Theses and dissertations (Engineering and Built Environment)
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Item Sustainable energy transition and optimization of grid electricity generation and supply(2024-05) Kabeyi, Moses Jeremiah Barasa; Olanrewaju, Oludolapo AkanniClean and low-carbon energy sources and technologies have emerged as a critical driver in delivering the energy transition and achieving net zero-carbon emissions. All energy sources and power systems produce greenhouse gases (GHGs) and hence they contribute to anthropogenic greenhouse gas emissions and resultant climate change besides contributing to other negative environmental impacts. Energy sustainability remains a major challenge globally due to current heavy reliance on depletable and polluting fossil fuels for most of global energy needs. This study examines the energy transition strategies and proposes a roadmap for sustainable energy transition for sustainable energy planning and grid electricity generation and supply in wake of commitments made by the world community to the Paris Agreement aimed at reducing greenhouse gas emissions and limiting the rise in global average temperature to 2oC and preferably 1.5oC above the preindustrial level and realisation of the sustainable development goal of the United Nations. The sustainable transition strategies typically consist of three major technological changes namely, energy savings on the demand side, generation efficiency at production level and fossil fuel substitution by various renewable energy sources and low carbon non-renewable sources like nuclear power and carbon emission reduction strategies like carbon capture and sequestration and a conversion from high carbon fossil fuels like coal and oil to natural gas which remains the cleanest fossil fuel. The study demonstrated that decentralised generation with application of both demand side management and behind the meter management (BTM) strategies are effective measures to increase the use of renewable energy resources which are often locally available leading to higher uptake of renewable energy sources and conversion of consumers to prosumers making the transition economically sustainable. Waste to energy options have a significant potential to contribute to the energy transition e.g. use of biowaste for biogas production, slaughterhouse waste biodigestion for biogas and electricity generation and waste treatment and disposal, waste heat recovery from used geothermal for extra power generation and reinjection to improve the reservoir sustainability and use of bagasse and sugarcane trash for grid-based power production in sugar factories. Therefore, domestic, and industrial scale waste to energy conversion can enhance the economic sustainability of waste management process by offering useful energy substitutes for fossil fuels and enhanced energy security through decentralisation of generation. Whereas sustainable development has social, economic, and environmental pillars, energy sustainability is best analysed by five-dimensional approach consisting of environmental, economic, social, technical, and institutional/political sustainability to determine energy resource sustainability. The study recommends the adoption of sustainability-based planning for energy development and optimisation of electricity generation and supply where energy sources are analysed and ranked based on the five dimensions of energy sustainability instead of Least Cost Development Planning (LCDP) often applied by many countries. On this basis, the sustainable energy transition and optimisation of power generation will rely on both renewable and non-renewable energy since both have an important role in the realisation of the energy transition plans even though the desire is to shift entirely to renewable energy sources by the year 2050. The sustainability of various energy sources was assessed with hydrogen, wind, solar, sugarcane bagasse and cane trash, biogas and ocean energy technologies proving to be among the most sustainable renewable energy and sustainable sources. The study also examined various power plants and energy conversion systems for electricity generation in terms of their specific role and potential in grid-based power generation with hydro power plants, geothermal, nuclear, fuel cells, raking high on performance indicators like load and capacity factors making them ideal for base load power supply. Diesel engines and gas turbines using cogeneration and dual cycle systems powered by cleaner fuels like natural gas, hydrogen and biomethane will play an important role in supplying intermediate and peak load power. The study highlighted enabling technologies and concepts in the energy transition which include decentralisation of generation, cogeneration and trigeneration, demand side and behind the meter management microgrids and smart grid technologies, energy and generation planning and optimisation models, energy storage, electrification of transport and use of electric cars as decentralised electricity sources through the V2X technologies like the G2V and V2G, and carbon capture and sequestration for emissions reduction in fossil fuel power plants making them more sustainable. The study classifies electric vehicles as distributed power plants and variable loads with extensive use of energy storage while sugar cane bagasse is noted as a sustainable energy resource for power generation by cane sugar factories by application of more efficient grid connected cogeneration power plants. The study identified long project gestation period as the main factor limiting nuclear and geothermal energy deployment and recommends the adoption of modularised wellhead generators and small modular nuclear reactors (SMRs) as a solution to enhance exploitation of these sustainable