Browsing by Author "Shiratori, Yusuke"

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Indirect internal reforming SOFC accommodating graded-catalytic domain fabricated by paper-structured catalyst
(Electrochemical Society Inc., 2019) Aydin, Özgür; Matsumoto, Go; Kubota, Atsushi; Tran, Dang Long; Sakamoto, Mio; Shiratori, Yusuke; 0000-0002-8814-6025; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Aydin, Özgür
Biogas can be directly utilized in Solid Oxide Fuel Cells (SOFCs), as it can be reformed to H2-rich mixture in the anode of SOFCs. However, the rate of reforming reaction significantly changes along the flow field due to the rapid conversion of CH4 in the inlet region. Since the reforming reactions are endothermic, a dramatic temperature gradient develops along the flow field, resulting in thermal stresses on the adjacent SOFC components. Taking the reforming reactions out of SOFC domain by indirect internal reforming reduces the thermal stresses to an extent, which can be further mitigated by designing a graded catalytic domain for an even temperature distribution. In this study, we demonstrate a reliable and durable operation of SOFC equipped with an indirect internal reformer graded in terms of catalyst loading.
Performance and Durability of One-Cell Module of Biogas-Utilizing SOFC Equipped with Graded Indirect Internal Reformer
(ELECTROCHEMICAL SOC INC, 65 SOUTH MAIN STREET, PENNINGTON, NJ 08534 USA, 2020) Aydin, Ozgur; Matsumoto, Go; Kubota, Atsushi; Dang Long Tran; Sakamoto, Mio; Shiratori, Yusuke; 0000-0002-8814-6025; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü
Utilization of biogas in Solid Oxide Fuel Cells (SOFCs) is an efficient way of renewable power generation. Despite some technical challenges, biogas can be reformed to H-2-rich fuel stream in the anodes of SOFCs. However, the reforming rate drastically drops toward the outlet of the flow field due to the rapid conversion of CH4 (biogas) in the inlet region. As the reforming reactions are endothermic, they cause large temperature gradients along the flow field, so that thermal stresses arise on the SOFC components. This problem can be resolved to an extent via taking the reforming reactions out of the SOFC domain (Indirect Internal Reforming), which however makes the heat transfer from SOFCs to the reforming domain also indirect. From the point of effective thermal integration, this study introduces an innovative indirect internal reforming concept. For totally eliminating the thermal stresses, it is necessary to homogenize the reforming rate, which can be achieved by designing a graded reforming domain. In this paper, we investigate the electrochemical performance and durability of an indirect internal reforming SOFC module featuring a graded reforming domain. (C) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.
Thermal stresses in SOFC stacks: the role of mismatch among thermal conductivity of adjacent components
(SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAKATATURK BULVARI NO 221, KAVAKLIDERE, TR-06100 ANKARA, TURKEY, 2021) Aydin, Ozgur; Matsumoto, Go; Shiratori, Yusuke; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Aydin, Ozgur
Generating power from renewable biogas in solid oxide fuel cells (SOFCs) is an environment-friendly, efficient, and promising energy conversion process. Biogas can be used in SOFCs via a reforming process for which dry reforming is more suitable as the reforming agent exists in the biogas mixture. Biogas can be directly reformed to H-2 -rich fuel stream in the anode chamber of a SOFC by the heat released during power generation. Exploiting the heat and water produced in the SOFC for internal reforming of biogas makes the energy conversion process very efficient; however, various challenges are reported. Thus, indirect internal reforming is opted for which a separate reforming domain is required. In an indirect internal reformer operating at usual conditions, dry reforming rate is quite high in the inlet and it decreases steeply toward the fuel outlet. Great temperature gradients develop over the reformer, since the dry reforming reaction is strongly endothermic. The abruptly varying rate of the reforming reaction affects the temperature fields in the adjacent components of SOFC and hence intolerable thermal stresses emerge on the SOFC components. In our preceding study, we graded the reforming domain, homogenized the temperature profile over the reforming domain, and executed performance and durability experiments. However, most of the experiments failed due to fracturing SOFC components hinting at existence of thermal stresses. In that study, we focused on minimizing the temperature gradients within the reforming domain; namely, we neglected the other processes. To eliminate the thermal stresses, we modeled the entire module of SOFC equipped with a reformer featuring a graded reforming domain. We found that the mismatch between the thermal conductivities of the adjacent module components is the major reason for the thermal stresses. When the mismatch is eliminated, thermal stresses disappear even if the reforming domain is not graded.