Comprehending the spatiotemporal complementarity of variable renewable energy (VRE) sources and t... more Comprehending the spatiotemporal complementarity of variable renewable energy (VRE) sources and their supplemental ability to meet electricity demand is a promising move towards broadening their share in the power supply mix without sacrificing either supply security or overall cost efficiency of power system operation. Increasing VRE share into the energy mix has to be followed with measures to manage technical challenges associated with grid operations. Most sub-Saharan countries can be considered ‘greenfield’ due to their relatively low power generation baseline and are more likely to be advantaged in planning their future grids around the idea of integrating high VRE sources into the grid from the outset. An essential measure for achieving this objective entails exploring the possibility of integrating renewable hybrid power plants into the existing hydropower grid, leveraging on existing synergies and benefiting from the use of existing infrastructure and grid connection points...
Renewable energy distributed generation is reaching an unprecedented level of integration into po... more Renewable energy distributed generation is reaching an unprecedented level of integration into power generation systems due to its numerous advantages. However, its increased penetration compounds the level of uncertainties being coped with in distribution systems. This aggravates the difficulty in making decisions in the context of large-scale penetration of renewable distributed generations, especially with the intermittent ones. Consequently, the analysis of uncertainty and modelling of the related system parameters is essential. This paper aims to provide a state-of-the-art review on uncertainty modelling approaches for distribution system studies and applications. This work focuses mainly on classifying and comparing the uncertainty modelling approaches and methodologies, presenting mathematical syntax of the methods, as well as the merits and demerits of the modelling methods. This study serves as the knowledge warehouse and selection tool for choosing the most suitable method for various applications.
ABSTRACT Wind farms (WFs) based on doubly-fed induction generator (DFIG) have become nowadays ver... more ABSTRACT Wind farms (WFs) based on doubly-fed induction generator (DFIG) have become nowadays very popular for the national grid integration option. The reason for this is their ability to support the electric grid with its reactive power. Most of the optimal reactive power (VAR) problems in the past, have dealt with conventional electric grid, and a few with the grid-connected WFs based on squirrel cage induction generator (SCIG). This paper presents an optimal VAR control problem where all VAR control variables present in the network as well as the reactive power from the reactive power capability (RPC) of DFIGs are optimized for achieving the system active power loss minimization. Particle swarm optimization (PSO) algorithm is used as an optimizer tool. Simulation results based on IEEE 6-bus test system show the effectiveness of the optimal use of RPC of DFIGs in solving VAR problem.
Environmental footprints and eco-design of products and processes, 2019
In satisfying the perpetually increasing energy demand, utility companies have traditionally depe... more In satisfying the perpetually increasing energy demand, utility companies have traditionally depended on fossil-based energy sources (natural gas, oil and coal). These fuels are carbon-intensive, and burning them has negative implications on both human health and environment. However, in order to make sure that the global temperature rise is kept below 2 °C based on the Paris Agreement, it is essential that the electricity generation industry is subjected to transformation through the process of decarbonisation. Renewable energy sources have the tendency to mitigate the negative effects of the conventionally powered power plant. The move to renewable sources motivated the start of the process of decarbonisation—reducing the carbon intensity of the electricity generation. Furthermore, the adoption of demand-side management, carbon capture and storage, clean coal technologies, decommissioning of ageing fossil fuel-powered plants (replacing it with renewable energy-based plants), nuclear energy and adoption of stringent low-carbon policies can also aid decarbonisation of the power system sector. This work presents the trends and challenges in the decarbonisation of the power generation. This will help in achieving an all-encompassing strategy for the attainment of green economy. It is predicted that in order to maintain 2 °C temperature rise by 2050, the following technologies will contribute to emission reduction: carbon capture and storage 19%, fuel switching and efficiency 1%, hydro 3%, nuclear 13%, solar photovoltaic 9%, concentrated solar power 7%, wind onshore 9%, wind offshore 3%, biomass 4%, electricity saving 29% and other renewables 3%. It is clear that there is no singular approach that can entirely be used for the decarbonisation of the grid. An integrated approach that accommodates various policies and decarbonisation technologies will enhance low-carbon electricity generation.
