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contactDIY solar water distiller
Page created June 16, 2019
This page has DIY plans for a solar water distiller. This will evaporate brackish or salty water and output pure distilled water. It is powered entirely from the sun, and is very simple to construct, using materials that are expected to be safe for drinking, and long-lasting.
Actually, this is prototype #2, as #1 was learning how to do it, and
making improvements that went into #2. I reported the progress in my
blog. It was a learning curve, discovering what sealants bonded with
what materials, temperature limits, potable-water safe materials,
construction methods, and so on. For example, I posted about bonding of
Selleys 401 silicone sealant here:
http://bkhome.org/news/201905/testing-bonding-of-selleys-401-silicone-sealant.html
Here is a blog post testing wicking cloth:
http://bkhome.org/news/201905/testing-wicking-properties-of-felt.html
If you would like to get an overview of what solar water distillers
are all about, and the different designs, this blog post has links:
http://bkhome.org/news/201905/solar-water-distiller-online-references.html
In a nutshell, the tilted wicking-cloth type of distiller gives
higher water output than the basin type. Some efficiency figures are
typically 50% for the former, 30% for the latter.
Before we get started, there are health risks with sawing the
MDF/wood and spreading the sealant. It is advisable not to inhale the
MDF/wood particles, nor the vapours from the sealant. It is also
recommended not to touch the sealant with bare skin. Therefore, buy some
basic protection, if you don't already have these:
| Goggles, ear muffs, face mask set |
$14.90 |
https://www.bunnings.com.au/safety-zone-7-piece-safety-kit_p5820600 |
| Disposable latex gloves |
$7.40 |
https://www.bunnings.com.au/handy-white-disposable-latex-gloves-50-pack_p1662552 |
These plans assume only a very basic set of workshop tools. You will
be required to have two G-clamps, and electric drill. If you cut the
side pieces, instead of ready-made dressed wood, you will need some
means of cutting sheet timber, such as a rotary saw. There are some
items that I have explicitly listed in the parts tables below.
Now onto the DIY plans...
1: Build wooden frame
The base of prototype #1 was made with a premium-plywood base and
pine sides. However, the sealant that I had chosen, Selleys 401
silicone, did not stick well to either. On the other-hand, it did stick
very well to MDF (Medium Density Fibreboard), so decided to go with MDF
for #2.
I chose cheap "Standard MDF" sold by Bunnings here in Australia
(manufactured by Alpine). This is intended for indoor use, however, if
built correctly, it won't get damp (I hope!), and should be OK outside.
Here is the shopping list, prices are in Australian Dollars (AU$1 is approx US$0.70):
| 600x900x16mm MDF |
$13.40 |
https://www.bunnings.com.au/16mm-standard-mdf-600mm-x-900mm_p0590044 |
| 450x900x16mm MDF |
$9.90 |
https://www.bunnings.com.au/16mm-standard-mdf-450mm-x-900mm_p0590052 |
| 6G 25mm wood screws |
$3.98 |
https://www.bunnings.com.au/zenith-6g-x-25mm-zinc-plated-hinge-long-thread-countersunk-head-timber-screws-35-pack_p2420440 |
| 6G 30mm wood screws |
$3.98 |
https://www.bunnings.com.au/zenith-6g-x-30mm-zinc-plated-hinge-long-threads-countersunk-head-timber-screws-35-pack_p2420068 |
The 600x900 MDF is the base-plate, so that will be the size of the
distiller. Around the edges, will be the sides, and I cut the 450x900
MDF into 50mm high strips for that purpose.
I discovered very quickly that there is a big downside to using MDF
for the sides -- it very easily de-laminates when screwing into the
side. It can be done, but extreme care must be taken. Pre-drill the
holes, and only use short screws. I would have preferred pine, but had
the bonding problem with the sealant.
As I only have very basic tools, to cut the MDF into strips required
some improvisation. I marked out every 50mm and used two G-clamps so
that my rotary saw will cut in a nice straight line:
I cut off four strips, and a fifth just in case one of them was a bit
off the required 50mm. But, they turned out reasonable close, within
0.5mm anyway.
Please wear goggles and face-mask when cutting, as the particles are a health hazard.
