Specific Cell Design Research Articles

Effect of pore size and electrolyte flow rate on the bubble removal efficiency of 3D pure Ni foam electrodes during alkaline water electrolysis

To further reduce the capital expenditure of alkaline water electrolyzers, an improvement in power density can still be achieved through process intensification. The change from traditional gap-cells to zero-gap cells has already been proven to be very promising in this respect. In the zero-gap design, macro-porous 3D structures are typically being used as electrodes. Here, pure nickel foams with different pore sizes in the range 450 – 3000 µm have been studied under well-controlled electrolyte flow conditions. To this end, a dedicated flow cell has first been constructed that allows for imposing the same relatively high flow rates on the order of 1 L/min that are typically encountered under industrial conditions. Our specific cell design was shown by computational fluid dynamic simulations to be able to homogenize the flow field before entering the electrodes. This is absolutely mandatory to reliably evaluate the intrinsic bubble removal efficiency of the differently sized foams. We then demonstrate that the effect of pore size and the electrochemical performance can be rationalized by considering the cell voltage as a function of electrochemical current density, i.e. the current divided by the theoretically available electrochemical surface area (ECSA) rather than by the projected electrode area. Based on this analysis, we were also able to quantify the bubble removal efficiency by estimating the effective fraction of the ECSA that is not impeded by bubble coverage.

Solid Oxide Fuel Cell Performance Analysis through Local Modelling

Solid Oxide Fuel Cells (SOFC) are an emerging technology among different fuel cell types since they are successfully used in stationary cogeneration units to produce heat and electricity. Different scale applications are proposed as alternative energy sources for residential usage and industrial power plants, reducing the greenhouse gas emissions which characterize fossil-fuel-based processes. Their spread is favoured by the development of proper simulation tools that allow system design optimization and control in real-time operations. For this purpose, model building and validation, through comparison with experimental observations, are fundamental steps to guarantee the simulation validity. A single-anode-supported planar SOFC with two possible cathodic current collector designs is tested in common operating conditions, evaluating the performance through EIS analysis and characteristic curves. These provide a preliminary validation for the proposed 2D steady state simulation code. This model, implemented in Fortran, makes it possible to forecast the main SOFC local properties on both the anodic and cathodic sides. The key point of the code is the electrochemical kinetics, based on a semi-empirical approach where requested parameters, derived from fitting of experimental results, are introduced in physically based equations. In this way, the influence of specific cell design on system performance is evaluated.

Cost Reduction through Cell Design Optimization for Vehicle Requirements-From Active Material to Vehicle Product Portfolios

The cost situation for lithium-ion batteries is one of the key limitations for the market potential of electric vehicles and has been covered by several authors from the industry and science sector. This work addresses the relation between active material properties, cell design and vehicle requirements. The results of this investigation show that the efficient use of the cell properties in the vehicle application will be decisive for the competitiveness of OEMs and battery suppliers. The center of the research is a cell model in which different active material properties, cell formats and electrode layouts can be implemented flexibly. Within a constant volume of a standardized cell housing the variation of the electrode loadings leads to relationships between the storable energy and the power of the cell. The costs determined for each specific cell design then allow describing the relation between the power to energy ratio of a cell and its energy specific costs for current and future materials. The optimal cost situation is reached when the P/E-ratio of the cell matches the required P/E-ratio of the storage system. In a broad vehicle portfolio this means a specific cell would be required for each car project. This potentially large number of cell types seems unfavorable for OEMs to handle. Therefore a genetic algorithm optimization is applied to determine the cost-optimal number and specifications of cells to address a certain vehicle portfolio. For these optimizations further restrictions such as voltage level limitations are considered as well. The tool derived from these considerations can support OEMs as well as cell & material suppliers to find the optimal modular kit for their lithium-ion cell strategy considering individual customer requirements.

Classification of Mechanical Failure in SOFC and Strategy for Evaluation of Operational Margin

Mechanical damages and their formation mechanisms in SOFC were investigated. Generalized schemes of the occurrence of mechanical failures were summarized, and among them, common features in various cell designs were extracted. They were discussed in three categories of (a) deformation of a cell due to its asymmetry, (b) propagation of mechanical defects, and (c) effects of irregular operations. Prototype-cell experiments were designed to reproduce the key features, and to develop a quantitative evaluation scheme of operational margins for prediction of the short and long term reliability of a specific cell design. Numerical calculation tools based on finite element method and homogenization method are designed. Experimental methods were developed to acquire high-temperature mechanical behaviors of the materials and cell stacks.

Investigation of H2 and CO Oxidation on Ni-CeO2 Electrodes Using a Specially Designed Three-Electrode Configuration

The electrochemical oxidation of H2 and CO was studied on Ni- CeO2 anodes using a specific cell design characterized by a Luggin-type reference electrode. The consistency of this configuration was verified theoretically using a numerical model. The oxidation rates were measured by cyclic- voltammetry and electrochemical impedance spectroscopy (EIS) at temperatures between 700 and 800{degree sign}C and at different H2 and CO partial pressures. EIS results were analyzed following a validation and deconvolution procedure. EIS fitting parameters were rationalized using a method developed for conventional Ni-YSZ anodes. Typically, two main arcs composed the complex impedance of Ni/CeO2. In H2, the charge transfer reactions were not limiting but the rate of the process related to the lower peak-frequency arc decreased with anodic overpotential, indicating diffusion limitations in this region. In CO, charge transfer limitations were evident. The design and procedure developed in this study is useful for characterizing the processes in SOFC anodes.

A fast response smectic LCD using induced polarization

In this paper, a general performance of the PSS‐LCD or Polarization Shielded Smectic Liquid Crystal Display is discussed. This smectic base LCD does not use any spontaneous polarization, but uses induced polarization just sa me with current nematic base LCDs. Specific initial molecular alignment as well as specific cell design realizes ext remely fast optical response speed with native wide viewing angle. Moreover, this performance is provided by full compatible electronics for current conventional LCDs. A general performance of the PSS‐LCD is introduced herein.

Strategic Implications of Manufacturing Cell Formation Design

Cell formation design in cellular manufacturing systems (CMS) has been the focus of recent manufacturing research literature. A great amount of research has been published addressing either technical issues (e.g. part‐machine grouping algorithms) or operational issues (e.g. planning and scheduling in the CMS). Research addressing strategic issues in cell formation design has been minimal. Addresses strategic considerations in cell formation design, specifically, the linkage and relationships between specific cell design issues and the firm′s competitive advantage in the marketplace. It is demonstrated that cell formation design decisions must be addressed in alignment with the firm′s strategic plan and manufacturing competitive priorities.

The effects of trap-induced lifetime variations on the design and performance of high-efficiency GaAs solar cells

The authors investigate the impact of Shockley-Read-Hall (SRH) lifetime behavior directly on GaAs solar cell performance and design optimization for various lifetime-limiting defects, characterized by trap position, cross section, and trap density. It is demonstrated theoretically and experimentally, for a specific cell design, how far GaAs cell efficiency can be from the optimum efficiency if certain types of bulk defects limit the lifetime and are not properly accounted for. A realistic situation is considered where cell designers/manufacturers know the bulk lifetime at some nominal carrier concentrations but are unaware of the trap characteristics or defect responsible for this lifetime. An improved GaAs p/n heteroface cell design is proposed. This design utilizes a high-low junction and a thin base, with AlGaAs back-surface passivation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A model for capacity planning of flexible robotic assembly systems

This paper presents a cost-based model for capacity planning of Flexible Robotic Assembly Systems capable of handling batch assembly of multiple end products. The non-linear integer programming model is based on a specific cell design procedure that considers two important aspects, such as robot selection, and cell configuration, in forming the assembly cell. The model incorporates stochastic variations in the batch arrival rate, batch size, and processing times. The solution procedure for the model is discussed and an example problem is used to demonstrate the use of the model for real world applications.

A p‐AlxGa1‐xAs‐p‐GaAs‐n‐GaAs concentrator solar cell design without a collection grid

AbstractA concentrator solar cell is designed without a front contact collact collection grid. Its p‐AlxGa1–xAs‐p‐GaAs‐n‐GaAs epitaxial structure on a p‐GaAs substrate allows for collection of the carriers generated in the p region through the substrate while carriers generated in the n region are collected through an edge ring contact.Although cell efficiency depends on specific cell design, it has been found that such a device may work efficiently at over 100 sun incident radiation levels.