Instructables

Large Scale Solar Dehydrator

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Picture of Large Scale Solar Dehydrator
Any sort of sustainable food plan that involves a garden and/or fruit trees needs a good dehydrator.  This in conjunction with some canning and some animal protein can get you through any low production season.

Here is a solar dehydrator that uses a solar heat collector and dc powered fans to push hot air through the dehydration chamber.   I built without plans and based the size of the solar collector on how the beer cans would fit in when stacked up.   The fans aren’t needed, but can improve the air flow.  They use so little wattage; they can run off of a small 10-15w solar panel.  Or you can plug them in.
 
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Step 1: Sizing the Solar Collector

Picture of Sizing the Solar Collector
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Gather some aluminum cans of your choice, measure the boards based on the sizing of the cans and the number of rows you'd like.  My box was 117cm x 69cm.   I used a variety of different can sizes. I also used a treated lumber since this will be sitting outside all of the time.   I used 2x4's for the entire construction.

Step 2: Build the Frame

Picture of Build the Frame
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Based on the size of your collector, build the dehydration chamber frame so that the collector can lean up against it as seen in the finished picture and be mounted on the inside of the frame. 

Step 3: Roof Supports and Solar Collector Mounting

Picture of Roof Supports and Solar Collector Mounting
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Cut 2 diagonal beams for the roof mount and make a cut in the 2x4's on the solar collector to allow it to notch into place as seen in the picture.

Step 4: Solar Collector Bottom and Air Vents

Picture of Solar Collector Bottom and Air Vents
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Next you'll need to make a bottom.  I used DensGlas, an outdoor rated gypsum board.  Then you'll need to add your vents. You want air to move freely so don't put vents where there are going to be cans in the way.   If you use fans, you'll want to cut holes based on the shape of fan you use. 

I used "CoolerGuys" dual blower computer cooling fans from Amazon. They're variable speed and built to be used in a hot environment so I thought they would be good for this application.
Mig Welder10 months ago
So, to clarify, the soda-can-fan-array is a source of dry hot air for dehydrating the food?

Correct. In the case of this design the fans would be added to increase airflow and the black cans increase temperature. Technically speaking you don't *need* fans. as the air current would move the air anyway... but sometimes that is not enough flow - as I speculate was the case here.

LOL - not true. The black cans do not increase temperature - there is only so much energy coming in and there is only so much that the temperature that a given flow of air will be heated by, per unit of time.

More anergy = larger gathering area. Higher temperature = slower rate of air flow.

Dezri8 months ago
Simple, effective!
hildymarie10 months ago
I've seen something similar to this only the ends of the cans are cut out and they are connected so that altho the cans are still painted black, the air goes thru the insides of the cans.The air is pulled by convection from the bottom to where the stuff being dried is by the heat of the sun heating the black cans. You must make sure the bottoms of the can/tubes are screened to keep insects out. This way the air is not passing thru any painted surfaces.
actually i made one like that. works pretty well
Taerzik10 months ago
CRP, what about sterling engine powered fans? You should have plenty of heat to run them from the looks of things.
milegrin10 months ago
Would the spray paint of the roofing and cans not taint or "flavour" the hot air as it bakes in the sun?
CostaRicaPrepper (author)  milegrin10 months ago
I don't think so. Not any more than any painted surface in dehydrator. If I see issues I can easily sway out the solar heating media. This was the first prototype. I'll be posting tweaks in the coming months.
Helder4u10 months ago
Some temperature insulation between the corrugated and the bottom board, may result in higher yield.
spark master10 months ago
I see one not so good thing, using pressure treated lumber in the part that heat up then feeds the drying chamber. If it outgasses toxic things you eat them.

Other than that add a light bulb or two to the drying chamber so if it is over cast or after sun down, it keeps going, no fungus will grow that way.

