Making Safe Drinking Water for Life!

The PanCooker    pdf[Download a PDF Copy]

During one of my (unsuccessful) attempts to desalinate seawater using solar energy,
I managed to invent a highly effective and simple solar thermal cooker that can be used
for both hazardous water pasteurization and food cooking.  I call it the PanCooker and
it consists of a 12 x 24 inch flexible back reflector,  18 x 24 inch shiny surface mat, and
12-quart clear plastic ice bucket as shown in Figures 1 and 2.  Up to a  4-quart black
enamel stock pot can be used to treat water or cook a meal. A 2-quart black teapot
may also be used for water treatment.

To use the PanCooker,  first lay the surface mat on the ground, lengthwise, facing the
sun. Next, use your hands to shape the back reflector into an open letter 'C' and center
it on the back edge of the mat facing the sun.  Then, place your pot on the center of the
mat,  and cover the pot with the ice bucket. Adjust the covered pot so the base of the
ice bucket touches the back reflector as shown in Figure 1. Monitor the position of the
sun in the sky and move the PanCooker as needed to always face the sun.  The
PanCooker is capable of intense light amplification. A set of sunglasses is highly
recommended when using or being near the PanCooker.  The size of the PanCooker is
only limited by the size of the ice bucket.  As a result, the size of the water/cooking
pot is limited to nothing larger that 7.5 x 7.5 inches ( 4-quarts). When I find a larger
inexpensive alternative, I'll let you know.

Since 1890, pasteurization has been used to kill harmful waterborne bacteria and virus.
To be pasteurized, water must be heated to at least 150° F (65° C)  for one hour  (1). 
The PanCooker is fully capable of  reaching 150° F in two hours but you need up to
one more hour to safely complete the pasteurization process.  Always use a
thermometer,  WAPI or SPADE to measure water temperature and avoid heating
beyond 160° F  (71° C).  Once water temperature reaches 160° F,  you only need
15 seconds to kill all harmful waterborne germs.

Given sunny skies and air temperatures of at least 75° F (24° C),  I found I could
pasteurize a 2-quart teapot in two hours and a 4-quart cooking pot in three hours. 
On very hot days ( 90°+ F, 32+° C)  the heating time is reduced by up to one hour. 
Under ideal conditions, the PanCooker has the capacity to pasteurize up to 12 quarts
of hazardous water per day.  Hence, one PanCooker can meet the water treatment
needs of the average household almost anywhere in the world.  Please note, the
PanCooker does NOT treat chemically contaminated water, seawater or brackish
water.  Also, the  PanCooker is NOT a filter or purification system. The water used
should be reasonably clear and free of obvious particles or have already passed 
some other pre-filter system (2).

The PanCooker works because the back reflector is curved to reflect and focus
sunlight onto the center of the surface mat where we place our water pot. The shiny
surface mat further reflects light onto the pot and onto the back reflector. The black
color of the pot acts like a light magnet absorbing all available light striking its' surface. 
The pots' metal molecules are excited by the photons that make up the light resulting
in heat which is transferred to the water (or food) in the pot. Finally, the clear plastic
ice bucket helps to retain heat by promoting a greenhouse effect and preventing heat
loss due to wind and air temperature.

Steps for Making a PanCooker

Materials (brands in parenthesis)

With the exception of the 12-quart ice bucket which I found at Party City,  all 
tools and materials may be purchased in the USA at most large hardware stores
and supermarkets.  I found everything at Loews hardware and Walmart
Everything you need is shown in Figure 3. The ice bucket is the most
expensive component of the PanCooker and costs $12.  However, the
total material cost is under $17 per unit.

