Re: LETS ADOPT A Bigger UNIVERSAL POT

["Dean Still" <dstill@epud.net>]

Dear Ron,

 

Don O'Neal who is in charge of the HELPS, International molded cement griddle stove project in Guatemala writes:

"I agree with standardizing on pot size and shape in order to compare data.
I would encourage however a larger pot containing at least one and a half
gallons of water.  My point is that it be sufficiently large to average out
short term variation in wood and fire tending.  Also it is about the size of
actual cooking pots in the field."

 

I have just finished a series of tests at Aprovecho. We use 5 pounds of water because using less water biases the test toward the lowest mass, quickest responding stove which may in fact be burning wood quickly. In the 12 tests just done although we found a range of boiling times to be between 12 and 19 minutes the efficiencies after burning 1.5 pounds of wood were closely packed, 22% to 26%. Some of the slower responding stoves burned slower and closed the gap as the pot was simmering. Don suggests that we use 1.5 gallons of water. I believe as well that a larger amount of water is better and it allows the higher mass stove material to get hot and become more efficient. A longer test is more like boiling, beans, corn for tortillas, etc.

 

Tom, I agree with you that the test should reflect how people cook. In Don's experience people in Central America use big pots and larger amounts of water. One litre seems more suited to backpackers, etc. But really any reasonable test would be better than the confusion that now exists. Apples and oranges...Tower of babble...

 

By the way, here is our test procedure:

 

Procedure: Weigh water and wood (5 lbs. of water (2265g), and 1.5 lbs. wood (680 grams). Kiln dried Douglas Fir is cut into pieces 18" X 5/8" X 1/2" except for one 18" piece which is split finer to provide kindling for starting fire. Prepare fire and place uncovered steel pot (9 inch diameter by 5 inches high) on stove. Place all 8 probes while stove is at room temperature. Begin recording. One minute after recording has begun, light fire. Once fire is going, feed sticks into fire five at a time, burning at the tips and pushed into fire as consumed. Continue recording until 7620 seconds after test is initiated. Make note on file of: date; test number and description (for example: 3rd Pico test, 2nd using adobe brick); weight of wood used; weight of water used; time from lighting fire until boiling; water remaining at end of test; time when last wood was fed into firebox, and weight of charcoal produced. Also note any inconsistencies in procedure.

We assign a pound of wood 8,600 BTU's. And figure that it takes 1005 BTU's to boil off a pound of water. The amount of BTU's that made it into the pot (sensible plus latent) over the amount of BTU's in the wood gives us a percentage. We don't count BTU's that heated the pot or made remaining ash, coals, etc.

But, I'm not looking for us to agree on every part of the test protocol, although that would be really great. Just agreeing on the pot size and weight of water will be a major advance. Hopefully folks publish their test protocols and we can make adjustments.

Hope we can make this happen! Onward to good science!

Best,

Dean