The Experts below are selected from a list of 678 Experts worldwide ranked by ideXlab platform
Ni M - One of the best experts on this subject based on the ideXlab platform.
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Mathematical modeling of ammonia-fed solid oxide fuel cells with different electrolytes
'Elsevier BV', 2008Co-Authors: Ni M, Leung Mkh, Leung DycAbstract:An electrochemical model was developed to study the ammonia (NH3)-fed solid oxide fuel cells with proton-conducting electrolyte (SOFC-H) and oxygen ion-conducting electrolyte (SOFC-O). Different from previous thermodynamic analysis, the present study reveals that the actual performance of the NH3-fed SOFC-H is considerably lower than the SOFC-O, mainly due to higher Ohmic Overpotential of the SOFC-H electrolyte. More analyses have been performed to study the separate Overpotentials of the NH3-fed SOFC-H and SOFC-O. Compared with the NH3-fed SOFC-H, the SOFC-O has higher anode concentration Overpotential and lower cathode concentration Overpotential. The effects of temperature and electrode porosity on concentration Overpotentials have also been studied in order to identify possible methods for improvement of SOFC performance. This study reveals that the use of different electrolytes not only causes different ion conduction characteristics at the electrolyte, but also significantly influences the concentration Overpotentials at the electrodes. The model developed in this article can be extended to 2D and 3D models for further design optimization. © 2008 International Association for Hydrogen Energy.link_to_subscribed_fulltex
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Modeling of methane fed solid oxide fuel cells: Comparison between proton conducting electrolyte and oxygen ion conducting electrolyte
'Elsevier BV', 2008Co-Authors: Leung Mkh, Leung Dyc, Ni MAbstract:An electrochemical model was developed to study the methane (CH4) fed solid oxide fuel cell (SOFC) using proton conducting electrolyte (SOFC-H) and oxygen ion conducting electrolyte (SOFC-O). Both the internal methane steam reforming (MSR) and water gas shift (WGS) reactions are considered in the model. Previous study has shown that the CH4 fed SOFC-H had significantly better performance than the SOFC-O. However, the present study reveals that the actual performance of the CH4 fed SOFC-H is considerably lower than the SOFC-O, partly due to higher Ohmic Overpotential of SOFC-H. It is also found that the CH4 fed SOFC-H has considerably higher cathode concentration Overpotential and lower anode concentration Overpotential than the SOFC-O. The anode concentration Overpotentials of the CH4 fed SOFC-H and SOFC-O are found to decrease with increasing temperature, which is different from previous analyses on the H2 fed SOFC. Therefore, high temperature is desirable for increasing the potential of the CH4 fed SOFC. It is also found that there exist optimal electrode porosities that minimize the electrode total Overpotentials. The analyses provided in this paper signify the difference between the CH4 fed SOFC-H and SOFC-O. The model developed in this paper can be extended to 2D or 3D models to study the performance of practical SOFC systems. © 2008 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex
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Electrochemical modeling of ammonia-fed solid oxide fuel cells based on proton conducting electrolyte
'Elsevier BV', 2008Co-Authors: Ni M, Leung Mkh, Leung DycAbstract:An electrochemical model was developed to study the NH3-fed and H2-fed solid oxide fuel cells based on proton conducting electrolyte (SOFC-H). The modeling results were consistent with experimental data in literature. It is found that there is little difference in working voltage and power density between the NH3-fed and the H2-fed SOFC-H with an electrolyte-support configuration due to an extremely high Ohmic Overpotential in the SOFC-H. With an anode-supported configuration, especially when a thin film electrolyte is used, the H2-fed SOFC-H shows significantly higher voltage and power density than the NH3-fed SOFC-H due to the significant difference in concentration Overpotentials. The anode concentration Overpotential of the NH3-fed SOFC-H is found much higher than the H2-fed SOFC-H, as the presence of N2 gas dilutes the H2 concentration and slows down the transport of H 2. More importantly, the cathode concentration Overpotential is found very significant despite of the thin cathode used in the anode-supported configuration. In the SOFC-H, H2O is produced in the cathode, which enables complete fuel utilization on one hand, but dilutes the concentration of O2 and impedes the diffusion of O2 to the reaction sites on the other hand. Thus, the cathode concentration Overpotential is the limiting factor for the H2-fed SOFC-H and an important voltage loss in the NH3-fed SOFC-H. How to reduce the concentration Overpotentials at both electrodes is identified crucial to develop high performance SOFC-H. © 2008 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex
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Parametric study of solid oxide steam electrolyzer for hydrogen production
'Elsevier BV', 2007Co-Authors: Leung Mkh, Leung Dyc, Ni MAbstract:A theoretical model was developed to study the electrical characteristics of a solid oxide steam electrolyzer (SOSE) for hydrogen production. The activation and concentration Overpotentials at the electrodes as well as the Ohmic Overpotential at the electrolyte were considered as the main sources of voltage loss. The Butler-Volmer equation, Fick's model, and Ohm's law were applied to characterize the Overpotentials. The theoretical model was validated as the simulation results agreed well with the experimental data from the literature. In the study of the component thickness effect, anode-support SOSE configuration was identified as the most favorable design. Further parametric analyses were performed to study the effects of material properties and operating conditions on the anode-supported SOSE cell performance. The results have shown that increasing electrode porosity and pore size can reduce the voltage loss. In the operation, both temperature and steam molar fraction can be increased to enhance the SOSE electrical efficiency. The pressure should be regulated depending on the current density. The electrochemistry model can be used to perform more analyses to gain insightful understanding of the SOSE hydrogen production principles and to optimize the SOSE cell and system designs. © 2007 International Association for Hydrogen Energy.link_to_subscribed_fulltex
Yihhang Chen - One of the best experts on this subject based on the ideXlab platform.
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operation relevant modeling of an experimental proton exchange membrane fuel cell
Journal of Power Sources, 2007Co-Authors: Aijen Hung, Lungyu Sung, Yihhang ChenAbstract:Abstract A current–voltage ( I – V ) curve, also known as a polarization curve, is generally used to express the characteristics of a proton exchange membrane (PEM) fuel cell system. The behavior of a PEM fuel cell is highly nonlinear and it is important to incorporate process nonlinearity for control system design and process optimization. Therefore, it is essential to generate the I – V curve from the model as the operating condition changes. A first principle one-dimensional water and thermal management model is developed to generate the I – V curve. The model considers the effects of water transport across the membrane, activation Overpotential, Ohmic Overpotential, concentration Overpotential, pressure drops, and current density distribution along the channel of a PEM fuel cell. Design and modeling parameters are obtained via regression from four sets of experimental data. They are further validated as operating conditions (e.g., fuel cell temperature, anode pressure, cathode pressure, hydrogen stoichiometric ratio, air stoichiometric ratio, hydrogen humidification temperature, and air humidification temperature) change. A sensitivity analysis example is used to illustrate the usefulness of the predictive model.
Dennis Y C Leung - One of the best experts on this subject based on the ideXlab platform.
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parametric study of solid oxide steam electrolyzer for hydrogen production
International Journal of Hydrogen Energy, 2007Co-Authors: Meng Ni, Michael K H Leung, Dennis Y C LeungAbstract:Abstract A theoretical model was developed to study the electrical characteristics of a solid oxide steam electrolyzer (SOSE) for hydrogen production. The activation and concentration Overpotentials at the electrodes as well as the Ohmic Overpotential at the electrolyte were considered as the main sources of voltage loss. The Butler–Volmer equation, Fick's model, and Ohm's law were applied to characterize the Overpotentials. The theoretical model was validated as the simulation results agreed well with the experimental data from the literature. In the study of the component thickness effect, anode-support SOSE configuration was identified as the most favorable design. Further parametric analyses were performed to study the effects of material properties and operating conditions on the anode-supported SOSE cell performance. The results have shown that increasing electrode porosity and pore size can reduce the voltage loss. In the operation, both temperature and steam molar fraction can be increased to enhance the SOSE electrical efficiency. The pressure should be regulated depending on the current density. The electrochemistry model can be used to perform more analyses to gain insightful understanding of the SOSE hydrogen production principles and to optimize the SOSE cell and system designs.
