Non-Electric Air Conditioner made from Coke Bottles

I haven't tried this, but it looks promising:   http://inhabitat.com/this-amazing-bangladeshi-air-cooler-is-made-from-plastic-bottles-and-uses-no-electricity/

Interesting idea.

This is the video from the page - there's lots more information there too.

Thanks Nancy (and Burra for putting the you tube where I could look at it without going off in to internet land)

This is very "cool" but I have a few questions:

I always thought the pursed lip blowing was cooler because it was faster and more concentrated on a smaller area of my hand, not because there was any actual change in the temperature.

Does it drop the temperature 10 degrees (the thermometers show a decrease of more than 10 C) or 5 degrees, as stated by the subtitles?
Does the air already have to be moving, as in a breeze or wind.

I always thought that when air was compressed the temperature would rise, but the subtitles say the bottle necks compress and cool the air.  So, I am wondering about the actual "physics" of the apparently wonderful contraption.

Maybe I ought to go to the website and see what they say, but that would be later and I may forget to look later.

I think they skipped a few steps in the explanation. I think when the air is compressed it releases heat energy back into the outside and so when it decompresses (coming out of the bottle neck) then the decompressed air is cooler than the original temperature. That's just a guess, but it's my first thought for how it might work.

The 10 degree/5 degree discrepancy is Fahrenheit/Celsius

Hi Casie,
That's what I thought, on the air being cooler when it expands.  At about minute 3:10, it shows the before and after thermometers in both C and F .

The C temp drops from 44 to 35 and the F temp goes from 112 to 95, so they are underestimating the amount of cooling by almost half.... unless the thermometer readings were not photographed at the same time.

Great idea.  I think the bottles are acting like simple vortex tubes. The wind pressurizes the air in the bottle and it spirals. The cooler air molecules spiral inward and enter the building while the hotter air spins to the outside and spills out the bottle to be carried away by the wind. Here are some vortex tubes used in industry

http://www.exair.com/en-US/Primary%20Navigation/Products/Vortex%20Tubes%20and%20Spot%20Cooling/Vortex%20Tubes/Pages/How%20a%20Vortex%20Tube%20Works.aspx

An entire wall that catches the prevailing winds could be covered with these things. Exhausting the hottest air out of the top of the building might help with efficiency.

I am thinking to put it in open windows in the summer.   But it might be a way to ventilate an attic too.

Not sure what they used for the plastic but I am thinking to use a 1/4" plywood board.

What a great concept!

Casie Becker wrote:I think when the air is compressed it releases heat energy back into the outside

The compression happens at the bottle neck, so that's the place where the kinetic energy of moving air molecules gets transformed into heat. My sense is that in order to release the heat energy back into the outside, it either has to lose heat by convection or radiation. I wonder how efficient that would be as the inside gets cooler, at which point the heat tends to transfer at that direction. If the top-edge of the neck gets colder, I think that there's also a chance for the heat to transfer inward through conduction, making the process a bit less efficient.

Another way to look at this would be the net change of pressure in the system. If the air pressure inside the room is same as to the outside, the resolution of energy would be zero, unless the heat accumulated at the bottle neck is released to the outside. In other words, the power of cooling would be proportional to the rate of heat loss at the bottle neck.

Hmm! How about this idea: maybe a bit more efficient version to this would be to have a highly conductive metal neck, attached to a thin copper pipe which carries water. Since copper and water have high levels of thermal conductivity, that would effectively absorb the heat accumulated at the metal neck of the bottle. Since the cooling power is proportional to the rate of heat loss, that would cool it down a bit quicker, I guess....

Devaka Cooray wrote:
Hmm! How about this idea: maybe a bit more efficient version to this would be to have a highly conductive metal neck, attached to a thin copper pipe which carries water. Since copper and water have high levels of thermal conductivity, that would effectively absorb the heat accumulated at the metal neck of the bottle. Since the cooling power is proportional to the rate of heat loss, that would cool it down a bit quicker, I guess....

I am lost.   Could you draw a picture?