The Mother Earth News has reprints on how to make these, (see there website) here is one of their articles, but they have older ones that are built like yours, (or your is like theirs)

h ttp://w ww.motherea rthnews.com/diy/build-a-solar-food-dehydrator.aspx#axzz2fBoCO9tN

An Amerian university also has a set of plans like yours you must google plans to find it. Measured drawings actually.

Yours is great truly, but add the light bulbs if electricity is available.
You are right,pressure treated,heat and items for consumption is not good,plus non pressure treated dose not cost as much. A good coat of non-toxic paint on the outside,and your good to go,Im gonna use a small ceramic heater for the days that the sun is not doing the job,good catch on that one.
jolshefsky10 months ago
You could have also put the fans on the "cool" side of the solar collector and blown the cool air in rather than pull the hot air out. That way, you could use fans that didn't need to handle high temperatures.

But other than that, awesome design. I have been looking at options for my own dehydrator and this one seems like a winner.
hansenmarj10 months ago
So, you're saying the cans are empty? Would having full cans/bottles hold more heat?
CostaRicaPrepper (author)  hansenmarj10 months ago
Yes they're empty. I figure more surface area to heat the air the better. Plus they resting on a piece on galvanized roofing.
mlipovsky10 months ago
How long does it take on average to dehydrate fruit with your dehydrator? Thanks!
CostaRicaPrepper (author)  mlipovsky10 months ago
I ahven't used it for fruit yet because of the high humidity right now. In one month when dry season comes I'll start doing fruit so there's no hassle with overcast days and what not. But with good sun, it should have no issue drying thinly cut fruit in one day.
jimwi10 months ago
Nice job. I like this.
I had a close look at your finished pics and spotted a small problem. For better air flow cut the top and bottom off the cans and aline cans so air is sucked or pushed up thew the middle of the cans. If you put fans on the air in end, the air coming in will keep fans cooler. Hop this helps good job.
JIM
CostaRicaPrepper (author)  jimwi10 months ago
Your can idea is a good one.
antioch10 months ago
Thanks for this Instructible! Very nice inspiration but the idea of air flowing through and over sprayed aluminium cans to dehydrate herbs seems gross to me. Gonna try and come up with a closed circuit when I start building mine next summer.
CostaRicaPrepper (author)  antioch10 months ago
You can use what ever you want in the solar chamber.
batonas10 months ago
hot air is moving up itself, the fans move air quicker but it's not as hot then, fans makes the process quicker but theres no limit of cans you can use for heating, another idea a long chimney, the higher the more wind, and the more distance the hot air passes the more cold air it sucks in the hearers.
CostaRicaPrepper (author)  batonas10 months ago
Also I added the fans because I thought that the speed of the air from just the heat rising.would not be ideal for dehydration....functional.....but not ideal.
as usual, the real thing proves to be different in reality. but I'm a thinker so I like to think of more efficient and green ways. and by the way what are you planing to dehydrate? sorry I haven't read the instructable the pics just say it all and I know the principles, Im thinking of making some dehydrator for herbs in the future.
CostaRicaPrepper (author)  batonas10 months ago
I built it so big so that i could do a massive ammount of herbs and teas at one time(9 big trays) I grow a lot of herbs like stevia, oregano, basil and tarragon. Also, I grow a tea called "Juanilama" that's magnificent. Veggies, hot peppers and fruits too.

I haven't used it for jerky yet, but if I can get up around 140ish i will. (It's been overcast during rainy season). I'll use it for beef.

.
CostaRicaPrepper (author)  batonas10 months ago
I would 100% agree, if this were a solar oven. However, with dehydrators air movement is key. The more you have going by the food the more efficient dehydration. The temp doesn't need to be anything ridiculous. As long as you can get the temp up to around 130' F.

I also installed the variable speed electric fans as an alternate means to control temp and air speed. I may install chimney later if it looks like air movement could be improved significantly. That's a great idea and thank you for the input.
Davesp10 months ago
Hot idea!
audreyobscura10 months ago
Cool idea!