ABSTRACT In a weak network where the reactive power capability is not able to satisfy the demand ... more ABSTRACT In a weak network where the reactive power capability is not able to satisfy the demand of wind farm based on squirrel-cage induction generator (SCIG), flexible AC transmission system such as static VAR compensator (SVC) is used. Traditionally, the SVC device and other network reactive power facilities are used in optimal way by the network operator, for optimal voltage profile and loss minimization, during different steady-state operations caused by wind resource changes. In this paper, the SVC reactive power reserve (SVC-RPR) is added to the problem as a third objective function to be maximized with the purpose of further compensation usage during dynamic operation. Particle swarm optimization (PSO) is used to optimize the search space of this multi-objective problem. The reactive power optimization scheme is tested in a MATLAB/R2010a based simulation model of Wale & Hale 6-bus system with wind farm integration. It is has been found that the conflict between the three objective functions causes the difficulty of achieving a sufficient SVC-RPR during high wind farm power generation, unless the SVC rating is designed in such away to be higher than the reactive power required by the total number of SCIG at full load.
The variability of large-scale photovoltaic/wind hybrid distributed generation power integrated i... more The variability of large-scale photovoltaic/wind hybrid distributed generation power integrated into the distribution system causes persistent system oscillations. The oscillations result in serious small-signal stability issues when these distributed generation units are not adequately optimised and the network dynamic variables are unconstrained as seen in the existing renewable power allocation planning works. In this paper, planning and design of optimal allocation (sizing, placement) and timing of intermittent renewable energy hybrid distributed generations such as photovoltaic and wind is being investigated with the ultimate goal of maximising the renewable power generated and absorbed into the distribution network within the required small-signal stability level at a minimum net present value of total cost. The problem is formulated as a stochastic mixed integer linear program where variables related to small-signal stability are constrained. The paper also evaluated the impact of these renewable generation output power variability on the small-signal stability of the IEEE-24 bus test system using eigenvalues analysis. The results indicate a profound improvement on the small-signal stability of the network, an increase in the quantity of renewable power absorbed and a significant reduction in the costs of emissions and electricity.
This paper presents an analysis of an off-grid hybrid energy system (HES) for a single residentia... more This paper presents an analysis of an off-grid hybrid energy system (HES) for a single residential apartment owned by a low-income earner. The system is made up of photovoltaic (PV), wind, battery storage system, and a gasoline generator. Using a house in Akoka, Nigeria as a case study, the HES is developed to adequately supply a load of 3.8kWh/day. The technical, economic and environmental considerations are presented. The results revealed the potential of the HES to provide environment-friendly, cost-effective and affordable electricity for the low income household, as compared to using only gasoline generators.
As a contribution to the studies on techno-economic optimization and sizing of a standalone energ... more As a contribution to the studies on techno-economic optimization and sizing of a standalone energy system, this study presents the optimal sizing of a Photovoltaic (PV) system based on various tracking configurations. In order to elucidate the impact of temperature coefficient of PV modules on the techno-economic results from the optimal sizing of a PV system, a comparison of tracking configuration with and without temperature coefficient is also presented. Results indicate that a PV system with no tracking device performed best in terms of economic metrics. As regards the level of annual electricity production, the PV system with two axis orientation had a superior performance if temperature effect is considered while the PV system with horizontal axis, continuous adjustment performed best if the temperature effect is neglected.
Generation expansion planning (GEP) problem which is also known as the power plant mix problem (P... more Generation expansion planning (GEP) problem which is also known as the power plant mix problem (PPMP) has received a lot of attention from researchers worldwide. PPMP has been formulated and presented from various perspectives, models, objectives, constraints, and solution methods. This paper presents a brief review of state-of-the-art topics on PPMP. A discussion on PPMP trends and challenges is also presented. The review results provide a comprehensive background on areas of further works in this field.
