Appropriate solar spectrum usage : the novel design of a photovoltaic thermal system
- Elshik, Ebrahim, Bester, Rudolf, Nel, Andre
- Authors: Elshik, Ebrahim , Bester, Rudolf , Nel, Andre
- Date: 2017
- Subjects: Sustainable buildings , Photovoltaic power systems , Renewable energy sources
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/217739 , uj:21677 , Citation: Elshik, E., Bester, R. & Nel, A. 2017. Appropriate solar spectrum usage : the novel design of a photovoltaic thermal system.
- Description: Abstract: The path towards zero energy buildings is fraught with many challenges, the onsite renewable energy production to drive consumer appliances that are not low or zero energy is an important challenge. Therefore, developing the energy production such that the production mode is matched to the usage mode is the simplest manner to improve efficiency. As such, energy consumption for lighting could be significantly reduced by optimizing the building`s design to maximize direct daylight usage, similarly cooking using solar stoves, or water heating using solar geysers eliminates the need for PV cells to generate electricity. The most important energy consumption in most buildings is HVAC (accounting for approximately 40% of a building`s energy consumption) which can be addressed with the use of a solar power absorption chiller. This article introduces the design of a novel solar concentrated photovoltaic thermal (CPVT) system that produces electricity and thermal energy simultaneously from the same surface area. The goal of the proposed system is to provide sufficient heat for an absorption cooling system, water heating as well as to produce electricity in a cost effective way. The CPVT system is designed to operate over a wide spectrum (400nm upward contains around 90% of the incident solar radiation spectrum). In the proposed system, solar irradiation is highly concentrated (to the equivalent intensity of approximately 100 suns) onto a single point, using a dual axis sun tracking concentrator with a Fresnel lens. A filter then separates the infrared (IR) from the visible light (VL) components using an imaging lens (viz. a hot mirror which has approximately a 98% filter efficiency). The IR is then utilized for heating while the VL components power the PV cell. The efficiency of the electricity generation in the PV cell improves when the IR component is removed from the incident solar irradiance. High-temperature high pressure water, at approximately 95-120oC (203–248oF), is generated by the IR and serves as a heat source for the absorption cooling system (lithium bromide water / ammonia-water). The proposed system is expected to deliver electricity at the rate of 0.08 W/cm2 (0.2032 W/in2) of PV cell area, and around 0.04W/cm2 (0.1.016 W/in2) collector area. Given that the ratio of collector area to PV cell area is ±9:1 this allows us to design the relative size to suit the building requirements.
- Full Text:
- Authors: Elshik, Ebrahim , Bester, Rudolf , Nel, Andre
- Date: 2017
- Subjects: Sustainable buildings , Photovoltaic power systems , Renewable energy sources
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/217739 , uj:21677 , Citation: Elshik, E., Bester, R. & Nel, A. 2017. Appropriate solar spectrum usage : the novel design of a photovoltaic thermal system.
- Description: Abstract: The path towards zero energy buildings is fraught with many challenges, the onsite renewable energy production to drive consumer appliances that are not low or zero energy is an important challenge. Therefore, developing the energy production such that the production mode is matched to the usage mode is the simplest manner to improve efficiency. As such, energy consumption for lighting could be significantly reduced by optimizing the building`s design to maximize direct daylight usage, similarly cooking using solar stoves, or water heating using solar geysers eliminates the need for PV cells to generate electricity. The most important energy consumption in most buildings is HVAC (accounting for approximately 40% of a building`s energy consumption) which can be addressed with the use of a solar power absorption chiller. This article introduces the design of a novel solar concentrated photovoltaic thermal (CPVT) system that produces electricity and thermal energy simultaneously from the same surface area. The goal of the proposed system is to provide sufficient heat for an absorption cooling system, water heating as well as to produce electricity in a cost effective way. The CPVT system is designed to operate over a wide spectrum (400nm upward contains around 90% of the incident solar radiation spectrum). In the proposed system, solar irradiation is highly concentrated (to the equivalent intensity of approximately 100 suns) onto a single point, using a dual axis sun tracking concentrator with a Fresnel lens. A filter then separates the infrared (IR) from the visible light (VL) components using an imaging lens (viz. a hot mirror which has approximately a 98% filter efficiency). The IR is then utilized for heating while the VL components power the PV cell. The efficiency of the electricity generation in the PV cell improves when the IR component is removed from the incident solar irradiance. High-temperature high pressure water, at approximately 95-120oC (203–248oF), is generated by the IR and serves as a heat source for the absorption cooling system (lithium bromide water / ammonia-water). The proposed system is expected to deliver electricity at the rate of 0.08 W/cm2 (0.2032 W/in2) of PV cell area, and around 0.04W/cm2 (0.1.016 W/in2) collector area. Given that the ratio of collector area to PV cell area is ±9:1 this allows us to design the relative size to suit the building requirements.
- Full Text:
Design of a reliable hybrid off-grid solar-wind micro-grid for rural electrification
- Authors: Mhandu, Simbarashe Raphael
- Date: 2020
- Subjects: Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/481792 , uj:43667
- Description: Abstract: The economic growth of countries leads to an increase in energy demand. Energy consumption in most developing countries is likewise increasing due to their economic growth. This has raised a concern about meeting the energy shortage in their communities. The rising alert of air and environmental pollution has created opportunities for electricity access through renewable energy sources as a viable solution to meet the growing energy demand. Therefore, power generation through renewable energy can be a sustainable energy solution for developing countries. Considering the rate of developments in some countries (e.g. Zimbabwe), the extension of power lines from the main grid in a centralized manner to remote and rural areas is still economically challenging. This study addresses how to improve electricity access to rural areas in Zimbabwe. The overall electrification rate of Zimbabwe is 40.42% with approximately 85% urban population and 15% rural population, which has a deficit in rural electricity access. There is therefore a great concern to increase access to electricity in rural and remote areas... , M.Ing. (Electrical Engineering)
- Full Text:
- Authors: Mhandu, Simbarashe Raphael
- Date: 2020
- Subjects: Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/481792 , uj:43667
- Description: Abstract: The economic growth of countries leads to an increase in energy demand. Energy consumption in most developing countries is likewise increasing due to their economic growth. This has raised a concern about meeting the energy shortage in their communities. The rising alert of air and environmental pollution has created opportunities for electricity access through renewable energy sources as a viable solution to meet the growing energy demand. Therefore, power generation through renewable energy can be a sustainable energy solution for developing countries. Considering the rate of developments in some countries (e.g. Zimbabwe), the extension of power lines from the main grid in a centralized manner to remote and rural areas is still economically challenging. This study addresses how to improve electricity access to rural areas in Zimbabwe. The overall electrification rate of Zimbabwe is 40.42% with approximately 85% urban population and 15% rural population, which has a deficit in rural electricity access. There is therefore a great concern to increase access to electricity in rural and remote areas... , M.Ing. (Electrical Engineering)
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Design of a temperature controllable demand water heater
- Authors: Duff, Craig Andrew
- Date: 2012
- Subjects: Renewable energy sources , Hot-water supply , Solar energy , Heat exchangers
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/256890 , uj:26975
- Description: Abstract: The purpose of this study is to investigate ways to reduce the wastage of electricity and water during domestic hot water applications. Contemporary electric water heaters do not use water and electricity in an efficient manner due to their methods of operation, the placement of the water heater unit away from the point‐of‐use and the lack of direct user‐control. The aim of this study is to consider the feasibility of decentralising water heating to the point‐of‐use by combining a compact heating chamber with the tap, providing scope for the user to be in direct control of the water heating system. This study is necessary in order to support the development of products that improve the efficient use of essential resources, in this case electricity and water. The method used to study the feasibility of user‐controlled decentralised water heating is laboratory‐based experimentation, for which a compact heating chamber and user‐operated controls are designed. This study uses mixed‐methods research to measure both the heating chamber and the user‐control simultaneously. The experimental findings confirm that it is possible to heat flowing water in a compact heating chamber and the user is able to directly control the water heating system. These findings support further research and development of the user‐controlled point‐of‐use water heating concept as a method to save electricity and water. Further research and development should aim to determine to what extent this concept saves water and electricity when compared to existing water heating systems. , M.Tech. (Industrial Design)
