(introduction...)

IT Intermediate Technology

Acknowledgements

Technical Editors:	Stephen Joseph
	Yvonne Shanahan
Artwork:	Jenny Trussell
Production:	Sandra Conn
Contributors:	Siddhartha Bhatt
	Stephen Connors
	Michael Drohan
	Stephen Joseph
	Brian MacGarry
	G M Mhango & N S Cooper
	Weclaw Micuta
	Ralph Royer
	Yvonne Shanahan
	Bill Stewart

(Readers wishing to enter into correspondence with any of the authors may obtain full postal addresses from the Stoves Project address given opposite)

ISSN 0263-3167

'Boiling Point' is the newsletter of the Intermediate Technology Development Group Stoves Project. Contributions are welcome in the form of articles of not more than 700 words with line drawings, simple graphs, etc. where appropriate. Copy date for the next issue is 1st June 1983.

All correspondence should be addressed to: 'Boiling Point', ITDG Stoves Project, Applied Research Section, Shinfield Rood, Reading, UK, RG2 9BE.

Opinions expressed in contributory articles are those of the authors and not necessarily those of the ITDG Stoves Project.

Editorial

The ITDG Stoves team has been writing up results of evaluation studies which its members have carried out in Sri Lanka, Indonesia, and Kenya. We have-been trying to synthesise this information together with that from other-evaluation studies carried out in Senegal, Mali, Niger and Gambia, to determine the impact of present stove programmes, and the constraints they face.

It would seem, from the information available, that it is difficult to determine with any certainty what fuelwood savings are being achieved (although it appears that in some projects there are net savings).

The performance of a mud stove decreases as it ages, as cracks appear and pieces of the internal walls flake off. It is evident that people will abandon their new stove when it ages to the point at which it uses more wood and takes longer to cook than the old stove. Lining the inner walls of mud stoves with a pottery insert significantly increases the lifetime and also increases the performance of a stove (over that lifetime).

It is also found that chimney stoves do not necessarily lead to increase in performance (although they have the benefit of removing smoke from the kitchen). A great deal of careful design work is required to avoid blockage of the flues leading to the chimney. The chimney must be easy to cIean and there must be a considerable effort expended to train users how to clean the stove (or else train the stove builder, or some other person to establish a stove cleaning enterprise).

One of the main attributes that have motivated many users to adopt or make frequent use of a new stove appears to be a decrease in cooking time. Women value the extra time for either extra household chores or extra agricultural work. Hates of adoption appear to be greater in areas where people spend a considerable proportion of their income on fuel purchase; this especially applies in urban areas where charcoal is the main fuel.

It has been noted in most programmes that many of the new stoves do not fulfil all the functions of the existing open or shielded fireplaces. In particular, most stoves that have been introduced to date are not portable. In Africa people often cook outside. Enclosed stoves do not provide light, and often not enough heat to warm people during the cold season. Massive mud stoves often take longer and use more wood than an open fire to boil water just for tea.

This only represents some of the findings of these evaluation studies. Over the next year we hope to be able to detail the reasons why people do or do not adopt a stove, and what the potential impact of stove programmes could be.

Nepal - The CFDP / RECAST Stove Programme

In September Stephen Joseph was commissioned by FAC to assist the National Nepal Stove Programme, which was initiated in February 1981.

Two pottery stoves have been designed and laboratory tested. They are an insert stove and a double walled stove (see Figure 1 ); both have 2 pot-seats and a chimney. 700 stoves have been placed in households in the Kathmandu valley. initial indications are that the stoves are more fuel efficient than the existing models, and are acceptable to most users.

* Community Forestry Development Project (FAO), Kathmandu / Research Centre for Science and Technology, Tribhuvan University, Kathmandu, Nepal.

FIGURE

Problems had been encountered with the cleaning of the chimney and installation of the insert stove. TO overcome these, members of the RECAST team, Mr Bajracharya (a local stove consultant), and Stephen Joseph redesigned the bottom section of the chimney, and modified the insert stove (see Fig 2).

Following this visit Stephen has redesigned the single pot chimney stove and test work is now being undertaken. We hope to report on the results in the next issue of Boiling Point.

BP No. 3: New Nepali Chulo

Mr Chiplonkar, the Section Manager for the Indo-German Dhauladhar Project has asked us to point out that the article title was misleading. The stove being promoted is known as the DHAULADHAR CHULA which has developed from the New Nepali Chula. It should be noted that the plan and elevation on page 3, BP No 3, are of the Dhauladhar, and not the New Nepali, Chula.

Gambia National Stoves Project

In October 1982, The Gambia launched the first National Stoves Project to be implemented in the CILSS* region of West Africa. Funding was agreed between the Gambian government and the UN Sundano-Sahelian Office (UNSO) for a three year National Project. The Department of Community Development is responsible for implementation of the Stove Project, whose main objectives are to introduce 6, 000 improved stoves into the rural areas, and 1, 000 into the urban areas of the Gambia.

Traditionally, the open-fire is used for cooking in the rural areas, while in the urban areas metal charcoal burning stoves were used until the sale of charcoal was banned in 1980. The ban was imposed in an attempt to reduce firewood consumption but despite this an energy consumption survey in 1981/2 found that 20% of its urban sample still used charcoal for cooking and ironing. This finding, coupled with the inefficient burning of wood by a population accustomed to charcoal, has probably diminished the expected net energy savings in fuelwood.

Following the ban, in 1980 the Forestry Department embarked on the introduction of improved wood-burning stoves to the urban population. Their overall objective was to convince urban women that there was a clean and economical alternative to charcoal.

The Forestry Department was assisted by a Peace Corps volunteer working with the Rural Vocational Training Project (RVTP) at Mansakonko. He built the first new stove, which was a modified 'Lorena' with two pot-holes and a chimney. Since the objective was to introduce new stoves to the urban community, a series of training courses were organised for artisan masons, who would be competent to construct and repair stoves on a cash basis. During 1981, over 100 mud stoves with chimneys were introduced into urban areas and more than 40 people were trained in their construction. In the rural areas, the RVTP team built a total of over 400 mud stoves and over 100 people were trained.

