Eco-Cooler - world’s first zero-electricity air cooler made from plastic bottles

Gundersen

Senior Member.
I stumbled upon the following video on Facebook:



Most homes in Rural Bangladesh are made out of tin huts that go over 45° celsius during the summer. Our employees volunteered and teamed up with Grey Dhaka to address this issue.

Re-purposing used soft drink and water bottles, The Eco-Cooler works without electricity to reduce temperatures up to 5° celsius.

Grey Dhaka unveils world’s first zero-electricity air cooler made from plastic bottles

Zero electricity air cooler from Grey DhakaGrey has come up with an idea to keep rural housing in Bangladesh cool using re-purposed plastic bottles and no electricity in time for the hot summer months and the advertising awards season.

The agency teamed up with Grameen Intel Social Business, a Dhaka-based social business IT company, to create grids made from plastic bottles cut in half that can be placed in windows. The agency claims the Eco-Cooler can reduce the temperature of a room by five degrees celsius.
The video explains how the Eco-Cooler works with the same cooling effect as a person blowing air with pursed lips.

Eco-Cooler“After initial tests, blueprints of the Eco-Cooler were put up online for everyone to download for free. Raw materials are easily available, therefore, making Eco-Coolers a cost-effective and environmentally-friendly solution”, Syed Gousul Alam Shaon, managing partner and chief creative officer at Grey Dhaka, said in a press release.

The agency claims the Eco-Coolers have been installed in villages in Nilphamari, Daulatdia, Paturia, Modonhati and Khaleya.

Grameeen Intel Social Business’s deputy GM Abdullah Al Mamun commented: “Since most rural homes in Bangladesh are made with corrugated tin, the Eco-Cooler has the power to provide relief to millions of Bangladeshis. We sincerely hope this volunteer effort will make a difference in their lives.”

The Eco-Cooler is another idea from Grey that fits with what the network’s creative head Per Pedersen describes as “solvertising” – work that solves social and environmental problems.
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To be honest, this makes very little sense in my head.

upload_2016-6-23_9-59-45.png

I tried to find something regarding heating/cooling of air by compression/decompression, but I came up short. I can easily imagine this working like a fan, creating ventilation. But cooling the air? Furthermore, I would also guess that the degree of actual compression would be quite insignificant. I would quickly call BS, but I might be too early. I would have researched this myself but had a hard time figuring out how to find the relevant physics.
 
Some more googling, I found a principle called Adiabatic processes.

https://en.wikipedia.org/wiki/Adiabatic_process#Adiabatic_heating_and_cooling

Adiabatic heating and cooling
The adiabatic compression of a gas causes a rise in temperature of the gas. Adiabatic expansion against pressure, or a spring, causes a drop in temperature. In contrast, free expansion is an isothermal process for an ideal gas.

Adiabatic heating occurs when the pressure of a gas is increased from work done on it by its surroundings, e.g., a piston compressing a gas contained within an adiabatic cylinder.

...

Adiabatic cooling occurs when the pressure on an adiabatically isolated system is decreased, allowing it to expand, thus causing it to do work on its surroundings...
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Wouldn't this mean that the initial compression would increase temperature equal to the drop in temperature you would gain from decompression? So no net loss in temperature?
 
Hm.. you can start fires with air compression.
Aight, found a link:
https://en.wikipedia.org/wiki/Fire_piston

A fire syringe is a piston-and-cylinder device used to demonstrate compression ignition. A typical fire syringe is a thick-walled transparent cylinder fitted with a metal piston which can travel to within a short distance of the bottom of the cylinder.
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I too, can't get my head around how this should work..
 
Unless there is a breeze there would be no air going thru the bottles. The homes look congested and up against each other. I can't see how this would work at all.
 
I would also guess that the degree of actual compression would be quite insignificant
I don't think it would come close to that required to achieve the claimed reduction in temperature:
The Eco-Cooler works without electricity to reduce temperatures up to celsius
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My interpretation could well be wrong, but according to this:



the Joule-Thomson Coefficient for air (mostly nitrogen) at 300K (27°C/80°F) is about 0.36K/bar. This means that at 300K a 1bar change in pressure equates to a 0.22K. The change in pressure required to get the 5°C (5K) reduction would therefore be:

5 / 0.22 = 22.7bar

This is just an estimate as the Joule-Thomson Coefficient decreases when temperature rises, so the hotter the air is to start with, the greater the drop in pressure required to make a 5° fall in temperature. 22.7bar is a conservative estimate as this is reportedly being used where temperatures routinely exceed 300K and the system will not be 100% efficient.

