Doctoral Degrees (Mechanical and Mechatronic Engineering)

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Browsing Doctoral Degrees (Mechanical and Mechatronic Engineering) by browse.metadata.advisor "Brent, Alan C."

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    Spatial-temporal model to evaluate the system potential of concentrating solar power towers in South Africa
    (Stellenbosch : Stellenbosch University, 2016-12) Gauche, Paul; Von Backstrom, Theo W.; Brent, Alan C.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: Concentrating solar power (CSP) is a relatively unknown power generation technology entering into the growth phase of its technology life-cycle. The value of CSP is relatively well understood from a state of the art point of view, but its value and potential in a power generation network is not as clear. South Africa potentially offers an accelerated market due to constrained electricity capacity and an excellent solar resource. The objective of this dissertation is to quantifiably evaluate CSP in the electricity system of South Africa and thereby aid national policy. The methodology required the development and validation of a model to predict the performance of central receiver CSP plants in an electricity system. The Integrated Resource Plan (IRP) of South Africa legislates the definition of the national electricity system with a twenty year horizon and intended updates every two years. The IRP initiated significant renewable energy adoption, but only 1 GW of CSP is officially allocated until 2030, despite several analysis updates recommending increased capacity for CSP in scenarios based on scarcity of resources for fossil or nuclear technologies. The spatial-temporal CSP model was developed and validated within available means to about 7 % accuracy within a standard deviation of known CSP tower settings. This model permits cascaded allocations of CSP capacity by location, plant configuration and size without being overly prescriptive to technology specification or advancements. The model is, therefore, able to comprehensively evaluate a distributed network of CSP towers within an energy system environment. A deterministic energy system model and a probabilistic economic model were developed to test the behavior of the CSP model in an energy system. The value of CSP towers was studied in various scenarios, including an emulation of the 2010 IRP, the 2013 proposed IRP Update and scenarios commissioned by the Worldwide Fund for Nature (WWF) in South Africa. The WWF scenario resulted in a renewable-centric proposal for 2030 that includes 8 GW of CSP with 12 storage hours on average. This scenario unexpectedly outperforms other scenarios in terms of cost regardless of resource scarcity. The analysis, however, correlates with other recent research, finding that CSP capacity needs to operate only serving the system to avoid unserved power. In this mode, CSP levelized cost of energy (LCOE) increases due to a drop in capacity factor, but the marginal value of electricity (MVOE) attributable to this operating mode is R 0.48 per kWh. MVOE is introduced as a method to inform tariff policy. The model successfully demonstrates the importance of technology, space and time within a constrained electricity system in order to fully evaluate the role of CSP towers. The evaluation itself provides initial quantified evidence that CSP has an important role for South Africa and should be pursued by investing more resources in research, planning and implementation.
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    Synthesis of an off-grid solar thermal cogeneration and intelligent smartgrid control system for rural applications
    (Stellenbosch : Stellenbosch University, 2018-03) Prinsloo, Gerhardus Johannes; Dobson, Robert Thomas; Brent, Alan C.; Perold, Willem ; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH SUMMARY: Access to reliable, affordable, and modern energy services has a vital role to play in attaining the Sustainable Development Goals promulgated by the United Nations, since this factor directly impacts on 74 % of their associated overall targets. With 80 % of the global energy-impoverished population living in rural areas, it is crucial to reach these communities to solve the global energy access problem. Sub-Saharan Africa is of particular concern as 16 of the 20 high-impact countries (lowest electrification rates) are located in this region, with current endeavours not able to keep up with population growth. Microgrids are critical in solving this problem, with about 44 % of the rural Sub-Saharan Africa population gaining access to electricity by 2040 expected to be connected by microgrids. This study identifies the need for advanced village microgrid control governance to fulfil the role of smart energy systems of future Smart Villages. While R&D pathways for future Smart Grid microgrids in the Global North are well defined, there are no definitive pathways for the development of advanced microgrids in the rural village landscape of the Global South. This dissertation hypothesises that rural village microgrids should adopt their operating principles from state-of-the-art future Smart Grid developments, and tailor these to address the knowledge gap pervading in the rural village microgrid landscape. This hypothesis is based on observations of global energy market trends that indicate a likely convergence in operating methods between Smart Village and Smart City energy systems. This study applies a model-based design-thinking methodology to the conceptualisation process of a proposed microgrid platform suitable for future Smart Village microgrids. This steered the development process to observe the challenges to rural electrification from the perspective of the village energy user as the primary stakeholder while formulating a concept platform based on future Smart Grid operating principles. This study combines state-of-the-art microgrid control principles, based on transactive energy management, with innovative methods that allow for functional interaction between the microgrid system and energy prosumers in the rural village. This dissertation thus establishes the interactive-marketbased- control (i-MBC) approach at the core of the proposed next-generation Smart Village microgrid platform. The feasibility of this unique approach is demonstrated in synthesis experiments, using rural Smart Village case-based challenge scenarios. In addition to the current energy market drivers and trends that support this hypothesis, this research presents additional evidence to support the philosophy that Smart Village microgrids and Smart City microgrids can, to a large extent, share the same developmental pathway. A firm standpoint on the future of rural village microgrids is taken, as reflected and confirmed in the proposals for the Smart Village microgrid platform. This standpoint gives clear directives on the overlapping principles of Smart Cities and Smart Villages that will help researchers and energy access practitioners to select aspects of a Smart Grid R&D development program that is relevant to Smart Village microgrids.