Planar solid oxide fuel cell modeling and optimization targeting the stack's temperature gradient minimization

Minimization of undesirable temperature gradients in all dimensions of a planar solid oxide fuel cell (SOFC) is central to the thermal management and commercialization of this electrochemical reactor. This article explores the effective operating variables on the temperature gradient in a multilayer SOFC stack and presents a trade-off optimization. Three promising approaches are numerically tested via a model-based sensitivity analysis. The numerically efficient thermo-chemical model that had already been developed by the authors for the cell scale investigations (Tang et al. Chem. Eng. J. 2016, 290, 252-262) is integrated and extended in this work to allow further thermal studies at commercial scales. Initially, the most common approach for the minimization of stack's thermal inhomogeneity, i.e., usage of the excess air, is critically assessed. Subsequently, the adjustment of inlet gas temperatures is introduced as a complementary methodology to reduce the efficiency loss due to application of excess air. As another practical approach, regulation of the oxygen fraction in the cathode coolant stream is examined from both technical and economic viewpoints. Finally, a multiobjective optimization calculation is conducted to find an operating condition in which stack's efficiency and temperature gradient are maximum and minimum, respectively

Simultaneous estimation of states and inputs in a planar solid oxide fuel cell using nonlinear adaptive observer design

An adaptive nonlinear observer design for the planar solid oxide fuel cell (SOFC) is presented in this work. This observer is based on a lumped parameter model of the SOFC and it can simultaneously estimate the inputs and the states of the system. Considering the inputs as unknown parameters is advantageous because some of the input parameters are not practically measurable in a SOFC stack. The asymptotic stability of the proposed observer is proven using the Lyapunov function method and is based on the concept of input-to-state stability for cascaded systems. The simulations show that the developed observer can track the temperature and species concentration profiles in the planar SOFC during step changes in the input variables and can simultaneously predict the input variables. The adaptive observer presented is valid for a wide operating range, requires fewer variables to be measured, and is robust to fluctuations in the input variables

Transesterification of Pyrolysed Castor Seed Oil in the Presence of CaCu(OCH3)2 Catalyst

Energy consumption is on the rise due to rapid technological progress and a higher standard of living. The use of alternative energy resources is essential to meet the rising energy demand and mitigate the carbon emissions caused due to use of fossil-based fuels. Biodiesel produced from non-edible oils such as castor seed oil (CO) can be used in diesel engines to replace fossil diesel. However, the quality and yields for CO biodiesel is low due to the presence of ricinolic acid C18:1OH (79%). In this study, two-stage conversion techniques were used to improve the yields and properties of CO biodiesel. The catalyst CaCu(OCH3)2 was prepared from waste eggshell and synthesized with copper oxide in the presence of methanol. The castor oil was subjected to pyrolysis at 450–500 ℃ and then transesterified in the presence of modified catalyst. The reaction parameters such as methanol-to-oil ratio and catalyst and reaction time were investigated, and the optimum combination was used to produce castor biodiesel from pyrolysis castor oil. Results showed that the cetane number and oxidation stability were increased by 7% and 42% respectively. The viscosity, density, flash point, and iodine value were decreased by 52%, 3%, 5% and 6%, respectively. The calorific values remained the same. This study suggests that pyrolyzed castor seed oil followed by transesterification in the presence of a modified catalyst gave better fuel properties and yields than the conventional transesterification process for biodiesel fuel production

Planar SOFC system modelling and simulation including a 3D stack module

A solid oxide fuel cell (SOFC) system consists of a fuel cell stack with its auxiliary components. Modelling an entire SOFC system can be simplified by employing standard process flowsheeting software. However, no in-built SOFC module exists within any of the commercial flowsheet simulators. In Amiri et al. (Comput. Chem. Eng., 2015, 78:10-23), a rigorous SOFC module was developed to fill this gap. That work outlined a multi-scale approach to SOFC modelling and presented analyses at compartment, channel and cell scales. The current work extends the approach to stack and system scales. Two case studies were conducted on a simulated multilayer, planar SOFC stack with its balance of plant (BoP) components. Firstly, the effect of flow maldistribution in the stack manifold on the SOFC's internal variables was examined. Secondly, the interaction between the stack and the BoP was investigated through the effect of recycling depleted fuel. The results showed that anode gas recycling could be used for managing the gradients within the stack, while also improving fuel utilisation and water management

