Need ideas on how to build a solar dehydrator

VT-Chicklit

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I want to build a solar dehydrator using passive solar technology to dry fruits and veggies in larger quantities than my small dehydrator with round trays can accomplish.

I want the size to be about 3' x 2' x 4' (l x d x h) and I plan on using the old fashioned window screens that expand for myshelves. I am concerned that there will be too much humidity trapped in the box if it is not vented properly. I had thought that I would use a piece of plexiglass that I had for the door an thought that I would drill a 3" hole at the bottom of each of the two sides and a rectangular 3 x 5 inch hole at the top of the back. All the holes would be covered with a fine screen or mesh. I thought that I would place a narrow board on the outside of either side that I would use to support the box at an angle inorder to catch he best of the suns rays. The box would be painted a dark color to maintain the heat.

Any suggestions? Do you think that those holes would provide enough air flow to prevent molding of the veggies?
 

xpc

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Normally the vents would be at the top and be adjustable so that all the warm air has to travel thru the food to get out, sliding the vents open or closed will regulate the temperature so you don't end up cooking anything.

Are you using a slanted window box as you heat generator?
 

VT-Chicklit

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My intent was to slant the box that I build and have the screen shelves inside. The plexi glass will cover the open front of the box and be pointed toward the sun. This box will be slanted to get the optimum amount of sun.
 

unclejoe

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Here is the one I am working on now. It's a little bigger than what you are looking for but it's all I have. It' nearly 6' high, the drawers are 24" wide and 30" deep. ( I plan on drying a lot of stuff in each batch ). In the lower right corner there is a screen for photo purposes. The finished product will be a triangular box with glass on the top section and screen on the sides to allow air in.

335_camera_024.jpg

The vent is a standard 6" chimney pipe which will have a damper in it to control the heat build up. It will also have a cap to prevent rain or dew from getting in.

335_camera_026.jpg


A single sheet of plywood mounted on a piano hinge will be the access door for the drawers. The angled top and face will be glass and the entire unit will be painted black. Hope this helps.
 

freemotion

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unclejoe, would you be so kind as to post a picture of the completed project as well?
 

Wifezilla

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Great start!

Since I live in Colorado, I cheat. When we had the trampoline, I would just spread stuff out on that and cover it with cheese cloth. There were people a few block away from me and they used to lay a sheet out on their driveway and use that to dry peppers.

Now that the trampoline is gone, I will have to use the hot tub cover :D
 

xpc

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unclejoe that's a nice setup, if you are looking for some unsolicited advice I would build a slanted window box exactly where you have that window screen leaning in the first picture.
Paint the inside of the new slanted box black and cover with glass, put some holes in the bottom under the glass and cover with fine mesh screen, you can also put a damper there to regulate air flow. I would also leave the design just like you have it with the glass on the top too, but add the second removable slanted glass box at the bottom.

This method forces the warm air to circulate thru the food to quicken the process and lessens the chance for rot, you would also not need any other vents or screens except above the food for exhausting (and the one below the window).
 

unclejoe

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That's exactly the way it was designed. I guess I didn't explain it very well.
The slanted screen is there just to show what it will look like when it's done. In place of the screen will be a detachable, triangular box. Where it attaches to the main unit, it will be an air intake. The angled part will be glass and the sides will be screen. The top angle and front face is glass down to the box. And yes, the entire thing will be painted black. The gray is just primer on bare wood. Today I picked up 6 storm window screens off freecycle for the tray's and that lower air intake. I already have the glass, which I also got off freecycle a couple months ago.
Now that I have all the materials, I need to make the time to finish it. :rolleyes:
 

xpc

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Ha ha good deal then, have you or anyone else ever jerked meat in a solar dehydrator?
 
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