Last August, I built a solar food dryer according to the plans in Eban Fodor’s book, The Solar Food Dryer. It’s the blue one in the picture and I’ll refer to that as the SunWorks (SW) design. I wanted to know if I could actually dehydrate food with the sun in humid Virginia. The answer is Yes! In October, I built a second solar dryer according to plans developed by Appalachian State University (ASU). Those plans were in two articles that I found online from Home Power magazine, issues #57 (Feb/March 1997) and #69 (Feb/March 1999). I’m studying how to lessen my dependence on fossil fuel as far as food is concerned, so solar drying is high on my list to explore. I have an Excaliber food dehydrator that I bought used in 1992. In those days, I was deep into canning our extra produce and learning a new method of food preservation did not fit into my schedule. Besides, when in use the Excaliber pumped hot, humid air into the house and it made noise. Of course, canning produced hot, humid air, so at the time, it was the noise that bothered me the most. I might have used it for tomatoes more, but even with nine trays, it only held about 10 lbs. of tomatoes and it took 24 hours for them to dry completely. I was processing lots of tomatoes in my kitchen for our family of 6 and would run 2-4 times that amount through the canner in an afternoon and be done. I used it periodically for making beef jerky.
Times have changed. Now it is usually only two of us at the dinner table and I’m open to some new ideas. I still don’t like noise and I also want to eliminate the hot, humid air of both canning and from the electric dehydrator (not to mention all that fossil fuel). Last summer, I found that the tomatoes in the solar food dryer would be almost dry by the end of the first day. I could leave them in the dryer overnight and they would be finished the second day. That was okay because I didn’t have to listen to a motor or have any disruptions in the house. The only concern was if it would rain the next day. The SW design has an electric option that I built. One day I had tomatoes in it and was gone for the afternoon. That day a storm came up with a brief rain. My tomatoes were fine inside, but I plugged it in that evening to complete the drying, since the next day would be cloudy. I found that I used it so much more because it was just there and the sun was shining. I would look around the garden each day to see what I could put into it. I never did that with the Excaliber.
The SW design has only 60% of the drying area as my Excaliber. Since I’m interested in processing a large quantity of food, I built the larger ASU design which has 1.4 times the drying space of the nine tray Excaliber and about 2.25 times the drying capacity of the SW design. Last fall, I was acutely aware of how fast the sun was sinking each day because I had to keep moving the solar dryer so as not to be shaded by the trees on our property whose shadows kept getting longer. When I finished the second dryer by October 21, I was able to dry two batches of apples before I called it quits for the year. The larger dryer stayed out in the weather all winter and the SW dryer spent the winter in the barn. Now that it is time to use it, it is outside all the time with an old grill cover thrown over it during down times.
When I built the first dryer, deciding on how to build the screens was a big thing. I sized the dryer to the storm window I had. To have one screen on each level required screens that I thought would be unwieldy getting in and out of the house, so my design called for four screens, two on each level. I ordered food safe screening material from the author’s website at http://www.solarfooddryer.com/ and I’m pleased with it. I made one screen frame with some old wood, cut to 1/2″ by 3/4″ and was unhappy with the results. Then I found out how easy it was to make the aluminum frames and made the rest with that. Once I used them my feelings changed. The aluminum frames were HOT to the touch when in use and the wood frame wasn’t. Also, I may be doing something wrong, but I have to keep resetting the plastic spline in places or the screening will pop out of the aluminum frames.
When I made the larger dryer I made nice wooden frames with knot-free wood cut to 3/4″ by 3/4″. The corners are glued lap joints with one screw. These screens are wonderful and actually cheaper than the aluminum ones, but they require more skill to make. They don’t get hot and I can stack them with the food on when carrying them in and out of the house. Having a tablesaw and a terrific husband as my helper is my secret to success.
I added 8″ to the length of the legs on the SW dryer and put old lawn mower wheels on one end. To make it level on the other end, I added aluminum corner strips, which hold the legs 2″ off the ground, protecting them from rot. In spite of having some materials already, such as the window, wheels, sheet metal, screening for vents, and aluminum tape, I spent $162 (before tax) on the SW dryer. If I would have made wood framed screens instead of the aluminum ones, I would have saved $18. Hardware adds up quickly and I spent $7 on the two side carrying handles, which I felt were important to the use of the dryer. Hinges also add to the cost, so if you can scrounge the hardware, you will be well ahead. Including the electric option cost me $23, with the porcelain sockets costing $5.49 each. By the way, the ONLY place I could find those fixtures was at an ACE Harware store. I tried other places and other sockets, and those were the only ones that would do. My goal was getting it built and seeing if it worked, not building it with the least money. I’ll be helping a few friends build their dryers in a couple weeks and my experience will help them save some money and time. They’ve already visited the Habitat Restore and found a good deal on some hardware. This dryer is lightweight and easy to move around.
