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:

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:

The Reflector

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

Step 3:

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

Step 4:

You can run a bead of silicon along the seams.

Step 5:

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:

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:

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:

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:

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:

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.



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    52 Discussions


    4 years ago on Introduction

    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)

    3 replies

    Reply 3 years ago

    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.


    Reply 4 years ago on Introduction

    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!!


    Reply 4 years ago on Introduction

    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.


    5 years ago on Introduction

    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!

    2 replies

    Reply 5 years ago on Introduction

    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!


    3 years ago

    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

    1 reply

    Reply 3 years ago on Introduction

    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.


    5 years ago on Step 8

    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.

    3 replies

    Reply 5 years ago on Introduction

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


    5 years ago on Introduction

    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?

    1 reply

    Reply 5 years ago on Introduction

    @ 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.


    5 years ago on Step 10

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

    1 reply

    Reply 5 years ago on Step 10

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

    roberto sirigu

    5 years ago on Step 10

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