Introduction: Build a Simple Solar Still

Picture of Build a Simple Solar Still

I've posted here about the square foot solar cooker, and here is another of the many uses for it.
This is a solar alembic, or pot still, made from square foot mirrors, which can produce between 2 and 5 ounces of distillate on a lazy sunny afternoon.

Step 1:

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It is not that great at making distilled water (without added reflectors as above), but can make essences, perfumes, and even ethanol.

Please note: it is illegal to distill ethanol except for fuel, and you must have a federal permit to do so.  However they are not that hard to get, and our government is actually encouraging the citizenry to experiment with this which is why I'm writing.  I am with a group who have one.

Here is the link for a permit, which you MUST have.  You need to specify that you will be making alcohol for fuel on the permit application.

Step 2:

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The Reflector

You need 3 square foot mirrors, about $7 at your hardware store to build the reflectors..

Step 3:

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Put them together with duct tape (carefully) to make a half box.

Step 4:

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You can run a bead of silicon along the seams.

Step 5:

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Be sure to have some backing on the mirrors (as above) as they are dangerous to carry about. You can use cardboard, or even better a good wood backing for safety.  Paint your wood with a good coat of shellac or paint to help preserve it in the weather.

Step 6:

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Your 'mash' bottle, outer cover insulating jar, and collector bottle can be had with a little scrounging in the recyclable bin, or from your local bar or casino.  For the outer insulator jar, I use both glass and PET plastic gallon jars.  I like the PET better because it insulates just a bit more, and is lightweight and unbreakable.
Cut a 1 inch hole in the middle of your jar lid to allow the beer bottle to poke through.

Step 7:

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The inner mash jar is just an old brown colored quart beer bottle, and the collector bottle can be any 12 oz glass bottle.  You need a couple of corks with holes (from your local wine-brewer's hobby shop), and a 16 inch length of 3/8 copper tubing bent into an inverted "U".

The unit goes together as shown.  Since you're not going to be drinking this, but are rather making fuel, you don't need to condition you copper tubing.

Step 8:

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When you fill your inner jar with mash, be sure to leave enough space for expansion, or it will 'puke' on you and splurt a lot of mash into your collector jar.  I fill my 32 oz bottle with about 28 oz of mash.

If you are distilling for ethanol, you are required to put a 'spoiler' into your collector jar.  A bit of gasoline will make it unpalatable, however I have tried using rubbing alcohol, since I know what the proof (% of alcohol) is on that as per the label, whereas I'm unsure of gas. 
So far testing proofs has been iffy, but I have learned to easily tell if the distillate is over 50%.  Vodka, at a rating of 40% WILL burn.  However, it takes a very good lighter, and some patience.  It will burn though as I can attest.

Here is how i check to see if it's above 50%, which lights so much easier than vodka.  It is a beer can upside down (I use fosters, since it will easily hold 10CC of fuel).  Measure 10CC into the cup and light it.  If it lights easily, you've got over 50%.  After it burns out, measure the remaining water, and by some math you can figure out your %, or Proof as they say. (Proof is 2X the %)
If I have 4CC left over, then my distillate was 60%.
Try burning 10CC of 91% rubbing alcohol, and you can get a feel for proofs.
Of course the best way to test is to use an alcometer.

Step 9:

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Since alcohol evaporates starting around 170 degrees (less here in the high desert) by the time your mash bottle hits boiling, most if not all of the ethanol will have been removed into your collecting jar.  Of course, the less ethanol in the mash, the higher the boiling point becomes, the unit works, and drives out the alcohol, it boils less easily.  The cool thing here, is that the 3 square foot mirrors do NOT QUITE have enough energy to distill water.  Therefor, when the alcohol is gone, it quits working.  How marvelously convenient.
This is a set-it and forget-it device.  Point it at just slightly South of where the sun sets, and it'll do all the work by itself.  When it's distilled most everything, refill the mash jar, but pour the leftover mash onto your compost heap. Or you could perhaps water your plants with it, it is certainly sterile by this time.

Step 10:

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And, it's pretty much weatherproof.

