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Abstract: Solid oxide fuel cells (SOFCs) are very promising for their potential applications as power generators. However, the cost of these cells needs to be significantly reduced to make them a commercial success. Cost of the materials is a significant component of the overall cost. An improvement of the power density with respect to the weight of the cell, termed as gravimetric power density in this study, can help to achieve a lower material cost. On the other hand, a compact design is required for both man-portable and stationary powerhouse applications. The power density with respect to the overall volume of the cell is termed as volumetric power density in this study. A nonlinear constrained multiobjective optimization study using a lexicographic approach is performed to maximize the gravimetric and the volumetric power density of a tubular SOFC. The decision variables are the radius of the anode channel, the cell length, and the annulus size. To be used for optimization studies, a detailed steady state model is developed that can capture changes in the concentration, activation, and ohmic losses due to changes in the decision variables. The model is extensively validated with experimental data collected from an industrial cell spanning a wide range of temperatures, H2 flow rates, and DC polarizations. Although the model predictions are found to be satisfactory for most operating conditions, a significant mismatch between the simulation results and the experimental data is observed when the H2 flow rate is low. The validation study helps to identify the feasible region for the optimization study. The optimization study shows that significant improvements in both the power densities are possible for all the operating conditions considered in this study. The electrical efficiency of the cell also gets improved due to the optimization. In one of the operating conditions, about 30% improvement in the gravimetric power density and about 65% improvement in the volumetric power density are obtained due to the optimization. The percentage changes of the decision variables compared to their base case values are found to be similar for all the voltages other than the voltages close to the open circuit potential (OCP). [Copyright &y& Elsevier]

Abstract: In this paper, the impact of the design and operating parameters of a tubular Solid Oxide Fuel Cell (SOFC) is studied using a well-validated steady-state model. The profiles of species concentrations and pressure in the flow channels when the cell terminal voltage is changed are studied. In addition, both the axial and radial profiles of the species concentrations inside the electrodes are presented. The model is also used to study the effects of the parameters that can significantly influence the design criteria of an anode-supported tubular SOFC. The effects of the flowrate of , inlet pressure, and the cell temperature on the power output from the cell are studied. Cell characteristic parameters such as the porosity of the electrodes, effective diffusivity of the species, and the rate of the electrochemical reactions are varied and their impact on the cell performance is observed. The influence of the cell design parameters such as the thickness of the electrodes and the electrolyte on the steady-state polarization curve are also studied. Finally, a dimensional study is presented. In the dimensional study, the radius of the anode flow channel, the length of the cell, and the annulus size are varied keeping the solid volume and the total cell volume constant. This study shows that it is possible to design guidelines for the optimum performance of the cell. [Copyright &y& Elsevier]

In this paper, we describe a model for a micro photosynthetic power cell ( μ PSC). μ PSC is an electrochemical device which harnesses electrons and protons from the electron transport chains of photosynthesis (in the presence of light), and respiration (in the absence of light) occurring inside an oxygenic photosynthetic organism to generate electricity. μ PSC has been identified as a potential power generating device for low power applications. A one dimensional model for a μ PSC based on mass balances of species in the anode and cathode chambers considering unsteady one dimensional diffusion is developed. The governing equations are solved to obtain the v − i characteristics of a μ PSC device. The unknown parameters in the model are estimated from experimental data. The model with its estimated parameters is validated using test v − i characteristic data. Simulation analysis is performed to understand performance improvement possibilities. Explicit optimization formulations to identify promising device designs are also explored. [ABSTRACT FROM AUTHOR]

Highlights: [•] Qualitative analysis of data series is cast for the first time as a shape constrained spline fitting problem. [•] Shape constrained spline fitting is generalized to include optimization of change-point locations. [•] The generalized shape constrained spline fitting is solved through branch-and-bound optimization. [•] Benefits and limitations of the provided method and its applicability to fault diagnosis are carefully explained. [Copyright &y& Elsevier]

Abstract: To make the polymer electrolyte membrane fuel cells (PEMFC) commercially viable, further reduction in cost and improvement in performance are required. In this work, an innovative design of a PEMFC with multiple catalyst layers (CLs) is considered and the design variables, weight fraction of platinum on carbon (f pt ), platinum loading (m pt ), ionomer loading (f ionomer ) and thickness of all the CLs, are optimized for cost reduction and performance enhancement. In the first optimization study, the cell performance is maximized. The maximum current density of an optimized PEMFC with four CLs shows a significant improvement over the base case design at all operating voltages. In another optimization study, the platinum loading of the PEMFC with multiple CLs is minimized. With an increase in the number of catalyst layers, the platinum required to achieve the base case design current density is reduced. Using four CLs, a reduction of 17% (at 0.15Acm−2) to 60% (at 0.7Acm−2) in platinum loading is achieved in comparison to the base case design. In addition, the maximum power density of the PEMFC with multiple CLs is found to be superior to that of an optimized PEMFC with a single CL at all voltages. [Copyright &y& Elsevier]

Abstract: An appropriately designed sensor network is crucial for the success of any fault diagnostic strategy. Strategies for optimally locating sensors based on reliability-maximization and cost-minimization exist. While reliability and cost criteria have been used in selecting optimal sensor networks, the robustness of the network to uncertainties/errors in the underlying model and probability data have not been considered. In this article, we present robustness enhancing criteria for the design of sensor networks for reliable fault diagnosis. Robustness to modeling errors is incorporated by choosing a distributed sensor network. Robustness to available probability data is incorporated by minimizing the unreliability of fault detection with uncertain probability data. These criteria are incorporated in a lexicographic manner along with the overall reliability-maximization and cost-minimization objectives in a single optimization problem. Solution to this optimization problem results in a solution that is most reliable, robust and cost minimal in a lexicographic sense. The utility of the proposed approaches is demonstrated through the Tennessee Eastman case study. [Copyright &y& Elsevier]