
A Refrigerator that Runs Without Electricity - stretchwithme
http://www.celsias.com/article/a-refrigerator-that-runs-without-electricity/
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iwwr
Not a new concept, see:

<http://en.wikipedia.org/wiki/Pot-in-pot_refrigerator>

and

<http://en.wikipedia.org/wiki/Absorption_refrigerator>

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wisty
It's also similar to old Australian meat keepers. Australia was, historically,
one of the world leaders at refrigeration development.

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toast76
It's also a common sight to see canvas water bags hanging from the front of a
4WD in Australia. The bag is porous causing some of the water to evaporate
slowly as you drive. Hey presto, beautiful cold water when stop to take a
break.

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chopsueyar
This only works in dry climates, no?

In humid, tropical climates this will not work.

MotherEarth had an article on building a solar-powered freezer that uses
ammonia gas. Use that to make ice, and then use the ice in an ice-box like
storage device.

[http://www.scribd.com/doc/6599651/How-to-Build-a-Solar-
Icema...](http://www.scribd.com/doc/6599651/How-to-Build-a-Solar-Icemaker)

Yeah, clay is easier to find than the other materials, but the ammonia freezer
does work without any moving parts.

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cubicle67
My grandparents lived, until the early '90s, on a farm with no running water,
no plumbing and no electricity. Lighting was provided by kerosene lanterns
hanging in each room, and they had a number (three, from memory) of kerosene
powered fridges for keeping things cold.

My google-fu is failing me this evening, and this is about the best I can come
up with <http://www.earthgarden.com.au/kerosene.html>

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pasbesoin
IIRC, natural gas -- or propane -- powered refrigerators are not all that
uncommon, either. This pre-supposes more infrastructure, but it's still not
electricity.

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Turing_Machine
Propane refrigerators are extremely common in the RV/camper world, likely
because most of them already have a propane tank for cooking.

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pbhjpbhj
Greeks used a twin pot system to cool (or keep cool?) their wine. They would
have a _psykter_ ("cooler") and a _krater_. The psykter is filled with water
or ice and floated in the krater holding the wine.

It's been long known that wet terracota on a windy day keeps the insides cool.

[http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:19...](http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0004:id=psykter)
page also describes a double walled amphora where the space was filled with
water, no mention of external glazing (or its lack). These are apparently
known as _psykter amphora_ ,
[http://books.google.co.uk/books?id=L-DYdyXXMy8C&lpg=PA22...](http://books.google.co.uk/books?id=L-DYdyXXMy8C&lpg=PA221&dq=double-
walled%20amphora%20~cool&pg=PA221#v=onepage&q&f=false). Such amphora are known
since 6th Century BC.

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Turing_Machine
A technology that I haven't seen mentioned yet is the thermoacoustic
generator. <http://en.wikipedia.org/wiki/Thermoacoustic_hot_air_engine> These
are basically a resonator driven by a heat differential. Very simple, no
moving parts. With the proper arrangements you can get out heat for cooking
(obviously), refrigeration, or with a piezoelectric module, electricity.
They're still more or less experimental, but very cool nonetheless.

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jberryman
A friend from Albuquerque, New Mexico was just telling us about _swamp
coolers_ which are commonly used instead of AC to cool homes, and works on the
same principle.

I'd never heard of it before.

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code_duck
Yes, I lived there and we had swamp coolers, aka evaporative coolers. They're
adequate, but not as deluxe feeling as refrigerated air.

It's basically a 3 foot wide wheel that spins in a metal box, blowing air.
Water is misted through the air that comes through the box, cooling it and
making it more humid. This works quite well in a dry place like Abq, but you
can imagine what it would be like somewhere like Houston that is already very
humid.

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hoprocker
AFAIK, evaporative coolers are more energy efficient than AC, as they just
power a small pump instead of a compressor.

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code_duck
Yes, they're far less expensive to operate than refrigerated air, since it's
pretty much just a fan with a bunch of water.

