Using a solar food dryer is kind of like learning to cook over an open fire. You need to develop skills for managing different temperature levels within the dryer, as well as adjusting the overall heat level within the unit. One of the advantages of having the collector frame hinged at the bottom is that it allows you to tilt the top open more or less to control heat at food level. The top of the food dryer always gets hotter than the bottom because warm air rises. This is why you’ll need to monitor the drying progress of food closely until you learn what different seasons and weather conditions do to the performance of your dryer. You’ll want to keep the collector frame closed completely during cooler or cloudier weather, but you’ll also probably want to prop it open a bit with wooden wedges to let excess heat waft off when the sun is bright and temperatures are high. Some people find that it’s even necessary to partially shade the collector frame in low latitudes that get exceptionally powerful sunlight.
Depending on where you live, you might find the clear polycarbonate roofing I recommend works well or not so well. Clear glass or smoked glass might work better where you live. The main thing is that an airspace needs to exist between the layer of glazing and the metal collector plate underneath. This space is crucial for the conversion of solar energy into heat.
Unlike most of the other wooden parts on this solar dryer, the drying frames are made of wood that’s 1” thick, not one and a half inches thick like all the other parts. This creates space above the drying frames for the food you’re drying, and for air underneath the metal collection plate. The easiest way to get one-inch thick material is with something called “5/4 decking stock”. This lumber is used to form the walking surface of some outdoor decks, and the material measures a full 1” thick. Cut strips that are 2 1/4” wide on a table saw, then trim to the correct length for frames that fit between the base side strips of your dryer. Join the frame pieces with two four-inch long deck screws per joint driven into pre-drilled holes. Size your frames so there’s a 1/8” gap on the sides, top and bottom so they don’t get jammed in place. Cut your mesh to size, then fasten it to the top of the drying frames using #8 x 3/4 stainless steel screws and flat washers.
How to Dry Produce
High quality foods, consistently sliced and evenly spread on drying frames. These are the basics behind successful solar food drying. If you’re drying broccoli, cauliflower, celery, carrots, corn, peas or potatoes, plunge these things into boiling water for 3 to 5 minutes after slicing and before drying. This step is called “blanching” and maintains colour and speeds the drying process. Go ahead and experiment with salt or spices added to the water to improve flavour, too. For especially bright dried fruit, soak fresh-cut fruit for 10 minutes in a solution of 1 teaspoon of ascorbic acid powder (it’s just vitamin C) in a gallon of water. This prevents oxidization and a brown colour from setting in on the fruit.
You’ll never be able to tell if your food is dry enough while it’s still warm. That’s why you need to take a sample out of the dryer and let it cool. If it feels dry when cool then it probably is. If your dried produce is thicker than about 3/16-inch, then cut a piece open and check out the middle to make sure it’s moisture free all the way through.
Before packing your dried produce out of sight in jars for long-term storage, let it sit where you can see the jars for a while. There’s always the chance that your food isn’t as dry as you think. Watch for moisture building up on the inside of the jars. If you see any at all, return the food to the dryer for another session on the frames, and make sure that future batches get dried more thoroughly than you think necessary.
Watch the video up next to see how air flows through the dryer and how to control temperature depending on outdoor temperatures and sunlight conditions.
VIDEO – How to Operate Your Food Dryer
Finish up by fastening the collector frame to the base frame with two 1” x 2 1/2” butt hinges and you’re ready to go. You could build the angled support frame shown in the plans to keep the dryer pointed towards the sun, or rig up anything else that makes sense at your place. Aim for an angle of 20° from horizontal for your solar food dryer, then experiment with different angles for best results during different seasons. Before you do, check out “How to Dry Produce” on page TK.
The world around us doesn’t encourage preparation and self reliance. That’s all the more reason to step up to the plate and create systems and plans to take over if our food, energy and social systems stop working. Maybe this will never happen, but it certainly could. It’s about protecting yourself and your family, but it’s also about equipping yourself to preserve wholesome food in a simple, energy-free way no matter what the state of the world is. And who knows? Having a stock of dried food on hand and the ability to dry more without access to power could end up being a lifesaver for friends and neighbours who might not have thought as far ahead as you. Sure, a solar food dryer is only part of this preparation, but it could be a pretty big part. Might as well build one now while hardware stores, lumber yards and ecommerce websites are still things we can count on to get us the supplies we need.
How to Dry Meat
You can dry meat in your food dryer, but you need to do things differently than with fruits and vegetables. The first difference is the need to add insect screens over the top and bottom ventilation openings. Flies may or may not be a problem where you live, but why take a chance? Mount thin strips of wood across the top of the ventilation openings, then tack strips of aluminum window screen over the entire top and bottom ventilation spaces. Aluminum screen here is fine because it doesn’t come in contact with food.
Brining meat before drying is the process of letting it soak in salt water before slicing and spreading on the drying screens, and it’s at least as important as insect protection because it guards against microbe contamination and food-borne dangers. Drying meat like this is essentially involves making jerky, so begin with lean meat in pieces 1” thick. Soak this meat in a brine made with 1 to 1 1/2 lbs. of curing salt (not regular salt) in a gallon of water for 3 or 4 days. Remove the meat, rinse it thoroughly, then slice it 1/4” thick before laying out strips on the drying screens. As with all home food processing skills, you’ll need to fine-tune your methods and recipe to get results that are just right. Little things can make a big difference, so keep track of all variables so you know what works and what doesn’t. Brine recipe, sun conditions, meat type, length of drying time, spices used – all these things matter and are different for every situation. Getting good at drying meat is all about coming up with a system that works.
Final Words
Food is essential for life, but plentiful food available for sale can’t always be taken for granted, as most of us do now. History has seen more than a few situations where bad events turn into hungry people. Prepare now and you’ll be better off than so many who never think about trouble until it’s too late.
