Light enters through the top glass (or plastic),
to slowly heat up the box. Problems: energy enters only through
the top, while heat is escaping through all the other sides,
which have a tendency to draw heat away from the food. When the
box is opened to put food in or take it out, some of the heat
escapes and is lost. Also, effective box cookers tend to be
more complicated to build than the funnel cooker.
While studying this problem, I thought again and again of the
great need for a safe, inexpensive yet effective solar cooker.
It finally came to me at Christmastime a few years ago, a sort
of hybrid between the parabola and a box cooker. It looks like
a large, deep funnel, and incorporates what I believe are the
best features of the parabolic cooker and the box cooker.
The first reflector was made at my home out of aluminum foil glued
onto cardboard, then this was curved to form a reflective funnel.
My children and I figured out a way to make a large card-board
funnel easily.
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