Hi Everyone,
Today I'm going to show how I built this solar food dehydrator.
First we'll start with making the base. The entire frame is made with 2 by 3 by 12 foot
pieces which minimizes the scrap. The final base size is 36" wide by 48" deep. Depending
on the width of the glazing, you may want to make yours slightly more narrow because
the finished plywood will make the body about 36.5" wide. I decided to use construction
adhesive at all the seams along the exterior to help to minimize air from leaking at the
joints. I'm not sure if it really matters, but it's just for peace of mind. The shell
is made from 3/16" plywood, but there's no problem using 1/4" if you can't find 3/16".
The rear wall acts as the chimney to help with the air draft through the dehydrator.
At the top, I cut each of the 2-bys at a 45 degree angle so I can put a small roof over
the vent to minimize rain from getting in the dehydrator. The plywood hangs over the
end of the 2-bys by 2.5 inches so that it can be used to anchor the rear wall to the
base section. The top of the sheet ends around 8 inches from to top. This is where the air
will exit.
On the front of the chimney, I cut the plywood at an angle so that it would match the angle
of the roof section. At the base of the chimney, I left it a couple of inches from the bottom
to allow the air to flow a bit easier into the chimney. This entire section is also glued
and nailed together.
Next is to attach the back chimney wall to the base. Just plywood holds the two sections
together with a little glue and nails. It may not look pretty yet, but I usually prefer
function over aesthetics. I then square the two sections and add a temporary cleat to
maintain their positions.
The solar collector is next. On mine, I made it 73.5" long and it draws the cool air in
from the back. However, most sheets of acrylic are around 70" long so you may want to make
this a bit shorter and draw the air in from the bottom. The top section is cut at a 45
degree angle so that it will match against the back chimney. Instead of using a full
sheet of plywood, I used to remaining sections of scraps. Since this joint is between the
solar collector and the drying racks, it really didn't matter if some air sneaks between this
joint. There should be around 6" of space at the top end of the plywood so the hot air
can get into the dehydrating area.
Before attaching the solar collector section, I added some rails along the rear chimney
wall. These are just made from some scraps that I ripped down to be around ¾" square.
They are spaced so the racks will be2" apart on center. I then made up some more rails
that are attached to a 2 by 6 that I ripped a 45 degree angle along its edge. This will
attach into the solar collector.
With the unit lying on its back, I attached the solar collector between the base and the
chimney wall with some nails or decking screws. This triangle shape makes the unit very rigid
and then the cleat can be removed.
To set the rails under the collector, I cheated just a little so I could make sure the drying
racks would be level with the racks attached to the chimney wall. I took two pieces of
scrap and measured the height of each rail and cut the scraps to that height. I then
temporarily attached the scraps to the new rails so they acted as legs to hold them at
the proper elevation. Then added some glue and screwed it into place through the collector's
plywood.
For one side of the collector I fastened on a piece of plywood. It doesn't need any structural
support so there are no studs built into it. At this point, I ran out of glue and I didn't
feel like going to the hardware store so I just attached it with nails.
When it's complete, the dehydrator will weight a few hundred pounds and I wanted to be able
to move it around and align it with the sun, so I made up an axle out of some scrap black
pipe and found some old riding mower wheels. There's always a good reason to save old junk
like these wheels!
For the door, I made up a few brackets and anchored them into the base. They are tapered
so when the door is resting on them, they will force to door tight against the frame.
Then around the rest of the perimeter, I made up some little turn-knobs that hold the door
in place. It only takes a few seconds to open and close the door. It's not a perfect seal
so at some point I may add a foam gasket in around the door frame.
One last piece is to add a little roof over the chimney so that it helps to keep some
of the rain out of the dehydrator.
The entire thing is painted with flat black exterior latex paint. It took about two quarts
to put on two coats. Even the sides should be painted so if the sun hits it, it will
help to keep it warm.
This next part is optional depending on your location. Here in the northeast, we need to
try to maximize our solar collection as much as possible. In sunnier areas, you should
test your dehydrator to make sure it doesn't get too hot whereas you start to cook your
food instead of dehydrating it.
Take some expanded steel plaster lathe and spray paint both sides of it with flat black
paint. It's best to just paint a few sheets together to minimize your paint loss as it
blows through the lathe. You can try to be complete, but don't worry about getting 100%
coverage. Then cut the sheets into pieces so that the width will fit into the cavity
of the solar collector. To mark the cutting line, I just ran a piece of tape along the
cut line since it was difficult to see a chalk line. Inside of each cavity install a cleat
that runs from about 3/4" from the top of the cavity down to the bottom. I stacked 5
layers into each section to absorb as much light as possible. I couple of sheetrock screws
hold them in place and I then touch them up one more time with some spray paint. As the
air passes up through the collector, it is forced through each of these "solar sponges"
and the heat that is absorbed into the metal is transferred into the air.
You can see as I stack each layer in the sun, less light is able to get through to the bottom.
Even though these are flat black, some light does bounce off of the surface, but a percentage
will hit the backside of the layer above it, helping to maximize the light absorption.
I also added one more wheel to the dehydrator. After attaching a cleat and painting it, I
attached a swivel castor to it. It makes it far easier to push it around now!
Along the bottom opening, it's a good idea to add some screening to keep the bugs from
getting up inside the solar collector....unless you like dehydrated grasshopper!
To attach the sheet of acrylic, I drilled a bunch of holes through it and fastened it
to the frame with some screws and washers. You want to make sure the holes are extra-large
because the acrylic will expand and contract with the temperature changes. The best trick
for drilling holes in acrylic is to run the drill backwards so that it will melt its way
through the plastic. When screwing the acrylic down, don't over tighten it so it can still
move around a bit. I had to add one little extra piece along the bottom because I purchased
the acrylic after I build the solar collector and had the wrong measurements....so you can
learn from my mistakes!
The last part of the project is to make some drying racks. I used some scrap lumber and
ripped it down to be about 3/4" square. Then I took some scrap plywood and made some corner
brackets and glued and tacked them to each corner. Next I stretch some fiberglass screen
over each rack and stapled it into place. After I ran out of the fiberglass screen,
I found some pet screening. It's a bit thicker and smoother and I'm finding that the food
doesn't stick to it much. I wanted to get some stainless steel screen, but it was far
outside of the budget.
After waiting for a few days for the paint to fully cure, it's finally time to give it
a test drive and move it to its new home near the greenhouse. We happen to have some fresh
peaches on our tree and sliced them up to about 1/4" slices. After a couple of days
of drying at around 145 degrees, it was time for a taste test. Not many of the slices made
it back to the house so I loaded it with a bigger batch.
Thanks for watching, please don't forget to like this video, subscribe to our channel,
and leave comments about your solar food dehydrator.