Department of Chemical Engineering

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https://scholar.sun.ac.za/handle/10019.1/321
Department Process Engineering now has a new name, and will be known from March 2023, as Department of Chemical Engineering.

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Browsing Department of Chemical Engineering by browse.metadata.advisor "Brent, Alan C."

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    Investigating the effects of a green economy transition on the electricity sector in the Western Cape province of South Africa: a system dynamics modelling approach
    (Stellenbosch : Stellenbosch University, 2016-03) Oosthuizen, Juan; Brent, Alan C.; Musango, Josephine Kaviti; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.
    ENGLISH ABSTRACT: Many of the global and regional crises – economic, social, and environmental – that are prevalent today can be attributed to misdirected investments that were made in the past. The current crisis that the electricity sector in South Africa finds itself in can be attributed to such misdirected investments. This current crisis in the electricity sector relates to electricity supply shortages and an increasing carbon footprint. This crisis has to be faced by each of the country’s nine provinces. The Western Cape Province in South Africa has identified the green economy concept as a tool to transform the Province’s economy to one that is more sustainable from an economic, social, and environmental perspective. This transition would include transforming the Province’s electricity sector to one that is more sustainable and more in line with the green economy concept. Three key priorities of this transition include using gas power technologies as a transition fuel, increasing renewable energy capacity, and developing a manufacturing sector that can support the growing renewable energy industry. The difficulty of obtaining finance and prevalence of financial mismanagement in South Africa requires that such a transition be properly planned and managed in order for it to be carried out successfully. The system dynamics methodology was chosen to develop a better understanding of the impacts of different green economy policies and investments in the electricity sector of the Western Cape Province. This was achieved by developing a system dynamics model of the Province’s electricity sector and simulating different green economy investment policies. Five scenarios were simulated over a 40 year simulation period, from 2001 to 2040. The results suggested that continuing on the current policy path would increase the gap between demand and supply, increase the carbon footprint of the electricity sector, and not provide growth in employment in the sector. Strategic green economy investments are expected to impact positively on a number of indicators across a number of sectors: electricity supply, renewable energy share, employment, and greenhouse gas emissions. A few points of concern for policymakers, regarding renewable energy technologies, were highlighted. These include the short operating life of wind and solar PV technologies, their low capacity factors, and their inability to supply base-load power. Other concerns that were highlighted include the expected growth in electricity demand in the Province, large investments needed for electricity capacity expansion, and the benefit of localising manufacturing activities related to wind and solar PV technologies. Overall, the study laid the foundation for future research on the topic of a green economy transition of the Western Cape Province’s electricity sector. The usefulness of applying the system dynamics methodology to green economy transition research was also demonstrated. The study aims to provide relevant and insightful recommendations to the policymakers and stakeholders that are, and will be, involved in the process of transitioning the Western Cape Province to a green economy hub and the Province with the lowest carbon footprint
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    Opportunities for solar thermal process heat integration in South African sugar mills
    (Stellenbosch : Stellenbosch University, 2016-03) Beukes, H. T.; Brent, Alan C.; Hess, S.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.
    ENGLISH ABSTRACT: The sugar milling sector is one of the major agro-processing industries in the South African economy. This sector, however, is under pressure to remain profitable under strenuous economic conditions. In order to enhance the competitive advantage of the industry, stakeholders are investigating opportunities to reduce the input costs of raw sugar production as well as alternative income streams, such as the production of bagasse by-products or the cogeneration of electricity. Since the production of raw sugar is characterised by a significant demand for thermal energy, this study has been conducted to identify opportunities for the integration of solar thermal process heat into this process. Potential solar heat integration points have been identified by considering all of the heat sinks and input streams within a generic raw sugar factory. The suitability of each of the integration points have been assessed in terms of the heat demand and expected impact of solar heat integration. Integration opportunities that conserve bagasse and coal or enhance the potential for electricity cogeneration have been prioritised. The sugar production process consists of various processes, such as sugarcane preparation and juice extraction, clarification, evaporation, crystallisation and drying of the raw sugar. Although there are numerous potential solar heat integration points within these processes, only six have been found to be potentially feasible in terms of the abovementioned criteria. The major opportunities for solar process heat integration into the sugar production process have been found to be the parallel production of live and exhaust steam, the drying of bagasse and sugar, the preheating of boiler feed water and, to a lesser extent, the heating of mixed juice. Basic integration concepts have been developed for the abovementioned integration points in order to assess the potential solar gains. Rudimentary energy yield simulations have been used to estimate the expected solar gains of the proposed concepts and the collector fields have been pre-dimensioned according to the mean thermal loads of the processes. According to this preliminary study, solar thermal process heat can potentially supply between 10 and 27 % of the respective processes’ heat demand without thermal storage. According to a basic economic assessment, the levelised cost of heat (LCOH) of the particular integration concepts is expected to be between R 0.43 and R 1.72 /kWh1. Although this study is only a preliminary evaluation of the potential of solar heat integration into the sugar milling industry, it has been shown that there are feasible integration points within the production process and that solar process heat integration can be considered as technically and financially feasible. However, owing to the intricacies of the heat supply and distribution network of a typical sugar factory, detailed studies should be conducted to optimise the integration of solar heat into the industry.