RP-Department of Physics

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Advances in Silicon–Carbon Composites Anodes Derived From Agro Wastes for Applications in Lithium-Ion Battery: A Review
(Heliyon, 2024-05) Adetomilola, Victoria Fafure; Bem, Daniel Barasa; Kahuthu, Stanley Wambugu; Adediran, Adeolu Adesoji; Bodunrin, Michael Oluwatosin; Abosede, Adefunke Fabuyide; Ajanaku, Christianah
Recently, the growing demand for high-performing batteries and different environmental challenges (such include global warming and climate change) have increased the requirement and demand for Lithium-ion batteries (LIBs) used in advanced technologies (i.e., electric cars and many others). To meet this increasing demand, there is an urgent need for more advanced technologies and materials. In the pursuit of developing anode materials, silicon has emerged as the utmost favourable choice for the next generation of LIBs, aiming to substitute the commonly used graphite. Carbon is commonly used to render silicon (Si) suitable for use since Si cannot be used directly as the electrode in LIBs. One of the recently discovered techniques in the development of high-performance LIBs is the use of inexpensive, sustainable, renewable, and ecofriendly materials. Agro-waste-derived silicon and carbon are often used as long as they don’t negatively affect the LIB anode’s performance. This review paper presents the advances in the development of silicon-carbon (Si/C) composite anodes sourced from agro-waste for applications in LIBs. It provides an overview of agro-waste-derived silicon-based anode materials and techniques for extracting silica from agricultural wastes. Next, the outline explains the preparation technique of Si/C composites obtained from agricultural residues for use in LIBs. Additionally, the paper delves into recent research challenges and the potential prospects of materials derived from agro-waste in the advancement of sophisticated LIBs battery materials.
Lateral distribution cosmic ray muon coincidences up to 36 m
(Elsevier, 2024) Kihagi, Veronicah N.; Chege, Samuel M.; Hashima, Nadir O.; Kimani, Naftali K.; Grupen, Claus
Primary cosmic ray particles comprise about 85 % protons, 12 % helium, 3 % iron, and heav ier elements. These particles interact with the Earth’s atmosphere, generating the Extensive Air Showers (EAS). Among the particles produced are pions and kaons, which decay into cosmic ray muons. In this research, the lateral distribution of cosmic ray muons was measured using two-fold coincidences. Four NaI (Tl) detectors and the associated electronics were used in the measure ments of cosmic ray muons. The detectors were positioned from 0 to 36 m at regular intervals. The muon count rate was observed to decrease as the distance between the detectors increased. The measurements were fitted to the Nishimura–Kamata–Greisen (NKG) function to analyze the lateral distribution. Monte Carlo (MC) simulations of EAS were performed using the Cosmic Ray Simulations for the KAscade Grande (CORSIKA) program. The simulations made use of EPOS and GHEISHA models for high and lower energies respectively. • The measurements for the two-fold coincidence are consistent with the NKG function. • The simulated and measured data were found to be in agreement. • The knowledge gained from the lateral distribution of cosmic ray muons is essential for the understanding of the development of extensive air showers
Performance Analysis of 600 Kwp Grid-Tied Rooftop Solar Photovoltaic Systems at Strathmore University in Kenya
(Results in Engineering, 2023-07) Ayora, Emmanuel; Munji, Mathew; Kaberere, Keren; Bundi, Thomas
Kenya boasts of abundant solar irradiation potential across its expansive regions, averaging between 4.5 kWh/m2 and 6 kWh/m2 per day. Despite this advantageous condition, solar energy's contribution to the national energy mix remains relatively low. To boost solar energy contribution to the national grid, it is crucial to assess the performance of existing grid-tied solar PV systems and develop strategies to improve their energy yields and further help in designing and installing new plants. This paper presents a technical performance analysis of a 600-kWp grid-tied solar PV system at Strathmore University, monitored over one year between January and December 2019. Economic and thermographic analysis of the solar PV system is done. The performance indices studied according to IEC 61724 standard include performance ratio, capacity utilization factor, reference yield, final yield, total collection losses, and total energy yield. This solar plant generated 735 MWh in 2019. The annual average monthly performance ratio, capacity factor, and annual specific energy yield were 57.4%, 13.97%, and 1225 kWh/kWp, respectively. The annual average monthly final yield, array yield, reference yield, and total system collection losses were 3.37 kWh/kWp, 4.49 kWh/kWp, 5.9 kWh/kWp, and 2.53 kWh/kWp, respectively. The thermographic analysis done shows that the system exhibits healthy temperature distribution. The economic analysis demonstrated Levelized Cost of Energy (LCOE) and simple payback period of US$ 0.143/kWh and 9.1 years respectively. The study reveals that the Strathmore system's performance is similar to other solar plants worldwide.
