Solar Heated Large Scale Dehydrator

I like to dry food for canoe and backpack trips. I have been using a commercial dehydrator that did the job over a couple of weeks. Then when my daughter decided to dry yarrow for a local store that makes a cream, the system got overloaded.

So… I built this dehydrator. It is much larger in scale than my previous dehydrator, uses solar energy as the heat source and a recycled fan to move air across the screens. It is also easy to load and unload.

Step 1: Design of Dehydrator

When I designed this dehydrator, I wanted to be sure that air was free to circulate across all the screens, that the dehydrator not impart anything to the stuff being dried and the heating process was effective and inexpensive.

The dehydrator is a basic box supporting a number of screens with a fan moving air across the screens, glazing on one side, brackets that separate and hold the screens, an air distribution system, a large door and that moves air across all the screens.

Materials

• 7 screens 17 3/8" by 30 5/8" (I found the aluminum frame with fiberglass screens at the local recycle station)
• 32" x 24" glass glazing
• 2 @ 24" by 18" 1/2" plywood
• 1 @ 32" by 24" doors
• 1 @ 32" by 18" 1/2 plywood
• 14 @ 1 1/2 by 3/4" by 17" spruce
• Waterproof glue
• Screws
• 4" PVC with recycled computer fan
• wide foil to line the back and sides of the box

Step 2: Making the Box

Half inch holes, spaces at 3" intervals 1" from the top are drilled along the top edges of the two ends and the door. The two ends are glued and fastened to the top and bottom plywood. The glazing face is caulked with silicon then drilled and screwed in place. Glue foil on the inside of the ends, top and door surfaces. The foil on the two ends with also be held in place by the brackets.

The screen brackets are fastened to allow about 1/8" clearance between the bracket and screen. This allows the screen to be moved in and out freely.

The door at the back of the box is fastened with a piano hinge so that it can open fully to allow the screen moved in and out.

Step 3: Installing the Air Circulation System

A 4" hole is drilled near the base of one end. This hole is fitted with a PVC pipe that holds the computer fan that pushes air through the screens. The air is distributed passing through a screen that has restricted openings. A hot glue gun closes off about 50% of the screen. When the door at the back is opened the screen can slide in and out of the brackets.

Step 4: Using the Dehydrator

You want to dry on a sunny day with low humidity. Slide out all six trays.

It is best to coat the screens with a cooking spray so the sugars in the fruit don't stick.

Place the fruit, veggies, meat or meals you want to dry on the trays leaving space between the items. If you are drying a meal like chili, then put the chili on the top screen.

Close the door and place the dehydrator so the glazing is facing the sun then plug in the plug in fan.

Check the dehydrator every couple of hours. On a hot sunny day, it may get hotter than you want for fruit and vegetables, so put something in front of the dehydrator so it is in the shade.

Fruit should be dried until it has a dry but rubbery texture but vegetables can be dried until they are brittle.

Adding water reconstitutes the fruit, vegetables or meals.

The weight is greatly reduced (something important when a portage is on the canoe route).

Dehydrated chili is only about 1/4 the original weight and, left in a baggie for the day, reconstitutes so that it is hard to tell from the original. Try this with a dutch oven corn bread. My mouth is watering just writing this.

Comments

[UNSEPARABLE TECHSCIENTIFICS]

EXCELLENT WORK!!!

GOOD IDEA FOR EVERYBODY!!!

[chunkerbutt02]

What kind of screens are you talking about, and won't the bugs get in.

[gtoal]

Don't insects get in through the holes in the top? I live in a hot climate (south texas) and would be inclined to do this rather than use an electric dehydrator but I guarantee that drosophila, flies, and ants would be all over it if there was the slightest entrance for them to use.

[camilo.zuluagag]

you can put a mesh with thiny holes, i rocomend that in all vents, included the fan air supply.

[admiraldre]

Nice design. A recycled computer Fan " 12 volt DC" and a small solar panel would make this portable and wireless. Also wouldn't you get a lot more heat gain if the outside of the box was painted Black? David Jamestown RI

Sorry I missed the word Fan the first time.

[admiraldre]

Nice design. A recycled computer " 12 volt DC" and a small solar panel would make this portable and wireless. Also wouldn't you get a lot more heat gain if the outside of the box was painted Black? David Jamestown RI

[boy2man]

I have a question for this tool (or equipment) to dry food.

How many food this tool can dry per time ? How long to dry food ?

[Webuildwaterfalls]

Thats really cool !
and gtoal, a few bugs aint gonna Kill Ya!

[sash99]

I've built solar dehydrators before, you would of being better to of had the box twice as tall. and installed the glass portion on the bottom 1/2 and have that bottom 1/2 dark in colour with a screened air intake along the bottom edge of the glass ( even slant for better solar gain ). then have the upper portion for drying your food stuff with a screen chimney around the outside upper edge . then it would not sun bleach your food and would create a natural even convection that would dry your food thoroughly and quickly . with out the use of fans

[Agio]

can you point me to resources or pictures with this type of design?.

[sash99]

it in german but you should get the idea from it a book printed in 1983.

https://www.dropbox.com/s/g5bp9vi7d3j24s7/03271101...

it actually quite an intereresting book, from building your own bio digester to making your own cheese - "handbuch fur bessere zeiten" by Rudolf Doernach. whether you German read or not It has alot of interest stuff

[YLBright]

Instructable????

[Steinzel]

Nice one! A filter on the air intake and a solar powered fan would be a nice addition.

[cwheit]

I wonder if it would be possible to add some type of reflector around the air intakes to increase the heat of the incoming air

[GrumpyOldGoat]

A good furnace filter to keep the dust and bugs out would be a good addition.

[ClemRz]

Hi, nice job!

Why do you use active/non-renewable-powered system (electric fan) when you could use the same passive/solar-powered system to move the heated air? See that example: http://i39.servimg.com/u/f39/17/92/54/52/deshyd12....
Thanks!

[ClemRz]

This one is actually a better example of what I'm trying to explain: http://ecolib.free.fr/textes/agrialim/sechpro1.JPG

[deankosmac]

Freaking nice!
Can you tell me how long did the apples dry? Can you please provide us with some test examples of temperature in this box?
I really appreciate this tutorial!

[ajofkandy]

Nice job! I was thinking of something like this. I do not have any experience in drying food. I was wondering, do you think it would help if you add a humidity controlling mechanism inside the dryer?

[iminthebathroom]

This is inspiring