Department of Environmental Sciences

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Browsing Department of Environmental Sciences by Advisor "Chiguvare, Zivayi"

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    Design and performance evaluation of an oil/rock bed heat storage system for solar cooking
    (University of Namibia, 2025) Naule, Cecilia N.; Chiguvare, Zivayi
    This thesis presents the development and performance evaluation of a sensible thermal energy storage system that used sunflower oil and rock pebbles as heat storage mediums. The aim was to assess the system's performance based on charge and discharge rates, energy storage capacity, power output, cooking efficiency, and cost-effectiveness. The main body of the system was created with an old hot water geyser. An Arduino-based data logger was fabricated and was used to monitor and capture temperature changes throughout system operation periods. The data was analyzed with Python programming, from which time-temperature graphs were drawn. The heat retention capacity was obtained by heating the system to about 200 °C and then cooling it, with the time taken to cool being recorded. The system took approximately 30 hours to cool from 194℃ to 60℃. The system generated 0.028 kW of power and stored a total of 0.85 𝑘𝑊ℎ of heat energy. The efficiency testing, which involved boiling five liters of water, yielded an average efficiency of 78.98%. The total cost of constructing the system was: N$ 3,860, with a unit energy cost of N$ 1.26/kJ and a unit power cost of N$ 137.86/W. The cooking test demonstrated that the system could simultaneously cook 300 g of rice in 43 minutes and 300 g of dry beans in about 4 hours using only the stored thermal energy. The study therefore concluded that the developed system was able to deliver a reliable and cost effective solution for domestic use. Nonetheless, constraints including insufficient funding for further development and a limited timescale, impeded comprehensive investigation of the system's capabilities. Future research needs to improve the design of the system as well as explore the possibility of using solar PV panels to heat the TES system
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    Influence of enclosure geometries and internal installations on the explosion pressure of hydrogen-air mixtures
    (University of Namibia, 2025) Uunona, Ndamononghenda N.; Chiguvare, Zivayi
    The use of green hydrogen gas as a clean energy carrier solution is gaining global momentum and Namibia is on track to being one of the major producers of green hydrogen. The growing emphasis on green hydrogen has elevated the importance of safety in its value chain. This thesis investigates the influence of enclosure geometries and internal installations on the explosion pressure of hydrogen-air mixtures within flameproof enclosures. The aim of this work is to investigate two critical aspects: the impact that different flameproof enclosure geometries have on the explosion pressure, and the role that internal installations play in exacerbating or mitigating the phenomenon of pressure piling. Experimental tests were conducted in the metrological laboratories of Physikalisch Technische Bundesanstalt, an Institute in the Federal Republic of Germany in compliance with the international standards, such as IEC 60079-1, in order to adhere to the safety guidelines which are vital for preserving structural integrity during hydrogen explosions. These experiments were conducted using specific enclosure geometries – spherical, cylindrical and multi-chambered enclosures. Different orifice sizes and welded internal installations were used to replicate the real-world industrial conditions of pressure piling. The results demonstrated that enclosures with complex geometric design and internal installations were more susceptible to pressure piling effects due to localised pressure compression and uneven pressure distribution. Additionally, this work highlighted the importance of the proper design of the enclosure, emphasizing the need for optimized internal configurations to minimize risks. The findings from these experiments contribute to enhancing and improving the design of flameproof enclosures, potentially informing future regulatory updates, promoting safer practices in hydrogen production plants, and ultimately, bridging the existing knowledge gaps in hydrogen explosion protection