Browsing by Author "Ogwang, Isaac"

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    Characterization of Biogas Digestate for Solid Biofuel Production in Uganda
    (Scientific African, 2021) Ogwang, Isaac; Kasedde, Hillary; Nabuuma, Betty; Kirabira, John Baptist; Lwanyaga, Joseph Ddumba
    In this study, suitability of digestate from anaerobic digestion of cow dung, pig dung, and human waste feedstock as a solid fuel for thermal applications was investigated. The digestate was obtained at different retention times from laboratory scale and household digesters and later characterized. Carbonized briquettes were produced from the digestate followed by their physico-chemical characterization and assessment for combustion and mechanical properties. Results of the proximate analysis of the digestate were: moisture content (6.1 to 18.3%), volatile matter (27.9 to 47.7%), ash (15.0 to 48.9%), and fixed carbon (9.1 to 17.1%). The ultimate analysis results for the digestate were: carbon (19.5%), hydrogen (3.3%), oxygen (20.8%), and nitrogen (7.0%). The developed briquettes showed a moisture content, volatile matter, ash, and fixed carbon in the range of 3.7 to 8.9%, 9.9 to 21.5%, 45.6 to 76.4%, and 8.2 to 22.8%, respectively. Their ultimate analysis results were: carbon (21.1%), hydrogen (1.3%), oxygen (1.8%), and nitrogen (1.9%). The briquette combustion properties revealed an ignition time, burning rate, and water boiling time of 5.35 seconds, 0.16 g/min, 31.1 minutes, respectively with higher and lower heating values of 14.87 and 7.88 MJ/kg, respectively. The briquette ash compounds were sodium 1718.5 ppm, potassium 20017.8 ppm, copper 6.12 ppm, cadmium 1.22 ppm, and lead 25.6 ppm. TGA/ DTG analysis indicated high mass loss rates at 105°C and maximum energy release between 600 and 900°C. The mechanical compressive strength was between 19 and 50 MPa, with bulk density between 1.82 and 2.02 g/cm3. Thus, the briquettes from the biogas digestate demonstrate potential for domestic thermal applications in Uganda.
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    Thermal Comfort in a Residential House in Kampala
    (Journal of Civil, Construction and Environmental Engineering, 2023) Wafula, Simon Peter; Kamulegeya, Obed; Kasumba Buyondo, Andrew; Mutebi, Solomon; Ogwang, Isaac; Mutambo, Michael; Kateu, James
    Global warming and climate change has been a challenge in the last decades. Buildings are major contributors to energy consumption. This is due to the rise in human comfort needs and services. The residential sector consumes a significant amount of energy worldwide. A NZEB strategy emphasizes closing the gap between energy demand and renewable energy supply. Despite some of the roles that NZEBs significantly contribute to smart cities on the energy efficiency, the potential contribution of NZEB to the residential sector of Uganda has not been documented in literature. The objective of this study was to develop a thermal comfort model in a residential house through an envelope design. CBE tool was used and results indicate; PMV with elevated air speed of residential houses during resting hours in Kampala; at night: -0.75. DBT as 24.1°C, PPD as 17%, the Cooling effect as 2.7°C and SET = 26.3°C. The study realized factors to be considered while building like; air temperature, average radiant temperature, air speed, air humidity. The model developed in this study enables a building to heat up during cold hours and cool down during hot hours by the help of the water pool collected during rainy days. This water cools down the house during the day time while absorbing heat that can be released during the night hours that are somehow cold in Kampala. However, if this isn’t considered, then heat pumps have to be employed to pump heat into rooms to reduce heating in rooms. Recommendations should be put in raising thick walls and ceilings to maintain building temperatures.