* Permanent Inter-State Committee for Drought Control in the Sahel, PO Box 7049, Ouagadougou, Upper Volta.

FIGURE

In November 1981, CILSS funded a National Wood-Saving Stoves Workshop, held at Mansakonko. This was the first event to embrace everyone involved or interested in the introduction of improved stoves to the Gambia. During the workshop seven prototype mud stoves, from all over the Sahel region, were constructed in a demonstration area, and then installed in several compounds of a nearby village.

With the launch of the National Stoves Project, the Department of Community Development has embarked on a programme of testing and modifying the prototypes to improve their performance, lifetime and acceptance by users. In addition, improved prototypes of metal stoves are to be developed for use in urban areas with ground-nut shell briquettes as a charcoal substitute.

Since the start of the National Project, the ITDG Stoves Project has been attempting to assist the Gambia and has carried out two consultancy visits to help set up the programme for testing and modification of stoves which will suit the rural and urban situations.

New Stoves in Senegal

Recently Yvonne Shanahan visited Dakar for a few days and took the opportunity to visit the CERER* Stove Project and the Dakar Industrial Trade Fair.

The CERER Project, funded by USAID, began in March 1980 in response to a request from the Senegalese government. The project objective was to introduce half a million wood saving stoves into the rural and urban areas of Senegal over a period of 3-5 years. According to the Project Director, Mr Lamine Diop, approximately 5000 have been built during the pilot phase of the project (1980-82). CERER are now awaiting refunding to continue with the larger scale dissemination. The majority of the stoves are a one pot chimneyless design known as the 'Louga' or 'Koumba Gaye' stove. They are concentrated in the Louga region of NW Senegal where there is said to De a perceived shortage of wood and single pot cookins/meals predominate. The basic design was formulated during an APROVECHO mission to the Project in 1980/1.

Village women were actively involved in the design process. Subsequently the stove has been disseminated by training women to build their own stove. After a two year period of introduction, the average lifetime of this stove is claimed to be 14 months. According to follow, up, many of the original stoves are being rebuilt by their owners when they begin to crack and break down.

In the other areas, CERER has trained several teams of masons in the construction techniques for 2 pot chimney mud stoves. A series of 14 day workshops have been organised by CERER and collaborating institutions in urban and rural areas. During these workshops, people are trained as stove constructors by the skilled masons. The majority of the trainees are unemployed and unskilled young men, and after the workshop they are expected to sell their stove making skills in their villages. The fee charged varies as the costs of labour and materials are not fixed. None of the stoves built after a workshop training are subsidized by CERER, but several of the stoves built during a workshop are installed free of charge in a number of compounds.

In a few areas (eg Flores in the north) associations have been formed by women to save towards the cost of a stove, each woman contributing weekly. The money is used to buy materials and pay for the stove-builder's labour.

CERER has encountered problems with the introduction of mud stoves into the urban areas, where the majority of women want a portable stove. This is still seen to be a considerable advantage of the traditional three stones and the metal charcoal stove. Consequently CERER has begun research in the improvement of the traditional metal stove, initially by lining the firebox with a mud mix which fits around the sides of the cooking pot.

FIGURE

The objective is to reduce heat loss around the sides of the pot and through the metal wall. During the visit to CERER the initial test results were not available, but the French volunteer in charge of the technical work claimed that the modified metal stove made a 35% saving over the existing metal charcoal stoves. A similar claim (30%-35%) was made for all the mud stove prototypes on display at CERER. The laboratory results are said to be substantiated by field results.

Amongst the many stands at the Dakar Industrial Trade Fair Yvonne found the USAID Senegal stand showing all the CERER stove prototypes, mud and metal, presented in a very neat display. Peace Corps regional co-ordinators were responsible for the stands, and they said that there had been a good deal of interest shown in the stoves. Most of the questions had come from men and were about cost and how to obtain one. The northern co-ordinator for stoves had spent the past two years working with the CERER Stove programme, the southern co-ordinator had just started. They were both very enthusiastic about the future for new stoves in Senegal, although the southern co-ordinator spoke of the complexity of problems involved in trying to introduce chimney mud stoves into a region with reasonable wood supplies. To quote one recent observer to the stove programme, 'After the training, the chimney stoves are sufficiently complicated, the masonry skills sufficiently daunting, the lack of tools sufficiently discouraging, and the failure to attract customers for 2-3000 CFA combines to convince the new trainee to drop the whole topic'.

CERER Chimney Mud Stove

Another interesting stand, in the exhibition area for the Niayes region, was a display for a Turf Exploitation and Environmental Rehabilitation scheme. It is estimated that there are 55 million cubic metres of turf deposits in the Niayes region. Part of the display included chimney mud stoves and modified metal stoves from CERER, and the display literature proposed that the turf briquettes could be used with the CERER stoves to save trees.

Stove Seminar in Bamako

Between the 1st and 8th December 1982 Yvonne Shanahan attended the second CILSS regional stoves seminar which was held in Bamako, Mali. The seminar was jointly funded by CILSS and the UNFISTD, and organised in co-operation with the Malian government.

The aims of the seminar-covered:

1. A review of national and regional stove activities with special reference to technical aspects of stove building and testing

2. A search for

- new approaches and strategies for the organisation and training of stove builders
- mechanisms to establish better communications between researchers, technicians, and stove users.

All of the CILSS member countries, and CILSS stove programme staff were in attendance, with the exception of Cap Verde Islands, which has no stove programme. Organisations participating at the seminar included ITDG (UK), the Eindhoven Woodburning Stove Group, Bois de Feu (France), AIDR (Belgium), GTZ (Germany), ENDA (Sweden), USAID (Mali/Senegal), Peace Corps (Mali), UNSO, FAO and DANIDA.

Many of the country delegates were particularly concerned with tackling the technical problems of constructing durable and acceptable mud stoves. The practical workshop on mud stove construction techniques was very popular judging by the numbers who chose it. The single-pot Louga stove was constructed along with a 2-pot chimney stove. Most of the participants managed to get their hands dirty, and we gathered a very large and curious audience! The second most popular workshop dealt with the organisation of communication between stove workers and users.