It was only my best guess for what might be causing that. It looks like Benton Stuart has a more educated idea of what might be happening to make it work, below mine. I'd never even heard of vortex tubes before.

benton stuart wrote: Great idea.  I think the bottles are acting like simple vortex tubes. The wind pressurizes the air in the bottle and it spirals. The cooler air molecules spiral inward and enter the building while the hotter air spins to the outside and spills out the bottle to be carried away by the wind. Here are some vortex tubes used in industry

http://www.exair.com/en-US/Primary%20Navigation/Products/Vortex%20Tubes%20and%20Spot%20Cooling/Vortex%20Tubes/Pages/How%20a%20Vortex%20Tube%20Works.aspx

An entire wall that catches the prevailing winds could be covered with these things. Exhausting the hottest air out of the top of the building might help with efficiency.

Never heard of vortex tubes. A good topic for me to study. I didn't read, but there even seems to be some math related to vortex tubes.

What I'm a bit unsure about vortex tubes in this application is if the separation of air flow can be significant when you only have two sides, where the hot air has to come out from the same opening the air gets in. But, like I said, I never heard about vortex tubes before and my thought could be simply an ignorant one

I am lost.   Could you draw a picture?

I was picturing something like this:

Thank you for the picture Devaka Cooray.  Maybe use a solar pump to circulate the water?

The biggest problem with this setup is I rarely drink soda.   So getting sufficient bottles to try it out is proving difficult.

I am also wondering if the setup would work best on the sunny side of the building?  

wouldn't temperature differentials in the copper tubing create sufficient flow if there were a "cooling" location as well?

This is a fun thought experiment and idea to tinker with.  I love copper tubing and all its potential, and I think it is interesting how we are off and away with this idea, and imagining upgrades far beyond what's available to the people in the video.

Nancy Troutman wrote:Maybe use a solar pump to circulate the water?

Either that, or let the gravity take water slowly down from a bucket full of water placed at a higher position. If the bucket is large enough and the water flow is slow enough, it would take a whole day for the bucket to be empty. And, of course, you can reuse that water.

Thekla McDaniels wrote:wouldn't temperature differentials in the copper tubing create sufficient flow if there were a "cooling" location as well?

That would definitely be sufficient. But if the rate of heat loss at the bottle neck is proportional to the cooling power, a bit of a water flow would make the heat-loss happen faster, increasing the cooling effect.

Devaka Cooray wrote:

Thekla McDaniels wrote:wouldn't temperature differentials in the copper tubing create sufficient flow if there were a "cooling" location as well?

That would definitely be sufficient. But if the rate of heat loss at the bottle neck is proportional to the cooling power, a bit of a water flow would make the heat-loss happen faster, increasing the cooling effect.

Ah! of course!  I see it clearly, now that it's been pointed out.  

This all is working in basically the same way as a normal air conditioner:
1) compression of some refrigerant (driving the compressor is where the high electrical load comes from)
2) Allowing the heat created to dissipate (cooling fins on the back of your frig or on the exterior side of your A/C unit)
3) expansion of refrigerant (the temperature drops in that section of the A/C's plumbing and a fan is blown over it)
4) re-compression of the refrigerant.

As with blowing cool air out from your mouth, steps 1 and 2 are inside your mouth and step 3 is outside your mouth.

The heat generated will be at the neck of the bottles, outside. Problem is, you'll need a fair amount of wind to create the pressure to drive ambient air through the bottles necks. Also, dropping the air a few degrees on a hot day doesn't do much, at least not for me.

I can think of a lot more practical ways to get electricíty free cooling, e.g., upwind-facing air intake leading into earth tubes with the exhaust blowing their cool air over an air intake radiator. You don't want earth tubes venting directly into a living quarters, though. Too much of a risk of mold spores you can't control in the underground part of the earth tubes.

Or...here's a thought. Build a wofati.

Why not just tilt the bottles slightly and put a little water in each one? should hold about a cupful which would probably last all day. Not so good if it's humid but under arid conditions could be a poor-man's swamp cooler with no moving parts and no power or fan required.

I have my doubts.  Where would the extra heat go?  I don't think the air can be compressed that much.  

If it does work, and I would love to see a demonstration, I wonder if it has something to do with the concepts of what Viktor Schauberger's Klimator showed.  

http://peswiki.com/os:klimator:main-page  



P.S.  He was a master at dealing with water and making it healthy.  Also, for preventing erosion.

