Browsing by Author "Baldwin, Susan Anne"

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    The development of low cost fuel-efficient woodburning stoves appropriate to underdeveloped areas of South Africa
    (1986) Baldwin, Susan Anne
    In light of the dependence of the majority of rural South Africans on fuelwood as their major energy source and the rapid diminution of this resource, the aims of this thesis were to investigate the design of a fuel-efficient woodburning stove, appropriate to and acceptable in the underdeveloped areas of South Africa, and to assess the potential for woodstoves in the mitigation of the fuelwood crisis and deforestation in these areas. This involved a review of international experience in stove development and dissemination from which the relative successes of differing designs and dissemination strategies were assessed. Stove design guidelines were also gleaned from the literature survey. Information on existing fuelwood usage and cooking patterns in the target areas was collected and incorporated in the design criteria for two prototypes. It was decided to develop light-weight metal prototypes that could be manufactured in minimally equipped rural workshops, since user constructed heavy-mass mud stoves were deemed to be inappropriate for warm climates and relatively short cooking times, and their dissemination was inhibited by hidden difficulties and costs. The two prototypes developed included a chimneyless bucket type (Onepot) which supported one, either three legged cast iron or flat bottomed aluminium, pot of maximum diameter 280 mm, and a chimney stove (Twopot) accommodating two cooking pots and one hot water container. Both stoves were lined on the inside with a 2 cm thick layer of vermiculite/firebrick mixture. These stoves underwent testing in a specifically equipped laboratory, to determine their efficiency versus power performance and to identify the main heat losses. At a nominal power input of 3 kW, the Onepot had an efficiency of 55% and at a nominal power input of 5 kW, the Twopot had an efficiency of 40%. The power range of both stoves was limiting, as the efficiency fell sharply with increasing power input. In the Twopot this was probably due to the under sizing of the grate area, as the combustion intensities on the grate were much less than those used in the design (37,5 W/ cm2 compared to 50 W/ cm2 ). A number of each prototype underwent field trials for six months in two rural villages in KwaZulu namely Biyela and Scheepersdal. In the assessment open discussions and interviews were held. It was found that the Onepot stoves were not used regularly because of their limitation of heating only one pot at a time. The Twopot stoves were more popular, however the main areas that still required attention were durability, incorporation of an oven and aesthetics of appearance. A theoretical model was developed and, for the Onepot stove, predicted that increasing insulation thickness would not result in significant increase in heat transferred to the pot in the burning rate ranges investigated. In conclusion, recommendations were made for re-design of the Twopot stove, mainly to increase durability and acceptability. It was felt that more work on combustion characteristics in the firebox was needed for better modelling of the stove. However, it was deemed that the greatest challenges for attaining the broader goals of this project lay with proving fuelwood savings in the field and devising successful dissemination strategies.