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- Authors: Duff, Craig Andrew
- Date: 2012
- Subjects: Renewable energy sources , Hot-water supply , Solar energy , Heat exchangers
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/256890 , uj:26975
- Description: Abstract: The purpose of this study is to investigate ways to reduce the wastage of electricity and water during domestic hot water applications. Contemporary electric water heaters do not use water and electricity in an efficient manner due to their methods of operation, the placement of the water heater unit away from the point‐of‐use and the lack of direct user‐control. The aim of this study is to consider the feasibility of decentralising water heating to the point‐of‐use by combining a compact heating chamber with the tap, providing scope for the user to be in direct control of the water heating system. This study is necessary in order to support the development of products that improve the efficient use of essential resources, in this case electricity and water. The method used to study the feasibility of user‐controlled decentralised water heating is laboratory‐based experimentation, for which a compact heating chamber and user‐operated controls are designed. This study uses mixed‐methods research to measure both the heating chamber and the user‐control simultaneously. The experimental findings confirm that it is possible to heat flowing water in a compact heating chamber and the user is able to directly control the water heating system. These findings support further research and development of the user‐controlled point‐of‐use water heating concept as a method to save electricity and water. Further research and development should aim to determine to what extent this concept saves water and electricity when compared to existing water heating systems. , M.Tech. (Industrial Design)
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Development and performance analysis of a hydraulic hybrid system
- Authors: Wressell, Donovan Leslie
- Date: 2020
- Subjects: Alternative fuel vehicles , Renewable energy sources , Hybrid systems
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/480505 , uj:43501
- Description: Abstract: The automotive industry has for some years considered hydraulic regeneration systems for use in hybrid vehicles; combining the concurrent use of an internal combustion engine and a hydraulic system to reduce fuel consumption and increase performance. To achieve this, the kinetic energy of the vehicle is transformed and stored as hydraulic potential energy in hydraulic accumulators, which use pressurised nitrogen to store the hydraulic potential energy. This transformation, storage and utilization of kinetic energy in vehicles is termed regenerative braking... , M.Ing. (Mechanical Engineering Technology)
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- Authors: Wressell, Donovan Leslie
- Date: 2020
- Subjects: Alternative fuel vehicles , Renewable energy sources , Hybrid systems
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/480505 , uj:43501
- Description: Abstract: The automotive industry has for some years considered hydraulic regeneration systems for use in hybrid vehicles; combining the concurrent use of an internal combustion engine and a hydraulic system to reduce fuel consumption and increase performance. To achieve this, the kinetic energy of the vehicle is transformed and stored as hydraulic potential energy in hydraulic accumulators, which use pressurised nitrogen to store the hydraulic potential energy. This transformation, storage and utilization of kinetic energy in vehicles is termed regenerative braking... , M.Ing. (Mechanical Engineering Technology)
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Development and performance evaluation of a dynamic compressed air energy storage system
- Kabinga, Rolly Karodolan Ndeko
- Authors: Kabinga, Rolly Karodolan Ndeko
- Date: 2020
- Subjects: Compressed air - Storage , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/444225 , uj:38817
- Description: Abstract: Renewable and clean energy are safe sources for powering the world of the future. Transportation sector driven by fossil fuels produces between 15 to 20 % of the greenhouse gas emissions worldwide. Those emissions are threatening to all forms of life and the environment. To mitigate the pollution from fossil fuel, new high energy density storage systems must be developed, and existing ones must be improved. This research focused on compressed air energy storage systems. Because air is an important source of energy, it is one of the most abundant substances on earth, and it is freely available. Its effective use as a clean energy source can significantly contribute to solving the problem of pollution on the planet. The commonly used cylindrical reservoir plays only the role of storing and releasing compressed air to work in a pneumatic network. The performance of this medium relies heavily on its volume, material of construction, and the capacity of the compressor that charges it. In this dissertation, that medium is referred to as the static reservoir. In this work, a thought about a new mechanism that can provide better performance when it comes to storing and releasing the compressed air energy was considered. That mechanism is the dynamic reservoir, a compressed air cylinder fitted with a piston, and a spring of a specific stiffness... , M.Eng. (Mechanical Engineering)
- Full Text:
- Authors: Kabinga, Rolly Karodolan Ndeko
- Date: 2020
- Subjects: Compressed air - Storage , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/444225 , uj:38817
- Description: Abstract: Renewable and clean energy are safe sources for powering the world of the future. Transportation sector driven by fossil fuels produces between 15 to 20 % of the greenhouse gas emissions worldwide. Those emissions are threatening to all forms of life and the environment. To mitigate the pollution from fossil fuel, new high energy density storage systems must be developed, and existing ones must be improved. This research focused on compressed air energy storage systems. Because air is an important source of energy, it is one of the most abundant substances on earth, and it is freely available. Its effective use as a clean energy source can significantly contribute to solving the problem of pollution on the planet. The commonly used cylindrical reservoir plays only the role of storing and releasing compressed air to work in a pneumatic network. The performance of this medium relies heavily on its volume, material of construction, and the capacity of the compressor that charges it. In this dissertation, that medium is referred to as the static reservoir. In this work, a thought about a new mechanism that can provide better performance when it comes to storing and releasing the compressed air energy was considered. That mechanism is the dynamic reservoir, a compressed air cylinder fitted with a piston, and a spring of a specific stiffness... , M.Eng. (Mechanical Engineering)
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Dynamic model and control of power converters for grid connected renewable energy systems
- Nnachi, A. F., Nicolae, Dan-Valentin, Jimoh, A. A.
- Authors: Nnachi, A. F. , Nicolae, Dan-Valentin , Jimoh, A. A.
- Date: 2008
- Subjects: Electric current converters , Renewable energy sources
- Language: English
- Type: Conference procedings
- Identifier: http://hdl.handle.net/10210/20449 , uj:16099 , Citation: Nnachi, A.F., Nicolae, D.V. & Jimoh, A.A. 2008. Dynamic model and control of power converters for grid connected renewable energy systems. Proceedings of the Second IASTED Africa Conference Power and Energy Sysyems (Africa PES 2008), 8-10 September, 2008, Gaborone, Botswana.
- Description: Abstract: In order to investigate certain dynamic events of a grid connected renewable energy system (RES), a systematic model and control is developed. The RES with its converter is taken as a controlled dc current source and the grid side converter model is based on approximate power balance of the dc-link and the ac-side. Here an AC-side decoupled current controller in dq reference frame and simplified net dc-bus voltage controllers are implied. Among different dynamic events that is studied, the response of the system during three-phase to ground fault, step change in reference DC voltage, active and reactive power change are studied and presented.
- Full Text:
- Authors: Nnachi, A. F. , Nicolae, Dan-Valentin , Jimoh, A. A.
- Date: 2008
- Subjects: Electric current converters , Renewable energy sources
- Language: English
- Type: Conference procedings
- Identifier: http://hdl.handle.net/10210/20449 , uj:16099 , Citation: Nnachi, A.F., Nicolae, D.V. & Jimoh, A.A. 2008. Dynamic model and control of power converters for grid connected renewable energy systems. Proceedings of the Second IASTED Africa Conference Power and Energy Sysyems (Africa PES 2008), 8-10 September, 2008, Gaborone, Botswana.
