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trial solar still

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rorschach
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trial solar still

Postby rorschach » Tue Sep 05, 2017 3:59 am

Hello,

This is a project I have been working on. Cost was about $100 from Home Depot
-
- 1/2" plywood sheet was $25
- clear acrylic sheet 30" x 32" x .080" was $44
...and a few other odds and ends

(I had marine spar varnish already, as well as PL Premium caulking)

Hopefully, the picture will work. Okay, I resized it REALLY small to like 300 kB and it still doesn't upload (what kind of 1990's file limitations are we dealing with here?). I'll try one more time on another program to shrink it more...

Supposedly, a unit like this can collect ~ 2L of H2O per day. If you have a large chunk of land with good solar exposure, you could make 1 or 2 of these per family / group member and theoretically have water processing needs met (assuming you at least have a convenient source of dirty water as input).

Questions or comments?



solar still super tiny res.jpg
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peppercorn
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Re: trial solar still

Postby peppercorn » Tue Sep 05, 2017 8:28 pm

It should work to produce water, though by the size of it I would say not even close to two liters. If it did 500 milliliters I would be surprised. My quess is fully unqualified, just a ballpark estimate.
We are supposed to have hot sunny temps all week so its a perfect time for you to try it out.Use it and measure what it really puts out...I will estimate 250ml to 300ml.....
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Re: trial solar still

Postby peppercorn » Sat Sep 09, 2017 6:43 am

Rorschach...Im dying to know, 5th, 6th, 7th were blistering hot and sunny days,the best conditions you could want. How did your unit perform??
Was I out to lunch? Do I have to recalibrate my quesso meter
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rorschach
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Re: trial solar still

Postby rorschach » Sun Sep 10, 2017 12:08 am

Peppercorn,

Unfortunately, the solar still does not seem to work properly. I'm scratching my head a bit. I looked at several research articles (from places like India and sub-Saharan Africa where they are looking at solutions to the clean water problem) and attempted to follow their designs.

There has been no water output to speak of. Theories / possible problems:

- insufficient sealing of the unit such that too much vapour escapes. However, the "quick and dirty" solar stills that people use in a survival situation (e.g. a pit with a garbage bag over top, with dirt around the perimeter holding the bag in place and a rock or weight in the centre of the garbage bag to weigh it down and make a cone shape) do not seem that well sealed and yet still work. I have a reasonably constructed "box" that is made from 1/4" ply that has 3 coats of marine spar varnish. And I sealed all the edges generously with PL premium. The "door" of the unit is at the front / bottom of the box and is not likely to appreciably interfere with trapping / holding warm vapour.

- problems with the "collecting channel," although it seems simple enough to me, and should be capacious enough to serve as an "eavestrough" to collect the water from the underside of the window sheet.

- improper material for the window sheet. I opted to go for acrylic because it was inexpensive, easy to work with, and I was afraid of an accident involving broken glass (I also have small children at home who could possibly bump into it or knock it). The "angle of inclination" (for lack of a better phrase is about 30 degrees, consistent with the research articles. I am wondering if a steeper angle might be needed for acrylic (c.f. glass). The reason I say this is that whenever I checked the unit after work on those warm days that you mentioned, I noted two things:
- foggy / steamy condensation on the acrylic in general
- a "matrix" of water droplets ... it literally looked like they were arranged in rows and columns. I'd estimate there were maybe 30 droplets across left to right by 50 or 60 droplets forward to back (top to bottom).
I don't know the physics equation that would apply, but I'm wondering whether the adhesion of the water to the underside of the acrylic, combined with the coefficient of friction ... is insufficient to cause the droplets to passively roll / flow down the window to the "eavestrough / collecting channel."

Sorry if that above is wordy. Hopefully, it makes sense.

Any advice would be appreciated.

At this point, it looks like I'm not quitting my day job to mass produce these for anything. :oops:

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peppercorn
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Re: trial solar still

Postby peppercorn » Sun Sep 10, 2017 4:55 am

Your construction looks fine. I think you nailed the problem with this observation..... I am wondering if a steeper angle might be needed for acrylic (c.f. glass). The reason I say this is that whenever I checked the unit after work on those warm days that you mentioned, I noted two things:
- foggy / steamy condensation on the acrylic in general
- a "matrix" of water droplets ... it literally looked like they were arranged in rows and columns. I'd estimate there were maybe 30 droplets across left to right by 50 or 60 droplets forward to back (top to bottom).
I don't know the physics equation that would apply, but I'm wondering whether the adhesion of the water to the underside of the acrylic, combined with the coefficient of friction ... is insufficient to cause the droplets to passively roll / flow down the window to the "eavestrough / collecting channel."

I would bet the drops just kept forming until they were large enough to drop straight back into water supply at the bottom....I would have had about a 50 degree angle myself,maybe 60, even with glass. I don't think there is a downside to a good steep angle, Good news is all you should need to do is when the drops have formed, lift up the back end until the drops start rolling to the collecting trough, then you will know the angle you need
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term0shad
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Re: trial solar still

Postby term0shad » Mon Sep 11, 2017 1:54 am

Built a few. Work fine. Will rebuild again. Let you know how i did angle. All built by eye. I do most by trial and error. Way i learn. I might even have a old one in shop. Will look next weekend. So much shit in shop i can't recall what i have any more.
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