Theses and dissertations (Engineering and Built Environment)
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Item Appraisal and optimization of energy-efficient green buildings in South Africa(2024-05) Agbajor, Favour David; Mewomo, Modupe CeciliaGenerally, over 35% of global energy use and 40% of carbon emissions are attributed to the built environment while future forecasts indicate that these values may rise much further. In South Africa (SA), building stocks account for 40% of the country’s final energy demand which strains the country's coal-dependent energy grid and oftentimes results in power outages. Optimizing energy efficiency and thermal comfort while attaining the lofty goal of carbon neutrality is essential for all concerned stakeholders in the building sector globally. Meanwhile, green building (GB), being a recognized revolutionary theory and practice in the building industry, is suggested as a solution to SA’s environmental challenges. On this wise, this research aimed to develop energy-efficient models for optimizing green buildings into the design and operation of buildings to allay their environmental impacts. The goal was to enhance energy efficiency, decrease energy consumption, and mitigate carbon emissions across diverse climates, thus benefiting South Africa's built environment. To achieve the study's goals, three primary research objectives were identified and pursued namely: (i) To provide an overview on status-quo of green building development in South Africa with a view to explore the status quo and provide roadmap for improvement; (ii)To examine the energy-saving potential of incorporating building-integrated greenery systems towards climate-resilience in the subtropical climate zone of South Africa; and (iii) To investigate the energy-performance of green building renewable energy utilization systems within South Africa’s hot and arid climate zones. Initially, the study's first objective entailed a comprehensive literature overview integrating climate, sustainability, and building energy modeling within the South African context. This was carried out through a scoping review approach via the PRISMA guideline of reporting Subsequent objectives involved selecting reference buildings and creating hypothesized models as case studies based on six climate zones from the South African National Standard. For the second objective, a thorough and integrative approach that linked building energy modelling and varying climatic change was devised. The numerical parametric simulation and analysis, being a quantitative research approach was adopted as a data collection method. Similarly, the third objective employed numerical parametric simulation as a data gathering method in this research, which is based on a quantitative analysis to explore various design options iteratively. In the second and third objectives, Global climate databases, Meteonorm, Climate Consultant, and energy simulation software such as DesignBuilder, EnergyPlus, and Polysun were used for weather data analysis, climate modeling, and building energy simulation. The findings highlighted that while South Africa boasts notable green construction projects, scientific research progress has not matched international levels. The focus was on promoting green building adoption through standards, certifications, and incentives. However, gaps were observed in optimized energy performance and post-occupancy evaluation of existing buildings. Despite high awareness, the utilization of green building technologies among South African professionals did not meet anticipated levels. For the second objective, the study's findings indicated an increase in extreme heat waves with higher peak temperatures in the future. Building energy use in the study area is projected to rise by 8-24% from 2030 to 2080. Notably, heat gains primarily result from envelope thermal transfer rather than solar radiation. Greenery systems were found to effectively support green building goals and urban sustainability across anticipated seasons. Nature-based solutions proved successful in adapting to climate change compared to non-retrofitted conventional buildings. For the last objective, the study revealed regions with substantial solar irradiance, indicating potential for renewable energy adoption. It emphasized the need for durable BIPV systems in hightemperature conditions. BIPV modules generated more energy in Upington than Nelspruit due to varying solar radiation. Opportunities were identified for BIPV systems to achieve optimal power generation. The study provides a foundation for informed decision-making, policy formulation, and targeted research in sustainable building practices. The study presents practical principles to guide urban planners and policymakers in integrating eco-friendly technology into both new and existing building designs. This promotes sustainable urban development and reduces cities' carbon emissions. Going forward, to showcase the effectiveness of these energy-efficient and climate-responsive systems to the public and industry stakeholders, it is recommended to establish and enhance largescale demonstration projects in South Africa's subtropical, hot and arid regions.Item Privacy and security for applications and services in future generation smart grids(2022-05-13) Khumalo, Zephania Philani; Nleya, B.Growing energy demands together with the urge to supply available power in a reliable, as well as efficient manner, has led to the gradual upgrading and modernizing of existing power grid systems into Smart Grids (SGs) by way of incorporating supporting information and communication technology (ICT) subsystems. The latter facilities the two-way flow of both energy (power) and information related to the grid's performance, as well as the end user's requirements. Notably, the ICT subsystem enables key entities such as generation, distribution, transmission, and end-user subsystems to interrelated in real-time, and in the process, this