Introduction: Solar Heated Large Scale Dehydrator
Third Prize in the
Solar Contest 2016
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.
- 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
- 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.
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