At the conclusion of the seminar everyone agreed that no single stove design or construction technique was suitable for mass dissemination. Instead it was recommended that at least 3 designs should be selected. There was a certain amount of healthy dissent amongst the participants about the eligibility of different designs. However, everyone agreed that there was still a considerable need for continuing field-testing efforts and optimisation of designs before mass dissemination could hope to take place. It was strongly felt that at least one prototype of portable stove, whether metal or pottery, was an urgent priority for research.

Alternative Cooking Stoves Zimbabwe

Brian MacGarry

(Brian MacGarry works from Silveira House at Harare, Zimbabwe, for a church-based private voluntary organisation which carries out hardware development and runs training courses in the energy field.)

Several technologies are being used to combat the growing shortage of fuelwood in Zimbabwe: improved woodburning stoves, biogas and solar cooking. This short summary is written from the viewpoint of one of the centres involved in this work, and thus does not claim to cover all that is going on.

Two of the wood-burning stoves that have aroused interest in the eastern part of the country are the Lorena stove, and a modification of the iron frame 'stove' described by Jaz Gill in Boiling Point No 2. Both are reported by users to give 65-70% fuel saving as compared to the unmodified iron frame, and both make much more effective use of low-grade seasonally available fuels such as dry maize cobs.

Lorena stoves are generally built against the wall of the round thatched kitchen, so that the chimney can be taken out through the wall. They generally have places for three pots - one for the sadza (stiff maize porridge), one for vegetable or meat relish, and one for hot water - and often an oven.

This type of stove is favoured not only because it saves fuel, but because it produces very little smoke and it presents a more 'modern' image: young housewives want to stand to cook, while older women prefer to sit on a chair or on the floor, and the stove can be built at whatever height suits the user. This flexibility in the design is seen as a great point in its favour. Suitable material for building the stove is easily available, and techniques for using it, eg in brickmaking, are well known. Construction however is slow and some stoves have now been built partly out of brick. This is likely to become more popular.

The bulk of this stove and its consequent nigh heat capacity make for good space heating, although when families gather around the central hearth in cold weather, many prefer to see a fire in the hearth.

The Iron Frame stove is closed in with sheet metal (which can be obtained from old 5 or 20 litre tins) on three sides and the top, so as to give a sheet metal stove with an opening through which fuel is inserted and holes in which the pots sit.

FIGURE

This is favoured because it saves fuel, produces much less smoke, and can do all that an open fire does, no other fire is ever used to heat the house, and unlike the Lorena stove, it can be used, for example, to smoke meat to preserve it.

Both of these stoves can be built for less than Zimbabwe $5 (£4).

The advantages of both these stoves are most obvious in the area in which the iron frame grate is already widely used, and cooking is almost always done indoors, outdoor cooking being only for brewing beer or cooking large amounts of meat for social gatherings. Where more cooking is done out of doors, especially in western parts of the country, less bulky clay-and-brick stoves are gaining popularity.

The solar cooker is the next most expensive option for cooking, and the model developed is a simple absorbing box solar cooker. Such a cooker is capable of cooking a total of 3 litres of sadza and/or stew, twice on a sunny day (about 240 in an average year), and is easy to construct for a cost of about ZS40 (£32). Foam rubber sheet insulation is not the cheapest, but it seems to be the best to use as it greatly simplifies construction.

FIGURE

With this cooker, a new method of cooking sadza must be learned, and this deters some potential users, but a few dozen of these cookers have come into use in the past year or so. The ability of this cooker to cook common, simple dishes with little attention, its portability, (so that women can cook while working in the fields), and the fact that the pots do not become dirtied by soot, are all appreciated.

Demand is now growing for a solar oven capable of roasting meat and baking bread (at up to 200ºC). Such an oven, fitted with concentrating reflectors, and using glass wool insulation, has been tested and demonstrated. It can be produced at a cost not much greater than that of the simple cooker. Since the solar oven must be moved frequently to track the sun, it requires more attention in use, and we have yet to see whether this presents any problems.

Biogas is the remaining option; it is more costly, but a slightly modified 8 cu m version of the 'Chinese type' of digester, big enough to provide for all of a family's cooking, can be built for less than Z$400 (about £300), including the cost of the cooker. This is not prohibitive in Zimbabwe, as in the last 2 years thousands of peasants have earned more than Z$1000 annually from the sale of crops, most of which goes to capital development on the farm. Peasant families have also shown their ability to manage this type of digester.

The main modifications we have made in this digester are the use of old inner tubes as gasholders, (to minimize pressure in the digester), keeping 50 cm depth of water on top of the lid (see drawing), and painting the interior with bitumen.

FIGURE

Users like biogas because it saves wood, is clean, looks modern, and the digester provides improved fertilizer in the form of spent slurry. In the next stage of development, more digesters are to be built at community centres than in private homes, and this may prove the most economical system if they are to get the same attention and maintenance as those already installed.

We cannot yet conclude which of the cooking stove technologies will be most significant in the long run, maybe some new variant on one of these may overtake them all, but all seem to have a secure place in the overall picture for cooking in Zimbabwe.

Evolution of Insulated Stoves in Kenya

by Bill Stewart
ITDG Stoves Project

In 1981 and 1982 a considerable amount of publicity and effort went into the promotion of the need to produce more efficient charcoal stoves for use in Kenya.

One approach was to try to introduce the Thai bucket stove, an insulated pottery liner stove. In 1982 Max Kinyanjui, working with the Ministry of Energy and two other Kenyans from Clayworks, a private brick and tile company, went to Thailand to study the production system for the Thai bucket stove. On their return they worked on adapting the stove and production system to Kenyan conditions.

A number of design changes were made by Max Kinyanjui and others to the stove, to make it more appropriate. A tight fitting door was added so that the heat output could be reduced for the longer simmering periods of Kenyan cooking. To make the stove more robust, the bucket was made cylindrical instead of tapering, and metal stands were used instead of pottery stands to support the-pots.