The two long sides need notches cut in them, for the inlet and outlet
pipes. Rather than having to drill round holes, which I did in #1, this
time it is simplified, just cut rectangular notches. I have one of
these, so add this to your shopping list if you don't have something
like it:
| Mitrebox and tenon saw set |
$14.98 |
https://www.bunnings.com.au/craftright-mitre-box-and-saw-set_p5710099 |
Also, if you don't have these size drill bits:
| Drill bit, 2.5mm |
$2.95 |
https://www.bunnings.com.au/sutton-tools-2-5mm-hss-metric-viper-drill-bit_p6351582 |
| Drill bit, 3.5mm |
$3.60 |
https://www.bunnings.com.au/sutton-tools-3-5mm-hss-metric-viper-drill-bit_p6351639 |
Here is a sketch showing the notches and dimensions:
My 3-dimensional sketching is a bit wonky, but it should be easy to
understand. The two notches at the top are for the inlet pipe, that runs
right across the top. At the bottom (right side of sketch), the left
notch is for the waste-water outlet, and the right notch is for
distilled-water outlet. Short aluminium pipes will be slotted into the
two bottom notches. All pipe is 12mm outside-diameter.
Note, I built prototype #2 with a 12mm thick base-plate, but you can
see in the above sketch, it is increased to 16mm. For structural
soundness, I decided that 12mm is a bit too thin. Also, there is heat
loss out of the back-side of the still, and a bit more insulation will
help.
Note also, in the above sketch, I have tweaked the dimensions of the
notches. The inlet notches were 15mm high, have increased that to 16mm.
There is a gap of 10mm between the pipe and inside of top-side-piece --
just enough the fit the cloth with rod inserted (see photo further down)
-- hence the 26mm shown -- but of course, if you were to use thicker
side-pieces, then this would have to be increased.
Using a bath towel, that 10mm gap was a very snug fit, so that 26mm could be increased to 27mm.
And, the distilled-water outlet notch was 12x12mm, now 12x15mm, so that the water runoff slope can be increased a little bit.
Cutting the notches is pretty easy, using the mitrebox and tenon saw.
Make multiple close cuts within the notch, then use a chisel, or in my
case a screwdriver, to remove the debris from the notch. File it if
necessary.
The four side pieces can now be joined together. To avoid splitting
the MDF, the holes must be pre-drilled. I used a 2.5mm drill bit, and a
3.5mm drill bit for the "first" piece of wood. Then a larger drill bit
to gouge a countersink, done by hand.
I have used 6G 25mm countersunk wood screws. Do not try to "do them
up" too tight, as it will split the MDF. If you do find the wood
starting to de-laminate, do not despair, as it will all be glued
together.
At this stage, grab a felt-tip pen and write "L", "R", "T" and "B"
(left, right, top and bottom) on each of the side pieces, and "T" and
"B" on the base-plate. This is important, to avoid a dumb mistake after
having unscrewed everything and then putting it back together later.
After having screwed the four sides together, turn everything upside
down, and drill holes to attach the base-plate to the side pieces.
Again, pre-drill with 2.5mm and 3.5mm drill bits. This will later be taking 6G 30mm
screws.
Now, give the sides and base-plate two coats of exterior
acrylic paint. If you have any in the shed, great, white or any light
colour is OK. Only paint the bottom of the base-plate (which will be the bottom of the
still when it is right-way-up) and the sides -- do not paint anywhere that will be on the inside,
nor in the notches.
That is, it is only the exterior parts of the wood that are painted.
If you have the four side pieces screwed together, partially unscrew
them so that painting does not cause them to stick together. Here is my
effort:
 |
|
...my painting was a bit sloppy, but try to only paint the outside of the side pieces. Keep paint out of the notches also.
The reason for painting it now, is we are going to unscrew all the MDF pieces, then re-screw them, with silicone sealant as an adhesive. Any sealant that gets onto the outside cannot be painted over, hence we get the painting out of the way beforehand. Note, Selleys 401 silicone is translucent, and will be very slightly milky when cured.
2: Glue wood frame and base
As mentioned above, I put silicone sealant into the wood frame, as an
adhesive, as the screws are so weak in the MDF. This is a step that you
could bypass if using premium/marine plywood and pine (see
"Improvements" at bottom of this page), as that would be much stronger.
Firstly, choice of silicone. I chose Selleys 401 silicone sealant, as
it is specified for use in potable water and exposure to steam. Not all
sealants meet both of these requirements. It also must bond well
with whatever is used for the base-plate and side pieces.
Here is a table of bonding tests that I have conducted. The Parfix
"Roof, Gutter and Concrete" silicone sealant is just what I had lying
around in my shed, it does not meet the potable-water requirement. If
anyone wants to test their silicone, we can expand this table:
| Product | Plywood (pine) | Dressed pine | Standard MDF** | Cured sealant* | Glass | Aluminium | Acrylic paint |
| Selleys 401 silicone sealant, acetic curing | 
|
|
|
|
|
|
|
| Parfix Roof, Gutter and Concrete silicone sealant, neutral curing |
|
|
|
|
|
|
|
* Cured sealant is the same type as that being applied on top.
** Made from pine, no waterproofing treatment.
For a tick, the applied sealant cannot be pealed off. If it can be
pealed off, even with difficulty, it fails. If it tears when try to pull
off, but with persistence (using fingernail) can get it all off, give a
tick with a small cross.
Anyway, for the current DIY project, I have chosen Selleys 401
(clear). Purchased from Bunnings. Also buy a spreader tool. And, if you
don't have one, an applicator gun:
| Selleys 401 silicone sealant, two 310g tubes |
$19.65 x2 |
https://www.bunnings.com.au/selleys-310g-401-rtv-engineering-grade-silicone_p1231042 |
| Sealant applicator gun |
$4.35 |
https://www.bunnings.com.au/uni-pro-skeleton-caulking-gun_p1670517 |
Start with the four side pieces, screw together with 6G 25mm screws,
do not tighten. Now, unscrew one corner, apply silicone into the gap,
and insert and tighten the screws. Remembering that MDF will split at
the drop of a hat when screwing sideways into it, so only tighten
slightly.
Repeat for all for corners.
Now run a bead of silicone all along the the side pieces (what will
become the bottom when it is right-way-up), and place the base-plate on
top, and screw with 6G 30mm screws. Again, exercise extreme caution when
tightening.
Wipe all around, to remove sealant that has squeezed out.
This step, of applying the sealant all around the the side pieces,
and placing the base-plate on top, has to be done fast, as you only have
a few minutes before it starts to skin.
I looked carefully, to make sure that there were no stray deposits
left anywhere, nor inside the notches. I also used disposable latex
gloves, but I have seen on many YouTube videos, people just using their
bare fingers to wipe over the squeezed-out sealant.
Now wait for it to cure. Which could take a week or more, to cure
right inside, but at least wait a couple of days, then it will be cured
enough to go onto the next step.
Note, putting the pieces together correctly, this is where those "L",
"R", etc., that you wrote on earlier, might come in handy, just in case
you have a moment of confusion.
Two days later, a critical operation is to be performed...
The inside of the still must be totally waterproof. So, the inside of
the base-plate and side-pieces needs to be coated with sealant. The
challenge will be to spread the sealant thinly and evenly over the
base-plate, covering the MDF completely. This is where the spreader-tool
is required.
However, while waiting, something else can be done...
3: Cut the pipes
The inlet and outlet pipes are aluminium, 12mm outside-diameter tube,
wall thickness 1mm. This is available from Bunnings. You will also need
a hacksaw to cut it, file, fine sandpaper, 1mm drill bit and a
hand-drill (or drill press):
| Aluminium tube, 12mm OD, 1m long |
$3.37 |
https://www.bunnings.com.au/metal-mate-rcr-12-x-1mm-1m-aluminium-round-tube_p1067750 |
| Hacksaw* |
$4.98 |
https://www.bunnings.com.au/craftright-300mm-tubular-hacksaw_p5710239 |
| Files, flat and round* |
$16.20 |
https://www.bunnings.com.au/craftright-9-piece-file-set_p5760101 |
| Fine sandpaper |
$1.70 |
https://www.bunnings.com.au/rocket-fine-sanding-sponge_p1661077 |
| 1mm drill bit |
$3.20 |
https://www.bunnings.com.au/sutton-tools-1mm-hss-metric-viper-drill-bit_p6351508 |
* You will likely have most or all of these tool-shed items. Drilling
a 1mm hole is a delicate operation, and you may prefer to use a drill
press, such as this: https://www.bunnings.com.au/dremel-220-01-workstation_p6200017
Here is another wonky 3-dimensional sketch:
The water inlet tube runs right across the distiller, sticking out
20mm at both ends. There are two short lengths, for waste-water and
distilled-water outlets, 46mm long, that will stick out 20mm.
Notice the spacing of the three 1mm holes. They are spaced so that
each allows for water to spread out by 94mm each side of the hole.
