A few years ago, I woke up to the fact that half of the world's
peoples must burn wood or dried dung in order to cook their food.
It came as quite a shock to me, especially as I learned of the
illnesses caused by breathing smoke day in and day out, and the
environmental impacts of deforestation -not to mention the time
spent by people (mostly women) gathering sticks and dung to cook
their food. And yet, many of these billions of people live near
the equator, where sunshine is abundant and free.
As a University Professor of Physics with a background in
energy usage, I set out to develop a means of cooking food and
sterilizing water using the free energy of the sun. First,
I looked at existing methods.
The parabolic cooker involves a reflective dish that concentrates
sunlight to a point where the food is cooked. This approach
is very dangerous since the sun's energy is focused to a point
which is very hot, but which cannot be seen. (BYU students and
I built one which will set paper on fire in about 3 seconds!)
I learned that an altruistic group had offered reflecting
parabolas to the people living at the Altiplano in Bolivia.
But more than once the parabolas had been stored next to a shed
-- and the passing sun set the sheds on fire! The people did
not want these dangerous, expensive devices, even though the
Altiplano region has been stripped of fuel wood.
The box cooker: Basically an insulated box with a glass or
plastic lid, often with a reflecting lid to reflect sunlight
into the box. 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. (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.