Solar Water Distillation

[NAPOTS]

are there any solar water distillation units on the market? I got the idea a while back when I was studying solar power and learned about parabolic trough power generation. The idea is you would have an array of paraboilic tough mirrors oriented vertically with clear tubes of water in the line of focous and the sun would boil the water, you would then condense the steam and have potable drinking water. you could even run the steam through a small generator and make power along the way. This way you are not relying on filters or chemicals for clean drinking water. you would probably size the tubes based on your location and the rate you could produce water would depend on that but you could run it all day. It could even have a feature to track the sun for maximum efficiency.

[JTHunter]

Don't know about the "solar still" but you wouldn't want to drink the water that comes from the steam used on a generator. You would have no way of knowing if there are microscopic metal fragments or oils & greases that lube the turbine/pistons. Not a good idea.

[HDR]

Better to buy unscented bleach and find a stream.

Obviously that would depend on where you live as to whether bleach has a chance to purify the water or not..

[NAPOTS]

I was hoping much like an alcohol still you'd know you were boiling off only water by the temperature. And probably much like an alcohol still you would throw out the first few ounces and last few ounces. You'd leave any heavy metals and minerals behind and the boiling should kill anything. The ones they use for power generation use a heat transfer fluid, and a heat exchanger to flash the water to steam, you could do something similar depending on the capacity of the unit, run an oil in the reflectors and have a primary stage to make steam for power and a secondary stage to make steam for water distillation, each circuit would be independant and sealed.

[El Jefe]

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

[HDR]

Interesting and informative site; some of the links are broke; so don't give up.


http://www.thefarm.org/charities/i4at/surv/

[HDR]

Interesting and informative site.

http://www.thefarm.org/charities/i4at/surv/

some of the links are broke; so don't give up.

[Bick_Sastard]

Oh my freakin god!

These are NOT distillation units!

There is a HUGE difference in a condenser and a distillation unit and the simple fact is, the difference is indeed life and death when it comes to drinking water.

[NAPOTS]

Crap, I like that better than what I had in mind.

[El Jefe]

Oh my freakin god!

These are NOT distillation units!

There is a HUGE difference in a condenser and a distillation unit and the simple fact is, the difference is indeed life and death when it comes to drinking water.

Not sure I follow. The one I linked to are using solar energy to evaporate water and giving you a method of collecting it. How is that not distillation?

[Bick_Sastard]

Not sure I follow. The one I linked to are using solar energy to evaporate water and giving you a method of collecting it. How is that not distillation?

You have actually said it very well, it EVAPORATES the water and then CONDENSES it. This is very much different than distillation.

When you go out to your car in the morning and there is "dew" on the windshield, that is because the glass did not warm up as fast as the air aka it remained "below the dew point" this is in direct relation to the humidity. At any given temperature there is a maximum amount of water the air can hold in vapor form the realative humidity is a refrence to how much is in the air in contrast to how much is actually in it. The dew point is the temperature at which the water would precipitate out (condense) aka rain is called precipitation.

This is important to note. The reason it is important is the panels simply warm up the air/water mix that is in between the base of the panel and the glass to raise the dew point and the glass is cooled by the air outside the panel keeping it below the dew point. For a lack of better terms everything has a boiling point and the water in this unit is being evaporated not boiled, this is not good. While the site refrences "hot" water, hot is a releative term and while the sun may indeed make it hot enough you do not enjoy touching it, that is only around 125-130 degrees. If it does not get the water over 160 degrees it is not going to kill what you want killed for human consumption.

Next comes the glass it is condensing on, the glass is not going to be over 160 so the water on the glass will indeed be cooler and since it is going to be below 160 it is going to foster growth. Significant growth, in effect it is a giant petri dish which is used to grow bacterias and viri.

The other concern is water is an azeotrope for many things, I do not know your back ground in the sciences, but that basicly means you simply can not fully seperate the water from some substances, some alcohols, acetone, antifreeze etc. There is enough polution in the air now days it is not recommeneded to eat snow or drink rain without filteration with good reasons.

I do hope you take my words at least serious enough to research it yourself, I know we had a fuss over Joe but I wish you no ill will what so ever and would never recommend the use of this for drinking water as it is not a distillation unit.

[El Jefe]

I didn't realize that to be considered actual distillation it had to boil. Interesting.

But why couldn't one drink water from the solar unit assuming everything was clean to start with? I haven't read that deal in a good while, but wouldn't it be like drinking water out of the dehumidifier I have in the wood shop? Meaning that as long as the collection surfaces are clean you should be good to go, not?

I should add that I would personally treat water collected in these ways with bleach.

[Bick_Sastard]

I didn't realize that to be considered actual distillation it had to boil. Interesting.

