http://ir.bdu.edu.et/handle/123456789/6 2026-06-15T07:29:25Z 2026-06-15T07:29:25Z Gedifew, Assaye http://ir.bdu.edu.et/handle/123456789/16873 2026-06-05T08:19:57Z 2025-11-01T00:00:00Z

Solar Energy Assessment using Data-driven and Physical Models: Application for Crystalline Silicon Photovoltaic Systems in Ethiopia Gedifew, Assaye Solar radiation, the electromagnetic energy emitted from the Sun, is a fundamental driver of Earth's weather and climate systems and represents a vast, clean energy source. Global solar radiation (GSR) is the total amount of solar radiation (both direct and diffuse) reaching a horizontal surface on Earth. It is a key measurement for evaluating the solar energy potential of a specific location, which in turn is essential for assessing the expected performance and efficiency of solar photovoltaic (PV) system. Thus, the accurate measurement and estimation of GSR is crucial for assessing and utilizing solar energy resources at both global and local scales. Hence, this study investigates estimations of GSR and assesses the performance of crystalline silicon (c-Si) PV cells/modules across Ethiopia, by utilizing a comprehensive approach that integrates data-driven and physical models. The study also implemented various optimization techniques such as determining the optimum tilt angle and tracking mechanisms. For this purpose, twelve machine learning (ML) and one stacked/ensembled model were trained and validated with hourly, daily and monthly ground-based global solar radiation data from 16 synoptic weather stations (2020-2022), supplemented by meteorological, aerosol, and sky condition data from MERRA-2 and NASA POWER archives. The three stations with distinct weather patterns were withheld from the model development process for model transferability/generality test. A stacked/ensemble model (i.e., constructed by stacking better performing separate models) showed exceptional predictive performance with error metric values ranging (R²: 0.956-0.963; RMSE: 9.938-11.784 W/m²) for all time scales. With this performance capability we generated a high-resolution (1° x 1°) global solar radiation data across Ethiopia for the year 2022, and the distribution showed a precise spatial and seasonal dependence with the highest in spring (i.e., 594 - 641 W/m2; eastern and northeastern) and lowest in summer (i.e., 359 – 405 W/m2; western and southern parts of the nation). Such analogs were also observed on the peak sun hours and plane-of-array (POA) irradiance distribution with their annual value ranging from 4.83 – 6.57 kWh/m2/day and 0.65 – 1.05 kW/m2, respectively, across the nation. Here it’s worth noting that to model POA irradiance, we implemented five decomposition and six transposition models (i.e., thirty different independent combinations). Furthermore, we incorporated POA irradiance into a single diode PV cell model to evaluate c-Si PV cell performances. Consequently, the annual PV cell temperature, ranging vii from 38.84°C to 55.45°C, significantly impacted device parameters. The short-circuit current (Jsc) mirrored POA irradiance trends, while the open-circuit voltage (Voc) showed an inverse temperature dependence. The annual PV cell efficiency varied from 13.02% to 22.35%, with clear average seasonal variations such as the highest in spring (20.72%) and the lowest in summer (16.01%). Besides, optimal PV module tilt angles and implementation of different tracking mechanisms were determined. The monthly optimal tilt angles ranged from 0° (July) to 47.90° (January), while seasonal averages were observed as 29.40° (winter), 21.65° (autumn), 12.34° (spring), and 8.8° (summer). The annual optimal tilt angle varied from 14.51-21.52o. In addition, the performance of different tracking mechanisms (dual/full axis: DAT, vertical-axis: V-axis, east-west/incline east-west: EW/IEW, north-south: NS) were also evaluated. Dual/full axis tracking yielded the highest annual average efficiency (44.89%), while NS tracking resulted in a 28.46% energy loss compared to horizontal mounting. On the other hand, PV module mounted at optimal tilt angle resulted in a 4.12% gain, while EW/IEW and vertical axis tracking yielded 43.12% and 24.94% energy gains, respectively compared to horizontally mounted. Overall, this study provides a valuable resource for selecting, comparing, and designing future solar PV systems in Ethiopia. It contributes to strategic PV deployment by aiding in energy assessment and forecasting. Moreover, the study offers an optimal tilt angle model, guiding the selection and implementation of the best tracking mechanisms for PV modules/panels in Ethiopia. This information is essential for effective energy assessment and forecasting across the nation

2025-11-01T00:00:00Z Wondim, Megbaru http://ir.bdu.edu.et/handle/123456789/16870 2026-06-05T08:01:44Z 2025-08-01T00:00:00Z