Assessment of Radioactivity Concentration for Building Materials Used in Babadogo Estate, Nairobi City County, Kenya
(Oxford, 2023-12) Oborah, Kenneth A.; Hashim, Nadir O.; Migwi, Charles M.; Rotich, Charles
Advancements in Energy Storage Technologies: A Review across Canada, USA, and Africa
(GJETA, 2024-01) Chidolue, Onyinyechukwu; Ngozichukwu, Bright; Ibekwe, Kenneth Ifeanyi; Ibekwe, Kenneth Ifeanyi; Fafure, Adetomilola Victoria; Daudu, Cosmas Dominic; Illojianya, Valentine Ikenna
This research explores recent advancements in energy storage technologies across Canada, the United States, and Africa, assessing their economic and environmental impacts. In Canada, the focus is on optimizing renewable integration and grid resilience. The United States witnesses growth in utility-scale projects, influencing grid reliability and fostering economic development. In Africa, off-grid and decentralized solutions address energy access challenges. The financial implications include job creation, industry growth, and cost savings, while environmental benefits range from reduced emissions to improved air quality. Future trends highlight technological advancements, integration with electric vehicles, and regulatory support. Collaborative efforts are essential for navigating these trends and unlocking the potential of energy storage in shaping a sustainable energy future.
Control Systems in Renewable Energy: A Review of Applications in Canada, USA, and Africa
(WJAETS, 2024-01) Chidolue, Onyinyechukwu; Daudu, Cosmas Dominic; Illojianya, Valentine Ikenna; Fafure, Adetomilola Victoria; Ibekwe, Kenneth Ifeanyi; Ngozichukwu, Bright
This research explores the applications of control systems in renewable energy across Canada, the United States, and Africa. It underscores their pivotal role in optimizing efficiency and reliability by examining supervisory, predictive, and adaptive control strategies. The literature review delves into global and regional renewable energy landscapes, emphasizing unique challenges and opportunities. Technological innovations, including advanced monitoring, artificial intelligence, and blockchain, are investigated, highlighting their transformative impact. The paper anticipates prospects such as quantum computing, decentralized systems, and heightened cybersecurity measures. The findings contribute to understanding the nuanced interplay between control systems and renewable energy, offering insights for policymakers, researchers, and industry stakeholders as they navigate the evolving landscape of sustainable energy solutions.
Sustainable Cooling Solutions for Electronics: A Comprehensive Review: Investigating the Latest Techniques and Materials, their Effectiveness in Mechanical Applications, and Associated Environmental Benefits
(WJARR, 2024-01) Ohenhen, Peter Efosa; Chidolue, Onyinyechukwu; Umoh, Aniekan Akpan; Ngozichukwu, Bright; Fafure, Adetomilola Victoria; Ilojianya, Valentine Ikenna; Ibekwe, Kenneth Ifeanyi
This study presents a comprehensive review of the latest techniques and materials in sustainable cooling solutions for electronic systems, focusing on their effectiveness in mechanical applications and associated environmental benefits. The primary aim is to assess the current state and future prospects of sustainable cooling technologies, highlighting their role in addressing thermal management challenges while minimizing environmental impacts. The methodology adopted is a systematic literature review, drawing data from peer-reviewed academic journals, conference proceedings, and industry reports. The search strategy involved keyword searches, database filtering, and reference tracking, with a focus on recent advancements in cooling technologies and their environmental implications. Key findings reveal a significant shift from traditional cooling methods to innovative, environmentally friendly solutions. Advanced materials like phase-change materials and nanotechnology-based heat sinks, along with techniques such as liquid cooling and thermoelectric cooling, have emerged as effective solutions. These technologies offer improved thermal management, reduced carbon footprints, and enhanced resource efficiency. The future landscape of sustainable electronic cooling is expected to be shaped by smart technologies, new materials with superior thermal properties, and the integration of renewable energy sources. The study concludes with strategic recommendations for industry stakeholders and policymakers, emphasizing the need for fostering innovation, promoting green cooling solutions, and setting stringent environmental standards. Future research directions include exploring new materials and technologies, integrating cooling systems with renewable energy, and conducting lifecycle analyses to understand the environmental impact of these technologies fully. This study underscores the critical role of sustainable cooling technologies in achieving environmental sustainability in electronic systems.
Microgrid Systems in U.S. Energy Infrastructure: A Comprehensive Review: Exploring Decentralized Energy Solutions, Their Benefits, and Challenges in Regional Implementation
(WJARR, 2024-01) Ibekwe, Kenneth Ifeanyi; Ohenhen, Peter Efosa; Chidolue, Onyinyechukwu; Umoh, Aniekan Akpan; Ngozichukwu, Bright; Ilojianya, Valentine Ikenna; Fafure, Adetomilola Victoria
This study presents a comprehensive review of microgrid systems within the U.S. energy infrastructure, focusing on decentralized energy solutions and their regional implementation. The primary objective is to explore the evolution, current state, and future prospects of microgrid technologies, assessing their technological, economic, and environmental impacts on regional energy infrastructures. Employing a systematic literature review methodology, the study synthesizes data from peer-reviewed journals, industry reports, and government publications. The search strategy involved keyword searches and manual screening, adhering to strict inclusion and exclusion criteria to ensure relevance and contemporary significance. Key findings reveal that microgrids are instrumental in enhancing energy security, integrating renewable energy sources, and providing economic benefits through decentralized solutions. Technological advancements in microgrid components and control systems have significantly improved efficiency and adaptability. However, challenges such as regulatory hurdles, technological integration, and financial constraints persist. The study concludes that microgrids represent a transformative solution for the future of energy systems, balancing reliability, sustainability, and economic viability. Strategic recommendations for industry and policymakers include developing clear regulatory frameworks, investing in advanced storage solutions, and incentivizing renewable energy integration. Future research directions emphasize enhancing microgrid interoperability with traditional grids, developing robust cybersecurity measures, and exploring innovative business models. In summary, microgrids stand at the forefront of revolutionizing the energy sector, offering a path towards a more resilient, sustainable, and equitable energy future, with ongoing advancements shaping the energy systems of tomorrow.
