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Absorption fridge : How to adapt for no gas or electric ??

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  • Absorption fridge : How to adapt for no gas or electric ??

    An 'absorption' fridge, the 'RV' type that happily runs on 12 V, 110 / 220V or 'propane' tank, uses a heat source instead of a pump. Boils ammonia in water solution. Cooled ammonia gas chills cooled water when re-absorbed else-where in system...

    The tech is really, really clever, but could a generic 'absorption' fridge be adapted to use heat from an 'Aga'-type stove / cooker or solar concentrator ? Perhaps using a 'heat-pipe' or thermo-syphon to transfer heat ??

    Alternative, beyond wind / PV / water generation for sundry Watt-hours, would be a small gasification plant, cooking wood etc to get a gas mix to burn. Sadly, with potential sooting problems...

  • #2
    Before we decided to move here permanently, we had a 29'-6" RV. Using propane the absorption fridge barely sipped propane. The heat source to boil the ammonia is a smaller than a natural gas kitchen stove's pilot light.

    As many tail wagger (towed) camper owners learned, running an absorption fridge off their vehicle's battery would drain the battery overnight. Some pickup trucks have 2 batteries, one starts the vehicle and the other powers the camper.

    A solar panel(s) to charge batteries is an easy solution as is wind power. If running water is available, a water powered Pelton wheel (impulse turbine) to generate electricity is another option.
    The caveat for solar is battery life is finite as is how much propane. The only free cheese is in a mouse trap. LOL

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    • #3
      Given the modest power draw, plus the fridge acting as its own 'storage battery', a vertical axis windmill may well be the simplest 'renewable power' system. As current is going to a purely resistive load, don't need much 'regulation'. A brushless stepper motor plus poly-phase diode bridge would probably suffice. Preferably with motor bearings not taking wind-loads, so flexible drive. Really, an up-scaled version of crank-charged torch. Add a modest solar panel for clear, windless days...

      My query is more about retro-fitting an absorption fridge to sip heat from eg an Aga-type stove. SHTF scenario...

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      • #4
        If SHTF would happen, keeping it very simple would be best.
        A windmill needs a propeller to generate electricity. How available an efficient propeller would be is the question.
        As every vehicle uses tapered roller bearings at each wheel and they handle radial and thrust loads effectively. They are very available.
        Depending on one's location, electronic component availability is another question.

        Adapting an AGA-type stove's element to replace the absorption fridge's pilot light would require matching the pilot light's temperature. A temperature measuring "gun" is one solution; if, its accuracy is sufficient.

        When we camped, I was curious how the RV's fridge worked.
        https://www.arprv.com/image-arp/how-...unit-works.png
        The image states a "calibrated heat source" based on that, it appears regulation would be required at what degree of accuracy and its ± tolerance is the question.


        I did a search for the AG-stove's power requirements and came up with this:
        https://www.tncook.co.uk/AGA_electri...as_supply.html
        Because they sell stoves, the amperage requirements for one heating element is not defined. The easiest way would be measure the amperage draw for one element burner at the same temperature as the "pilot" light. As the "pilot" light is quite small in size; the size of an AG-stove's element might be detrimental?

        There are other methods of producing heat which might be in an more appropriate size and capable of the "calibrated heat source."









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        • #5
          Nik... I didn't know what the heck an AGA stove was. I've never heard of it so I had to look it up. Interesting and long tried method. I did see one item on their site that mentioned the oil units would consume 40L (~10.5gal) a week which does seem like a lot. from an efficiency standpoint it seems much conservative to only use an appliance when absolutely needed. When I think of how long I could run 2 or 3 camp stoves on 10.5 gallons of fuel, it doesn't balance out to me. I get it's a different style cook but in a grid down situation resource management will be critical, I don't know. But then I guess that's why you mention the electric version would then make the most sense. I'd agree a small vert axis mill might make most sense and lots of improvised things to make a similar sort of set up.from using barrels or pipe to catch the wind to car alternators being used as the generator. https://www.cooksinfo.com/aga-stoves

          Do they still manufacture these? I see it says most are electric so I'd be interested to see how that works. I see it mentions the ovens are completely cast iron which made me think cooking similar to a dutch oven. It must use low wattage heating elements embeded into the outer shell of each oven chamber? Then each is independently set at a certain percent power to maintain the individual temps. What temp does the ammonia solution in the fridge need to reach to boil? I didn't quite get how the hot plates are used.

          But to the original point of the fridge side, another idea I saw as I was looking up vids on the AGA and the absorption fridge was a guy using a solar refactor as the heat source on the boiler chamber. So there is another idea during daylight. Another key focus would be adding additional inches of insulation to all sides of the fridge to try and super insulate to make the cold stay longer.
          I can explain it to you, but I can't understand it for you!

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