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The solar dryer

marcoMarco has come to Koanga from Tauranga with his wife and six-month-old baby, to do a three-month appropriate technology apprenticeship. The solar drier is just one of many projects he has thrown himself into….

As part of our Appropriate Technology course we made a solar drier to harness the sun’s energy for   drying and preserving some of our excess fruit and vegetables so we can eat them throughout the year.
The basic design is a radiant heat solar drier. It is a really easy design, but works really effectively.
Basically there is a layer of glass that is propped up on a timber frame, and two layers of corrugate iron.  The sun shines through the clear glass at the top of the drier which then hits the black painted corrugate iron that heats up the metal.
drid tomsThe heat from the underside of the metal then heats the food below in a stainless mesh tray, causing  it to lose moisture and dry.  The moisture leaving the food flows out under the screen and up the sloped air channels. The cool air comes through the corrugate troughs and draws the hot air and moisture out leaving behind tasty dried food.
You can dry all sorts of fruit and vegetables. Depending on the size of the fruit and amount of sun, the drying process can happen in a day or two.  It would be advised to put the produce in on a sunny day and to cut it quite thinly.  As you can see in the photo above, we have wild blackberries, alma tomatoes (which are specific for drying), elderberries and peaches.
solar groupWe have made a large solar drier to suit the community, but you could build a much smaller one for home use out of pallets, for example.

Here is our design draft:
Solar drier sketch

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