Production of 500 of these stoves was then begun at a medium sized pottery workshop. The pottery liners were made at the workshop, the metal shells were made by traditional artisans. Insulation materials were bought in, and the whole stove was fabricated at the pottery workshop.

The final cost of the new stove was about 67 Kenyan Shillings (US$6.70) compared to KSh 20 (US$2.00) for a traditional charcoal stove. Laboratory tests showed that the new stove was faster and had fuel savings of about 30%. For an urban household using charcoal, the extra investment would be paid back in less than two months. However, the difficulties in organizing the various craftsmen for the stove production, the heavier weight, the problems of transporting the stoves, and the higher initial cost to the consumer, made it worthwhile to investigate other types of stoves and production methods.

Following the success of the introduction of charcoal stoves lined with cement and vermiculite in Papua, New Guinea, it was decided to adapt and test this stove in Kenya.

Vermiculite is a lightweight rock that is produced by heating a type of mica so that it expands to about 10 times its original volume. Both vermiculite and cement are products of Kenya, and when mixed, a lightweight, easily moulded, heat resistant material is produced which can be used to insulate the stove instead of pottery liners. A mixture of vermiculite to cement of 3:1 produces a material with a density of 0.8 gm/cu m. Max Kinyanjui, with assistance from ITDG, designed a simple production procedure for a lightweight, cheap cement-vermiculite stove. A plastic bucket is placed inside a traditional metal stove and the mixture of cement and vermiculite is packed in between the bucket and the metal wall to produce a lining approximately 4cm thick.

A testing programme was then organised to test different charcoal stoves that had been developed and were in production in Kenya. m e Kenyan pottery liner stove, two cement-vermiculite stoves, four types of UNICEF UMEME stoves, and the traditional jiko were chosen for testing.

Test Stove Data

STOVE TYPE	STOVE WEIGHT	APPROX COST	FIREBOX INSULATION
	kg	KSh
C-V*, top only	4.2	30	C-V
C-V, fully lined	6.6	35	C-V
Pottery liner	7.9	65	Pottery & ash
Traditional jiko	2.8	20	Metal
UMEME Fig 5	4.0	100	Metal & air
UMEME Fig 6	4.0	100	Metal & air
UMEME Fig 7	4.0	100	Metal & air
UMEME Fig 8	12.5	100	C-V

*Cement-Vermiculite

Test Procedure:

All tests were done with 300 gms of charcoal. A 12 gm piece of paper soaked with 8 gm of kerosene was put in the bottom chamber of the stove and lit. A covered aluminium pot containing 2 litres of water was placed on the lighted stove and brought to the boil. After boiling, the door was left open for high power tests and closed for low power tests. m e times taken to ignite and to boil the water were noted, and the PHU2 calculated.

The tests were repeated 4 times for the two cement-vermiculite stoves and the traditional jiko, but fewer times for the other stoves because of time constraints. The Standard Deviation did not exceed 6% of the mean PHU values for the tests repeated 4 times.

FIGURE

FIGURE

FIGURE

Test Conclusions:

1. The time taken to ignite did not differ greatly between all the stoves.
2. The insulated stoves are all significantly faster to boil than the traditional jiko (33% faster) significant at the 1% confidence level).
3. The insulated stoves are all more efficient than the traditional jiko, and the difference is more pronounced at a high power output (31% more efficient on average) - significant at the 5% confidence level).
4. It was not possible to lower the evaporation rate of the UMEME liner stove and the cement-vermiculite fully lined stove below 10 gms/minute, and it was not possible to get greater evaporation rates than 10gm/minute for the traditional stove.
5. The performance of the UMEME stove was very dependent on different grate designs. The model with an insulated firebox had the best performance (Fig 8).

Sequel

The cement-vermiculite stove with only the top section lined, besides having a high efficiency and variation of heat output, was also the lightest, cheapest and simplest insulated stove to produce. Because of these positive attributes a small production system was set up to produce the stoves. In November 1982 over 100 were produced to be used in a field trail. The performance of both the cement-vermiculite stove and the pottery liner stove will be monitored to see which stove and production process will have the greatest chance of success for widespread dissemination in Kenya.

FIGURE

Improved Stoves in Niger

by Ralph Royer
Church World Service

(Ralph Royer is Consultant for Appropriate Technology and Renewable Energy for the Church World Service in Niamey, Niger. The CWS stove programme began in 1980, and with the assistance of Angela Williams and Djibo Oumarou, the project has introduced over a thousand stoves (mostly Kaya and Banfora types), predominantly into urban areas. What follows are edited extracts from Mr Royer's 1982 annual report.)

Stove Project in Niamey

The number of stoves built in the first phase (350) was attained in December 1981, and with the funds remaining a second phase was launched, for 1982/3 to put 20 stoves in each of the remaining wards of the city, a target total of 440. For this second phase the amount paid by recipients was doubled (to about $9), and the stove shelter was discontinued (except for banco/adobe stoves of which few are built in the city). These changes in the programme had a noticeable effect on the demand for stoves.

There were 315 stoves built in 1982 as part of the project with the Women's Association of Niger (AFN), managed by an AFN-appointed woman director. The stove construction team consists of the Co-ordinator-Animatrice, an Animatrice, 2 mason instructors, a chauffeur, and 2 apprentice masons. This has proved to be a large team to manage and is an area needing improvement. The apprentices are changed about every two months with the intention that they will become stove constructors, but this has not worked well due to the transient nature of most of the apprentices, and the lack of a system to set them up in business. The Animatrice works alone on a follow-up programme teaching women to use the stoves effectively.

Work in Rural Training Centres

20 couples are trained in each centre for one farming season (9 months) to learn improved techniques and methods of farming. Improved cookstoves was one idea to which the women especially, were exposed. Two stoves were built in each of the 7 centres in the Niamey Department and then demonstrations were held for the trainees to show them how to use the stoves, and to learn how to build one for themselves when back home. All the stoves were made of banco (adobe). A similar programme was worked out for the 12 centres in the Dosso Department.