But why couldn't one drink water from the solar unit assuming everything was clean to start with? I haven't read that deal in a good while, but wouldn't it be like drinking water out of the dehumidifier I have in the wood shop? Meaning that as long as the collection surfaces are clean you should be good to go, not?

I should add that I would personally treat water collected in these ways with bleach.

Temps above 40f will foster growth, sanitizing the collector glass and water would indeed handle the bugs, but no not the same as the dehumidifier, the air in your house is likely far cleaner than the air outside, especially if an air borne illness starts spreading.

[El Jefe]

Temps above 40f will foster growth, sanitizing the collector glass and water would indeed handle the bugs, but no not the same as the dehumidifier, the air in your house is likely far cleaner than the air outside, especially if an air borne illness starts spreading.

Are you referring to something naturally occurring, or is something more sinister your concern. I'd imagine if the balloon does indeed go up, that a lot of people will get caught short on water. I know here it's against city ordinance to sink your own well, and if the city supply is interrupted you're going to have issues, or most would.

[Bick_Sastard]

Are you referring to something naturally occurring, or is something more sinister your concern.

Talking about both actually. There are only really two effective ways to handle drinking water, heat or chemistry. They call this thing a distillation unit, its not, they refer to it as getting hot, it does not get hot enough, and that just lends itself to a serious concern as some folks might well not understand.

Hell a simple bug causing the shitts if medical care is not availible. Water distillation is a fantastic way to make it safe as long as you are indeed distilling it at a temp over 180 degrees. High production distillation units are not really hard to manufacture as long as you keep the pressure very low with 0 psi preferred.

There is a lot of things in water, even natural water that can cause problems in a distillation unit, but making one that could produce significant quantities of water per day would not be outside the layman's abilities, the real issue is fuel to run it. Your not going to harness enough of the suns energy to effectivly drive it aka "prime mover" and i would expect that a home built still would be about 30-35% efficient. It takes about 1115 btu's of heat to boil 1 pound of 70 degree water to steam to recondense purified. This will give you at 100% efficient about 540 pounds of water from a 30 lb propane cylinder, factor the heat lost and you can expect roughly 180 pounds aka 21.5 gallons out of the jug of propane.

If you live in a standardish home in your area aka 1500sq ft, single story with a basement, that same jug of propane would run your homes furnace for 5 to 10 hours depending upon the size of the burners in it.

The real issue surrounding it is purity level, distilled water purity is not as dependent upon the equipment as it is the feed water. If there are similar boiling point products in it, they will not seperate, if they are azeotropes you will not seperate them, they have to be "cracked" which is a somewhat simple while complex process, the best way to descibe it is "multistage distillation" though that would be technicly ingorrect.

You sound as though you have done a bit of research on chemical treatment, I would suggest you look into high capacity filtration for your drinking water nees and add your chemical treatment. you are in an area where really clean spring water is availible, a decent cloth/sand filter would make most of it near drinking quality and if you boiled it to get rid of bio concerns and then filtered it only for drinking, you could probably spend a few hundred bucks and have drinking water for 2 or 3 years.

[HDR]

In the proper sense of the process you're correct; however judging by the search engines they are called Solar Stills and the process is called distilling.

http://en.wikipedia.org/wiki/Solar_still

http://www.solaqua.com/solstilbas.html

http://www.desertusa.com/mag98/dec/stories/water.html

http://www.watercone.com/product.html

This Invention represents a conical, self-supporting and stackable Unit made from transparent, thermo-formable polycarbonate (same as water dispensers) outfitted with a screw cap spout at the tip and an inward circular collecting trough at the base. Technically speaking it is a solar still.

Nope, everyone knows a still makes shine.. lol

Solar Still
Manufactured to ISO 9002
NATO Stock no. 4610-66-144-2646

Energy Free! Aquamate Inflatable Solar Stills are light, compact, float and very easy to use. They utilize solar radiation to distill and collect pure drinking water from sea or impure water. The still will produce 500 to 2000 ccs (1 to 4 pints) of water per day and has been used by military and civilian services throughout the world for the past 40 years. Packs neatly away to 26 x 23 x 7cm. At a fraction of the cost of a mechanical or electrical unit this is an ideal addition to the grab bag for any ocean going yachtsman.
http://www.landfallnavigation.com/memss.html

[NAPOTS]

Is my original idea of using parabolic reflectors to concentrate the energy on tubes of water with the intent of boiling them and collecting the vapor a better idea?

You mentioned the concern of chemical contamincation, I think much like an alcohol still where you throw out the heads and tails of the distillation you could do the same here and get rid of chemical contaminants.

