Solar Dehydrator

The quest… another way to create and store tasty food! Some food tastes better fresh, canned, frozen or dried. With a young orchard I figured drying at least some of the fruit would be a good idea. Dehydrators are expensive to buy and to run. There had to be a way to make my own.  The challenges I faced were:

1. Quantity – Space:  Drying lots of fruit at one time take space.
2. Expense: I wanted something that did not cost alot to build or to run
3. Speed:  If I could find a way to increase the heat and air movement the fruit would dry faster.

Heat Source

My research took me down several new paths and I learned more about solar dehydration. Solar dehydration works on moisture level and air movement.  The heat source can be the sun, electric light, etc. Lots of solar dehydrators have a long boxed in area painted black to supply the heat source.  Then I found some great solar pop can wall heaters that people were using to heat their shops.  The more I researched, the more I liked the solar pop can wall heater as part of the solar dehydration project.  Why?  Because I can use the work in two places – instead of code reuse I had work reuse!  The heat source solved I now went to airflow.

The solar heat collector can be used with the solar dehydrator in the summer and for heat in the winter.  No, not in my greenhouse, if the sun comes out the greenhouse is warm enough.  My office and the dog are not warm enough in the winter.  But I am going to fast.

Air Flow

Air flow is so interesting!  In a basic dehydrator the heat rises and comes out the top of the dehydrator.  This is the method most people know about.  But, did you know about down draft dehydrators?  I did not.  But they are sooooo kewl!  So let me explain.

A down draft dehydrator works air flow to get the most moisture out of the dehydrator.  The challenge?  It takes more work to set up and needs to be air tight. 

Putting It Together

Let’s look at the mostly finished project and see how the air moves.  They say a picture is worth a million words.  So here is a picture to help explain.

1. The air comes in at the lower part of the solar pop can wall heater.  The air is forced through 5 tall aluminum pop cans calked together to form a tube. 
2. Remember the rule hot air rises?  Well that is what is happening here.  The hot air rises from the solar heater through the pipe into the solar dehydrator.  On a 70 degree day the temperature coming out of the solar pop can wall heater is a balmy 140!
3. Now this is where it gets interesting.  The hot air comes into the top of the dehydrator.  It is still looking for the hottest point to rise to.  But it is trapped now and starts to cool down taking and gathering moisture with it. 
4. It is still warmer than the outside air.  The air needs to get out, more air is coming in.  This is where the 4″ fan comes into play at the base of the chimney pipe.  Air is forced up the pipe.  The pipe is painted black to help start the air flow. The air then comes out of the top of the chimney. 

That is it!

PROJECT PICTURES

The Dehydrator

This is where the work is done!  6′ tall, 2′ wide and 2′ deep.  Why this size?  It worked with the plywood we had on hand.  The plywood is 1/4″ sanded on one side plywood.

We also used 2×2 we ripped from 2×4’s we had on hand.  There is a theme here.  We are working to use the material we have on hand instead of buying new.  

The Door

It is important that the dryer section be air tight.  To help with this each section has been caulked with liquid nails as well as nailed in.  
The hinges are two screen door springs we had one hand.  The goal here is to keep the door closed and air tight.  The plywood we used is pretty light weight.  I am considering reinforcing the door with 1×4’s (painted white).  This would help keep the plywood from warping, the door air tight and would match the rest of the property!  

We have painted everything, the house, shop and shed with the same gray base with white trim.  

Interior

The interior of the dryer can handle different layouts.  I have a 1×4 at the top with hooks for hanging herbs.  Plus there are 11 shelves, again made from material we had on hand.  Each shelf has a regular screen bottom.  

Shelves

The screen is not great for drying fruit.  Acid from the fruit and screen do not mix.  Plus it does not clean very wall. I have a plastic screen I purchased which I lay down before adding fruit.  This way I can wash the screen I actually have food on.  The regular screen is great for drying herbs that do not hang.

Fans

We used old computer fans to help with air flow. We now have three fans (we added a fan this week to help move air). We have a fan at the pop can heater, a fan at the intake and a fan at the base of the tall stove pipe. 

DONE!

Here is the painted solar dehydrator.  The plywood would not last long outside without a good paint job!  I am very proud of our project.   We finished the dehydrator just in time!  We have dried several gallons of cherries and lots of herbs.