Research

1160 KiB

Open AccessArticle

Modeling Analysis of Bi-Layer Ni-(ZrO₂)_x(Y₂O₃)_1−x Anodes for Anode-Supported Intermediate Temperature-Solid Oxide Fuel Cells

by Anna Enrico, Marco Cannarozzo and Paola Costamagna

Energies 2014, 7(9), 5647-5674; https://doi.org/10.3390/en7095647 - 28 Aug 2014

Cited by 9 | Viewed by 5842

Abstract

Intermediate temperature-solid oxide fuel cell (IT-SOFC) Ni-(ZrO₂)_x(Y₂O₃)_1−x (Ni-YSZ) anodes formed by two layers, with different thicknesses and morphologies, offer the possibility of obtaining adequate electrochemical performance coupled to satisfactory mechanical properties. We investigate [...] Read more.

Intermediate temperature-solid oxide fuel cell (IT-SOFC) Ni-(ZrO₂)_x(Y₂O₃)_1−x (Ni-YSZ) anodes formed by two layers, with different thicknesses and morphologies, offer the possibility of obtaining adequate electrochemical performance coupled to satisfactory mechanical properties. We investigate bi-layered Ni-YSZ anodes from a modeling point of view. The model includes reaction kinetics (Butler-Volmer equation), mass transport (Dusty-Gas model), and charge transport (Ohm’s law), and allows to gain an insight into the distribution of the electrochemical reaction within the electrode. Additionally, the model allows to evaluate a reciprocal overall electrode resistance 1/R_p ≈ 6 S·cm⁻² for a bi-layer electrode formed by a 10 µm thick active layer (AL) composed of 0.25 µm radius Ni and YSZ particles (34% vol. Ni), coupled to a 700 µm thick support layer (SL) formed by 0.5 µm radius Ni and YSZ particles (50% vol. Ni), and operated at a temperature of 1023 K. Simulation results compare satisfactorily to literature experimental data. The model allows to investigate, in detail, the effect of morphological and geometric parameters on the various sources of losses, which is the first step for an optimized electrode design. Full article

(This article belongs to the Special Issue Reacting Transport Phenomena in Solid Oxide Fuel Cells)

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6114 KiB

Open AccessArticle

Modeling and Analysis of Transport Processes and Efficiency of Combined SOFC and PEMFC Systems

by Abid Rabbani and Masoud Rokni

Energies 2014, 7(9), 5502-5522; https://doi.org/10.3390/en7095502 - 25 Aug 2014

Cited by 20 | Viewed by 7060

Abstract

A hybrid fuel cell system (~10 kWe) for an average family house including heating is proposed. The investigated system comprises a Solid Oxide Fuel Cell (SOFC) on top of a Polymer Electrolyte Fuel Cell (PEFC). Hydrogen produced from the off-gases of the SOFC [...] Read more.

A hybrid fuel cell system (~10 kWe) for an average family house including heating is proposed. The investigated system comprises a Solid Oxide Fuel Cell (SOFC) on top of a Polymer Electrolyte Fuel Cell (PEFC). Hydrogen produced from the off-gases of the SOFC can be fed directly to the PEFC. Simulations for the proposed system were conducted using different fuels. Here, results for natural gas (NG), dimethyl ether (DME) and ethanol as a fuel are presented and analysed. Behaviour of the proposed system is further investigated by comparing the effects of key factors such as utilisation factor, operating conditions, oxygen-to-carbon (O/C) ratios and fuel preheating effects on these fuels. The combined system improves the overall electrical conversion efficiency compared with standalone PEFC or SOFC systems. For the combined SOFC and PEFC system, the overall power production was increased by 8%–16% and the system efficiency with one of the fuels is found to be 12% higher than that of the standalone SOFC system. Full article

(This article belongs to the Special Issue Reacting Transport Phenomena in Solid Oxide Fuel Cells)

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1020 KiB

Open AccessArticle

Electrical Performance and Carbon Deposition Differences between the Bi-Layer Interconnector and Conventional Straight Interconnector Solid Oxide Fuel Cell

by Min Yan, Pei Fu, Qiuyang Chen, Qiuwang Wang, Min Zeng and Jaideep Pandit

Energies 2014, 7(7), 4601-4613; https://doi.org/10.3390/en7074601 - 22 Jul 2014

Cited by 6 | Viewed by 7572

Abstract

Carbon deposition considered in a solid oxide fuel cell (SOFC) model may be influenced by the operating voltage, inlet water/methane ratio, working temperature and pressure, inlet molar fraction of fuel and so on. The effects of these parameters in a planar SOFC implementing [...] Read more.

