| Boiling Point No. 17 - December 1988 |
by Ian Grant, ITDG
The "stove problem solutions" quoted above from the ITDG "Practitioner's Manual" will help field workers to follow a planned procedure for fixing a faulty stove. However, they may still need to check to know whether they have been completely successful or whether the stove still needs treatment to bring it to its full potential. Its performance can be compared with other stoves of the same kind, tested at the same time, with standard figures for the stove, or with the results of tests carried out on the stove before "fixing". This can be done by using the simple Boiling Water Test procedure set out in the Practitioner's Manual (pa 2()-21) as follows:
"The first stage in a test programme is to carry out Water Boiling Tests. At least three different procedures have been developed, each with its advantages and disadvantages. A joint programme between Eindoven University and ITDG has indicated that at least two of these procedures give comparable results. The first procedure described can be used to make a quick assessment of a stove, without the need for any laboratory equipment.
Water Boiling Tests can be carried out in a laboratory or a field station, by scientists or field workers, at the initial assessment and development stage. They can be used for assessment of stove designs and optimization of stoves. Most frequently they are used for comparisons between stoves, or between a stove and an open fire. They can also be used to help determine the effect of deterioration or poor installation of a stove in household situations. In some cases, where cooking tests or kitchen field tests cannot be undertaken. Water Boiling Tests can be used to give a rough approximation of relative fuel savings.
Procedure 1 - Quick assessment, with minimum equipment
Use of the Test: To make a quick assessment of the difference in performance between two stoves.
This test requires minimal equipment - a watch, a bottle to measure equal volumes of water, and, if no scales are available, a simple pivot balance can be constructed to make measurements of equal quantities of wood (see Fig 1).
· The procedure is not complicated and no special preparation of fuel is needed.
· The results provide a quick indication of the relative performance between stoves.
· The results provide a clear indication if modifications to a stove significantly change its performance.
· The procedure allows one set of tests to be compared with tests done under similar conditions.
· The procedure enables designers to determine whether the performance of the stove is affected by the type, size and moisture content of the fuel, by the size and type of pots, weather conditions, etc.
· The test does not indicate the range of power output of the stove, or how easily the output could be controlled.
· The test does not indicate the performance as a function of cooking time; the warm-up time is the least efficient period, and in this type of lengthy test is considerably reduced as a proportion of the whole.
· In particular, the test does not adequately account for heat which does not actually boil the water.
· The test does not provide data for optimization.
1. Prepare the Fuel
Take approximately 2kg of wood and divide it into two equal portions, by weight.
2. Prepare the Pots
Take at least 8 pots (4 for each stove), of the same size and weight, and fill to three quarters full with water (from the same supply - ie. same temperature).
3. Light the Fire and Bring the Pots to Boil Sequentially
Light the fire, place one of the pots over the fire, and when it comes to the boil replace it with a second pot. Note the time when the pot came to the boil. NOTE - If the stove has a second pothole, start with a pot on both potholes and when each comes to boil replace it with a new pot of water. Repeat this until all the wood is used up.
4. End of Test
At the end of the test note down the number of pots of water that each stove has brought to the boil. Calculate the time each pot took to come to the boil.
5 Repeat The Test
Each stove should be tested at least 4 times".