The BYU Solar Cooker/Cooler | Page 2

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. (I'll tell you exactly how to do this later on.)
The Solar Funnel Cooker is safe and low cost, easy to make, yet very
effective in capturing the sun's energy for cooking and pasteurizing
water -- Eureka!
Later, I did extensive tests with students (including reflectivity tests)
and found that aluminized Mylar was good too, but relatively
expensive and rather hard to come by in large sheets. Besides,
cardboard is found throughout the world and is inexpensive, and
aluminum foil is also easy to come by. And individuals can make their
own solar cookers easily, or start a cottage-industry to manufacture
them for others.
Prototypes of the Solar Funnel Cooker were tested in Bolivia, and

outperformed an expensive solar box cooker and a "Solar Cookit"--
while costing much less. Brigham Young University submitted a patent
application, mainly to insure that no company would prevent wide
distribution of the Solar Funnel Cooker. BYU makes no profit from the
invention. (I later learned that a few people had had a similar idea, but
with methods differing from those developed and shown here.) So now
I'm trying to get the word out so that the invention can be used to
capture the free energy of the sun - for camping and for emergencies,
yes, but also for every day cooking where electricity is not available
and even fuel wood is getting scarce.

II. How it Works
The reflector is shaped like a giant funnel, and lined with aluminum
foil. (Easy to follow instructions will be given soon.) This funnel is
rather like the parabolic cooker, except that the sunlight is concentrated
along a line (not a point) at the bottom of the funnel. You can put your
hand up the bottom of the funnel and feel the sun's heat, but it will not
burn you.
Next, we paint a jar black on the outside, to collect heat, and place this
at the bottom of the funnel. Or one can use a black pot, with a lid. The
black vessel gets hot, fast. But not quite hot enough to cook with... We
need some way to build up the heat without letting the air cool it. So, I
put a cheap plastic bag around the jar--voila, the solar funnel cooker
was born! The plastic bag, available in grocery stores as a "poultry bag",
replaces the cumbersome and expensive box and glass lid of the solar
box ovens. You can use the plastic bags used in American stores to put
groceries in, as long as they let a lot of sunlight pass. (Dark-colored
bags will not do.)
I recently tested a bag used for fruits and vegetables, nearly transparent
and available free at American grocery stores, that works great. This is
stamped "HDPE" for high-density polyethylene on the bag (ordinary
polyethylene melts too easily). A block of wood is placed under the jar
to help hold the heat in. (Any insulator, such as a hot pad or rope or

even sticks, will also work.)
A friend of mine who is also a Physics Professor did not believe I could
actually boil water with the thing. So I showed him that with this new
"solar funnel cooker," I was able to boil water in Utah in the middle of
winter! I laid the funnel on its side since it was winter and pointed a
large funnel towards the sun to the south. I also had to suspend the
black cooking vessel--rather than placing it on a wooden block. This
allows the weaker sun rays to strike the entire surface of the vessel.
Of course, the Solar Funnel works much better outside of winter days
(when the UV index is 7 or greater). Most other solar cookers will not
cook in the winter in northern areas (or south of about 35 degrees,