Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Building and Real Estate | en_US |
| dc.contributor.advisor | Ni, Meng (BRE) | en_US |
| dc.creator | Wang, Chen | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/13275 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Modeling and optimization of fuel flexible and reversible solid oxide fuel cells for energy conversion and storage | en_US |
| dcterms.abstract | As a novel energy conversion device, solid oxide fuel cell (SOFC) is promising to address global energy issues and the associated environmental problems due to its high efficiency, excellent fuel flexibility, clean, and reversible operation (as solid oxide electrolyzer cell, SOEC). Despite some experimental and simulation studies of SOFC/SOEC have been conducted in terms of fuel flexibility, thermal management, as well as large-scale hydrogen production and energy storage systems, the oversimplification of the internal multi-physics processes (e.g. ignoring thermal effects or degrading the cell to a black box) has limited the detailed description and in-depth understanding of SOFC/SOEC. Therefore, the primary objective of this study is to investigate the operating characteristics of SOFC with specific focus on fuel flexibility and reversible features. In order to reveal the potential of a promising alternative fuel (glycerol), the performance and operating features of glycerol-based SOFC/SOEC is evaluated through comprehensive numerical models. Subsequently, the simple and efficient thermal management scheme for SOFC is proposed for long-term stability. Additionally, the feasibility and viability of integrating high-temperature steam electrolysis with renewable solar power plants for large-scale H2 production and energy storage is evaluated and analyzed. | en_US |
| dcterms.abstract | In this work, firstly, a numerical model is developed to study the glycerol-fueled SOFC. After model validation, the simulated SOFC demonstrates a performance of 7827 A·m-2 at 0.6 V, with a glycerol conversion rate of 49.0 % at 1073 K. Then, parametric analyses are conducted to understand the effects of operation conditions on cell performance. It is found that the SOFC performance increases with decreasing operating voltage or increasing inlet temperature. However, increasing either the fuel flow rate or steam to glycerol ratio could decrease the cell performance. It is also interesting to find out that the contribution of H2 and CO to the total current density is significantly different under various operating conditions, even sometimes CO dominates while H2 plays a negative role. This is different from our conventional understanding that usually H2 contributes more significantly to current generation. In addition, cooling measures are needed to ensure the long-term stability of the cell when operating at a high current density. | en_US |
| dcterms.abstract | Afterwards, in order to investigate the auxiliary effect of glycerol in the electrolysis process, a multi-physics model is developed to study the glycerol-assisted co-electrolysis process in SOEC, with a novel in-tube reformer to improve the fuel utilization and reduce the internal temperature difference. After model validation, the effects of key operating parameters on the electrochemical performance and temperature distribution of the system are investigated. It is found that glycerol assistance can significantly reduce the operating voltage of the SOEC co-electrolysis system, thus saving over 55% of electrical energy at 1073K. Besides, increasing operating voltage, operating temperature and cathode H2O molar fraction promote the co-electrolysis process, leading to an increase in cathode H2O/CO2 conversion. Optimal values of the anode/cathode flow rates (Qan=70-110 SCCM and Qca=125-175 SCCM) and the anode glycerol molar fraction (Xan,GL=0.05-0.15) are obtained to achieve both good electrochemical performance and uniform temperature distribution. And the temperature difference inside the cell can be greatly reduced through the in-tube reformer. | en_US |
| dcterms.abstract | Subsequently, the thermal management potential of the proposed novel in-tube reformer is further explored through the optimization framework based on Multi-physics simulation-Artificial neural network-Multi-objective genetic algorism, so as to improve the output performance and reduce the internal temperature difference in solid oxide fuel cell. First, a validated multi-physics model is developed for parametric simulation and generating dataset. Afterwards, a surrogate model is obtained by training an artificial neural network to predict the output performance and internal temperature field of solid oxide fuel cell. Finally, multi-objective genetic algorithm optimizations based on the surrogate model are performed to maximize the output performance and minimize the internal temperature difference under different operation strategies. It is found that compared to the conventional configuration (without in-tube reformer), the use of in-tube reformer can effectively promote the electrochemical reactions, increase the fuel utilization (up to 34.2%) and current density (up to 14.5%) while significantly reducing the maximum temperature difference (up to 85.5%) in the cell, resulting in a uniform current density and temperature distribution along the cell. | en_US |
| dcterms.abstract | Lastly, a comprehensive component-to-system model and optimization framework is developed to investigate the performance of a zero-emission H2 production system based on solar power plant and protonic ceramic electrolysis cell. Compared to previous system studies, the detailed description of cell internal operating characteristics is realized by integrating multi-physics simulation and artificial neural network. After parametric analyses, it is found that the system energy/exergy efficiency and co-generation performance is complicated by each subsystem. And the optimal system performance (ηth=50.63 %, Z=179.63 $·h-1 and ηex=33.03 %, Z=178.94 $·h-1, with the levelized cost of energy of 0.172 $·kWh-1 and H2 production cost of 6.497 $·kg-1) is obtained considering cell operating features and system energy-exergy-economic factors through multi-objective optimizations. Besides, the tradeoff between system maximum H2 production capacity and cell internal thermal conditions is revealed, allowing the convenient determination of the maximum system H2 production at acceptable temperature differences in the cell. | en_US |
| dcterms.abstract | The results of this study provide an insight into the multi-physics processes and thermal effects of glycerol-based SOFC/SOEC and solar-driven PCEC power-to-gas (H2) system under different operating conditions. The models and studies can facilitate the development and commercialization of SOFC/SOEC for efficient energy conversion and storage. | en_US |
| dcterms.extent | xxi, 162 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2024 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.LCSH | Solid oxide fuel cells | en_US |
| dcterms.LCSH | Glycerin | en_US |
| dcterms.LCSH | Energy storage | en_US |
| dcterms.LCSH | Hong Kong Polytechnic University -- Dissertations | en_US |
| dcterms.accessRights | open access | en_US |
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