Use the mitrebox and hacksaw to cut the three pieces...
Note, however, one of the short pieces will be improved if cut at an
angle. This is the outlet for distilled water and the cutout will
improve channelling of runoff from the glass above. So, the short pipes
will look like this:
...notice the score marks. I did those with the hacksaw. The region
of pipe between the two black felt pen marks, is within the 16mm side
walls, which will have epoxy resin around the pipe. The score marks will
firmly lock the pipes in place.
Use a flat-file and rounded-file to smooth off any burrs inside
and out. It would be good to have a slight chamfer on the ends,
especially the inlet pipe, as it is going to be designed to slide out of
the distiller, if you ever need to make changes to the holes, or to
clean it.
Use the fine sandpaper to make the ends very smooth.
Drilling the three 1mm diameter holes in the inlet pipe has to be
done with care, to avoid breaking the thin drill bit. I wedged the pipe
in the mitrebox with a thumb, then realised that a length of 10x10mm
aluminium channel locked it more firmly. However, just the thumb and
mitrebox should be enough. Photo:
One thing that I found helped with the drilling, was to spray the
drill bit with Selleys RP7 lubricant -- there are many similar spray-on
lubricants, such as those commonly used to free stuck bolts, or
automotive electrical protection. Or, use oil.
It is important that the holes be drilled in a straight line along the pipe, as well as correctly spaced.
Then I was faced with the problem of removing some tiny burrs inside
the pipe. The fix was to feed rope through the pipe, and when holding it
tight, move the pipe up and down:
...looks like that worked! Then a final twirl of the 1mm drill bit in
each hole, by hand, to make sure that the holes are clear. I also blew
water through it, using a garden hose, to get rid of any lingering bits
of
aluminium.
4: Spread sealant on inside
A couple of days after having glued the wood together, now comes a
very exciting step, and a bit tricky, as it has to be done fast, before
the sealant starts to skin. For this step, you will need a spreader. I
chose this one, as it has a rounded edge, not sharp:
| 200mm sealant spreader |
$2.48 |
https://www.bunnings.com.au/uni-pro-wallpaper-smoother-and-straight-edge_p1661659 |
| 50mm+ flexible blades |
$1.48, or $6.55 |
https://www.bunnings.com.au/uni-pro-50mm-flexible-steel-filling-blade_p1660994 or: https://www.bunnings.com.au/uni-pro-4-piece-filling-blade-set_p1670761 |
...I added the 50mm flexible blade to the shopping-list, as it will
be handy when spreading the silicone on the sides. It is also useful as a
scraper. Or, you might prefer a wider one, so the set is probably a better choice.
I did consider putting a sheet of glass inside, then would only have
to apply sealant around the edges. Yes, probably doable, and may have an
advantage of improved insulation under the cloth, but decided to go
with spreading sealant over the entire MDF base plate.
Having made that decision, I approached this step with some
trepidation, as the sealant has to be spread thinly, very evenly,
covering the MDF completely, and has to be done within a few minutes,
before the sealant starts to skin.
I have figured out a technique, but the problem is, cannot pause to
take a photo. So, will have to describe it as best as I can...
I bought a second 310gm tube of Selleys 401 sealant. The one that I
had already used was about half empty, and I did not know how much would
be needed for the base. I cut the nozzle of the new tube well-down so
as to get a good flow:
...notice the torch. I used that after spreading, to carefully examine the surface for any bare spots.
I think that the instructions state, do not inhale the vapours, wear a
mask. I forgot about that. Also used my bare fingers for touch-up.
Standing at the bottom-end of the still, I ejected the sealant onto
the base surface, very generously, sweeping across, making sure that
there is lots right at the start, zigzagging backwards and forwards,
about a 12mm (half-inch) gap between each row of beads. Working as fast
as possible.
Much to my alarm, the tube was empty when I was only 2/3 of the way
through. Quickly loaded the other sealant tube, and continued. Again,
working fast.
Then used the spreader, starting top-left, did one sweep right down,
holding the spreader pressed fairly firmly to the surface. Then again
from the top, until had got to the right side.
A quick touchup with the spreader, as lines are left from the ends of
the spreader. The end result looks OK, except where I went back after a
few minutes to try and do a bit of extra smoothing at one place, and
only made it worse:
...the right-side is the top of the still. You can see that it looks
smooth, but on the bottom-left of the photo is where I went back after a
few minutes and tried to do a bit of extra smoothing.
I did a bit of touching-up with a 50mm thin springy metal blade, and used my finger.
I used the torch to look over the surface very carefully, and applied
dabs of sealant where there was bare MDF. Only a few found, around the
edges. The end result looks OK:
Then I made a discovery, please heed this:
This sealant bonds extremely well to itself. I found that using the 50mm flexible blade, patching holes several hours after having applied the sealant, worked well. Therefore, after doing the big sweep with the spreader, if there are a few holes here and there, just leave them. Instead of trying to fix them and making a mess as I did, wait several hours, even overnight.
The above photo shows the outlet pipes inserted. That can be done now.
The left-side, standing facing the bottom-end of the still (top-left of
photo) is waste-water outlet, the right-side is distilled-water outlet.
Put them in place, but only spread sealant on the inside, do not push
it right through the cutout notch. The reason is, I want to use 2-part
epoxy, to more firmly hold the pipes in place. Remember also, there are
score-marks on the tubes, that the epoxy will flow into. Here is a
closer photo of the waste-water outlet:
...you can see the "L" written on the side-piece. Notice also, the
slight de-lamination of the bottom-piece. This was when I first
discovered how delicate MDF is when screwing in from the side. I had
attempted with a longer screw (40mm) and tightened it too much. However,
the other side is OK:
...this pipe has the angled-cut, as distilled water will be flowing
from above, off the glass. Again, see that I avoided pushing the sealant
very far into the cutout notch. Notice the "R".
You do need to have a soft cloth handy, to wipe the spreader, and
spatula if used. A hint for the sealant tube: put thin plastic over the
end of the nozzle, held in place with an elastic band -- it prevents air
getting in, and will keep for years.
Wait a few hours at least, then do the sides and top. I found the 100mm flexible spreader useful for this.
The top pipe. for water inlet, must not be installed yet. First, the sealant has to cure. Wait until the next day...
5: Install inlet pipe
The inlet pipe runs right across, sticking out both ends.
Shopping list:
| Epoxy filler |
$2.10 |
https://www.bunnings.com.au/utility-25ml-slow-setting-epoxy-adhesive_p1662637 |
| Aluminium rod, 6.3mmx1m |
$2.32 |
https://www.bunnings.com.au/metal-mate-6-3mm-x-1m-aluminium-solid-rod_p1130541 |
| Cotton bath towel |
$6.00 |
https://www.kmart.com.au/product/malmo-cotton-bath-towel---black/2332350 |
...that 2-part 25ml epoxy is far cheaper than the others, but it is great, I have used it several times.
The bath towel and rod will be used later, however, it is convenient
to cut off a piece of the towel now, to use as a spacer for the inlet
pipe.
The towel that I chose is from Kmart. It is black cotton, without any
pattern or embossing. One end is really convenient, as the rod will be
inserted into it. Well, later, but just showing a photo now:
...how convenient that is! Otherwise, I would have had to sew a loop at the top-end of the cloth, in which to insert the rod.
Have shown this rod and towel photo now, as you will need to cut off a
strip of towel, to use as a spacer for the inlet pipe. Cut the strip
from the other end!
The towel spacer can now be placed, and the pipe inserted:
I originally had the idea of being able to slide the pipe out
afterward, by wiping margarine on the pipe before applying sealant and
epoxy, however, that proved too difficult. Therefore, as the pipe is
going to be locked in place, make sure that it is rotated so
the the nozzles are facing downstream.
The nozzles should be down, toward the cloth, but still viewable from
outside the distiller. You need to be able to see if water is coming
out of them.
Now, wipe silicone sealant on the inside, just as you did for the
outlet pipes. The sealant does not have to go all the way through the
notches, as I am going to apply epoxy into the outside of the notches,
to more firmly hold the pipe in place.
Must wait another day, for the sealant to cure, before pulling the
cloth through. But, there is one little operation that can be performed
now...
6: Epoxy distilled outlet
Just a little something to do, then have to wait until tomorrow to do Step 7.
Some electrical tape, mixed up a very small amount of epoxy, applied it:
Used a toothpick to try and encourage the epoxy to flow right to the
bottom (afterward, found that it had flowed down one side only). Well, can always put a bit more in
from the side later.
This epoxy is advertised by Bunnings as "slow setting". Probably a
bit embarrassing for the brand-name epoxies, that this one is so cheap,
so Bunning feel compelled to say something negative about it. I went
back for a look about 3 hours after having applied the epoxy, and it was
set, to my touch anyway.
