Tuesday, January 1, 2013

Off Grid Refrigeration

This article was written by Tom Chatham and originally published at Project Chesapeake
One of the hardest things to go without when going off grid is refrigeration. Most other operations can be replaced by manual means but keeping food cold or frozen in hot weather is a unique need in modern times. In times past the need for refrigeration was limited because most food was prepared fresh every day and very little was kept for several days due in part to the lack of mechanical cooling. The fast paced lifestyle many now live have led people to depend on frozen or refrigerated food due to the modern day work habits leaving little time for home preparation of food. In times past most women worked in the home all day, so daily preparation of food was a natural occurance. With most women working outside of the home nowadays, the fast preparation of food dominates most kitchens. Even for those that do a lot of cooking from scratch everyday, the use of frozen foods is very convenient.

The ability to raise your own meat, butcher it, and save it for later use on a moments notice has been nothing less than revolutionary in the kitchen. While freezing is not the only way to save foods, it is much easier than other methods for many foods. The biggest problem with frozen foods is the need to keep it frozen at all times. When the power goes out many people lose the contents of their freezers because of lack of electricity. Even after this happens several times most people continue to use the same means to keep their food refrigerated and never give thought to using a different method that would save them that loss and provide them with frozen food and ice no matter how long the power was off.

The use of propane refrigeration is a step above compressor driven units for several reasons. Many absorption refrigeration units can run on 12v, 120v and propane power. A refrigerator that can run on all three, such as the units found in RVs or camper trailers, can give you an edge when the power goes out. You could run it on 120v for normal operations and if the power fails you can switch over to 12v battery power or to a propane tank outside your home. Absorption units are powered by heat so as long as you have a heat source they will continue to cool. Another great thing about these units is the fact that unlike compressor units that have many moving parts that can break or wear out, an absorption unit has no moving parts in the cooling unit.

Absorption freezers use mostly propane, except for a few of the very small units, so having a propane freezer and a large tank can provide you with continuous refrigeration no matter what the weather does to the power lines. With no need for electricity, propane is a natural fit for off grid living. It can be expensive to fill the tank but the minimal amount of infrastructure you need compared to electricity can offset the expense. A bonus when using propane is the fact that you can use the same tank to power a generator, fuel a stove, heat your home, provide light and provide hot water. It is the best all around fuel source for off grid that you can get. Your propane appliances will continue to run when electrical systems may be disabled. The only problem with propane is the fact that you cannot produce it yourself.

A possible replacement for propane in a catastrophic situation would be the use of bio-gas that you can produce yourself. A digester that can produce bio-gas from livestock manure is fairly simple to build and can enable someone with livestock to produce small amounts of gas to provide fuel for refrigeration and possibly cooking. This is a sustainable solution to off grid power that requires minimal equipment.

Another alternative fuel would be wood gas. This is a good all around fuel that you can produce yourself that operates similar to propane. It can be used for many different items such as generators, lighting, refrigeration and even running an automobile. In days past, town gas was produced from coal and provided lighting and cooking gas prior to the advent of natural gas and propane. To run an absorption refrigerator on wood gas would take some experimentation to get the proper adjustments but it can provide you with a non-electric option in a long term catastrophic situation.

A different type of fuel to run an absorption refrigerator is kerosene. Some kerosene units are available today and use a 2.5 gal. tank that will run for about 10 days on a fill. They use a burner found on some types of Aladdin lamps to provide a heat source. With some experimentation it might be possible to run it on alcohol that you produce yourself. This would give you another option in a long term non-electric situation. About 100 gallons of fuel would last you about a year and kerosene will store for up to 10 years giving you plenty of time to use a large supply.

What if something happens to the power grid and electronics and they never return and you don’t have a propane refrigerator or freezer? How would you provide refrigeration even in a limited way? The answer might be an icy ball cooling unit. These units were first produced in the 1920s and are about as simple a cooling unit as you can possibly make. They are filled with ammonia and water and are charged by heating them over a small fire. The unit is removed from the fire and allowed to cool. When it cools enough for the ammonia to begin recombining with the water you place the coolant end inside a chest that contains your food. The unit will cool for about 24 hours then you repeat the process. The factory units that were sold even had a hollow space in the cooling ball that would allow you to freeze a tray of ice. These units require some labor and time every day but they can be homemade and can provide you with refrigeration when nothing else is available.

One other cooling system that operates similar to an icy ball uses Zeolite which is non toxic. Zeolite is used in the self cooling beer kegs that you can now get. A self cooling beer keg will keep 20L of beer at 41 degrees for 12 hours and can be recharged by heating it up. Water is kept in one chamber and Zeolite powder in another. When a valve is opened between them the water vapor which forms in the vacuum migrates to the Zeolite and as it gets absorbed it causes the water to cool in the other chamber. This would be a good project to make at home from scratch and is much safer than an ammonia system.

A simpler cooling device is a watertight metal container that is loaded with items to be refrigerated and lowering it into a shallow well until the bottom few inches of the container is in the well water. The water will keep the food items at the same temperature as the water which stays about 55 degrees year round.

A simple cooling device used in third world countries is the pot in a pot. The bottom few inches of a clay pot is covered with sand then a smaller clay pot is set inside the first one. The area between the two pots are filled with sand to the top. Water is poured into the sand until it is completely saturated then food is placed in the inner pot and a lid is placed on it. Evaporation will cause the inner pot to remain cooler than the outside air helping to preserve the food.

Hopefully this information will provide you with some ideas to think about if the situation prevents the use of compressor driven refrigeration in the future.


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