- Description: Abstract: In order to investigate certain dynamic events of a grid connected renewable energy system (RES), a systematic model and control is developed. The RES with its converter is taken as a controlled dc current source and the grid side converter model is based on approximate power balance of the dc-link and the ac-side. Here an AC-side decoupled current controller in dq reference frame and simplified net dc-bus voltage controllers are implied. Among different dynamic events that is studied, the response of the system during three-phase to ground fault, step change in reference DC voltage, active and reactive power change are studied and presented.
- Full Text:
Effect of nutrient addition during anaerobic digestion of potato peels and maize husk
- Ramatsa, Ishmael, Sibiya, Noxolo, Huberts, Roberth
- Authors: Ramatsa, Ishmael , Sibiya, Noxolo , Huberts, Roberth
- Date: 2014
- Subjects: Anaerobic bacteria , Renewable energy sources , Biomass energy , Biogas
- Type: Article
- Identifier: uj:5091 , http://hdl.handle.net/10210/13681
- Description: The composition of the substrate and nutrients addition plays a very significant role during the production of the biogas. For this reason this paper tries to evaluate the effect of nutrients addition during biogas production under anaerobic conditions. Potato peels wastes and maize husk were anaerobically digested in a 5 liter scale reactor at mesophilic conditions (32 o C). The characteristics of the potato peels were and maize husk are presented in Table 1. The results obtained indicated that the addition of the nutrients during anaerobic digestion has an influence on the biogas production, meanwhile methane content in biogas varied from 48 to 64%.
- Full Text:
- Authors: Ramatsa, Ishmael , Sibiya, Noxolo , Huberts, Roberth
- Date: 2014
- Subjects: Anaerobic bacteria , Renewable energy sources , Biomass energy , Biogas
- Type: Article
- Identifier: uj:5091 , http://hdl.handle.net/10210/13681
- Description: The composition of the substrate and nutrients addition plays a very significant role during the production of the biogas. For this reason this paper tries to evaluate the effect of nutrients addition during biogas production under anaerobic conditions. Potato peels wastes and maize husk were anaerobically digested in a 5 liter scale reactor at mesophilic conditions (32 o C). The characteristics of the potato peels were and maize husk are presented in Table 1. The results obtained indicated that the addition of the nutrients during anaerobic digestion has an influence on the biogas production, meanwhile methane content in biogas varied from 48 to 64%.
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Energy sustainability : Fischer-Tropsch synthesis over mesoporous material supported ruthenium
- Okonye, Leonard Uchejim Odikowu
- Authors: Okonye, Leonard Uchejim Odikowu
- Date: 2018
- Subjects: Fischer-Tropsch process , Renewable energy sources , Ruthenium
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/401528 , uj:33562
- Description: Abstract : Sustainable energy has remained a challenge across the world due to over-dependence on fossil fuels. This has resulted in energy crises in terms of the shortfall in supply, global price instability and continual adjustment of energy policies. The issues of environmental degradation and the quest for a long-term solution to the importation of fossils fuels necessitated the call for relentless engagement and development of sustainable alternative sources of energy that can also serve to bridge the unavoidable gap between demands and supply. Amongst the alternative and sustainable sources of energy generation is the Fischer-Tropsch (FT) synthesis, which could play a very important role, if not to a great extent, an improvement on the efficiency of fossil fuel reserve exploitation and utilisation. The process of Fischer-Tropsch Synthesis (FTS) produce liquid hydrocarbons generated from the synthesis gases (CO, H2), which rely on the potential of carbon monoxide to exchange hydrogen for oxygen when a catalyst is present. The FT process conversion reaction more often than not is heterogeneously catalysed by an active metal phase, dispersed on a support which might contribute to the catalytic activity, and is considered a surface-catalysed polymerization reaction. However, surface scientists have shown that in addition to the actual FT catalysis which generally takes place on the metal surfaces, the nature of the metal/oxide interfaces still plays a role in the reaction. Hence, the need for a suitable and stable support system with active surface sites for proper metal dispersion. This will be suitable for high FTS activity, achieved by the use of nano-sized particles and novel meso-structured materials. The arrival of novel meso-structured materials can facilitate the design of heterogeneous catalysts and promises to have the potential for FT synthesis, because of their tunable porous interconnected networks that have a large surface area (with a pore size of 2 - 50nm) and uniform pore size distribution. This is because of the metal-support interaction in smaller particles that is noticeably stronger compared to larger particles, which could lead to high FTS activity through the use of nano-sized particles, and periodic mesoporous supports... , Ph.D. (Chemistry)
- Full Text:
- Authors: Okonye, Leonard Uchejim Odikowu
- Date: 2018
- Subjects: Fischer-Tropsch process , Renewable energy sources , Ruthenium
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/401528 , uj:33562
- Description: Abstract : Sustainable energy has remained a challenge across the world due to over-dependence on fossil fuels. This has resulted in energy crises in terms of the shortfall in supply, global price instability and continual adjustment of energy policies. The issues of environmental degradation and the quest for a long-term solution to the importation of fossils fuels necessitated the call for relentless engagement and development of sustainable alternative sources of energy that can also serve to bridge the unavoidable gap between demands and supply. Amongst the alternative and sustainable sources of energy generation is the Fischer-Tropsch (FT) synthesis, which could play a very important role, if not to a great extent, an improvement on the efficiency of fossil fuel reserve exploitation and utilisation. The process of Fischer-Tropsch Synthesis (FTS) produce liquid hydrocarbons generated from the synthesis gases (CO, H2), which rely on the potential of carbon monoxide to exchange hydrogen for oxygen when a catalyst is present. The FT process conversion reaction more often than not is heterogeneously catalysed by an active metal phase, dispersed on a support which might contribute to the catalytic activity, and is considered a surface-catalysed polymerization reaction. However, surface scientists have shown that in addition to the actual FT catalysis which generally takes place on the metal surfaces, the nature of the metal/oxide interfaces still plays a role in the reaction. Hence, the need for a suitable and stable support system with active surface sites for proper metal dispersion. This will be suitable for high FTS activity, achieved by the use of nano-sized particles and novel meso-structured materials. The arrival of novel meso-structured materials can facilitate the design of heterogeneous catalysts and promises to have the potential for FT synthesis, because of their tunable porous interconnected networks that have a large surface area (with a pore size of 2 - 50nm) and uniform pore size distribution. This is because of the metal-support interaction in smaller particles that is noticeably stronger compared to larger particles, which could lead to high FTS activity through the use of nano-sized particles, and periodic mesoporous supports... , Ph.D. (Chemistry)
- Full Text:
Enhancing strategies to improve hydroelectricity generation
- Authors: Klassie, Unathi
- Date: 2020
- Subjects: Electric power production , Renewable energy sources , Hydroelectric power plants , Sewage disposal plants - South Africa , Water treatment plants - South Africa , Fluid dynamics - Mathematical models
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/445001 , uj:38915
- Description: Abstract: Renewable energy sources are evolving fundamental components of wastewater treatment plants. The intermittent and increasing adoption of renewable energy sources supports emerging studies undertaken in the demand and supply of energy. Hydropower is a significant renewable energy source globally. A sustainable application of hydropower technology requires effective planning, design and implementation to manage or mitigate challenges. In South Africa the prevalent source of energy generation is through fossil fuels and solid waste. Overdependence on energy demand based on fossil fuels for everyday capacity of the wastewater treatment plants is unsustainable. Affordability, stability, reliability, and accessibility of electricity generated by alternative renewable energy resources are fundamental for ensuring sustainability in wastewater treatment plants... , M.Ing. (Engineering Management)
- Full Text:
- Authors: Klassie, Unathi
- Date: 2020
- Subjects: Electric power production , Renewable energy sources , Hydroelectric power plants , Sewage disposal plants - South Africa , Water treatment plants - South Africa , Fluid dynamics - Mathematical models
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/445001 , uj:38915
- Description: Abstract: Renewable energy sources are evolving fundamental components of wastewater treatment plants. The intermittent and increasing adoption of renewable energy sources supports emerging studies undertaken in the demand and supply of energy. Hydropower is a significant renewable energy source globally. A sustainable application of hydropower technology requires effective planning, design and implementation to manage or mitigate challenges. In South Africa the prevalent source of energy generation is through fossil fuels and solid waste. Overdependence on energy demand based on fossil fuels for everyday capacity of the wastewater treatment plants is unsustainable. Affordability, stability, reliability, and accessibility of electricity generated by alternative renewable energy resources are fundamental for ensuring sustainability in wastewater treatment plants... , M.Ing. (Engineering Management)
- Full Text:
High output gain modified DC-DC Cuk converters for renewable energy applications
- Authors: Adepoju, Webster Oluwafemi
- Date: 2017
- Subjects: DC-to-DC converters , Distributed generation of electric power , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280173 , uj:30101
- Description: M.Ing. (Electrical Engineering) , Abstract: Renewable energy application has become a focal point of most researches in recent times. This is motivated by the need to achieve an eco-friendly atmosphere and to mitigate the environmental hazards such as global warming and climate change which are drawbacks of conventional energy generation. High power application is equally on fast rising demands especially for industrial use making conventional DC-DC converters less applicable. Three High gain Modified DC-DC Cuk converters were proposed in this thesis. Voltage Lift Technique (VLT) is used to increase the voltage gain of the proposed converter. The converters produced amplified versions of the supply voltage by the inclusion of passive components and switch capacitor network. In perspective view, by a simple addition of diodes, capacitors and inductor to the classical Cuk circuit, the first, second and third proposed high gain modified Cuk circuits generated voltage gain of 10, 20 and 29 respectively when the switching gate is driven at 90% duty ratio. MATLAB/Simulink and Lt-spice simulations validate the numerical analysis and prototype results for different values of the duty ratio.
