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close this bookBoiling Point No. 26 - December 1991 (ITDG, 1991, 32 p.)
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View the documentStove Technology Transfer
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View the documentImproved Stove Promotion in Three Indian States
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Does Anyone Need to Design a ''New'' Stove?

by Myles Allen, Bellerive Foundation, Nairobi, Kenya

In fact, is there any such thing as a "new" stove design? We in the Bellerive Foundation have been working on woodfuel conservation in East Africa for seven years now. And we have come to the conclusion that the answer to both questions is usually "no". But we have also found that, although stove designs are plentiful enough, adapting and applying an existing design to a new context (new project, new country) requires considerable care. This is an example from our recent experience to show what we mean:

Development of a stove for small hotels and restaurants in rural Kenya

Bellerive Foundation, in collaboration with the Kenya Forest Department and the British Overseas Development Administration (ODA), has been running a District Focus Fuelwood Conservation Project (DFFCP) in Embu, Meru and Isiolo Districts since 1988. Initially the DFFCP had two key areas of activity. First, the conservation of woodfuel in large catering institutions, through the introduction of improved catering equipment and better woodfuel management; and second, the conservation of woodfuel among domestic users through education in efficient cooking practices. In 1989, it was decided to widen the scope of the programme to address woodfuel consumption by small hotels and restaurants ("hotellis") in the three Districts.

By that time, the Conservation of Fuelwood in Institutions (CFI) project had become extremely successful; so successful, in fact, that the basic institutional stove design disseminated by the CFI project has since become the de facto standard for most Kenyan schools, hospitals and other large-scale catering institutions. The catering requirements of hotellis arc in many respects similar to those of schools (they cook the same dishes, both use woodfuel, both generally use unskilled labourers to operate their stoves etc). Thus, at first glance, extending the

CFI projectto this new sector seemed completely straightforward. However...

There is an old saying: "If the only tool you have is a hammer, you see all problems in the form of a nail." For projects involving technology transfer to avoid this trap, it is essential to follow this process: begin by defining the problem, then identify the "tools" needed to deal with it and only then look around to see whether these tools can be picked up easily from other projects, or whether they need to be developed laboriously from scratch.

The Objective-Constraint Matrix

So the first of our activities was a survey of the catering requirements of small hotels and restaurants, both formal and informal sector, in the three districts covered by the DFFCP This survey defined the following key objectives for any project aiming to assist this sector:

1) To improve catering hygiene
2) To improve working conditions for catering staff
3) To improve the cost-efficiency of catering operations by reducing waste of foodstuffs and fuel, particularly expenditure on charcoal.
4) To reduce the environmental damage done by woodfuel consumption, in particular by reducing the consumption of indigenous trees in the form of charcoal.

At the same time, the survey identified a number of constraints, including:

a) Because of intense competition, private-sector catering operations, particularly those in the informal sector, were operating close to their margin of profitability. Hotelli owners would evaluate any new idea almost exclusively in terms of its impact on profits.

b) Many hotelli operations were relatively insecure, pardy because of their unclear legal status and frequent changes in the enforcement of regulations. In consequence, typical time-horizons for evaluating new investments were extremely short. If an investment did not show a positive return within a few months, it was unlikely to be acceptable.

c) Many hotellis were operating in improvised accommodation, with a strong possibility of moving within a year or two at the most.

d) The cooking area was generally the same as or adjacent to the area where customers ate. Thus almost all cooking was done on charcoal braziers ("jikos'). Open wood fires could not be used because of the smoke, despite the fact that firewood was generally available and much more economical to use than charcoal.

e) Charcoal use was very inefficient. First, because charcoal production in these districts is largely an informal-sector activity, an estimated 60% of the energy in the wood was wasted in converting it to charcoal in traditional kilns. Second, because the traditional jikos were themselves inefficient, they utilised at most 20-25% of the energy in the charcoal. This gives an overall system efficiency of 8-10%, even before transport and other losses are considered.

f) Despite these obvious inefficiencies, past experience with improved stoves in this sector was not encouraging. Improved (charcoal burning) Kenya Ceramic Jikos (KCIs) were not extensively used by hotellis, because working conditions meant that their ceramic liners tended to break unacceptably often.

g) Very few kitchen staff had received any specialist training for their work.

h) The total number of hotellis was very large. To be effective, a programme targeting hotellis could not depend on project staff giving target beneficiaries individual attention (as is the ease with the larger institutional stoves).

A look at the objective-constraint matrix (try drawing it out) shows that, while improved stoves would help in almost all areas, they are always only part of the answer. For example, objective-constraint pair 4e: to reduce woodfuel consumption given that charcoal is used inefficiently at present. You might think improved stoves are the obvious answer here, but they are only part of the answer. Cooking practices and firewood preparation have as great an influence on woodfuel consumption as does stove design (Allen - 1989).

Another example, objective-constraint pair if: improve hygiene given poor staff training. At first glance stoves don't seem to come into this one. But, of course, they do. Staff training levels were low because of rapid staff turnover, due to their extremely harsh conditions working with open charcoal braziers. Also, because relatively large numbers needed to be employed to operate the traditional stoves, hotellis could only remain profitable by employing low-wage, and thus low-calibre, staff. Install improved stoves, and you can recruit and retain fewer and better staff.

So improved stoves were one of the project "tools required" to emerge from our objective-constraint matrix, along with several others: including in particular improved staff training and promoting awareness of the need and scope for woodfuel conservation among Hotelli owners. These other activities form essential components of the project, although we will not discuss them here because the focus of this article is on technology transfer.

