Build a Solar Food Dehydrator

With a solar food dehydrator, you can use free energy from the sun to preserve your harvest.
By Eben Fodor
August/September 2006
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With increasing interest in healthy eating, sustainable local food supplies and self-reliance, many people are discovering the benefits of a solar food dehydrator.
Photo by Eben Fodor
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More and more people are recognizing the importance of food quality in their daily lives. The freshest, ripest, tastiest and most nutritious food comes from our own gardens or local farmers. But because these high quality fruits and vegetables are seasonal, you have access to them for only a few weeks or months each year.

What do you plan to eat the rest of the year? Will you rely on industrial foods grown by strangers from all over the world and shipped thousands of miles? With increasing interest in healthy eating, sustainable local food supplies and self-reliance, many people are discovering the benefits of a solar food dehydrator.

Solar food drying is more than a curiosity or hobby — it’s an ideal application for solar energy. Solar radiation passes through the clear glass top of a wooden dehydrator box, then the heat trapped by the box dries the food. The dehydrator also may have an absorber plate inside, which indirectly heats your food and creates a convection current of air that enters a vent at the bottom of the dryer (see image gallery). The cool, fresh air that enters the vent heats up, circulates through the dryer, then exits through a vent at the top. As your food dries, moisture is carried away with the hot air. But do solar food dryers work well? Are they practical? Yes, but first let me put this topic in the context of creating a healthy and sustainable food supply.

Eat in Season Year-round

Food preservation is the key to extending the summer’s precious bounty of locally grown produce throughout the year. If you’re like me, you would prefer a method that’s easier and requires less energy than canning.

Freezing is commonly viewed as the most convenient preservation method, but freezers require a constant source of electricity. Your food will be vulnerable to power outages and mechanical failures, and freezer burn will limit the storage life of most foods to about six months.

Drying is an excellent method of food preservation that maintains a high level of flavor and nutrients, while providing a convenient, compact, easy-to-store supply of your favorite produce. Electric food dryers work fine, but I don’t care for the constant noise, heat and odors they add to my house. Electric dryers also take away valuable counter space for weeks on end and can attract ants and other pests. The electricity to run them costs about a dollar a load. The convenience of electricity does not compare to the satisfaction of drying food with free solar energy.

Disenchanted with electric drying, I began experimenting with solar drying. With a background in engineering and solar energy, I soon designed and built my first solar dehydrator. I was delighted to watch the sun quickly dehydrate my organic fruits and veggies. It worked even better than I had hoped, drying large batches of food in one to two days. I dried my entire surplus of garden and orchard produce, leaving nothing to waste. The following year, I grew a larger garden so I could dry even more food.

Got Sun?

If you’re wondering whether solar drying could be right for your location, consider that I live in Eugene, Ore., at a latitude equivalent to Bangor, Maine. We receive lots of rain, but fortunately, we also receive enough sunshine during the summer and fall harvest seasons to successfully dry all our crops with solar energy. If you can get two days of sunshine in a row with some regularity, solar food drying will work for you.

But for those times when the sun is hiding, a backup heating system still can help. I added 200-watt light bulbs as heating elements so I could finish drying my produce any time the weather turned cloudy.

Good Designs

A solar food dehydrator can be made in many designs, ranging from the simple to the complex, and from small to large. For the home gardener, a good solar food dehydrator has these qualities:

  • It dries food quickly — on par with a good electric food dryer.
  • It has venting controls that allow for easy adjustment of drying temperature and airflow.
  • It’s easy to load, unload and clean.
  • It’s easy to set up and put away, with little or no assembly.
  • It’s relatively compact and lightweight for portability.
  • It’s weather-resistant and keeps your food dry in the event of rain.
  • It has sturdy and durable construction for a long life of outdoor operation.
  • It’s pest-proof, and all vent openings are screened.
  • The food trays are made from durable, nonstick and food-safe materials.

Now that you know the basics about solar food dryers, where do you go for designs? Surprisingly, you won’t find much useful information on the Internet. If you search, you will find plans for solar dryers made from cardboard and duct tape. Skip these and stick with the handful of high quality dehydrators that meet my criteria. My book The Solar Food Dryer provides information on some of the better designs and includes complete plans for building the SunWorks dehydrator I designed.

The easiest solar food dryer to build is a “hot box,” a design in which the food is enclosed and protected in a box with a clear covering on top. Screened holes should be in the bottom and sides, so warm, moist air can exit the dryer.

To increase airflow and efficiency, you’ll have to modify the simple hot-box design. Many high-performance designs are based on the strategy of separating the two functions of a solar food dryer: gathering heat and drying the food. The New Mexico dehydrator shown below illustrates this approach.

