How to build your very own solar food dehydrator from scratch

A solar dehydrator is a great piece of low-cost, easy-to-build, and highly effective technology. It can be used for drying anything from fruits and vegetables to herbs and leaves or seeds or anything really very fast and using nothing but sunlight. There are many different designs out there, as you will know if you’ve done a quick search online already: some very simple and small, sporting just a black frame drying chamber with a glass front, others very complex and large.

After doing some research, a number of reasons convinced Charlotte and me to build our dehydrator based on the design by Dennis Scanlin: We wanted a dehydrator that did not directly expose the food to the sun as to minimize nutrient-loss. The very simple dehydrators were thus not an option.

We also looked into dehydrators with solar collectors made from recycled soft drink / beer cans and had already started collecting them at a party, but then decided against it because of the sheer amount of work it is to remove all the lids and bottoms from the cans. Finally, we wanted a dehydrator design that was already planned out for us by someone who had put some thought into it. If you read Dennis Scanlin’s building plan you can tell that he definitely has.

 

 

 

 

 

 

 

 

 

 

Scanlin’s design is good, not only because it produces a fabulous solar dehydrator, but also because it minimizes the amount of materials needed to build. Most of the required wood can be cut from a single plywood (multiplex) sheet. However, his plan is written for an American audience, using feet and inches, and assuming that you have access to an American DIY store. To save you the trouble of translating this excellent plan into something that can be used outside of the US, which is what we had to do, we decided to reproduce a condensed version of Dennis Scanlin’s solar dehydrator building plan in metres and centimetres and that is more flexible with regards to what materials you use.

Necessary Materials

For the body

• One thick (2cm [3/4 inch]) sheet of plywood (multiplex sheet), 244cm x 122cm
• One thin (0.6cm [1/4 inch]) piece of plywood (multiplex sheet), 61cm x 200cm
• 1 wood brace, 57cm x 10cm x 2cm
• 6 wood braces, 57cm x 4cm x 2cm
• 6 wood braces, 57cm x 2cm x 2cm
• 2 wood planks, approx. 180cm x 10cm x 2cm
• 1 sheet of fibre-reinforced plastic, 180 x 61cm
• Heavy duty aluminium foil 200cm x 57cm
• High temperature black spray paint
• Insect screening (around 1 sq. meter)

For the drying chamber

• Screening for the trays (wire netting or something similar), approx. 6 sq. metres.
• At least 20m of thin wood, approx. 1.5cm x 1.5cm

Screws, metal fittings, etc.

• 2 sturdy wheels (wheelbarrow wheels are excellent)
• One 90cm long steel axle (that matches your wheels)
• 100 x 3cm flat head screws
• 30 x 4cm flat head screws
• 20 x 2.5cm round head screws
• 8 x 5cm bolts, nuts, and washers
• 2 strong hinges
• 2 hook and eye fasteners
• Lots of 0.6cm staples

Necessary Tools

• Circular saw (or handsaw, if you have the energy)
• 2 sawhorses or benches
• Electric drill
• Tape measure, protractor, long straightedge, and a framing square
• Marking pencil
• Staple gun
• Wrenches
• Pliers
• Utility knife

 

Step 1 – Collect the Materials

Except for the thick, 2cm plywood sheet, which is absolutely essential for this solar dehydrator construction plan as the majority of parts are cut out from there, you can replace many of the materials in the above list with similar materials that you have ready at hand. Be creative!

Step 2 – Mark out the cuttings

The majority of the wood in Scanlin’s solar dehydrator plan can be cut out from the 2cm thick plywood sheet. Get your measuring and marking equipment ready and mark out the cuttings, as described the graphic, on your plywood. Once you have everything marked out, jack up your plywood sheet on your sawhorses and carefully cut out the individual pieces using a circular saw. Lay the two large sides on top of each other to check whether they are the same shape and trim them to match, if necessary.

 

 

 

 

 

 

 

 

Step 3 – Install the braces

Now it is time to assemble the two sides of your dehydrator using the 12 wooden braces from the materials list: Scanlin’s lead chart is useful to figure out what goes where.  Place the two sides side-by-side and upside down on your sawhorses and begin by installing the 10cm wide brace between the two sides. Pre-drill your holes and fasten the braces in place with the 4cm flat-head screws. Continue with the two 2cm braces at the bottom of the collector box and keep working your way up from there. Obviously you cannot yet install the two 2cm braces that will go into the roof and I would also recommend waiting with the four 4cm braces that will hold the vent covers in place.

 

 

 

 

 

 

 

 

 

 

Step 4 – Collector box bottom

Now it is time to attach the thin, 0.6cm sheet of plywood to the bottom of your collector box: with the two joined sides still lying upside down on your sawhorses put the plywood sheet on top and fasten it with the 3cm flat-head screws around every 30cm all around. Don’t forget to pre-drill your holes! Once your collector box bottom is in place you can saw off any overlapping pieces.

 

Step 5 – Drying chamber front

Get your drying chamber front piece, which you cut out from the plywood sheet earlier (it’s the 58cm x 61cm one, the slightly larger one is the door). Bevel one of the front’s 61cm long sides to allow for a tight fit with the collector box. Then screw the whole thing, beveled side down, onto the front of the drying chamber.

Once the front is in place you can install the two of the remaining 4cm wide braces on the inside of the drying chamber: one right behind the front piece you’ve just installed, but sticking up around 2cm as this will hold the vent door; the other one at same height at the back, so that it will hold the door later on. Cut some of the insect netting to fit the vents and staple it onto the braces from the inside.

Step 6 – Shelf supports and roof

Now it is time to install the shelf supports that will allow you to put trays into your dehydrator. Cut out 22 40.5cm long pieces from the thin 1.5cm x 1.5cm wood and screw them onto the inside of your drying chamber. Make sure to install them with an approximately 2.5cm gap  in between to leave enough space for the trays (plus some stuff on the trays). Again, don’t forget to predrill your holes and use the small screws so they don’t stick out of the side of your dehydrator! You will also notice that the lowermost tray and support will have to be a little shorter because of the brace that is installed there.

For the roof you can use two 30cm x 76cm sized pieces of 2cm thick plywood with a 30 degree bevel on one side each (so they join at the top), which you will hopefully have lying around somewhere (if not you could also glue together scraps from earlier, but only if you’re really desperate). Simply screw the roof onto the dehydrator braces.

Step 7 – Legs and wheels

 

This article was written by Valentin Kunze and has been republished from The Permaculture Collective under creative commons licence.