Research Papers

J. Electrochem. En. Conv. Stor.. 2018;15(4):041001-041001-10. doi:10.1115/1.4039418.

To investigate the efficiency of dodecafluoro-2-methylpentan-3-one (C6F-ketone) extinguishing agent on suppressing the lithium titanate battery fire, an experimental system was devised to implement suppression test. One 5 kW electric heater was placed at the bottom of the battery to cause the thermal runaway. The extinguishing agents of CO2 and C6F-ketone with different pressures were performed to suppress lithium ion battery (LIB) fire. The temperatures of the battery and the flame, the ignition time, the release time of the agent, the release pressure of the agent, the time to extinguish the fire, the battery mass loss, and the mass of used agent were obtained and compared in different aspects. The experimental results reveal that the lithium titanate battery fire can be suppressed by C6F-ketone within 30 s; the results further show that CO2 is incapable of fully extinguishing the flame over the full duration of the test carried out. Therefore, C6F-ketone extinguishing agent is a good candidate to put down the LIB fire.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2018;15(4):041002-041002-9. doi:10.1115/1.4039504.

In this research study, the performance in battery running and charging of an original circuit design is compared with the performance between the developed DC–DC boost converter running and charging replication circuit design. Bedini generators are a kind of magnetic generator designed by John Bedini on the basis of zero point technology. The generator serves as a self-battery charger. In this study, the two types of circuit design, namely, the original and the replication, are examined in terms of performance in battery running and charging. The DC–DC boost converter offers greater voltage boost capabilities and hence has the potential to enhance step-up power conversions. The novel design was a prototype of the six-pole eight-neodymium magnet generator, which potentially offers free energy and could therefore serve as an alternative means of addressing energy needs when the current nonrenewable fuel sources have been wholly depleted in the future. The coefficient of performance (COP) for the battery performance of both designs is calculated in this study in order to allow comparisons to be drawn. Upon analysis, it is discovered that the DC–DC boost converter circuit is both practical and efficient, offering a high level of step-up power conversion capacity for battery running and charging. The COP of the new system provides a significant increase in COP when compared to the original design.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2018;15(4):041003-041003-5. doi:10.1115/1.4039458.

The design of efficient devices for the photoelectrochemical (PEC) water splitting for solar-to-hydrogen (STH) processes has gained much attention because of the fossil fuels crisis. In PEC water splitting, solar energy is converted to a chemical fuel for storage. From the viewpoint of economics and large-scale application, semiconductor photoelectrodes with high stability and efficiency are required. However, although numerous materials have been discovered, challenges remain for their commercialization. Among the enormous number of investigated materials, layered transition metal dichalcogenide (TMD)-based photoelectrodes show attractive performance in PEC devices owing to their suitable narrow bandgaps, high absorption capacity, and fast carrier transport properties. A comprehensive review of TMDs photoelectrodes for STH processes would help advance research in this expanding research area. This review covers the physicochemical features and latest progress in various layered-structure TMD-based photoelectrodes, especially MoS2, as well as various approaches to improve the PEC performance and stability by coupling with active carbon materials, including graphene, CNTs, and conductive carbon. Finally, we discuss the prospects and potential applications for STH processes. This review paper gives insights into the fundamental concepts and the role of active chemical species during the STH conversion processes and their influence in enhancing PEC water splitting performance.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2018;15(4):041004-041004-8. doi:10.1115/1.4039662.

Cell temperature uniformity inside most batteries is important, because temperature variation leads to cell resistance variation and thus cell voltage variation during discharge–charge cycling. Voltage variation among the cells leads to accelerated degradation of the overall battery. Goal of this work was to improve cell temperature uniformity of the General Electric DurathonTM E620 battery module (600 V class, 20 kWh, 280 °C nominal temperature), which uses the sodium metal halide chemistry and convection air cooling. Computation fluid dynamics (CFD) study and bench-top testing were used to evaluate multiple battery design options. The optimized battery design was prototyped and tested, which demonstrated 3.5× increase in cooling power and 30% reduction in cell temperature difference during discharge–charge cycling. Cell temperature difference during battery float was reduced 50%. The hardware design changes were implemented into production batteries, which showed 450% improvement in reliability performance during discharge–charge cycling.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2018;15(4):041005-041005-12. doi:10.1115/1.4039788.

Proton exchange membrane (PEM) fuel cells suffer noticeable power loss when operated at high power output. This paper proposes a hybridization scheme for a PEM fuel cell/supercapacitor system operating in three different regimes: “Flat,” “Uphill,” and “Downhill.” Transitions among operational regimes are governed by logical statements, which compare operational parameters against threshold values. These threshold values were obtained using a genetic optimization (GO) algorithm. The hybridization problem is analyzed in a simulation environment before the solution is implemented in an actual laboratory prototype. Results and discussion are presented to demonstrate the soundness of the proposed solution. The approach presented in this paper is suitable for applications where sudden changes in power demand occur.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2018;15(4):041006-041006-8. doi:10.1115/1.4039789.