Species Composition, Vegetation Structure and Regeneration Status of Woody Plants in Gonje Thewodros Monastery Forest in Gonje Kolela District, North Gojjam Zone, Amhara Region, Bahir Dar, Ethiopia. Wondim, Megbaru The Churches and Monasteries are the main sites for biodiversity and forests conservation in Ethiopia. However, the loss of biodiversity and forest degradation is the most burning issue in Ethiopia as well as in Gonje Thewodros Monastery Forest (GTMF), because of anthropogenic and naturally induced disturbances. Thus, this study was aimed at evaluating the woody species composition, vegetation structure and regeneration status of GTMF in Gonje Kolela district. A Systematic random sampling designs were employed to set sampling plots for vegetation data collection. I have used Shannon-Weiner diversity index and Sorensen similarity coefficient for analysis of data. Five sampling transect lines and the total of (14,000 m2) 35 main sampling plots and (4375m2 and 175m2) 175 sub-plots were used to collect matured, saplings and seedlings woody plant species, respectively. The GTMF had three different types of communities were classified based on the dominant woody plant species. A total of 62 woody plant species belonging to 52 genera and 34 families were recorded and identified. The majority of the woody plant species were shrubs (50%) and the remaining were trees and climbers contributed 37% and 13%, respectively. GTMF had 3.5 and 0.85 the Shannon-Weiner diversity index and evenness value, respectively. The percentage of Sorensen similarity coefficient among communities ranges from 43.3% - 66.7%. Out of 62 woody plant species, 6.5% and 71% were endemic and had fair regeneration status, respectively. In this study, the degree of dominance and abundance of woody plant species was not equal in their IVI. Therefore, GTMF had great role in conservation of biodiversity. However, currently, the GTMF is under anthropogenic and naturally induced disturbances. The majority anthropogenic induced disturbance were grazing, farm land expansion to the monastery as well as residents and selective cuttings of trees and shrubs. Generally, the Monastery forest is under severe threat due to diversity of factors. Therefore, protection of plant diversity through different and feasible conservation strategies Such as finding alternative for grazing and farmlands and avoiding selective cutting of trees is recommended.

2025-08-01T00:00:00Z Girum, Alemayehu http://ir.bdu.edu.et/handle/123456789/16868 2026-06-05T07:53:12Z 2025-11-01T00:00:00Z

Hesitant Fuzzy Algebraic Structures on Pseudo-TM Algebra with Multicriteria Decision Making Girum, Alemayehu This dissertation presents an in-depth study of fuzzy algebraic structures, specifically focusing on TM-algebras and pseudo-TM algebras by using various extensions of fuzzy set theory such as hesitant fuzzy sets, and bipolar hesitant fuzzy soft sets. These theories help to deal with uncertainty, hesitation, and vagueness in mathematical modeling. In this study, we also define and investigate fuzzy subsets within pseudo-TM algebras. Important structures like fuzzy pseudo-TM subalgebras and fuzzy pseudo-TM ideals are introduced. Their properties are discussed using operations such as Cartesian product and homomorphism. It is shown that the intersection of two fuzzy pseudo- TM-subalgebras is also a fuzzy pseudo-TM subalgebra, but their union may not be. The study deals with the idea of fuzzy congruence relations more deeply. A fuzzy congruence relation is a fuzzy equivalence relation that respects the algebraic structure. It is shown how such relations can preserve the fuzzy structure under mappings and how they can be used to simplify the algebra into equivalent classes. The connection between fuzzy pseudo-ideals and fuzzy congruence relations is also discussed, providing a strong algebraic framework for fuzzy systems. The study moves from fuzzy sets to hesitant fuzzy sets. It introduces hesitant fuzzy TM-subalgebras, hesitant fuzzy Tideals, hesitant fuzzy pseudo-TM subalgebras, and hesitant fuzzy pseudo-ideals. These structures allow multiple degrees of membership for each element, capturing hesitation in decision-making. Various properties of these structures are analyzed. It is shown that Cartesian products and homomorphic images of hesitant fuzzy ideals preserve the structure, under certain conditions. This provides a useful tool for modeling uncertain systems in mathematics and applications. The notions of bipolar hesitant fuzzy soft sets in TM-algebras are introduced. The combination of bipolarity (positive and negative views), hesitation (multiple values), and soft sets (parameter-based uncertainty) creates a powerful structure. These structures are applied to decision-making problems, especially when both satisfaction and dissatisfaction need to be considered. A numerical example is provided on selecting the best alcoholic drink based on multiple criteria, such as taste, health impact, and cost. Each criterion is evaluated with both positive and negative opinions, along with hesitation. The bipolar hesitant fuzzy soft set model is used to combine these opinions and find the best option. This shows the practical usefulness of the theoretical framework developed in this work. This research not only advances the theoretical understanding of fuzzy and hesitant fuzzy structures in algebra but also offers practical tools for modeling complex decision-making problems. The findings have potential applications in artificial intelligence, computer science, medical diagnosis, and other fields where human hesitation, dual opinions, and uncertainty are common

