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Optimisation of feedwater heaters and geothermal preheater in fossil-geothermal hybrid power plant
Sufficient energy supply is a fundamental necessity for the stimulation of socio-economic advancement. However, the current rapid rise in urbanisation has resulted in the significant increase in energy demands. Consequently, the current conventional energy supply systems are facing numerous challeng...
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| Format: | Thesis |
| Language: | English |
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Department of Mechanical Engineering
2020
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| _version_ | 1867613215213486080 |
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| access_status_str | Open Access |
| author | Nsanzubuhoro, Christa |
| author2 | Bello-Ochende, Tunde |
| author_browse | Bello-Ochende, Tunde Nsanzubuhoro, Christa |
| author_facet | Bello-Ochende, Tunde Nsanzubuhoro, Christa |
| author_sort | Nsanzubuhoro, Christa |
| collection | Thesis |
| description | Sufficient energy supply is a fundamental necessity for the stimulation of socio-economic advancement. However, the current rapid rise in urbanisation has resulted in the significant increase in energy demands. Consequently, the current conventional energy supply systems are facing numerous challenges in meeting the world's growing demand for energy sustainably. Thus, there is an urgent and compelling need to develop innovative, more effective ways to integrate sustainable renewable energy solutions into the already existing systems or better yet, create new systems that all together make use of renewable energy. This research aims to investigate and establish the optimum working conditions of a feedwater heater and geothermal preheater in a power plant that makes use of both renewable and non-renewable energy resources, where renewable energy (geothermal energy) is used to boost the power output in an environmentally sustainable way. Henceforth, a simplified model of a Rankine cycle with single reheat and regeneration and another model with a geothermal preheater substituting the low-pressure feedwater heater were designed. The Engineering Equations Solver (EES) software was used to perform an analysis of the thermodynamic performance of the two models designed. The models were used to analyse the energetic and exergetic effects of replacing a low-pressure feedwater heater with a geothermal preheater sourcing heat from a low temperature geothermal resource (temperature generally < 150°C). The results of this research work reveal that the replacement of the low-pressure feedwater heater with a geothermal preheater increases the power generated since less heat is bled from the low-pressure turbine (allowing more heat energy from the steam to be converted into mechanical energy in the turbine). Applying the principle of the Second Law of thermodynamics analysis, the Number of Entropy Generation Units (EGU) and Entropy Generation Minimisation (EGM) analysis were employed to optimise the designed hybrid system. The feedwater heaters and geothermal preheater were modelled as counter-flow heat exchangers and a downhole co-axial heat exchanger, respectively. The feedwater heaters were optimised by means of the method of Number of Entropy Generation Units whereas the geothermal preheater was optimised by means of the Entropy Generation Minimisation analysis method. Owing to the optimisation of these components, the operating conditions of the boiler and turbines were secondarily improved. Overall, this research emphasises the impact renewable energy has on major power plant systems that are in operation and run on non-renewables. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/31128 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:32:36.207Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2020 |
| publishDateRange | 2020 |
| publishDateSort | 2020 |
| publisher | Department of Mechanical Engineering |
| publisherStr | Department of Mechanical Engineering |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/31128 Optimisation of feedwater heaters and geothermal preheater in fossil-geothermal hybrid power plant Nsanzubuhoro, Christa Bello-Ochende, Tunde Malan, Arnaud Engineering Sufficient energy supply is a fundamental necessity for the stimulation of socio-economic advancement. However, the current rapid rise in urbanisation has resulted in the significant increase in energy demands. Consequently, the current conventional energy supply systems are facing numerous challenges in meeting the world's growing demand for energy sustainably. Thus, there is an urgent and compelling need to develop innovative, more effective ways to integrate sustainable renewable energy solutions into the already existing systems or better yet, create new systems that all together make use of renewable energy. This research aims to investigate and establish the optimum working conditions of a feedwater heater and geothermal preheater in a power plant that makes use of both renewable and non-renewable energy resources, where renewable energy (geothermal energy) is used to boost the power output in an environmentally sustainable way. Henceforth, a simplified model of a Rankine cycle with single reheat and regeneration and another model with a geothermal preheater substituting the low-pressure feedwater heater were designed. The Engineering Equations Solver (EES) software was used to perform an analysis of the thermodynamic performance of the two models designed. The models were used to analyse the energetic and exergetic effects of replacing a low-pressure feedwater heater with a geothermal preheater sourcing heat from a low temperature geothermal resource (temperature generally < 150°C). The results of this research work reveal that the replacement of the low-pressure feedwater heater with a geothermal preheater increases the power generated since less heat is bled from the low-pressure turbine (allowing more heat energy from the steam to be converted into mechanical energy in the turbine). Applying the principle of the Second Law of thermodynamics analysis, the Number of Entropy Generation Units (EGU) and Entropy Generation Minimisation (EGM) analysis were employed to optimise the designed hybrid system. The feedwater heaters and geothermal preheater were modelled as counter-flow heat exchangers and a downhole co-axial heat exchanger, respectively. The feedwater heaters were optimised by means of the method of Number of Entropy Generation Units whereas the geothermal preheater was optimised by means of the Entropy Generation Minimisation analysis method. Owing to the optimisation of these components, the operating conditions of the boiler and turbines were secondarily improved. Overall, this research emphasises the impact renewable energy has on major power plant systems that are in operation and run on non-renewables. 2020-02-17T08:10:42Z 2020-02-17T08:10:42Z 2019 2020-02-17T08:09:03Z Master Thesis Masters MSc http://hdl.handle.net/11427/31128 eng application/pdf Department of Mechanical Engineering Faculty of Engineering and the Built Environment |
| spellingShingle | Engineering Nsanzubuhoro, Christa Optimisation of feedwater heaters and geothermal preheater in fossil-geothermal hybrid power plant |
| thesis_degree_str | Master's |
| title | Optimisation of feedwater heaters and geothermal preheater in fossil-geothermal hybrid power plant |
| title_full | Optimisation of feedwater heaters and geothermal preheater in fossil-geothermal hybrid power plant |
| title_fullStr | Optimisation of feedwater heaters and geothermal preheater in fossil-geothermal hybrid power plant |
| title_full_unstemmed | Optimisation of feedwater heaters and geothermal preheater in fossil-geothermal hybrid power plant |
| title_short | Optimisation of feedwater heaters and geothermal preheater in fossil-geothermal hybrid power plant |
| title_sort | optimisation of feedwater heaters and geothermal preheater in fossil geothermal hybrid power plant |
| topic | Engineering |
| url | http://hdl.handle.net/11427/31128 |
| work_keys_str_mv | AT nsanzubuhorochrista optimisationoffeedwaterheatersandgeothermalpreheaterinfossilgeothermalhybridpowerplant |