Decarbonization Strategies in Energy-Intensive Industries: Cases from Canada, USA, and Africa
(IJSRA, 2024-01) Chidolue, Onyinyechukwu; Ngozichukwu, Bright; Ibekwe, Kenneth Ifeanyi; Fafure, Adetomilola Victoria; Daudu, Cosmas Dominic
This research paper delves into "Decarbonization Strategies in Energy-Intensive Industries: Cases from Canada, the United States, and Africa." Against escalating global concerns about climate change, energy-intensive industries stand at the forefront of environmental impact, necessitating urgent and effective decarbonization measures. Through a comprehensive analysis, this study aims to unravel the diverse strategies employed in three distinct regions—Canada, the United States, and Africa—each marked by unique economic, social, and environmental contexts. The exploration begins with an in-depth examination of the current landscape of decarbonization strategies, encompassing technological innovations, policy and regulatory frameworks, and market-based approaches. A comparative analysis uncovers commonalities and distinct challenges across the selected regions, shedding light on the nuanced dynamics of sustainable industrial development. Barriers such as economic viability, technological adoption challenges, and socioeconomic impacts are scrutinized alongside enablers like government leadership, technological innovation, and sustainable finance. The paper outlines prospects for decarbonization, envisioning advancements in green technologies, the integration of circular economy principles, and the evolution of resilient energy systems. Grounded in these prospects, strategic recommendations are proposed, emphasizing the need for holistic policy frameworks, publicprivate collaboration, incentivizing sustainable finance, investing in research and development, and embracing a just transition approach. In conclusion, this research contributes a holistic understanding of the complex interplay between strategies, challenges, and prospects in the pursuit of decarbonization in energy-intensive industries. The insights garnered provide a blueprint for policymakers, industry leaders, and stakeholders to navigate the intricate path toward a sustainable and resilient industrial future.
Green Data Centers: Sustainable Practices For Energy-Efficient It Infrastructure
(ESTJ, 2024-01) Chidolue, Onyinyechukwu; Ohenhen, Peter Efosa; Umoh, Aniekan Akpan; Ngozichukwu, Bright; Fafure, Adetomilola Victoria; Ibekwe, Kenneth Ifeanyi
The digital age has led to a surge in connectivity, innovation, and information exchange, but it has also led to escalating energy consumption by data centers. Green data centers have emerged as a transformative solution, embodying a commitment to sustainability through eco-friendly practices and cutting-edge technologies. Key principles of green data centers include energyefficient hardware, renewable energy integration, advanced cooling systems, and resource optimization strategies. Energy-efficient hardware involves replacing outdated servers, storage systems, and network equipment with energy-efficient alternatives, such as virtualization technologies. This reduces power consumption and sets the stage for a more sustainable and technologically advanced data center infrastructure. Renewable energy integration reduces dependence on traditional power grids and fossil fuels, ensuring an eco-friendlier energy supply. Advanced cooling systems, such as liquid immersion, hot aisle containment, and free air cooling, optimize efficiency while maintaining ideal server temperatures. Resource optimization ensures that every unit of energy is utilized judiciously, contributing to the overarching goal of sustainability. The transition to green data centers presents challenges such as upfront investment costs, integration of renewable energy with fluctuating power grids, and technical complexities associated with advanced cooling systems. However, there are substantial opportunities, including reduced operational costs, improved brand image, and compliance with environmental regulations. Emerging trends in green data centers include artificial intelligence and edge computing, which enable optimization of cooling systems, prediction of peak workloads, and dynamic resource management. By prioritizing energy efficiency, embracing innovative technologies, and staying attuned to emerging trends, data centers can play a pivotal role in forging a more sustainable digital future.
Energy Status in Africa: Challenges, Progress and Sustainable Pathways
(MDPI, 2023) Agoundedemba, Maklewa; Kim, Chang Ki; Kim, Hyun-Goo
Access to modern energy is essential for socioeconomic development, yet Africa faces significant challenges in this regard. For example, Sub-Saharan Africa (SSA) is marked by economic underdevelopment and poverty largely due to the non-environmentally friendly energy used (wood, charcoal) and limited access to modern energy resources. Indeed, this review provides an overview of the African energy landscape; it provides a comprehensive renewables-focused energy pathway for developing a cleaner and more sustainable African energy system. It explores end-use sector electrification in both rural and urban areas in Africa. It emphasizes the rapid expansion of renewable generation, the challenges facing and solutions for the implementation of renewable energy, and the role of emerging technologies. It also presents technological pathways and investment opportunities that will enrich the regional debate and help accelerate the energy transformation across Africa. The analysis demonstrated that the current trends of renewable energy used are hydropower, wind power, biomass, and geothermal energy. The electrification rate in West Africa is less than 58% in urban areas and less than 25% in rural areas. Results show that 65% of the SSA population does not have access to electricity and 81% rely on wood and charcoal. In West Africa, only Ghana (70% or so) and Cape Verde (95.9% or so) have equitable access to electricity between rural and urban areas. The potentiality of solar irradiance in Africa ranges between 3 and 7 KWh/m2/day. The wind speed ranges from 3 m/s to 10 m/s; the wave power can range from 7 to 25 kW/m per site in island regions. Egypt, Morocco, Ethiopia, Tunisia, and South Africa are, respectively, countries leading in wind power technology, and solar energy technology was more advanced in North Africa and South Africa. Finally, geothermal is only developed in Kenya and Tanzania and Kenya is the leader in that field. Although renewable energy in Africa is still growing year to year, it still faces power outages because most renewable energy potentialities are not yet exploited, the technologies used are weak, there is insufficient funding, there is ineffective infrastructure, and there are inadequate or no policies in that field.
