Faculty of Engineering and Built Environment
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Item Design and simulation of an optimized small wind turbine(2021-12-01) Sanjimba, Norberto Fernando Soares; Tabakov, Pavel Y.The volatility of fossil fuel's price, pollution, and emission associated with converting fos- sil fuel into a useful type of energy led man to search for more sustainable energy sources that are pollution-free and renewable. Today, renewable energy technologies, such as solar and large wind turbines, are developed to a stage of maturity, having the cost of produc- ing electricity dropping signicantly in the last decade, therefore making these technologies competitive with the traditional counterpart. The cost of producing electricity through small wind turbines is still high compared to large wind turbines or photovoltaic technology. For small wind turbines to successfully compete with other technologies and contribute to the diversication of o-grid technology, further research is needed to reduce the levelised cost of energy (LCOE). Therefore, this study aims to reduce the levelised cost of energy (LCOE) of small wind turbines. To achieve the ob- jective, a 10 kW wind turbine operating at a site of an average wind speed of 7.5 m/s was designed, optimized, and simulated. With low LCOE in mind, the turbine components were designed as simple as possible to reduce manufacturing costs. The blades are made of uniform cross-sectional area, which made possible to use aluminum as the blade material, and the blade cross-sectional area is made out of a high lift airfoil. The hub is made of aluminum and modelled and designed as a disc with holes to bolt the blades and attach the main shaft. The mainframe is treated as a thick plate with a proper arrangement to connect the generator, the main and yaw bearings, the tail support, and any other ancillaries needed. An octal tapered tower with a height of 20 m made of steel was designed and optimized for low weight. The electrical power is to be produced by a direct drive variable speed permanent magnet synchronous generator. The control system is designed in such a way that allows the turbine to operate in maximum power eciency for any speed below the rated speed, and to increase reliability, a sensorless control system is suggested. The research started with a broad review of the relevant literature on wind turbines in general and small wind turbines. The turbine blades design began by analysing the aero- dynamic performance of the blade. To accomplish that, XFoil was used to generate the aerodynamic parameters of the airfoil, the Blade Element Momentum (BEM) method was used to estimate the blades' aerodynamic performance, and Qblade was employed to com- pare the results, and Computational Fluid Dynamics (CFD) was used to verify the results. The preliminary design was done using standard IEC 61400-2 to obtain the load cases, and general engineering formulas, CFD and Finite Element Analysis (FEA) was used to analyse the load in the components according to IEC 61400-2, FAST-V7 was used to simulate the turbine's overall performance, standard formulas were used to evaluate the economic perfor- mance of the design, MatLab was used to perform all needed calculations. In this study, it is evident that using standard IEC 61400-2 to estimate the load, gyroscopic load components dominate the design, and the control system must be used to limit those loads. The designed turbine has relatively high eciency and low LCOE.Item Optimisation of biodiesel production from Croton Gratissimus oil(2018) Jiyane, Phiwe Charles; Musonge, Paul; Tumba, KanikiConsumption of liquid energy products, primarily fossil-based fuels, by the transportation industry, is high and has caused an escalation of the energy crisis facing global communities. This protracted use of fossil fuels has inadvertently resulted in an increased concentration of CO2 and other greenhouse gases (GHG) in the atmosphere, leading to environmental degradation. An environmentally friendly alternative fuel source, in the form of biofuels, has been found. These biofuels are biodegradable, boasting reduced levels of particulate matter (PM), carbon monoxide (CO), obnoxious sulphur (SOx) and nitrogen compounds (NOx) in their combustion products. In African countries, particularly the Republic of South Africa (RSA), the urgency for the establishment of a viable biodiesel industry is driven by the vulnerability of crude oil prices, high unemployment, climate change concerns and the need for the continent’s growing economies to use their resources in a sustainable manner. In order to address these concerns, this investigation focused on the extraction of non-edible oil from the seeds of the indigenous Croton gratissimus plant, the catalytic synthesis of biodiesel and the optimisation of the developed biodiesel production process. In this optimisation study, biodiesel was produced from oil extracted from Croton gratissimus seeds using synthesised monoclinic sulphated zirconia (SO42–/ZrO2) and KOH as catalysts. Low oil extraction yields (29.35%) obtained for this crop were attributed to its low unsaturated fatty acid content of 25.4%. From the model developed for the esterification of Croton 2– gratissimus oil, the concentration of SO4 /ZrO2 catalyst had the most significant effect in the reduction of the Acid Value of oil. This was substantiated by flat response surfaces observed on the RSM surface plots when all other design factors were varied whilst keeping catalyst concentration constant. The operating conditions for the esterification process that could give an optimum Acid Value of 2.693 mg KOH/g of oil were therefore found to be; 10.96 mass % SO42–/ZrO2 catalyst concentration, 27.60 methanol-to-oil ratio and 64 0C reaction temperature. In the optimisation of the transesterification process, the model showed that catalyst concentration, methanol-to-oil ratio, reaction temperature, and their interactions were all significant model terms. But catalyst concentration and methanol-to-oil ratio, were the terms found to have the most influence on the percentage fatty acid methyl ester (FAME) yield and percentage FAME purity. It was established from the combined model that optimum responses of 84.51% FAME yield and 90.66% FAME purity could be achieved when operating the transesterification process at 1.439 mass % KOH catalyst concentration, 7.472 methanol-to-oil ratio and at a temperature of 63.50 0C. The two-step biodiesel process used in this work, produced biodiesel with a high FAME purity and a relatively high FAME yield. Improvement of the oil extraction process may be possible with polar co-solvent such as ethyl acetate, which may increase the FAME yield in the Croton gratissimus biodiesel production process.