Somewhere in Time and Kentucky

Somewhere in time and Kentucky,
‘tween furnace fire and frigid flurries,
beats the heart and warms the blood
and finds the brain
bittersweet in joy and pain.

By cast iron stove the scuttle sits,
full of coal and snowy bits
melting, glistening, into drips
that rust the metal bucket’s pit
and reinforced wire upper lip.

Though the scuttle’s galvanized,
acidic anthracite denies
longevity; yet, for today,
keeps my heart alive
and ice and cold at bay.

Quiet rooms; silent home;
floor of wood on cornerstone;
Bible fast by telephone;
I do not feel alone
for I know and I am known.

Kaleidoscopic Solar Oven Temperature vs Time

by Curlydock
Nov. 13, 2007

In my previous post, on September 27, 2007, I went into detail describing the “Kaleidoscopic” type of solar oven that I have been using to bake bread.

image 93

Now I post the time versus temperature for an actual bread baking episode. The episode occurred in Jefferson County, Kentucky, USA, on a day in October, 2007. There had been a recent rain and the cloudless sky was unusually clear and free of haze. Starting at 10:55 AM EST, the bread baked to completion in about an hour. The maximum temperature recorded, between the black lid and top glass bowl, was 320 F (160 C). Just as I removed the bread, I saw the temperature was 325 F and probably still climbing. The ambient temperature was 64 F at the beginning and 70 F at the end.

The results are tabulated and graphed in the next image:

solar_oven_time_temp.jpg

__Time____Ambient______Oven________Note___________

10:55 AM ___ 64 F ___ not recorded ___ start baking

11:05 AM ___ 64 F ___ 240 F (116 C)

11:15 AM ___ 64 F ___ 275 F

11:20 AM ___ 66 F ___ 280 F (138 C)

11:30 AM ___ 68 F ___ 290 F

11:34 AM ___ 68 F ___ 300 F (140 C)

11:44 AM ___ 69 F ___ 308 F

11:56 AM ___ 70 F ___ 320 F (160 C) ___ condensation seen

12:06 AM ___ 70 F ___ 320 F ___ good odor, end baking

The optimum design for this type of oven is a fascinating problem. I wonder if 60 degrees is the best angle for the vertical axis and what the best sizes and proportions are for the reflecting panels. I am pretty sure it would be pointless to have the width of the vertically hinged panels be either more or less than three times the diameter of the oven cavity, for example. But I would like to have some way to test these personal prejudices.

To that end, I have given in to the temptation to do a detailed theoretical analysis. My way of doing this is to write a computer program that uses something like “ray tracing” to simulate the oven, allowing me to more easily see how different configurations affect the solar flux concentration. That program is pretty much finished and I hope to post some of the results in the near future.