Bibliography: leaves 154-160. / 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.

Kinetic data on soot and pyrolytic graphite oxidation rates have been used to calculate the ability of woodstove catalysts to burn woodstove effluent particles. Large variations appear in the literature and depending upon which particle diameter and rates were used one can calculate maximum possible particle oxidation efficiencies of 10⁻¹ to 40 per cent, with most investigators predicting less than a 1 per cent efficiency. This suggests that the 80 per cent reduction in "particulate" emissions which is shown by tests with catalyst-equipped stoves is due to catalytic oxidation of high molecular weight vapors rather than due to particle burnup. Dilute (500 and 250 ppm) acetylene/air mixtures flowing between parallel catalytic plates have been studied experimentally. Measured acetylene profiles for the hydrodynamic entry length region are presented and compared to profiles calculated by a single-phase, two-dimensional, low mass transfer analytical model currently under development and which eventually will be extended to cover three-dimensional flows such as those in the passageways of a woodstove catalyst. The measured temperature profile for a 5000 ppm acetylene/air mixture flowing between parallel catalytic plates was compared to the temperature profile calculated by a single step, adiabatic, constant pressure, homogeneous model. / Master of Science

Thesis (M.A.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 277-290.

Thesis (M.Soc.Sc.) - University of KwaZulu-Natal, Pietermarizburg, 2009. / Full text also available online. Scroll down for electronic link.

The use of biomass as a renewable fuel source can help the United States reduce its dependence on fossil fuels, especially in providing affordable heat for many middle- and low-income households. However, residential wood combustion (RWC) releases pollutants that can negatively impact the environment and human health, especially for those living in the vicinity of wood-burning locations. Current compliance testing methods are insufficient in capturing the actual in-use emissions of residential wood heaters because they do not represent real-life use, leading to higher emissions during actual use. This thesis investigates emissions during realistic operations of wood-fired heaters to identify and quantify the majority of emissions and ways to minimize such emissions. The study focuses on investigating eight different woody biomass fired heaters, including three pellet stoves, a pellet boiler, two wood chip-fired hydronic heaters, and two outdoor cordwood fired hydronic heaters. This research contributes a new knowledge on the impact of combustion strategies, fuel type, and control strategies to minimize emissions. The obtained data can provide information to manufacturers, policy makers, and consumers, guiding low-emission and more efficient use of wood-fired heating devices. In all chapters, variability was evident due to burn phase, fuel type, and operation. The results from the pellet stoves showed that even while using a homogeneous fuel, different burn phases produce different emissions than the overall period. For the pellet boiler studies, the highest efficiencies were achieved during the high load, steady state tests. The burn phase also affects emissions from woodchip boilers, where low output periods are significantly higher in terms of emissions compared to high output periods. Each individual burn phase of the duty cycle produced different emissions in cordwood testing, with steady-state phases having the lowest emissions and highest efficiency. The variability in emissions from different burn phases is a crucial factor in evaluating the performance of wood-burning appliances. Lower moisture content fuels were found to have better performance in terms of PM emissions and efficiency. Fuel type can impact emissions, but it may be overshadowed by burn phase and technology. Relatively high emissions were often related to low or incorrect air-to-fuel ratios. Gasification techniques used in some woodchip boilers during low output periods significantly increased efficiency and reduced CO emissions. Additionally, gasification techniques used during high burn steady states with wet fuel chips resulted in a 77% reduction in PM emissions. Comparing all the primary heaters studied in this thesis, in terms of PM emission output, showed the units that used gasification, integrated catalysts, or thermal storage had the lowest emissions. The results of the study are compiled into data sets that give a more accurate picture of real-world operation of wood-fired heaters that will benefit air quality modelers and policy makers. Such emission data for various biomass heaters in EPA’s AP-42, under realistic operating conditions, currently either does not exist or is limited. Additionally, this research identifies the most important parameters that need to be included in the development of high-resolution models, optimizing the performance of wood-fired devices and supporting the transition from current compliance testing to more realistic testing. In conclusion, this work provides new insights into the performance and emissions of wood-fired heaters during realistic operation. The results of the study can help manufacturers optimize their products for real-life performance and help policy makers and consumers make informed decisions regarding low-emission and more efficient use of wood-fired heating devices. The study highlights the importance of capturing transient phases and the impact of fuel type and control strategies on minimizing emissions.

Persistent poverty, social and economic inequalities are some of the challenges in the process of national development efforts targeted in the United Nations Millennium Development Goals (MDGs). Yet in South Africa, poverty, hunger, social and economic inequalities are still on the increase especially among poor rural to urban migrants. Because of severe poverty in rural areas, large populations of rural poor migrate to urban areas in search of better life. However, the growing energy needs in the urban areas where these people settle and their use of inefficient energy technologies negatively impact on the balance of environmental resources on which their socio-economic development depends. Efficient, affordable and environmental friendly technologies are therefore vital for improving the livelihood conditions and protecting the much needed environmental resources of the country. On the contrary, current practices presently dominating energy provision issues in South Africa are insufficient to solve the problems of socio-economic inequalities, especially for the increasing urban poor population. In addition, they are also failing to protect the environment and natural resources. Electrification of poor urban and peri-urban areas by both grid and off-grid systems through the top-down development practice is doing very little to change the socio-economic conditions of the poor section of the population in the country. Likewise, the provision of modern energy through public sector agencies such as Eskom is inadequate and inappropriate for the rapidly expanding urban and peri-urban poor areas in the country. One major reason that hinders provision of such services to the overcrowded consumer population in these areas is the massive capital investment required and inability to pay electricity bills by urban poor households. Against the above background, this study examined the use of improved wood stoves in two peri-urban areas (Umsilinga and Isnathing) in Pietermaritzburg, South Africa as an alternative modern energy technology on how they would socio-economically benefit the peri-urban poor. It looked at the following: The efficiency of four improved wood stoves (Yamampera, Simunye, Household Rocket and Vesto) in comparison with the three stone open fire, The impact of the efficient burning of the four improved stoves, Factors influencing consumers in choosing a specific energy technology to use, The effectiveness of the improved wood stoves placed in 24 peri-urban households and observed for the specified period, and Additional potentials of such stoves to other prospective users. The key finding of this research is that the use of these improved wood stoves could play a pivital role in household economic growth and improving livelihoods. Participants ranked smokeless burning, low selling price, fuelwood saving and light weight of the stoves as priority preferences for using these stoves. Speed of cooking and less constant attention to the fire were also ranked as important preferences. From women participants view point, the low selling price of the stoves and their considerable fuel saving would reduce strain on the household investment capital, household indoor pollution and tedious work of women’s fuelwood collection. Low investment costs in acquiring the stoves would encourage women’s participation as entrepreneurs in modern energy technologies. However, results from focused group discussions and observations of usage of stoves that were placed in 24 homes showed that the incorporation of consumer preferences in the design of improved wood stoves would be key. This would enable stoves to adequately meet the energy needs of targeted users and be used frequently as an alternative energy solution by both urban and peri-urban poor who are currently lacking electricity and suffering from energy poverty. / Thesis (M.Soc.Sc.)-University of KwaZulu-Natal, Pietermarizburg, 2009.