The ASU dryer cost me $385 (before tax) to build and I bought everything except the wheels, washers, and caulk. I wanted to do a good job on it, since it would be out in the weather and I wanted it to last a long time. I had to buy twice as much glazing as I needed and cut it lengthwise. The price includes only what I used for this project. I’m sure I’ll have use for the rest sometime. This is a large object, so be sure you have a sunny spot that is large enough before building it.
The price per square foot of drying area comes out pretty close to the same for these two dryers, which is about $3 more per square foot over the price of a new nine tray Excaliber that I found online. I noticed that the new Excaliber is listed at 600 watts and my old ED-301 model is 1050 watts. The ad also says that it has 15 sq. ft. of drying area. The 15″x15″ trays in my Excaliber actually only have 14″x14″ of screened drying area, with a 1/2″ plastic frame all around, for a total of 12.25 sq. ft. for the nine trays. My calculations compare the actual screened area on all three dryers.
So, I’m ready to go this summer and I want some company. The more of us who are out there doing this and talking about it, the more we can share what we know and build the momentum of learning. I don’t have lots of experience using the solar dryers yet, but I’ve used them enough to know that they work. Last summer, I dried tomatoes, peppers, peaches, apples, summer squash, snap beans, onions, greens, and made raisins from my grapes. Last week, I dried collards twice. They were easy and were done the same afternoon. There was lots of sun during the week, however the clouds moved in this weekend, after I had put some summer squash in. It served as a reminder that we need to be flexible when we are working with things like this. I’ll use the dryers when I can, but if we have a week of rain and produce is coming out of the garden faster than we can use it, I’ll get out the canner. The biggest adjustment to using the dryers is to get the trays filled as early as possible in the morning, to take advantage of the sun. I encourage you to read Fodor’s book, even if you are going with your own design. It’s full of much valuable background information. You might not have a good place to use a solar dryer yet, or the skills, time or inclination to build one, but you could obtain an electric one to get started learning about dehydrating food. The important thing is to get started. By the way, people have told me they put their electic dehydrators in a spare room so they didn’t have to listen to them. On September 17, I’ll be giving a presentation on Low Energy Food Preservation at the Heritage Harvest Festival at Monticello. Come and hear about my summer with the solar dryers. Sandor Katz of Wild Fermentation fame will also be there.
My next post on June 14 will be about growing grains in your garden, so stay tuned.
Drying with the excalibur now and I have the same complaint. I only have the 5 tray and size and noise are my issues. This solar dryer looks great! Can’t wait to hear more at the Heritage Harvest Festival!
Fascinating to hear your experience! I have only dehydrated with an old Ronco dryer that I picked up from a thrift store. I would love to build one like you have. Looking forward to more of your posts
Sometimes we might think a method or process is not for us, but it is really the tools we are using that are what’s holding us back. That, and those blocks we throw up in our minds. Although the SW dryer holds less that my Excaliber, I used it so much more. You could expand on the capacity by building a second one of that size (as Fodor suggests) or building one with a larger window. The larger it gets, however, the less portable it is, if that’s important to you. Anyway, dehydrating with the sun, rather than electricity, has became a lot more interesting.
Dehydrated okra is one of our mainstays. It is easy to throw some in a soup during the winter. I grow Burmese okra (southern exposure seed exchange) and it is not as “slimy” as other varieties so it dries well. Also, the pods can get large , but still stays tender.
Has anyone tried using a greenhouse to dehydrate veggies?
I’m growing okra for the first time this year because I thought it would be good to put in the dryer. I’ve heard of people hangning their onions and garlic in the greenhouse to dry.
That’s not quite the same thing – you’re really just letting the greens finish dying off. Slice open a “dried” onion and you’ll (thankfully) find it absolutely full of water! 🙂 (Let me know if you meant more than this….but this is typical.)
Dehydrating – which dries a food more or less completely – depends on a good flow of fresh air to remove relative humidity from the area where the dryer is in operation.