7: Build water runoff
There needs to be a channel to direct distilled water into the outlet
pipe. It needs to have a gradual slope, toward the outlet. The waste
water outlet does not need anything, except it also would be nice to
have a gradual slope.
I purchased 0.3mm aluminium flashing, a large roll, even though only need a tiny piece:
| Aluminium sheet, 0.3mm |
$15.00 |
https://www.bunnings.com.au/consolidated-alloys-150-x-0-3mm-x-10m-weatherflash_p1100453 |
Just need a little piece, about 568x55mm, to guide the water that
falls from the glass, to the outlet pipe. As I only have basic tools,
had to improvise again. This shows how I bent the flashing:
What I ended up with is bent like this, the dimensions are approx. 20x20mm, 10mm bent over:
...the vertical part will be stuck against the bottom inside wall of
the distiller. I roughed it up a bit using coarse sandpaper, to try and
improve adhesion to the sealant. Then, glued it in, using the silicone
sealant. Used something (a mirror) to hold it in place until set:
...the distilled water outlet pipe could have been a bit further
down. I specified the notch as 12x12mm, which turned out just on 13mm
deep. So not getting much of a slope for the runoff. I have edited the
original 3-dimensional sketch (above) and changed the notch to 12mm wide and 15mm
height. But it is OK as-is, will still work.
8: Finish water runoff
Making this as another step, as need to wait overnight for the
aluminium flashing to be reasonably well glued in place. Next day, can
do some finishing-off.
Currently there is no slope for waste-water runoff. Not essential,
but decided to put in a slight slope. This was done by cutting a strip
of aluminium flashing, and embedding it into sealant.
9: Install legs
Originally, I planned to construct folding legs, however, decided to
go for the easiest solution, screw-on legs, using ready-made legs from
Bunnings:
| Table leg, 735mm x2 |
$10.00x2 |
https://www.bunnings.com.au/leggz-735mm-round-plain-wooden-table-leg_p3940091 |
| Table leg, 400mm x2 |
$7.50x2 |
https://www.bunnings.com.au/leggz-400mm-round-plain-pine-furniture-leg_p0038654 |
| Angled leg plate, 4 pieces |
$2.20x2 |
https://www.bunnings.com.au/adoored-5-16-angled-leg-plate-2-pack_p0101572 |
| Screws, 8G 15mm round head |
$3.98 |
https://www.bunnings.com.au/zenith-8g-x-15mm-galvanised-button-head-stitching-timber-screws-35-pack_p2410091 |
The legs have bolts sticking out of them that are too long, so I
created spacers by cutting some of the 16mm MDF into 50x50mm pieces,
with holes in the middle.
Oh, about this time, also put epoxy into each end of the inlet pipe.
The leg plates were affixed with the 8G 15mm screws, pre-drilled, and
with extreme care not to drill right through. Used some of my Parfix
silicone sealant as glue for the leg plates.
Note, I used a 12mm thick base-plate, and the 15mm screws are too
long (I didn't have any shorter), so I sawed the tips off them. However,
I have changed the specification for the base-plate to 600x900x16mm
(see further up this page).
The resultant slope of the distiller will be 25 degrees, which is about what I want, at least for the initial testing.
10: Install cloth
Measure the required internal dimensions, and cut the bath towel with
scissors. Remember to leave that loop at the top, in which the rod will
be inserted.Cut the width reasonably accurately, so that the cloth isn't climbing
up the sides. However, if the length turns out to be too long after
insertion, it can easily be trimmed.
Cut the rod so it fits into the inside-width of the distiller. Width
is 568mm, but it does have sealant applied, so a few millimetres less
should be OK.
Bevel the ends of the rod with a file, and smooth with fine sandpaper, so it is easy to insert into the cloth.
Insert the rod into the bath towel, then feed the bath towel in at the top, under the inlet pipe. For the dimensions that I have constructed to, it is a pretty snug fit.