Wind energy exhibits high intermittence in its characteristics and this constitutes a major setba... more Wind energy exhibits high intermittence in its characteristics and this constitutes a major setback to its integration into the power system operation. Conventional power system operation is a challenging task under variable load and power generation. Integration of wind power, especially on large scales further complicates the operation. In conventional power system, wind generation is connected directly into the system using available techniques to minimize impact of the intermittence. This work proposes a solution to the problem using a new method that requires the elimination of the intermittence prior to its connection into the power system. This minimizes the associated instability issues that could normally result in operational disturbance on both the wind turbine and the power system in addition to increasing the wind power harvest. In this method, the wind power is first harnessed into a Pumped Hydro Generator and thereafter discharged to the power system.
2019 IEEE 2nd International Conference on Renewable Energy and Power Engineering (REPE)
Due to the preference placed on sustainability of resources and the need for reduction in the emi... more Due to the preference placed on sustainability of resources and the need for reduction in the emissions related to electricity generation, various sustainable developmental strategies have been proposed. These policies are usually based on social, technical, economic, environmental and policy aspects. One of the strategies targeted at ensuring sustainability and emission reduction is the inclusion of low-emission electricity generation technologies in the future power plant mix. This study proposes a hybrid multi-criteria decision-making model based on a fuzzy modified similarity-based method for the evaluation and ranking of five green energy alternatives for generation expansion. In order to implement the proposed model, a number of criteria and attributes are defined for implementation. The results show that based on the social, technical, economic and environmental (STEE) criteria the wind technology is the most suitable option while the hydro technology is the least suitable. With regards to the techno-economic perspective, the wind technology was also identified as the most suitable while the geothermal technology is the least suitable option.
Comprehending the spatiotemporal complementarity of variable renewable energy (VRE) sources and t... more Comprehending the spatiotemporal complementarity of variable renewable energy (VRE) sources and their supplemental ability to meet electricity demand is a promising move towards broadening their share in the power supply mix without sacrificing either supply security or overall cost efficiency of power system operation. Increasing VRE share into the energy mix has to be followed with measures to manage technical challenges associated with grid operations. Most sub-Saharan countries can be considered ‘greenfield’ due to their relatively low power generation baseline and are more likely to be advantaged in planning their future grids around the idea of integrating high VRE sources into the grid from the outset. An essential measure for achieving this objective entails exploring the possibility of integrating renewable hybrid power plants into the existing hydropower grid, leveraging on existing synergies and benefiting from the use of existing infrastructure and grid connection points...
Renewable energy distributed generation is reaching an unprecedented level of integration into po... more Renewable energy distributed generation is reaching an unprecedented level of integration into power generation systems due to its numerous advantages. However, its increased penetration compounds the level of uncertainties being coped with in distribution systems. This aggravates the difficulty in making decisions in the context of large-scale penetration of renewable distributed generations, especially with the intermittent ones. Consequently, the analysis of uncertainty and modelling of the related system parameters is essential. This paper aims to provide a state-of-the-art review on uncertainty modelling approaches for distribution system studies and applications. This work focuses mainly on classifying and comparing the uncertainty modelling approaches and methodologies, presenting mathematical syntax of the methods, as well as the merits and demerits of the modelling methods. This study serves as the knowledge warehouse and selection tool for choosing the most suitable method for various applications.