A method which allows for the comparison of polymer electrolyte fuel cell (PEFC) bipolar plates (BPs) with various channel dimensions is outlined here. It is applied to data from an experiment with different channel and land width and channel depth combinations for interdigitated and parallel designs. Channel and land width and channel depth varied from 0.25 mm to 1 mm on six different BP designs, and two stoichiometries were tested. Each condition was performed three times for repeatability. The method calculates the performance of each condition after accounting for reversible voltage and overpotential changes due to varying pressure and after eliminating ohmic resistance as a variable. In these data, the interdigitated flow field outperformed the parallel flow field. Designs are compared using the BP permeability as a benchmark metric. The method then calculates the area-specific ohmic resistance (ASR) of the cell. It was difficult to draw hard conclusions about changes in the ASR between flow field designs, but there may be more consistent liquid water removal from the gas diffusion layer (GDL) with smaller channel dimensions. It was found that concentration losses seem to be primarily a result of channel width, rather than channel depth.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2018;15(4):041007-041007-9. doi:10.1115/1.4039944.

Chemical process optimization problems often have multiple and conflicting objectives, such as capital cost, operating cost, production cost, profit, energy consumptions, and environmental impacts. In such cases, multi-objective optimization (MOO) is suitable in finding many Pareto optimal solutions, to understand the quantitative tradeoffs among the objectives, and also to obtain the optimal values of decision variables. Gaseous fuel can be converted into heat, power, and electricity, using combustion engine, gas turbine (GT), or solid oxide fuel cell (SOFC). Of these, SOFC with GT has shown higher thermodynamic performance. This hybrid conversion system leads to a better utilization of natural resource, reduced environmental impacts, and more profit. This study optimizes performance of SOFC–GT system for maximization of annual profit and minimization of annualized capital cost, simultaneously. For optimal SOFC–GT designs, the composite curves for maximum amount of possible heat recovery indicate good performance of the hybrid system. Further, first law energy and exergy efficiencies of optimal SOFC–GT designs are significantly better compared to traditional conversion systems. In order to obtain flexible design in the presence of uncertain parameters, robust MOO of SOFC–GT system was also performed. Finally, Pareto solutions obtained via normal and robust MOO approaches are considered for parametric uncertainty analysis with respect to market and operating conditions, and solution obtained via robust MOO found to be less sensitive.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2018;15(4):041008-041008-7. doi:10.1115/1.4039858.

Code stability is a matter of concern for three-dimensional (3D) fuel cell models operating both at high current density and at high cell voltage. An idealized mathematical model of a fuel cell should converge for all potentiostatic or galvanostatic boundary conditions ranging from open circuit to closed circuit. Many fail to do so, due to (i) fuel or oxygen starvation causing divergence as local partial pressures and mass fractions of fuel or oxidant fall to near zero and (ii) nonlinearities in the Nernst and Butler–Volmer equations near open-circuit conditions. This paper describes in detail, specific numerical methods used to improve the stability of a previously existing fuel cell performance calculation procedure, at both low and high current densities. Four specific techniques are identified. A straight channel operating as a (i) solid oxide and (ii) polymer electrolyte membrane fuel cell is used to illustrate the efficacy of the modifications.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2018;15(4):041009-041009-7. doi:10.1115/1.4040058.

This work defines and implements a technique to predict water activity in proton exchange membrane fuel cell. This technique is based on the electrochemical impedance spectroscopy (EIS) as sensor and adaptive neuro-fuzzy inference system (ANFIS) as estimator. For this purpose, a proton exchange membrane fuel cell (PEMFC) model has been proposed to study the performances of the fuel cell for different operating conditions where the simulation model for water activity behavior is in the proposed structure. The technique based on ANFIS predicts the PEM fuel cell relative humidity (RH) from the EIS. For creation of ANFIS training and checking database, a new method based on factorial design of experimental is used. To check the proposed technique, the ANFIS estimator will be compared with the output humidity relative observation.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Electrochem. En. Conv. Stor.. 2018;15(4):044501-044501-4. doi:10.1115/1.4039705.

A planar solid oxide fuel cell (SOFC) was fabricated using a commercial Ni/yttria-stabilized zirconia (YSZ) anode support, an YSZ/gadolinium-doped ceria (GDC) thin-film electrolyte, and a composite cathode of La0.6Sr0.4Co0.2Fe0.8O3/Gd0.1Ce0.9O1.95 (LSCF/GDC). A small, three-cell, SOFC stack is assembled using 10 cm × 10 cm single cells, metallic interconnects, and glass-based sealing. The stack performance was examined at various fuel flow rates of H2 + N2 and air at a fixed temperature of 750 °C. The three-cell stack with a crossflow design produced peak power density of 0.216 W/cm2 or about 39 W total power at 750 °C.

Commentary by Dr. Valentin Fuster

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