- Full Text:
- Authors: Adepoju, Webster Oluwafemi
- Date: 2017
- Subjects: DC-to-DC converters , Distributed generation of electric power , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280173 , uj:30101
- Description: M.Ing. (Electrical Engineering) , Abstract: Renewable energy application has become a focal point of most researches in recent times. This is motivated by the need to achieve an eco-friendly atmosphere and to mitigate the environmental hazards such as global warming and climate change which are drawbacks of conventional energy generation. High power application is equally on fast rising demands especially for industrial use making conventional DC-DC converters less applicable. Three High gain Modified DC-DC Cuk converters were proposed in this thesis. Voltage Lift Technique (VLT) is used to increase the voltage gain of the proposed converter. The converters produced amplified versions of the supply voltage by the inclusion of passive components and switch capacitor network. In perspective view, by a simple addition of diodes, capacitors and inductor to the classical Cuk circuit, the first, second and third proposed high gain modified Cuk circuits generated voltage gain of 10, 20 and 29 respectively when the switching gate is driven at 90% duty ratio. MATLAB/Simulink and Lt-spice simulations validate the numerical analysis and prototype results for different values of the duty ratio.
- Full Text:
Hybrid renewable energy-based facility location : a Geographical Information System (GIS) integrated multi-criteria decision-making (MCDM) approach
- Authors: Adedeji, Paul Adeola
- Date: 2020
- Subjects: Hybrid power , Renewable energy sources , Geographic information systems , Energy facilities - Location , Multiple criteria decision making
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/481988 , uj:43691
- Description: Abstract: Site suitability analysis with geographical information system multi-criteria decision-making (GIS-MCDM) techniques forms a significant process in wind and solar energy exploration at the utility-scale level. The process unveils viable sites for exploration, however, few is known about the variability investigation of these sites before physical site development. Besides, soft computing techniques like Adaptive Neurofuzzy Inference System (ANFIS) at standalone and hybrid with population-based optimization models like Particle Swarm Optimization (PSO), and Genetic Algorithm (GA), have been effective in understanding the variability and intermittency in wind and solar resources. Hence, their integration with GIS-based site suitability analysis for variability investigation in viable sites for utility-scale wind and solar resources offers a high potential for strategic and operational resource planning. Pilot studies that investigate the effectiveness of the developed standalone ANFIS, GA-ANFIS, and PSO-ANFIS models were carried out and all these present PSO-ANFIS as highly effective, however at a higher computational time(CT). Furthermore, site-specific investigations on wind and solar resources predictions using standalone ANFIS and PSO-ANFIS models were performed. First, the significance of data clustering (Fuzzy-c-means (FCM), Subtractive Clustering (SC), and Grid Partitioning (GP)) on the two models using wind power time-series data was investigated. The SCbased PSO-ANFIS model performed best among the three models with root mean square error (RMSE)= 0.127, mean absolute deviation (MAD) = 0.078, mean absolute percentage error (MAPE)= 28.11, relative mean bias error (rMBE) of 0.190 and Variance Accounted For (VAF) of 94.311, and CT= 47.21 secs. Second, the effectiveness of GA and PSO-based ANFIS models on power forecast for three wind turbine generators(WTG) was performed and the PSO-ANFIS model performed better on the first WTG with RMSE= 0.180, MAD= 0.091, R2= 0.914, and CT= 702.3 secs. In the same study, further investigations on the feasibility of embedded generation for powering a nearby agricultural farm was carried out. Similarly, wavelet-based ANFIS models were investigated on solar radiation forecast and it was established that standalone models performed better than wavelet hybrids, though many factors can be responsible for this. With the effectiveness of the soft computing model assured, they were used for resource variability investigation in candidate viable sites obtained from GIS-based site suitability analysis for wind and solar energy in the Eastern and Western Cape Provinces respectively. Twenty years historical satellite data for wind and global horizontal irradiance (GHI) obtained from the National Aeronautics and Space... , Ph.D.
- Full Text:
- Authors: Adedeji, Paul Adeola
- Date: 2020
- Subjects: Hybrid power , Renewable energy sources , Geographic information systems , Energy facilities - Location , Multiple criteria decision making
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/481988 , uj:43691
- Description: Abstract: Site suitability analysis with geographical information system multi-criteria decision-making (GIS-MCDM) techniques forms a significant process in wind and solar energy exploration at the utility-scale level. The process unveils viable sites for exploration, however, few is known about the variability investigation of these sites before physical site development. Besides, soft computing techniques like Adaptive Neurofuzzy Inference System (ANFIS) at standalone and hybrid with population-based optimization models like Particle Swarm Optimization (PSO), and Genetic Algorithm (GA), have been effective in understanding the variability and intermittency in wind and solar resources. Hence, their integration with GIS-based site suitability analysis for variability investigation in viable sites for utility-scale wind and solar resources offers a high potential for strategic and operational resource planning. Pilot studies that investigate the effectiveness of the developed standalone ANFIS, GA-ANFIS, and PSO-ANFIS models were carried out and all these present PSO-ANFIS as highly effective, however at a higher computational time(CT). Furthermore, site-specific investigations on wind and solar resources predictions using standalone ANFIS and PSO-ANFIS models were performed. First, the significance of data clustering (Fuzzy-c-means (FCM), Subtractive Clustering (SC), and Grid Partitioning (GP)) on the two models using wind power time-series data was investigated. The SCbased PSO-ANFIS model performed best among the three models with root mean square error (RMSE)= 0.127, mean absolute deviation (MAD) = 0.078, mean absolute percentage error (MAPE)= 28.11, relative mean bias error (rMBE) of 0.190 and Variance Accounted For (VAF) of 94.311, and CT= 47.21 secs. Second, the effectiveness of GA and PSO-based ANFIS models on power forecast for three wind turbine generators(WTG) was performed and the PSO-ANFIS model performed better on the first WTG with RMSE= 0.180, MAD= 0.091, R2= 0.914, and CT= 702.3 secs. In the same study, further investigations on the feasibility of embedded generation for powering a nearby agricultural farm was carried out. Similarly, wavelet-based ANFIS models were investigated on solar radiation forecast and it was established that standalone models performed better than wavelet hybrids, though many factors can be responsible for this. With the effectiveness of the soft computing model assured, they were used for resource variability investigation in candidate viable sites obtained from GIS-based site suitability analysis for wind and solar energy in the Eastern and Western Cape Provinces respectively. Twenty years historical satellite data for wind and global horizontal irradiance (GHI) obtained from the National Aeronautics and Space... , Ph.D.