During the first year of this type of involvement, which does not take a great deal of money and yet is an effective means of disseminating stoves, the following lessons were learnt which will enable improvements to be made in future:

1. the stoves need to be strong to withstand institutional use;

2. someone must be appointed at each centre to be responsible for stove maintenance and repair;

3. introduction of a one pot stove is desirable as there is frequent use of only one cookies pot;

4. the length of training period for stove building must be increased to enable trainees to get a good grasp of the process;

5. there is a need for booklets snowing how to build and use the stove - these can be used in the literacy classes and taken home by the couples.

Stove Design and Development

During the year we started work with a one pot stove which is built up from the usual three stones as a base. A banco wall is built around the pot, leaving the 3 stones in the wall. An arched doorway is cut out or left in the wall for insertion of wood. Smoke and heat come up around the pot, and the wall prevents wind carrying the heat away. With some air holes added at the back side it works exceptionally well.

Personally, because of its simplicity to guild, and the Lack of many critical tolerances to contend with, I think it has one of the best chances of achieving 'self-dissemination'. The main disadvantage is the lack of a chimney to carry away the smoke.

FIGURE

Improved Malgache Stove: Following the CILSS regional stove conference in Bamako (Dee 1982) we began working to improve the locally made metal ring that is used to support pots while cooking. We raised the sides to give wind protection and put in a grate to help improve combustion. These modifications have not been tested yet. We feel that something of this nature may help reduce fuel costs for those who cannot afford our other stoves, have no place for a more massive stove, or who do not want to pay $9 rent for a stove they cannot take with them when they move.

In addition, we have begun work with local manufacturers of cast aluminium pots to incorporate a ring or collar into the pot to allow it to be suspended or supported by this ring. This will open up the entire bottom surface of the pot to the fire and thus allow better heat exchange. We have just finished building several stoves adapted for use with the special pots. Several stove experts have suggested the principle in the past, and it turned out to be relatively simple to put into practice. Considerable interest was shown when we displayed out first model at the Bamako stove conference.

Work on protective coverings for banco stoves continues. So far old engine oil rubbed into the stove seems to be the most effective. A mixture of fresh cow dung, ashes, and clay, also worked fairly well.

Evaluation

An evaluation of the project was carried out during July and August, 1982. It was pleasing that we were able to get various government services, international organisations, and individuals together to work out the methods to be used and also to carry out the evaluation. We hope that this augers well for cooperative interest and work with stoves.

Among the things pointed out by the evaluation team were:

1. So far we are only touching the upper levels of urban society. The poorer sector' who rent rooms, do not have space for a large stove nor do they want to invest in something which they may have to leave behind.

2. The stove is frequently used incorrectly mainly as a result of using only one pot at a time, and so we are working on one pot stoves.

3. We found that there had not been enough teaching and training in the use and maintenance of the stoves, and so we are increasing the extension staff.

4. The chimney is one of the weakest points of the stove, it being too easily broken and needing cleaning on a monthly basis.

One of the concerns I have is for maintaining standards as the wave of interest in stoves mounts. We find that even though we are building a relatively simple stove, there are a host of complex factors that play a part and several critical dimensions that must be respected. As training goes from one person to the next, little errors creep in which can alter drastically the performance of the stoves.

Consequently, I am thinking more and more about the value in promoting for the time being one of the simplest ways we have of reducing fuelwood consumption, which is simply protecting fire from the wind and forcing the hot air up around the cooking pot. On the other hand we must continue to search to improve the efficiency of woodburning stoves and at the same time look at other possible areas to find sources of energy to meet this basic need of mankind. We have done some work with the coal found in Niger, and in future would like to work with solar and possibly bottled gas.

One tendency I note is the acceptance of a certain model of stove or organisational structure, and then to stick to it rather than continuing a flexible position or attitude, always looking for improvements. The state of the art is still in its infancy and we must do what we can to keep all avenues open to see which has the best chance of success.

Avoiding Pot Holes in the Structural Design of Pottery Stoves

SOME NOTES......

by Stephen Joseph
ITDG Stoves Project

To date we have discussed how ceramic stoves crack due to thermal stress, but stoves also crack because of poor structural design.

Fired clay is a very brittle material that has a relatively low strength and a low resistance to impact, and thus cannot bear heavy loads. Ceramic stoves must therefore be carefully designed to reduce the likelihood of fracture.

To understand how to design structurally sound stoves it is useful to have some understanding of the theory of crack formation and propagation.

Most ceramic materials have imperfections present in the clay; impurities such as small stones. But they can also have imperfections which are incorporated in the manufacturing process, for example, badly joined pieces or uneven thicknesses of clay will subject the object to further stress on firing. It is the ready propagation of cracks from these defects that give ceramics their characteristic low shock resistance.

When a material is subjected to a load (eg putting a pot on a stove) the stress (force per unit area) at the imperfections is locally very much greater than in the body of the material. Cracks will start to grow and if the applied load is greater than some critical value the crack will rapidly grow larger, resulting in the failure of the material. Cracks are more likely to propagate from right-angled joins, where there is a concentration of stress. Stoves are not only subjected to this mechanical loading but also to thermal loading. Stresses are established because one part of the stove is hotter than another, and the greater the local temperature difference, the higher the stress. (For a more detailed discussion on the theory of crack propagation see "STRUCTURES" by J E Gordon, published by Penguin Books 1978.)

Some general rules governing the design of stoves emerge from an understanding of the concepts of stress concentration, and the formation and propagation of cracks.

1. Avoid putting sharp corners in your stove. For example:

- Doors

FIGURE

- Adjoining tunnels and pieces make sure joined pieces are gently tapered and rounded, avoiding right-angled joins

FIGURE

2. Never place the air entrance and flue gas exit on the same side of the stove - place them opposite each other. The narrow space left is particularly susceptible to stress.

