|Drying Apricots in Southern California–early 20th century style.|
Dehydration is one of my favorite food preservation techniques. Drying food concentrates flavor and is a traditional technique in our Mediterranean climate. Best of all, drying food is one of the best applications for low-tech solar power. In many places, you can simply set food out under cheesecloth to dry in the sun.
But there’s a catch to sun drying: humidity. Food dries best when temperatures are above 85º F and below 60% humidity. If you live in a desert, humidity isn’t a problem. But in most other places in North America it’s simply too moist to set food out under the sun. It will rot before it dries. In Los Angeles, due to the influence of the ocean, it’s slightly too humid most of the year for sun drying to work well.
But there’s an easy way to overcome humidity: convection, i.e. hot air rises. Most solar dehydrators take advantage of the passive movement of hot air to lower humidity enough to dry food. Here’s a couple of solar dehydrators that harness this simple principle to dry food without electricity:
Appalachian Solar Dehydrator
This is the dehydrator I built with plans from Home Power Magazine. The plans and an improvement on the original plans are split between two articles in Issue #57 and Issue #69. You need to download and read through both articles before building this dehydrator. This dehydrator has performed well for us. The same design can also be modified to work as a rudimentary solar house heater. I had originally used a sheet of plastic over the collector, but have sinced replaced that plastic (which ended up spltting) with a door I was getting rid of.
Cardboard Box Dehydrator
Mother Earth News has plans for a Appalachian style dehydrator made from cardboard boxes. As long as you keep it out of the rain, this dehydrator should work just fine, and is a lot easier to make than the plywood version. I’ve never built one of these, but am interested in hearing from anyone who has.
Eben Fodor Solar Food Dryer
|Photo from Simply Resourceful|
This design is by Eben Fordor, and is described in a book by Fodor called The Solar Food Dryer: How to Make and Use Your Own Low-Cost, High Performance, Sun-Powered Food Dehydrator. I have not seen one of these in person, but the folks at Simply Resourceful built and blogged about their Fodor style dryer. If you’ve got a Fodor dryer, please leave a comment to let us know how it worked.
Solar Tunnel Food Dryer
Beware of Bugs
One drawback to outdoor drying is that you can often get infestations of flies and pantry moths. We’ve lost a lot of dehydrated tomatoes this way even though our Appalachian dryer has screens. I’ve even lost batches I’ve done in an electric dehydrator inside. Thankfully it’s easy to kill larvae by sticking your dried food in the freezer at 0ºF for 48 hours. I’d recommend this step.