I suspect that unless the greenhouse can be open and still retain the level of heat desired, there will be problems after the air has a chance to stagnate inside the greenhouse slightly. The dryer will eventually be “breathing its own air” and the drying effect will slow down or stop working…even though the drying was still flowing air. This potentially invites problems like mold.
With all this in mind, I think it would be worth trying!
-Matt
You are right. For the example I gave of the onions and garlic, it would be more correct to say they were cured there. They would have been put there whole. Although, I’ve heard of people putting cut vegetables in their greenhouse to dry, I wouldn’t do that for the fear of contamination from whatever is in the air with exposure to the soil and non-sanitary surfaces.
Cindy and Matt, thanks for the replies.
Matt, I don’t really care what the name is. BTU, kWh because as you wrote all that counts is the heating power. The peak output power is just part of the puzzle. 120+F air would be a great temp *if* the volume is high enough. I need many gallons air to heat my house. So I need to know temperature plus gallons/h. That would be a good start. Then I need to know the average performance over a whole day. To make this project worthwhile I need a large volume of hot air over an extended period.
Tony
Strange I got a comment in my email from this thread that’s not on the website. I would have replied……strange. Seems several comments are lacking the Reply function now too. WordPress bug or something going on? Thanks from Northern Virginia!!
You’ll notice that a comment on the actual post will have a reply button, as will a comment on that comment. The reply button doesn’t show up on further comments on comments. I suppose that is to keep things from going too far off base from the original post.
That was a really interesting post – thanks. I have Fodor’s book and have ordered some screens from him as well, but haven’t had the time to build one yet. I really want to start dehydrating and have almost bought the Excalibur several times, but I keep holding off because I’d rather have a solar powered one! But, I think you’re right, the important thing is to just start dehydrating… regardless of the method initially. The Excalibur could always serve as a great back up down the road.
I am excited about what you have done already…and ready to do more research myself! I have requested the Fodor book from the library.
I am very short on time, so the idea of loading the dryer on a sunny morning and checking it after my day at work sounds GREAT. My crew would certainly eat dried tomatoes and peppers. BABY STEPS.
Suzanne, glad to have you with us on this adventure. Before I bought Fodor’s book to use to make my dryer, I borrowed it from the library to see if it was going to be useful to me.
There’s more information about using these dryers at https://homeplaceearth.wordpress.com/2011/11/29/solar-food-dryers-update/.
Finishing up the appalachian solar dehydrator now, and I am really excited to get it working! Fruit is starting to come in where we live, and we’re just in time! Luckily, I’m a carpenter, and have salvaged most of the materials free.
We live in sunny colorado, and are excited to see the speed at which we can dry.
Beau, so glad you’ve made a dryer. You’ll find yourself walking around the garden each morning trying to find something to put in it, just because it’s there.
[…] can find more information about my solar dryers at my blog posts Solar Food Dryers and Solar Food Dryers-Update. The Solar Food Dryer, a book by Eben Fodor, was my guide in making […]
what material is the mesh made from?
The screening material is polypropylene. More info at http://solarfooddryer.com/Info/About_SunScreens.htm.
[…] days for something to pick, prepare it at my garden washing station and put the calyx pieces in the solar dryers. After a day or two, when they were dry, I’d bring the trays in and store the dried pieces in a […]
I’m building a downdraft dryer now. The theory is that the cooler, more humid air will sink so it should work better than the Appalachian-style that expects the air to rise through the dryer. I’ll let you know…
Joan, keep us posted on how your solar dryer works for you.
It’s really awesome to see others who are walking the talk! I offer lots of plans on solar food dehydrators and one important piece of feedback I have gotten is from the very health conscious wanting stainless steel screens. If you are interested in where to find stainless steel screen for your solar food dehydrators just shoot me an email. Have you ever thought about selling them? I did notice there are a few industrious individuals who seem to be doing quite well offering their custom solar food dehydrators on eBay. Anyway – very cool and thanks for sharing.
Scott, I haven’t felt the need for stainless steel screens, but others might be interested. I want folks to make their own solar dryers and learn along the way, leaving me free for other projects.
Just a data-point:
I measured how long it took my Excalibur 5-tray to dehydrate a load of seedles grapes into raisins with a KillAWatt meter.
It took me 6.2 killowatt-hours – or about $0.62!
