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Purpose: A reliability analysis of a solid oxide fuel cell (SOFC) system is presented for applications with strict constant power supply requirements, such as data centers. The purpose is to demonstrate the effect when moving from a module-level to a system-level in terms of reliability, also considering effects during start-up and degradation. Design/methodology/approach: In-house experimental data on a system-level are used to capture the behavior during start-up and normal operation, including drifts of the operation point due to degradation. The system is assumed to allow replacement of stacks during operation, but a minimum number of stacks in operation is needed to avoid complete shutdown. Experimental data are used in conjunction with a physics-based performance model to construct the failure probability function. A dynamic program then solves the optimization problem in terms of time and replacement requirements to minimize the total negative deviation from a given target reliability. Findings: Results show that multi-stack SOFC systems face challenges which are only revealed on a system- and not on a module-level. The main finding is that the reliability of multi-stack SOFC systems is not sufficient to serve as sole power source for critical applications such as data center. Practical implications: The principal methodology may be applicable to other modular systems which include multiple critical components (of the same kind). These systems comprise other electrochemical systems such as further fuel cell types. Originality/value: The novelty of this work is the combination of mathematical modeling to solve a real-world problem, rather than assuming idealized input which lead to more benign system conditions. Furthermore, the necessity to use a mathematical model, which captures sufficient physics of the SOFC system as well as stochasticity elements of its environment, is of critical importance. Some simplifications are, however, necessary because the use of a detailed model directly in the dynamic program would have led to a combinatorial explosion of the numerical solution space. [ABSTRACT FROM AUTHOR]

• System reliability analysis methodology for solid oxide fuel cell. • Combination of physical modeling and experiments. • Considering start-up effects and degradation during constant ower generation mode. A reliability analysis methodology for a multi-stack solid oxide fuel cell (SOFC) system is presented based on physical modeling and experimental data. The constructed failure probability function comprises three operation phases: (i) as-fabricated, (ii) start-up, and (iii) constant power generation. In-house experimental data are used to capture the behavior during start-up and normal operation, including drifts of the operating point due to degradation. The physics-based model provides a theoretical structure, but alternatives are discussed as well which are particularly suitable for experimentalists. The failure probability function can be used to calculate the reliability of a multi-stack SOFC system. The effect of operating stacks under over-load conditions in terms of degradation is discussed. It is shown that the customized failure probability function better explains the dependency on operating conditions compared to standard parametric distribution functions. The originality of this work is mainly twofold: first, the construction of the failure probability function of a multi-stack SOFC using experimental data for degradation as well as start-up on a system level; second, the focus on technological implications covered by the methodology. Hence, this systems engineering methodology aims to provide a process for reliability analysis in which the strength of both approaches are utilized, namely keeping sufficient parameter-dependency by means of the physics-based approach together with the simplicity of stochastic methods. This methodology is not limited to SOFC but may also be applicable to other modular (electrochemical) systems. Besides references on SOFC from a theoretical and experimental perspective, the extended bibliography also includes references on reliability analysis and engineering design, which may act as a starting point for related system analyses. [ABSTRACT FROM AUTHOR]

A solid oxide fuel cell-based (SOFC) power generation plant is analyzed with a view to performance as well as thermo-mechanical stresses. Emphasis is given to design and operation constraints of individual components as well as control-relevant aspects. We use a multi-physics modeling approach for simulations in design and off-design (part-load) under steady-state and transient conditions. Simulations confirm that the temperature distribution plays a pivotal role. For the SOFC the electrolyte is exposed to higher stresses compared to those in the electrodes. Disturbances in operation, e.g. in terms of current extraction, should be avoided because of resulting temperature excursions. This systems engineering perspective in which performance, durability issues and control aspects are combined, provides additional insights on a system level of practical relevance. [ABSTRACT FROM AUTHOR]