Requirements for the Design Specific design requirements for an improved stove for hotels and restaurants emerged from a more detailed look at these objectives and constraints. For example:

· Concerning objective 3, to improve cost-effectiveness of catering services. To minimise money wasted on burnt or under-cooked food, convenience and ease of operation should be higher priorities for the stove design than achieving the best possible fuel-efficiency. This may sound like heresy to a stove designer, but look at it this way: food production and (active or passive) woodfuel production make competing demands on land resources. There is no point in marginally reducing the fuel consumed by a stove if the result is frequent burning or under-cooking of food because the stove is difficult to control.

· Conceming constraint b, short investment horizons. It was clear that a low capital cost would be a higher priority than durability. A hotelli owner would be unimpressed by an expensive stove lasting 10 years if he or she was unsure if the business would still be operating in 6 months' time.

· Also concerning constraint b above, problems with fragile stoves. While long-term durability was not such a high priority, the stove would clearly have to stand up to rough treatment.

· Conceming constraint c, need for mobility. The stove would have to be designed so that it was easy to remove and re-install should the hotelli have to change location.

Armed with our objective-constraint matrix and a list of requirements for the design, we looked to what the CFI project had to offer.

Learning from experience

It was immediately clear that there were a number of problems with applying the CFI stoves to hotellis:

· Pots in the CFI stoves are fabricated from stainless steel. Although this makes for very good durability, the capital cost of the stoves, which are sold with pots fitted, is high (constraint b).

· The internal construction of the CFI stoves (brick firebox and stove walls) requires on-site construction and regular servicing by specialist stove-maintenance teams. It would clearly be impossible to establish a dissemination mechanism for such a design to hotellis (constraint h).

· The brick construction made it very expensive to move and re-install a stove once built (constraint c).

However, the basic firewood channel-stove-with-fitted chimney was clearly applicable, provided it could be manufactured cheaply and made portable. We drew up an outline design; aluminium pot, of the type mass-produced in Kenya; sheet metal stove-body, with minimum "frills"; a simple light galvanised pipe chimney. We then recognised that what was required was not a version of the CFI stove at all, but something much closer to a stove designed for the Woodbuming Stoves Group by Frans Sulilatu, of TNO Apeldoorn, the Netherlands, for the Tamil Nadu region of South India (Sulilatu - 1984).

Because aluminium pots are too weak to maintain their shape if suspended around the top of the pot (as the stainless steel pots are in the CFI design), Sulilatu designed the stove with the aluminium pot supported from below. The basic design, as adapted by the Foundation, is extremely simple. It consists of:

· A single mild-steel sheet cylindrical outer wall, about 5 cm larger diameter than the pot.

· No insulation: external wall temperatures remain safe during operation, and cost is more important than appearance to hotelli owners.

· A mild-steel disk, positioned horizontally half-way up the outer cylinder.

· A simple, box-like, sheet-steel firebox, suspended from a square hole in this disk, and offset so gases emerging from the firebox are drawn under the base of the pot.

· A reinforcing bar frame, which sits loose on the steel box, and supports the pot 12-15mm above it. This frame sets the width of the heat-exchange channel under the pot, guaranteeing the stove's efficiency even if the other components are not made exactly to specification.

· A ring, welded to the top of the external cylinder, which fits around the pot leaving a 5mm gap, which is small enough to stop smoke escaping once the stove has warmed up.

· A galvanised chimney.

While the design is neither as attractive nor as durable as the brick-lined CFI stoves, it has one key advantage: an ax-factory cost (including manufacturer's profit) of about US$80 for 30 litre Hotelli stove, instead of over US$300 for the 50 litre CFI stove.


The Bellerive Hoteli 50 litre stove

The benefits of technology transfer 50 litres and 30 litres capacity prototypes were produced, based closely on Sulilatu's specifications, and found to perform acceptably (PHU 40% and 36% respectively) in laboratory tests. Because Sulilatu had already carried out water-boiling tests on the basic design, to optimise key dimensions, it proved necessary to construct only four trial prototypes and two production models in the "lab-testing" stage of development. Only two design parameters needed to be optimised by repeated water-boiling tests: the firebox size and thickness of the pot-support grate, defining the gap between the disk plate and the base of the pot. Since we already knew from Sulilatu's work approximately what these parameters should be, the optimization exercise was relatively quick; three weeks from initial prototype testing to proceeding to field trials.

Having minimised the time required for technical performance testing, we were able to concentrate on manufacture (optimising the use of steel sheet), field performance (convenience of use, cleaning etc) and dissemination (making the product attractive to private-sector retailers): issues which all too often tend to be afterthoughts in a stove development project.

The Hotelli stove performed very satisfactorily in field trials. Follow-up surveys found that, by converting from charcoal to firewood (which is already marketed throughout all three districts), and using the new stoves, Hotellis reduced their woodfuel consumption by a factor of 3 or more. The Hotelli stoves work best with exotic (eucalyptus) wood as their fuel, reducing the pressure on indigenous trees. Most important of all for a Hotelli owner, at a retail price of US$140, the pay-back period on the new stoves (in reduced expenditure on fuel) is between 8 and 20 weeks. At the time of writing, negotiations are in progress with a number of leading private Kenyan manufacturers and retailers, to establish dissemination in the private sector.

The benefits of technology transfer in this exercise are very clear. The development of the Hotelli stove was considerably simplified through the use ofFrans Sulilatu's basic design, resulting in a more thoroughly tested and robust final product. We believe the key reason for this success was that the requirements for the Hotelli stove were defined systematically before we started looking at the designs available: making the exercise "problemled" rather than "solution-driven".