Week 24 -Solar dehydrator

 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.

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.

Step 1: Materials and Tools

Materials

You can also get second hand materials and nake your solar panel according the your materials measurement. 

• 40 ft of 1" square tubing
• 16 ft x 3 ft sheet metal
• 2 ft x 8 ft polycarbonate greenhouse panel
• 2 hinges
• latch
• silicon
• paint(black and water resistant paint for outside)
• 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

Tools

• welder
• metal chop saw
• drill
• tin snips
• tape measure and marker
• framing square
• wood saw
• box cutter

Step 2: The Frame

Step 3: The Door

Step 4: The Covering

1. 

Step 5: The Trays/Screen

Step 6: Using

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 the weather is clear and dry. Slice food as thin as possible (1/4”) to hasten drying time. We like to keep an oven thermometer in the dyer to see the temperature inside the dryer.  Ideally, you want it to be about 55 degrees. If the temperature is lower than this, you can reduce the size of the bottom vent with a piece of cloth.

Foods can be rehydrated before using, if needed. You can dry leaves, roots, fruit, vegetables, nuts, fruit pulp, meat and anything else you can think of.

Resource: https://thepermaculturecollective.com/building-a-solar-dehydrator/