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forgottenpaswrd
We Spanish people had been using evaporative cooling since dogs bark.

Botijo(spanish version is more complete):
<http://en.wikipedia.org/wiki/Botijo>

Other methods that people used was making deep holes on the ground( > 30feet
10meters under ground level). Old houses in Madrid have (now sealed) passages
and cellars under ground. They were used as pantries(in some cases they had
snow with straw that lasted for months, now some are used for winery, but most
are closed and owners only realize they exist when they remodelate their
homes.

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drallison
Ammonia cycle refrigerators like the classic Frigidaire of the 1930s operated
on a small flame from natural gas, propane, or kerosene. See
<http://en.wikipedia.org/wiki/Ammonia_Refrigeration> for an overview of this
and other similar processes. Ammonia is toxic at the levels used for
refrigerators and was phased out in home refrigeration units for safety
reasons.

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kragen
You can still buy ammonia-absorption refrigerators today. A quick Google
search finds
[http://www.warehouseappliance.com/propane_gas_refrigerators....](http://www.warehouseappliance.com/propane_gas_refrigerators.htm#danby).
I had one in my Vanagon in 2006. It's certainly true that they're more
dangerous than compressor refrigerators.

Presumably you could easily operate a refrigerator like this with a solar
concentrator instead of a flame providing the heat.

A thermoacoustic cooler like the one in the SCORE project
<http://www.score.uk.com/research/default.aspx> could also refrigerate using
only a heat source, without a source of electricity. (The SCORE stove also
produces electricity.) I don't know what the state of the art in this
technology is right now.

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danboarder
The developer of this solution won an award for building and distributing this
to rural areas in Nigeria - see the cooler working in a video profile here:
<http://www.youtube.com/watch?v=SsH7dp2MB2c>

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lurchpop
The guy in the doc "No Impact Man" tried using one of these in NYC and I
recall it didn't work too well and he ditched it.

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johngalt
NYC isn't dry enough. This device operates through the evaporation of water.
Using a humidity delta to create a temperature delta.

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ChuckFrank
This double pot evaporation system is not new, it's ancient. I can clearly
recall seeing antique market photos from the 19th C clearly showing the double
pot cooler throughout the middle east. (can't find reference sorry.) It works
especially well in hot dry climates where you can have extensive evaporation.
It doesn't work in humid or cold climates. What's needed in North America is a
return to the root cellar, and external cold sheds or window boxes for
climates that fall below freezing. Again this is not new technology, but was
widespread in the 19c. (again, it is amazing that I can't find any image
references for window box cold storage.)

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ck2
But won't work where it's humid, right?

Because there would be little or much slower evaporation?

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meatmanek
Tomatos can last three weeks in this thing? My electricity-powered fridge
can't even do that!

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yhlasx
Creative and Intuitive. The same way our body keeps us cool by sweating.

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zitterbewegung
Does this scale? How large can the pot be before you run into problems?

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johngalt
The problem you run into with evap cooling is that you only get the benefit
once for a given volume of air. Once you humidify the air you can't humidify
that same air again. So its all about how much dry air you can bring in and
how quickly you can eliminate the already moist air.

