Natural Refrigeration

There is a fairly simple method of creating food refrigeration and food freezing, without any need for electricity or freon refrigerants.

It is entirely dependent on a basic scientific Law, that of Ideal Gases.

We will discuss several alternatives, which are dependent on the local climate and the season, along with a fourth distinctive version which is described in the Self Sufficiency page. That variant can be used in any climate on Earth, but it REQUIRES using something like a Savonius Rotor windmill for power to drive the crude compressor it runs on.

The three variants described here are very similar. The first is extremely crude, and it is only useful in Temperate Climates, and often only during winter.

Consider digging a pit, at least six to twelve feet deep and deeper for equatorial climates. Essentially make this pit into a crude Cistern, pretty much just making it waterproof. Around the Chicago region, soil deeper than about six feet deep is NEVER warmer than about 52°F. A rope and pulley like at the top of an old water well, could have an endless loop rope. Maybe 12 or 20 five-gallon-pails could be hung along that rope. They might contain butter, vegetables, milk, cheese, each LABELED on the outside! So any time you need cheese for a meal, just go to your 'Natural Refrigerator' and pull on the rope to cycle through the various 5=gallon-buckets until you get to the foods you need for this meal!

If 20 such buckets COULD be hung along the rope loop, leave about four of them off, so you have 16 containers of food down in your refrigerated system. The reason for this, and for regularly oiling the bearings on your pulley, is so that when you are done accessing food, gravity will take over and move the buckets deeper down. Only the very top four would not be there, due to gravity, and that is where it would not have been as cool. Find an old water heater, one where the tank does not leak. Attach standard iron water piping to the two pipe fittings on top of the vertically positioned tank, marking them so you know them apart.

Plug off all other water fittings, and bury the tank completely, vertically.

An automatic air valve is necessary, to open and close different airpaths. You will need a source of SLIGHTLY pressurized air. An air compressor generally needs at electric motor to run it, but a Savonius Rotor windmill could also power it.

For an example, say that we are considering the Chicago, IL, USA climate, and we are going to consider a warm summer afternoon. The deep soil temperature in that climate is ALWAYS at about 52°F (or 11°C).

This configuration cannot use the naturally cool deep earth to provide cooler than about 52°F, which is not cold enough for a Freezer and not really cool enough for reliable refrigerating. Again, this really relies on COLD WEATHER to provide cool enough local air to supply the appliance.

For the crudest configuration, a minimal fan or blower blows WINTER OUTDOOR AIR through a duct which has an insect filter. Two possible destinations for that cold air are possible. IF the outdoor air happens to be colder than 25°F, the cold air can be sent into a FREEZER COMPARTMENT, even inside an existing (unplugged) refrigerator. That freezer compartment HAS a thermostat which would have turned on the refrigerator's compressor if the freezer had warmed to above a chosen temperature (which you can set) but it now turns on a tiny electric fan or blower to send NATURAL COLD OUTDOOR AIR into the freezer as necessary. The other destination for your cold outdoor air could be into the REFRIGERATOR COMPARTMENT of the appliance. It has its own separate internal thermostat, where you may adjust it to about 40°F. Again, traditionally, that thermostat would normally have turned on the appliance compressor to create cool air to supply the refrigerator. However, we re-wire that thermostat to turn on and off a fan or blower in a duct of cold outdoor air.

During the winter, in cold enough climates, this arrangement can supply accurately cold air in the FREEZER and accurately cool air in the REFRIGERATOR. No compressor ever needs to run to use up hundreds of dollars of electricity!

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But that FIRST configuration is limited by the outdoor temperature being cold enough. In warmer seasons or in warmer climates, this configuration may often not work, and the more sophisticated SECOND or THIRD configuration may be needed.

Both of these PRESSURIZE the buried tank, to use an effect of the Ideal Gas Law of science. In one case, the tank is filled with AIR and in the other case, it contains mostly water.

You use the compressor to pump AIR down into the (wrong) pipe which normally supplies hot water to a house, and we will say you use very moderate compressor pressure of 15 PSI. The ambient afternoon temperature is about 85°F, which is 544°R (Reumer or Absolute). Because of the Ideal Gas Law, and the fact that we have DOUBLED the pressure (P) of the compressed air, that means our compressed air would heat up to DOUBLE the temperature (T) (in absolute) so the air has heated to nearly 1088°R, which is 629°F. REALLY hot air!

The entire buried tank soon is filled with air which is compressed at 15 PSI and very hot due to that Ideal Gas compression temperature. But the WALLS of the tank are in contact with ground that is always at 52°F. So the air inside the tank soon COOLS down to near 52°F!

If this compressed and cool air was ALL SUDDENLY RELEASED (through the other pipe) the Ideal Gas Law would act again, but now to COOL the air down to HALF its Absolute temperature. In other words, it would cool from 408°R down to 204°R. This would be incredibly cold, or NEGATIVE 256°F!

Only a small dribble of released air would be needed to SLIGHTLY reduce the pressure, so that the released air might be at 20°F (to be released into a FOOD FREEZER) or 40°F (to be released into a FOOD REFRIGERATOR.

Two holes would need to be bored into an insulated box (such as a failed standard refrigerator), one to let the cold air INTO the refrigerator box and the other to be able to bleed out warm air out of the refrigerator (without the added pressure pushing the refrigerator door open!)

A $12 thermostat, or possibly the thermostat control which was already in the failed refrigerator, is then used to modulate the pressure release valve in the pipe from the buried tank. A separate PRESSURE REGULATOR (from an old car engine or many other sources) would turn the compressor on to maintain the pressure inside the underground tank.

Please note that this is therefore ALL AUTOMATIC, exactly like the way an expensive refrigerator works!

Note that there is no actual reason to use 15 PSI pressure, and even a bellows can produce sufficient pressure to create the desired refrigeration, using very low pressure. The value of using a substantial pressure inside the tank (such as the 15 PSI) is to store MORE coolness! Even 2 PSI or 3 PSI works fine! (With your mouth, YOU can produce air pressurized at about 1 PSI easily!)

The third variant is the same but where about half the buried tank is filled with a mixture of car antifreeze and water. The tank still is compressed with air from a compressor at the 15 PSI or whatever pressure, and the cool soil surrounding the tank cools that hot air and also the water-antifreeze in the tank. There are only two reasons for this variant. First, the AMOUNT of coolness which can be sent up into the refrigerator (per minute) is much greater by sending WATER instead of air up, because water has a much greater thermal conduction coefficient, which lets you use smaller diameter PIPES to transfer the coolness. Second, the AMOUNT of coolness inside the buried tank is much greater than if it were just air, which enables much more effective freezing and refrigerating. However, even though you can use smaller diameter pipes to transfer the coolness, you need an extra component, a 'car heater radiator' to transfer the coolness to the air inside the appliance.

If you use the water-antifreeze mixture inside the buried tank, depending on your climate, you might also be able to add a conventional car radiator and a 12-volt car heater blower, to provide actual house air conditioning for part or all of your house. You could also bury more old tanks to provide all the A/C that your entire house needs, ANYWHERE ON EARTH!

This presentation was first placed on the Internet in June 2014.

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Carl W. Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago