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edit this page An improved cooking stove for farming families
India's farming community constitutes some 65% of the rural population. In spite of socio-economic development during the last two decades, farming families in rural India are still attached to their traditional way of living. Their energy requirements are still met using locally available biomass fuels for cooking, simmering milk and preparing nutritious feeds for their cattle. The author has visited rural areas in various parts of the country and has observed that a typical farmer's family needs a bigger improved cooking stove from those currently available for normal domestic use. The stove, although made from mud, must be strong enough to bear the weight of heavier cooking pots of various sizes and shapes.
The details of different parts of the stove are shown in Figures 1-3. The following points should be noted: - The stove gives an average thermal efficiency of 24% at a burning rate of 2 kg per hour of sun-dried wood (acacia nilotica) and dung
- The chimney (Figure 2) produces an optimum intake of primary air into the fire box and helps to remove harmful gases
- A close fit between the cooking pot and the pot hole helps to reduce heat loss
- The 'tunnels' between the potholes and between the second pot-hole and the chimney inlet are positioned to reduce the speed of the gases leaving the stove. This optimizes the amount of heat reaching the second pot, thus improving overall efficiency
- The cone-shaped pot-holes can support pots of different sizes, varying from 25-30cm in diameter, or can support a combination of pot and hotplate of up to 40cm in diameter, or a square hotplate of a similar size.
- Pot-1 is used for cooking food quickly and for the preparation of cattle feed, leaving Pot-2 for long slow cooking; making curry or simmering milk
- The stove is simple to construct and maintain. It can be made and maintained by the cook herself, once she has been taught by a trained field-worker
- The floor of the fire-box has been designed with a slope for easy removal of ashes
- The space below the chimney-pipe inlet is accessible through the second pot-hole, for removal of deposits from the chimney-pipe.
 Figure 1: Schematic drawings of stove (cm) |
Pure clay from a pond is mixed with silt-free sand with a particle size of 1-4mm, in the ratio 1:3 to 1:5, depending on the 'oiliness' of the clay. Alternatively, sub-soil (not topsoil) with 50% clay can be used. For durability, and to inhibit cracks which develop during the drying process, the addition of fibrous material such as rice husks or wheat husks and dung is advisable.
The mixture must be wetted and kneaded well and formed into a stiff paste before casting into a block. To ensure durability of the stove structure, the mixture should be tested by making brick-sized test pieces and drying them in the shade. If the surface of the test piece does not develop cracks, the mixture is suitable for making the stove.
[top] [end]Method of construction - Cast the mixture in the form of a block measuring 90cm × 45cm × 35cm along the wall of the kitchen. To improve the front elevation of the stove, the floor area below it may be raised by 8-10cm using bricks and mud-mortar and the block can be cast on to it.
- Allow the block to lose some of its moisture for a couple of hours so that the structure does not slump while working on it with a trowel. Mark out the outline of the stove and scribe circles for the positions of pot-1, pot-2 and the chimney-pipe support, as shown in Figure 1.
- Cut out material from the block using a trowel or a long knife to form the fire-box; cut away holes for Pot-1, Pot-2, the tunnels and the fire-box opening, as shown in Figure 1 front view and side view. Insert pottery liners into the tunnel holes.
- Shape the outside of the block to give it a smoother rounded shape, as shown in Figure 1. A shrinkage allowance of about l-2cm should be left on all the finished surfaces to allow for shrinkage as the stove dries.
- Allow the structure to dry and gain strength before fixing the chimney pipe, using the method illustrated in Figure 3.
 Figure 2: Completed stove |
[top] [end]Fixing the chimney-pipe The minimum length of chimney pipe should be two metres, and it can be longer if it goes into a high roof. It the pipe is of metal or asbestos cement, it may be better to make it using two pieces, to facilitate cleaning. The upper part of the chimney can be clipped with a wall bracket and sealed to the roof, projecting at least 60cm above the roof. This will reduce the risk of sparks from the fire alighting on the thatched roof. Its free end should not be close to any wall or structure which could hinder the free flow of air around it. This will help to pre- vent a back-draught in the chimney-pipe. The free end of the pipe should be covered with a conical cowl to prevent rainwater entry and the effects of wind.
The lower half of the chimney-pipe is supported on the pipe socket, which is fixed to the stove body and serves as a chimney inlet. It is joined to the upper half by a metallic ring or a specially designed pottery sleeve, The sleeve permits easy separation of the two halves for cleaning the pipes from inside, without disturbing the seal between the upper half of the pipe and the roof.
Alternatively, pottery pipe lengths of 60cm each, with a slip-in socket can be used to make up the total length of the chimney pipe. The pottery pipe length passing through the roof should, however, be fixed and sealed, such that cleaning can be undertaken without disturbing the sealing between the pipe and the roof. Figure 3 shows the technique for fixing the chimney pipe to the roof.
 Figure 3: Chimney fixing technique |
 Figure 4: Cooking stove in use |
The improved cooking stove (Figure 4) has been tested in the field with positive feedback from users. If constructed and maintained as described, and used at the burning rate for which it has been designed, a significant fuel-saving and reduction in smoke can be attained.
[top] [end]Contents: Boiling Point 41: Household energy: the urban dimension  . |
Urban energy - a rapidly expanding issue - A place to feel at home - A social perspective on the family hearth in Africa - Urban Energy - practical and theoretical issues - Development of stoves for cooking and heating in China - The household energy market in urban Mali - What ever happened to kerosene as a cooking fuel - some experiences from Haiti - Energy issues in the small-scale industry sector in Dakar - Urban consumption of biomass energy in Morocco - Energy options for urban households in India - Biobriquettes - a competitive fuel for cooking - Household energy isnt all stoves - Mirte stoves in Ethiopia - An improved cooking stove for farming families
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