This solar cooker has been designed by Suresh Vaidyarajan - an architect, who has found a simple solution for a tough problem. This design can be made from items that people no longer need (rubbish) making it potentially free. There are no tools needed to create this cooker. It will be cooking for you in no time!
Take an old car tube. If the tube is punctured get it patched. Inflate the tube and keep it on a wooden board.
Get your black pot or pan (if its not black you can make it vlack in a fire). Put all the ingredients for cooking Khichdi - rice, daal, salt, water etc. in the cooking pot.
Place the cooking vessel inside the tube. Cover the tube with a piece of plain glass. Within three hours the Khichdi will get cooked.
What happens? The place in the center of the tube is like a closed cavity. Air neither goes out or comes in. The rays of the sun enter the glass and get trapped. Slowly, the temperature of the cooking vessel rises and the Khichdi gets cooked.