On Oct. 26 I posted a query for technical assistance for Zacharia Olang, a
30-year old student for whom I provide a scholarship at the Kisumu
Polytechnic Institute in Kenya. Zacharia wrote me, "I have started writing
my first project (entrepreneurship project) and the article you sent to me
has become the centre of focus. I'm writing my project basically on solar
box cooker manufacturing which I hope will earn me a credit and perhaps
would lead to self employment. ..."
If you'd like to correspond with Zacharia, his e-mail address is:
olang@kisumupolytechnic.com
Jim Green posted a suggestion to contact Steve Jones of BYU. That was a
great idea! I found an important and practical article by Steve Jones at
www.solarcooking.org, and I'll mail it to Zacharia. Below are excerpts.
SOLAR FUNNEL COOKER
by Steve Jones <stevejones@byu.edu>
Professor of Physics at Brigham Young University (BYU) http://www.solarcooking.org
Introduction:
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. Ergo...
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.
... 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 cardboard 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! ... 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.... 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.
How it Works:
The reflector is shaped like a giant funnel, and lined with aluminum foil.
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.
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. ...
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, either).
I thought that a pressure cooker would be great. But the prices in stores
were way too high for me. Wait, how about a canning jar? These little
beauties are designed to relieve pressure through the lid -- a nice
pressure cooker. And cooking time is cut in half for each 10º C we raise
the temperature (Professor Lee Hansen, private communication). I used one
of my wife's wide-mouth canning jars, spray-painted (flat) black on the
outside, and it worked great. ...
Tests in Utah :
I have personally used the Solar Funnel Cooker to cook
lunches over many weeks. My favorite foods to cook are
potatoes (cut into logs or slices) and carrot slices. Vegetables
cook slowly in their own juices and taste delicious. I also
make rice, melted cheese sandwiches, and even bread in the
Solar Funnel Cooker. I usually put the food out around 11:30
and let it cook until 12:45 or 1 pm, just to be sure that it has
time to cook.
I have also cooked food in the mountains, at an altitude of
around 8,300 feet. If anything, the food cooked faster there -
the sunlight filters through less atmosphere at high altitudes. ...
Students at Brigham Young University have performed numerous tests on the
Solar Funnel Cooker along with other cookers. We have consistently found
much faster cooking using the Solar Funnel Cooker. The efficiency/cost
ratio is higher than any other solar cooking device we have found to date.
Mr. Hullinger also performed studies of transmissivity, reflectivity and
absorptivity of alternate materials which could be used in the Solar Funnel
Cooker. ...
Jane Jackson, Co-Director, Modeling Instruction Program
Box 871504, Dept.of Physics & Astronomy,ASU,Tempe,AZ 85287
480-965-8438/fax:965-7331. http://modeling.la.asu.edu