This post is not intended to nor does it wish to promote the illegal distilling of 'moonshine', but rather as a potential way for interested folks to learn how to make ethanol for fuel, or other non-alcohol products, including distilled water and essences as we progress toward sustainability and self sufficiency.
While some people dislike the idea of making ethanol from our corn and grains, the leftover mash is rumored to be a superior livestock food.  And, why not glean some ethanol fuel out of it along the way if we insist on feeding grains to our cows? I believe the development of simple solar distilling can greatly improve the EROEI of ethanol, and perhaps reduce the cost by 60% or more.
Additionally with solar, there is no danger of flame ever catching the vapors on fire.  It is flameless, if you don't count that great big ball of fire in the sky.


zBackman (author)2014-11-04

aluminum foil inside the boxes used for fish 2" walls

Inside a cardboard box, but need a second box to make the triangles to fill in where the flaps of cardboard box are not.

Sheet of glass or plastic. Cooks rice in 25 minutes (glass mason jar painted black outside.) Cooke bread, made tea I forget what else was my daughter's 2nd grade science project.

Boxes we got for free at the local fish market. Aluminum foil was enough for about ten of these (wide roll heavy duty 25m) use contact cement, but made a second one just forming the foil and folding it over edges.

Pice of glass was the largest expense. I think it cost about 50 cents (no rappers were harmed).

First one was $2 second one we used the rest of the foil and another piece of glass so 57 cents (figuring the cost of the foil)

TxMike (author)zBackman2015-10-03

That sounds interesting for our coast camp. Any pics or links would be appreciated. Everything we keep there is cheap or disposable due to tropical storm damage and thieves.

cobergland (author)zBackman2014-11-04

zBackman, very nice. Cardboard works well, and if you find you like cooking with the sun, you can either make another one for next season, or make on out of more durable materials. I do like my glass and wood cookers because I can leave them out overwinter with little or no harm. Good Job!!

zBackman (author)cobergland2014-11-04

I work with people who think a piece of wood is used to build a house. Not a lot of snow in the tropics, well outside of Peru, but different kind of snow.

I like to use materials that can be found for free of very cheaply. Wood, mirrors, $7 I can buy lunch for 20 people.

katabillups (author)2015-09-06

Thank YOU!!!

bpersun (author)2013-03-08

At step 6, you show a condenser that looks like it has a screw top lid.
Where did you get this? Is it glass or plastic?
Thanx, Lovely job!

kereu (author)bpersun2015-07-20

hi there.

cobergland (author)bpersun2013-03-08

Hi bpersun, the condenser is just a glass fruit juice bottle, and you can either put a #3 cork with a hole in it, or carefully drill out a 3/8 hole in the screw top lid. If you do the latter, the plastic seal inside the lid will help to seal the tubing. The tubing fits in the hole fairly snugly. Seems to work ok, but I don't know how many vapors can escape. I want to try sealing that hole area with a flour water mixture like the 'real' distillers do. Thanks for comment!

mperrault1 (author)2015-02-26

Using plastic in a still is just bad news. Use a large cork instead of the plastic lid and you'll save yourself from drinking the plastics

cobergland (author)mperrault12015-02-26

Thanks mperrault1, but if you look carefully you will see that the plastic lid from the larger jar has NO way of contaminating the mix. The large plastic jar, and its lid are only for insulative qualities. And, since the mash gets hot, it does not draw any plastic or other air into the feed bottle, nor does any plastic get into the collector bottle. Again, the working part of the still is 1. glass bottle, 2. cork and copper tubing, 3. glass collector bottle and cork. I was using rubber corks, however have switched to cork corks. Thanks for your input.

Gadget93 (author)2013-03-07

Perhaps as a spoiler one could put in 10% C2H5OH. That is some terrible stuff and I'm sure nobody would want to drink that.

cobergland (author)Gadget932013-03-07

Sorry, but don't know what that is...?

Kaljakaaleppi (author)cobergland2013-06-05

I'll give a hint. An alcohol with tho carbon atoms.

Gadget93 (author)cobergland2013-03-08

Sorry, I was using nerd humor. That is the chemical structure of Ethanol. I was also using a bit of sarcasm as a joke.

