TY - JOUR
T1 - New interconnector designs for electrical performance enhancement of solid oxide fuel cells
T2 - A 3D modelling study
AU - Guo, Meiting
AU - He, Qijiao
AU - Cheng, Chun
AU - Zhao, Dongqi
AU - Ni, Meng
N1 - Funding Information:
This work was supported by the Project of Strategic Importance funding scheme (Project ID: P0035168 ) from The Hong Kong Polytechnic University .
Funding Information:
Among SOFCs of various shapes and support types, the planar anode-supported SOFC is most popular due to its compactness and larger volume power density. To deliver a high voltage and high power output, multiple cells need to be connected in series by interconnector (IC) to assemble an SOFC stack. A repeating unit of SOFC stack consists of IC, gas channels, sealant and PEN (Positive electrode-Electrolyte-Negative electrode) components. Among all the constituent components, IC shoulders the functions of gas distribution, current collection, cells connection and mechanical support, which are of great significance for power output of an SOFC stack [1]. However, even for the commercialized SOFC [2], the SOFC stack performance is significantly lower than that of an SOFC single cell due to uneven gas distribution and additional ohmic loss at the IC-electrode contacts [3]. Even worse, the performance of SOFC stack could decrease over time due to the oxidation of metal alloy-based IC [4], which can significantly increase the contact resistance at the IC-electrode interfaces [5].For all the cases, the active area is 1.2 cm ? 1.2 cm. The heights of anode support layer (ASL), anode functional layer (AFL), electrolyte (ELE), cathode functional layer (CFL) and cathode current collection layer (CCCL) are 1 mm, 20 ?m, 10 ?m, 20 ?m and 50 ?m, respectively. The heights of ASL, AFL, ELE, CFL and CCCL are the same as those of the experiment cell [22]. To be more general, the height of ELE is set as 10 ?m in this study, rather than 8 ?m as that of experiment cell. The heights of channel and IC are 1 mm and 2 mm, respectively. Considering the practical fabrication difficulty and cost, the widths of ribs and channels for the base case (traditional IC design) are both 2 mm, the rib size is also restricted not less than 1 mm for all the IC designs to reduce the fabrication and machining difficulty. Based on the traditionally designed IC (case 1), only the shape, size or layout of ribs at cathode side are changed to design new IC while keep traditionally designed IC at anode side and all other geometrical parameters unchanged. To exclude the effect of total contact area between IC and electrode, all the cases except for case 6, 7, and 8 possess the same contact area, which occupies 50% of the total active area. Besides, the cases (case 6, 7, 8) with different contact area are also compared to better reveal the potential influential factor on electric power and performance degradation of SOFC.The multiphysics model is verified by comparing the theoretical I?V curves to that of experimental data [22] at three different operating temperatures. The experimental button cell is composed of anode support layer, anode function layer, electrolyte, cathode function layer, cathode current collector layer, and the corresponding constituent materials are respectively Ni-YSZ, Ni-YSZ, YSZ, LSM-YSZ, and LSM. The corresponding thicknesses of the components mentioned above are 1 mm, 20 ?m, 8 ?m, 20 ?m, 50 ?m, respectively. The microstructural parameters of the experiment cell are listed in Table 2. The molar ratio of H2 to H2O provided at anode side is 0.97:0.03, while the molar ratio of O2 to N2 provided at cathode side is 0.21:0.79. It can be seen from Fig. 2 that the simulation results agree well with experimental data [22], which proves the validity of the multi-physics model.For an anode-supported SOFC stack, the continuous straight rib-channel structure is the most widely used IC configuration. However, due to the coverage of ribs, it is difficult to convey oxygen timely to cathode region underneath ribs through horizontal oxygen diffusion, which degrades the local cell performance under the ribs, thus decreasing the overall electric power output. To solve the problem, we propose some new IC designs at cathode side with IC at anode side unchanged. Given the output voltage, the current densities are obtained and compared to elaborate the change of output performance of SOFC with different ICs.This work was supported by the Project of Strategic Importance funding scheme (Project ID: P0035168) from The Hong Kong Polytechnic University.
Publisher Copyright:
© 2022 Elsevier B.V.
PY - 2022/6/15
Y1 - 2022/6/15
N2 - Interconnector (IC) is a critical component of solid oxide fuel cell (SOFC) stack for current collection and gas distribution. However, the commonly used IC design causes low average SOFC stack performance due to the highly uneven distribution of gas (especially O2) in the porous electrodes and the contact resistance between IC and electrode. In this study, several unconventional IC designs are proposed and studied numerically by 3D multi-physics modeling. Compared with the traditional straight channel-based IC design, the new IC design can achieve more uniform distribution of O2 in the cathode of SOFC. As a result, the peak power density of SOFC can be improved by up to 27.86%. The performance improvement can be attributed to the discrete distribution of ribs, the reduction of rib size, and the spatial layout arrangement of discrete ribs, which may shorten gas diffusion path, current collection path, or both. It is also found that the performance degradation caused by IC oxidation is highly related to the contact area between IC and electrode. In addition, the increased parasitic power loss induced by the newly designed IC is less than 0.1% of the increased electric power, so it can be neglected.
AB - Interconnector (IC) is a critical component of solid oxide fuel cell (SOFC) stack for current collection and gas distribution. However, the commonly used IC design causes low average SOFC stack performance due to the highly uneven distribution of gas (especially O2) in the porous electrodes and the contact resistance between IC and electrode. In this study, several unconventional IC designs are proposed and studied numerically by 3D multi-physics modeling. Compared with the traditional straight channel-based IC design, the new IC design can achieve more uniform distribution of O2 in the cathode of SOFC. As a result, the peak power density of SOFC can be improved by up to 27.86%. The performance improvement can be attributed to the discrete distribution of ribs, the reduction of rib size, and the spatial layout arrangement of discrete ribs, which may shorten gas diffusion path, current collection path, or both. It is also found that the performance degradation caused by IC oxidation is highly related to the contact area between IC and electrode. In addition, the increased parasitic power loss induced by the newly designed IC is less than 0.1% of the increased electric power, so it can be neglected.
KW - Contact area
KW - Contact resistance
KW - Electrical power
KW - Multi-physics models
KW - Oxygen concentration
KW - Performance degradation
UR - http://www.scopus.com/inward/record.url?scp=85127692538&partnerID=8YFLogxK
U2 - 10.1016/j.jpowsour.2022.231373
DO - 10.1016/j.jpowsour.2022.231373
M3 - Journal article
AN - SCOPUS:85127692538
SN - 0378-7753
VL - 533
JO - Journal of Power Sources
JF - Journal of Power Sources
M1 - 231373
ER -
