isn’t just mildly interesting. We should be considering methods of air cooling that do not use any carbon in order to avoid aircon usage becoming a contributor to the climate problem as things get hotter and hotter.
I agree with you that we should be exploring alternatives, but aircon is extremely energy efficient for how much thermal energy it moves (reaching 400% efficiency in some cases) . The problem isn’t aircon itself, but what is being used to power it (coal/natural gas power plants)
In fact the technology behind aircon can be expanded into a heat pump to both heat and cool, being more efficient than electro-resistive or gas heating. There’s even water heaters that will actually cool the area they’re in and use the heat they gather from the space to heat the water.
Technology Connections has a great series of videos that go in depth on both heat pumps and aircon.
Yeah, “air conditioning powered by solar/wind/hydro” can feel like it’s one big Rube Goldberg machine to make air cool, but the reality is that it comes together to make something that can scale really easily. I can’t imagine coming up with a design like what’s in OP for an apartment complex or condo building.
Source: just made it up, but also a Technology Connections fan. All that’s to say, feel free to correct me with a little data
They actively use this design in large buildings (with a modern twist). Its known as a chilled water system: https://hvactrainingshop.com/how-a-chilled-water-system-works/
Or you have ones that do not run at all during the day, and only chill/freeze the water at night on excess power/cheap power: https://www.buildinggreen.com/news-article/making-ice-night-cool-buildings
The second system I linked would then let the ice slow melt over the day as its way of actively chilling air passing through its exchanger.
These systems work by chilling water instead of air, which has a much higher heat capacity. Meaning, it can accept much more thermal energy per unit mass before raising its temperature by 1 kelvin. You are able to build a single, very well designed, and efficient refridgeration unit that can provide HVAC services to up to multiple high rise buildings. This reduces waste and reduces the usage of coolant/refridgerant.
This system can be reversed in the winter (heating the water instead of chilling) with geothermal heat, solar heat, or if no “green” options are readily available, natural gas direct fire heat can be extremely efficient compared to electric coil
400% efficiency is good, but it’s not better than the ∞% efficiency you get from something that doesn’t require fuel input to begin with. (I’m pretty sure the Technology Connections guy would agree on that point.)
If nothing else, think of it this way: even if you still want to use air conditioning to make sure you get all the way down to comfortable room temperature or whatever your target is (which a Qanat, although able to achieve a >15°C ΔT, might or might not be able to do reliably), it’ll still give you a big head start and greatly reduce the amount of energy needed. It’s a lot like using a ground-source heat pump instead of an air-source one. What’s not to like‽
Sorry my point wasn’t that we shouldn’t explore other options to use instead of/in tandem with A/C. I was entirely pointing out that the use of an AC/heatpump is by itself, in absence of the context of what is used to power it, a non issue as its one of the most efficient electric heating/cooling technologies we have.
Wind catchers could be, and likely are a great technology to adapt for wider use, though I can’t speak to that, I’m not an HVAC engineer.
Sorry, my notifications have been messed up because of the lemmy.world issues! Some other people have already answered but I’ll still reply :)
A heat pump’s efficiency is measured differently than that of a gas furnace.
The actual unit for heat pumps is the Coefficient of Performance (CoP). This measures the power input (electricity) VS the power output (heat). A “400% efficiency” as I put it, is a CoP of 4, meaning that for every watt of power used, 4 watts of heat energy are moved. As some other people pointed out, depending on the quality and technology of the heat pump and the interior/exterior temperature, the actual range of a heat pump is a CoP of anywhere from 2-5.5 (the theoretical, perfect maximum is 8.8). The efficiency of the heat pump does dip as the temperature of the region it’s pulling heat energy from lowers, there’s less energy available to move, so it has to work harder. This is why heat pumps in regions with especially cold winters have what’s usually called “emergency heat” which brings us to…
Electrical heating. This works by pushing electricity through a wire to heat it up. Directly turning electricity into heat. Electrical heating always has a CoP of 1 (terms and conditions apply). For each watt of electrical power consumed, 1 Watt of heat energy is produced.
