Solar Oven

I built this solar oven and use it whenever the sun is shining, which is the majority of the time in sunny Johannesburg. In summer it gets up to 110deg C and in winter 80deg C. I use it to bake cereals (millet, corn meal, sorghum), rice, potatoes, beans and sourdough bread. The average cooking time is 4hrs. Food is able to cook from 70deg C and upwards. The lower the cooking temperature, the longer it takes, but the more nutrition the food will have.

Use 22x22mm pine par for the frame. The top frame is 61cmLx45cmW and the bottom frame 50cmWx35cmL. It slopes forward - the back being 31cmH and front 17cmH, to allow more sun in, during the winter months. Masonite board is screwed onto the frame to support it.
 

The inside is lined with tin foil stuck on with white flour and
 water mixture. Cardboard lined with tin foil, is used as additional insulation.
 
Make another box made of 0.4mm galvanised sheeting, to slide into the inside of the outer wooden box.                      
 
Its quite easy to bend the sheeting and then use pop
rivets to hold it together. I painted the bottom half black. I have not found much difference in temperature, whether you paint the sides or not.
 
 
Add a sheet metal plate at the bottom with 10mm spacers. The thicker the plate, the more heat that is generated. The glass cover must overlap the top section of the box, so that no hot air can escape. The glass is stuck on with silicon glue. The reflective lid adds more sunlight.   
I can also use the solar oven as a solar dryer to dry fruit & vegetables. Note how the glass cover is moved back, so that air can can enter the front section and move out the back, to maintain lower temperatures, typically 45-50degC.   
 

Vilikazi and his teammate in the JHB prison training centre, carpentry division, building a solaroven. 

Carpet underfelt or cardboard can be used as insulation.

 

The solar catcher is made of reflective plastic cardboard. The pot fits inside an oven bag. Easy to fold and transport. It can be bought from Richard at alternativeworks@gmail.com
 
These sunstoves are light and effective. They can be bought from Margaret Bennet, Sunstove organisation, tel 0119692818 or sunstove@iafrica.com