Humid Climate Solar Dehydrator

This dehydrator is my version of an upper Mid-west design. I adapted it (as recommended) to fit the windows I had on hand, which I also use for my cold-frames. These windows were roughly 32" by 32", which matched nicely with 32" wide galvanized roofing. I couldn't get the wavy kind in my area, only the ribbed, so had to adapt the screen support system accordingly. I used cedar throughout for to withstand weather without coating it with any preservatives or paint. It also makes the frames really light so I can put them on a 4 1/2 foot high shed roof.

Materials (for two dehydrators):

3 1x6 3/4" 6-foot cedar boards (these are fencing boards in my area - I picked for few knots)
1 sheet of 8-foot galvanized ribbed roofing (is enough for 3 dehydrators)
2 yards of 36" aluminum flashing
2 32" x 32" storm windows (or other similar sized glass)
Matte black spray paint
2 yards of 36" aluminum screen
Staples
Galvanized nails (1 1/2")
1" finishing nails for drying screens

Tools:
Jigsaw with metal-cutting blade
Tin snips
Table saw with rip fence to produce frame elements
Stapler

Step 1 A Simpler List of Materials

Two years after initially publishing this Instructable, I found myself conducting a Saturday build of three smaller dehydrators with three friends of mine.  I found 3 windows of the same size at the local Habitat ReStore and worked everything from there.  I also wanted to get the three of them done in less than a day, so I went with materials that simplified things.

For each dehydrator:

1   24"  x 27 3/4"  storm door window
Dehydrator bottom: Aluminum flashing,  white on one side, shiny on the other:  24" x 27 3/4"  (no need to trim ribs)
Heat sink: Aluminum flashing,  black on one side, white on the other:  22" x 26"  (no need to paint)
Nylon screening:  24" x  30"  (easier to work with than aluminum screening)
3  1" x 6" x 6' cedar boards:  one ripped 3 1/2" wide (for top and bottom),  one ripped 4" wide (for the sides),  one ripped into 1" wide pieces (for tray frames).  Once the pieces are cut for the box, rip the remainders into 1" wide pieces.
scrap 2" x 2"  (about 4" - 6" long) for heat sink handle
1 1/4"  galvanized spiral nails  (for making the dehydrator trays)
1/4" staples
8  1 1/2"  deck screws  (to hold the outside box together)

For this size,  the top and bottom were the 27 3/4" sides of the window.  

Because the flashing doesn't have ribs,  you'll have add "risers" to the long sides of the trays using scraps of the 1" wide pieces.  The flashing is much easier to cut than galvanized roofing!   We cut the screening oversize for the trays and found the nylon easier to stretch tight than aluminum screening;  it was also easier to trim once the top pieces were nailed on.

We completed three dehydrators in 4 hours.

Comments

[faun108]

Thank you for this inspiring instructable!
I asked myself however if you checked the temperature? I want to build a solar dryer for herbs and most plants should not be dried over 40 degrees celsius. Any expericence or ideas?

[amtrudell]

Hmmm, I'd heard you shouldn't dry plants over 140 degrees Fahrenheit, which translate to 60 degrees Celsius.

Using this dehydrator in south-eastern Ontario I routinely dry herbs and greens in it. On a day with full sun, a steady breeze from the south, moderate humidity (60 % or less), and air temps higher than 32 deg Celsius, I have had thin leaves begin to brown in the mid-afternoon when I've put them in in the early morning. That's an indication things are too hot. When those conditions occur, I either don't dry or I check things at noon and every couple of hours after that.

This dehydrator is not suitable for a low-humidity, extended high-temp climate (like the desert).

[faun108]

Thanks for your reply! It´s very much appreciated! I will experiment with it and maybe put a thermometer inside, to get a better idea of the development of temperature.
Best wishes!

[jonnyarmony]

Hey I was wondering if this model of a dehydrator can be stacked on top of each other. This would be useful, as to not take up so much room.

Also, I didn't see you mention many vegetables that you dehydrate. I imagine that this will work for most, but will it work for carrots, celery, peas?

[amtrudell]

A friend of mine made a dehydrator of this design last summer and he was drying all sorts of things with it: onions, carrots, sweet peppers, tomatoes, blueberries, peaches, strawberries.

Check out books on dehydrating from your library or at Amazon. I got one, not so much for the electric dehydrator times, as for recommendations on how to cut up various things and if they should be blanched before drying them.

[guy90]

Very informative and useful, thank you for the upload

[shilohjim]

Is the aluminum screen food safe? I worry about acidic foods reacting with it.

[amtrudell]

Probably not the best for acidic fruits. If you can find stainless steel screen (I've seen expensive US sources for it on the Internet), that is probably the best for everything and would definitely be stronger. My solar drying season is best for vegetables and herbs (non-acidic). Viole fabric (the stuff of sheer curtains) could be put on top of the aluminum screens to prevent or at least mitigate the reaction you worry about. I was thinking of trying that for things like mashed cooked sweet potato patties or winter squash patties. I use viole for juice straining and by chance I left a small bit of rhubarb pulp on it last week, but the bit peeled right off once the viole and it were dry. Also, if you start the drying process with the fruit skin down on the screen, you would certainly minimize any acidic reaction (top of the fruit would be surface dry when you turned it over on the second day or so).

[imrobot]

will this work for meats?

[rimar2000]

Very useful work.