Dusted off my original Solar Cooker from 2011 and tried to get cooking towards the end of the summer. Whereas 5 years ago I had very little luck in getting anything cooked, had much more success this year.
Improvements made as follows.
Added a door to the rear of the Box Cooker. This meant that I did not have to lift the glass every time I checked on the food. Lifting the glass meant a loss of heat as hot air rises. Using the door at the rear of the cooker meant that the hot air remained trapped at the top under the glass.
Refined the reflectors. The original design had 3 aluminium panels roughly bent to reflect additional light into the box. This has been changed to 4 plywood panels lined with aluminium foil and held at 120 degrees to the glass using metal brackets. The side reflectors are quickly added to the Box Cooker using butterfly nuts.
Lining the inside with tin foil. The previous design had black card on the inside. This was not effective as although the black attracted the heat the card was useless in holding it. The tin foil reflects the incoming radiation around the inside of the box until it hits a black metal object.
Using a black metal plate on the base. A 2 mm thick aluminium plate was used at the base of the cooker. This absorbed and maintained the heat from the sun.
Use of a roasting bag. Given the disadvantages of a British summer, the belt and braces approach of a roasting bag meant that there was yet another layer of air insulation between the black cooking pot and the outside.
Addition of corner pieces. To ensure maximum reflection of the suns radiation into the Box Cooker the corners between the main reflectors was filled in with tin foil wrapped cardboard panels and held in place with bulldog clips.
With the resulting cooker design we managed to successfully cook rice, lentils and also bake bread rolls.
The finished cooker is shown below.
Click on the link below for details of how to build your own solar cooker to the design given here.