Finally we have gas heating, which is still the only option for some areas for various reasons. Gas heating efficiency is not measured with CoP but instead with Annual Fuel Utilization Efficiency, simply a number that represents what % of the fuel burned is actually turned into useful heat energy. I’m finding AFUE ranges of 76-97% as a general range for modern furnaces. If a furnace has an AFUE of 90%, that means that when it burns an amount of fuel representing 100 units of heat potential (I’m not using a unit, BTUs confuse and terrify me) then 90 of those units will be turned into usable heat, and 10 of them will be waste, whether that is heat that leaves via the chimney or is simply unburnt fuel.
TLDR: 400% means 4x more energy is moved than is used, I apologize for the wordiness, I find this stuff rather interesting
What the other guy said. It’s down to the fact that you aren’t actually heating/cooling down a room, you’re just moving the heat already there around. E.g. in winter, instead of producing your own heat with electricity, which is 100% efficient, you take heat from the outside and put it inside, using a lot less energy in the process than if you were to create the heat inside of your home.
Though I’m not sure if it’s that efficient, I think I heard it’s more around the 150-200% mark, but I’m not sure.
This would be a great idea if you want everyone in that building to file humidity complaints every single day. Air conditioners work by using mechanical work (compressor) to exploit evaporation in order to pull heat from one location to another and exhaust it away, in turn cooling the first location (this could be air, water, etc.)
This system works by using ground temp water as a heatsink to suck heat out of the air passing over it. When it does this, it humidifies the air. In the desert…who cares? In an office building…who cares? Every single worker who is stuck there all day
If you’re saying we need better systems than the AC unit you grew up with, fear not! Many office buildings have been moving away from it (same with other large venues) they use a chilled water system. They use the best of both these systems to get WAY more performance out of way less wattage. You only need a fraction of the cooling power with a chilled water system because the water can absorb much more heat per unit mass than air and can be sized to never run during the day, but only at night when the grid is least in use
AC unit you grew up with
Lmao grew up with? Most of us have never used AC at all in europe. Here in the UK no homes have AC. The issue is that people are installing it now because of climate change and the result is massively higher energy use.
Not necessarily in your house. I’m talking about the design of the units from when you were a child (Many public buildings in the EU have AC regardless of houses not having it). AC was invented in 1901, and has come a very long way since then, and we have begun combining it with old principles to extract the best of both solutions
Combining modern refrigeration/cooling techniques with well designed passive systems that exploit material properties (Heat capacities, transfer coefficients, etc.) to their advantage is the future of HVAC. It started with CFCs and knowing we could exploit their boiling point with mechanical force to chill air beyond the outside air temperature. Who knows where science and engineering may take us next!
People in the UK are installing air cons, because most houses are very bad and have no insulation.
https://www.youtube.com/watch?v=5zW9_ztTiw8 Have you seen this? Seems like the next big thing in AC is just around the corner :-)
I had a crazy thought. What if you used depressurization to cool interiors?
Not as in depressurize the room and potentially kill the people inside, but in a way similar to soundproofing where you create an airtight gap in your walls, depressurize it to create a partial vacuum and effectively restrict both heat and sound transfer. That way it would be much easier to control internal temperature.
The only two problems I can see with it is expense (pumping air out of the gaps between your walls could be pricey), and the potential of explosive repressurization if something were to break the wall.
And how do you get fresh air in? Also the problem of heat transfer is never by gaps in the walls, at least not for buildings in western and central Europe. The problem is heat conduction through the window panes. And that is with isolated windows already. Also it is impossible to get a brick wall air tight. Leave alone you create a great environment for water to leak in and damage everything.
A building needs to be able to “breathe” in order to get rid of the humidity that is generated inside.
