DIY Solar Dehydrator

16
23708
Photo Via Matt Kowal CC By 2.0

One afternoon my wife and daughter were going to see the latest twilight movie and asked if I wanted to go. I politely declined. So after they had left to head to the theater I was getting a little bored so I decided to build a solar dehydrator and drink beer.

I went down to the hardware store and picked up some materials

Image

I cut some 2×4’s down to 2 and 4 foot pieces

Image

and screwed them together to form a framework

Image

I had picked up some 2×2 sheets of aluminum and 2×4 sheets of luan. I test fitted the luan onto my frame

Image

and screwed the aluminum onto the frame

Image

I backed it with the piece of luan

Image

I grabbed my 1 inch wood bit and drilled out vent holes in the top and bottom of the frame

Image

I spray painted the whole thing flat black

Image

I had picked up a 2×4 sheet of lexan. I laid it on top of the frame and pre-drilled mounting holes

Image

and screwed it down to the frame

Image

I set up my thermocouple to check the temp and it was climbing

Image

I let it sit in the sun a little longer to see what I could get the temp to

Image

and was able to get it to 123 after about 15 minutes

Image

I grabbed some more 2×4’s to make the frame for the dehydrating chamber

Image

and stood the panel up into the frame to test the angle

Image

and was able to get the temp up to 136

Image

so I took the lexan panel off

Image

and mounted some netting across the bottom holes to keep bugs out of the chamber

Image

I used some soda cans I had and placed them into the chamber to increase surface area for creating heat

Image

I used the scraps from my whole saw to block up the cans so they didn’t interfere with air flow

Image

and spray painted the whole thing black

Image

I used the netting to hold the cans in place

Image

I trimmed off the excess netting and ran a bead of silicone around the frame

Image

and remounted the lexan, I overtightened the screw in the top right corner and cracked it, awesome

Image

I continued building the frame for the chamber

Image

and screwed down a scrap piece of luan for the base

Image

I did another temp test

Image

and was able to draw 152 degrees

Image

I used a piece of scrap wood to establish spacing for the tray holders

Image

and screwed down a scrap piece of 1x material

Image

and continued screwing them down

Image

Image

Image

and mounted the other side

Image

I used some scrap T&G pine I had to cover the outside

Image

Image

I picked up a vent for the roof

Image

and spray painted it black to help with draft

Image

I started sheathing the other side

Image

and did a quick temp check and I was still over 150

Image

I sheathed the back wall

Image

I made a simple door and z backed it for stability

Image

temp check

Image

I mounted some simple piano hinges

Image

and mounted the door

Image

I used more scrap and set up the roof and traced out for the vent

Image

I cut out the hole and mounted the roof

Image

temp check

Image

I had a scrap piece of ice and water shield

Image

and mounted it on top of the roof

Image

I cut out the hole for the vent

Image

and mounted the vent

Image

I stapled a piece of screen across the opening

Image

I picked up a cheap digital thermometer

Image

I used some 1x material and made some tray frames

Image

and stapled screen material on the trays

Image

I loaded the chamber with the trays

Image

It is all complete, it took me about 6 hours from start to finish

With everything that happened last summer with the loss of my wife’s father and everything else that happened we didn’t get a chance to play with it a lot. A couple of design flaws that I need to fix this year. The bottom is a dead space where the solar panel comes into the chamber, so I want to install insulation to fill the space. Second is airflow through the solar panel, the way the cans are set it restricts the air flow to much and actually overheated the panel and caused the lexan to buckle and shatter.

Image

I think it would have been better served with less cans and leaving a straight shot for airflow. A lot of people will actually just use the solar collector without any cans. Airflow is more important than heat. This project will be continued!

16 COMMENTS

  1. When dehydrating it is all about airflow.

    Yes, for safety reasons (beef) most meats should have at least ten minutes at 160 for bacteria. Most dehydrators will be run at 155 with full airflow.

    So it is about attaining as much temperature as possible and controlling the temp through the use of fans.

    The second most important thing is ventilation, less vents = higher heat. It also means more air movement before finding a way out of the system.

    In NA it should be easy enough to find solar powered fans and hook up a variable speed control for them.

    Imo that is a great solar dry box with a few mods done.

  2. This is a typical example of the same solar box dryer that the Rodale Istitute was recommending 35 years ago. It seems so novel and intuitively correct to all who see it for the first time. Sort of an electric box dehydrator switched to solar collection. Only problem is these never work well in a humid climate, despite full sun. Pushing the same moisture through that meany screens is kind of pointless. You have to keep turning the collector to “track” the sun. And the size of this collector, compared to the square footage of screens, is completely inadequate except in the hottest, driest climates or highest altitudes. Our experiments 30 years ago with this and similar designs led to a revolutionary approach based on radiant drying instead of convection. The results were so much better that we published the results back in 1985 and the design has since been copied worldwide. You can find information about it at http://www.geopathfinder.com/9473 . Think outside the box!

  3. Bob Dahse,

    Thanks for the extraordinary link to the geopathfinder site. I’ve got some double-paned glass recycled from some windows that needed replacing and I’ve been looking to build a solar dehydrator. I’ve done the vertical box and had to mess with moving the trays about to evenly dehydate the food. I’be been kicking around a design kinda like the one in the link but why re-invent the wheel if the first wheel is round?

    About the only change I might make is using Aluminum sheeting that I’ve anodized black instead of using black paint since I can anodize the Al flashing myself.

    Thanks again for the wonderful link!

  4. Would this work in north-eastern Missouri? Our temp ranges from mid 70s to low triple digits from between June and early September. In August, we dropped to the 40s at night….no higher then mid 80s during the day. Full sun, so would it work? I’d love to know so I know whether or not to build one…..thanks!!

    • Yes, we have since modified it like that, I need to update this post with some pictures, another option would be metal dryer vent painted black, some people will just use the metal backing and skip the cans, airflow is important more than high temps