2. The removable lid

Building the base: Two cardboard boxes are needed an inner box that is at least 38cm x 38cm but bigger is better. The outer box should be larger all around but it doesn't matter how much bigger as long as there is about 2cm or so of airspace between the two boxes. We folded the top flaps closed on the outer box and set the inner box on top and traced a line around it onto the top of the outer box, removed the innerbox and cut along this line to form a hole in the top of the outer box. It is upto the user to decide how deep one wants ones oven to be and slit the comers of the inner box with a knife down to that height. We then folded each side down forming extended flaps. Then we glued aluminum foil to the inside of both boxes and also to the inside of the remaining top flaps of the outer box, then glued the top flaps closed on the outer box. We placed wads of crumpled old newspaper into the outer box so that when you set the box down inside the hole in the outer box the flaps on the inner box just touch the top of the outer box. Then we trimmed the excess flap length to be even with the perimeter of the outer box. To make the drip pan we cut a piece of cardboard the same size as the bottom of the interior of the oven and applied foil to both sides and then we painted the whole thing black and then let it dry. This drip pan is put inside the oven and the cooking pots are placed on it when cooking.

Building the removable lid: To build the lid we took a large piece of cardboard and lay it on top of the base. We then traced its outline and then cut and folded down the edges to form a lip of about 8cm. The comer flaps were then folded around and then glued to the side lid flaps. We then oriented the corrugations to go from left to right as you faced the oven so that later the prop may be inserted into the corrugations. We did not glue this lid to the box as we need to remove it to move pots in and out of the oven. To make the reflector flap we drew a rectangle on the top of the lid the same size as the oven opening. Then we cut around the three sides and folded the resulting flap up forming the reflector. The side of the reflector facing the sunlight was also glued with aluminum foil so as to reflect the maximum amount of light and heat into the now emerging solar oven/cooker. To make a prop to hold the reflector flap up we used a old hanger. This was then inserted into the corrugation to hold the flap up. We now had to figure out the glazing material for the top of the oven as recommended by the instructor in class we tried to find a good piece of glass to fit our needs but a glass of specific dimensions would have been quite expensive. To keep the cost down and also keeping the flinctionality of the cooker on priority we decided to use turkey size oven bags with a dimension of about 48cm x 59cm. This made for a double layer of plastic and the two layers tend to separate from each other to form an airspace as the oven cooks. We also glued the bag closed on its open end this was done mainly to stop water vapor from entering the bag and condensing. We were very eager to try out our cooker and which we did and were able to get temperatures close to and sometimes more than 200 degree Fahrenheit. After the presentation in class Umesh and I were thinking about the ways to improve our work and we came up with these ideas.

1. Making pieces of foiled cardboard the same size as the oven sides and placing them inside the wall spaces will help to keep the heat inside the cooker for a longer time.

2. Making a new reflector the entire size of the lid so that we can hamess more solar energy.

3. Making a drip pan of sheet metal such as aluminum and painting it black and elevating it from the bottom of the oven slightly with small cardboard strips, this idea sounded very promising as was put into practice by the other solar oven team in class and they deserve credit for coming up with this idea.

As for the materials the boxes were found after rummaging through the garage and the foil, glue, black paint were purchased from the local stores. The whole project took us about 3 hours to complete and cost us close to 10 dollars.