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Hybrid-renewable energy : a methodology for identifying communities that can benefit from off-grid systems
- Authors: Kekana, Hlologelo Maesela
- Date: 2020
- Subjects: Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/452518 , uj:39914
- Description: Abstract: In a world of increasing demand for electrical energy, renewable energy is Africa’s calling-card to come to the forefront of renewable energy generation. Solar energy can be harnessed in different ways; and the technology to increase the energy output efficiency continues to develop daily, growing exponentially towards achieving efficiency levels, which can substantiate its greater use in everyday lives. This study has attempted to model a hybrid-energy power plant that utilises solar PV and wind energy to power the electricity demand of a community in South Africa. The hybrid-energy system operates with the support of a Battery Energy Storage (BES) system, together with a diesel generator, in order to access an energy supply whenever solar or wind energy are not harnessed... , M.Ing. (Mechanical Engineering Science)
- Full Text:
- Authors: Kekana, Hlologelo Maesela
- Date: 2020
- Subjects: Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/452518 , uj:39914
- Description: Abstract: In a world of increasing demand for electrical energy, renewable energy is Africa’s calling-card to come to the forefront of renewable energy generation. Solar energy can be harnessed in different ways; and the technology to increase the energy output efficiency continues to develop daily, growing exponentially towards achieving efficiency levels, which can substantiate its greater use in everyday lives. This study has attempted to model a hybrid-energy power plant that utilises solar PV and wind energy to power the electricity demand of a community in South Africa. The hybrid-energy system operates with the support of a Battery Energy Storage (BES) system, together with a diesel generator, in order to access an energy supply whenever solar or wind energy are not harnessed... , M.Ing. (Mechanical Engineering Science)
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Managing the design and development of high performance buildings through integrated design
- Authors: Beetge, Willem Gerhardus
- Date: 2016
- Subjects: Sustainable buildings - Design and construction , Sustainable design , Buildings - Energy conservation , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213042 , uj:21070
- Description: Abstract: The world population has doubled during the past 45 years [9]. This has created a huge increase in the demand for natural resources. Extremely high levels of carbon dioxide emissions have been witnessed during the last decade. Natural resources like plantations, construction aggregate, coal, oil, water, and agriculture land have come under extreme pressure due to the high demand for these and other scarce resources. During the last two to three decades there have been increased efforts to reduce greenhouse gasses, to save and to protect water sources, and to use materials and products sparingly. Phrases like green buildings, sustainable construction and high-performance buildings are being used more widely amongst role players in the construction industry. High-performance buildings also referred to as green buildings or sustainable buildings are designed and developed with the aim of reducing the demand on fossil fuel energy and potable water. The indoor environmental quality, another major aspect of highperformance buildings, ensures that building occupants show signs of being healthier and more productive. To ensure the successful implementation of green building design and development, some important aspects like design implementation strategies, integrated design, building life cycle assessment, and passive design have to be considered. Management of the design and development processes also requires some technical knowledge of sustainability. The main barriers that prevent the implementation of the development of high-performance buildings have to be addressed and removed. The urgent need for developing energy-efficient and waterefficient buildings has to be acknowledged and supported by senior management and executive officers of organisations involved in building development. The development of highperformance buildings is most effectively achieved through a process referred to as integrated design. This process requires the early involvement of all relevant role players. The development of high-performance buildings through the process of integrated design is regarded by a number of experts as two inseparable concepts. It is therefore essential that managers and leaders who are involved in the development of high-performance buildings are equipped with knowledge and skills in the principles of sustainability and integrated design. , M.Ing. (Engineering Management)
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- Authors: Beetge, Willem Gerhardus
- Date: 2016
- Subjects: Sustainable buildings - Design and construction , Sustainable design , Buildings - Energy conservation , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213042 , uj:21070
- Description: Abstract: The world population has doubled during the past 45 years [9]. This has created a huge increase in the demand for natural resources. Extremely high levels of carbon dioxide emissions have been witnessed during the last decade. Natural resources like plantations, construction aggregate, coal, oil, water, and agriculture land have come under extreme pressure due to the high demand for these and other scarce resources. During the last two to three decades there have been increased efforts to reduce greenhouse gasses, to save and to protect water sources, and to use materials and products sparingly. Phrases like green buildings, sustainable construction and high-performance buildings are being used more widely amongst role players in the construction industry. High-performance buildings also referred to as green buildings or sustainable buildings are designed and developed with the aim of reducing the demand on fossil fuel energy and potable water. The indoor environmental quality, another major aspect of highperformance buildings, ensures that building occupants show signs of being healthier and more productive. To ensure the successful implementation of green building design and development, some important aspects like design implementation strategies, integrated design, building life cycle assessment, and passive design have to be considered. Management of the design and development processes also requires some technical knowledge of sustainability. The main barriers that prevent the implementation of the development of high-performance buildings have to be addressed and removed. The urgent need for developing energy-efficient and waterefficient buildings has to be acknowledged and supported by senior management and executive officers of organisations involved in building development. The development of highperformance buildings is most effectively achieved through a process referred to as integrated design. This process requires the early involvement of all relevant role players. The development of high-performance buildings through the process of integrated design is regarded by a number of experts as two inseparable concepts. It is therefore essential that managers and leaders who are involved in the development of high-performance buildings are equipped with knowledge and skills in the principles of sustainability and integrated design. , M.Ing. (Engineering Management)
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Mathematical modelling for biogas production
- Authors: Matheri, Anthony Njuguna
- Date: 2016
- Subjects: Sewage - Purification - Anaerobic treatment , Sewage - Purification - Mathematical models , Renewable energy sources , Biomass energy , Biogas
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213006 , uj:21066