energy and technologies through faster deployment with high degree of flexibility. Biogas and biomethane demonstrated significant potential as renewable energy sources for power generation and substitute fuels in all applications of fossil natural gas. The study recommends sustainability-based planning for the energy sector and power generation and use of both renewable and non-renewable but sustainable sources of energy, adoption of smart energy concept by all sectors and investment in energy technology and infrastructure development for hydrogen and other promising energy sources like ocean thermal, wave and tidal energy and the conversion of the transition from the traditional to smart grid systems and a shift from centralised to decentralised power generation. Since the transport sector accounts for a significant portion of the global greenhouse gas emissions, electrification of the transport sector and coupling with the power sector is a key strategy recommended for the transition with the smart grid and microgrids playing an enabling role. Since energy sources and generation technologies have associated emissions occurring at different sections of the lifecycle, the use of lifecycle costs and emissions are helpful in long term energy and generation planning which demonstrate that renewable sources and nuclear are the most sustainable when analysed within the five dimensions of energy sustainability, but with the non-renewable sources playing a critical role as dispatchable sources for sustainable grid power generation, while the smart grids and use of energy storage can increase the uptake of variable renewables to as high as 95% to 100% up from a low of 20-25% uptake of variable renewables with the traditional grid. This will significantly help the world in achieving the global emissions and climate targets as. stipulated in the Paris Agreement as well as the sustainable development goals (SDGs). Graphical Abstract The overall objective of the study was to provide solutions to build global energy systems based on renewable and sustainable energy resources and optimise power generation and consumption by use of sustainable energy resources and generation technologies based on the five dimensions of energy sustainability. A sustainable energy system should intergrade electricity and other sectors through smart electricity grids, smart gas grids and smart heat grids as demonstrated below.Item Voltage rise mitigation at the point of common coupling of large renewable distributed generation and distribution network(2022-02-24) Akinyemi, Ayodeji Stephen; Kabeya, Musasa; Davidson, Innocent EwaenA lot of changes are taking place in the power system as a result of the introduction of Renewable Distributed Generation (RDG) (e.g., wind and PV systems). Gradually, electricity generated by fossil fuel is being replaced by electricity generated from Renewable Energy Sources (RESs). The deregulation of generation, transmission, and distribution systems due to the introduction of RDGs has brought competition to the electricity market. The electricity generation assets are no longer owned by one or a few owners, as investors have been attracted to the electricity market. Individuals can now generate their own electricity from renewable energy sources such as solar, wind, hydro, wave, tide, and geothermal etc. RDGs are predicted to play a crucial role in the power system transformation in the near future; they are the key to a sustainable energy supply infrastructure because of their inexhaustible and non-polluting nature. However, the integration of RDGs into the power system would have an impact on power system planning, voltage profiles and power quality requirements within the Distribution Network (DN). The voltage rise (or over-voltages) at the busbars within the conventional power system with centralized large power generating units are actually of less concern due to advances in control and protection technologies, but the issue of excessive voltage drop at the far end of transmission lines cannot be overemphasized. The introduction of RDGs into the power system has eliminated the occurrences of the severe under voltage at the far end of transmission lines, but the voltage rise effects and the bidirectional power flow issues at the point of common couplings (PCCs) between RDGs and DN are now of major concern. Indeed, the integration of RDGs can make the power system become bidirectional as electricity can flow from RDGs as well as from DN with a centralised generator. This causes various problems with regards to the power quality, power flow control, frequency control, system voltage profile, etc. Furthermore, the voltage rise effects at PCC with connected-RDG has been a noticeable issue in recent years and requires remedial action. The standard grid code requires that output parameters of RDGs (i.e., voltage profile, current, voltage-current harmonic distortions, power factor, frequency, etc.) at PCC shall be regulated to avoid damage to sensitive equipment connected to the DN, meet up with the power quality criteria, and shall continue providing power support to the DN. Hence, this study focuses on the following two main problems: – firstly, the voltage rise effect, and secondly, the bidirectional power flow constraint at the PCC between RDGs and DN. The analysis and simulations in this thesis are conducted on an IEEE 13-bus sample model and DUT Steve Biko network with penetration of a large RDG. The capacity of the RDG integrated to DN is 1 MW (solar PV). In order to investigate the effect of voltage rise and bidirectional power flow in a DN, a mathematical model of a power distribution network connected with RDG is developed. Intensive simulations are carried out using MATLAB/Simulink software. Furthermore, a control strategy is