Advances in Science and Technology Vol. 160

Abstract: In this study, a single-cell, zero-gap, unipolar alkaline water electrolyzer which operates on a 30 wt.% KOH electrolyte solution was developed for production of hydrogen. Suitable material properties such as density, toughness, electrical conductivity, and corrosion resistivity were evaluated in Ansys Granta 2019 with the aid of material property charts; and thermal and stress simulations of the modelled components performed using Autodesk Inventor Nastran 2019. A DC power source supplied voltages below 3.0 V across the nickel electrodes, maintaining an operating temperature of 50 °C, and operating pressure at 0.1 MPa. The electrolytic process produced hydrogen and oxygen gases at the electrodes, and the membrane performed the gas separation. Polytetrafluoroethylene plastic was experimentally found to be a superior and more suitable material for the electrolyzer endplates and spacers to polypropylene plastic. Polypropylene nonwoven geotextile fabric was also found to be a low-cost and efficient membrane material, against Zirfon Perl UTP 500 membrane which is an efficient but expensive industrial membrane; polyester geotextile fabric got corroded after about 24 hours of good service. The optimal performance of the electrolyzer cell was obtained at a cell voltage of 2.2 V and a current of 1.30 A, while producing 14 ml of hydrogen gas per minute. This performance gave an electrolysis efficiency of 55.6%, an energy efficiency of 67.3%, and a hydrogen production efficiency of 75.4%. The produced hydrogen and oxygen gases generated electrical energy in a reversible PEM fuel cell device which powered a 0.2 W DC electric motor for a minute.

Abstract: In this study, a supercritical metal-water reactor for hydrogen production was designed, simulated, and analysed. As the world urgently seeks to transition towards sustainable energy, hydrogen stands out as a pivotal solution in this shift. This project aims to fill knowledge gaps related to the transition to supercritical conditions through comprehensive analysis, thereby contributing to the advancement of clean energy technologies. Mechanical and thermal properties suitable for a supercritical metal-water reactor were modelled and simulated in SolidWorks 2022, utilizing plots and mesh results. The reactor was designed to produce hydrogen gas and metal oxide as by-products, with the hydrogen gas being released through a pressure relief valve. The reactor cylinder, made of Ti-6AL-4V, was found suitable for operation at a constant pressure of 25 MPa and a temperature of 380°C. The reactor wall was observed to buckle at pressures exceeding 27 MPa and temperatures above 144,000°C, which are beyond the design conditions. The elastic limit of the cylinder was determined to be 868 MPa, and its ultimate tensile strength was 1,258 MPa, with fracture occurring at 620 MPa. The average damage percentage was calculated to be 0.001%, and the total lifecycle was estimated at 10,000,000 cycles. The integrity of the reactor designed for supercritical states was found to be structurally sound. Detailed insights into the effects of pressure and temperature on the selected material were analysed, enhancing understanding of the reactor's performance under various conditions.

Abstract: In this study, a two-parameter computational thermodynamic analysis of a hydrogen-impurity mixture in a repurposed pipeline was performed. The hydrogen purity is a vital aspect of the hydrogen value chain, and it is essential to constantly monitor its purity. We anticipate that refineries will use repurposed pipelines for bulk hydrogen transportation to consumers; however, these pipelines are known to contain impurities. Therefore, there is a need for such an analysis. This study considered two basic thermodynamic parameters: the pressure and gas molar concentration. The Peng–Robinson equation of state was used for the analysis. We implemented octave programming for the Newton-Raphson numerical scheme to obtain the molar volume of the pure hydrogen. Four scenarios were considered: scenario 1 (only hydrogen), scenario 2 (hydrogen mix with H₂S), and scenario 3 (hydrogen mix with H₂S, and pentane), and scenario 4 (hydrogen mix with H₂S, pentane, and propane). We studied the variation in gas pressure with molar concentration. The results showed that, as the number of impurities considered in the analysis increased, the pressure decreased. The pressure of scenario 1 and 2 is approximately Pa, scenario 3 is around Pa, and scenario 4 is around Pa. We can develop a non-destructive acoustic emission hydrogen quality monitoring system by considering how impurities in hydrogen moving through a repurposed pipeline might affect the pressure of the gas moving through the pipeline.

Abstract: Natural rocks are emerging as a viable solution for solar heat storage in Sub-Saharan Africa due to their low cost and accessibility, as well as their ability to reduce energy costs and reliance on solar energy. This study review research on applications of natural rocks as heat-storage materials for food drying in Sub-Saharan Africa. Findings of this study indicate that current research on the combination of drying systems with thermal energy storage systems using natural rocks as storage material focuses on indirect solar dryers (66.67%), mixed mode solar dryers (16.67%), and solar-assisted heat pump dryers (16.67%). These dryers perform admirably, particularly in extreme weather conditions and when there is no sunlight. The findings show that using natural rocks as a storage medium can increase the efficiency of dryers by up to 17.48%, reduce drying time by as much as 50%, and extend the drying operation by 2 to 4 hours after sunset. This study also identifies and proposes key areas for further research. In particular, more attention is needed to characterize the thermal properties of the storage materials used, as this aspect is often underexplored in African studies. Understanding these properties is essential for optimizing the performance of solar dryers and making informed choices about which materials to use. In addition, the techno-economic analysis of all these dryers is neglected, making it difficult to assess the economic impacts of these technologies and facilitate their adoption in communities. Exergoeconomic analysis should also be carried out in order to facilitate optimization and understand the actual efficiency of these dryers.