Properties of Isolated Galaxies in the Digital Survey Isolated Galaxies (DSIG) Catalogue within a Redshift Range (0.005 < Z < 0.080)
(RAS, 2023) Kinyumu, Marcelina K.; Kimani, Naftali; Nyenge, Raphael; Obonyo, Willice
Evolution of galaxies is known to be influenced by a number of factors such as the environment that hosts the galaxy as well as the galaxies intrinsic properties. The environmental effects on galaxy properties have not been fully quantified. In our study, we analysed a sample of isolated galaxies within 0.005 < z < 0.080 from Sloan Digital Sky Survey data release 16, as part of a Digital Survey Isolated Galaxies catalogue. The aim was to investigate intrinsic physical properties of singly isolated galaxies in low-density environment. We investigated the galaxies morphology, colour, luminosity, stellar masses, and star formation rates (SFRs). A concentration index, Cr, of 2.65 separates our isolated sample into early and late types, with the late-types (spiral galaxies) dominating the isolated sample at 68 per cent as confirmed from the visually classified sample obtained from Galaxy Zoo. Our isolated ellipticals are redder, massive, and more luminous, while the isolated spirals are blue, less massive, and less luminous. Both the isolated spirals and ellipticals have steeper colour relations indicating a fast transition to the red sequence. In the colour–colour analysis, most ellipticals were quiescent with the majority of spirals being star forming. 5 per cent of the isolated ellipticals have recently quenched their star formation and are transiting to the red sequence. The isolated spirals experiences higher star-forming activities, with a small fraction of passively evolving high-mass isolated spirals. Similarly, isolated ellipticals exhibit low SFRs indicating passive evolution, with a fraction being actively star forming
Improving FTO/ZnO/In2S3/CuinS2/Mo Solar Cell Efficiency by Optimizing Thickness and Carrier Concentrations of ZnO, In2S3 and CuInS2 Thin Films Using Silvaco-Atlas Software
(IJRED, 2023) Agoundedemba, Maklewa; Baneto, Mazabalo; Nyenge, Raphael; Musila, Nicholas; N'Zi Toure, Kicoun Jean-Yves
Optimization of optical and electrical properties of active semiconducting layers is required to enhance thin film solar cells' efficiency and consequently became the cornerstone for sustainable energy production. Computational studies are one of the ways forward to optimize solar cells’ characteristics. In this study, Silvaco-Atlas, a powerful software that excels in both 2D and 3D electrical simulations of semiconductors has been used for the simulation in order to investigate the solar cell properties. The architecture of the solar cell simulated was FTO/ZnO/In2S3/CuInS2/Mo. This study aims to optimize solar cell efficiency by optimizing film thicknesses and carrier concentrations via simulation. The designed solar cell was exposed to the presence of a sun spectrum of AM1.5 from a 1kW/m2 incident power density at 300K. The thickness values of the window (ZnO), absorber (CuInS2) and buffer (In2S3) layers were varied to record a solar cell's optimum thickness. The resulting FTO/ZnO/In2S3/CuInS2/Mo solar cell formed by simulation is presented. The best efficiency and fill factor of the solar cell simulated were found to be 41.67% and 89.19%, respectively. The recorded values of current density and the open circuit voltage of the cell were 40.33mA/cm2 and 1.15 V, respectively. Additionally, the maximum power of the simulated solar cell device was 41.68 mW. Optimization results revealed that the most efficient cell found was made up of a window layer with a thickness of 0.03μm, an absorber layer with a thickness of 6.0μm and a buffer layer with a thickness of 0.2μm. The optimized carrier concentration of ZnO, In2S3 and CuInS2 was respectively 1e21 cm-3 , 1e20 cm-3 , 3e18 cm-3 and the optimized Al-doped ZnO value was 1e25 cm-3 . The Absorption spectra indicated that the solar cell's peak absorption occurs between 350 nm and 1250 nm and presented a good external quantum efficiency (EQE) of around 84.52% to 92.83% which indicates good efficiency in the visible domain. This performance is attributed to the transparency of FTO, ZnO and good absorption of In2S3 and CuInS2 thin films.