- Description: Abstract: The main focus of this dissertation is the experimental, modelling and simulation of anaerobic digestion processes from pilot bio-digesters. For this purpose, biochemical kinetic models were utilized together with corresponding simulation software; DYNOCHEM. By application of the anaerobic digestion (AD), different parameters have been investigated and simulated including adjustments of the process model and corresponding modifications. To validate the process model, the modelled data was compared with experimental monitored laboratory results. Bio-chemical kinetics modelling was applied as a systematic tool in order to support the process design and optimization of a demonstration of the biogas processes which constitutes the main scientific framework and background of this dissertation. Monitored laboratory-scale biogas production data were used for parameter calibration in order to predict plant performance. The calibration focused on the influent characterization of both substrates and on selection of kinetic of the coefficients in order to generate a uniform set of parameters which are applicable for the simulation of codigestion. In this study, it was observed that the experiment work under laboratory scale using conventional bio-methane potential (BMP) analyzers under mesophilic optimum temperature of 35 oC and 37 oC, and pH of 7 for co-digestion of organic fraction of municipal solid waste (OFMSW) with cow dung and manure with grass clippings. The substrate characterization moisture content ranged from 60-95%, volatile content 55-95%, total solid 10-90% and carbon to nitrogen ratio 16-20 for manure and 5-15 for OFMSW. All trace elements concentration were below the threshold of 32 mg/l that leads to inhibition of micro-organisms activity. The rate of conversion increased with retention time. According to the findings, 54-62% of methane composition was evaluated. The kinetics constant evaluated ranged from 0.009-0.35 d-1 and coefficient of determination (R2) ranged from 0.9989-0.9998. The Michaelis-Menten and Monod models provided goodness of fit of 0.9997 with confidential level of 95%. The simulations confirmed that the rate of conversion increased as temperature increases and conversion of reactants increased with retention time, until an equilibrium state was reached. The AD process modelling using DYNOCHEM was successfully modified and implemented to account for unsteady operation which is generally the case of full-scale reactor by developed methodology. , M.Tech. (Chemical Engineering)
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- Authors: Matheri, Anthony Njuguna
- Date: 2016
- Subjects: Sewage - Purification - Anaerobic treatment , Sewage - Purification - Mathematical models , Renewable energy sources , Biomass energy , Biogas
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213006 , uj:21066
- Description: Abstract: The main focus of this dissertation is the experimental, modelling and simulation of anaerobic digestion processes from pilot bio-digesters. For this purpose, biochemical kinetic models were utilized together with corresponding simulation software; DYNOCHEM. By application of the anaerobic digestion (AD), different parameters have been investigated and simulated including adjustments of the process model and corresponding modifications. To validate the process model, the modelled data was compared with experimental monitored laboratory results. Bio-chemical kinetics modelling was applied as a systematic tool in order to support the process design and optimization of a demonstration of the biogas processes which constitutes the main scientific framework and background of this dissertation. Monitored laboratory-scale biogas production data were used for parameter calibration in order to predict plant performance. The calibration focused on the influent characterization of both substrates and on selection of kinetic of the coefficients in order to generate a uniform set of parameters which are applicable for the simulation of codigestion. In this study, it was observed that the experiment work under laboratory scale using conventional bio-methane potential (BMP) analyzers under mesophilic optimum temperature of 35 oC and 37 oC, and pH of 7 for co-digestion of organic fraction of municipal solid waste (OFMSW) with cow dung and manure with grass clippings. The substrate characterization moisture content ranged from 60-95%, volatile content 55-95%, total solid 10-90% and carbon to nitrogen ratio 16-20 for manure and 5-15 for OFMSW. All trace elements concentration were below the threshold of 32 mg/l that leads to inhibition of micro-organisms activity. The rate of conversion increased with retention time. According to the findings, 54-62% of methane composition was evaluated. The kinetics constant evaluated ranged from 0.009-0.35 d-1 and coefficient of determination (R2) ranged from 0.9989-0.9998. The Michaelis-Menten and Monod models provided goodness of fit of 0.9997 with confidential level of 95%. The simulations confirmed that the rate of conversion increased as temperature increases and conversion of reactants increased with retention time, until an equilibrium state was reached. The AD process modelling using DYNOCHEM was successfully modified and implemented to account for unsteady operation which is generally the case of full-scale reactor by developed methodology. , M.Tech. (Chemical Engineering)
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Maximizing demand response aggregator compensation through optimal RES utilization : aggregation in Johannesburg, South Africa
- Authors: Essiet, Ima O. , Sun, Yanxia
- Date: 2020
- Subjects: Demand response , Day-ahead market , Renewable energy sources
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/415946 , uj:35165 , Citation: Essiet, I.O., Sun, Y. Maximizing demand response aggregator compensation through optimal RES utilization : aggregation in Johannesburg, South Africa. DOI: 10.3390/app10020594
- Description: Abstract: , This paper examines the role of demand response aggregators in minimizing the cost of electricity generation by distribution utilities in a day-ahead electricity market. In this paper, 2500 standard South African homes are considered as end users. Five clusters (and aggregators) are considered with 500 homes in each cluster. Two cases are analysed: (1) Utilization of renewable energy sources (RES) is implemented by the distribution supply operator (DSO), where it meets excess demand for end users during peak hours by purchasing electricity from the renewable sources of the energy market, and (2) Utilization of RES is implemented by end users alone, and it is assumed that every household has one plug-in electric vehicle (PEV). The aggregators then compete with each other for the most cost-effective energy usage profile; the aggregator with the least energy demand wins the bid. In both cases, energy pricing is estimated according to the day-ahead energy market. A typical day during winter in Johannesburg is considered for the simulation using a genetic algorithm (GA). Results obtained demonstrate the effectiveness of demand response aggregators in maximizing the benefits on both sides of the electricity supply chain.
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- Authors: Essiet, Ima O. , Sun, Yanxia
- Date: 2020
- Subjects: Demand response , Day-ahead market , Renewable energy sources
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/415946 , uj:35165 , Citation: Essiet, I.O., Sun, Y. Maximizing demand response aggregator compensation through optimal RES utilization : aggregation in Johannesburg, South Africa. DOI: 10.3390/app10020594
- Description: Abstract: , This paper examines the role of demand response aggregators in minimizing the cost of electricity generation by distribution utilities in a day-ahead electricity market. In this paper, 2500 standard South African homes are considered as end users. Five clusters (and aggregators) are considered with 500 homes in each cluster. Two cases are analysed: (1) Utilization of renewable energy sources (RES) is implemented by the distribution supply operator (DSO), where it meets excess demand for end users during peak hours by purchasing electricity from the renewable sources of the energy market, and (2) Utilization of RES is implemented by end users alone, and it is assumed that every household has one plug-in electric vehicle (PEV). The aggregators then compete with each other for the most cost-effective energy usage profile; the aggregator with the least energy demand wins the bid. In both cases, energy pricing is estimated according to the day-ahead energy market. A typical day during winter in Johannesburg is considered for the simulation using a genetic algorithm (GA). Results obtained demonstrate the effectiveness of demand response aggregators in maximizing the benefits on both sides of the electricity supply chain.