SOFC Stack and System Modeling, Fault Diagnosis and Control

This report is an account of research and development activities undertaken by the Centre for Process Systems Computations, Department of Chemical Engineering at Curtin University, Western Australia in the area of solid oxide fuel cells. The focus of work of the group included 1) effect of cell macrostructure and microstructure on electrochemical performance with a view to optimise both macro- and micro-structure 2) electrochemistry modeling for simulating electrochemical performance 3) internal reforming aspects impacting performance at cell/stack and system levels 4) system level modeling investigating cell internal profiles (temperature, gas composition), homogeneity improvement, thermal management, anode recycle, fuel diversity, oxygen quality, and 5) monitoring for diagnostics, optimisation and control. The report summarizes work done over a period of 15 years and highlights areas of research gaps and future directions for research in the path to mass-scale commercialisation of the solid oxide fuel cell technolog

Targeting Phosphopeptide Recognition by the Human BRCA1 Tandem BRCT Domain to Interrupt BRCA1-Dependent Signaling.

Intracellular signals triggered by DNA breakage flow through proteins containing BRCT (BRCA1 C-terminal) domains. This family, comprising 23 conserved phosphopeptide-binding modules in man, is inaccessible to small-molecule chemical inhibitors. Here, we develop Bractoppin, a drug-like inhibitor of phosphopeptide recognition by the human BRCA1 tandem (t)BRCT domain, which selectively inhibits substrate binding with nanomolar potency in vitro. Structure-activity exploration suggests that Bractoppin engages BRCA1 tBRCT residues recognizing pSer in the consensus motif, pSer-Pro-Thr-Phe, plus an abutting hydrophobic pocket that is distinct in structurally related BRCT domains, conferring selectivity. In cells, Bractoppin inhibits substrate recognition detected by Förster resonance energy transfer, and diminishes BRCA1 recruitment to DNA breaks, in turn suppressing damage-induced G2 arrest and assembly of the recombinase, RAD51. But damage-induced MDC1 recruitment, single-stranded DNA (ssDNA) generation, and TOPBP1 recruitment remain unaffected. Thus, an inhibitor of phosphopeptide recognition selectively interrupts BRCA1 tBRCT-dependent signals evoked by DNA damage

Solid oxide fuel cell reactor analysis and optimisation through a novel multi-scale modelling strategy

The simulation of a solid oxide fuel cell (SOFC) that incorporates a detailed user-developed model was performed within the commercial flowsheet simulator Aspen Plus. It allows modification of the SOFC's governing equations, as well as the configuration of the cell's fuel-air flow pattern at the flowsheet level. Initially, the dynamic behaviour of single compartment of a cell was examined with a 0D model, which became the building block for more complex SOFC configurations. Secondly, a sensitivity analysis was performed at the channel (1D) scale for different flow patterns. Thirdly, the effect of fuel and air flow rates on the predominant distributed variables of a cell was tested on a 2D assembly. Finally, an optimisation study was carried out on the 2D cell, leading to a robust, optimal air distribution profile that minimises the internal temperature gradient. This work forms the foundation of future stack and system scale studies

An adaptive non-linear observer for the estimation of temperature distribution in the planar solid oxide fuel cell

Minimising the thermal gradients is extremely important in a planar solid oxide fuel cell (SOFC) forimproving the cell life. The estimation of the temperature distribution in the cell is necessary to achievethis objective through suitable control, since they are not generally measurable. In this work, we havedesigned a non-linear adaptive observer for estimating the temperatures inside the hydrogen fed planarSOFC. The observer design is based on a lumped parameter model of the SOFC. The stability of theproposed observer is proven using the Lyapunov function method and is based on the concept of input-to-state stability for cascaded systems. The simulations show that the developed observer can track the temperature and species concentration profiles in the planar SOFC during step changes in the cell current. The adaptive observer presented is valid for a wide operating range, requires fewer variables to be measured, and is robust to fluctuations in the inlet flows