Cellulose, suitably mixed with a binder can be moulded into jars, which can be used to store water when you're out camping. The cellulose contains micropores, which allow extremely small amounts of water to percolate through the walls of the jar on to the surface. Heat exchange takes place at the surface, resulting in the permeated water getting evaporated, and the water inside the jar staying cool. No electricity used, and a nice eco-friendly way to have cool water any time you want some.
-- Brahma, Aug 04 2009

Well, seeing as the purpose of a jar is to contain the water, you're definitely thinking outside of the box. One problem you will come across is the coefficient of heat transfer for cellulose. I will guess that it is quite small, as it typically is for polymers, meaning that the stuff doesn't like to transfer heat. So, all that cool you got on the surface will do it's thermo thing with the air and not your contents, taking the path of least resistance and such. Even still, just because you evaporated some water doesn't keep outside heat from transferring to your unevaporated water. If there is an excess of heat it will make its way into the water faster than the evaporation can cool it down, again leaving you disappointed. All the same, it's a fun idea, in that 'oh shit, everything in my bag is wet' sort of way.
-- daseva, Aug 04 2009


Baked in ancient times: unglazed pottery jars do exactly this.
-- pocmloc, Aug 04 2009


Yes - but they're heavy, and easily dmaged. The idea is not wihtout merit. What about an aluminium vessel incorporating carbon nanotubes to give controlled porosity ?
-- 8th of 7, Aug 04 2009


Leather or canvas water pouches or skins work vary well for this .

The canvas stays cooler but has higher watter loss, leather not as cool but less water loss pick what fits the situation.

though both will eventually rot out and need to be replaced.
-- dev45, Aug 04 2009


"If there is an excess of heat it will make its way into the water faster than the evaporation can cool it down, again leaving you disappointed."
Might be self-regulating. As the water inside heated, more would seep out, cooling it back down again.
-- phoenix, Aug 05 2009


you need a fair bit of surface area so something ... right; canvas or leather... hmm... wonder if covering a house in canvas and periodically soaking it with the hose would prove a good method of summer cooling.
-- FlyingToaster, Aug 05 2009


Also note this won't work in high humidity environments.
-- Custardguts, Aug 05 2009



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