12-quart jumbo ice bucket (Party City)

12 inch roll of self-adhesive HVAC duct insulation (Frost King at Loews)

12 inch roll of heavy duty aluminum foil (Reynolds at Walmart) 

18 inch roll of heavy duty aluminum foil (Reynolds at Walmart)             

18 inch roll of self-adhesive clear plastic contact paper (Con-tact at Walmart)  

Aluminum foil tape (Shurtape at Loews)

Clear packing tape (3M at Loews )


Scissors (for cutting)

Yard stick (for measuring)

Liquid or meat thermometer or SPADE (for measuring water temperature)

Step 1: Make the Surface Mat

The shiny surface mat is a sheet of  'aluminum canvas'.  Aluminum canvas is
a name I coined to describe the product of applying a sheet of self-adhesive contact
paper or overlapping strips of 2-inch duct tape to the 'dull' side of a sheet of aluminum
foil.  After some experience, I found it easier to apply duct tape instead of contact
paper. I like to use aluminum canvas whenever I need  a surface that's shiny plus
water and tear resistant.  You make the aluminum canvas surface mat by first cutting
an 18 x 24 inch strip of aluminum foil. Next,  if you are using contact paper, press an
equal sized sheet of clear self-adhesive contact paper onto the 'dull' side of  the
aluminum foil.  Press the two layers together and smooth out with your hands. Remove
any air bubbles by pricking them with your scissor (or other sharp point) and flattening
with your fingers.  Use clear  packing tape or strips of contact paper to cover any
rough edges and bare spots. Cut away any excess material with your scissors.

The result is a tough, tear resistan, reusable sheet of  aluminum foil that is protected
from wear and water.  You will be placing the contact paper (or taped) side of the
surface mat face down on the ground and the shiny side up. Depending on your situation,
you may want to add another sheet of clear contact paper onto the shiny side of the
foil for extra wear and water protection. However, this may reduce the shine (slightly),
so see how things work with only a single layer of contact paper.

Step 2: Make the Back Reflector
Second, make the back reflector by cutting a 12 x 24 inch strip of self-adhesive
HVAC duct insulation and laying it adhesive side up.  Next, press the 'dull' side of 
the 12-inch roll of heavy-duty aluminum foil onto the adhesive side of the insulation
to form the reflector.  Use aluminum foil tape to cover any rough edges and bare spots.
The result is a tough, lightweight and flexible parabolic solar reflector.  Depending on
your situation, you may want to use aluminum canvas instead of unprotected foil. 
This time, make the aluminum canvas by pressing the contact paper onto the 'shiny'
side of the aluminum foil. 

In Conclusion

There are many of excellent solar cookers you can make or buy on the market today. 
For example, if I did not invent the PanCooker I would recommend the CooKit for
water pasteurization. However, for simplicity of design and low cost, the do-it-yourself
PanCooker is hard to beat. It's a powerful tool that can cook anything you can fit into a
4-quart pot. Any able-bodied adult can make a PanCooker in less than 15 minutes.
Moreover, as shown in Figure 4, the compact design allows eveything to fit inside the
ice bucket including the cooking pot.  Where I live, summer time is huricane season.
Having lived through huricane Katrina in 2005, I know my familly will be better
prepared to survive with our PanCooker. Amen.


Ciochetti, D. A., and Metcalf, R. H., Pasteurization of Naturally Contaminated Water
     with Solar Energy
    Applied and Environmental Microbiology, 47:223-228, 1984.

2.  Burch, J. D., and Thomas, K. E., Water Disinfection for Developing Countries and Potential
     for Solar Thermal Pasteurization,
     Solar Energy Vol. 64, Nos 1–3, pp. 87–97, 1998

Figure 1
Figure 1. PanCooker  - a solar thermal cooking and water pasteurization

Figure 2
Figure 2. PanCooker components - from left to right: 12-quart clear plastic
ice bucket, 12 x 24 inch flexible back reflector, 18 x 24 inch shiny surface
mat,  4-quart black enamel stock pot, and 2-quart black teapot. Optional
2-liter filled water bottle to brace the back reflector (from wind).

Figure 3
Figure 3. Tools and materials used to make a PanCooker. From left to
right: yard stick, scissors,  meat thermometer, 12-quart jumbo ice bucket,
self-adhesive HVAC duct insulation, 12 inch and 18 inch rolls of heavy duty aluminum foil, 18 inch roll of self-adhesive clear plastic contact paper,
aluminum foil tape and clear packing tape.


Figure 1
Figure 4. PanCooker storage - everything fits inside the ice bucket including
the water/cooking pot.



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