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Modified SEPIC DC-to-DC boost converters with high output-gain configuration for renewable applications
- Authors: Muranda, Charles
- Date: 2018
- Subjects: SPICE (Computer file) , MATLAB , SIMULINK , Renewable energy sources , Electric circuit analysis , Low voltage integrated circuits , Simulation methods , Computer simulation - Software
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280529 , uj:30145
- Description: Abstract: Renewable energy sourcing has increased popularity these days because of the issues with burning fossil fuels as an energy sources and as a way of combating global gas emission. Thus, renewable energy has become the principal focus of most energy-based researches. Most of the sources energy is however produce electricity with low voltage levels and grid connection requires very high voltage electricity for efficient transmission. This calls for step up converters with very high voltage gains to synchronize the sourced electricity with the grid. Also, the popular boost converters do not have high enough step up voltage gain as their efficiency and effectiveness degrades with increasing switch duty ratio. This research thus introduces a higher voltage gain topologies that can be alternatives to the voltage stepping up problem in renewable energy systems. Three different topologies that are modifications of the SEPIC converter are presented in this research and each of the converters has a different voltage gain of 10, 20 and 29 times the input voltage at 0.9 duty ratio. Theoretical analysis will be used to derive the gain of the converters. Simulations with the Matlab/Simulink and SPICE simulation software’s will be used to verify the theoretical results. Hardware prototypes will be presented to demonstrate the workings of the prototypes. , M.Ing. (Electrical Engineering)
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- Authors: Muranda, Charles
- Date: 2018
- Subjects: SPICE (Computer file) , MATLAB , SIMULINK , Renewable energy sources , Electric circuit analysis , Low voltage integrated circuits , Simulation methods , Computer simulation - Software
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280529 , uj:30145
- Description: Abstract: Renewable energy sourcing has increased popularity these days because of the issues with burning fossil fuels as an energy sources and as a way of combating global gas emission. Thus, renewable energy has become the principal focus of most energy-based researches. Most of the sources energy is however produce electricity with low voltage levels and grid connection requires very high voltage electricity for efficient transmission. This calls for step up converters with very high voltage gains to synchronize the sourced electricity with the grid. Also, the popular boost converters do not have high enough step up voltage gain as their efficiency and effectiveness degrades with increasing switch duty ratio. This research thus introduces a higher voltage gain topologies that can be alternatives to the voltage stepping up problem in renewable energy systems. Three different topologies that are modifications of the SEPIC converter are presented in this research and each of the converters has a different voltage gain of 10, 20 and 29 times the input voltage at 0.9 duty ratio. Theoretical analysis will be used to derive the gain of the converters. Simulations with the Matlab/Simulink and SPICE simulation software’s will be used to verify the theoretical results. Hardware prototypes will be presented to demonstrate the workings of the prototypes. , M.Ing. (Electrical Engineering)
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Optimal energy management of microgrids incorporating hybrid energy storage systems
- Authors: Gbadegesin, Azizat Olusola
- Date: 2020
- Subjects: Energy storage , Renewable energy sources , Microgrids (Smart power grids)
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/480408 , uj:43489
- Description: Abstract: An increase in the search for electricity from renewable energy sources (RES) like solar, wind, tidal and geothermal sources has become important in improving access to reliable and affordable energy worldwide. The challenge with their use, however, is that the electricity supply is intermittent, thus posing a challenge to energy system planners. Storage systems may be incorporated within the power system to address this intermittency and handle the varying power surpluses or deficits provided by these renewable sources. Although it has been established that storage systems can improve the reliability of a network, encourage the penetration of RES and reduce peak demand, a major challenge is the high capital costs involved. Thus, this thesis presents three mathematical models to investigate the techno-economic aspects of hybrid energy storage systems (HESS) operating within a power network. The first model, which is reported in Chapter Three, exploits the complementary characteristics of each storage system forming a part of the HESS while considering degradation in energy output. The results present an index, the Levelised Cost of Hybrid Energy Storage Systems (LCOHESS) which informs proper decision making for the HESS configuration to be adopted considering technoeconomic constraints Similarly, the second model, in Chapter Four, examines the multiple revenue streams offered by hybrid storage systems in a prosumer microgrid in an attempt to make a favourable case for the adoption of storage systems... , D.Phil. (Electrical and Electronic Engineering Science)
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- Authors: Gbadegesin, Azizat Olusola
- Date: 2020
- Subjects: Energy storage , Renewable energy sources , Microgrids (Smart power grids)
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/480408 , uj:43489
- Description: Abstract: An increase in the search for electricity from renewable energy sources (RES) like solar, wind, tidal and geothermal sources has become important in improving access to reliable and affordable energy worldwide. The challenge with their use, however, is that the electricity supply is intermittent, thus posing a challenge to energy system planners. Storage systems may be incorporated within the power system to address this intermittency and handle the varying power surpluses or deficits provided by these renewable sources. Although it has been established that storage systems can improve the reliability of a network, encourage the penetration of RES and reduce peak demand, a major challenge is the high capital costs involved. Thus, this thesis presents three mathematical models to investigate the techno-economic aspects of hybrid energy storage systems (HESS) operating within a power network. The first model, which is reported in Chapter Three, exploits the complementary characteristics of each storage system forming a part of the HESS while considering degradation in energy output. The results present an index, the Levelised Cost of Hybrid Energy Storage Systems (LCOHESS) which informs proper decision making for the HESS configuration to be adopted considering technoeconomic constraints Similarly, the second model, in Chapter Four, examines the multiple revenue streams offered by hybrid storage systems in a prosumer microgrid in an attempt to make a favourable case for the adoption of storage systems... , D.Phil. (Electrical and Electronic Engineering Science)
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Optimal operation and control of renewable energy powered reverse osmosis desalination system
- Authors: Okampo, Ewaoche John
- Date: 2020
- Subjects: Saline water conversion - Reverse osmosis process , Renewable energy sources
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/481956 , uj:43687
- Description: Ph.D. , Abstract: Desalination is a viable solution to meet water scarcity but is regarded as cost-intensive. The reverse osmosis (RO) technique of desalination is commonly used for its cost-effectiveness as compared to other methods but still considered energy-intensive. Conventional fossil energy sources emit carbon gas, which has environmental and cost implications, while renewable energy sources are limited by intermittency. This study formulates mathematical optimization models used to determine the optimal energy mix to power a reverse osmosis desalination unit. The models are formulated to ensure balance between power supply and demand, water demand and water produced, cost functions, and a time-of-use demand response (TOU DR) program. The cost functions include carbon emission cost, DR cost and components cost. The objective of The optimization models is to minimize the annualized cost of system (ACS), levelized cost of energy (LCOE), unit cost of water (COW) and carbon emissions, while maximizing the quantity of freshwater production subject to different economic and system reliability constraints. The first model has an energy mix of grid power, a diesel generator and a photovoltaic (PV) module to supply an RO desalination unit with the objective of maximizing freshwater production at minimal cost. Also considered is the impact of DR and its cost on the quantity of water produced at different hours of the day, and the unit cost of freshwater. Three cases of optimal sizing approaches were compared. Case 1 is a system with only grid power and a diesel generator as energy sources; Case 2 has PV power incorporated in the energy supply mix, while Case 3 has the three energy sources and a TOU DR program on the demand side. The result shows that Case 3 turns out the highest freshwater production (1 520 m3/day) at low cost of (1.33 $/m3) when compared to Case 1 with daily freshwater production of 1 250 m3/day at a unit cost of 1.54 $/m3 and Case 2 with daily freshwater production of 1 501 m3/day at a unit cost of 1.28 $/m3.
- Full Text:
- Authors: Okampo, Ewaoche John
- Date: 2020
- Subjects: Saline water conversion - Reverse osmosis process , Renewable energy sources
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/481956 , uj:43687
- Description: Ph.D. , Abstract: Desalination is a viable solution to meet water scarcity but is regarded as cost-intensive. The reverse osmosis (RO) technique of desalination is commonly used for its cost-effectiveness as compared to other methods but still considered energy-intensive. Conventional fossil energy sources emit carbon gas, which has environmental and cost implications, while renewable energy sources are limited by intermittency. This study formulates mathematical optimization models used to determine the optimal energy mix to power a reverse osmosis desalination unit. The models are formulated to ensure balance between power supply and demand, water demand and water produced, cost functions, and a time-of-use demand response (TOU DR) program. The cost functions include carbon emission cost, DR cost and components cost. The objective of The optimization models is to minimize the annualized cost of system (ACS), levelized cost of energy (LCOE), unit cost of water (COW) and carbon emissions, while maximizing the quantity of freshwater production subject to different economic and system reliability constraints. The first model has an energy mix of grid power, a diesel generator and a photovoltaic (PV) module to supply an RO desalination unit with the objective of maximizing freshwater production at minimal cost. Also considered is the impact of DR and its cost on the quantity of water produced at different hours of the day, and the unit cost of freshwater. Three cases of optimal sizing approaches were compared. Case 1 is a system with only grid power and a diesel generator as energy sources; Case 2 has PV power incorporated in the energy supply mix, while Case 3 has the three energy sources and a TOU DR program on the demand side. The result shows that Case 3 turns out the highest freshwater production (1 520 m3/day) at low cost of (1.33 $/m3) when compared to Case 1 with daily freshwater production of 1 250 m3/day at a unit cost of 1.54 $/m3 and Case 2 with daily freshwater production of 1 501 m3/day at a unit cost of 1.28 $/m3.
