Testing Cookstoves (pdf)
Dean Still, Damon Ogle, Rob Bailis, Aprovecho Research Center December 1, 2003
Presented to ETHOS 2004
In June of 2003, approximately twenty people met at the Aprovecho Research Center near Eugene, Oregon to compare various wood burning cooking stoves used in either Central America or Africa. The stoves were examined using a Water Boiling Test. This test has been used at Aprovecho for many years. Energy in the fire heats water up to boiling and by measuring the sensible (by rise in water temperature) and latent heat (by amount of steam generated) the thermal efficiency of the stove is determined. The amount of heat entering the pot, divided by the total amount of heat released from the burning wood, results in a percentage. Higher percentages indicate a stove that has improved thermal efficiency. This test is frequently called Percent Heat Utilized (PHU).
After comparing the performance of many stoves side by side, doubts about the approach forced a re-examination of the literature on testing. In the Aprovecho water boiling tests,
stoves that burned at high power exclusively, using up fuel quickly, scored higher than other stoves that boiled food as quickly but then simmered the water at slightly less than
full boil for much longer time periods. The same amount of wood was used in all tests and it seemed reasonable to expect that the stove that kept food at near boiling temperatures for the longest time would be the most fuel efficient when cooking food. The PHU test did not seem to be predictive of success at cooking food.
After the seminar, Dr. Alan Berick took the results from nine stoves and looked at how long the stove was able to keep the pot