https://etd.cput.ac.za/handle/20.500.11838/858 2026-05-19T19:27:52Z https://etd.cput.ac.za/handle/20.500.11838/4403 Title: Pico-scale wind turbine system for sustainable electricity provision in off-grid rural regions Authors: Temilola, John Busayo Abstract: This research investigates the practical feasibility of deploying pico-scale vertical-axis wind turbines (VAWTs), specifically of the Darrieus configuration, as decentralized power generation solutions for remote rural communities without access to grid electricity. The overarching goal is to provide sustainable, low-cost electrical energy for essential enduses such as mobile phone charging, small communication devices, and LED lighting. The Darrieus VAWT topology was selected for its compact footprint, omnidirectional wind capture capability, and relatively favorable aerodynamic performance in low to moderate wind speed regimes. A transient Computational Fluid Dynamics (CFD) model of a pico-scale Darrieus VAWT was developed in ANSYS Fluent. The simulation employed a Six Degrees of Freedom (6DOF) dynamic mesh solver, enabling free rotation of the rotor driven solely by aerodynamic forces, thereby capturing realistic self-starting and operational behavior. The analysis covered wind speeds ranging from 2 m/s to 10 m/s and angles of attack (AoA) between 0° and 25°. Aerodynamic performance metrics—such as torque, lift force, and power coefficient (Cp)were evaluated using the Realizable k-ε model turbulence model to accurately resolve boundary layer separation, dynamic stall, and wake vortex structures. A mesh sensitivity study was conducted to ensure grid convergence and numerical stability. Simulation results revealed that the turbine achieved peak performance at an electrical output of 38.29 W, corresponding to wind speeds of 6–8 m/s and AoA values of 5°–10°. Below 4 m/s, torque generation was insufficient to overcome bearing and aerodynamic losses due to inadequate lift production. Conversely, AoA values exceeding 15° induced pronounced dynamic stalls, characterized by flow separation, elevated pressure drag, and reduced Cp. These findings indicate that the design is best suited to steady, moderate- wind environments and is less effective under persistently low or highly turbulent wind conditions. The study concludes that pico-scale Darrieus VAWTs offer viable potential for small-scale rural electrification but are most effective when integrated into hybrid renewable energy systems. Coupling the turbine with photovoltaic modules and battery storage would mitigate the intermittency of wind resources, enhance supply reliability and support broader rural electrification initiatives aligned with the United Nations’ Sustainable Development Goals (SDGs). Real-world prototyping and experimental validation are recommended to refine aerodynamic predictions and confirm long-term performance under field conditions. Description: Thesis (MEng (Chemical Engineering))--Cape Peninsula University of Technology, 2026 2026-01-01T00:00:00Z https://etd.cput.ac.za/handle/20.500.11838/4401 Title: Synthesis and characterisation of bioplastic films through valorisation of starch-rich waste from maize (Zea mays) wet-milling Authors: Ross, Magan Abstract: This thesis presented the synthesis and characterisation of starch-based bioplastic films developed through the valorisation of starch-rich waste derived from the maize wet-milling process. Addressing growing environmental concerns related to conventional petroleumbased plastics, this study explores sustainable alternatives by transforming agro-industrial residues into biodegradable polymer films. Starch, as a renewable and biodegradable polymer, serves as the primary matrix for bioplastic formulation. This research aimed to synthesise starch-based bioplastics for improved performance properties through the addition of filler reinforcements that are rich in lignocellulosic fibre. This research also aimed to address problems of high feedstock costs and the impact on food security through valorising starch and fillers obtained from waste rather than food crops. A comprehensive literature review preceded the experimental work, covering starch production methods, its industrial applications, and bioplastic potential. The experimental methodology involved extracting starch from maize waste collected from a local maize wetmilling facility, followed by the formulation of bioplastic films with varied plasticiser (glycerol), filler (lignin, cellulose-lignin mixture and canola fines), and acetic acid compositions. Mechanical properties, including tensile strength and elongation at break, alongside water absorption behaviour, were assessed. A factorial design model was employed to investigate the effects of five factors, namely starch type (spillage or extract), filler type (cellulose-only or cellulose-lignin mixture), plasticiser mass fraction, filler mass fraction, and acetic acid volume, on key bioplastic properties. Acetic acid was found to have no statistically significant influence on tensile strength, elongation at break, or water absorption and was excluded from further formulations to reduce costs and processing complexity. Spillage starch was identified as the superior raw material, yielding bioplastic films with an optimum tensile strength of 9.7 MPa, elongation at break of 24.9%, and water absorption of 54.2%, outperforming extract starch films in strength and moisture resistance. Subsequently, response surface methodology optimised synthesis conditions for films incorporating canola fines, a lignocellulosic agro-industrial waste. The optimal formulation contained 30% glycerol and 13.5% filler (w/w dry starch), producing films with a tensile strength of 3.3 MPa, elongation at break of 52%, and water absorption of 65%. The incorporation of canola fines improved structural integrity and durability while promoting sustainability by valorising agro-industrial waste, reducing feedstock costs, and aligning with food security goals. This research highlights the critical impact of raw material selection and plasticiser-filler optimisation in developing starch-based bioplastics with desirable mechanical and barrier properties. The elimination of acetic acid simplifies production and decreases costs without sacrificing performance. The findings provide a robust framework for developing costeffective, eco-friendly bioplastics tailored to specific application requirements such as packaging, agricultural films, and single-use