Samw (author)2013-03-17

What if you created a wide angle back and a one way mirror front? Or would too much light energy be lost through the double pane of the one-way mirror?

cobergland (author)Samw2013-03-18

@ Samw, I'm not sure what a one-way mirror would do....
If you widen the angle of the mirrors, you may get a little more energy collected, but for my purposes the 90 degree configuration works perfectly.
I measured some soybeans once cooked under pressure in the cooker, and it reached around 240 degrees+. It was scary hot when I cracked the lid open, and hissing steam whooshed out everywhere.
So it has a good temperature range.
The way to increase the temps is to gain in reflecting area, which means add more mirrors, and keep it focused all the time, or super-insulate the inner cooking container.
However, the downside of this is that you will have to track the sun more often I suspect.
I really like the 90 degrees, because it takes minimal attention and tracking.
Since I'm a lazy old fart, I enjoy the 'set it and forget it' feature, and it can boil most things in under 2 and 1/2 hours if left alone, and can raise a quart of liquid about one degree per minute.
If you build one, do some tweaking and write back what you find out. Thanks.

tstrain (author)2013-03-09

From a naive do you "condition" a copper pipe AND what is "mash?" Loved your Instructable! Thanks!

cobergland (author)tstrain2013-03-09

@tstrain, If you read through the comments section, it should answer your questions. Thanks for kind words....

chaseis1badmonkey (author)2013-03-08

Fuel, sure ;)

roberto sirigu (author)2013-03-07

Muy buena idea tengo que probar me gusta mucho tu invento vivo en Sevilla España el sol nuca falta!

Roberto, thank you I think? Me espanol is pobre.

loafers (author)2013-03-08

Very nice mate. Very convenient for those of us who enjoy a good camp in the bush. I've always wanted to try out making and using an alcohol stove. Is home brewing really illegal over in America?

cobergland (author)loafers2013-03-08

Hi loafers, it's not illegal to brew here, it's just illegal to distill. Alcohol stoves are great, and ethanol does not smell bad like burning rubbing alcohol. Ewwww.

arty (author)2013-03-08

Cool. Thanks. Well done. Your beer bottle in a PET bottle might make an automatic stock-tank heater, too.

Have you considered the flip-side? Instead of making a passive solar heater, how would you make a passive cooler? Every time you see a "Bridges May Be Icy" sign, you are seeing a warning of an artificial cold spot. Dew and frost on your windshield are another proof of something going below ambient temperature. If you could domesticate that cold, it would solve a lot of the world's problems. Looking at the local temperature/dew point charts, I see the spread is often just a few degrees. If you could build a artificial cold spot that took advantage of that small spread... Rural dwellers use about 37 gallons a day. Urban dwellers use more like 150 gallons per day. (The cities defend this figure by blaming the difference on the fire department and industrial use.)

But we don't need huge quantities to make an important difference. One Peace Corp volunteer-teacher wrote that she walked x (3?) miles each day before class, for 2 gallons of water, which had to suffice for all her cooking, washing and gardening.

I asked the State of Colorado what would be the legal consequences if I could "strike a rock with a staff and get water." They said that it would be classified as "weather modification:" and "under no circumstances would the water be yours." If this seems harsh, remember that the States and Municipalities have an enormous investment in "water rights" and delivery infrastructure. The "water rights" to one acre-foot of water cost between $3600 and $7200... of course you get that acre-foot of water every year, forever... if it is there to be got... and if your water-rights are senior.

In 1922 a S.B. Russell patented an "air well" that delivered 75-gallons a day in the winter and 150-gallons a day in the summer, but his airwell was concrete, thirty-foot on a side and five feet deep. The world needs an airwell that can sit on your kitchen counter and deliver half-a-gallon a day.

Capturing or retaining heat is easy. Avoiding or rejecting heat gain is tougher... and yet for centuries the Arabs have made ice by exposing a bowl of water to the night sky, then insulating it during the day. The Crusaders built "siege ponds" to provide water for their hilltop fortresses. History says this can be done, has been done, that man has known how to do it wholesale for thousands of years.

