Solar Food Dehydrator
by Robin Green
Hi, this is Robin from Green-Energy-Efficient-Homes.com
Years ago I built a solar food dehydrator without really paying much attention to how others had done so. This was before the Internet so you couldn't just search for good designs and copy them. My dehydrator consisted of a box about 3x3x3 feet, propped up on a 3-foot high platform, with a collector that ran from the ground to the bottom of the box, so that heat would rise through the collector and into the bottom of the box, and from there rise to the top.
I built trays for the dehydrator by putting slots inside the box and building wooden frames over which I spread window screen material. The dehydrator could hold about 15 trays.
We had bought a 3 gallon pail of sour cherries and I decided that would be the first thing I would dry in it. I put the cherries on the trays and stuck the trays in the dryer, then positioned the dryer in my back yard facing south.
There were a few problems. First, my back yard was at the north end of the lot, so my house created shadows on the dryer in the mornings - I only had full sunlight from noon on. Second, the day I started drying was overcast, and it never really got all that sunny during the 3-4 days I ran it. I believe I had actually rigged up an electric fan to help blow air through the solar dehydrator, but it's been so long I can't recall!
In any event, while the
inside of the solar dehydrator did get warm some of the time, it never really got to the ideal 110F or higher that's required to effectively dehydrate food. As a result the cherries started to ferment, and then the alcohol turned to vinegar. In the end I had wet cherries that tasted like vinegar. I managed to salvage a couple of mason jars full of vinegary cherries and steep them in white vinegar so I had a good vinegar for making salad dressings, but most of the cherries went in the compost. As for the dehydrator, I left it in the garage for a year or more and finally admitted defeat and cut it up. When I moved to our current house, I cut the 2x2 framing (which had been made of salvaged oak) into 1 foot pieces and used it in the fireplace insert in my living room - that was about the only decent heat that solar dehydrator ever produced!
What did I learn from this? If you want to do a DIY solar power project, at the very least do lots of research beforehand. Don't do your own design - start with a design that is known to work. Make your own design a second or third project after you've proved the first one works.
Also, start your solar dehydrator tests out with a few banana slices (cost: $0.20) instead of a bucket of sour cherries (cost: $20 plus $10 to drive to the farm to buy them).
Finally: check the long-range weather forecast before you put things out to dry!