Abstract: This study explores the integration of thermoelectric generators (TEGs) and phase change materials (PCMs) to enhance the efficiency of photovoltaic (PV) panels in high-temperature conditions. An AP-PM-20 Polycrystalline PV panel, SP-1848-27145 Bismuth Telluride TEG, and paraffin wax PCM in an aluminum container were used. Four configurations were tested: standalone PV, PV-PCM, PV-TEG-PCM, and PV-PCM-TEG, under identical conditions from 10:30 AM to 6:00 PM at 25-minute intervals. Data on PV and TEG voltage, current, and solar irradiance were collected and analyzed. The results show significant performance improvements: the PV-PCM configuration achieved a 68.04% increase in power generation, while the PV-PCM-TEG and PV-TEG-PCM setups recorded efficiency gains of 43.06% and 37.51%, respectively. Efficiency gains relative to the standalone PV system were 33.33% for PV-PCM, 25.76% for PV-PCM-TEG, and 21.21% for PV-TEG-PCM. The results demonstrate that integrating TEG and PCM technologies significantly enhances solar PV performance and offers promising solutions for optimizing solar energy systems in real-world conditions.

Abstract: Poor storage conditions, particularly exposure to extreme temperatures, can significantly compromise vaccine efficacy, making them ineffective or harmful. This highlights the urgent need for adequate storage infrastructure and monitoring systems, especially in remote areas with limited healthcare resources. This study evaluates the performance of a locally-made solar-powered cooler designed for vaccine storage in such environments. A digital AKO thermostat was integrated to control the compressor according to specified temperature limits, alongside a data logger for continuous temperature monitoring and a fluke device for DC and voltage measurements. The experimental results, validated against existing literature, were reliable and accurate. Key findings reveal that the cooler can reduce temperature to -14.9°C within 180 minutes, surpassing the performance of previous models that attained a temperature of -10°C after 144 minutes. The optimal insulation thickness for maintaining a cooling temperature of -15°C was determined to be 0.07 m using polyurethane insulation material, compared to 0.129 m with Feather Fiber, reflecting a 45.7% increase in efficiency at an ambient temperature of 42°C. Similar results were observed at an ambient temperature of 32°C. Modeling outcomes provided valuable guidance for the experimental design and comparative analysis.

Abstract: Malawi is among the Sub-Saharan African countries with abundant solar energy resources, mainly used for electrification, water pumping, and domestic water heating in rural and urban communities. More than 85% of Malawi’s population is based in remote rural areas, where the majority depend on untreated water that can compromise their health. This study aimed to design an improved Solar Disinfection (SODIS) system for microbial disinfection of harvested rainwater at rural healthcare facilities in Malawi, supplementing the United Nations’ efforts to accelerate SDG 6 through SDG 7. The results accomplished the 0 MPN/100 ml E. coli and 0 MPN/100 ml Total coliform water disinfection using solar UV radiation. Despite the focus on clean water for sanitation and hygiene in maternal healthcare facilities, the study achieved the water quality recommended by the World Health Organization’s and Malawi Bureau of Standards’ drinking water requirements.

Abstract: The integration of photovoltaic systems into energy grids has been very common in recent times since more renewable forms of energy are sought after. Reliability and safety are among the most essential concerns that have to be considered for the deployment and operation of such systems. There have been some very conspicuous failures of protective devices in recent installations, leading to huge damage to solar equipment and an estimation of millions of Naira in repair and maintenance costs. The said incidents further underscore the need for technical competency in PV system installations as well as good-quality protective component acquisition. This study examines the critical role of protective devices in photovoltaic (PV) systems, focusing on their impact on system reliability, operational safety, and financial implications. A survey of industry professionals revealed that the major causes of device failures are overvoltage and poor-quality devices. Similarly, Circuit Breakers and Surge Protectors top the list of devices affected by failures. Critical system shutdowns take up 50% of the resultant consequences of failures, deteriorated performance, and safety hazards. Surprisingly, 65% of those who responded reported financial losses due to the failures, estimated at 45% between N100,000 and N500,000, while 15% had losses above N500,000. The study recommends high-quality protective devices be installed, installation and maintenance be standardized, and predictive maintenance/remote monitoring technologies be adopted to improve reliability and early fault detection. The long-term performance of devices in varying environmental conditions and the economic benefit of using durable, high-quality components are to be focused on further for research. These findings also put forward actionable suggestions to better ensure the PV system resilience for all stakeholders, thereby reducing their financial risks and ensuring the continued growth of the solar energy infrastructure in a reliable manner.

Abstract: This paper presents an indicator-based framework for the sustainability analysis of mini-grids and applies this to a selection of mini-grids in Kenya. Although various frameworks exist, they have been criticised for lack of attention to long-term perspectives, high data needs, prescriptive nature of the attributes and limited user-friendliness. Considering that data availability is a major concern and that data available is qualitative in nature, this paper proposes a set of indicators and a scoring system that can be used with a broad qualitative understanding of the sustainability attributes of the mini-grids. The paper first presents the framework and the scoring system and applies this to the data gathered from the fieldwork in Kenya. The results indicate that the significant variation in sustainability performance of the mini-grids covered and the performance is relatively good in technical and economic dimensions and relatively poor in social, institutional and environmental dimensions.