Effect of the use of inorganic- based photoluminescent materials in solar energy devices application
(WJAETS, 2023) Kimemia, D. Njoroge; Njoroge, W. K.; Mwangi, I.W.; Tonui, M
The dynamic processes that take place in life require energy. The main convenient source of energy even in living tissue are hydrocarbons. This is due to the high-carbon based energy source that eventually converts fossil fuels. The preferred fuels as the primarily and industrial fuel contribute to the observed negative effects which emit pollutants to our environments and result to global warming. To mitigate such energy dependence, solar radiation has been exploited to produce clean energy through the use of photovoltaic cells. Nevertheless, natural radiation varies depending on the season of the year. This study investigated the properties of inorganic materials that support fluorescence after the source of light has been withdrawn. The minerals Sb/Ca/Mn/Ag were prepared hydrothermally to cultivate luminescent properties. The resulting products were characterized using Fourier Transformed Infrared (FTIR) spectroscopy and then applied to extend radiation in a photoactive material of a photocell. Optimal values of the prepared luminescent substance were established to produce the best generated potential in the fabricated solar cells when the natural radiation was withdrawn. Established receptive layer composites (KI/I2: CX) were inserted into a molding dice on top of the photosensitive layer and joined together by pressing. The ensued inorganic luminescent cells optical characteristics were observed under UV radiation (320 - 400 nm) wavelength which produced sequential varying colorations from brown, light blue, blue to red before diminishing gradually as the incident radiation was removed. The open circuit potential voltage (VOC) and current density (JSC) generated parameters were observed. The (0.45, 0.4, and 0.086) V residue potential resulted due to shifting of IR by SbNO3, Sb-PO4, Sb-CO3 and Sb-O luminescent materials. The dopants had promising properties for radiation delay in photo voltaic devices application.
Implementation of a Wide Band and Low Noise Signal Generator Based on Phase Locked Loop
(Kenyatta University, 2023) Mutinda, M. B; Munji, K. M; Nyenge, L. R
A signal generator, an essential electronic test instrument with versatile applications, finds its utility in various fields such as cellular communications, radar systems, microstrip antennas, and electronics labs. This research focuses on the simulation and design of a low-phase noise signal generator operating in frequency range of 35 MHz to 3 GHz . To accomplish this, an Atmega 328P microcontroller on an Arduino board was employed to control the synthesizer based on the Phase-Locked-Loop (PLL) concept. The signal generator’s performance was assessed, with particular emphasis on predicting and analyzing the phase noise generated by the PLL components. To ensure a robust system, a third-order loop filter was devised to effectively suppress spurs. Through simulation using the ADIsimPLL simulation tool, optimal values for loop bandwidth (10 kHz) and phase margin (45°) were obtained. The chosen Phase-Locked-Loop chip for this implementation was the ADF4351, manufactured by Analog Devices. By conducting transient analysis, the time required for the PLL system to transition from the minimum to the maximum output frequency was determined. Furthermore, the characteristics of the generator’s signal were investigated in the frequency range of 35-100 MHz using a cathode ray oscilloscope, and for 101-3000 MHz using a spectrum analyzer. The phase noise levels were calculated at different frequencies (35 MHz, 387 MHz, 1 GHz, 2 GHz, and 2.9 GHz) and analyzed at varying offsets (1 kHz, 10 kHz, 100 kHz, and 1 MHz). Comparatively, the experimental results indicated a higher level of phase noise than what was obtained through simulation. Notably, as the output frequency increased, there was a corresponding increase in the amount of phase noise. The maximum spur observed occurred at the third harmonic, measuring -18.6 dBc, while the minimum spur appeared at the fourth harmonic, measuring -44.5 dBc.