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Performance and emission evaluation of a bi-fuel car
- Authors: Kukoyi, Temitope Oladayo
- Date: 2016
- Subjects: Alternative fuel vehicles , Spark ignition engines - Alternative fuels , Motor fuels , Biogas , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242306 , uj:24988
- Description: M.Ing. (Mechanical Engineering) , Abstract: A fundamental shift towards alternative sources of energy particularly in the transport sector has led to the use of fuels such as liquefied petroleum gas and natural gas in spark ignition (SI) engines. However, these fuels retain the challenges associated with fossil fuels which are primarily their finite reserves and negative effects on the ecosystem. This study assesses the use of biogas, a renewable and environmentally friendly high octane fuel in the more popular spark ignition powered passenger vehicle using the simplest single-point fuel delivery conversion kit available on the market. The vehicle powered by a 1.5 litre 1UF-ZE spark ignition engine was converted to a bi-fuel vehicle. Torque, power, and transient emissions were measured with a single roller chassis dynamometer and a gas analyser while running on vehicle quality biogas also referred to as biomethane. The data collated from the use of biogas was pitched with that of petrol in the same system to compare performance and tailpipe emissions. The biogas was simulated by mixing 95% methane (CH4) with 5% carbon dioxide (CO2). The experiments also afforded the opportunity to validate biogas similarity with natural gas (CNG) when used to power vehicles. The research further looked into enhancing system efficiency by investigating the addition of a measure of 2% hydrogen to create a biomethane-hydrogen mix (HCBG) which is within allowable limits of the mix used in a conventional spark ignition (SI) system to curb the negative impacts associated with hydrogen use as a fuel in internal combustion engines. The HCBG was derived by mixing 93% CH4 with 5% CO2 and 2% H2. Biogas recorded a reduction of 16% in maximum power and torque values when pitched with petrol while similar maximum power and torque values to that of biogas were derived from the experiments using natural gas to power the same vehicle. When the hydrogen-biomethane mix was utilised, a 1% power drop was noticed. However, slight increments in power and torque values at mid-speed ranges showed promise for higher hydrogen concentrations in the HCBG in fine-tuned systems. With respect to the mass emission of pollutants, the Inspection and Maintenance 240 (IM240) Drive Cycle was employed to determine the carbon dioxide (CO2), carbon monoxide(CO), hydrocarbon (HC), nitrous oxide (NOx) values in grammes per kilometer (g/km). Biogas recorded an 18% CO2 emission reduction compared to the data obtained using petrol (152.2 g/km). With reference to biogas, CNG recorded 0.4 g/km more CO2 mass emissions while the enhanced HCBG...
- Full Text:
- Authors: Kukoyi, Temitope Oladayo
- Date: 2016
- Subjects: Alternative fuel vehicles , Spark ignition engines - Alternative fuels , Motor fuels , Biogas , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242306 , uj:24988
- Description: M.Ing. (Mechanical Engineering) , Abstract: A fundamental shift towards alternative sources of energy particularly in the transport sector has led to the use of fuels such as liquefied petroleum gas and natural gas in spark ignition (SI) engines. However, these fuels retain the challenges associated with fossil fuels which are primarily their finite reserves and negative effects on the ecosystem. This study assesses the use of biogas, a renewable and environmentally friendly high octane fuel in the more popular spark ignition powered passenger vehicle using the simplest single-point fuel delivery conversion kit available on the market. The vehicle powered by a 1.5 litre 1UF-ZE spark ignition engine was converted to a bi-fuel vehicle. Torque, power, and transient emissions were measured with a single roller chassis dynamometer and a gas analyser while running on vehicle quality biogas also referred to as biomethane. The data collated from the use of biogas was pitched with that of petrol in the same system to compare performance and tailpipe emissions. The biogas was simulated by mixing 95% methane (CH4) with 5% carbon dioxide (CO2). The experiments also afforded the opportunity to validate biogas similarity with natural gas (CNG) when used to power vehicles. The research further looked into enhancing system efficiency by investigating the addition of a measure of 2% hydrogen to create a biomethane-hydrogen mix (HCBG) which is within allowable limits of the mix used in a conventional spark ignition (SI) system to curb the negative impacts associated with hydrogen use as a fuel in internal combustion engines. The HCBG was derived by mixing 93% CH4 with 5% CO2 and 2% H2. Biogas recorded a reduction of 16% in maximum power and torque values when pitched with petrol while similar maximum power and torque values to that of biogas were derived from the experiments using natural gas to power the same vehicle. When the hydrogen-biomethane mix was utilised, a 1% power drop was noticed. However, slight increments in power and torque values at mid-speed ranges showed promise for higher hydrogen concentrations in the HCBG in fine-tuned systems. With respect to the mass emission of pollutants, the Inspection and Maintenance 240 (IM240) Drive Cycle was employed to determine the carbon dioxide (CO2), carbon monoxide(CO), hydrocarbon (HC), nitrous oxide (NOx) values in grammes per kilometer (g/km). Biogas recorded an 18% CO2 emission reduction compared to the data obtained using petrol (152.2 g/km). With reference to biogas, CNG recorded 0.4 g/km more CO2 mass emissions while the enhanced HCBG...
- Full Text:
Renewable energy sources microgrid design for rural area in South Africa
- Longe, O. M., Ouahada, K., Ferreira, Hendrik C., Chinnappen, S.
- Authors: Longe, O. M. , Ouahada, K. , Ferreira, Hendrik C. , Chinnappen, S.
- Date: 2014
- Subjects: Microgrids , Renewable energy sources , Umhlabuyalingana Local Municipality
- Type: Article
- Identifier: uj:4798 , http://hdl.handle.net/10210/12052
- Description: Approximately 1.4 billion people around the world lack access to electricity, of which 85% are rural dwellers, mostly living in Sub-Saharan Africa. In South Africa, 55% of rural dwellers lack access to electricity. The Umhlabuyalingana Local Municipality is the least electrified municipality in the country with an electrification rate of 20%. It is therefore taken as a case study, investigating the implementation of a Renewable Energy Sources (RES) microgrid compared to grid extension. HOMER software was the tool used to carry out the simulation, optimization and sensitivity analyses in this research. It was discovered that a Photo Voltaic (PV) with Battery system is the optimal microgrid combination for the proposed microgrid yielding $0.378/kWh cost of electricity, 0 kg/person CO2 emission, 100% renewable penetration compared to $0.328/kWh cost of grid electricity, 8.9 kg/person CO2 emission from grid extension and 0% renewable penetration from the national grid. The microgrid had a standalone breakeven Electric Distance Limit of 34 km less than the 150 km transmission powerline required for Umhlabuyalingana. This microgrid design is proposed as a better solution to electricity access in unelectrified areas of Umhlabuyalingana local municipality than grid extension.
- Full Text: false
- Authors: Longe, O. M. , Ouahada, K. , Ferreira, Hendrik C. , Chinnappen, S.
- Date: 2014
- Subjects: Microgrids , Renewable energy sources , Umhlabuyalingana Local Municipality
- Type: Article
- Identifier: uj:4798 , http://hdl.handle.net/10210/12052
- Description: Approximately 1.4 billion people around the world lack access to electricity, of which 85% are rural dwellers, mostly living in Sub-Saharan Africa. In South Africa, 55% of rural dwellers lack access to electricity. The Umhlabuyalingana Local Municipality is the least electrified municipality in the country with an electrification rate of 20%. It is therefore taken as a case study, investigating the implementation of a Renewable Energy Sources (RES) microgrid compared to grid extension. HOMER software was the tool used to carry out the simulation, optimization and sensitivity analyses in this research. It was discovered that a Photo Voltaic (PV) with Battery system is the optimal microgrid combination for the proposed microgrid yielding $0.378/kWh cost of electricity, 0 kg/person CO2 emission, 100% renewable penetration compared to $0.328/kWh cost of grid electricity, 8.9 kg/person CO2 emission from grid extension and 0% renewable penetration from the national grid. The microgrid had a standalone breakeven Electric Distance Limit of 34 km less than the 150 km transmission powerline required for Umhlabuyalingana. This microgrid design is proposed as a better solution to electricity access in unelectrified areas of Umhlabuyalingana local municipality than grid extension.
- Full Text: false