I'd imagine that this pot in pot method wouldn't scale very far. Your cooling
a volume but your evaporation rate is governed by surface area.

~~~
ms4720
I think it would scale fairly well, just buy a second set of pots.

The thing I think lost in the discussion is that the solution is not a great
one in the general case and thats a given, so what. What it is is a way for
lots of very poor people to have a better quality of life. Also they can do it
on there own. This just might spark other very good local applications of
existing knowledge to existing problems. There is plenty of knowledge out
there that would improve the local living conditions, especially if that
knowledge is in the hands of people who really know what the local problems
are. Hopefully this will lead to other people boot
strapping/rediscovering/stealing simple solution to local problems.

To the people who are saying that this would not work in a rain forest, or
high humidity in general. A heavy winter coat is useless in the amazon, but I
am rather glad to have it in NYC during the winter.

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hoprocker
> I think it would scale fairly well, just buy a second set of pots.

He's saying that you couldn't scale the individual size of the pots that much.
The ratio of surface-to-volume changes dramatically as the pots get larger
(squared-polynomial for surface vs cubed-polynomial for volume).

Realistically, unless you are storing something which generates its own heat,
the only thing affected would be the amount of time to lower the internal
temperature to equilibrium, at which point the added thermal inertia of
everything in the pot would help keep things at temperature. With a system
like this, what you're fighting is the thermal exchange with the surrounding
air, which is of the same magnitude as the vapor exchange (both are a squared-
polynomial).

(Anybody with a less hand-wavy understanding of thermodynamics, feel free to
step in!)

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ms4720
I knew that, I was trying to say "So What" in a more polite way. My point was
this is better then what was available before. It is a real improvement in the
peoples lives who use it: more fresh food consumed, food costs go down and
probably less food poisoning by trying to stretch one more day from what we
have bought for dinner. It is cheap enough to be purchased and simple enough
to be maintained by untrained people. This is a solid step in the better
direction.

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SoftwareMaven
That sounds perfect for camping in the southwest US during warmer months.

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rickmode
Anyone know the typical internal temperature?

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hoprocker
Possibly a differential proportional to both the outside temperature and the
difference of humidity? I'd love some links to the physics behind this system.

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kazuya
Rather I would find radiative cooling cool.

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rms
Anyone do this at Burning Man?

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ghshephard
Unlikely. There is massive use of evaporative cooling techniques (We cool our
domes with a pair of Essick 3301 coolers) - but the preponderance of (A)
Electricity, and (B) ice at BRC would make it unlikely that anyone would futz
around with this technology to cool food instead of air, particularly as all
you would be doing is preventing food from spoiling, not particularly cooling
it that much.

I've often wondering if the critical ingredient that makes BM so popular (they
won't even sell tickets at the gate this year they are so oversubscribed -
might even sell out for the first time) - is that they sell ice at a number of
distribution points on the Playa.

Far more likely they put that energy into figuring out how to evaporate /
dispose of their grey water.

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JoeAltmaier
People at BM unwilling to futz around? Huh? Isn't that the point?

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pitdesi
See Also: Chotukool in India. Example of large conglomerate making products
for the base of the pyramid and succeeding:
[http://www.gizmag.com/refridgerator-rural-india-
chotukool/13...](http://www.gizmag.com/refridgerator-rural-india-
chotukool/13680/)

And Mitticool - this one is similar to the nigerian one in that it uses
evaporative cooling. [http://www.sankalpindia.net/drupal/know-india/mitticool-
cool...](http://www.sankalpindia.net/drupal/know-india/mitticool-cool-indian-
innovation)

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maxklein
I'm somehow very doubtful that this works effectively. If it is so effective,
then why is it so rare? Probably it keeps the goods somewhat cool, but not
particularly cool.

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johngalt
The operating principle isn't rare. We use swamp coolers here in Arizona all
the time. But I wouldn't use them to store food.

There are a number of limitations to them. The maximum cooling you'll get is
20F less than ambient, and that is entirely dependent upon humidity. So these
only work in places that are extremely dry (yet also have plentiful water to
run these coolers).

With the "pot in pot" method I wonder how they circulate air. You need a
fairly constant supply of dry air for evap cooling to work. I'd imagine a
porous exterior pot (think whiffle ball) filled with a spongelike material.

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hoprocker
> The maximum cooling you'll get is 20F less than ambient, and that is
> entirely dependent upon humidity.

Any idea about the specific physics here? I'd love to see some equations to
help explain this system (and the swamp coolers we use here in rural CA too).

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kragen
Equations: [http://en.wikipedia.org/wiki/Wet-
bulb_temperature#Temperatur...](http://en.wikipedia.org/wiki/Wet-
bulb_temperature#Temperature_reading_of_wet-bulb_thermometer)

~~~
hoprocker
Ka- _zaa_!

