Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.706349
Title: Modelling and simulation of intermediate temperature solid oxide fuel cells and their integration in hybrid gas turbine plants
Author: Ighodaro, Osarobo Omorogieva
ISNI:       0000 0004 6057 0160
Awarding Body: Newcastle University
Current Institution: University of Newcastle upon Tyne
Date of Award: 2016
Availability of Full Text:
Access from EThOS:
Access from Institution:
Abstract:
Solid oxide fuel cells (SOFCs) are gaining prominence as power sources amongst other types of fuel cells due to their high electric energy efficiencies, their ability to integrate with other energy cycles in a hybrid system, fuel choice flexibility and low pollutant emissions. Operation of an SOFC involves complex coupling of the electrochemical reactions, chemical reactions and transport phenomena simultaneously in the cell’s main components consisting of gas channels, porous electrodes and the dense ceramic electrolyte. Consequently, mathematical modelling of these processes becomes an essential research tool aiming to provide detailed insight, while reducing cost, time and the effort associated with experimentation. The main aim of this thesis is to develop mathematical models in the cell and at system level to better understand the complex operation of SOFCs and its associated cycle under practical conditions with the aim of enhancing the power output and efficiency of the cell. At the cell level, a two dimensional along the channel micro-scale isothermal model of a SOFC is developed and validated against experimental data and other simulated result from literature. The steady state behaviour of the cell was determined by numerical solution of the combined transport, continuity and kinetic equations. The model is capable of predicting the cell performance including polarisation behaviour and power output. The model is used to study the effect of the support structure, geometric parameters and the effect of operating conditions on cell performance. Several parametric studies, such as the effect of operating conditions and geometric parameters on cell performance with a view to optimising the cell. Also, at the cell level, a two dimensional along the channel model was developed which integrates a heat transfer model and direct internal reforming kinetics into the earlier developed isothermal model. This non-isothermal model was also validated against experimental data. The developed model not only predicts the performance of the SOFC at different design and operating conditions, it also provides an insight on the different phenomena and the distributions of current density, temperature and gas pressures within the cell. Microstructural parametric studies of the reaction layer were also carried out. Solid oxide fuel cells (SOFCs) are gaining prominence as power sources amongst other types of fuel cells due to their high electric energy efficiencies, their ability to integrate with other energy cycles in a hybrid system, fuel choice flexibility and low pollutant emissions. Operation of an SOFC involves complex coupling of the electrochemical reactions, chemical reactions and transport phenomena simultaneously in the cell’s main components consisting of gas channels, porous electrodes and the dense ceramic electrolyte. Consequently, mathematical modelling of these processes becomes an essential research tool aiming to provide detailed insight, while reducing cost, time and the effort associated with experimentation. The main aim of this thesis is to develop mathematical models in the cell and at system level to better understand the complex operation of SOFCs and its associated cycle under practical conditions with the aim of enhancing the power output and efficiency of the cell. At the cell level, a two dimensional along the channel micro-scale isothermal model of a SOFC is developed and validated against experimental data and other simulated result from literature. The steady state behaviour of the cell was determined by numerical solution of the combined transport, continuity and kinetic equations. The model is capable of predicting the cell performance including polarisation behaviour and power output. The model is used to study the effect of the support structure, geometric parameters and the effect of operating conditions on cell performance. Several parametric studies, such as the effect of operating conditions and geometric parameters on cell performance with a view to optimising the cell. Also, at the cell level, a two dimensional along the channel model was developed which integrates a heat transfer model and direct internal reforming kinetics into the earlier developed isothermal model. This non-isothermal model was also validated against experimental data. The developed model not only predicts the performance of the SOFC at different design and operating conditions, it also provides an insight on the different phenomena and the distributions of current density, temperature and gas pressures within the cell. Microstructural parametric studies of the reaction layer were also carried out. Solid oxide fuel cells (SOFCs) are gaining prominence as power sources amongst other types of fuel cells due to their high electric energy efficiencies, their ability to integrate with other energy cycles in a hybrid system, fuel choice flexibility and low pollutant emissions. Operation of an SOFC involves complex coupling of the electrochemical reactions, chemical reactions and transport phenomena simultaneously in the cell’s main components consisting of gas channels, porous electrodes and the dense ceramic electrolyte. Consequently, mathematical modelling of these processes becomes an essential research tool aiming to provide detailed insight, while reducing cost, time and the effort associated with experimentation. The main aim of this thesis is to develop mathematical models in the cell and at system level to better understand the complex operation of SOFCs and its associated cycle under practical conditions with the aim of enhancing the power output and efficiency of the cell. At the cell level, a two dimensional along the channel micro-scale isothermal model of a SOFC is developed and validated against experimental data and other simulated result from literature. The steady state behaviour of the cell was determined by numerical solution of the combined transport, continuity and kinetic equations. The model is capable of predicting the cell performance including polarisation behaviour and power output. The model is used to study the effect of the support structure, geometric parameters and the effect of operating conditions on cell performance. Several parametric studies, such as the effect of operating conditions and geometric parameters on cell performance with a view to optimising the cell. Also, at the cell level, a two dimensional along the channel model was developed which integrates a heat transfer model and direct internal reforming kinetics into the earlier developed isothermal model. This non-isothermal model was also validated against experimental data. The developed model not only predicts the performance of the SOFC at different design and operating conditions, it also provides an insight on the different phenomena and the distributions of current density, temperature and gas pressures within the cell. Microstructural parametric studies of the reaction layer were also carried out. At the system level, the SOFC was integrated in a hybrid gas turbine plant. The integrated cycle was modelled using energy and exergy thermodynamic analysis. The analysis was done using the non-isothermal models developed for SOFC at the cell level and through the development of thermodynamic models for the other components such as the compressors, turbines, mixers, recuperators and combustors in the hybrid system. Performance comparison of two different hybrid configurations was carried out. Electrical efficiency, fuel utilisation efficiency, and exergy destruction were used in assessing the system performance. The results from the developed models shows that the anode supported SOFCs gives the best cell performance amongst other support structures when operated at intermediate temperatures and that the cathode ohmic overpotential is the single largest contributor to the cell potential loss. Also, the inclusion of the heat transfer model and internal reforming kinetics significantly improves the cell predictions. The study on the effect of integrating the SOFC in a hybrid system showed an overall improvement with respect to electrical efficiency.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.706349  DOI: Not available
Share: