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Situation:

  • Forest
  • Clay Ground covered in pine needles
  • Pacific Northwest Climate
  • No River
  • No Electricity
  • Can provide purified water, and whatever building materials needed.

Goal:

  • Construct a cooler which can permanently serve as an fridge out there.
  • Must be able to keep eggs from spoiling for at least two weeks, and Milk for at least one week.
  • Can't use electricity.

During the spring, winter, and fall; cooling is generally not an issue, living in Canada after-all. The summer here though has proven a bit of a challenge. What I have tried so far, is to keep my milk cold by filling a bucket up with water, and placing my milk in that. It does not work excellently, but I gather it is at least doing something.

I have read that if you dig a hole in the ground, this may be a better way to keep things cool. I am willing to go to just about any extent short of buying a fridge and a generator. The most naturally cold substances I gather would serve as the best means to surround my container.

A solution is needed!

Anon
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    Eggs do not necessarily need to be kept cool –  Jul 23 '14 at 09:45
  • The folks at [Sustainability.SE] might have ideas as well. – gerrit Jul 23 '14 at 16:00
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    If the eggs have previously been refrigerated they MUST continue to be refrigerated. However, if the egg is fresh and has not been refrigerated they can last weeks in the summer heat. eggs are designed to hatch baby chicks in a healthy environment, eggs only get "rotten" if bacteria has invaded them; they don't just rot from lack of refrigeration, or it would be impossible for hens to hatch chicks. Important to note that you should not wash them once you collect them fresh as there is a protective coating on the egg, wash when ready to consume... – AM_Hawk Jul 23 '14 at 19:00
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    More info on what @AM_Hawk said: http://cooking.stackexchange.com/questions/14775/how-long-can-eggs-be-unrefrigerated-before-becoming-unsafe-to-eat – nhinkle Jul 23 '14 at 19:22
  • Can I store eggs in a jug full of water? According to this: https://ca.answers.yahoo.com/question/index?qid=20070704134026AAtYDjp "You can always float them. If you are ever concerned about eggs being good you can gently place them in a container of water. If they sink they are good. If they float up to the top, toss them. They are spoiled. If they are kind of boyiant but still on the bottom they are still good, just older. These eggs boil up and peel perfectly since they membrane seperates more easily." – Anon Jul 23 '14 at 20:17
  • @AM_Hawk Where do you get your information about continuing to be refrigerated? We keep our store-bought (refrigerated) eggs out of the refrigerator, and have never had any spoilage (they generally get eaten within one week, sometimes two). – ErikE Jul 24 '14 at 02:32
  • @AM_Hawk Have you reviewed the information linked to in the comments on the question how never refrigerated eggs can be good for a month or longer? I thought you were trying to say that refrigerating an egg somehow reduces its later potential unrefrigerated life, and can't figure out a mechanism for this (other than some kind of moisture thing). If the eggs don't spoil in 30 days at room temperature, clearly there are no substantial bacteria colonies inside to "rapidly increase" in growth. It may be that commercially washed eggs won't last as long outside the fridge. – ErikE Jul 24 '14 at 04:29
  • @AM_Hawk Could you please offer some kind of information as to why, other than mere assertion or supposition, please? How exactly does refrigerating an egg make it spoil faster once you take it out of the fridge? – ErikE Jul 24 '14 at 05:02
  • @AM_Hawk So the issue was never lack-of-refrigeration-after-refrigeration, but that store-bought refrigerated eggs are presumptively washed, thus lack-of-refrigeration-after-washing. Thank you for at last making it clear! – ErikE Jul 24 '14 at 06:14
  • Why is electricity ruled out? Is there something preventing you from using photovoltaics? –  Jul 24 '14 at 16:33
  • @BenCrowell At least in the short term, it is sheer economics. I am willing to spend up to a hundred dollars on a method of refrigeration. I make about 200 dollars a month, half of that is spent on food and other amenities, and so I gather it would take me a long time to save up enough to accomplish this. Also; It rains 1/3rd of the time here, and the woods makes sunlight gathering quite difficult. – Anon Jul 24 '14 at 21:39
  • You might consider to ask this at [sustainability.se] as they probably have more experience with this over there. – Paul Paulsen Jul 25 '14 at 14:48
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    @AM_Hawk just to add to the comments, already refrigerated eggs store just as well on the counter. I haven't put store bought egg (USA HERE) in the fridge for decades, and they've lasted as long as several weeks. Fresh eggs can last month's on the counter. – Escoce Dec 16 '15 at 17:52

7 Answers7

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The first solution that comes to mind is a "zeer", or pot-in-pot refrigerator. However, this functions best in hot and dry environments as it relies on evaporation to work.

Such a device is constructed by nesting one clay pot inside another, with a layer of sand between them (about an inch on the bottom, a few inches on the sides). The sand is then soaked with water until saturated. The food goes into the inner pot, which can then be covered with a sheet of wet burlap.

A Zeer

"Clay pot cooler - Canari Frigo - Tonkrugkühler" by Peter Rinker - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Clay_pot_cooler_-_Canari_Frigo_-_Tonkrugk%C3%BChler.PNG#mediaviewer/File:Clay_pot_cooler_-_Canari_Frigo_-_Tonkrugk%C3%BChler.PNG

Alternate solutions include an Einstein-Szilard refrigerator, which would require a good bit of skill to construct but only needs a source of heat to power it. Another option is the traditional root cellar. However, it usually requires digging quite deep into the ground to construct a root cellar that will maintain ideal temperatures. You may be able to get somewhat OK results with only a foot or two of soil as the top insulating layer.

requiem
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  • If it relies on hot dry environments, I am afraid I am out of luck. My environment is heavily shaded, from being in the forest, and it is quite humid. Although, I may still consider trying it. – Anon Jul 23 '14 at 06:02
  • Another variation that only requires a heat source (e.g. keep some hot coals going) is the Einstein-Szilard refrigerator, but that's probably not going to be straightforward to create: http://en.wikipedia.org/wiki/Einstein_refrigerator – requiem Jul 23 '14 at 06:33
  • Looks heavy???? –  Jul 23 '14 at 09:45
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    @requiem - If you don't mind lugging around a propane tank, such a refrigerator (a "3-way refrigerator") can be purchased off-the-shelf for a few hundred dollars. – Compro01 Jul 23 '14 at 18:09
  • @Compro01 Ah, yes, a good suggestion especially if the OP is car-camping! – requiem Jul 23 '14 at 18:48
  • Alas; the OP lives in the woods, in a tent. To the first suggestion though; the pot in pot refridgerator; This would be the easiest for me to implement as I could refill this thing daily. It is just that it is going to be in the shade 23/7; will this still work? – Anon Jul 23 '14 at 20:06
  • Is is a permanent site that you can develop, or just a random place you'll be visiting for a few weeks? – requiem Jul 23 '14 at 20:14
  • @requiem This is a permanent site I can develop. The only thing to note is that during the winter, the lower parts flood. My location during the worst times, will be about 4 inches above the flood. – Anon Jul 24 '14 at 06:47
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    @Akiva In that case the idea of the barrel-style root cellar sounds useful, as you can go deep enough to get cooler temps. (Yep, saw your other question.) – requiem Jul 25 '14 at 17:36
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Although technology has brought us many conveniences most of them require supporting power or other technology. You seem set on refrigeration and you say: "I am willing to go to just about any extent short of buying a fridge and a generator." Perhaps you should consider solar panels (photovoltaic) and an electric refrigerator. Both technologies are readily available and highly developed. Absorption refrigerators may be less so and they still need a fuel source. (If the refrigerator is well insulated it should stay cold over night if it is not opened.)

A better alternative may be store things that do not require refrigeration, and even your examples are compatible with this:

  • It happens that many people around the world don't refrigerate eggs at all. You may find that undamaged eggs keep just fine for two weeks if stored below ground at a relatively constant temperature.

  • There exists UHT pasteurized milk that may be stored unrefrigerated for a month or more before it is opened.

I believe that hard cheeses can be kept at a cool (cave-like) temperature if tended properly. I'm sure there are many more examples of traditional foodstuffs that do not require modern refrigeration.

Mr.Wizard
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  • Solar Panels... I may consider this in the future when I build a cabin out there, but in the forest; there just is not enough sun light. – Anon Jul 23 '14 at 20:19
  • If you use Powdered milk you'll remove another of your problems – That Idiot Jul 30 '15 at 12:06
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You'll need to do several things:

  • Change your habits and foods
  • Work
  • Combine several techniques

First, you need to more carefully consider the necessity of refrigeration. Refrigerators are used to keep food in a "safe" temperature zone where bacteria is less active, and this requires temperatures close to freezing. Passive cooling, such as root cellars and rivers, only reach these temperatures in extreme environments.

If you need to live in a place without refrigeration, it's far easier to change your habits and preserve foods in a way that requires little to no cooling.

Second, cooling methods that will produce refrigerator-like temperatures require a lot of work. Typically that work is obtained from the electrical grid, but since that's restricted in this case, you get to do the work. Digging a root cellar, carrying insulation, and exposing it at night to a cloudless sky with a clear covering for nocturnal cooling, then covering it if it becomes cloudy, or air flow is too great, etc, etc, etc, require a lot of micromanagement. You can, however, obtain freezing temperatures in may places with such a method. It requires a lot of work on your part though - work that could be replaced by a solar panel and thermo-electric cooler, or a small pedal generator where you can contribute work when it's convenient for you, rather than pay attention to the environment and act on changing conditions to best preserve what little cooling you obtain each night.

There are a number of techniques you'll need to know and use depending on the environment. In a humid environment, evaporative cooling won't work well. In a rocky place you're going to have a hard time digging a hole deeply enough for a cellar. In a windy environment you are not going to be able to use nocturnal cooling.

There's no single, universal method that will work everywhere your question is applicable. Combining methods will become necessary in most cases to maximize cooling.

Adam Davis
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It there is a well nearby use it. 1. by dropping sealed and floating containers to water and then using a net to get them back. This works very well with beer cans. 2. Put the food in a bucket and use rope to lower it near the water.

Kristian
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Because water evaporates at any temperature over 32 DegF, a swamp cooler or evaporative cooler is possible in any climate that needs cooling (though perhaps not in a powerful enough fashion depending on the cooling required). In a still body of water, the evaporation rate is proportional (in some form) to the humidity of the air, the air temperature, the dew point, and the water temperature. Taking all this into mind, here is a simple (unanalysed) design for your consideration:

Dig a shallow trench (the volume of your refrigerator) on the crest of a ridge or hill, or some other location in which you find natural, dry air flow. You will want well insulated walls and floor for this trench, so don't line it with copper plate or anything silly like that. Over the top of the trench you will lay a thin, highly conductive lid like sheet metal. The downward side of this lid should be thinly painted a dark, matte color (to improve radiation from your food to the lid). Once in place, you should poor water onto the lid to create a "roof pond." As the water naturally evaporates from the roof pond into the naturally flowing air, it will cool the chamber underneath it.

This entire pit should be in the shade however, as evaporation due to the water heating from the sunlight will have no benefit.

To create a swamp cooler in this same area, you would need to dig out a (long) channel to let wind into one side of the refrigerator and leave some gaps in the lid for it to escape out the far side, much like a "windcatcher". Pour water into a long hole in the channel, such that the wind flowing into the fridge flows over the surface of the water before entering the fridge. The evaporation of water into the air will drop the air temperature, and you will have cooler air than the outside blowing across your food.

Perhaps the combination of these two ideas would be enough to chill your food to a reasonable temperature? Alternatively, here is a website about passive cooling: http://www.builditsolar.com/Projects/Cooling/passive_cooling.htm#Passive

pheidlauf
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  • This is a great idea. Unfortunately, I am on a nearly completely flat plane. However, being on the coast, the wind does usually blow in a constant direction; could I still utilize this technique? – Anon Jul 25 '14 at 20:25
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    As long as there is a constant wind, the topography of your area shouldn't make a different. I suggested a ridge simply because they often experience constant airflow. All you need is a source of dry air to evaporate water into, whether it comes on flat ground or a hill makes no difference. Also, if you actually construct a permanent chiller, please post here so that we can hear about your results. – pheidlauf Jul 28 '14 at 13:25
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If your ambient temperatures (air/water/earth) don't get down below refrigerator temperatures (2-4 C), and in summer I suspect they don't, then the second law of thermodynamics says you can't do this without an energy source.

Since electricity is out, you could consider a propane refrigerator.

Nate Eldredge
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    You can use the clear night sky as a cold source to get temperatures below freezing -- for thermodynamic purposes, the night sky has a temperature around that of interplanetary space. It requires preventing conductive and convective heat transfer and restricting the directions in which radiative transfer takes place -- a bit tricky, but theoretically doable. – Mark Jul 24 '14 at 09:43
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Ground temperature up to 30 feet deep varies as a function of depth and the seasonal temperature. The further down you go, the more it "averages" the location's seasonal variations and the more it lags the seasonal changes.

Hole in the ground

In southwest canada (vancouver, for instance) you can expect that four feet down the ground will be around 50F (10C). Go further down and you can lower it another few degrees, but for your purposes this should be sufficient for your needs.

In the simple case, dig a hole four feet deep, drop a metal or plastic trash can into it, and then tie a rope to your goods (perhaps a small cooler) and lower them in the trash can. Keep the top covered, and if possible insulated. Lining a sheet of marine plywood with foam insulation on both sides, for instance, and laying it over the top will allow the hole to remain cool regardless of the air currents at the surface. If your area is prone to surface water, keep the top of the can several inches above ground level.

In the more complex case, dig a full root cellar and consider it a walk-in fridge.

If you insulate well, and your can/cellar are in the shade, you may find they maintain temperatures well below the above estimate.

Groundwater temperature

If you use a well for water, then you'll find it gets even colder than the ground immediately below your feet. Find your water pressure tank, insulate it with a small area enclosed in the insulation. Store your perishables in that area, and the groundwater you're pumping up will keep the tank and the enclosed area cool. If you use a thermometer you can figure out how much water you need to use a day to keep it at a reasonable temperature.

Adam Davis
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