I share some of the doubts/confusions/skepticisms about the physics of this that have already been expressed.  However, if there is any heat at the neck of the bottle, plastic bottle material is not ideal for convecting or radiating it away.

On the other hand, a family member of mine drinks beer from those fairly heavy (compared to cans) screw-top aluminum bottles.  I have been casting about for a good use for them; they seem too useful to throw away and we are too rural for convenient recycling.  This seems like a perfect use to which they might be put, if it works at all.

The underlying physics is the Venturi effect which has an amazing number of practical applications according to that wikipedia page.
I wonder if you could use two or three bottlenecks in series, i.e. a stack, to get an even bigger temperature reduction. It would need more wind pressure which you could arrange with a large scoop.
For years we have opened our garage door as a wind scoop to funnel air through a screen door between the garage and our kitchen/dining area. I am going to have to experiment with adding a bottleneck layer to the screen door.
Other ideas are to cut the opening in the bottom of the bottle as a rectangle on the bottle side so as to make the bottle scoop air from wind parallel to the window plane, and by twisting the bottles make it slightly tunable to wind direction.
I have also seen bottles filled with water used in roofs to provide solar lighting - in this case the bottle neck points upward and the bottle body is down below the roof emitting light.
You could make a lighting/cooling window  by combining a rectangular array of intact bottles full of water with necks pointing out with an equal number of chopped bottlenecks pointing in placed so the necks align in the gaps between the full bottles.
You might not even need the outer chopped bottles as the normal ones already provide a constriction in the spaces between them.
At last something useful to do with all the empty two buck chuck bottles

While copper might work better in your area, part of what makes this work in the slums this is designed for is that there's no material in it worth salvaging.  Copper and aluminum are sellable for scrap,and it's not uncommon to see A/C units stolen for the metal parts (at least here in California).

Daniel Zimmermann wrote:While copper might work better in your area, part of what makes this work in the slums this is designed for is that there's no material in it worth salvaging.  Copper and aluminum are sellable for scrap,and it's not uncommon to see A/C units stolen for the metal parts (at least here in California).

Good point.   I think if you have the $$$ to do something else, there are better ways to cool.  However, if money is scarce, this is an almost free way of getting some relief from the heat.  The biggest disadvantage I see is bugs.   I am concerned a screen might block much if not all of the wind created by it.  It will take me some time to collect enough bottles as I am not a soda drinker, and neither are my friends.   However, at the very least I plan to use this in my chicken coop and barn windows.

I'll apologize in advance, but I just couldn't resist. A couple people commented on difficulty in getting bottles because of not drinking soda. I don't drink soda (or pop as it is called here) any more either, but if you are looking for materials to experiment with and don't mind spending a bit, you can use bottled water bottles.  You are still spending money, but at least you are not poisoning your body.  Another possibility would be to simply knock on a few neighbor's doors and ask for them.  Or here's one...  Head out on the day your local refuse folks pick up "recycling".  Yes, I am suggesting you go STEAL them from the neighbors cans.  At least you don't have to dig through actual garbage.  And I would be remiss to leave out good old dumpster diving.  Have fun with it.  If you want free plastic bottles, there are literally millions of them out there.  Get creative and go get'em.  Heck, you could kill two birds with one stone and go pick them up off the road somewhere.  You'll be getting your bottles for free and doing a great community service at the same time.

It would take me forever to accumulate enough bottles. So... alternatives... you could probably achieve the same effect with scrap wood -- a trough rather than a funnel, but basically the same effect as a barn vent.

While this simple system might have an apparent cooling effect of some sort, it's literally impossible for this effect to be due to compression of the wind as it passes through the bottle necks.  The Law of Conservation of Energy would be violated.  However slight and temporary the compression effect might be, compressed air does not suddenly lose it's net heat energy, it's just in a smaller space.  Which would read hotter, not cooler.  This is why compressors require heat fins in order to disperse the concentrated heat into the environment, before decompressing the air/gas resulting in a cooling effect.  The venturi effect might be part of it, allowing the warmer molecules of air to "spiral" out to the edges of the bottle, therefore the remaining molecules of air in the center (where the neck actually is) to be slightly cooler on net.  However, this effect would only work with a good cross wind that does not arrive anywhere near perpendicular to the face of the device.  The apparent wind angle would have to be somewhere around 30 degrees from perpendicular to get the swirl right.  Much more angle than that, and a mild vacuum is the more likely effect.  Thus, the conditions for the venturi effect to be worthwhile are unlikely to be common, so any apparent cooling by that method would be highly weather dependent.