Leung Dyc - One of the best experts on this subject based on the ideXlab platform.
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Mathematical modeling of ammonia-fed solid oxide fuel cells with different electrolytes
'Elsevier BV', 2008Co-Authors: Ni M, Leung Mkh, Leung DycAbstract:An electrochemical model was developed to study the ammonia (NH3)-fed solid oxide fuel cells with proton-conducting electrolyte (SOFC-H) and oxygen ion-conducting electrolyte (SOFC-O). Different from previous thermodynamic analysis, the present study reveals that the actual performance of the NH3-fed SOFC-H is considerably lower than the SOFC-O, mainly due to higher Ohmic Overpotential of the SOFC-H electrolyte. More analyses have been performed to study the separate Overpotentials of the NH3-fed SOFC-H and SOFC-O. Compared with the NH3-fed SOFC-H, the SOFC-O has higher anode concentration Overpotential and lower cathode concentration Overpotential. The effects of temperature and electrode porosity on concentration Overpotentials have also been studied in order to identify possible methods for improvement of SOFC performance. This study reveals that the use of different electrolytes not only causes different ion conduction characteristics at the electrolyte, but also significantly influences the concentration Overpotentials at the electrodes. The model developed in this article can be extended to 2D and 3D models for further design optimization. © 2008 International Association for Hydrogen Energy.link_to_subscribed_fulltex
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Modeling of methane fed solid oxide fuel cells: Comparison between proton conducting electrolyte and oxygen ion conducting electrolyte
'Elsevier BV', 2008Co-Authors: Leung Mkh, Leung Dyc, Ni MAbstract:An electrochemical model was developed to study the methane (CH4) fed solid oxide fuel cell (SOFC) using proton conducting electrolyte (SOFC-H) and oxygen ion conducting electrolyte (SOFC-O). Both the internal methane steam reforming (MSR) and water gas shift (WGS) reactions are considered in the model. Previous study has shown that the CH4 fed SOFC-H had significantly better performance than the SOFC-O. However, the present study reveals that the actual performance of the CH4 fed SOFC-H is considerably lower than the SOFC-O, partly due to higher Ohmic Overpotential of SOFC-H. It is also found that the CH4 fed SOFC-H has considerably higher cathode concentration Overpotential and lower anode concentration Overpotential than the SOFC-O. The anode concentration Overpotentials of the CH4 fed SOFC-H and SOFC-O are found to decrease with increasing temperature, which is different from previous analyses on the H2 fed SOFC. Therefore, high temperature is desirable for increasing the potential of the CH4 fed SOFC. It is also found that there exist optimal electrode porosities that minimize the electrode total Overpotentials. The analyses provided in this paper signify the difference between the CH4 fed SOFC-H and SOFC-O. The model developed in this paper can be extended to 2D or 3D models to study the performance of practical SOFC systems. © 2008 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex
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Electrochemical modeling of ammonia-fed solid oxide fuel cells based on proton conducting electrolyte
'Elsevier BV', 2008Co-Authors: Ni M, Leung Mkh, Leung DycAbstract:An electrochemical model was developed to study the NH3-fed and H2-fed solid oxide fuel cells based on proton conducting electrolyte (SOFC-H). The modeling results were consistent with experimental data in literature. It is found that there is little difference in working voltage and power density between the NH3-fed and the H2-fed SOFC-H with an electrolyte-support configuration due to an extremely high Ohmic Overpotential in the SOFC-H. With an anode-supported configuration, especially when a thin film electrolyte is used, the H2-fed SOFC-H shows significantly higher voltage and power density than the NH3-fed SOFC-H due to the significant difference in concentration Overpotentials. The anode concentration Overpotential of the NH3-fed SOFC-H is found much higher than the H2-fed SOFC-H, as the presence of N2 gas dilutes the H2 concentration and slows down the transport of H 2. More importantly, the cathode concentration Overpotential is found very significant despite of the thin cathode used in the anode-supported configuration. In the SOFC-H, H2O is produced in the cathode, which enables complete fuel utilization on one hand, but dilutes the concentration of O2 and impedes the diffusion of O2 to the reaction sites on the other hand. Thus, the cathode concentration Overpotential is the limiting factor for the H2-fed SOFC-H and an important voltage loss in the NH3-fed SOFC-H. How to reduce the concentration Overpotentials at both electrodes is identified crucial to develop high performance SOFC-H. © 2008 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex
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Parametric study of solid oxide steam electrolyzer for hydrogen production
'Elsevier BV', 2007Co-Authors: Leung Mkh, Leung Dyc, Ni MAbstract:A theoretical model was developed to study the electrical characteristics of a solid oxide steam electrolyzer (SOSE) for hydrogen production. The activation and concentration Overpotentials at the electrodes as well as the Ohmic Overpotential at the electrolyte were considered as the main sources of voltage loss. The Butler-Volmer equation, Fick's model, and Ohm's law were applied to characterize the Overpotentials. The theoretical model was validated as the simulation results agreed well with the experimental data from the literature. In the study of the component thickness effect, anode-support SOSE configuration was identified as the most favorable design. Further parametric analyses were performed to study the effects of material properties and operating conditions on the anode-supported SOSE cell performance. The results have shown that increasing electrode porosity and pore size can reduce the voltage loss. In the operation, both temperature and steam molar fraction can be increased to enhance the SOSE electrical efficiency. The pressure should be regulated depending on the current density. The electrochemistry model can be used to perform more analyses to gain insightful understanding of the SOSE hydrogen production principles and to optimize the SOSE cell and system designs. © 2007 International Association for Hydrogen Energy.link_to_subscribed_fulltex
Leung Mkh - One of the best experts on this subject based on the ideXlab platform.
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Mathematical modeling of ammonia-fed solid oxide fuel cells with different electrolytes
'Elsevier BV', 2008Co-Authors: Ni M, Leung Mkh, Leung DycAbstract:An electrochemical model was developed to study the ammonia (NH3)-fed solid oxide fuel cells with proton-conducting electrolyte (SOFC-H) and oxygen ion-conducting electrolyte (SOFC-O). Different from previous thermodynamic analysis, the present study reveals that the actual performance of the NH3-fed SOFC-H is considerably lower than the SOFC-O, mainly due to higher Ohmic Overpotential of the SOFC-H electrolyte. More analyses have been performed to study the separate Overpotentials of the NH3-fed SOFC-H and SOFC-O. Compared with the NH3-fed SOFC-H, the SOFC-O has higher anode concentration Overpotential and lower cathode concentration Overpotential. The effects of temperature and electrode porosity on concentration Overpotentials have also been studied in order to identify possible methods for improvement of SOFC performance. This study reveals that the use of different electrolytes not only causes different ion conduction characteristics at the electrolyte, but also significantly influences the concentration Overpotentials at the electrodes. The model developed in this article can be extended to 2D and 3D models for further design optimization. © 2008 International Association for Hydrogen Energy.link_to_subscribed_fulltex
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Modeling of methane fed solid oxide fuel cells: Comparison between proton conducting electrolyte and oxygen ion conducting electrolyte