Carbon deposition considered in a solid oxide fuel cell (SOFC) model may be influenced by the operating voltage, inlet water/methane ratio, working temperature and pressure, inlet molar fraction of fuel and so on. The effects of these parameters in a planar SOFC implementing a novel bi-layer interconnector are not well understood. This paper is focused on the numerical study of carbon deposition and electrical performance of a bi-layer interconnector planar SOFC. The results illustrate that the electrical performance of the bi-layer interconnector SOFC is 11% higher than that of the conventional straight interconnector SOFC with initial state. After 120 days of operation, the electrical performance of the bi-layer interconnector SOFC has a slight decrease and more carbon deposit because of the increased electrochemical reaction rate. However, these differences minimize if higher operating voltages are involved. Full article

(This article belongs to the Special Issue Reacting Transport Phenomena in Solid Oxide Fuel Cells)

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1319 KiB

Open AccessArticle

Modeling of Proton-Conducting Solid Oxide Fuel Cells Fueled with Syngas

by Meng Ni, Zongping Shao and Kwong Yu Chan

Energies 2014, 7(7), 4381-4396; https://doi.org/10.3390/en7074381 - 09 Jul 2014

Cited by 21 | Viewed by 7636

Abstract

Solid oxide fuel cells (SOFCs) with proton conducting electrolyte (H-SOFCs) are promising power sources for stationary applications. Compared with other types of fuel cells, one distinct feature of SOFC is their fuel flexibility. In this study, a 2D model is developed to investigate [...] Read more.

Solid oxide fuel cells (SOFCs) with proton conducting electrolyte (H-SOFCs) are promising power sources for stationary applications. Compared with other types of fuel cells, one distinct feature of SOFC is their fuel flexibility. In this study, a 2D model is developed to investigate the transport and reaction in an H-SOFC fueled with syngas, which can be produced from conventional natural gas or renewable biomass. The model fully considers the fluid flow, mass transfer, heat transfer and reactions in the H-SOFC. Parametric studies are conducted to examine the physical and chemical processes in H-SOFC with a focus on how the operating parameters affect the H-SOFC performance. It is found that the presence of CO dilutes the concentration of H₂, thus decreasing the H-SOFC performance. With typical syngas fuel, adding H₂O cannot enhance the performance of the H-SOFC, although water gas shift reaction can facilitate H₂ production. Full article

(This article belongs to the Special Issue Reacting Transport Phenomena in Solid Oxide Fuel Cells)

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541 KiB

Open AccessArticle

Effects of Pretreatment Methods on Electrodes and SOFC Performance

by Guo-Bin Jung, Li-Hsing Fang, Min-Jay Chiou, Xuan-Vien Nguyen, Ay Su, Win-Tai Lee, Shu-Wei Chang, I-Cheng Kao and Jyun-Wei Yu

Energies 2014, 7(6), 3922-3933; https://doi.org/10.3390/en7063922 - 23 Jun 2014

Cited by 11 | Viewed by 6781

Abstract

Commercially available tapes (anode, electrolyte) and paste (cathode) were choosen to prepare anode-supported cells for solid oxide fuel cell applications. For both anode-supported cells or electrolyte-supported cells, the anode needs pretreatment to reduce NiO/YSZ to Ni/YSZ to increase its conductivity as well as [...] Read more.

Commercially available tapes (anode, electrolyte) and paste (cathode) were choosen to prepare anode-supported cells for solid oxide fuel cell applications. For both anode-supported cells or electrolyte-supported cells, the anode needs pretreatment to reduce NiO/YSZ to Ni/YSZ to increase its conductivity as well as its catalytic characteristics. In this study, the effects of different pretreatments (open-circuit, closed-circuit) on cathode and anodes as well as SOFC performance are investigated. To investigate the influence of closed-circuit pretreatment on the NiO/YSZ anode alone, a Pt cathode is utilized as reference for comparison with the LSM cathode. The characterization of the electrical resistance, AC impedance, and SOFC performance of the resulting electrodes and/or anode-supported cell were carried out. It’s found that the influence of open-circuit pretreatment on the LSM cathode is limited. However, the influence of closed-circuit pretreatment on both the LSM cathode and NiO/YSZ anode and the resulting SOFC performance is profound. The effect of closed-circuit pretreatment on the NiO/YSZ anode is attributed to its change of electronic/pore structure as well as catalytic characteristics. With closed-circuit pretreatment, the SOFC performance improved greatly from the change of LSM cathode (and Pt reference) compared to the Ni/YSZ anode. Full article

(This article belongs to the Special Issue Reacting Transport Phenomena in Solid Oxide Fuel Cells)

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794 KiB

Open AccessArticle

Optimization of the Interconnect Ribs for a Cathode-Supported Solid Oxide Fuel Cell

by Wei Kong, Xiang Gao, Shixue Liu, Shichuan Su and Daifen Chen

Energies 2014, 7(1), 295-313; https://doi.org/10.3390/en7010295 - 10 Jan 2014

Cited by 38 | Viewed by 6551

Abstract

A comprehensive mathematical model of the performance of the cathode-supported solid oxide fuel cell (SOFC) with syngas fuel is presented. The model couples the intricate interdependency between the ionic conduction, electronic conduction, gas transport, the electrochemical reaction processes in the functional layers and [...] Read more.

