Contributed by Little Colorado River Plateau Resource Conservation and Development Area
A Solar chimney dehydrator can be constructed with any number of designs, adjusted to meet whatever needs you have. Following, is a basic design used at the Crofford Demonstration Farm in Woodruff, AZ. If you would like more information on this design or the farm, please contact the Little Colorado River RC&D
I received these instructions from Little Colorado River RC&D. They are a little confusing so I will add a few comments here and there to help simplify and explain. This is a large dehydrator and some may want to scale it down. As I understand it, it should work on a smaller scale as long as the general demensions are the same.
Materials needed for your solar chimney dehydrator:
2x4's, 2x2's, 1x4's, 1x2's, 3/4 inch plywood, weather stripping, sheet metal, plexiglass, cardboard, black paint, screws & nails, hinges, door latches, screen, and food safe screen. Quantity of materials will be determined on the size of dehydrator you build. This dehydrator cabinet measures 5 1/2 ft. tall by 3 ft. wide.
Important: The collector should be angled between 35 and 45 degrees, facing south.
Adding the walls... There are three walls and one door, the walls are north, south and west, leaving the east as the door. There is also an inside wall that serves as a vent. The North inside wall panel is 4 inches shorter than the outside wall to allow for the vent at the bottom. See diagram below.
In the diagram on the right, the left side is the South side. The collector attaches to that side allowing for the heated air to flow into the food compartment, down through the food then escape upward through the Chimney Vent on the North side, right of the diagram. The Inner North Wall provides this Chimney. Using 2x4's for the basic frame will allow you to place the North Inner Wall gainst the inside of the frame and have a 3 to 4 inch chimney area.
The south wall opens into the solar area of the dehydrator at the top, about 4-6 inches, which brings the air into the cabinet and cirrculates down thru the vent at the bottom of the inside wall and is moved up the chimney and out the vent at the top. Air circulation is of utmost importance, as the moisture must be able to escape the cabinet, and all the product must be exposed to circulation, in order for proper drying.
Adding the runners...
The tray runners are made up of 2x2's measuring 32 inches long, spaced 3 inches apart. Space the runner braces 26 inches apart. Leaving extra space between the right brace and the inside wall, this will allow the air to circulate.
To build the collector, attach 2x4's cut at a 35 or 45 degree angle to the cabinet. Run a 1x4 cut at the same angle down the middle. See diagram. Enclose the bottom of the cabinet and the collector with plywood. The top and sides of the collector are covered with the plexiglass. Leave an opening at the bottom to allow the air to flow in, cover with screen to keep bugs out. Cut a section of cardboard and secure to the back of the 1x4 and underneath to the bottom of the collector. Paint the inside of the collector black.
This is a big dehydrator. The approximate footprint is 3 feet by 7 feet and stands 5.5 feet tall. Make sure that you have your area set up before construction and you may want to assemble in that location as moving it will not be easy.
Finishing the dehydrator...
Cover the roof with plywood, leave a 3-4 inch opening on the north side for the vent, cover with screen. Run weather stripping along the edges for protection. Make sure the door is hinged properly and secureley latched. Remember, you can design your own solar chimney dehydrator, this rough layout is for your reference. Just remember the angle needs to be 35-45 degrees, facing south, and properly ventilated