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 is 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, and drying with the sun is one of the easiest, most energy efficient ways to do so. It also maintains a lot more of the original nutrients than canning or freezing.
The concept of a solar dryer is 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.
40 ft – 1″ square tubing
16 ft by 3 ft – sheet metal
2 ft by 8 ft – polycarbonate greenhouse panel
2 – hinges
11 – 1X2 by 8ft lumber
16 ft by 2 ft – food-safe screen
2 – thin wooden moulding, 48” long
self tapping metal screws
metal chop saw
tape measure and marker
You can make the frame any size you want, but I settled on 48 inches long by 18 inches wide. This was the size that I could cover from one piece of 24”x96” polycarbonate.
Attach the door with hinges and a latch.
You now have a brand new solar food dryer. To begin with, make sure the dryer sits in the sun for a few days to allow any fumes from the paint and silicon to escape.
Test the dryer using 2 trays at a time, then increase to 4 trays if weather is clear and dry. Slice food as thin as possible (1/4”) to hasten drying time. I like to keep an oven thermometer in the dyer to see the inside temperature. Ideally, you want it to be about 130 degrees F. If the temperature is lower than this, you can reduce the size of the bottom vent with a piece of cloth.
Foods can be re-hydrated before using, if needed. You can dry leaves, roots, fruit, vegetables, nuts, fruit pulp, and anything else you can think of.