My design, the SunWorks, integrates the solar collector and food drying cabinet into a compact configuration, which uses both direct heating (like the solar hot-box dryer) and indirect heating from the absorber plate. The airflow is optimized for even drying, and ventilation is achieved by natural convection (see image gallery).

How to Use a Solar Dryer

You don’t need to be a solar whiz to operate a solar dehydrator — just place it in a sunny spot oriented to the south and load it with food. If you will be around during the day, you can speed drying by occasionally repositioning the dryer to track the sun as it moves across the sky. Many foods will dry in one day of sunshine. Wet foods such as tomatoes or pears will require a second day. They should be dry enough after the first day to stay in the dehydrator overnight.

Always start with food that is at its peak freshness and ripeness — simply wash, slice to your desired thickness and place in your solar dryer. I get great results without any blanching or pre-treatments. The dried food consistently looks and tastes great. The flavor is better than anything I find in supermarkets, and it’s free of sulfites (a sulfur-based preservative) and other additives found in commercial dried foods.

Most people think about drying food in August, when they can’t keep up with the supply from their gardens. But there is abundant solar energy in the spring for drying. In May or June, you can start capturing early season crops such as peas, blueberries and strawberries. Then you’ll be ready for your summer and fall bumper crops of beans, plums, peaches, apples and squash.

As you think about how much fun you will have with a solar food dryer, consider that by preserving and storing produce, you can expand your garden and grow more of the things you’d like to enjoy year-round, such as tomatoes. A solar food dehydrator is a great way to maintain a nutritious and tasty supply of high quality, locally grown foods all year long. A good dehydrator will produce outstanding results, along with the satisfaction of saving energy and money by harnessing the power of the sun.


Food Drying Favorites

Fruits: apples, apricots, bananas, blueberries, grapes (seedless), peaches, pears, plums and strawberries.

Vegetables: broccoli, carrots, cauliflower, corn, green beans, onions, peas (sweet, in pod), peppers, potatoes, summer tomatoes, zucchini and other squash.

Mushrooms and herbs are excellent, too!


Eben Fodor is the author of The Solar Food Dryer, a "Book for Wiser Living" from New Society Publishers highly recommended by MOTHER EARTH NEWS. He is an avid organic gardener with a background in solar energy and engineering.


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kashosoft
10/17/2014 9:39:48 AM
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Kermit
5/18/2014 2:59:07 PM
I have been a subscriber for DECADES but became so frustrated because of trouble finding this article I almost canceled my subscription. Latest magazine said there were free plans for the "solar food dehydrator" at www.motherearthnews.com/food-dehydrator-plans. Guess what, it comes back NOT FOUND. Then you want me to sign in so I try to sign in and I have a password that is a few years old. Guess what, "account with this email not found. I DO GET YOUR EMAILS WAY TO OFTEN. I also subscribe (Long time) to Countryside and to Grit but I almost canceled ALL. Sometimes I have a short fuse I guess.

Abhir
12/10/2013 8:11:10 AM
Hello folks, Can any one tell me that is their any disign we have of solar dehydrators by CMOS logic gates through which we can study its working and make it efficient. Its urgent please reply fast.

Vince
8/17/2013 11:29:37 PM
I live in Florida and think most any design would work very well most of the year only in the coldest part of the winter would i need better designs to incorporate the most use of the sun? is this true I have been planning on making one for some time now and have a lot of finished oak boards i would think would work very well? any suggestions tips? thanks for the help

Henry
8/10/2013 5:16:29 AM

http://appropriatetec.appstate.edu/sites/appropriatetec.appstate.edu/files/HPImprovingSolarFoodDryers.pdf

 

 

here is an easy to build solar  dryer


haruka.amora
6/13/2013 11:46:41 PM

haruka.amora
6/13/2013 11:37:20 PM

I was wondering is there a way to adapt your diy solar dehdrator to also funtion as a solar oven? Thanking you Amora


alisarider
5/27/2013 9:42:17 AM

could you send me the plans to build a solar food deydrator too please. Thx


Cleo Castonguay
1/17/2013 10:01:45 PM
It would be nice to see the drawing and the plans...

Larkin Rakes
11/16/2011 5:04:39 PM
here in the Appalachians, we have not have had much ,but economic depressions. my people have always "sun dried' fruits and vegetables. it was very common to see the top of the front porches with apple slices, tomatoes, persimmons, etc. . Stings of beans hanging, called "leather britches". You would never hear anyone "squaling" (whining) about they didn't have the equipment to do it with. I knew several folks that would take a couple of screen doors off and lay them together to keep the bugs off till the food was dry enough. my mother-n-law would put homemade trays, or ones we would get from old refrigerators, in the window of a car (even an old one that didn't run anymore). Just put your little "scrounging" (recycling) caps on. there are several sources all around, like companies that do window replacements. You ought to see all the glass and screens they throw away every day, and most will give it to you for the asking. As mentioned before old refrig. racks, most communities have a repair company that has old frigs. that they just haul away for junk. kissmif, and good luck

Cecil Cooper
7/4/2011 10:40:11 PM
Are the plans available for free or not? It seems to me that if they are you could simply put a download button and if they cost then tell us what the price is.

