SUNNY COOKER

INTRODUCTION:

 

The price of corrugated cardboard, which is widely used for the 

making of low cost solar cookers, has been rising at an annual

rate of 15-20% in recent years.  The price rise is due to the

costlier energy, labor, chemical products and recovered paper,

which are used for making corrugated cardboard.  

 

The cardboard price increase may not have an impact on those

solar cookers made from used cardboard boxes, but it would

impact those made from newly purchased cardboard material.

 

Cardboard price increase is inevitable, but we could alleviate the

cost impact per solar cooker if we are able to reduce the amount

of construction material needed in making each solar cooker.

 

In early 2008, I set a goal to create a functional solar cooker,

from a flat sheet of cardboard, by using 25% less material than

that required for a ‘CooKit’ solar cooker.  The end result, after

about eight month's time, is the ‘Sunny Cooker’.

 

The ‘Sunny Cooker’, made from a 36" x 36" sheet of cardboard, 

has multiple triangular shape reflector panels to help focus 

sunlight towards a cooking pot.  'Sunny Cooker' is designed in

such a way that its contour can be easily re-shaped, simply by

tilting the cooker forward or backward.  Altering the contour

of the cooker would enable the cooker to become more efficient

in capturing the sunlight at different sun angles. 

            Sunny Cooker in normal low-sun-angle setting 
            (For cooking when: 35^o < sun angle < 50^o)

Sunny Cooker in mid-sun-angle setting & tilted backward
              (For cooking when: 45^o < sun angle < 60^o)

Sunny Cooker in high-sun-angle setting & tilted backward
                (For cooking when: sun angle > 50^o)

MATERIAL and CONSTRUCTION STEPS:

To construct a ‘Sunny Cooker’, this will require a square sheet

of corrugated cardboard measuring 36”x36”, aluminum foil and

glue.  

 

The following are the construction steps for the ‘Sunny Cooker’: 

1. Glue the aluminum foil on one side of the square cardboard.
2. Draw cooker’s outlines and fold lines on the aluminum side
   of the cardboard.  Make sure that the cardboard corrugations
   or flutes run vertically from the top to the bottom.
3. Cut away all unwanted parts.
4. Crease and fold along the fold lines.
5. Cut open the four slots, and widen them to about the same
   dimension as the thickness of the cardboard.
   

Please click on the link below if you need a .cdr format copy of the
'Sunny Cooker' plan.  I used the Corel Draw to create the plan.
http://webzoom.freewebs.com/sunnycooker/Sunny Cooker Plan.cdr

 COOKER ASSEMBLY and SETTINGS:

For a new cooker, crush the corrugations or flutes within the

two locking tabs first before using it.  This will make it easier

to bend and insert the locking tabs through the slots.

 

When the sun’s angle is below 50^o, assemble the cooker by

inserting the two locking tabs through the two upper slots. 

 

When the sun’s angle is above 50^o, assemble the cooker by

inserting the two locking tabs through the two lower slots. 

 

 

 

The vertical section of the cooker's panels can be tilted backward, 

and kept in the desired position, by wedging a small stone under

the lower edge of  the two vertical panels on the side.  Backward

tilting of the cooker will allow for better focusing of the sunlight

towards the cooking pot when the sun moves to a higher altitude.

 

 

SETTINGS and COOKING:

 

To cook, put food in a black metal pot (3 to 4 liters size), and cover

the pot with a clear glass lid.  Enclose the pot inside a clear oven

bag, if available, and place the cooking pot on top of the cooker’s

base.  Set the cooker according to the instructions in the two

previous paragraphs, and face the cooker directly towards the Sun

to start cooking.  Adjust the cooker, from time to time, to ensure

that the sunlight stays focused on the cooking pot.

 

Tilt the cooker forward, as shown in the above illustration, should

there be a need to start cooking even when the sun is still low, less

than 35^o.  It would also help if the cooking pot is raised higher by

an inch or two, with a support, to better capture the low sunlight.

 

   Sunny Cooker and 4L size pot with a clear glass lid
     (4L size pot achieved 156 degree C temperature)

 

STORAGE and TRANSPORTATION:

 

The ‘Sunny Cooker’ can be fully folded by first releasing the two

locking tabs from their slots, and following the folding steps shown

in the illustrations below.  A fully folded ‘Sunny Cooker’ measures

about 21”x18”x3”. 

 

 

 

Some of the joints, between panels, may remain ‘flat’ when a

folded cooker is taken out of storage and re-assembled for use. 

To correct this, it is necessary to refold the cooker, along its

existing fold lines, and adjust the panels until you get an even

cooker curvature.

 

I hope that the introduction of the 'Sunny Cooker' design will

be able to help bring about meaningful savings due to a reduction

in the amount of construction material required.

 

Teong H Tan

23 August 2008