MST-Department of Energy Engineering

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Browsing MST-Department of Energy Engineering by Author "Okwach, Silvester"

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    Enhancing efficiency of biomass carbonization for high Quality and quantity charcoal production by using Metallic clay insulated kiln
    (Kenyatta University, 2014) Mulei, Fredrick Mwange; Laichena, Justus K.; Okwach, Silvester
    The main objective of this study was to construct a metallic clay insulated kiln to enhance charcoal yield in quality and quantity. This research project aims at improving the charcoal quality in terms of calorific value and smoke - free, and maximum yield of charcoal (per kilogram of biomass substrate loaded). The quantity of charcoal harvested per kilogram of primary four biomass materials loaded as substrates was determined in four tests in each substrate. The main objective was to develop metallic clay insulated kiln with high efficiency, economical and environmentally friendly. metallic clay insulated kiln would offer solution to the problems of low efficiencies of existing charcoal kilns, for example, Traditional Earth Mould Kiln, Mark V. Kiln, Beehive kiln, and Half Orange kiln, among others. These kilns have efficiency of 10%, 31%, 32% and 28.8%, respectively, compared to the achieved 40.85 ± 5.04 % for this metallic clay insulated kiln. In this research a metallic clay insulated kiln was constructed and tested. The major aspect is that a proto type 0.15 m' drum was used to provide feedstock housing. This was tightly covered such that no fraction of feedstock was burned to provide carbonization heat. Clay insulation housing was constructed while the drum was provided with metallic stands and each of the substrates was loaded in the drum. Insulation wall made of clay/mud was constructed to prevent heat loss from the drums and combustion area. The quantity of charcoal produced from the metallic clay insulated kiln was compared with the quantity of wood substrate used. To determine the quality of the charcoal (in terms of calorific value and smoke), universal standard charcoal testing method was used that is Water Boiling test. The quality of charcoal produced from the kiln was then compared with charcoal produced from other different existing kilns in the literature. The data analysis was done by the help of statistical package for social science (SPSS) and Microsoft Excel. In conclusion, efficiency of charcoal production should be emphasized so as to make the practice of charcoal production sustainable by use of metallic clay insulated kiln. It was also found that metallic clay insulated improved kiln had higher efficiency (40.85 ± 5.04 %) than existing kilns such as Beehive, Mark V, Half Orange, Traditional Earth Mould, drum kilns adopted by FAO and others. Adoption! utilization of the metallic clay insulated kiln (with high efficiency as obtained in this research project (40.85 ± 5.04 %)) will reduce/cut-off the problems experienced in use of the _existing low - efficiency kilns. It is both an economical benefit, and environmental friendly. Charcoal production using improved charcoal kilns with high efficiency would give much higher yields of charcoal of excellent quality (in sense of HHV and smoke-free). This can make the practice very profitable, and users will have motivation for sustainable production of charcoal.
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    Performance of a Double Reflector Solar Box Cooker with Phase Change Material Energy Storage
    (2014-02-19) Mwaura, Margaret Muria; Thoruwa, T. F. N.; Okwach, Silvester
    The use of solar energy for cooking offers an alternative source of energy to the high cost of petroleum products and the diminishing wood fuel products for cooking and heating applications. An effective solar cooker is the one that can be used throughout the day and in the evening when there is no sunshine. Most areas in Kenya can be considered as a high potential solar energy area because Kenya is located on the equator. Most of the solar cooker designs do not have thermal storage systems and can be used for cooking when there is sunshine and cannot be used during cloudy weather or in the evening. The aim of this study was to design and assess the performance of a double reflector solar box cooker with an energy storage unit. The use of phase change materials (PCMs) as a technique of storing energy was used to overcome the time mismatch between solar availability and demand. The PCM used in this study is acetanilide with a melting point ranging from 113 to 116 °C. The box cooker was designed so that the length to width ratio for the reflector and the glass window was 4:1. This eliminated the azimuth tracking towards the sun. Three sets of experiments were carried out, one without loading the cooking pot of the cooker, one with water as the cooking load and one with different actual cooking loads in the School of Engineering and Technology Demonstration Center, Kenyatta University. The measured parameters included, the solar radiation, ambient air temperature, temperatures of the different components of the solar cooker, load temperature and wind speed. The data values were read and recorded by use of a data logger at regular intervals of 10 minutes. Data analysis was done using statistical measures. An average stagnation temperature of 85.9 ± 24.0 °C and 82.7 ± 24.3 °C was achieved in the two pots. The average solar radiation was 637.1 ± 212.0 W/m2. The cooking power tests achieved a coefficient of performance of 0.754. The results showed that the double reflector solar cooker with energy storage can be used to cook meals throughout the day and in the evening. Noon cooking does not affect evening cooking. The adoption of this study will be beneficial to Kenyans as it will increase the acceptability of the solar cookers hence reduce the consumption of wood fuel and petroleum products. This will reduce the rate of depletion of wood resources, save time and reduce expenses for the user which could be diverted to increased productivity and monetary gains thus raising the living standards and a clean environment devoid of hazardous emissions associated with wood and fossil fuel combustion.