How to Build the Plywood Telkes Cooker - Capturing heat: Five earth-friendly cooking technologies and how to build them

Begin by constructing the box first. In this case we used one-half inch thick plywood. Cut out all of the pieces shown in the diagram. Bevel the edges that meet the glass at 30 degrees. Cut the door into the back or sides of the box. Each joint is glued and nailed together.



The glass cover fits over the plywood and is supported by the insulation as well, which completely covers all interior wooden surfaces. You can nail or glue rigid foam insulation to the walls or build up the one inch thick insulation out of alternating layers of cardboard and aluminum foil. If you choose the cardboard option, contact cement works better than white glue. It resists moisture better. Big washers, with nails or screws, are helpful to hold the cardboard to the walls. Remember that the front and back insulation needs to be beveled. Surround the cardboard insulation with aluminum foil, shiny side facing in towards the food. Make this "package" as tightly and strongly wrapped as possible to keep moisture out of the cardboard. Paint the whole interior black with water based flat paint. Leave the cooker in the sun for a couple of days to burn off the gases from the paint before using the cooker.

The reflector wings, which in this case are made out of 1/2" plywood, need to be supported by some type of brace. We make the braces out of wood. The reflectors meet the glass at an angle of 120 degrees. Hinges hold the reflectors together. It's possible to make the hinges from leather or old bicycle tubing.

The interior of the reflector needs to be covered with something very shiny like aluminum foil or mylar. Contact cement works well.

The box works better covered with two panes of glass. One pane works too. Glue the glass to the insulation and plywood, using a sealant, preferably silicone. The silicone can also be used as a spacer between the two sheets of glass. Leave a small air hole so that the heated air can escape and not build up pressure between the panes of glass.

Remember that the black pot (hopefully, low mass) should sit on a black cookie sheet or painted piece of metal. Make sure that the door fits tightly, try to minimize air leaks! The oven can't get hot with a lot of air infiltration.

Following these criteria will result in a solar cooker that should hover around 300 degrees F. even when full of food. On hot days, beans will cook quickly, bread will bake and brown, chicken will get crispy and french fries will disappear in foaming oil as they fry. The results will impress you!





Cut the door out of the back panel.
Remember to bevel the front and back panels at 30 degrees.
The back and front are nailed onto the
bottom                                     The sides are nailed onto the bottom, back,
andfront.


The glass is glued to the top of the box
using silicone sealant. If two panes of glass          Wooden reflector supports that meet the
are used, another bead of silicone forms a         glass at an angle of 120 degrees are screwed
gasket between the two.                                    or nailed to the box.




Diagram A: A comparison of varying reflector angles for solar cookers, showing the amount of admitted sunlight and the advantages of a 30 degree angle.