2025-11-01T00:00:00Z Abebe, Asmamaw http://ir.bdu.edu.et/handle/123456789/16867 2026-06-05T07:50:05Z 2025-11-01T00:00:00Z

Fuzzy Hyper and Pythagorean Fuzzy Composite Structures on BCL–Algebra and LiuB–Algebra Abebe, Asmamaw This dissertation presents det ailed and thorough research on the notions of hyper BCL–algebra, fuzzy substructures in hyper BCL–algebra, fuzzy substructures in BCL–algebra, Pythagorean fuzzy substructures in BCL–algebra, fuzzy substructures in LiuB–algebra and Pythagorean fuzzy substructures in LiuB–algebra. It provides new theoretical understanding, well refined definitions and rigorous characterizations that contribute to the development of algebraic knowledge about these structures. The research begins by introducing the hyper BCL–algebraic structures, supported by proven properties, under which (weak, strong) hyper subalgebras, (weak, strong) hyper deductive systems and (weak, strong) hyper ideals of hyper BCL–algebra are defined and several relevant properties are investigated. The relations among strong hyper subalgebras, weak hyper subalgebras and hyper subalgebras, as well as among strong hyper ideals, weak hyper ideals and hyper ideals of hyper BCL– algebra are clearly demonstrated in the context of hyper BCL–algebras. In hyper BCL–algebras, the relationship between hyper deductive systems and weak deductive systems is established. The intersection and union of corresponding (weak, strong) hyper substructures of hyper BCL–algebras are shown to be conserved. Following the introduction of hyper substructures, the notions of fuzzy hyper algebras are introduced, characterized as fuzzy (weak, strong) hyper subalgebras, fuzzy (weak, strong) hyper deductive systems and fuzzy (weak, strong) hyper ideals. The conservation of intersections of corresponding substructures is established; however, unions of such substructures are generally not conserved justified by examples. The relationships among fuzzy (weak, strong) hyper substructures are also explored. After investigating additional relevant properties, we introduce the notions of fuzzy subalgebra, fuzzy deductive system and fuzzy ideal of BCL–algebra. Moreover, we prove that the complements of fuzzy substructures of BCL–algebra and its characteristic functions correspond to fuzzy substructures of BCL–algebra. In the BCL–algebra, we also prove that intersections of fuzzy subalgebras, fuzzy deductive systems and fuzzy ideals are fuzzy subalgebra, fuzzy deductive system and fuzzy ideal of BCL–algebra, respectively; however, unions of such substructures are not conserved justified by counter examples. Several additional properties of fuzzy substructures of BCL–algebra are also demonstrated. Following the introduction and investigation of fuzzy subsets of BCL–algebra, we extend these notions to Pythagorean fuzzy substructures of BCL–algebra; viii namely, Pythagorean fuzzy subalgebra, Pythagorean fuzzy deductive system and Pythagorean fuzzy ideal of BCL–algebra along with an investigation of their relevant properties. After introducing the Pythagorean fuzzy substructures of BCL–algebra, we present new definitions of LiuB–algebra based on BCL–algebra combined with a semi–group. These definitions are illustrated with examples and their properties are explored. Following these investigations, we introduce fuzzy substructures of LiuB–algebras, including fuzzy subalgebras, fuzzy deductive systems and fuzzy ideals. In relation to substructures of LiuB–algebra, we extend these notions to Pythagorean fuzzy subalgebra, Pythagorean fuzzy deductive system and Pythagorean fuzzy ideal and relevant results are derived, with their properties explored in detail. Finally, the fuzzy subsets of BCL-algebra and LiuB–algebra and Pythagorean fuzzy sets of BCL-algebra and LiuB–algebra are described by making use of some basic tools. These include the Cartesian products of fuzzy subalgebras in BCL-algebra, the level sets in Pythagorean fuzzy deductive systems of BCL-algebra, and the homomorphisms of Pythagorean fuzzy deductive systems of LiuB–algebra. In addition, LiuB–algebra is also described through the Pythagorean ( , )–fuzzy ideal, and related properties arising from each of these descriptions are carefully examined. ix

2025-11-01T00:00:00Z