[El Jefe]

You sound as though you have done a bit of research on chemical treatment, I would suggest you look into high capacity filtration for your drinking water nees and add your chemical treatment. you are in an area where really clean spring water is availible, a decent cloth/sand filter would make most of it near drinking quality and if you boiled it to get rid of bio concerns and then filtered it only for drinking, you could probably spend a few hundred bucks and have drinking water for 2 or 3 years.

Yeah, I've done some and need to do more. I'm currently looking for land here in central Mizzou, I want around 30 acres to hunt on and build a cabin. I'd love to have a spring on the property, plus I want river frontage.

Recently I've been pricing getting a well drilled, looks like that will cost six to ten thousand for a deep usable set up. I've also looked into a rainwater cistern, that would be cheaper but has obvious drawbacks.

What I need to nail down in the short term is filtration and chemical treatment.

[Bick_Sastard]

In the proper sense of the process you're correct;

Nope, everyone knows a still makes shine.. lol

I did not need a wiki refrence or some company trying to hawk their wares to know I was correct.

Grandpa's made shine, the last one I was involved with was for separating nitroglycerin and nitrocellulose mixtures, now that was a fun project!

Calling those units “distillation systems” and referring to the “evaporation and condensation” process as distillation are quite the stretch and because they are based upon the Carnot cycle one could say they are similar, but that is where the similarities end.

There are miles between an atmospheric evaporation unit and a low pressure boiler distillation unit, miles.

[Bick_Sastard]

Is my original idea of using parabolic reflectors to concentrate the energy on tubes of water with the intent of boiling them and collecting the vapor a better idea?

You mentioned the concern of chemical contamincation, I think much like an alcohol still where you throw out the heads and tails of the distillation you could do the same here and get rid of chemical contaminants.

Yes and no sir, I will try to explain and if it seems I have simplified it to sound insulting, please understand I have no idea of your base knowledge.

The words hot and cold really have no meaning at all, they are relative terms, most folks would say ice is cold, but not compared with liquid nitrogen’s boiling point. A lot of folks would say 100 degrees is hot, but not compared to a car motor, a torch, a welding arc or the surface of the sun.

So you have to realize the process is an energy transfer or conversion. The fire on the tip of a match is "hotter" than the burner of some electric stoves, but it will not boil a pot of water as it does not contain enough thermal energy. I say this because temperature has little to do with heat "quantity" and is best stated as "heat intensity", this really applies to your idea.

Take a magnifying glass, draw the dot down to a pin point with the light coming through and you can cause paper to light on fire. You have concentrated all of the energy the glass could take in into one very tiny area. You have not increased the amount of energy though, you just concentrated it in a tiny spot.

Water is an energy hog. A popular size air conditioner is 2.5 tons, that would service a reasonably insulated home of one story and about 1400 sq ft and down, that is the same amount of energy it takes to boil about 3.75 gallons of water. Its called latent heat and water has a lot of it.

The parabolic allows you to concentrate the energy it can capture, but that does not increase how MUCH energy it captured. I would have to put pencil to paper to determine what kind of size a parabolic would have to be to boil off a gallon, but I am thinking it is going to be pretty darn big do get anywhere near two gallons a day. It would also be weather dependent and unreliable.

As far as the original thoughts on it being a prime mover for steam powered electrical energy generation, no sir, I know that any reflector that could approach running even the smallest gentset would be huge and cost prohibitive.

As far as the "toss out the first and last" that is not what I am talking about, that is disposing of the low and high boiling point fluids that come out "before and after" the alcohol. It is based upon temperature, its good science, but not the same science. I am speaking about how chemical bonding to water can occur with certain substances and distillation will not fully separate the water from the other chemical. All across the temperature of the operation a certain percentage of both the water and the chemical would always be present.

There are serious issues with marketing and accuracy when it comes to whether or not it even applies. For example, one of the links HDR posted, the firm referred to "salts" and Ph, they do so because the average person has no idea how or why they actually apply. They also threw in some unsolvable math to attempt to gain credibility. Water contains TDS aka totally dissolved solids, when water evaporates it leaves those behind as they do not vaporize, you have seen this, lime scale on faucets or water spots on your car if you did not dry it off. Not all of those solids are good and not all of them are bad. Calcium is good for you, lead is bad for you.

No quality distillation unit manufacture will make any claim of purity unless they know what it is you seek to distill and in fact, a really good company will not guarantee it without first testing your material to be distilled. Now that said, water is a huge variable. The contaminants in a river might well change significantly within a few hundred yards. Distilling "tap" water is fairly predictable because there are standards that tap water must meet and tap water is not "open" to the atmosphere to get contaminated from stuff in the air. Pond water, river water, rain water all are and they require serious consideration when your going to drink it.

Grandpa threw out the beginning and end to make it taste better and be more potent, grandpa also knew what went into the still, but even then some folks grandpas did a bad job and some poison white lightning got distributed every now and then too.