If your power is around $0.10/kw-h like it is here in Virginia, you should see similar results. They were done in about a day to a day and a half depending how big the grape was. I did not slice open the grapes.
FWIW, this thing could be run outside (or in a garage) to ameliorate the noise and humidity issues…and with the low power use – it alternates off/on…throughout its heating cycle – it seems like it should be able to run off of solar pretty easily.
Just some thoughts until I get around setting up my own solar dryer! Thanks for the great article and resource links!
-Matt
Matt, that’s interesting. I don’t know much about solar, but it would be good if it could be powered by the sun. My old 9-tray Excalibur took a hefty 1000 watts. I see from the Excalibur website that the new 9-tray models use 600 watts and the 5-tray uses 440 watts.
The mfgr pretty much always posts than maximum possible power usage.
On the “Fruit” setting, in the drying cycle I posted about, mine cycled “on and off” between 256-watts and 12-watts. The Excalibur is adjustable, so if you were dehydrating at a lower-temperature setting, peak power-usage would be proportionally lower. Next time I have it out ‘ll have to look at what the peak is for the lowest temperature setting.
Unless you’re dehydrating something like meat that requires higher temperatures (and short times) for safety….using a lower-than-usual setting is fine, it just extends the drying time.
If one were trying to power this via PV solar, I think it could be made to work for “most foods” without going to any extremes.
-Matt
Cindy, can you please share something about the performance of the various dryers? Does a certain type work under less optimal conditions like less sun or a non optimal angle of the sun?
Cloudy days certainly slow things down. No doubt about it, you need the sun, unless you utilize the electric option for the SunWorks dryer.The SunWorks dryer seems to get things done a little faster. I have not experimented with different angles, but I’m sure you could try moving it to maximize your efforts. I just put things in and take them out when they are dry. I like the ASU dryer because it holds more and the sun doesn’t shine on the food. Each has its own advantages.
Ok, thanks for your answer. I was thinking about a variation on the ASU type of dryer. Identical but a detachable solar collector that would use to heat my house in the winter months. I’ve seen many builds and tests, but they are mostly done during summer months in the hotter states. I want to use it during the winter months in Indiana. Test results usually are: Works good, gets quite hot etc. While I very much appreciate people even taking the time posting their tests on a blog the only number that’s workable (for me) is BTU/h. Impossible to measure, without equipment, but still a very useful number because it gives a “scientific way” to compare performance of dehydrators, solar ovens, heat collectors and all sorts of earth friendly devices which quite often are compared to (the BTU of) conventional heating like gas and electric stoves.
If you have an article discussing those things, please point me to it.
Thanks for the blog.
Tony, I don’t know of any articles, other than the ones with the directions for the ASU dryer that have done any measurements. You are probably familiar the the Heat Grabber from the Mother Earth News Article from the 1970s. Mother Earth News sells the updated plans through their online bookstore. You could attach a food dryer unit to it in the summer, as long as you could vent the heat away from the house when it is not needed.
It might not be precisely the data you are looking for, but what would be wrong with knowing the peak output temperature of the design instead of BTUs? This would be easy data to obtain! Measuring performance with and without forced air would probably also give useful info.
I understand why you want BTU’s, but trying to “speak in BTU” seems unnecessary and limiting at least in terms of evaluating initial designs. Unless you pick an expensive design to make, you can always scale up from whatever you build first. If you really want to implement an expensive (or hard to make) design, then it could make sense to try harder to measure something like “heating power” in BTU’s….but I’m not sure that even the HVAC mfgrs are actually “measuring” the BTU output of their HVAC’s….I’m pretty sure they are estimating – or calculating – based on power usage by using known conversion factors.
But it’s possible (with a little ingenuity) if you can sufficiently direct the output of your heater that you could make it raise 1 pound of water 1ºC and time how long it takes. That’s the time it takes to “make one BTU”.
-Matt
Can you compare the performance of the Fodor dryer vs the non-direct light solar dryer? I’m trying to decide which one to make. Fodor’s is available as a kit which makes it easy for someone like me who seems short on time…
Make sure to read all my posts of solar food dryers, since each dwells on something different. If you are drying mushrooms, you want the sun shining on them to produce Vitamin D. If you are drying greens, it would be an advantage to not having direct rays. They both work well. The Fodor dryer probably dries just a little faster. If you have more money than time and talent, go for the kit. Even if you are building it from scratch, the Fodor dryer is easier to make and takes up less space.