So, in order to achieve a 5°C cooling effect the bottles would have to compress the incoming air to at least 24bar* so that when it expands to normal atmospheric pressure you get the pressure drop needed. That means (in terms of pressure) that the bottles are working at near the operating limits of this thing:



*and somehow avoid the inevitable heating effect of pressurising the air.
 
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To cool air you have to move the heat somewhere. You can certainly cool a house by compressing air so it's hot, passing it over some kind of heat sink to pipe away the heat, and then expanding it again. It would not be very efficient though, and this "invention" lacks any significant compression, and any heat transfer mechanism. The incoming air can not be any cooler than the outside air.

I suspect from the description: "the same cooling effect as a person blowing air with pursed lips" that all this does is focus the breeze into more intense spouts of air that then feel cooler.

Another possibility is that it provide airflow through a window that normally would have the sun shining though it. So if you compare these possibilities:
  1. Window is covered with no airflow or sunlight coming in, the house is an oven
  2. Window is closed, but sun is shining through, heating the house, worse case, greenhouse-like
  3. Window is open, sun is heating the house, wind is cooling it
  4. The "eco-cooler" is installed, sun is blocked, wind is cooling
Then #4 would be coolest, with the additional benefit of a focussed breeze.
 
I agree with Mick, that creating shade while preserving the air flow is probably the major benefit. It is effect similar to Venetian blinds, used since centuries:



Additionally, as Mick also mentioned, the focused air flow helps too. Focused faster air flow creates so-called "wind-chill" effect - the room temperature with fast moving air does not sink, but it feels cooler, because it helps the sweat evaporation and removing body heat faster than standing air.

The Bernoulli's effect used in some types of passive ventilation (using the difference of air flow and pressure on the roof for sucking the air from the surrounding through the building) is likely not significantly involved in this case. See http://sustainabilityworkshop.autodesk.com/buildings/stack-ventilation-and-bernoullis-principle for some examples of passive ventilation based on Bernoulli's principle and stack effect.

So basically, I'd tell the invention can certainly help in some cases, but I would like to debunk the example with hot and cold air blown with open resp. pursed lips. The arguments used in the video are definitely wrong. The temperature felt on the hand has nothing to do with the compressing the air. This exact problem is very well explained for example at http://www.thenakedscientists.com/H...our-breath-sometimes-warm-and-sometimes-cold/, so I just copy and paste a part of the text here:
If you create a jet of fast moving air through stationary air it tends to drag the stationary air along with it, essentially due to friction. This is called entrainment, and the effect is stronger the faster the air jet is moving.

When your mouth is open the air coming out will entrain some cold air, but the air which reaches your hand will still be dominated by the warm air from your mouth.

But when your blow hard through pursed lips the jet is moving a lot faster so it entrains more air, and there is less warm air there to start with, so most of what reaches your hand is colder room air. Although this air is slightly warmer than the air in the room it moving so it is much better at removing heat from your hand both by conduction and evaporation so it feels cold.

With your mouth open most of the air which reaches your hand has come out of your mouth.
lips03.gif
With pursed lips lots of cold air is entrained so the air reaching your hand is cold and moving quickly.

lips02.gif
If you feel the air coming out of your pursed lips very close to your mouth it hasn't had time to entrain cold air, so it still feels warm

lips01.gif
If you feel the air from pursed lips close too it will still feel warm

And if you feel the air from an open mouth a long way away it will have entrained enough air to feel cold.
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  1. Window is covered with no airflow or sunlight coming in, the house is an oven
  2. Window is closed, but sun is shining through, heating the house, worse case, greenhouse-like
  3. Window is open, sun is heating the house, wind is cooling it
  4. The "eco-cooler" is installed, sun is blocked, wind is cooling
Then #4 would be coolest, with the additional benefit of a focussed breeze.

i totally agree with, that. nevertheless. option 4 would work without the bottles. Just the board with holes.
Even better without, since there is nonair heating up inside the sun drenched bottles, or am I missing something?
 
i totally agree with, that. nevertheless. option 4 would work without the bottles. Just the board with holes.
Even better without, since there is nonair heating up inside the sun drenched bottles, or am I missing something?
No, a board with holes would create somewhat less airflow, as there's less catchment area facing the wind.

This all seems like it should be easy to test though.
 
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