FIGURE

3. Always try to build a stove out of cylinders to avoid the high stresses that result from bending in flat shapes: ie exploit the natural strength of curved shapes (arches or domes)

FIGURE

4. When the food in the pot is likely to be stirred vigorously during cooking, or if large pots are used, it is essential to reinforce the ceramic, or remove the load from the ceramic in some other way. This can be done in a number of ways - (a) to (d) illustrate some well used methods.

a) Place mud around the ceramic and sit the pot on the mud

FIGURE

b) Use a metal frame

FIGURE

c) Use a double walled stove

FIGURE

In both (b) and (c), avoid a 'wedging' situation between the pot and the edges of the pot opening, otherwise problems could occur with differential expansion between the pot and the pot seat.

d) Use an outer metal casing

FIGURE

5. Reject stoves that have black marks, after kiln firing, on the inside or outside of the firebox. The black mark indicates a spot that has been reduced in the firing. Localised reduction may weaken the clay at this point.
6. Avoid features that give rise to high temperature gradients, for example, baffles under the second pot seat.

ENCLOSURES

With this issue of Boiling Point you should also receive a copy of Technical Notes ho 2 'Optimisation of Chimney Stoves' and No 3 'Testing of the Zip Ztove'. (No 1 in the series 'Comparative Performances of Kenyan Charcoal Stoves', mailed with BP No 3 was called a Technical Paper, but it was pointed out that ITDG Publications Ltd is issuing a series of Technical Papers hence the change of name.

Radiation and Stack Losses

by Siddhartha Bhatt
Central Power Research Institute,
Bangalore, India

Firewood, as such, does not take part in heat transfer, but the flames do. Firewood is converted to flames which transfer heat. A flame is a hot mass of burning carbon particles, when it cools down sufficiently the mass of residual gases are called flue gases.

The flame radiates heat in all directions. When the radiation is blocked by a solid wall (such as the inner surface of the combustion chamber) the wall takes up heat and conducts it away from the flame zone. If the radiation is not blocked it is lost to the environment. After the flame transfers heat to the vessel the hot flue gases moving into the environment carry away heat. The two main losses that can be identified are radiation, and stack losses.

The radiation loss can be subdivided into radiation to solid portions (walls, vessels, etc) and radiation to the rest of the environment.

In wood combustion the energy losses can be pictured in terms of wood lost per hour per area (for radiation), or wood lost per kg of wood input (for stack losses). The energy loss is converted on the basis that 1 kg of wood is equivalent to 1.42 MJ. Radiation lost to a stove wall is only 0.1 gm of wood per hour per sq cm. Direct radiation to the environment is 25g/hr/sq cm Thus a stove opening (for fuel feed or pot) loses 250 times more heat than that to a wall. It was this observation that led people who cooked on open fires to burn wood in a closed combustion chamber, which evolved into the traditional cookstove. Incidentally, the cookstove also provides wind protection to the flame and fire protection to the users.

The traditional cookstove has many openings to the combustion chamber - the fuel feed opening and the pot-hole(s) being the major ones. These are zones where severe heat losses take place. A conventional cookstove loses, from these two places, - 2 to 4 kg of wood per hour in energy losses. If these openings are closed or optimised, a 250-fold saving in the wall energy losses can be achieved and this can be about one third of the overall fuel consumption.

Now, about the gases that leave the stove as waste. These range in temperature from 80ºC to 400ºC and the loss is of the order of 70 to 440 gm of wood per kg of input wood. At 100ºC, 200ºC and 300ºC the losses will be 90 gm/kg, 210 gm/kg and 330 gm/kg of input fuel respectively.

The stack loss is linked to the radiative loss. When the latter is more the fuel consumption increases. The stack loss increases as fuel consumption increases.

FIGURE

The solution to minimising heat losses would be to plug all openings in the fire burning zone by using dampers and shields at the fuel door openings. As far as possible the fire must not be visible at all. An incidental advantage of this scheme is that fire hazards and inconvenience due to radiative heat is reduced. This solution may result in the shooting up of the stack gas temperature. The stack gas heat can be utilized by the old technique of using a multiple pot opening system. Dampers at the connections in between two pots is also suggested to control the stack losses.

Reviews

We were very pleased to receive some 'stove' publications from the training section of the Peace Corps in Benin. They were written by Stephen Connors. Although basically written for local use, it is very interesting to see other stove workers' approach to the writing and presentation of stove literature. We hope that readers will send us more - which we will review, summarize, or even print in full, to give ideas to those about to embark on a similar publication.

The STOVE DESIGN HANDBOOK by Stephen Connors is a 12 page leaflet on the basic design principles of wood conserving stoves, well set out, with attractive drawings. For example.....

FIGURE

The leaflet gives a straightforward explanation of 'how a fire works', followed by the general mehods used to maximise combustion, radiation, convection and conduction. It does not go into detailed stove construction, but gives a good coverage of the basic elements. m e leaflet ends with sections covering the vital cultural, economic, and safety factors that must be considered as part of stove design.

The handbook did not indicate the audience for whom it was intended, but we think that it would make useful introductory reading or discussion material in the training of stove programme extension workers.

We also received SOTA STOVE CONSTRUCTION, an instruction manual written by Mr Connors for the construction of the Sota stove, a one pot, chimneyless mud stove (made of 'banco' in Benin), which is a 'refined version of the Louga variety of stoves first developed in Senegal'.

As a construction guide we feel that more drawings, with labelling, and a better layout of the step-by-step instructions are required. However, as a back-up document to a stove building demonstration it would be very useful.

Focus on Testing

In December 1982 a meeting of stove testers from Asia, Africa, Latin and North America, Europe and Australia (Stephen Joseph!), was held in Washington at the head offices of VITA (Volunteers in Technical Assistance). The purpose of this meeting was to draw up a recommended procedure for the field testing of stoves (in draft form). The meeting was highly successful - agreement was reached on a procedure and a draft publication is being produced by VITA. Participants agreed to test this procedure over the next year and determine what changes may be necessary in the light of experience.

Discussions with the staff of Cookstove News are underway to produce a joint edition on testing methodology and practice.

In the last three months we have received two reports on testing, and a summary of these follows.

I COMPARATIVE WOOD CONSUMPTION IN 'IMPROVED' COOKSTOVES

by Stephen Connors, Peace Corps, Lenin

Stephen Connors (in Lenin, West Africa), carried out controlled boiling water tests on a 3-rock fire, a locally produced metal stove, a modified version of this metal stove (with sand insulation), and a SOTA stove (see REVIEWS).

