The Funnel solar cooker, originally introduced by Professor Steven E.
Jones, is very efficient in capturing sunlight with its 60 degree conical
reflecting surface. However, the Funnel solar cooker has an unstable
shape that makes it difficult to keep the cooker and the pot in position.
In addition, it is also not possible to fit a regular size cooking pot into a
regular size Funnel cooker because of limited space at the lower end
of the cooker. In order to retain the very efficient conical reflecting
surface, but eliminate the above mentioned disadvantages, I came up
with a hybrid Fun-Panel solar cooker.
The Fun-Panel solar cooker incorporates features from the Panel
cooker into the Funnel cooker. The Fun-Panel cooker can also be
placed in two different positions to better capture sunlight at different
The construction materials required to make a Fun-Panel cooker are
simple and low cost. I made my Fun-Panel cooker from a used
cardboard box that measures about 50cm on all edges. One cube-
shaped cardboard box has enough cardboard material for making
two Fun-Panel cookers. Other construction materials required are
one short string, paper tape, aluminum foil and glue. If you use
cardboard box with different dimension, all you need to do is to factor
the dimensions given in this instruction to suite your box's dimension.
To construct, cut the cube-shaped cardboard box to obtain two large
rectangular panels and one small panel as shown in Figure 1 below.
The 'Fun-Panel' plan was originally created using the Corel Draw
software. Click the link below for a .cdr (Corel Draw) copy of the plan.
Each large rectangular panel is made up of one square face of the box
together with one cover flap. Next glue aluminum foil onto one side of
the two large rectangular cardboard panels. Draw all the fold lines and
cut lines, according to Figure 1 above, onto the rectangular cardboard
panels. Next cut along the cut line and then fold along the fold lines.
Join the two large rectangular cardboard panels together, according to
Figure 2 below, to form the cooker.
Next glue the small cardboard panel to the lower edge of the square
panel, located in the middle of the cooker, according to Figure 3 below.
After the glue has dried, bring the lower edge of this square panel
forward by a distance equals to 2/5 the length of the square panelís
edge (this ratio is critical as it defines the final shape of the cooker).
Punch two holes through both the small cardboard panel and the
adjacent rectangular panel, and tie them together with a short cord in
order to keep them in position. The construction of the Fun-Panel
cooker is now completed.
SETTING and COOKING:
For low Sunís altitude cooking, between 35 and 50 degrees, place the
cooker down, with the rectangular panel on the floor, as shown in Figure
4 below. For very low Sunís altitude cooking, below 35 degrees, raised
the pot by 2 to 3 inches above the base to better capture the sunlight.
With rising sun angle, between 50 and 70 degrees, flip the cooker
around such that the square panel, in the middle of the cooker, is now
horizontal, and place the cooker on top of a small box (a box with 5-
6 inches in height is now required). See Figure 5 below.
The small box serves to support both the cooker and the cooking pot
in this high sunís altitude setting. For very high sunís altitude cooking,
above 70 degrees, loosen the short string that holds the small cardboard
panel to the rectangular panel. Tilt the vertical, rectangular panels slightly
backward until the pot receives maximum reflected sunlight. Tie the two
ends of the string together to hold the rectangular panel in that position.
To cook, put foods inside a black metal pot, and cover it with a clear
glass lid. Enclose the pot in a clear heat-resistant plastic bag. Set the
cooker according to the Sunís altitude, and face it towards the Sun.
Place the cooking pot in the cooker and start cooking.
The Fun-Panel cooker is also capable of cooking, without the clear
plastic bag enclosure, if you have good sunshine. A test done in
Singapore, without the use of a greenhouse enclosure, have recorded
a maximum empty pot temperature of 130 degrees C. The 4-liter size
pot used has a clear glass lid. The cooker was set to the high-sun
angle setting, and the Sun's angle was at 55 degrees when the
temperature was taken.
Fun-Panel cooker can be folded flat by first untying the string and then
folding the middle square panel upward so that the cooker can be
drawn together for ease of storage. I hope that you will find the Fun-
Panel cooker to be an interesting and user-friendly solar cooker.
6 January 2008
I have received several success stories from people who have built and
used the Fun-Panel cooker. Their positive feedbacks have prompted me
to take a closer look at the cooker design for further enhancement.
Several modifications have been identified for incorporation, individually
or together, into the original Fun-Panel design.
The first modification is to add a few more folds and cuts to the three flat
panels, located in the middle section of the cooker. This modification will
further enhance the efficiency of the cooker reflectors. See diagram below
for the additional folds and cuts required.
Picture of the modified Fun-Panel reflectors
The second modification is an alternate method of tying the center panel
to the base panel in order to eliminate the requirement for the small
cardboard piece in the original design. See diagram below for more details.
The third modification is to add an adjustable reflector-support, made from
cardboard and rubber bands. The adjustable reflector-support eliminates the
need to tie the center panel to the base panel, and provides the cooker with
the freedom to tilt at various angles to better capture the sunlight. The center
panel becomes the permanent base for the pot with this change added.
The photos and diagram below show the adjustable reflector-support
supporting the cooker at various tilt angle positions.
Cooker at low tilt angle Cooker at high tilt angle
1 July 2008