ABSTRACT Wind farms (WFs) based on doubly-fed induction generator (DFIG) have become nowadays ver... more ABSTRACT Wind farms (WFs) based on doubly-fed induction generator (DFIG) have become nowadays very popular for the national grid integration option. The reason for this is their ability to support the electric grid with its reactive power. Most of the optimal reactive power (VAR) problems in the past, have dealt with conventional electric grid, and a few with the grid-connected WFs based on squirrel cage induction generator (SCIG). This paper presents an optimal VAR control problem where all VAR control variables present in the network as well as the reactive power from the reactive power capability (RPC) of DFIGs are optimized for achieving the system active power loss minimization. Particle swarm optimization (PSO) algorithm is used as an optimizer tool. Simulation results based on IEEE 6-bus test system show the effectiveness of the optimal use of RPC of DFIGs in solving VAR problem.
Environmental footprints and eco-design of products and processes, 2019
In satisfying the perpetually increasing energy demand, utility companies have traditionally depe... more In satisfying the perpetually increasing energy demand, utility companies have traditionally depended on fossil-based energy sources (natural gas, oil and coal). These fuels are carbon-intensive, and burning them has negative implications on both human health and environment. However, in order to make sure that the global temperature rise is kept below 2 °C based on the Paris Agreement, it is essential that the electricity generation industry is subjected to transformation through the process of decarbonisation. Renewable energy sources have the tendency to mitigate the negative effects of the conventionally powered power plant. The move to renewable sources motivated the start of the process of decarbonisation—reducing the carbon intensity of the electricity generation. Furthermore, the adoption of demand-side management, carbon capture and storage, clean coal technologies, decommissioning of ageing fossil fuel-powered plants (replacing it with renewable energy-based plants), nuclear energy and adoption of stringent low-carbon policies can also aid decarbonisation of the power system sector. This work presents the trends and challenges in the decarbonisation of the power generation. This will help in achieving an all-encompassing strategy for the attainment of green economy. It is predicted that in order to maintain 2 °C temperature rise by 2050, the following technologies will contribute to emission reduction: carbon capture and storage 19%, fuel switching and efficiency 1%, hydro 3%, nuclear 13%, solar photovoltaic 9%, concentrated solar power 7%, wind onshore 9%, wind offshore 3%, biomass 4%, electricity saving 29% and other renewables 3%. It is clear that there is no singular approach that can entirely be used for the decarbonisation of the grid. An integrated approach that accommodates various policies and decarbonisation technologies will enhance low-carbon electricity generation.
ABSTRACT In a weak network where the reactive power capability is not able to satisfy the demand ... more ABSTRACT In a weak network where the reactive power capability is not able to satisfy the demand of wind farm based on squirrel-cage induction generator (SCIG), flexible AC transmission system such as static VAR compensator (SVC) is used. Traditionally, the SVC device and other network reactive power facilities are used in optimal way by the network operator, for optimal voltage profile and loss minimization, during different steady-state operations caused by wind resource changes. In this paper, the SVC reactive power reserve (SVC-RPR) is added to the problem as a third objective function to be maximized with the purpose of further compensation usage during dynamic operation. Particle swarm optimization (PSO) is used to optimize the search space of this multi-objective problem. The reactive power optimization scheme is tested in a MATLAB/R2010a based simulation model of Wale & Hale 6-bus system with wind farm integration. It is has been found that the conflict between the three objective functions causes the difficulty of achieving a sufficient SVC-RPR during high wind farm power generation, unless the SVC rating is designed in such away to be higher than the reactive power required by the total number of SCIG at full load.
The variability of large-scale photovoltaic/wind hybrid distributed generation power integrated i... more The variability of large-scale photovoltaic/wind hybrid distributed generation power integrated into the distribution system causes persistent system oscillations. The oscillations result in serious small-signal stability issues when these distributed generation units are not adequately optimised and the network dynamic variables are unconstrained as seen in the existing renewable power allocation planning works. In this paper, planning and design of optimal allocation (sizing, placement) and timing of intermittent renewable energy hybrid distributed generations such as photovoltaic and wind is being investigated with the ultimate goal of maximising the renewable power generated and absorbed into the distribution network within the required small-signal stability level at a minimum net present value of total cost. The problem is formulated as a stochastic mixed integer linear program where variables related to small-signal stability are constrained. The paper also evaluated the impact of these renewable generation output power variability on the small-signal stability of the IEEE-24 bus test system using eigenvalues analysis. The results indicate a profound improvement on the small-signal stability of the network, an increase in the quantity of renewable power absorbed and a significant reduction in the costs of emissions and electricity.
