solar water distiller

[Rabrsniver]

I have a countertop electric water distiller which we use to make water for our batteries. We are not able to buy "store-bought" water because of transportation costs.

It is a real energy hog (like most of them) and our batteries are thirsty.

I'm thinking of making a solar powered one.

My questions:

Are they efficient?

Is the water quality good enough for batteries?

I know its related to sun output, but how much product is produced/day on average?

Does anyone have decent plans for a simple unit?

I would appreciate hearing about anyone's experience with these, in order to decide if its a worthwhile project.

Thanks,

John

[cr8zy1van]

Try this link: http://www.thesietch.org/projects/distiller/index.htm I recently bought a roll of that mylar he uses for his mirror off Ebay and it only cost me around $25. I would love to make hot water, or even distill water for purification. He also has a few other projects that may tickle your fancy.



a.

[dnix71]

Here's a video on how to with stuff you already have in the kitchen. The warning at the end about impurities applies to any method of distillation. If the impurity evaporates,  like ammonia or chlorine, and you don't want it in the final water, then you will need an active charcoal filter as the last treatment. Don't add the dirt and grass like he did, that was just for show.

http://www.metacafe.com/watch/723941/solar_water_distiller/

You can use tap water as feed, but if your water supplier adds chlorine, ammonia or chloramines for disinfectant, then letting the water sit in the fridge for a day or two in a lightly covered glass jug should allow most of it to air out.

[ghurd]

How thirsty are those batteries? (!!!)

Seems like $20 total in PVC, spray paint, maybe a bit of thin plywood and aluminum foil, maybe copper tubing or old computer heat sinks, should make more water than batteries could use.

"experience".  I lost about 2.5 quarts of rain water in an open white bucket exposed to the sun about 3 hours a day in the last 5~8 days.  It is between our home's shadow and the next home's shadow.

NE OH and about the last 7 days.  And it rained in the bucket too.

G-

[Rabrsniver]

Thanks for the links.

 The batteries are NiFes, and 20 of them (1.2v each) usually use about 2 gallons every week and a half. A lot more than my old Trojans, but other than that I am happy with them.

Any other links would be appreciated.

John

[Norm]

I have a plastic tablecloth on our picnic table

every morning I could squegee about a half cup

of water....something like this on a larger

scale??

   maybe not...just a passing thought...

but it is distilled water

[zap]

Here's one of the simplest I've seen.

http://www.i4at.org/surv/sstill.htm

[Ungrounded Lightning Rod]

A simple device for automating filling and cleaning it out would be to replicate how swamp coolers are kept clean:

 - Inlet controlled by float valve.  (Ala a toilet tank.)

 - Brine pumped out by a little pump with a timer that runs for a few minutes each day.

[ghurd]

That's a lot of battery water.

I do not believe many solar stills are well though out.

To condense water from air is easy.  A glass of ice water does it because it is cooler than the air.

Most solar stills are at nearly the same temperature over the entire unit.  There is not much more reason to condense than there was to evaporate.

It would work better if the unit had a cool area.  That should not be difficult.  

The area where the condensation is collected can be shaded.  

Possibly some kind of simple heat sink, even extend it into the cool area.  Back to back CPU heat sinks with one inside and one outside?

Possibly evaporative cooling of the cool area.  Wrap the area in denim, keep it wet with wicking action or a slow drip, maybe supplied from one of those automatic dog bowl fillers that use an upside-down 2 liter soda bottle reservoir?

Simple idea, just for the concept.  4" PVC in an "H".  Cross piece slopped down toward the cool side.  1/4" plywood between the vertical sections to provide shade.  Paint the hot side black, maybe add a horizontal trough in the vertical piece at the lower edge of the horizontal piece.  Maybe add some cooling to the cool side.

Evaporates from the hot side, condenses in the cool side.

I expect the solar still in Zap's link would work better if there was no insulation over the short side, and maybe it could use some kind of heat sink on the end or lowest 3" of glass (wet denim?).

G-

[Ungrounded Lightning Rod]

In zap's example the cooling is provided by the ambient air cooling the glass as the water condenses on it.

It might work better with a piece of thin plastic sheeting in place of the single-pane of window glass.  (Though there would be a larger risk of tearing from environmental hazards or deterioration of the plastic sheet by sunlight, followed by contamination of the allegedly purified water by dust.)

Indeed, an emergency drinking water still can be made with a sheet of plastic, an empty can, a hunk of tubing and a digging tool:

 - Dig a hole.

 - Put the can in the middle of the hole with the tubing "drinking straw" in it.

 - (If it's really dry or you're in a hurry, cut up some vegetation and leave the chunks in the hole.)

 - Cover the hole loosely with the plastic, weighting it down with rocks around the edge and sealing it with dirt.

 - Put a little sand or a small stone in the middle so it dips down with the lowest point over the can.

Sunlight evaporates ground water and/or water from the vegetation and creates a warm and humid environment in the hole.  The plastic is cooled by the ambient air and moisture condenses on it.  It runs down to the low spot and drips into the can.  You can typically get enough from a three-foot diameter hole to keep one person alive indefinitely.

Similar things can sometimes be improvised at sea.  (By the way:  You'll last longer drinking sea water than not drinking, and can use it to stretch a small supply of fresh water by a bunch.)