recommended at PCC for mitigating or minimizing the impacts of voltage rise and reverse power flow when operating at a worst critical scenario, such as minimum load and maximum generation. The control structure consists of the installation of a static compensator (STATCOM) with Pulse Width Modulation (PWM), and the block/deblock and in-loop filtering circuit control scheme to control the active and reactive power. The proposed control strategy also mitigates the voltage-current harmonic distortions, improves the power factor and voltage stability at PCC, and also protects the converter-PWM scheme from grid disturbances and fault currents, as the control of active and reactive power is independent of the grid. This thesis also provides a review of various types of renewable energy resources (RERs) prospects in Africa, looking at how they can be deployed faster within the continent. The thesis also analyses power quality and compensators.Item Optimization of distribution static compensator for mitigation of power quality issues in grid-tied photovoltaic systems(2021-12-01) Adebiyi, Abayomi Aduragba; Lazarus, Ian J.; Saha, Akshay K.; Ojo, Evans E.The global energy demand is rising above the all-time average, and fossil fuel reserves, which power a large chunk of the existing power generation plants, are being depleted. Hence, Renewable Energy Technologies (RET) have become the alternative to meet demand and provide sustainable power. Solar photovoltaic (PV) energy, an essential aspect of RET, which generates emission-free power, is one of the world's emerging resources. Rooftop PV technology installation is advanced in residential and commercial applications due to government subsidies, lower investment costs, and feed-in tariffs. The rapid penetration of PV systems into conventional distribution grids has created some power quality and power stability issues. Power quality (PQ) distortion is the most critical problem in distribution grids. The literature studied revealed that the several nonlinear loads and PV systems power electronic-based inverters that penetrate the grid and contribute to poor power quality issues, i.e., voltage rise, voltage dip, voltage unbalance, flicker, and harmonics. Also, the PV system maximum power point (MPP) controller's performance was investigated since the current-voltage (I-V) characteristic of PV panels is nonlinear and dependent on variables such as solar radiation and temperature. A comparative analysis conducted showed that the incremental conductance tracks the maximum power point better than the perturb and observe method for better power generation. MATLAB/Simulink system model simulations were run for several case studies to analyze the maximum power point tracking (MPPT) algorithm's performance under varied solar irradiation. The results obtained suggested a course to the implementation of the proposed incremental conductance MPPT algorithm. Selected power quality problems in a grid-tied PV system were analyzed via simulations and enhanced with the application of conventional proportional-integral (PI) controlled DSTATCOM. Also, field measurement-based experiments were conducted to determine system performance in a typical grid-tied PV system. The real-life 110 kW grid-tied PV system installed at the Durban University of Technology (DUT), Steve Biko campus, was used for the fieldwork. Taken into consideration was the impact of solar radiation dynamic variation on the field study. According to the results obtained, the 110 kW PV system's voltage quality data were within the limits of the local and internationally defined standards. The concept of DSTATCOM was implemented with an Enhanced Jaya (E-Jaya) optimization algorithm to mitigate specific power quality issues, such as voltage rise, voltage dip, voltage unbalance, and current harmonics. The precision with which the DSTATCOM reference compensation current is selected is vital to the device's performance. The synchronous reference frame theory of phase lock loop (PLL) for a three-phase system is described in this thesis. The objective was to keep the source current THD below 5% to comply with the recommended limits of the IEEE519 Standard harmonic limits. The implemented novel E-Jaya control optimization algorithm-based D-STATCOM provided continuous and adequate voltage regulation and harmonic compensation to mitigate power quality issues in the grid-tied PV distribution system. Simulation comparative analysis results of the developed control method with Artificial Bee Colony (ABC) and Jaya optimization algorithm indicated that the developed novel E-Jaya optimization algorithm enhanced the grid-tied PV system's performance by providing superior voltage regulation and source current THD compensation significantly declined to 1.01% from 31.93%.Item Numerical and experimental investigations of the impacts of the integration of wind energy into distribution network(2021-12-01) Behara, Ramesh Kumar; Ojo, Evans E.; Akindeji, Timothy KayodeThe growing needs for electric power around the world has resulted in fossil fuel reserves to be consumed at a much faster rate. The use of these fossil fuels such as coal, petroleum and natural gas have led to huge consequences on the environment, prompting the need for sustainable energy that meets the ever increasing demands for electrical power. To achieve this, there has been a huge attempt into the utilisation of renewable energy sources for power generation. In this context, wind energy has been identified as a promising, and environmentally friendly renewable energy option. Wind turbine technologies have undergone tremendous improvements in recent years for the generation of electrical power. Wind turbines based on doubly fed induction generators have attracted particular attention because of their