The test procedure used was that described in Tim Wood's paper 'Laboratory and Field Testing of Improved Woodstoves in Upper Volta'.

The PHU values calculated from the test results were compared with those from tests carried out by Wood on an open fire and on four stoves built in the Upper Volta. He found that when compared with the 3-rock fire, the three stoves from Benin and the four stoves from Upper Volta show a decrease in wood consumption greater than 30%, and an increase of PHU of 40%. However, if the same comparison was made between the existing metal stove in Lenin and the other 'improved' stoves, only two of the latter, one from Benin (SOTA) and one from Upper Volta (CATRU-A) showed a decrease in fuel consumption of 20% or more, and an increase in PHU greater than 20%. Given that the CATRU-A costs over $30, and the existing Benin metal stove costs $1, he questions whether this is a viable alternative.

FIGURE

He concludes that it is necessary to consider not only wood fuel savings, but also economic and social factors when designing a stove.

II CHARCOAL STOVES AND THE POSSIBILITIES FOR IMPROVING THEIR EFFICIENCIES

by Michael Drohan, University of Bradford

Mr Drohan's report is of some of the work carried out at Kenyatta University College, Nairobi, as part of a research project on the efficiencies of charcoal stoves.

Two separate sets of experiments were carried out, on 8 charcoal stoves, using slightly different methods. Five stoves were tested using the first method, and one of these five (the traditional Kenyan jiko) and the remaining three stoves were tested using the second method. The two sets of results for the traditional Kenyan jiko therefore provided a comparison between the two methods.

In the first set of experiments, cooking conditions were simulated by using a fairly standard aluminium pot (diameter 25 cm) and a fairly standard cooking load of 3 litres of water. me water was heated from room temperature (approximately 20ºC) to 85ºC and was then discarded and replaced by a fresh lot of water. (The water was decanted at 85ºC to avoid complexities arising from high evaporative losses as boiling point is approached.) This process was continued until the charcoal load ceased to yield a rise in temperature of the water in the pot. The accumulated temperature rise multiplied by the mass of water and by its specific heat, was reckoned as heat effective in cooking. Heat used in raising the temperature of the pot was reckoned as heat losses together with convection and radiation losses from the sides of the stove and the pot.

For the second method a 40 litre container was constructed on the top of an ordinary aluminium cooking pot so that a normal load of charcoal (0.75 kg) would raise the temperature of its contents to between 70ºC and 80ºC. The reservoir built on the cooking pot was insulated with fibre-glass wool and covered with a coating of diatomite, leaving only the surface of the cooking pot uninsulated as in normal cooking conditions. The temperature was measured automatically by means of a thermistor, the output of which was fed into an operational amplifier and an electronic recorder.

The author points out that convection and radiation losses from the sides of the container would be much higher under normal conditions of cooking (as the pot contents would be brought to the boil, and then simmered or kept boiling more vigorously), but the experiments were designed to demonstrate the relative performance of various designs of stoves.

The heat of combustion of a sample of the charcoal used in the experiments was determined and the efficiencies of the stoves calculated from the heat outputs found in the tests. m e results below are taken from the report.

"Absolute Efficiencies of Various Charcoal Stoves"

STOVE	METHOD
	First	Second
Traditional Kenyan Jiko	20.5%	21.9%
Bellerive Model I	18.0%	--
Bellerive Model II	20.7%	--
Variant of Bell. Model I	19.6%	--
Schmalzle Stove	28.5%	--
Traditional stove with brick lining	--	27.4%
Traditional stove with clay lining	--	29.2%
Thai Bucket Stove	--	34.2%

The author concludes:

"The research and testing here reported revealed that modifications to existing charcoal braziers have produced improvements of the order of 50% on the existing ones without considerably increasing the cost of the stove. If universally adopted for charcoal burning, this technology could reduce the consumption of charcoal by one third. m us from the energy point of view, without consideration of afforestation and reforestation strategies, and more efficient methods of charcoal production, improvement in stove technology could make a considerable contribution to conservation of renewable energy resources. However, as pointed out at the beginning of this paper, this is only the technical dimension of the problem of renewable energy conservation and as such is incomplete without an analysis of the political economy of renewable energy."

BP No. 3 Village Studies in Sri Lanka

Yvonne Shanahan was to continue this article with a case study of a Kandyan village, and give an overall look at the implications for Extension of new stoves in Sri Lanka. Yvonne is about to visit Sri Lanka again, to continue with another aspect of village studies. Accordingly her article is postponed until the next Boiling Point so that the earlier studies can be reappraised in the light of a recent visit.

INFORMATION WANTED

Members of the stove team are currently working on the mud stove section of a training manual. They would be interested in hearing from anyone who has information on the following:

1. Additions to mud stove mixes besides sand and clay.
2. Experimental mixes for protective surface coverings of mud stoves (eg. Royer, page 11 "so far engine oil rubbed into the stove seems to be the most effective".

Mud Stoves in Malawi

by Dr G M Mhango & Dr N S Cooper
Blantyre Polytechnic, Malawi

(The following is a shortened version of a report on the status of mud stove building in Malawi, which the authors assessed assisted by funds from the Blantyre Polytechnic. The authors hope that it will lead to unification of the work on mud stoves in that country.)

Introduction

At the National Appropriate Technology Co-ordinators' meeting in Nairobi in December 1982 it was suggested that Blantyre Polytechnic (Malawi) should research into the possibility of introducing mud stoves in Malawi. Until preliminary work was started it was not realised how much work had already been done.

History

The traditional method of cooking in Malawi is using three stones. The earliest reference to mud stoves found, was made in the 1930's by teachers at Jeans School, Domasi. In fact, it has been suggested that the mud ovens used for commercial bread baking in Mzimba District were introduced by an ax-student of this School.

The next reference is in the 1960's with a suggestion by a UNICEF area officer that Magomero Community Development Training College should both build and encourage the use of mud stoves. This idea spread to the Thuchila Farm Institute (Mulanje District) and at both institutes, mud stoves, of various designs, have been built and tried ever since.

