| Boiling Point No. 10 - August 1986 |
Papers Nos. 7, 10, 12 by F.J. Mkwawa and H.H. Schneiders
Tanzania National Scientific Research Council, Dodowa Rural Energy Project
The Project has produced severe' interesting papers about its work on cooking stoves, Nos. 7, 10 and 12 deal especially with charcoal burning community stoves. Paper 10 describes a masonry stove which was built in 1984 and although initially popular with the users at the College of Education and reported to give 30% fuel saving (see test results in Paper No. 7), some components very soon needed replacing. A further 6 were built to an improved design in December 1984 and now are used for all the cooking for the college. These are much stronger and take pots up to 50 cm diameter which sit right into the stove. (See Figures 1 and 2). The stoves have a masonry body with a combustion chamber made from a lorry wheel rim and a steel or cast iron grate and a sheet steel ash tray and door to control air intake and burning rate. At the college, 4 of these stoves were served by one chimney, but this is only needed when lighting up.
Tests were carried out to compare the time taken to boil 20 litres of water by measuring how many pots of water could be boiled by one initial charge of 10 Kg of charcoal. The results show a payback period of 2 years assuming a cost of Shl0,000 per stove and no maintenance costs. This depends heavily on the quality of the masonry work which was often very poor in Dodoma, with failures within a few months. The grate temperatures in such large charcoal stoves can be very high, perhaps over 1000°C and firebricks are essential for reasonable life.
It seems clear that further development work is needed on the stove design and construction and that training will be needed for the local builders. Although the stoves must be built in situ, the metal parts could be made in a central workshop and sold as a kit, perhaps involving the services of a skilled stove builder for a day or two.
There is a need for larger aluminium (or stainless steel) pots of 200 or 250 litres capacity for larger institutions of 500-1000 people, The needs of the institution, in terms of numbers and times of meals, quantities of tea and hot water etc. must be carefully studies before the stove(s) specification can be prepared.
Paper . No.12, December 1985 describes the work with portable, steel, community stoves burning charcoal. These are double-walled, uninsulated stoves, supplied without a chimney and built in a metal workshop. The stove is a development of the Dodoma domestic metal stove ( figure 3)...The outer body is galvanised and the combustion chamber is again a lorry rim with a cast iron grate. The aluminium pots may be 30 or SO litres, with 2 handles and sit right into the stove.
The stoves take 3 person days to make with direct costs of Sh5000/and a selling price. estimated at about 10,000/-. Assuming 30% fuel saving, a pay back time of 10-12 months is claimed for 7 day use in a hotel. Four stoves have been tested and subsequently bought by hotels. Cooler kitchens, convenience, cleanliness and speed of cooking were important considerations.
The project believes that there is a place for both types of community stoves, although the portable, steel stove being a complete-unit at an inclusive price, is easier to promote and may be more efficient for-the smaller sizes - up to 50 litres. The portable stove is not made with a chimney -and it is recognised that some form of smoke removal is essential when lighting up if the stove is used indoors.
The project has made a detailed study of one hotel kitchen and prepared 3 schemes for reorganising it by replacing the nine stoves with 4 or more improved stoves. The capital outlay would be high because, of the~ cost of several large aluminium pots, but it could be repaid in 7 months in the last case and the non-monetary benefits such as the cooler kitchen might be even more important. They calculate that such a hotel kitchen conversion would save 6 hectares of woodland from being cut down each year (assuming 100 m³ wood removed per hectare). We have not heard whether this scheme is being implemented.