'Elsevier BV', 2008Co-Authors: Leung Mkh, Leung Dyc, Ni MAbstract:An electrochemical model was developed to study the methane (CH4) fed solid oxide fuel cell (SOFC) using proton conducting electrolyte (SOFC-H) and oxygen ion conducting electrolyte (SOFC-O). Both the internal methane steam reforming (MSR) and water gas shift (WGS) reactions are considered in the model. Previous study has shown that the CH4 fed SOFC-H had significantly better performance than the SOFC-O. However, the present study reveals that the actual performance of the CH4 fed SOFC-H is considerably lower than the SOFC-O, partly due to higher Ohmic Overpotential of SOFC-H. It is also found that the CH4 fed SOFC-H has considerably higher cathode concentration Overpotential and lower anode concentration Overpotential than the SOFC-O. The anode concentration Overpotentials of the CH4 fed SOFC-H and SOFC-O are found to decrease with increasing temperature, which is different from previous analyses on the H2 fed SOFC. Therefore, high temperature is desirable for increasing the potential of the CH4 fed SOFC. It is also found that there exist optimal electrode porosities that minimize the electrode total Overpotentials. The analyses provided in this paper signify the difference between the CH4 fed SOFC-H and SOFC-O. The model developed in this paper can be extended to 2D or 3D models to study the performance of practical SOFC systems. © 2008 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex
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Electrochemical modeling of ammonia-fed solid oxide fuel cells based on proton conducting electrolyte
'Elsevier BV', 2008Co-Authors: Ni M, Leung Mkh, Leung DycAbstract:An electrochemical model was developed to study the NH3-fed and H2-fed solid oxide fuel cells based on proton conducting electrolyte (SOFC-H). The modeling results were consistent with experimental data in literature. It is found that there is little difference in working voltage and power density between the NH3-fed and the H2-fed SOFC-H with an electrolyte-support configuration due to an extremely high Ohmic Overpotential in the SOFC-H. With an anode-supported configuration, especially when a thin film electrolyte is used, the H2-fed SOFC-H shows significantly higher voltage and power density than the NH3-fed SOFC-H due to the significant difference in concentration Overpotentials. The anode concentration Overpotential of the NH3-fed SOFC-H is found much higher than the H2-fed SOFC-H, as the presence of N2 gas dilutes the H2 concentration and slows down the transport of H 2. More importantly, the cathode concentration Overpotential is found very significant despite of the thin cathode used in the anode-supported configuration. In the SOFC-H, H2O is produced in the cathode, which enables complete fuel utilization on one hand, but dilutes the concentration of O2 and impedes the diffusion of O2 to the reaction sites on the other hand. Thus, the cathode concentration Overpotential is the limiting factor for the H2-fed SOFC-H and an important voltage loss in the NH3-fed SOFC-H. How to reduce the concentration Overpotentials at both electrodes is identified crucial to develop high performance SOFC-H. © 2008 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex
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Parametric study of solid oxide steam electrolyzer for hydrogen production
'Elsevier BV', 2007Co-Authors: Leung Mkh, Leung Dyc, Ni MAbstract:A theoretical model was developed to study the electrical characteristics of a solid oxide steam electrolyzer (SOSE) for hydrogen production. The activation and concentration Overpotentials at the electrodes as well as the Ohmic Overpotential at the electrolyte were considered as the main sources of voltage loss. The Butler-Volmer equation, Fick's model, and Ohm's law were applied to characterize the Overpotentials. The theoretical model was validated as the simulation results agreed well with the experimental data from the literature. In the study of the component thickness effect, anode-support SOSE configuration was identified as the most favorable design. Further parametric analyses were performed to study the effects of material properties and operating conditions on the anode-supported SOSE cell performance. The results have shown that increasing electrode porosity and pore size can reduce the voltage loss. In the operation, both temperature and steam molar fraction can be increased to enhance the SOSE electrical efficiency. The pressure should be regulated depending on the current density. The electrochemistry model can be used to perform more analyses to gain insightful understanding of the SOSE hydrogen production principles and to optimize the SOSE cell and system designs. © 2007 International Association for Hydrogen Energy.link_to_subscribed_fulltex