Since 1980 work on mud stoves has expanded world-wide, including Malawi. The Energy Systems Unit of the Ministry of Forestry and Natural Resources has a project constructing and testing mud stoves at Colby College of Agriculture. A low-cost housing project at Sadzi in Zomba has used the 'Lorena' type stove. The University of Malawi (including Blantyre Polytechnic) has been the most recent participant in research programmes related to mud cooking stoves.

Why Mud Cooking Stoves?

One important reason is to save wood, although a recent survey has shown that villagers do not realise that there is a firewood shortage, and have no strong reason for saving wood unless they travel large distances to get it.

Like much of the developing world, Malawi is facing the problem of deforestation. More trees are cut than are planted each year, and if an efficient mud stove could be designed which would use much less wood that the 3-stones fire, then its widespread introduction could solve the deforestation problem. The prospects for designing such a stove are high, but whether they would work efficiently in the rural situation is uncertain, as the stoves would not De built exactly to design unless a lot of money were spent to train stove builders.

Another important consideration is nutrition. If cooking can be made easier and quicker for the women, then hopefully they will cook more often. If two or three pans can be heated at the same time then a greater variety of food could be cooked and hence a more balanced diet provided.

Other positive benefits of the introduction of mud stoves would be the increased safety of a covered fire, stability of the pots, and the reduced effect of strong winds, which makes using the 3 stones difficult.

However, there are disadvantages: they provide less light and warmth, most designs of mud stove are not portable, and there are still problems with the designing of an efficient and long lasting stove.

One important decision to be made is whether to use only locally available materials (such as clay and sand) or to use metal as well. Not using metal keeps the cost at a minimum - except for labour costs. However, by using metal particularly for chimneys- a stronger and longer lasting stove is constructed. Both approaches nave been made by the groups working on mud stoves in Malawi.

Energy Systems Unit: Lilongwe

This unit has built and tested some very efficient stoves at Colby College. The nest stoves use only 50%-60% of the wood consumed by the 3-stones. The whole stove, including chimney, is made of mud, the mix being 50° anthill clay and 50% dambo sand.

FIGURE

Their designs are improvements on earlier ones: the changes made were

- reducing the size of the firebox

- enlarging the previously very small passageways

- cutting a lip around the pot holes, so that the pots sit lower down and are more stable

- introducing a sloped bottom so that the hot gases are directed up to the underside of the back pot (baffle effect)

- modifying the mud mixture in an attempt to solve cracking problems

- supporting the chimney against a building to overcome chimney breaking.

The stoves using significantly less wood than the 3-stones take as much time to cook. Other Unit designs were found to cook faster but tended not to save wood.

The Unit hopes to start field trials of their stoves.

Magomero CDTC

Stoves have regularly been built here by trainees since the 1960's, but they have proved to be less efficient than the 3 stones. A wide variety of stoves has been tested, the most efficient being one similar to those of the Energy Systems Unit.

Thuchila Farm Institute

Again, various designs have been tested. Most recently efforts have been concentrated on a large Lorena type stove.

FIGURE

This stove has been introduced into the rural area by extension workers. The reactions of the villagers have been

Advantages over the 3 stones

- safer, children cannot fall into it, and it never gets hot enough outside to cause burns

- more secure (pots falling from 3 stones wastes food)

- quicker

- Better in windy weather, when it is difficult to use the 3 stones.

Disadvantages compared with the 3 stones

- it consumes more wood
- it does not provide as much warmth and light
- it is fixed.

Also, these stoves have suffered from cracking - particularly above the fireboxes. This has been overcome by smearing with more of the mud mixture (50% clay, 50% sand) when required.

Zomba

Mud stoves have been built in the low-cost houses built at Sadzi for the UN Centre for Human Settlement project. They have 4 pot-holes and a metal chimney, but tests have shown them to be less efficient than the 3 stones. Two stoves were rebuilt but severe cracking problems followed.

Related Subjects

1. Hay Boxes

These have been investigated by the Energy Systems Unit and Thuchila Farm, the former finding them highly efficient, while the latter having problems in getting them to work.

2. Charcoal burners

These are popular in urban areas. The Polytechnic plans to investigate possible design improvements, and the authors know of no other work in Malawi done or planned for charcoal burners.

The Future

Much useful initial work has been done on mud stoves in Malawi, but some work has been duplicated. A meeting of everyone working with mud stoves in Malawi would be beneficial, to share the results, both successes and failures, and to formulate a joint plan of action for the future of improved stoves in Malawi.

ITDG stoves project manager

Stephen Joseph has run 'the ITDG stoves programme since 1979, but as many of you will know, he is Australian, (as is his wife), and they feel it is time to take their two children 'back down under' to see the grandparents. So as of 31st March Stephen has resigned as Manager, but will De based in the UK for a few months more as a consultant to the Stoves Project.

The post of Stoves Project Manager has been advertised in the UK and the information circulated to selected organisations with a closing date for applications of 31st March. However, applications from interested readers of Boiling Point who missed this information, will be taken into consideration, assuming that no appointment is made in the meantime.

Intermediate-Technology Development Group

BIOMASS TECHNOLOGY FOR RURAL DEVELOPMENT

ITDG is seeking a Manager for its internationally recognised Stove Programme, funded by the Overseas Development Administration. me goal of the Programme is to develop and disseminate improved, fuel efficient cooking stoves collaborative research is presently being undertaken with institutions in Nepal, Sri Lanka, Indonesia and Kenya. The Programme is also closely linked to ITDG's other biomass and forestry initiatives.

The applicant should:

- be qualified in a natural science/engineering discipline with social science experience, or possess a social science qualification with substantial technology based experience.

- have relevant Third World experience particularly in rural development

- have sound project management experience

- be an effective written/verbal communicator.

Location: The Programme is currently based at Shinfield, near Reading, UK. Considerable
overseas travel is required.

Salary: circa £10, 000 negotiable

Closing date for applications: AS SOON AS POSSIBLE!

Further details from:

ITDG (Biomass Recruitment)
9 King Street, London, WC2E 8HN
Tel: 01 836 9434

NB ITDG regrets that it has no funds available for relocation expenses, or for travel to the UK for interview.