achieving a well reliable, robust as well as efficiently managed SG system. The interactions of the various entities constituting the grid result in the emergence of various services and applications exchanging data throughout the interconnected systems. Whereas the SG is quite efficient in rendering its services, it, however, is exposed to various cyber security threats by adversaries. Notably, security threats vary depending on the applications. On the user end networks, the mandatory aggregation of power consumption as well as exchange of power consumption-related information on individual household area networks (HANs) or among HANs and utility's control canter (CC) can result in adversaries tempering with the processes. In particular key security concerns being that during these operations, individuals' privacy, as well as aggregated data integrity, can be compromised as a result of attacks. The resource-constrained nature of associated devices, objects, and elements of the SG at the user side networks and in the SG core, in general, brings about challenges in implementing robust security measures that inevitably involve the performing of complex crypto-operations.Item Secured Power Line Communication based network for advanced metering in Smart Grid(2018-07) Khumalo, Zephania Philani; Nleya, BakheA Smart Grid (SG) generally refers to a modernized power grid system that incorporates Infor mation and Communications Technologies (ICT) so that a two way communication between the grid system (utility) and power users ensures power supply efficiency and optimization to the users. In a way, an SG is an evolved version of legacy power grid systems that manages electricity de mand in a sustainable, reliable and economic manner, built on advanced infrastructure and tuned to facilitate the integration of all involved. The provisioning of duplex communication between the utility and itsusers (customers) allows key devicessuch as SMs to interact directly with the utility 's control center (CC). SGs are destined for provisioning a cleaner environmental sustainable and renewable energy for the future. Its successes mostly rely on advanced ICT design and architecture. It is imperative that it meets the future data transmission and design performance requirements in terms ofrobustness, reliability, and at the same time ensuring end-to-end data exchanges with min imal latencies and losses. The incorporation oflCT, however, results in security and access control challenges, as a result complex network arrangement may be exploited by hackers among other things, access private information and sensitive data, hence the necessity to address vulnerabilities of such systems. Typ ical consequences or repercussions of security and access control threats include energy theft by way of altering of SM data. At present, it is cost effective to implement the ICT related infrastruc ture on the currently unused power line spectrum (i.e. above 50Hz) hence in this work, Power Line Communication (PLC) is elected for provisioning this platform. As such, PLC implementation shall imply the digital communication in power lines concurrently with electrical power transmission and ensuring uninterruption of either of the services, as well as guaranteed efficiency. We address approaches to increasing the data rate of transmission and re duction of bit error rates. That will enhance the performance of PLC and redevelopment ofreliable JCT without additional cost to the existing infrastructure of electrical grids. We also address secu rity and access control by implementing Advanced Encryption Standard (AES) protocol to secure SG related data in our proposed security and access control framework. Results show that the sys tem has low computational requirements, minimal latency and as well ensures confidentiality and integrity. The simulation is run on a combined MATLAB/ OPNET platform.Item An energy efficiency evaluation of a bagasse gasification system for the South African sugar industry(2018) Nene, Sinqobile Wiseman; D'Almaine, George Frederick; Lazarus, Ian JosephAbstract The sugar industry in South Africa has been in existence for over a century. During this period, it has experienced different challenges both in production and market value, but recently; it is experiencing some difficulties in terms of relying solely on the sugar market. Recently, with South Africa undergoing energy-mix processes, the sugar industry has identified an opportunity for the utilization of this excess bagasse. The generation of excess electricity can then be exported into the national grid after all factory electrical requirements have been fulfilled. Several studies have been conducted to develop a system that would be more efficient than the current system which is the direct combustion of bagasse and coal in some factories. This research followed a case study approach. Two systems, direct bagasse combustion and bagasse gasification, were evaluated for their thermal efficiency and their impact on the operation of the sugar industry. According to the available data, bagasse gasification system is said to be at least 50% more efficient than the current direct combustion system. The gasification system utilizes a bagasse gasifier instead of a conventional direct combustion boiler. The gasifier is used to gasify bagasse into synthetic gas, also known as syngas. This gas can be used in gas turbines to generate electricity, and it can be integrated into an existing steam system as a source of steam for process operations. The system analysis showed bagasse gasification system thermal efficiency as 55% as compared to the direct bagasse combustion system thermal efficiency of 19.68%. The knowledge contribution of this study was that of a practical evaluation of the current direct bagasse combustion system and the theoretical evaluation of the bagasse gasification system with similar inputs to identify the benefit of the utilizing the bagasse gasification system.