11: Install glass
I purchased the glass from a business named "Glass Perth" here in
Western Australia. Actually, I bought two pieces for $90, including
bevelling of the edges, so I guess that will be $45 for one 600x900mm
piece:
| Window glass, 600x900x3mm, bevelled edges |
$45 |
http://www.glassperth.com.au/ |
The glass will sit on top, with a soft gasket between it and the wood
frame. I was thinking of using the silicone sealant for the gasket,
however, decided to use EPDM sponge rubber:
| EPDM sponge rubber, 13x3mm x4m |
$21.80 |
https://www.clarkrubber.com.au/epdm-sponge-seal-13mm-x-3mm |
This stuff is reasonably inert, however, is not the optimum choice
for hot potable water. Silicone sponge rubber strips are available, but
couldn't source them locally -- a quick look on eBay, could not see the
required dimensions.
Anyway, the EPDM sponge rubber will do for now, while I continue
searching for alternatives. Would prefer white gasket, if possible.
The 3mm thickness is minimal. If the frame has a twist in it, then thicker gasket would be required.
I used little dobs of super-glue to hold the sponge rubber in place,
and put the glass on top. Then cut some aluminium 40x12mm angle, to
firmly hold the glass pressed against the sponge rubber. The angle was
purchased from Bunnings:
| 40x12x1.6mm x1m aluminium angle |
$8.72 |
https://www.bunnings.com.au/metal-mate-40-x-12-x-1-6mm-1m-aluminium-unequal-angle_p1138181 |
I used the 8G 15mm screws, pre-drilled, and drilled with great care
so as not to go right through the sides. Each piece was 25mm long.
Note, I used a permanent marker pen to write on the inside of each
bracket, its position. As the holes are not positioned exactly the same
on each bracket, this is a wise precaution if the brackets ever get
removed.
12: First evaluation
The day is Wednesday 12th June, 2019, here in Perth, Western
Australia. It is mid-winter, and the rain has finally arrived. This day
though, it rained overnight, but just very overcast all day. The sun
peaks through the cloud sometimes, briefly, as the clouds are moving.
I setup the distiller just after midday, and here is a photo just after having connected the water supply:
The collapsible water-holder and plastic pipe was obtained from
Bunnings. The pipe is not UV-resistant, so for long-term usage, I have
this silicone pipe on order:
| 12x14mm (IDxOD) silicone pipe, 5m |
$16.29 |
https://www.ebay.com.au/itm/5m-6-25mm-Clear-Silicone-Tubing-Tube-Hose-Pipe-FDA-High-Temperature-Resistance/123692957857 |
After about half an hour, took some temperature readings. Ambient was
17degC, pointing the infrared thermometer at the front of the panel,
got 22degC, and at the back of the panel got 21degC.
What really surprised me, is with so little sun, and such low
temperatures, the panel was producing distilled water. Here is a photo
at the half-hour point:
After about an hour, measured 30 millilitres output. OK, that isn't much, but I was surprised that it was working at all.
I need to wait for a day with clear sky, looking forward to that.
The panel works. First impressions, though, the legs aren't so good, a
bit wobbly. I will need to rethink the legs, and might just use
interlocking plywood. Firstly, though, want to conduct some experiments
with different angles -- it is currently 25 degrees.
13: wind-up
Total cost of materials: $218.25
This includes $15 for a roll of aluminium flashing, that I only used a
very small piece of. And a few other items only partially used, such as
screws and plastic pipe.
The distiller is built, and works. For me, there is no particular
reason to build any more prototypes, though I can think of various improvements.
Yes, I am interested, very interested, but there are other projects to
work on. There is also the question of cost -- for me, it would be
wasteful to build more, and just discard the earlier prototypes.
I might be persuaded to do something more if someone gives me a
PayPal donation! However, where I can see further innovation is readers
of this page using these instructions as a starting point, and building
something better.
I have various thoughts about improvements, below the horizontal
line. Read it, see if any of it can be used in your "improved"
version...
Improvements & other cogitations
If you would like to have a go and build one of these, please read
these notes. I intend to append to this page as further ideas occur.
These DIY plans are intended as a starting point, and it will be great if refinements are made. Anything else that you can think of to improve the design, go for it, and report the results. If it turns out well, I will probably do a feature blog post showcasing your creation.
Pine instead of MDF
I have used standard MDF, that is not weatherproof.
However, I intend to keep it in the back of my car, and only set it up
when there is fine weather. Or, if there is rain, it could be left out
with a tarpaulin over it.
Silicone sealant lining inside the still should prevent the MDF from
getting damp while operating, but external rain is the problem. In fact,
the still could be used for rain collection, if suitable catchment is
attached at the bottom.
