Hi,
Sometime ago, in order to give my students an idea of what to expect from a solar still I conducted some experiments. These were done at an altitude of around 1800ft above sea level. The area is definitely not dry, but at the time it hadnt seen any rain for about a month and a half. When I introduce the solar still to my students I make it a point to tell them that it is at best a stop gap measure. you cant depend on it to keep you alive. The experiments seem to prove it. Unfortunately I had no way of measuring humidity.
Size of pit.(inches) Cloud cover (scale of 1-10) Time elapsed Quantity of water.
36x36x18 less than 1 4hrs 93ml
20x20x20 1 6 40ml
36x36x18 1 6 111ml
36x36x18 3 6 80ml
36x36x18 6 6 52ml
20x20x20 3 6 42ml
20x20x20 6 6 14ml
These results are pretty poor. But I found that any muddy(undrinkable) water poured into the hole before sealing it up increased the results by about three fold.
Along the coast I also discovered that if you dump several buckets of sea water into a pit the resulting water from evaporation is drinkable although it tastes slightly brackish. Fresh vegetation added to the hole, also increases the output by as much as 60%. Cactus (optunia) chopped up and placed in the pit also boosts output by 50 70%. Water tastes slightly bitter.
I have tried these experiments over and over and am still doing them from time to time when ever I go to a new area. But overall the solar still does not seem to give me good results when weighed against the energy expended to make one. Especially if the ground is hard. (digging was done with a sharp stick and knife to simulate a survival situation and took about 2.5hrs.)
The results of collecting dew off vegetation were much, much better. The best was 300ml with just 3 swipes with a 1x1meter bandana. (up in the mountains)
Transpiration from trees also yielded poor results. I suspect the size of leaf, composition etc plays a role in this. I am continuing with experiments as and when possible.
Ill be glad to hear your experiences, thoughts and suggestions.
rgds
