((Note: this is post of mine from a different site that is about a year old, but thought I would share it here too in case it helps anyone))
Old technology is once again getting attention, and this time it’s air-conditioners made out of terracotta clay.
“She was inspired by the Palestinian Jara, a traditional clay water container that is hung from the ceiling to cool water and cool the air. Specifically, the water contained in the hollow internal structure moves outward through the porous clay walls. With the heat of the air, it evaporates and is transformed into water vapor. This reaction absorbs heat from the surrounding air, cooling the water, the material itself and consequently the air in the room.” Forbes India In regards to Yael Issacharov.
There are two unrelated people currently being mentioned for promoting their designs using this technology; Monish Siripurapu(from India), and Yael Issacharov(from Israel).
Monish Siripurapu’s design is based off a beehive and uses a small pump to create a beautiful water fountain that both cools the air and can be used for gardening.
Yael Issacharov’s design uses no electricity, and instead relies on the naturally porous nature of the clay.
For dry and hot climates, this old technology could provide cooler air at an affordable price. The clay is readily available almost entirely world-wide, making it accessible and inexpensive.
"The humid clay traps some heat the air and the surrounding air gets cooled down to around 6-10⁰ C due to the process of evaporative cooling.“ EcoIdeaz in regards to Monish Siripurapu
Videos with more info:
Based on this information, I am wondering if a terracotta pot and a fan would have the same effect for a small room. Here's a drawing of mine to help explain what I mean:
I'm sceptical of evaporative coolers. In the short term it might work well, but it increases humidity. That leads to sweating being less efficient and generally a worse situation than before.
There would need to be a way to remove moisture from the air, which ironically was the original purpose of air conditioners, not temperature.
They do not work well in already humid environments but in a hot and dry climate they do quite well. It absolutely does add to the humidity (obviously) but speaking from experience I'd rather have a evap cooler than not if my AC is out.
The largest difference in utilizing one over AC is that they rely on airflow so you need to actually ventilate the area you are cooling as compared to AC where you want a sealed space.
The main driver is power efficiency. Only thing they are doing is running a small water pump and a big fan.
Evaportaive coolers are only effective in low humidity enviroments like a desert. Unless the room is hermetically sealed, the cooler wouldn't add enough humidity into the air for you to notice.
If you use it in a high humidity environment its just not gonna work.
The moisture is why this really only works in arid climates.
If you try this in more humid clicates, you're gonna roll the dice on getting mold in your house.
You are unfortunately wrong in your scepticism, they've been used for millennia to great effect, and are even part of how ice was made.
In a modestly arid climate (like a mountainous region) with 30% ambient humidity, you can achieve, a 12 °C drop, that's a lot more than the ~10% of lost sweat cooling.
It's not just about losing sweat cooling. Humid air is better at conducting heat (because water is), so if the air temperature exceeds your external body temperature, then it accelerates the heat being conducted into your body.
Check the source, net difference is 10%
I've only skimmed it, but Figure 1 shows their skin temperature consistently above the 31°C air temperature, so the humidity should inhibit evaporation of their sweat, which is bad for body temperature, but the humid air should still be conducting heat away from their body rather than into their body.
Check out figure 2 it shows equivalent cooling in energy units. Meaning how much energy is carried away by perspiration, and showing it for different levels of humidity. I read it as between 5-10% lower at higher humidity.
Compare that to the radiant heat difference (from 32 degrees to 22, as per the cooling chart) which cools you about 286 % more. And with convective cooling we expect even more at higher temperature differences.
(Calculated with Boltzmanns law for 310 K body temperature)