Experimental study on current distribution in parallel-connected solid oxide fuel cell strings

Abstract

To increase the power generated by solid oxide fuel cells (SOFCs), multiple cells have to be connected into a stack. Nonuniformity of cell performance is a worldwide concern in the practical application of stack, which is known to be unavoidable and caused by manufacturing and operating conditions. However, the effect of such nonuniformity on SOFCs that are connected in parallel has not been discussed in detail so far. This paper provides detailed experimental data on the current distribution within a stack with nonuniform cells in parallel connection, based on the basics of electricity and electrochemistry. Particular phenomena found in such a parallel system are the “self-discharge effect” in standby mode and the “capacity-proportional-load sharing effect” under normal operating conditions. It is believed that the experimental method and results proposed in this paper can be applied to other types of fuel cell or even other energy systems.

Key words： solid oxide fuel cells (SOFCs); stack; nonuniformity; parallel connection; current distribution

Acknowledgements

This work was supported by the National Key R&D Program of China (Grant No. 2021YFB2500400), the National Natural Science Foundation of China (Grant No. 22209149), and the Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang, China (Grant No. 2020R02015).

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11708-024-0941-9 and is accessible for authorized users.

Competing Interests

The authors declare that they have no competing interests.

Notations

OCV	Open circuit voltage/V
ΔOCV	Open circuit voltage difference between cell strings/mV
S1, S2, S3, S4, S5	Single cell string with four cells connected in series
RSD	Relative standard deviation of the cell string performance/%
ip	Parallel current/mA
pO2	Partial pressure of oxygen/%
R0	Ohmic resistance/Ω
ΔR0	Increment of ohmic resistance with shunt/Ω
Rp	Polarization resistance/Ω
ΔRp	Increment of polarization resistance with shunt/Ω
χ2	Goodness of fit for DRT analysis

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