products. Future work is recommended to explore lower acetic acid concentrations to fully assess effects influenced by concentration, alongside investigating the long-term durability and environmental biodegradability of these films to confirm commercial viability. Overall, this thesis contributes practical insights and advances the sustainable development of bioplastics derived from agro-industrial waste, supporting the growing bioeconomy and environmental sustainability efforts. Description: Thesis (MEng (Chemical Engineering))--Cape Peninsula University of Technology, 2026 2026-01-01T00:00:00Z https://etd.cput.ac.za/handle/20.500.11838/4399 Title: Design, build and test an assistive lower limb exoskeleton Authors: Mukengere, Musimwa Valery Abstract: In 2017, the global elderly population was approximately 962 million, and this figure is projected to reach 2.1 billion by 2050, according to the United Nations. Africa is anticipated to experience an increase of 225.8 million elderly people during the same period. As of 2019, South Africa's elderly population stood at 5.3 million, and this number is expected to continue growing, according to Statistics South Africa. In recent years, exoskeletons have emerged as a significant technological advancement to assist individuals with limb disabilities. However, many existing LLEs tend to be heavy and cumbersome, thereby increasing the user's metabolic cost. The objective of this study is to design an adjustable, lightweight LLE that enhances the mobility of elderly users by reducing their metabolic expenditure. This LLE is specifically designed for movement in the sagittal plane; therefore, it is assumed that users will rely on crutches for additional lateral support and balance, as the exoskeleton is limited to forward motion. The development of this walking robot was achieved using CAD software to model the LLE. During the modelling process, anthropometric data were used to shape the design of the LLE in relation to its intended user. The LLE was specifically designed to accommodate users ranging from 1.505 m to 1.740 m tall, with a maximum weight of 80 kg. After completing the modelling phase, the LLE was imported into Ansys for finite element analysis (FEA), which was conducted segment by segment. Upon confirming the structural integrity of the LLE frame, the walking robot was imported into MATLAB. An adaptation of the walking algorithm developed by Castro and Kim in MATLAB was modified to align with the LLE's design requirements for this research. During this phase, both kinematic and dynamic modelling were established, along with the Linear Inverted Pendulum Model, which was essential for the LLE's walking functionality. The weight of the LLE frame was measured at 4.942 kg; however, with the actuators included, the total weight rose to 13.338 kg, excluding the 16 kg of the two batteries. FEA results for the LLE frame demonstrated its ability to endure the applied loads without compromising its structural integrity. The yield strength for each segment was maintained below those of aluminium 6061-T6 and 6082-T6 for the frame, and below that of low-carbon steel for the bolts and nuts. Furthermore, the buckling load for each segment of the LLE remained below the critical buckling load during the stance phase, whereas the maximum bending stress experienced by these segments stayed below the specified permissible bending stress during the swing phase. In a MATLAB simulation, the LLE successfully walked 5.63 metres in 10 seconds, demonstrating its responsiveness to the walking algorithm. The scaled-down prototype of the LLE effectively mirrored the walking gait cycle in practice, with results from both the experiment and the simulations closely aligning. The contribution of this research is centred on the development of the LLE design to assist the elderly population by improving their walking capabilities, which are affected by aging. Description: Thesis (MEng (Chemical Engineering))--Cape Peninsula University of Technology, 2026 2026-01-01T00:00:00Z https://etd.cput.ac.za/handle/20.500.11838/4388 Title: The effect of orifice edge geometry on the discharge of non-Newtonian liquids from a tank Authors: Mampouya, Ninelle Samia Abstract: The discharge coefficient can be challenging to predict. This is due to many factors, including rheological characteristics of the flow liquid and orifice geometry. Indeed, predicting the orifice discharge can be difficult but can be accomplished experimentally. Flow rates were measured for square bevel back cut angle, chamfer-, quadrant- and short square-edged orifices from the bottom of the tank. The discharge coefficient was determined and related to the Reynolds number for water, different concentrations of glycerine and CMC solutions, and bentonite and kaolin suspensions. The calibrated average Cd values for: square bevel back cut angle edge was 0.6; chamfer-edged 0.88, quadrant-edged 0.84, and short square-edged 0.58 in the turbulent flow regions. The highest Re values for square-edged orifices (short square-edged and square-edged orifice with bevel back cut angle) were 14000 to 23000 whereas for chamfer and quadrant the Re was 14000 to 25000 for all water tests. The rheological parameters of the slurrie liquids were obtained and utilised in the determination of Re values for the different concentrations of the liquids discharged. The Re values for liquids tested; highly viscous Newtonian, Power Law, Herschel Bulkley and Bingham, were 18, 66, 300, and 340. It was determined that Cd as a function of the Re in the laminar flows were 0.00823𝑅𝑒0.39, 0.0787𝑅𝑒0.40 , 0.0904𝑅𝑒0.39 , and 0.0923𝑅𝑒0.38 for highly viscous Newtonian liquids and 0.0009 Re0.77 , 0.0128 Re0.71, 0.0276 Re 0.57 and 0.0188Re0.63 for square bevel back cut angle, short square, chamfer- and quadrant-edged orifices, respectively. The results obtained for all the orifice geometry explored showed that the Cd increased as the Re increased, but from Re of 1000, the Cd increased significantly before decreasing and becoming constant. This study adds to the empirical data that already exists in the discharge of non-Newtonian liquids from tanks for different edge geometry and confirms that the efficiency of flow in discharging operations is dependent on the edge effect of the orifice flow meter. This will be useful in engineering designs and processes. Description: Thesis (MEng (Chemical Engineering))--Cape Peninsula University of Technology, 2026 2026-01-01T00:00:00Z