If you do want it to be in the rain, for whatever reason, I suggest
use marine-plywood for the base-plate and pine sides. In that case, you
will have to find a silicone sealant that bonds well to these.
Selleys 401 does not, which I think is due to it being acetic (acid)
curing. I think that a neutral-curing silicone is required. Furthermore, it has to be
specified for both potable-water and continuous exposure to steam. If you find such a silicone, let me know. Preferably clear, white, or other very pale colour.
Another consideration is strength. MDF is pitiful compared to pine,
even compared to plywood. If you want the distiller to be as rugged as
possible, probably MDF is not the best choice. And, if it turns out that
there is a leak from inside, the MDF will perish, whereas pine and
marine plywood will not.
Another consideration: for prototype #1 I used premium plywood from
Bunnings, which is rated for external use. I left it on the lounge-room
carpet for a few days, and found that it had warped slightly. Heck, I
even had trouble at Bunnings, finding one that wasn't warped. The MDF
seems to be more structurally stable, and all the sheets at Bunnings
were perfectly flat, and mine stayed flat.
A "super spreader"
You have seen in this page, the challenge that I faced with spreading
the sealant quickly and smoothly over such a large area. Well, there is
a possible solution: a spreader that is as wide as the inside-width of
the distiller.
Well, not quite. Make it a few millimetres shorter, and maybe bevel
the edges inward a bit. What I was thinking of, is to use something like
this: https://www.bunnings.com.au/metal-mate-23-8-x-12-x-1-5mm-1m-aluminium-gutter_p1079276
Pop-rivet some plywood onto that, to allow firm grip with both hands.
Then, after having ejected all of the sealant onto the surface, in the
zigzag fashion as described above, just one sweep down with the
super-spreader should provide a super-smooth finish over the entire
inside surface.
Of course, some will run off the side and be deposited on the inside
walls. That is fine. use one of the flexible spreaders on the side walls.
Another thought: spread the silicone on the plywood before the
side-pieces are attached. Then you have a completely flat surface to
work on, and it won't matter if silicone goes off the sides.
Alternative silicones
I used Selleys 401, however, there are possible alternatives, for example, this is cheaper:
https://www.indrub.com.au/prosil-10-100-neutral-silicone-300g-cartridge.html
OR:
https://www.indrub.com.au/prosil-20-100-acetic-silicone.html
Another contender:
I cannot say whether you should use acetic or neutral cured silicone.
It is a matter of testing and see what ticks that you can get in this
table:
| Product | Plywood (pine) | Dressed pine | Standard MDF** | Cured sealant* | Glass | Aluminium | Acrylic paint |
| Selleys 401 silicone sealant, acetic curing |
|
|
|
|
|
|
|
| Parfix Roof, Gutter and Concrete silicone sealant, neutral curing |
|
|
|
|
|
|
|
* Cured sealant is the same type as that being applied on top.
** Made from pine, no waterproofing treatment.
Note, do not use Parfix "Roof, Gutter and Concrete" sealant, it is not rated for potable water. It is just in the table for comparison.
The columns that you require ticks in, depends what materials that you will be using. Definitely though, you will will require a tick in the "Cured sealant" column.
As for the colour, clear, white, or any very pale colour is OK. Do not use black, as we do not want heat to be absorbed into the wood.
If you test a silicone, send me the result, then I can offer more choices in this table.
Epoxy instead of silicone
For coating the inside of the distiller, the above plans have used
silicone sealant. However, "food grade" or "potable water" grade epoxy
is a possible alternative.
For example, Dulux Durebild TLE: https://www.duluxprotectivecoatings.com.au/products/ranges/durebild/durebild-tle/
This is rated for immersion in hot water up to 100degC, potable
water. The technical data sheet states that it is subject to yellowing
with long-term exposure to sunlight, however, will retain its protective
properties.
Having not used it, I cannot say which method of application to use.
It can be painted, and will accept multiple coats. It is probably
expensive.
Improved legs
As mentioned, the screw-on legs are a bit wobbly, not going to be
good in wind. I am thinking of plywood panelling, maybe that slots
together. Or, could do folding legs. Also, a frame that you can put
something heavy onto, to hold the panel down in wind, such as rocks,
will be good.
Have fun!
Regards,
Barry Kauler
(c) Copyright Barry Kauler, June 2019. All reproduction rights
reserved. That is, please do not copy this page to any other site,
instead link to this URL: http://bkhome.org/nomad/diy-solar-water-distiller.html
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