Validation of Popular Models Used in the Analysis of Specific Activity of Primordial Radionuclides in Environmental Samples through 1-D Analytical Modeling
(Hirosaki University Press, 2019) Chege, Margaret Wairimu; Kebwaro, Jeremiah Monari
A scientific model may be considered agreeable if it conforms to given scientific laws, in addition to being able to procure data that can be replicated to an acceptable level when other time-tested and proven methodologies are applied. For first-time researchers such as graduate students, choosing the right model is not always easy and some may opt for a particular model not because they are assured of its correctness, but because it has been used by peers before them. Such tendencies can inadvertently lead to the propagation of flawed models across generations of researchers. In the field of environmental radioactivity, the 􀁬comparison􀁺 and 􀁬conventional􀁺 models are frequently used in the evaluation of specific activity of primordial radionuclides in solids. Through one-dimensional (1-D) analytical modeling, this paper shows that while the conventional model conforms to given scientific laws, the comparison model does not since it wrongly assumes a linear between the intensity of gamma radiation through a solid and mass of the solid. A modified version of the comparison model that corrects for difference in mass between the solids being compared (sample of interest and certified reference material) is advanced.
Radon and Thoron; Radioactive Gases Lurking in Earthen Houses in Rural Kenya
(Frontiers in Public Health, 2019) Chege, Margaret; Hashim, Nadir; Nyambura, Catherine; Mustapha, Amidu; Hosada, Masahiro; Tokonami, Shinji
In this paper, documented studies on radon and thoron concentrations in earthen dwellings and 238U and 232Th concentrations in soil in Kenya are reviewed. High concentrations of the isotopes were recorded in the earthen dwellings despite being generally well ventilated. Mrima Hill in the Coast region recorded the highest thoron levels with a mean of 652 Bq m−3. Twenty five percent of dwellings had thoron concentration in excess of 1,000 Bq m−3. Notably high indoor radon levels were recorded in Taita Taveta also in the Coast region, and in Kenyatta University situated in Nairobi in the Central region of the country. Radon concentration in the Rift Valley region was found to be too low to contribute significantly to radiation exposure. Based on studies on the concentration of 238U and 232Th in soil, the Southwestern region of the country was anticipated to have elevated radon/thoron concentrations in earthen dwellings. Existing studies involving measurement of indoor radon and thoron, and 226Ra and 232Th in soil are relatively few and of a small scale. More extensive studies are therefore necessary not only to corroborate the risk projections but to also generate sufficient data to enable countrywide mapping of indoor radon/thoron risk-prone areas.
