this post was submitted on 24 Jul 2023
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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.
The AC is also small compared to a literal building with a sewer underneath and doesn't require a windy day. Trade offs
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
Do we know it's more efficient? Has anyone done the math?
Are you joking?
No, I'm being genuine. It's theoretical and all, but if you were to put up a windmill in the same spot instead of a tower, it's possible traditional air conditioners would be able to cool the building to the same degree while also providing surplus electricity. It's also possible that you wouldn't, and I don't know the answer. It would also be interesting to compare it in different ways as well, like rather than asking "If a windmill was here" we could ask "The energy removed from the wind by the tower", because that would indicate scalability problems if one windmill was indeed able to cool one building, but maybe 100 wouldn't be able to cool 100. All hypothetical, but air conditioners/heat pumps are actually very efficient, so it's possible an active design could be more efficient than a passive one in this situation. At least, until someone does the math
Exactly, I have no idea. The "probably(?)" in my comment should have been a "maybe," probably maybe.
Another thing to note, to your point, is that a windmill breaks down and requires energy to repair. These wind towers in Yazd are still there and doing the same thing from hundreds of years ago
Very true. The best machines have the fewest moving parts
True, and it wasn't meant as an attack at all, just a question out of curiosity. The towers are super cool
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. :)
Yes, that sounds about right - the relative effect of the tower probably depends a lot on various factors like how windy it is, if extreme heat occurs only for a day or if it has been ongoing so that the water under ground is heated as well, etc.
These comments were in response to @Gangreless, who stated that a modern AC "can only cool about 20f below the outside temperature". I didn't catch that it was fahrenheit first, and now that I know I am happily backing off rather than having to think in terms of freedom units.
They're full of it, that's it. Maybe in their house which lacks sufficient insulation. Heat pumps (i.e. air conditioning) are/is extremely efficient at moving heat around, there's not really a practical limit on it, particularly if you go geothermal.
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/
pretty sure 50c to 35c is 15 degrees
I wonder how he got his number, it makes no sense.
EDIT: oh, he just randomly mixed °C and °F, because why not...
Fucking Americans
It’s the Mars Climate Orbiter all over again.
50c is 122f, 35c is 95f so he went 50c-35c = 122f-95f = 27f because why the fuck not.
That's just not true, a modern home can be at 70f or below when its 110f outside. Air comes out at 50-55 even at those outside temps.
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.
Are you my brother? Whenever I go to his place I feel like I'm going to get hypothermia lol
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.
Your heat pump will definitely do it, it’ll just take a long time.
The 20 degree figure everyone is throwing around is actually supposed to be the difference between the return air temperature and the supply air inside your home
If you have 80 degree air in your house, 60 degree air should be coming out of your vents. Once the 60 degree air has cooled down the house to 70 degrees or so, 50 degree air should be coming out of your vents. And that’s about the theoretical limit for home air conditioning, as anything lower means the cooling coil is below freezing and will get damaged by ice, there’s usually a safety switch that prevents things from getting too cold.
Now the outside coil needs to be hotter than the surrounding air to actually push that heat out of the coil and cool off. Most places around me are designed for a 95 degree summer day, so will have a refrigerant temperature of about 120 degrees, in order to move that heat. Your compressor needs to be able to compress the refrigerant from your cooling coil until it’s about 30 degrees F hotter than the outside air. The hotter it is outside, the harder it is on the compressor. But it will eventually do it if you let it run long enough. Whether or not you want to pay for all that electricity is another thing entirely.
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.
But don't "swamp cooling" systems like the one in the OP not work well in humid environments? Sure, I have running water at home, but I also live in an incredibly humid climate.
I was more imagine something like the opposite of a district heating system and then using colling ponds or towers to disappate the heat from the system..
Don't you have water to drink at home? Or in the bathroom?
Modern plumbing uses pressurized pipes that are completely full of water, and can thus flow uphill, as long as the elevation gain doesn't exceed the head pressure from the water tower or pumps. That makes such pipe systems relatively cheap and easy to build.
In contrast, qanats require large conduits with space above for the air to flow through, using open channel flow. That means the entire system needs to be designed with a gentle downhill monotonic slope. That's doable (the wastewater and stormwater sewer systems are designed that way, for example), but it's more expensive and would require a lot of re-work if you wanted to convert over the existing water distribution system.
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.
And get it has way more upvotes than down, just like reddit.
Reddit is sipping here at a rapid pace...
Well, Iran is mostly desertic so I assume the air must be very dry.