Research Papers

J. Electrochem. En. Conv. Stor.. 2019;16(3):031001-031001-11. doi:10.1115/1.4042254.

In this research, cooling of polymer membrane fuel cells by nanofluids is numerically studied. Single-phase homogeneous technique is used to evaluate thermophysical properties of the water/Al2O3 nanofluid as a function of temperature and nanoparticle concentration. Four cooling plates together with four various fluids (with different nanoparticle concentrations) are considered for cooling fuel cells. The impact of geometry, Reynolds number, and concentration is investigated on some imperative parameters such as surface temperature uniformity and pressure drop. The results reveal that, among different cooling plates, the multipass serpentine flow field has the best performance. It is also proved that the use of nanofluid, in general, enhances the cooling process and significantly improves those parameters directly affecting the fuel cell performance and efficiency. By increasing the nanoparticle concentration by 0.006, the temperature uniformity index will decrease about 13%, the minimum and maximum temperature difference at the cooling plate surface will decrease about 13%, and the pressure drop will increase about 35%. Nanofluids can improve thermal characteristics of cooling systems and consequently enhance the efficiency and durability of fuel cells.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2019;16(3):031002-031002-12. doi:10.1115/1.4042063.

A computational fluid dynamics model for high-temperature polymer electrolyte fuel cells (PEFC) is developed. This allows for three-dimensional (3D) transport-coupled calculations to be conducted. All major transport phenomena and electrochemical processes are taken into consideration. Verification of the present model is achieved by comparison with current density and oxygen concentration distributions along a one-dimensional (1D) channel. Validation is achieved by comparison with polarization curves from experimental data gathered in-house. Deviations between experimental and numerical results are minor. Internal transport phenomena are also analyzed. Local variations of current density from under channel regions and under rib regions are displayed, as are oxygen mole fractions. The serpentine gas channels contribute positively to gas redistribution in the gas diffusion layers (GDLs) and channels.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2019;16(3):031003-031003-11. doi:10.1115/1.4042381.

A multiple model adaptive control (MMAC) methodology is used to control the critical parameters of a solid oxide fuel cell gas turbine (SOFC-GT) cyberphysical simulator, capable of characterizing 300 kW hybrid plants. The SOFC system is composed of a hardware balance of plant (BoP) component, and a high fidelity FC model implemented in software. This study utilizes empirically derived transfer functions (TFs) of the BoP facility to derive the MMAC gains for the BoP system, based on an estimation algorithm which identifies current operating points. The MMAC technique is useful for systems having a wide operating envelope with nonlinear dynamics. The practical implementation of the adaptive methodology is presented through simulation in the matlab/simulink environment.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2019;16(3):031004-031004-5. doi:10.1115/1.4042552.

The processes and mechanisms of LiNiO2 synthesis during the high-temperature solid state method, using Ni(OH)2 precursor and different lithium salts (Li2CO3 and LiOH), were revealed by the thermal (TG–DTA) and structural (X-ray diffraction (XRD)) analyses. Morphology characterization (scanning electron microscopy (SEM)) and the soluble lithium titration are carried out to support the findings. The results show that the synthetic processes of LiNiO2 generally include raw materials' dehydration, oxidation, and combination; also, the existence of lithium salts makes the oxidation of Ni(OH)2 relatively easier. Comparing the two lithium salts involved in the reactions, LiOH will bring about a transition oxide (Ni8O10) and lower the initial reaction temperature for LiNiO2 generation. In addition, a decent temperature under 800 °C, a preheat treatment in 500–600 °C, and a properly longer heating time are suggested to be significant for obtaining the ideal LiNiO2 materials.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2019;16(3):031005-031005-11. doi:10.1115/1.4042554.

