Last night at the yacht club, the Sea Scouts gave a demo on a homemade
water still where they put a can of salt water into a clear plastic
bag. Evaporation then condensed on the plastic and flowed to the
bottom as fresh water.
Now, Evaporation goes much faster as temp goes up and with surface
area. So, I propose a simple inflatable Compound Parabolic
Concentrator (google it) type optic with a container at the area of
maximum solar flux. This container would be permeable so that salt
water could wick through it and be evaporated and then run down the
plastic to the bottom. This might even be more useful than commercial
RO devices.
Once I saw a water container in St Augustine made by the Spanish in
the 1600s from permeable coral. They put water into it and water
wicked through it and evaporated causing the water inside to become
cooler. I could not ascertain its effectiveness because the museum
had it in the shade out of the wind too.. Perhaps one could make
something like this from modern lightweight materials.

On Jun 8, 1:00 pm, wrote:
Last night at the yacht club, the Sea Scouts gave a demo on a homemade
water still where they put a can of salt water into a clear plastic
bag. Evaporation then condensed on the plastic and flowed to the
bottom as fresh water.
Now, Evaporation goes much faster as temp goes up and with surface
area. So, I propose a simple inflatable Compound Parabolic
Concentrator (google it) type optic with a container at the area of
maximum solar flux. This container would be permeable so that salt
water could wick through it and be evaporated and then run down the
plastic to the bottom. This might even be more useful than commercial
RO devices.
Once I saw a water container in St Augustine made by the Spanish in
the 1600s from permeable coral. They put water into it and water
wicked through it and evaporated causing the water inside to become
cooler. I could not ascertain its effectiveness because the museum
had it in the shade out of the wind too.. Perhaps one could make
something like this from modern lightweight materials.

The problem I see with most solar stills is that the evaporated water
collects on the same membrane on which the sunlight is passing thru.
Most of the desired sunlight is IR and water is not too transmissive
of it. If one kept the condensed water from the light path it might
be much more effective.

On 2008-06-08 13:00:36 -0400, said:

Once I saw a water container in St Augustine made by the Spanish in
the 1600s from permeable coral. They put water into it and water
wicked through it and evaporated causing the water inside to become
cooler. I could not ascertain its effectiveness because the museum
had it in the shade out of the wind too.. Perhaps one could make
something like this from modern lightweight materials.

When I was a scout about 40 years ago, we had "Lister" (spelling
strongly suspect) bags that did just that. The water kept the canvas
sides damp, the wind evaporated the water and cooled the contents
slightly.

A variation of that put a can of water above a sack draped over some
shelves. Worked somewhat as a camp refrigerator.

--
Jere Lull
Xan-à-Deux -- Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/

On Jun 8, 10:37*am, Jere Lull wrote:

When I was a scout about 40 years ago, The water kept the canvas
sides damp, the wind evaporated the water and cooled the contents
slightly.


Maybe a "Desert Bag" hung on the grill of your dad's 1948 DeSoto

Bob