advantages such as variable speed, constant frequency operation, reduced flicker, and independent control capabilities for maximum power point tracking, active and reactive powers. For modern power systems, wind farms are now preferably connected directly to the distribution systems because of cost benefits associated with installing wind power in the lower voltage networks. The integration of wind power into the distribution network creates potential technical challenges that need to be investigated and have mitigation measures outlined. Detailed in this study are both numerical and experimental models to investigate these potential challenges. The focus of this research is the analytical and experimental investigations in the integration of electrical power from wind energy into the distribution grid. Firstly, the study undertaken in this project was to carry out an analytical investigation into the integration of wind energy in the distribution network. Firstly, the numerical simulation was implemented in the MATLAB/Simulink software. Secondly, the experimental work, was conducted at the High Voltage Direct Centre at the University of KwaZulu-Natal. The goal of this project was to simulate and conduct experiments to evaluate the level of penetration of wind energy, predict the impact on the network, and propose how these impacts can be mitigated. From the models analysis, the effects of these challenges intensify with the increased integration of wind energy into the distribution network. The control strategies concept of the doubly fed induction generator connected wind turbine was addressed to ascertain the required control over the level of wind power penetration in the distribution network. Based on the investigation outcomes we establish that the impact on the voltage and power from the wind power integration in the power distribution system has a goal to maintain quality and balance between supply and demand.Item The extraction of power and fresh water from the ocean off the coast of KZN utilising ocean thermal energy conversion (OTEC) techniques(2021-02) Gumede, Makhosonke; Naidoo, Pat; D'Almaine, George FrederickOcean thermal energy conversion (OTEC) is an electric power generation system which uses the temperature difference between warm water at the surface (26 oC) and cold water from the depths (5 oC) of the ocean. Generating electricity is not the only function of OTEC as it can also produce significant amounts of fresh water. This can be very important, for example on islands and in some regions, such as Port Edward, where fresh water is limited. This thesis sets out to harness this fluidic energy, thus generating significant amounts of useful electric power for insertion into the national grid, as well as fresh water in Port Edward on the KwaZulu-Natal (KZN), South Coast. The site of Port Edward is naturally suited to the establishment of alternate energy collection sources such as OTEC; the geographical location of this region is additionally suited to the development of Open Cycle - Ocean Thermal Energy Conversion (OC- OTEC). Port Edward lies just beneath the tropic of cancer and on the shore of the Indian Ocean thus two important elements needed for OTEC namely constant sunlight and large coastal areas can easily be found in this region. More importantly, the steep drop in water depth down to 3000 meters makes this an ideal research site for ocean thermal energy conversion in KwaZulu-Natal (KZN). If the proposed theories are correct, this can possibly be used for base generated energy capacity and fresh water. The results are presented with reference to the temperature difference between the sea surface and the sea bottom because it is an important parameter in choosing an actual plant site and system design of OC-OTEC. This research is mainly laboratory based concentrating on design, calculations, modelling and simulation of OC-OTEC. The thermodynamic fluid calculations were undertaken with a view to design the main mechanical components of an OC-OTEC system, i.e. flash evaporator, condenser and steam turbine. SOLID EDGE software was utilized to design OC-OTEC plant and ASPEN PLUS V8.6 software was used to simulate and model the experiment. An OC-OTEC demonstration plant was designed and constructed in an Electrical Power Laboratory at Durban University of Technology (DUT). The experimental study was carried out on the demonstration plant with consideration given to water temperature, mass flow rate of fluid, and pressure. The measurements were taken before and after each component. The selection of a good process modelling and simulation tool was of extreme importance for the success of this work. Throughout the measurements, we found that the thermal efficiency (%) and the power output increased with increasing temperature difference Δt = tw - tc. The power output was produced when the total temperature difference was sufficient to allow heat transfer within the evaporator and provide a pressure drop across the turbine. There was more heat transfer (steam produced) in the flash evaporator at a constant flow rate because the warm water continuously supplied heat energy to the evaporator without losing much energy through the process, therefore continuous feed to the turbine improved constant power output. The thermal efficiencies were increased with increasing pressure across the turbine. The increase of pressure drops across the steam turbine caused the output power to increase. The larger flow rates of the warm water lead to higher amounts fresh water produced from the condenser. The final step in this process was the design of the main components of a practical plant to be used as a pilot plant at a selected location on the KwaZulu-Natal South coast. This will address the problem of lack of water in the region.