The filter membrane made up of carbon nanostructure is one of the important components in proton exchange membrane fuel cell (PEMFC). The membrane while under operating conditions of a PEMFC is subjected to various dynamical loads due to the imposition of several input operating factors of the PEMFC. Hence, it is important to estimate optimal process parameters, which can maximize the strength of the membrane. Current studies in PEMFC focus on adsorption and transport-related properties of PEMFC membrane, without adequately investigating the mechanical strength of the membrane. This study proposes a multiphysics model of the membrane, which is used to extract the mechanical properties of the membrane by systematically varying various input factors of PEMFC. The extracted data are then fed into a neural search machine learning cluster to obtain optimal design parameters for maximizing the strength of the membrane. It is expected that the findings from this study will provide critical design data for manufacturing PEMFC membranes with high strength and durability.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2019;16(3):031006-031006-10. doi:10.1115/1.4042555.

Thermal management system (TMS) plays an essential part in improving the safety and durability of the battery pack. Prior studies mainly focused on controlling the maximum temperature and temperature difference of the battery pack. Little attention has been paid to the influence of the TMS on thermal runaway (TR) prevention of battery packs. In this paper, a heat pipe-based thermal management system (HPTMS) is designed and investigated to illustrate both the capabilities of temperature controlling and TR propagation preventing. Good thermal performance could be achieved under discharge and charge cycles of both 2 C rate and 3 C rate while the equivalent heat dissipation coefficient of the HPTMS is calculated above 70 W/(m2·K). In the TR propagation test triggered by overcharge, the surface temperature of the battery adjacent to the overcharged cell can be controlled below 215 °C, the onset temperature of TR obtained by the adiabatic TR test of a single cell. Therefore, TR propagation is prevented due to the high heat dissipation of the HPTMS. To conclude, the proposed HPTMS is an effective solution for the battery pack to maintain the operating temperature and improve the safety level under abuse conditions.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2019;16(3):031007-031007-14. doi:10.1115/1.4042726.

In this work, a model of a proton exchange membrane fuel cell (PEMFC) is presented. A dynamic performance characterization is performed to assess the cell transient response to input variables. The model used in the simulation considers three different phenomena: mass transfer, thermodynamics, and electrochemistry. The main sources of voltage loss are presented: activation, electrical resistance, and concentration. The model is constructed to avoid the use of fitted parameters, reducing the experimentation required for its validation. Hence, the electrochemical model is parameterized by physical variables, including material properties and geometrical characteristics. The model is demonstrated as a test-bed for PEMFC control system design and evaluation. Results demonstrate that the steady-state and dynamic behavior of the system are represented accurately. A case study is included to show the functionality of the model. In the case study, the effect of the purge valves at the fuel cell discharges is analyzed under different scenarios. Regular purges of the cathode and the anode are shown to achieve a good performance in the system avoiding reactant starvation in the cell. A closed-loop dynamic response is included as an example of the model capabilities for the design of fuel cell control strategies. Two variables were selected to be controlled: voltage and pressure difference across the membrane. A multivariate control strategy was tested and its dynamic response was analyzed. It was found that there was a strong interaction between the control loops, making the control of the system a challenge.

Commentary by Dr. Valentin Fuster
J. Electrochem. En. Conv. Stor.. 2019;16(3):031008-031008-6. doi:10.1115/1.4042727.

Ferrous nitrate/nickel oxide {Fe(NO3)2–NiO} nanocomposite was synthesized via two-step facile hydrothermal route. The nanocomposite exhibits crystalline structure as unveiled by X-ray diffraction (XRD) pattern, while as the scanning electron microscope (SEM) images divulge spherical morphologies for both Fe(NO3)2 as well as NiO nanoparticles differentiating from each other in size. Cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques were used to investigate supercapacitive behavior of the symmetrically fabricated nanocomposite electrode configuration using aqueous KOH as the electrolyte. The CV analyses demonstrate dominant electrical double layer capacitance (EDLC) behavior in the potential range of 0–1 V. From charge–discharge curves, the maximum specific capacitance calculated was 460 F g−1 corresponding to the energy density of 16 W h kg−1 at a high power density of 250 W kg−1. EIS data affiliate well with the CV and GCD results justifying the maximum contribution of specific capacitance due to double layer capacitance. The nanocomposite retained 84% of its original capacitance after 1000 cycles and yielded maximum efficiency of 78%.

Commentary by Dr. Valentin Fuster

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