Publications by Arata Nakajo | EPFL Graph Search

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Electrochemical Impedance Spectroscopy (EIS) is extensively used to characterize Solid Oxide Cells (SOCs) to extract information on the elementary loss mechanisms. However, these individual mechanisms usually overlap in the frequency domain, requiring dedi ...

The solid oxide fuel cell (SOFC) is a direct energy conversion device, which allows the production of electricity with high efficiency while maintaining pollutant emissions at a low level. It offers better fuel flexibility and lower vulnerability to impuri ...

Structural reliability is a hurdle for the large-scale commercialisation of solid oxide fuel cell (SOFC). The cells are prone to cracking, due to the brittleness of their constitutive materials. In operation, the failure of one of them can arise from the non-uniform temperature distribution, coupled to detrimental interaction with the other stack components. In the long-term, the uneven distribution of temperature, gas composition, current density or overpotential induces non-uniform creep deformation and m

Structural stability issues in planar solid oxide fuel cells arise from the mismatch between the coefficients of thermal expansion of the components. The stress state at operating temperature is the superposition of several contributions, which differ depe ...

The mechanical failure of one cell is sufficient to lead to the end of service of a solid oxide fuel cell (SOFC) stack. Therefore, there is growing interest in gaining knowledge on the mechanical properties of the cell materials for stress analysis. This s ...

Researchers and developers typically use I-V curves (current vs. potential) as a means to demonstrate good data fitting of a model under experimental validation. Despite the popularity of this method, assessment of the results can be intuitive rather than mathematical, and usually, when such a demonstration occurs, information on the quality of the parameter estimation is not given. On the contrary, it has been shown that simple model fitting on I–V curves cannot give statistically reliable results on the v

The properties of sealing materials are important for the performance and reliability of solid oxide fuel cells (SOFCs). Even if the properties of a sealing material can be studied separately, it remains difficult to quantify the effect of an imperfect sea ...

Micro-compression tests were carried out on pillars of 60 mu m in diameter, milled by plasma focused ion beam in porous Yttria-Stabilized Zirconia (YSZ) pellets. The fracture properties were determined over a wide range of porosities (33 %-63 %) for 8YSZ a ...

The common technology for solid oxide fuel cells (SOFC) is based on a cermet (ceramic-metal composite) anode of nickel with yttria stabilized zirconia (YSZ), often used as the supporting structure. One of the main limitations of this technology is the tole ...

Structural stability issues in planar solid oxide fuel cells (SOFC) arise from the mismatch between the coefficients of thermal expansion (CTE) of the components. The stress state at operating temperature is the superposition of several contributions, which differ depending on the component. First, the cells undergo residual stresses due to the sintering phase during the manufacturing process. Furthermore, the load applied during the assembly of the stack to ensure the electric contact and flatten the cells

A model based on the Euler-Bernoulli theory is used to assess the sensitivity of residual stresses in solid oxide fuel cells to the mechanical properties and geometry of the constituents. It considers different cell configurations, characterised by the presence or not of a compensating layer, and a cathode based on either lanthanum strontium manganite (LSM) or lanthanum strontium cobaltite ferrite (LSCF). The implementation of creep in the model provides insights into the parameters that affect the zero-str

The temperature profile generated by a thermo-electro-chemical model was used to calculate the thermal stress distribution in a tubular solid oxide fuel cell (SOFC). The solid heat balances were calculated separately for each layer of the MEA (membrane ele ...

Lifetime prediction and improvement of solid oxide fuel cell (SOFC) devices require a reliable electrochemical model that supports the implementation of degradation phenomena. This study comprises two parts. This Part I describes the calibration of an elec ...

In order to characterize a new SOFC stack design, to investigate degradation processes and to validate models, a diagnostic test station was designed and realized. It allows to characterize repeat-elements locally by measuring the local potential, current density and temperature over the active area. The active area is segmented in 18 small electrically insulated measurement points (segments), in addition to a main segment. The profile of current density was investigated up to an average of 0.6A/cm2 and 67%

Our planar SOFC stacking technology uses unprofiled metallic interconnects (MIC) and thin cells of tape cast anode supported YSZ. The key element is the gas diffusion layer (GDL) between cell and MIC, which consists of so-called SOFConnex™. Using square ce ...

The performance of solid oxide cells is known to be dependent upon the density of three phase boundaries (TPB), but the potential for improving their effective electrocatalytic activity by morphological adjustments is imprecisely known. A spilling algorith ...

With a growing energy demand in a carbon-constrained society, fuels cells powered by renewable fuels, and specifically solid waste, are seen as interesting contributors to the energy portfolio. The alternative energy industry needs to reduce costs, enhance ...

Structural reliability and durability is a hurdle for the large-scale commercialisation of solid oxide fuel cell (SOFC). Because of the multiphysics nature of the problem, modelling is required to first gain knowledge and then alleviate mechanical failures. This chapter places the emphasis on stress analysis at the SOFC stack scale. A brief overview on the mechanical behaviour of the cell, sealing and gas diffusion layer materials is provided, along with a discussion on their implementation in finite-elemen

A CFD model was developed to predict with accuracy the local electrochemical performance in an operating solid oxide fuel cell. A particular focus was given on the study of performance limitations and degradation sources caused by the design of the fuel cell, by the choice of materials and components, or by improper operating points. The model is used to understand typical degradation effects observed on stacks tested in collaboration with HTCeramix - SOFCpower. The model is able to predict several degradat

Arata Nakajo

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Model-assisted identification of solid oxide cell elementary processes by electrochemical impedance spectroscopy measurements

Thermomechanical and Electrochemical Degradation in Anode-Supported Solid Oxide Fuel Cell Stacks

Current state of models for the prediction of mechanical failures in solid oxide fuel cells

Simulation of thermal stresses in anode-supported solid oxide fuel cell stacks. Part I: Probability of failure of the cells

Compilation of mechanical properties for the structural analysis of solid oxide fuel cell stacks. Constitutive materials of anode-supported cells

A Parameter Estimation Method for Fuel Cell Diagnostics

Modeling and Study of the Influence of Sealing on a Solid Oxide Fuel Cell

Fracture properties of porous yttria-stabilized zirconia under micro-compression testing

RedOx study of anode supported solid oxide fuel cell

Simulation of Thermal stresses in anode-supported solid oxide fuel cell stacks

Sensitivity of Stresses and Failure Mechanisms in SOFCs to the Mechanical Properties and Geometry of the Constitutive Layers

Modeling of thermal stresses and probability of survival of tubular SOFC

Electrochemical Model of Solid Oxide Fuel Cell for Simulation at the Stack Scale I. Calibration Procedure on Experimental Data

Simulation of thermal stresses in anode-supported solid oxide fuel cell stacks

Investigation of Local Electrochemical Performance and Local Degradation in an Operating Solid Oxide Fuel Cell

Design of 500 W Class SOFC Stack with Homogeneous Cell Performance

Characterization of local morphology and availability of triple-phase boundaries in solid oxide cell electrodes

Techno-Economic Optimization of an Integrated Biomass Waste Gasifier–Solid Oxide Fuel Cell Plant

Current State of Models for the Prediction of Mechanical Failures in Solid Oxide Fuel Cells

Modeling of Local Cell Degradation in Solid Oxide Fuel Cells: Cumulative Effect of Critical Operating Points