So, I have put a bit of thought into the concept outlined below, and ended up posting it in another thread a couple of days ago. Since there hasn't been any movement on that thread, I am re-posting it as a seperate topic because I very much would like to hear any comments.
I realise that air conditioning an off-grid home might seem frivolous to the most committed permaculturists out there, but I am trying to think of ways to make more sustainable living appealing to a wider segment of the population who might not be willing to sacrifice comfortably interior temperature (especially in hot climates which try the limits of passive cooling).
The orrigional thread-starter's question was about using a rocket stove as a heat source for an absorption chiller.
Marcus Zed wrote:I have been thinking about this recently for my own use, and here is what I came up with:
An absorption chiller (water/lithium bromide) DOES NOT USE HEAT TO COOL, it uses vacuum to evaporate the refrigerant (water), a dessicant (lithium bromide solution) to absorb the water vapor in order to maintain the vacuum, and heat to re-concentrate the dessicant by boiling off the water.
In commercial systems, all of this usually happens simultaneously (so that you need heat to run the system as well as power for the pumps), but there is no reason that it needs to.
If you retrofitted a small absorption chiller with a VERY LARGE dessicant storage tank and very large used dessicant tank, you could use heat whenever it was available to reconcentrate dessicant, even if your system was not cooling at that time. This heat could come from whatever stove you use for cooking/baking or other process. Because the system is primarily plumbing, you could put the cookstove, dessicant boiler, and dessicant storage tank in a seperate building with little difficulty, thermally isolating it from the building you are trying to cool. The commercial systems I have looked at feed dessicant at low pressure, so elevating the bottom of the tank a few feet above the evaporator could give you all the pressure you would need.
In order to actually run the evaporator and circulate the chilled water requires electricity. If you found appropriate DC motors, this part of the system could be run directly off of a modest-sized solar panel directly without the losses from an inverter or battery storage.
There should be a thermal mass wall completely shaded within the building to be cooled (I doubt you EVER really wasnt solar gain in south Florida). The wall should be as tall as you can make it, and can include the convection tubes described above.
Each component of the system works whenever the necessary energy source is available.
Whenever you cook or bake, you are also re-concentrating dessicant.
Whenever the sun is shining, you are pumping refigerant and dessicant to produce chilled water which is circulating through your heat-sink wall and cool it.
Whenever the interior temperature of the house is significantly above that of the heat-sink wall, the passive convection design will draw that heat back into the heat sink.
There is no reason that these processes have to take place at the same time, since the concentrated dessicant stores the value of the heat in chemical form.
<span xmlns:dct="http://purl.org/dc/terms/" href="http://purl.org/dc/dcmitype/Text" property="dct:title" rel="dct:type">Concept for off-grid absorption cooling</span> by <span xmlns:cc="http://creativecommons.org/ns#" property="cc:attributionName">Albin Marcus Zuech</span> is licensed under a Creative Commons Attribution-ShareAlike 3.0 United States License.