|Boiling Point No. 01 - January 1982 (ITDG Boiling Point, 1982)|
The Tungku Lowon stove was designed by Desa Desa, an Indonesian AT organisation which is based in central Java. The stove was developed from the high mass Lorena stoves originally introduced in this area. These stoves were fairly rapidly found to be unsuitable for local cooking practices and the broken up stoves were remade several times, each time getting smaller. The present Tungku Lowon is similar in many ways to traditional stoves and is thus able to satisfy the same requirements of the villagers as the traditional stove. ITDG was requested by Dian Desa to evaluate the stove under laboratory conditions.
Testing the Tungku Lowon in Reading began in July 1981 appropriately with the new stove being given a new user. I was pleased to find that there were no problems with starting the stove, even from cold, using our standard wood, Jelutong. First in line was a series of tests to find out how repeatable the results were. This proved to be good, particularly when the tests involved boiling both pots rather than just one. Shorter tests are more prone to inaccuracy of measurements and starting a fire is the time when outside factors matter most.
unnumbered = standard
1. 3 sticks
2. Small diameter
5. Central flue blocked
6. Airholes blocked
8. 25% moisture
9. 48% moisture
10. Forced airflow
11. 63% moisture
Our calculations i of percentage heat utilised (PHU - defined in our Interim Report No.1, 1980) showed that in standard tests, 18 - 22% of the energy available was used in heating or evaporating water. This was an encouraging start as it agreed with the Indonesian test results. Time to boil 2 kg of water- in the first pot varied between ,12 and 19 minutes. Time to boil 2 kg of water in each of two pots varied between 21 and 25 minutes. Much of the variation in time to boil was due to the heat output from the stove which varied between 17 and 29 g wood burnt per minute (approximately 5 - 8 kW). These times are comparable with other relatively efficient low- powered stoves. The weight of wood used during the tests varied considerably - between 290 and 390 g to boil the first pot; 400 - 460 g to boil both pots.
Having completed the standard tests, we carried out a series of tests to find the effects of using wet wood and of partly blocking up some of the air and flue gas passages. On a good stove, minor variations from standard operating conditions shouldn't make much difference to the performance, so we reduced the central flue size by one third and blocked the airholes completely. PHU was reduced from 22% to 16% for blocked flues and from 22% to 19% for blocked air holes. One of the big problems with these changes in the configuration of the stove was that it produced lots of smoke and made the boiling times very long - up to 41 minutes for pot 1 with wood with a 63% moisture content.
Because of the slit at the front of this stove, smoke tended to escape through the front. We combatted this by slightly raising the back by 3 - 4 cm which reduced smoke without changing the PHU.
The overall conclusion was that we were testing a basically good stove. Modifications might be made to improve "user friendliness" but that it would be difficult to improve the efficiency without creating a new and different stove. Also I liked it!