Solar Food Drying

Tips for FAST Solar Food Drying!

Fast drying is key to good food quality and to maximizing your productivity as a food preserver. Most of the work in food drying goes into the food prep: washing and slicing. The rest is easy. You can dry some foods in one day and a full load of even the wettest foods in just two days of sunshine with a good solar dryer.

Fast drying requires three things: heat, air movement, and proper food prep. Here are my tips to fast solar drying:

Maximize solar heat input to your dryer.

Start your solar drying in the morning on a day with a good sunny forecast. If you have a large, wet load of tomatoes or fruit, you need a sunny day on the first day of drying to get most of the moisture out and start the preservation process.

Clean the glass of solar glazing with a wet cloth before each drying session to remove any dust. Dust on the glazing can easily reduce your solar energy input by 10% to 20%.

Get maximum solar rays by adjusting your dryer to face the sun. I usually adjust it three times: for morning sun, midday sun, and evening sun.

Optimize air flow.

Airflow is necessary to remove moisture and replace moist air with dry warm air. Solar dryers rely on natural convection instead of mechanical fans to move the air. Warm air rises, so controlling the top vent on the dryer regulates air flow.

Adjust the venting on your dryer to allow maximum airflow, while also maintaining adequate drying temperatures. Drying temperature is up to you, but I like to dry at 120 to 140 degrees F because food dries faster at higher temperatures.

Proper food prep.

Proper food prep will greatly speed drying. Slice all food to a uniform thickness so that each piece will dry at about the same rate. Generally, I try to keep all foods to a thickness of 1/4 inch maximum.

Cut through fruit and vegetable skins so that the flesh is exposed. Skins can greatly impede drying.

Load food so that there is a little space around each piece of food to facilitate air movement. Overloading the dryer will slow drying and will not save time.

This is all you need to get consistently great results.

If you have a load that requires a second day of drying, and the weather gets partly cloudy on the second day, you will still get good results, even if you need to take an extra day, since your food already has most of the moisture removed and the preservation process has started. However, if your weather turns overcast or rainy, make use of the backup electric heating (if available) to finish off the sun's work.

Happy solar drying!
Eben Fodor

More information on solar food drying can be found under these links:

SunWorks Home Page