A comprehensive mathematical model of the performance of the cathode-supported solid oxide fuel cell (SOFC) with syngas fuel is presented. The model couples the intricate interdependency between the ionic conduction, electronic conduction, gas transport, the electrochemical reaction processes in the functional layers and on the electrode/electrolyte interfaces, methane steam reforming (MSR) and the water gas shift reaction (WGSR). The validity of the mathematical model is demonstrated by the excellent agreement between the numerical and experimental I-V curves. The effect of anode rib width and cathode rib width on gas diffusion and cell performance is examined. The results show conclusively that the cell performance is strongly influenced by the rib width. Furthermore, the anode optimal rib width is smaller than that for cathode, which is contrary to anode-supported SOFC. Finally, the formulae for the anode and cathode optimal rib width are given, which provide an easy to use guidance for the broad SOFC engineering community. Full article

(This article belongs to the Special Issue Reacting Transport Phenomena in Solid Oxide Fuel Cells)

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856 KiB

Open AccessArticle

Mathematical Modeling Analysis and Optimization of Key Design Parameters of Proton-Conductive Solid Oxide Fuel Cells

by Hong Liu, Zoheb Akhtar, Peiwen Li and Kai Wang

Energies 2014, 7(1), 173-190; https://doi.org/10.3390/en7010173 - 07 Jan 2014

Cited by 16 | Viewed by 7511

Abstract

A proton-conductive solid oxide fuel cell (H-SOFC) has the advantage of operating at higher temperatures than a PEM fuel cell, but at lower temperatures than a SOFC. This study proposes a mathematical model for an H-SOFC in order to simulate the performance and [...] Read more.

A proton-conductive solid oxide fuel cell (H-SOFC) has the advantage of operating at higher temperatures than a PEM fuel cell, but at lower temperatures than a SOFC. This study proposes a mathematical model for an H-SOFC in order to simulate the performance and optimize the flow channel designs. The model analyzes the average mass transfer and species’ concentrations in flow channels, which allows the determination of an average concentration polarization in anode and cathode gas channels, the proton conductivity of electrolyte membranes, as well as the activation polarization. An electrical circuit for the current and proton conduction is applied to analyze the ohmic losses from an anode current collector to a cathode current collector. The model uses relatively less amount of computational time to find the V-I curve of the fuel cell, and thus it can be applied to compute a large amount of cases with different flow channel dimensions and operating parameters for optimization. The modeling simulation results agreed satisfactorily with the experimental results from literature. Simulation results showed that a relatively small total width of flow channel and rib, together with a small ratio of the rib’s width versus the total width, are preferable for obtaining high power densities and thus high efficiency. Full article

(This article belongs to the Special Issue Reacting Transport Phenomena in Solid Oxide Fuel Cells)

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1049 KiB

Open AccessArticle

Three-Dimensional CFD Modeling of Transport Phenomena in a Cross-Flow Anode-Supported Planar SOFC

by Zhonggang Zhang, Jingfeng Chen, Danting Yue, Guogang Yang, Shuang Ye, Changrong He, Weiguo Wang, Jinliang Yuan and Naibao Huang

Energies 2014, 7(1), 80-98; https://doi.org/10.3390/en7010080 - 31 Dec 2013

Cited by 38 | Viewed by 8519

Abstract

In this study, a three-dimensional computational fluid dynamics (CFD) model is developed for an anode-supported planar SOFC from the Chinese Academy of Science Ningbo Institute of Material Technology and Engineering (NIMTE). The simulation results of the developed model are in good agreement with [...] Read more.

In this study, a three-dimensional computational fluid dynamics (CFD) model is developed for an anode-supported planar SOFC from the Chinese Academy of Science Ningbo Institute of Material Technology and Engineering (NIMTE). The simulation results of the developed model are in good agreement with the experimental data obtained under the same conditions. With the simulation results, the distribution of temperature, flow velocity and the gas concentrations through the cell components and gas channels is presented and discussed. Potential and current density distributions in the cell and overall fuel utilization are also presented. It is also found that the temperature gradients exist along the length of the cell, and the maximum value of the temperature for the cross-flow is at the outlet region of the cell. The distribution of the current density is uneven, and the maximum current density is located at the interfaces between the channels, ribs and the electrodes, the maximum current density result in a large over-potential and heat source in the electrodes, which is harmful to the overall performance and working lifespan of the fuel cells. A new type of flow structure should be developed to make the current flow be more evenly distributed and promote most of the TPB areas to take part in the electrochemical reactions. Full article

(This article belongs to the Special Issue Reacting Transport Phenomena in Solid Oxide Fuel Cells)

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