Faculty of Agriculture, Engineering and Natural Sciences

Permanent URI for this community

http://hdl.handle.net/11070/3304

Browse

Now showing 1 - 4 of 4

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
Hydrogen purity assessment using laser absorption Spectroscopy
(University of Namibia, 2025) Shilongo, Rosamunde P.; Chiguvare, Zivayi
Hydrogen purity assessment is a critical concern in energy applications, especially in fields involving hydrogen injection into natural gas pipelines and fuel cell research. This study addresses the limitations of current hydrogen measurement techniques by developing a novel hydrogen spectrometer (𝐻2-Spectrometer) based on direct Tunable Diode Laser Absorption Spectroscopy (d-TDLAS). The goal is to establish a traceable and accurate methodology for hydrogen purity and concentration measurement without relying on calibration gases. The main objective of this research is to develop and evaluate the performance of the 𝐻2-Spectrometer, specifically investigating its suitability for measuring hydrogen purity and hydrogen concentration in methane hydrogen mixtures. The study also aims to support hydrogen injection into natural gas pipelines by providing precise hydrogen concentration measurements. An experimental design was employed, utilizing the 𝐻2-Spectrometer to measure hydrogen line intensity and concentration. The measurements were taken for 99.999% pure hydrogen and hydrogen-methane gas mixtures to test the spectrometer’s accuracy and reliability. The obtained data were compared against reference values from the HITRAN database and the certificate from the reference gas mix to evaluate performance. The findings revealed that the 𝐻2-Spectrometer demonstrated a significantly lower uncertainty of 1.6% in hydrogen line intensity measurements, compared to the 10% uncertainty reported in the HITRAN database. The measured line intensity obtained was 3.22 × 10−26 cm/molecule, which is slightly higher than the HITRAN value of 3.189 × 10−26 cm/molecule. In terms of hydrogen concentration, the spectrometer achieved an average mole fraction of 0.858 with a 1% uncertainty, closely aligning with the expected value of 0.900 as per the certificate from the reference gas mix with a 2% uncertainty. The 𝐻2 Spectrometer proved to be highly accurate and reliable, with potential applications in hydrogen quality control from electrolysis, fuel cell research, process control, and environmental monitoring. Its ability to provide traceable and precise measurements makes it a valuable tool for hydrogen-related research, optimizing system performance and ensuring compliance with regulatory standards
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
Viability of substitution of electricity with biogas for thermal uses at Neudamm campus of the University of Namibia
(University of Namibia, 2025) Tomas, Pineas Panduleni; Chiguvare, Zivayi
The growing demand for sustainable and affordable energy solutions in rural areas has led to increased interest in biogas technology, particularly in developing regions. This thesis presents the design and evaluation of a low-cost biogas digester for the Neudamm Campus of the University of Namibia. The study adresses the campus's energy cost and the underutilisation of livestock manure as a renewable energy resource. A 100 L digester, constructed from locally available materials, was fed with a cow manure-water slurry and operated over a 60-day period. Key operational parameters included an estimated 30-day hydraulic retention time, with pressure monitored three times daily in the first week, twice daily from Days 8–21, and once daily thereafter.. The digester achieved an average daily biogas yield of 0.95 L, equivalent to 7.61 MJ (2.11 kWh). Based on manure availability at Neudamm (22.2 tonnes/day), the system could theoretically produce 318.76 L/day of biogas. This represents a payback period of 2.5 years and an estimated 594% return on investment over a 10-year lifespan. The gas produced was sufficient to substitute part of the campus’s electricity demand for cooking and water heating, demonstrating both economic and environmental benefits, including reduced greenhouse gas emissions and nutrient-rich slurry for fertilizer. The study acknowledges limitations such as short monitoring duration, reliance on pressure as the sole gas measurement, and minor leakage issues. ii Despite these constraints, the study demonstrates the feasibility of low-cost, small scale digesters in Namibia and provides a replicable model for rural settings. The findings contribute to renewable energy knowledge in Southern Africa and highlight practical opportunities for integrating biogas into campus and farm operations

Browse

Browsing Faculty of Agriculture, Engineering and Natural Sciences by Advisor "Chiguvare, Zivayi"

Results Per Page

Sort Options