If you're growing your own fruit and vegetables, or just trying to eat the things that are produced locally, you come across one obvious problem: when something's in season, you have more than you can handle, and then there's nothing for the rest of the year. So the obvious solution is to preserve your food when you have it in abundance. Dehydration is an excellent preservation technique that's easy to do and that maintains a lot more of the original nutrients than canning or freezing.
However, a couple of years ago when we started to look around for a dehydrator to buy, we were sorely disappointed at what was available. A unit that could process any decent amount of produce was several hundred dollars, and they were all electric. We live off-grid, with solar and wind powering our home, so energy efficiency is a serious consideration for us. But it's also just common sense - why waste electricity on something when you have a perfectly good sun outside the window that can do the job just as well. So we got to working on making our own dryer, using the sun as the heat source, and it turned out not to be that hard or expensive. Within one weekend, we had the unit finished and ready to go, and we have been using it ever since.
So, what's the concept of a solar dryer? It's simple: move warm air over thinly sliced food. The warmer the air, the more moisture it can remove from the food. However, you don't want the air to move too quickly, as that will cause the temperature to decrease. Our design creates just enough air movement and warmth to dry food quickly.
The food is on trays, which sit behind a transparent polycarbonate sheeting. Below the trays, there is a metal shelf, painted black, that serves as a heat absorber. As heated air rises through the food, cool air is drawn in through the bottom vent, and the heated, moisture laden air flows out the exhaust at the top.
Because the dryer is something we plan to use for many years to come, we decided to make ours out of metal. If you do not have access to a welder, you can make the frame out of wood, but will have to adjust these plans accordingly.
Step 1: Materials and Tools
- 40 ft of 1" square tubing
- 16 ft x 3 ft sheet metal
- 2 ft x 8 ft polycarbonate greenhouse panel
- 2 hinges
- 11 pieces of 8 ft long 1" x 2" lumber
- 16 ft x 2 ft food-safe screen
- 2 thin wooden moulding, 48” long
- self tapping metal screws
- wood screws
- metal chop saw
- tin snips
- tape measure and marker
- framing square
- wood saw
- box cutter