Tyler Uebele

Dehydrators are useful for drying food quickly so that it can be stored longer without spoiling. Foods like beef jerky, banana chips, "fruit-roll-ups" and dried herbs may be familiar examples. A solar dehydrator would, of course, dehydrate your food with solar energy.

Two friends of mine have a garden and like to dehydrate some of its produce. They also are interested in being kinder to the environment, but without all the "Green" hype. These two interests together inspired the idea of using a solar dehydrator, and consequently, my building one.

The design is simple and found in variations all over the internet. I've checked out various designs and settled on my own variation. The solar dehydrator has two main parts: the heat collector, and the food chamber. The heat collector is a long channel painted black inside with a clear top which is heated by direct sun, since hot air rises, a steady flow of hot air passes through the food chamber at the top of the heat collector. The food chamber has a vent at the top to allow air to leave after passing over screen trays of food to be dried. Ideally, the temperature in the food chamber should be hot enough to dry the food quickly, but not so hot that it cooks the food.

Measurements

My heat collector is 18" wide, 6" tall, and 6' long on the top side. The opening at the top is 12" deep to match the bottom of the food chamber, leaving the bottom of the heat collector at 6' 10". The food chamber is 18" wide, 12" deep, about 23" tall in the front, and about 29" tall in the back. The slant accommodates a tilted roof and an exit vent. The door is in the back.

Materials

For this project I used the following materials:

1. ⁷/₁₆" x 4' x 8' OSB sheet for the panels.
2. 7 of 1" x 2" x 8' cedar board for the frame
3. 2 of 1" x 4" x 8' cedar board for the frame
4. 10 of ¹¹/₁₆" x ¹/₂" x 8' pine for the trays
5. 3 of 18" x 24" acrylic sheets for the clear top
6. 36" x 84" aluminium screening for the vents and trays
7. 24" x 8' corrugated tin roofing for the heat collector, and food chamber's roof

The following other supplies were needed:

1. Elmer's wood glue for all seams
2. 1 ¹/₄" deck screws
3. silicone sealant for the acrylic seams
4. 2 of 12 oz can black spray paint cfc free
5. small finishing nails

... and of course, the related tools: saw, drill, screwdriver.

Construction

I started with the heat collector. First I measured, measured, and cut the frame and panels. I used cedar for the frame because it stays straight and bugs don't like it. The frame is smaller than 18" by the thickness of the OSB. I attached the aluminium screening to the bottom end of the frame before attaching the panels to ensure a tighter fit. Every connection is glued and screwed. The extra cross pieces add lateral support and a place to bind the acrylic to later, spaced 24" on center for that reason. I used six feet of the eight foot tin roofing I bought to place inside the solar collector to increase the efficiency of heat transfer. Then I painted the whole thing black to increase solar absorption.

The food chamber I did second. I laid out the OSB I had left and determined the tallest I could make the box with the material remaining. A cedar frame was built in similar fashion to the solar collector: glue, screwed, and to support a box with an 18" x 12" exterior dimension. An extra cross beam supports the exit vent screening and the door hinges. For the bottom screening I tried something different: attach it first to the paneling and stretch it over the frame when applying the panels. This was the inferior method to the first method.

After I completed the frame and added the side panels, I started added the tracks for the trays to be built later. I used the small pine for these, spacing them with the wider dimension of the pine strips, I had enough space for 13 tracks. The trays would be built later. I used the small finishing nails to tack the tracks in place. When the tracks were all in, I added the front panel and the back door.

Making the trays was perhaps the most tedious part of this project. Fortunately I was able to borrow a chop saw to cut all the small pieces: 15.25" and about 11" with 45 degree cuts. I used glue and staples to bind the corners, then stapled the aluminium screening to all of them as they set. I had just enough for the trays after what I used for the vents.

Still To Do

I have to attach the remaining two feet of tin roof to the roof of the food chamber, attach the food chamber to the heat collector, attach legs to the whole unit, and deliver it. Since the fully assembled unit will likely not fit in my car, I may assemble it on site.

Final Assembly

With the back seats down, the front seats all the way forward, some strong-arming, and my knees hugging the steering wheel, I managed to fit the parts in my car and deliver them. Assembling the two halves was not complicated, but quite cumbersome. Laying them in place on side on construction horses and connecting them with the cedar boards meant for the back legs we managed to assemble the solar dehydrator whole. I found it necessary to remove the trays while maneuvering the food chamber, naturally a local cat found her perch. Trimming some length off the back legs to make the front legs, we completed the project and hauled it off to its new home. By this time the sun had set, so we were unable to test it. I haven't heard yet how my first attempt at a solar dehydrator performed, but I look forward to finding out.