I have to call B.S. on this video.  I don't believe their measured effects are due to the construction of this device.  More likely just due to a time delay in measurements, and the weather conditions improved slightly.

Even if it does not actually cool the air, the venturi effect would be the equivalent  to the "wind chill factor".
If it concentrates the moving air past you, it would have a cooling effect.
At those temperatures, any improvement, no matter how slight, would be welcome.

Seems like to know for sure if it does/would work, or doesn't /couldn't work, a person would have to build such a device and try it out.  All in all, it is, and has been, an interesting idea activating many folks' creative and problem solving processes.  That's valuable.  

We have use it or lose it functions in our nervous systems.  To take up an idea such as this and consider it against what we already "know" as true  (maybe read that as 'currently accept as fact'), and consider the possibilities presented, remember "laws" of physics and mechanics to test it as a thought experiment, then if interested,  build it, and see if what we thought was true really is true, exercises part of our brains integral to being human.

And, most fun of all is when something does NOT work the way our previous experience and understanding of physics and such led us to believe it would.  Then we get to begin to figure out why it did not do what we thought it would, and see what that teaches us about the natural world, and begin to think about ways to put our new knowledge to work.

When we accept the word of "authority" or "expert", especially in times such as these, when those terms are more often an indication of status, than superior knowledge, wisdom, judgement or critical thinking, then we let our own brains atrophy, literally.   Let go far enough, we could not possibly think for ourselves or generate an independent idea. And when we engage in the exploration of a seeming impossibility, we utilize, and keep current,  our abilities to think, learn, analyze, plan, consider possible outcomes.

Simple test from http://www.geek.com/science/eco-cooler-air-conditioner-cools-a-home-without-using-electricity-1657343/

"To test this, hold your hand up to your mouth then open your mouth wide and breathe out. The air is warm, right? Now do the same thing but with your mouth closed to typical a blowing position. The air leaving your body is cold, right?"

Dave Smythe wrote:Simple test from http://www.geek.com/science/eco-cooler-air-conditioner-cools-a-home-without-using-electricity-1657343/

"To test this, hold your hand up to your mouth then open your mouth wide and breathe out. The air is warm, right? Now do the same thing but with your mouth closed to typical a blowing position. The air leaving your body is cold, right?"

The blow on your hand test involves you first compressing the air with your lungs and mouth then blowing out compressed air that decompresses to atmospheric pressure.
The soda bottle device has air at atmospheric pressure on both sides and there is no cooling effect apart from you're letting ambient air into the building.
Air is not compressed when it enters a funnel so there is no cooling effect from decompression upon entering the room. When air flows thru a constriction its pressure drops due to the venturi effect. the air entering the room at the opening of the bottle is below atmospheric pressure, having had its pressure lowered thru being funnelled, it will immediatey increase in pressure on entering the room and regaining atmospheric pressure - the opposite of what is being supposed. There will be a small but possibly unnoticeable warming effect from using one of these devices compared to just allowing air to flow thru a hole in the wall. This myth has been busted in plenty of physics forum discussions on the internet.

I'm surprised how much resistance there is to this. I'm going to try to rustle up a fan, a bottle, and a thermometer and run a test.

By all means!  This is one of those ideas that sounds too good to be true and offends what many of us think we know about scientific principles -- but that's been true of many a new invention in the past.  By far the best way to believe in a new thing is to see it for yourself, but many folks are resistant to wasting time and other resources on a notion that seems half-baked; the next best thing is for people in your community to testify "I tried it and it worked".  A video by internet strangers, on the other hand, is not very persuasive; we've all had the unfortunate experience of discovering that there are many people on the internet whose hobby is to tell lies and fool strangers for motives inscrutable.  