Cindy Conner
5/31/2011 7:56:30 AM
I have built the solar food dryer from Eban Fodor's book The Solar Food Dryer and I'm able to dry food in humid Virginia. Every community has a library. If that book isn't there, request that they get it for you, and they will. I've written about my experiences so far with solar food dryers, including the slight changes I did, at http://homeplaceearth.wordpress.com/2011/05/31/solar-food-dryers/.

WoundedEgo
9/11/2009 8:08:11 AM
I've been thinking that my slow cooker would make a simple, small dehydrator somehow, since it maintains a steady 125 degrees Fahrenheit temp on the "warm" setting.

Alex_17
8/14/2009 11:47:29 AM
Here are more solar dehydrator plans: http://www.efn.org/~itech/Solar%20tunnel%20dryer/Solar%20tunnel%20food%20dryer%203_2008.html http://www.jrwhipple.com/sr/soldehydrate.html http://www.dehydratorbook.com/solar-dehydrator.html And I know this isn't solar, but it's from Alton Brown, so worth taking a look: http://www.goodeatsfanpage.com/Season11/dried_fruit/witheringbites.htm

ryan _1
7/12/2008 4:04:23 PM
Like so many things nowdays the price has got to be right. This article leads you to believe that there are some plans to build the solar dehydrater , but NOT. The person who wrote this article has used up the dictionary to say what could have been said in 3 sentences. Anyone who reads Mother Earth has the basic knowledge of dehydration , and does not need to read this overworded article. You have got to be kidding about the price of knowledge of solar . You say that the ones on the net are made out of cardboard , well in these times it might just be all we can afford. I will find a solar dehydrater on the net and I will not have to buy your overrated missle to do it.

Stacy_1
7/7/2008 4:10:53 PM
Just doing a simple google search turned up several free plans for solar food dehydrators for those of us that are um, frugal. Here area a couple links that I was able to find: http://www.ag.ndsu.nodak.edu/abeng/plans/6244.pdf http://ecobites.com/self-reliance-diy/diy-solar-food-dehydrator.html Enjoy!

Kerina
7/5/2008 3:25:48 PM
As with the others before me, is it possible to get a design for a solar dehydrator. I am on an incredibly tight budget right now, as alot of us are and am not able to buy the book. So if you cold send me a design, that would be terrific. Thanks much-kerina

Travis_1
7/2/2008 1:25:36 PM
Hello, Wondering how much nutrient loss is due to food exposure to the sun? I guess for years we have dryed our food over standard light bulbs so it shouldn't be any worse. Still, it seems like the "cardboard box" design done with wood and glass would be more efficient and a better design. For one, you could use a larger piece of glass without having to make your drying racks bigger and two, you could use a piece of glass that is already cut but may not be the exact demensions of your rack's/box. Lastly, it would be a pretty easy retrofit of an old lightbulb style box. Just build a box a couple inches deep with glass on the front and some kind of heat sink in the back with vents on top and bottom and line up the top vents with vents in the bottom of your dehydrator. This article may not have had any usefull info in it, but at least it got me thinking... Thanks, travis

brendan
12/16/2007 6:44:48 PM
I'm a peace corps volunteer in el salvador and think my community could really benefit from solar food drying. Can you email me a design?

Jeannine_4
9/9/2007 2:46:47 PM
need diagram on how to construct one. Mother Responds: The ilustrations for the dehydrator are in the Image Gallery at the top right of the article, under "Related." Also, see an earlier comment above regarding the author's web site.

Terry_32
7/11/2007 9:45:27 AM
Please let me know cost of plans and I will remit immediately. I would like to build this solar dryer and demonstrate it to my preparedness group. Thank you Terry Powers   Mother Responds: the illustrations for a solar dryer are in the Image Gallery, to the top right of the article, under "Related." To build this exact dryer, you will need to view the author's book.

RobM_2
4/13/2007 8:31:58 AM
The plans are available on the author's website: http://www.solarfooddryer.com

Karen_49
3/28/2007 7:45:17 AM
I would also like a design for the solar food dehydrator. Will you send me one.

ahmad
3/7/2007 3:39:00 PM
could send me a design thank you

Muhammad_2
3/6/2007 6:47:05 AM
I've got to build a simple dryer for a school project. Could you please send me a design urgently

Matthew_17
3/2/2007 12:32:50 PM
I've got to build a simple dryer for a school project could you please send me a desgin urgently








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