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Building a Solar Food Dryer

By: Chris Hogan MSc - Updated: 26 Oct 2010 | comments*Discuss
 
Solar Food Dryer Food Dryer Solar

As more and more people return to using gardens for food production, as well as pleasant places to pass the time, there is renewed focus on garden buildings being used as storage places for produce. One way of using a shed or other garden building as part of the storage process is to build and mount a solar food dryer on the side of it.

Use a Solar Food Dryer to Prolong Food Life

A solar food dryer can make sun-dried tomatoes for you to keep and enjoy long after the tomato harvest has been and gone and that's not all they're good for. Many other vegetables and fruit can successfully be dried then reinvigorated by soaking for a couple of hours before using them in the kitchen; sliced mushrooms and raisins spring immediately to mind. Some people dry out flower petals to use for herb teas, and meat becomes jerky or biltong, depending on the flavourings and method used.

Wood is usually the favoured material for a home made solar food dryer although cardboard is much cheaper, just don't leave it out in the rain. There are two sections, a solar collector with a food dryer cabinet mounted above it. They are usually made separately so that the food dryer can easily be disassembled and stored through the winter months.

Part One: The Solar Collector

The lower section of the solar food drier is the solar collector. It is a wide shallow box with a translucent top, either glass (most effective) or clear plastic (cheaper and lighter). The bottom of the box should be black, either painted or lined. If you use aerosol paint leave it to dry for a couple of days to get rid of any solvents and other chemicals, you don’t want them contaminating your home grown vegetables.

The solar collector should have large holes in both ends so that when it is stood up, with the glass facing the sun, the air inside will be heated up and go out through the holes at the top. Cool air will come into to replace it through the holes in the lower end, which should be covered with metal gauze or thin cloth to prevent insects getting in.

Part Two: The Food Dryer

The food dryer is a square box with grilles or grates, to sit the food on, which allow the heated air to flow around the food. It's a good idea to slant the box lid one way or the other so that rain slides off. A key feature is a large slot either in the lid or at the top of one of the sides (possibly better so that rain doesn't get in) to allow the heated air to escape. Cover the slot as before to prevent insects getting in.

Mounting the Solar Food Dryer on Your Garden Building

Now fix the solar food dryer cabinet on the side of your garden building where it will get the most sun, high enough to allow the solar collector to be mounted underneath but not in its shadow, allowing the bottom to be least six inches off the ground. Connect the two, using extra panels if necessary to make a relatively airtight seal between the two boxes.

Experiment with different angles for the solar collector so that you can work out the best position. It's a good idea to get a garden thermometer and put it inside so that you can see the effect of any changes; you should be looking for at least 40 degrees Celsius and preferably a lot more.

Adjustments and Modifications

If you fix the solar collector on a simple adjustable mounting at the bottom, something like a deck chair support, then you can adjust the angle through the year to make the best of the light in the spring and autumn. Keep an eye on the food but it should be dried out in a few days.

In the UK's climate you might need to modify the design to get the air hot enough. Insulating the sides of both boxes will help, as will lining the bottom of the solar collector with metal, although it should still be painted black.

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