An Experiment in Solar Cooking - page 5
A comparison of two cookers that I made
The purpose of this experiment was to compare my foldable cooker with the simple
parabola cooker that I made earlier. If a "stationary", extended time cooker
significantly underperforms the one that requires more frequent adjusting, then
it may not be practical for getting food quickly above the critical range where
bacteria can grow. I consider this as important.
Note: I used the "Improved Alignment" procedure with the parabolic cooker (Under
"Revisions" on page three) before this test. The pictures below show the bright,
focused light on the jar in the parabolic vs. the more diffused lighting of the
central area in the fold-up model.
Test
One quart of tap water in a painted-black glass applesauce jar in each cooker.
Air temp. 89 F, no clouds, light breeze. Simple parabolic cooker aimed at the
sun. Center axis of Fold-up cooker about 20 degrees from the sun at start of
test, to line up with the sun about 1 pm (Used same angle of elevation as other
cooker). I used the same small supports as before, made out of several layers of
glued cardboard, to keep the jars from sliding off..
Test time - 2 Hrs.
11:00 am Water Temp. 86 F (Start)
1:00 pm Final Water Temps. - Simple Parabola cooker 180 F, Fold-up
extended time cooker 175 F
Air temp. was 92 F at end of 2 hr. test. The sun hits its peak somewhere around
1:15 to 1:30 pm.
Summary
The parabolic cooker was adjusted several times during the test. Even though the
fold-up cooker was left in the same position, the difference ended up being only
five degrees between the two units. Both heated one quart of water to about 80 C
(176 F) in two hours. The glass jars had no insulation and a light breeze was
blowing by them. A better system for heating food would be to heat in a
partially insulated container (Like a tightly-covered vessel, sitting inside a
clear glass bowl, that would provide a layer of air insulation). Away from the
equator, sitting the cooker on a board, with something to prop up the other end,
is an easy way to rotate and elevate the cooker as needed
If someone is interested in experimenting with solar cooking, I hope this information is useful.
L.B.