Build your own DIY solar dehydrator

Tracy Chandler
Saturday, 1st May 2010

No one likes to waste gluts of summer fruits, so why not dry some using a simple, solar-powered dehydrator?

The principle of the solar dehydrator is very simple: a box at the bottom heats up the air which then rises and flows through the second box.

We bought some wood (having nothing suitable lying around) and some black paint, and a friend donated a sheet of perspex. Two boxes of similar size were then made.

Making the Heat Box

Holes were drilled in opposite ends of the first box, the inside of which was painted black (to absorb more heat) and the perspex was attached on top – although anything clear would do for the job, from glass to thin plastic, as long as it is attached well.

Making the Drying Box

Holes were drilled in one end of the second box, with runners put around the inside to rest trays on, and a removable lid made to allow air to pass through.

Joining the Two Boxes

The two boxes are joined with the heat box angled and the drying box flat, with a airflow conduit between them to ensure airflow goes where it is meant to.

The great thing about this design is that it works on fairly dull days – and if it's showery, a cover over the drying box should stop the contents getting wet. (It probably won't work well if it's overcast and humid as the water from the fruit will have nowhere to go and so may go mouldy.)

This design can be made to what ever dimension you require. My one is about 45cm2 (18in2) and has enough room for two tier drying trays.

And best of all it only cost £15 to make, although if you have some materials handy it could cost less or nothing. 

Heikki |
March 26, 2011 - 2:28pm

Most solar dehydrators are uncovered. Most green herbs are destroyed in sunlight. Many other dried food looses valuable staff or volatile molecules while in open sunlight. The end product tastes almost like pure cellulose. An exception of this is when drying mushrooms, they tolerate sunlight rather well.
Therefore it is essential that there is a lid above the boxes. It also is inconvenient to have a stress when a quick shower comes and it is raining already next to the house but I am in another part of the city. Therefore a lid or a roof is utmost necessary. Naturally the roof must be some 5...10cm higher then the uppermost box.
One important detail is that some times the wind is quite strong. If the small tower is not sturdy enough, then one have to collect the dried herbs again from the lawn this time.
Personally I have built several of these solar dehydrators from standard size tomato or cucumber boxes. One may use the 5cm or the 10 cm standard depending on what is the food stuff to be dried.

In drying process the speed of the air is most essential. If there is not enough sunlight to create air flow, one might dry same leaves for a week or two.

To maximize the effect of the solar dehydrator, it should have some 4...6 layers. The fresh leaves will be put on the uppermost box and the lowest will be emptied first. So up it goes in and below it goes into the kitchen. Of course same sort of herbs so that the mint leaves do not give their odour to some parsley or vice versa.
If the harvest is rich and one wishes to dry more, then an electric dryer indoors makes the best result for the end process. I have seen some so-called dry leaves, which most certainly were almost dry, but not enough. The composting effect soon takes place and destroys the product.
I have used this method with success in the winter time too. When there is a special offer at the market just before closing time, one might find some treasures worth buying a larger quantity. Then the dryer makes it easier to prepare dried fruit. These I enjoy in making wonderful soups.
It saves my money too and it comes from this planet.
Happy harvesting

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