This paper presents an analysis of an off-grid hybrid energy system (HES) for a single residentia... more This paper presents an analysis of an off-grid hybrid energy system (HES) for a single residential apartment owned by a low-income earner. The system is made up of photovoltaic (PV), wind, battery storage system, and a gasoline generator. Using a house in Akoka, Nigeria as a case study, the HES is developed to adequately supply a load of 3.8kWh/day. The technical, economic and environmental considerations are presented. The results revealed the potential of the HES to provide environment-friendly, cost-effective and affordable electricity for the low income household, as compared to using only gasoline generators.
As a contribution to the studies on techno-economic optimization and sizing of a standalone energ... more As a contribution to the studies on techno-economic optimization and sizing of a standalone energy system, this study presents the optimal sizing of a Photovoltaic (PV) system based on various tracking configurations. In order to elucidate the impact of temperature coefficient of PV modules on the techno-economic results from the optimal sizing of a PV system, a comparison of tracking configuration with and without temperature coefficient is also presented. Results indicate that a PV system with no tracking device performed best in terms of economic metrics. As regards the level of annual electricity production, the PV system with two axis orientation had a superior performance if temperature effect is considered while the PV system with horizontal axis, continuous adjustment performed best if the temperature effect is neglected.
Generation expansion planning (GEP) problem which is also known as the power plant mix problem (P... more Generation expansion planning (GEP) problem which is also known as the power plant mix problem (PPMP) has received a lot of attention from researchers worldwide. PPMP has been formulated and presented from various perspectives, models, objectives, constraints, and solution methods. This paper presents a brief review of state-of-the-art topics on PPMP. A discussion on PPMP trends and challenges is also presented. The review results provide a comprehensive background on areas of further works in this field.
Wind energy exhibits high intermittence in its characteristics and this constitutes a major setba... more Wind energy exhibits high intermittence in its characteristics and this constitutes a major setback to its integration into the power system operation. Conventional power system operation is a challenging task under variable load and power generation. Integration of wind power, especially on large scales further complicates the operation. In conventional power system, wind generation is connected directly into the system using available techniques to minimize impact of the intermittence. This work proposes a solution to the problem using a new method that requires the elimination of the intermittence prior to its connection into the power system. This minimizes the associated instability issues that could normally result in operational disturbance on both the wind turbine and the power system in addition to increasing the wind power harvest. In this method, the wind power is first harnessed into a Pumped Hydro Generator and thereafter discharged to the power system.
2019 IEEE 2nd International Conference on Renewable Energy and Power Engineering (REPE)
Due to the preference placed on sustainability of resources and the need for reduction in the emi... more Due to the preference placed on sustainability of resources and the need for reduction in the emissions related to electricity generation, various sustainable developmental strategies have been proposed. These policies are usually based on social, technical, economic, environmental and policy aspects. One of the strategies targeted at ensuring sustainability and emission reduction is the inclusion of low-emission electricity generation technologies in the future power plant mix. This study proposes a hybrid multi-criteria decision-making model based on a fuzzy modified similarity-based method for the evaluation and ranking of five green energy alternatives for generation expansion. In order to implement the proposed model, a number of criteria and attributes are defined for implementation. The results show that based on the social, technical, economic and environmental (STEE) criteria the wind technology is the most suitable option while the hydro technology is the least suitable. With regards to the techno-economic perspective, the wind technology was also identified as the most suitable while the geothermal technology is the least suitable option.
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Papers by Josiah Munda