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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]

The financial resilience of a Floating Production, Storage and Offloading (FPSO) plant is investigated through a hybrid modeling approach. With linked sub-models for economics, reliability and process safety, simulation results of the underlying transient nonlinear phenomena are shown, which represent the complex behavior of operation of the FPSO. The economics model is based on the Norwegian tax system with net cash flow as the main quantity. In the reliability model, statistical methods are used to obtain probability density functions for individual topside and subsea components. The safety model is centered around EHS 1 1 Environment, health, safety. time, in which a sufficiently high skill level is aimed to be maintained. Ample emphasis is given to parsimonious modeling, in which various engineering concepts are used in a way which avoids visual pollution. It is concluded that organizations that operate FPSO plants (under Arctic conditions) are not financially resilient per se , other than through a previously accumulated cushion of cash, which can rapidly deplete due to insufficient maintenance and repair of equipment, and even more so in case of major or frequent accidents. A (much) more conservative revenue stream should therefore be assumed as ground truth when considering exploration and exploitation of petroleum reservoirs in sensible (deep sea) ecosystems, as these are characterized by low natural resilience and also low potential for recovery. This work provides a set of analytical tools for technical managers, re-insurers and system engineers from the petroleum industry, which give a quantitative and more holistic perspective on the financial risks involved in such projects. The outlined general methodology, domain-driven design for implementation, and complete model description allow to rebuild applications for other contexts. • Case study using System Dynamics with heavy use of field data. • FPSO operation based on Norwegian economy and Arctic conditions. • Inter-/trans-disciplinary approach covering economics, technology, and safety. • Tutorial style and complete description of models and methods. • Introduction of financial resilience. [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]

We use a detailed solid oxide fuel cell (SOFC) model for micro-grid applications to analyze the effect of failure and degradation on system performance. Design and operational constraints on a component- and system level are presented. A degrees of freedom analysis identifies controlled and manipulated system variables which are important for control. Experimental data are included to model complex degradation phenomena of the SOFC unit. Rather than using a constant value, a spatially distributed degradation rate as function of temperature and current density is used that allows to study trajectory-based performance deterioration. The SOFC unit is assumed to consist of multiple stacks. The failure scenario studied is the loss of one individual SOFC stack, e.g. due to breakage of sealing or a series of fuel cells. Simulations reveal that degradation leads to significant drifts from the design operating point. Moreover, failure of individual stacks may bring the still operating power generation unit into a regime where further failures and accelerated degradation is more likely. It is shown that system design, dimensioning, operation and control are strongly linked. Apart from specific quantitative results perhaps the main practical contribution are the collected constraints and the degrees of freedom analysis. • System analysis of SOFC-based plant combining design, control and reliability aspects. • System simulation of degradation effects and failure scenario. • Parameter-dependent degradation rates with ohmic and activation polarization loss contributions. • Collection of design and operational constraints on plant level. • Set of controlled and manipulated variables of system for control. [ABSTRACT FROM AUTHOR]