The guy who can figure out how to do it retail is going to spawn a billion dollar industry.

Feel challenged.

cobergland (author)arty2013-03-08

Arty, Carl at has a system to capture water from pipes in the ground,condensing moist air you might enjoy reading that. He was trying to interest people in building this system for the folks in Haiti. Thank you for interesting comments.

mboese (author)2013-03-07

Sorry, another question, can stainless steel tubing be used instead of copper?

cobergland (author)mboese2013-03-07

From what I've read it can, and is probably superior. But too pricey for me...on a budget.

mboese (author)2013-03-07

I am interested in trying this, purely for scientific purposes, you know... ;) I am just curious about a few things. First, how do you "condition" the copper tubing, and second, what is in your mash? Thanks!

cobergland (author)mboese2013-03-07

Read 5 replies up for conditioning. You can use whatever mash you want, I've tried plain sugar wash, wines, and want to try wheat germ mash eventually, as well as the sunchokes if they will ferment..

chuckyd (author)2013-03-07

"Proof" is actually obtained by pouring alcohol over gunpowder and burning it.

JamesRPatrick (author)2013-03-07

The first five steps could be titled, "How to Make a Retroreflector."

cobergland (author)JamesRPatrick2013-03-07

Yes the 'Retroreflector' is the key to it all. 90 degrees works great, and it's not too big, not too small...just right. Thanks.

mlheran (author)2013-03-07

This is a great 'able, wow! Could it be used to distill water, and if so, what kind of conditioning is needed for the copper tubing?

cobergland (author)mlheran2013-03-07

@mlheran,, I haven't put much time into distilling water, but I think with the addition of a couple more mirrors (as above) it could do water. it would be interesting to find out how much water in a day it could do. However this setup will disinfect water, and if you look at my last instructable, it shows how. We need a minimal of a quart of 'safe' drinking water a day, and that's not if we do much physical work. AFA conditioning your copper, I've read that you should clean it well, and then run a mixture of white vinegar and water through it to make it potable. I have soaked the ends of my copper pipe in half and half (water and vinegar) and it cleans it amazingly well. There are some sites on distilling that can give you more info on that. Thanks for comment.

static (author)2013-03-07

I used 2 L. clear soda bottles as small hot water heaters. I found putting a length of black poly pipe or 2 inside the bottle helped heat it up faster. I think the biggest reason why they want to permit us to produce ethanol is to make sure we pay our road tax. Not that I mind road taxes, they are they only tax dollars I see working for me. :)

cobergland (author)2013-03-07

@ gn0stik, thanks for the info, it is always best to use the correct terminology, and for the link.
Until we all lobby our government to allow for the home use of nano-stills, I am going to concentrate on ethanol for fuel.
I am growing a batch of Jerusalem artichokes (sunchokes) to try, and in David Blume's most excellent book "Alcohol Can Be A Gas", he says that the chokes are a good feedstock. I highly recommend his book, as it is IMHO the bible of distilling, and it shows the possibility of a new world based on renewables. A great read, and I hope to finish it one day (it's looong and comprehensive), as it is a wonderful permaculture book.
My only objection is that he says solar distilling is basically not worth it, which as we suspect is wrong. I have attempted to reach him via his website, but have had no response. It is a wonderful book, and a 'should read'.
I am encouraged that folks are reading about this still, and grateful to Instructables for being a good place to post. I will continue to put up my goofy stuff from time to time, and hope that you will share your experiences if you build one of these. Thank you.

GreenMeUpScotty (author)2013-03-07

Thanks for the tips! Good Stuff!

gn0stik (author)2013-03-07

Isn't there an online version of the application?

gn0stik (author)gn0stik2013-03-07

Found it...