Optical Properties and Analysis of OJL Model’s Electronic inter-band Transition Parameters of TiO2 Films
(2018) Musila, Nicholas; Munji, Mathew; Simiyu, Justus; Masika, Eric; Nyenge, Raphael
Titanium dioxide is a wide band gap semiconductor responsible for the bright white appearance in most substances. This material has many unique properties due to its extra-ordinary chemical stability. TiO2 has a conduction band that closely matches the excited energy level of organic dyes hence it is used in fabrication of photo-anode electrode of dye sensitized solar cell. However, the optical properties and the density of states of TiO2 thin films determine the performance of dye sensitized solar cell fabricated from TiO2 photo-anode electrode. For this reason, the purpose of this study was to investigate the optical properties and the OJL electronic inter-band transition analysis of TiO2 nanoparticle thin films. Under the OJL model, the expressions of density of states were specified for the optical transition from the valence band to the conduction band. The TiO2 nanoparticles were prepared using sol-gel and hydrothermal methods and deposited on a conductive glass substrate by screen printing and spray pyrolysis techniques. SEM analysis revealed that TiO2 nanoparticles were spongy and had unevenly sphere-shaped profile while TiO2 nanotubes had a skein-like morphology with abundant number of nanotubes intertwined together. This study showed that TiO2 thin films have both direct and indirect band-gaps. The OJL Gap energy (E0) values were observed to be between 30273.2356 and 31072.0000 wavenumbers which translated to band-gap energies between 3.744 and 3.843 eV. From these findings showed that TiO2 films prepared could be used in the fabrication of high performing dye-sensitized solar cell.
Effect of Tio2 Compact Layer on DSSC Performance
(Path of Science., 2018) Musila, Nicholas; Munji, Mathew; Simiyu, Justus; Masika, Eric; Nyenge, Raphael
Dye-sensitized solar cells offer an economically reliable and suitable alternative in moderating the challenges presented by the existing convectional photovoltaic cells. Whereas, for convectional solar cells the semiconductor adopts both the duty of light absorption and charge carrier transport, these two functions are separated in dye-sensitized solar cells. However, the efficiency of dye-sensitized solar cells has remained relatively low. For this reason, this research was aimed at how to increase the dye-sensitized solar cells performance. To achieve this, compact cover of TiO2 was deposited on a conductive glass substrate by using Holmarc’s Spray Pyrolysis system, using Ultrasonic Spray Head and spraying in vertical geometry, while TiO2 nanoparticles and nanotubes were deposited by screen printing technique on top of a transparent conducting FTO glass slide with or without the TiO2 compact layer. Transmission characteristics showed that introducing TiO2 compact layer on the conductive film lowers the transmission while reflectance properties were less than 15 % for all the prepared thin films. SEM micrographs showed that TiO2 nanotubes had a skein-like morphology with abundant number of nanotubes intertwined together to form a large surface area film. Solar cell performance properties revealed that introducing compact layer to dye-sensitized solar cells improved the performance by 145 % (from 1.31 % to 3.21 %) while TiCl4 treatment on compact layered dye-sensitized solar cells increased the efficiency by 28.79 % (from 0.66 % to 0.85 %).
Assessment of Radioactivity Levels and Risks Due to Different Rock Types from the KERIO Valley “High Background Radiation Area (HBRA)” of Kenya
(IJMPSR, 2015) Agora, Jared Omari; Hashim, Nadir Omar
The goal of this study was to analyse the natural radioactivity levels and assess the contribution of different rock types to environmental dose in the Kerio Valley region of Kenya, a suspect high background radiation area (HBRA). The activity concentrations of 238U, 232Th and 40K in granite, sandstone, tuff, limestone, quartzite, gneiss, marble and conglomerate rocks were found to vary from 72.70 8.47 Bqkg-1-116.15 11.46 Bqkg-1, 40.32 14.48 Bqkg-1- 83.65 9.91 Bqkg-1 and 427.41 48.23 Bqkg-1-1397.24 65.27 Bqkg-1 respectively. Radium equivalent activity and external hazard index show that all the rock types do not exceed the recommended limit of 370 Bqkg-1 and 1, respectively. Calculated outdoor absorbed dose rate ranged from 90.585 nGyh-1 (limestone) to 159.085 nG/h (quartzite) while the indoor absorbed dose rate ranged from 66.696 nGyh-1(limestone) to 157.442 nGyh-1 (quartzite), which are above the world average value of 60nGy-1. The annual effective dose rate analysis is also presented.

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