A modern home ACs can only cool about 20f below the outside temperature. 50c to 35c is 27 degrees so that’s pretty damn good for a fancy unpowered swamp cooler
Yeah, the thing is the “unpowered” part. Look how much energy an AC chugs to achieve that cooling. This tower uses wind power to do it’s thing.
well technically it is powered, just directly by wind and water kinetic energy, probably(?) much more efficiently than if it had been converted to electricity first
AC really doesn’t consume that much if designed and sized properly. It’s nothing like the energy consumption of standard heating. The problem is all these people going out and buying the cheapest floor unit or undersized window unit they can find, then the wheezing thing just sits there chugging 100% of the time because it can’t keep up with their space. That’s super wasteful.
What’s your source for this? It routinely gets over 100 here and buildings aren’t 80 degrees inside.
We’re talking celsius, I hope for your sake it doesn’t routinely get to 100 C where you are. :)
Edit: The user actually said 20 F, I got confused by the mix of units. “50c to 35c is 27 degrees” didn’t make sense to me, but I figured I’d let it slide. No idea what’s going on here. :)
20 degrees is just a rule of thumb most ACs have a specific temperature change they’re designed to do. You can go past it, that’s just what the intented to do and it might not work as well or be able to do it. Fwiw I’d always heard 30 degrees farenheight for most window units. Had an hvac guy explain it to me years ago but fucked if I remember how it works
E: not sure why I’m getting downvotes this is like a very common thing. Google it https://frederickair.com/home-comfort/reduce-the-stress-on-your-ac-with-the-20-degree-rule/
I wonder how he got his number, it makes no sense.
EDIT: oh, he just randomly mixed °C and °F, because why not…
What do you mean modern AC can only cool by 20F?
I’m in Florida and it’s routinely 95-98F outside. My AC is set to 65F.
Did you mean 20C? Either way, that’s also false. AC units are limited to their rating and BTU. Many may not cool below 60F, but there’s no delta limit.
Heat pump doesn’t do that for us. We set it at 78-79f in the summer and it feels cool enough & keeps the house from molding.
Evaporative systems like the one pictured only work in the desert though. So if you have lots of water, it’s humid and you can’t use evaporation to cool, but in places you can use evaporative cooling, water is scarce. It’s still very cool tech, and everywhere can benefit from more intentional design of buildings.
ok, but the cost of building a quanat is still pretty high and is not trivial to achieve.
Can’t have water flowing everywhere in a country for this to work.
Most countries in the world quite literally have water flowing everywhere already.
You’ve got a lot of great replies on how you’re a wrong. But it is even simpler - your freezer works the same way as air con. And it’s at -18°C even if your room is at +35°. That’s all you need to know about air cons and their capabilities.
10 degrees is incredible though.
These days in Yazd the average warmest temperature in July is 40 degrees, so if what you’re saying is correct they’d be able to cool it down to a liveable 30 degrees even in the warmest part of the day. And at night temperatures still dip to 26, so the indoors temperature probably wouldn’t quite reach 40 even without this system. So it might make the difference between 40 degrees outdoors and high 20s indoors, which is fantastic.
Would be interesting to know if average temperatures got up to 40 in the summer around the time they were built as well, or if average temperatures in the region have been rising.
I do wonder what the humidity is. The drawing shows that the new air is mixed with air coming from the water canals below which I assume is very humid.
Looks like its essentially a swamp cooler.
So I wonder how the 30 with humidity feels compared to 40 without.
Im now at a 32 but with the current humidity it feels like fucking 38!
You can literally go there and witness these for yourself. It works. People live in Yazd right now in these old buildings. Newer constructions have air conditioning because building huge thermal mass retaining walls out of mud bricks is expensive. They keep ice all winter in buildings there from a thousand years ago cooled like this.
Iran’s traditional desert architecture masterfully navigates extreme temperatures through a combination of smart design and local building materials like mud-brick or adobe, which possess low thermal conductivity similar to sand. The thick walls of these houses act as a thermal mass, absorbing the intense daytime heat and slowly releasing it during the cooler night, regulating temperature swings inside the dwelling. This principle, paired with the utilization of design features like wind towers and qanat systems, helps to maintain a comfortable indoor climate. Some structures are even partially or completely built underground, using the earth as a natural insulator and benefiting from the surrounding cool sand. Consequently, it’s this strategic interplay of materials, design, and the desert environment that enables these homes to remain cool during scorching days and warm during chilly desert nights. This is a gross oversimplification of thermal dynamics but it’s the gist of it. It would be quite comfortable inside is what I am getting at.