You will need to create an account in order to submit the permit request.

gn0stik (author)2013-03-07

Ethanol distillates are called the "Wash" not the "Mash." Not that it matters much, but mash is the term used for beer, and is always comprised of grains. A wash can be pure cane sugar that has been fermented with champagne yeast, or even baker's yeast for that matter. Second, for any who would drink this, a word of caution: go read up on how to separate the "heads" from the "hearts" (drinkable) of your finished product. The first drops will smell like turpentine, and will burn in your nose, so start with a different container than the one you intend to keep the "hearts" in. Once it starts smelling like 151, or something similar that is drinkable. The methanol "head" can kill you, or blind you, not just rot your gut. It's hard on all your organs.. kidneys, liver, stomach, brain, etc. etc. But it makes a good cleaner. The last drops are called the "hinds" or "tails." and is less desireable due to impurities, and can be saved to add to the next batch of distillate to be redistilled. It's best to change containers when it begins to slow down, but has not yet stopped. This way, your "hearts" remain pure. All of that being said, if you are just making fuel... it is pretty much just set it and forget. And I have to say I do like the simplicity of this design.

bedwere (author)2013-03-07

Corn is used to feed cows because it is artificially cheap. In fact, federal agricultural subsidies (i.e. your tax money) are paid to corn producers.

cobaltxxxfusion (author)2013-03-07

Just a word of warning to those of you want to sample the very first thing that is going to distill off is going to be a small amount of methanol. I am not sure of the percentage produced in a typical batch but I believe it is around 3 to 4% of your total volume. It is not enough to kill you unless you got it pure but that is what makes "rockgut" whiskey. It is worth the time researching just in case you decide your body needs a little fuel. Great Instructable. Thanks for posting.

streetrod5 (author)2013-03-04

I wouldn't force-feed my cow to eat corn, so instead I will suffer in its place; I will *dramatic sigh* drink the corn ethanol (I mean "fuel my tractor!" yes, that is what I mean).

This is an elegant, simple design, and your 'Able is well-made. I will have to try this. (When my permit is approved, of course) Cheers!

cobergland (author)streetrod52013-03-05

Thank you streetrod5, for your comment.
As I understand it, it is not good for cows to eat corn, anyway, but then I'm not a farmer or rancher, so don't know. I would not be surprised if the leftover distillers mash is good as a supplemental feed, however. And it's probably good for chickens, etc., too. Maybe even humans.

Just a sidenote -- the 90 degree angle of these mirrors seems just about optimal. You shouldn't need to mess with it.
If you narrow the angle, you will get a hotter temperature quicker, but you will have to track the sun more often.
Conversely, if you widen the angle, you won't have to track as much, but your temps will likely be lower.
If you use this reflector to cook your foods (in blackened quart bottles) you should be able to cook most anything if you point the left edge of the reflector (as viewed from behind) right at the sun. As the sun moves (an illusion, we move...), it will get your stuff slowly and gently hotter and hotter, as it increasingly keeps adding heat. And, after the sun starts to wane, it will keep cooking after it reaches max. The insulating outer jar I think is what keeps it going.

Used as a still, the cooker is not a plug and play device -- you have to let it warm up. It takes a couple of hours in the sun before you notice anything. And then, you'll see a drop fall from the copper tubing into the collector jar. Then a bit later, another drop. When it gets up to good heat, I've recorded a drop about every 3 seconds. And it will keep at it until the alcohol level drops,and then it will gradually slow down. That's kind of how you can tell when it's all been captured.
Again, thanks for your kind words.

greenplat0 (author)2016-10-07

Wow this is a fun project, thanks! Perfume oil is my aim and your sun still seems like a legit way to fire and forget!

cobergland (author)greenplat02016-10-07

thx ive made hydrosols of sage, mint, jasmine, and rosemary so far and they are pretty good no need to use fossil fuels and other silliness keep me posted please on your progress XOXOXO

RossP18 (author)2016-02-21

I love! been looking for this. thanks this will work after emp comes.

cobergland (author)RossP182016-10-07

yes it will, off grid using only eonderful solar!!!

cobergland (author)RossP182016-02-24

Yes, Ross, either emp or collapse/peak resources stuff. I try to make all my projects to be used offgrid and after collapse or during Loooooong emergencies. Appreciate your input. thx.

WaqarAli1 (author)2016-04-26

Hey cobergland, if I want to distill water, can I just use vinyl tubing instead of copper

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