I freely admit that I don't fully understand the physics that's claimed, variously, to make this work or to make it impossible.  I have *opinions* about those physics that lead me to judge that the experiment isn't worth my time.  But I'll revise those opinions in a hurry if members of this forum start sharing positive reports of their experiments.  And given that I live in a hot place that's predicted to get a lot hotter, and I have a summertime electric bill that's already oppressive, I'd be delighted if this turned out to work even marginally.

I wish I saw this technique last spring.   September is not the time of year to properly test it out.

Nancy Troutman wrote:I wish I saw this technique last spring.   September is not the time of year to properly test it out.

No, but Dave is correct: if the principle works, it could be verified fairly simply on a lab bench with an enclosed box, a test rig, a fan, and some temperature measurements.  You'd still have to wait for summer to find out if the effect was strong enough in practice in a given location given prevailing wind directions and strengths to be worth bothering with.  And of course it would depend on what *other* design functions you need from your windows; in places where glass windows serve important functions for excluding insects, precipitation, dust, or noise, this cooler might not be desirable even if it works.  

Well I tried this myself with a pedestal fan, various bottlenecks/constrictions and a couple of different thermometers and I saw no change other than my face is now a bit redder with embarassment.
There's a good video experiment at

http://waploot.in/download/SuuNlZIbgrM/does-the-eco-cooler-really-work.html

that shows there is no measurable cooling effect. The original video at the top of the thread that shows a shot of before and after thermometers is fishy because it shows a difference of 10 deg C which is much larger than the claimed ~5C/10F cooling.
Now if instead they filled the coke bottles with water and stacked enough of them inside their tin shack, they might get some moderation of daily temperature swings, but the daily range between min and max temp in Bangladesh is only about 10 deg C in summer.

Good for you for giving it a try, Dave.

But holy cow!!! filling the coke bottles with water would also retain the heat long into the night.  I spent a few days in a concrete building in Senegal.  The west wall absorbed heat until sundown, and did not finish radiating it back out again until 2 or 3 in the morning!  It made for difficult sleeping conditions, for me anyway, liking cooler fresher for sleep.  It gave me a huge amount of respect for the young woman Peace Corps volunteer who not only lived in those conditions,  but shared the Ramadan tradition with the locals, eating and drinking NOTHING at all while the sun was above the horizon, and even going ahead with her daily run after strenuous physical work outdoors in the sun all day.

To use water's ability to soak up heat, I would also want an easy way to send the water elsewhere to radiate that heat, and would probably want to reuse the water.  The young woman I visited in Senegal planted plants to shade the west wall, but they were a year away from covering the wall when I was there.

Oh, nice, let me put that video inline for people:  

Thekla McDaniels wrote:Good for you for giving it a try, Dave.

To use water's ability to soak up heat, I would also want an easy way to send the water elsewhere to radiate that heat, and would probably want to reuse the water.  The young woman I visited in Senegal planted plants to shade the west wall, but they were a year away from covering the wall when I was there.

Water has excellent heat density, particularly as a phase change material, but the problem is that you have to have a source of quite a bit of it.  There didn't seem like there was likely to be a nearby well in the neighborhood shown on the video.  Common ivy planted every couple feet along a wall makes for a wonderful shade method.  The technique can also be used effectively for shading roofs, simply by stretching & suspending a bolt of dark cloth an inch or two above the tin roof.  This not only permits air to convect behind the shade, thus providing some forced air cooling by the convection draft powered by the sun itself; but also limits the infrared heat effect of a tin roof.  It does this by absorbing & re-radiating solar energy as infrared heat; but the exposed tin roof will radiate from both sides, so roughly half of the solar gain will make in into the living space anyway.  With a deliberate roof shade, the roof shade radiates in both directions as well; so even if the cooling effect of the convection draft were negligible, only about 25% (at most) of the solar gain would make it through the tin roof and into the living space.

These "A/C" units seem to be meant for tin shacks that are probably hot AF because they conduct so much heat. Probably the better thing to do is to insulate those solar ovens with hay bales, but I can see how the bottle AC is easier and more likely to be implemented. This is not a developed world solution to cooling, but I want to try it out and see how well it can cool my tuff shed.