Wikipedia claims “greater than 15 °C.” Besides, even if you supplement it with air conditioning, that’s 15 °C less ΔT worth of electricity you have to pay for.
I love passive systems. The more passive the better.
I assume the water here is doing the work. I didn’t say anything about a closed system, just passive. Maybe that doesn’t count as passive, I don’t know physics all that well.
The person that replied to you is probably being scientific-literal and obnoxious. I understood what you meant just fine. :}
The water does not perform work in this instance.
I do not think you’re trying to say the water “does work” in the physics sense, but to clarify, the water is just a large heat sink that has a much higher heat capacity than air. You can heat the water with air (which in turn cools the air), and that water can hold MANY times the heat (per unit mass) that the air can. Water also has a higher thermal conductivity than air. Allowing it to absorb and pass heat very well. This water is in the ground which also acts as a massive heatsink.
The air passes heat to the water which then passes the heat to the ground effectively cooling your air feed. A quick look online says current soil temp in Iran 21 inches deep is 35C or 95 F. That is your lower temperature limit. It’s physically impossible to become colder than the soil temperature (in this instance, as that is your lower temperature bound for heat transfer, in reality you wont even get there, because your driving force for heat flow is gone at that point) without putting in mechanical work (which is what a compressor does in your air conditioner) to compress your cooling fluid so that it may be evaporated repeatedly to exploit the tranfer of heat into an evaporating substance
Smart vs Facility (and the scramble who go with it)
My dude, I have no idea what you’re trying to say here.
I’ve read that these wind catchers were used to keep ice frozen in ice pits during summer.
https://en.m.wikipedia.org/wiki/Yakhchāl
Fun fact: Ancient Persia had ice cream like desserts enjoyed year round.
Amazing - I had no idea that anyone was making ice in the desert in BCE times. The wikipedia article seems to indicate that they did a lot of storing of ice in the Yakhchal structures - but it is confusing as to how they made it. It seems like they either gathered the ice from the mountains, or made it in outdoor shaded “ice pools” that were situated next to the Yakhchal. Surely the ice required winter desert temps to form? Otherwise how would the thermal mass of the ground ever get cool enough to allow ice to form, even with the magic of physics? The permanent shading helps, but year round-ice making surely wasn’t a thing, was it?
Seems like the ice pools were used for year round ice making at night. See the section on “Nocturnal ice making in early India and Iran”: https://en.m.wikipedia.org/wiki/Radiative_cooling
It’s called evaporative cooling and it’s quite potent since water takes enormous amounts of energy when changing states. It takes around 5x the energy to convert 100°C water into 100°C vapor than it takes to increase temperature of said water from 0 to 100°. This energy has to be taken from somewhere and that is from the environment, dropping the temperature as a result. Problem with these is that the humidity of the air increases. Not much of a problem in desert, quite a bit problem in other places.
Here’s a great video explaining science behind evaporative coolers and how it can be modernized. https://www.youtube.com/watch?v=R_g4nT4a28U
Just wind tunnels without water, I agree with you.
Wind powered swamp cooler. Basically a humidifier, but it does lower the temperature. I’ve heard people call swamp coolers air conditioning, so I don’t think it’s wrong.
No, calling swamp coolers air conditioning is definitely wrong.
If it’s 100% humidity in your room, the swamp cooler is going to do absolutely nothing, but AC will cool it down and can even dehumidify a bit if you run it enough.
Swamp coolers are awesome, but they only work in dry climates unfortunately.
No, it’s a swamp cooler, which is still used today in drier climates. This is a desert, so yes the air is not humid, and yes the water is cool because it’s underground. Stop being so pedantic.
On the point of calling eachother names, you two are acting like redditors.
Now you should really feel insulted.
Not really mentioned in the picture but Qanats are basically underground aquaducts, bringing water from nearby mountains to the cities. They can be up to 70km long. We went into one when I visited Iran.
