Electrode Heating Research Articles

Nanoscale nonlocal thermal transport and thermal field emission in high-current resonant tunnel structures

We present a nonlinear model of thermal field emission in resonant tunneling nanostructures with multiple barriers and potential wells, based on an accurate determination of the quantum potential shape and a rigorous solution of the Schrödinger equation, while considering thermal balance. The model applies to vacuum and semiconductor resonant tunnel diode and triode structures with two and three electrodes and to the general case of two-way tunneling with electrode heating. The complete balance of heat release and transfer is accounted for, with heat transport considered ballistic. This approach can also be extended to the non-stationary case, incorporating the influence of space charge. The short flight time of electrons in such structures makes them promising for the fabrication of THz devices.

Enlargement of the Surface Area of High-Entropy Alloys with Acid Treatment as Positive Electrode for High Specific Capacitance Supercapacitors.

High-entropy alloys (HEAs), containing five or more elements in equal proportions, have recently made significant achievements in materials science due to their remarkable properties, including high toughness, excellent catalytic, thermal, and electrical conductivity, and resistance to wear and corrosion. This study focuses on a HEA composed of 23Fe-21Cr-18Ni-20Ti-18Mn, synthesized via ball milling. The alloy was treated with hydrochloric acid (HCl) to enhance its active surface area. The untreated HEA and the HCl-treated HEA (HEA-T) were then evaluated as potential cathode materials for supercapacitors (SCs). X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) confirmed that the HEA's composition and crystalline structure remained stable during acid treatment, with no new phases forming. The acid treatment significantly increased the surface area by ~20 times, the pore volume by ~10 times, and improved microstructural homogeneity. The HEA-T electrode demonstrated superior specific capacitance, lower internal resistance, and better cycling stability than the untreated HEA electrode. At 0.5 A/g current density, the specific capacitance (Csp) of the HEA-T was 600 F/g, approximately two times higher than the untreated HEA. This enhanced performance suggests that the HEA-T electrode could lead to the development of high-performance SCs.

(Invited) Hyper-Multimodal Sensing with Heater-Integrated Fluidic Resonators

Mechanical resonators with embedded fluidic channels (hereafter referred to as fluidic resonators), known as suspended micro/nanochannel resonators (SMRs or SNRs) [1, 2], allow precise and sensitive measurements of single micro/nanoparticles or single cells in transit, adsorbed biomolecules and liquid analytes. To date, the majority of studies using fluidic resonators have been performed at a fixed steady-state temperature close to room temperature, since temperature modulation inevitably changes the resonance frequency of the fluidic resonators, one of the key measurement variables.To maintain physiologically relevant conditions or to perform measurements at different temperatures, fluidic resonators have been heated. Initially, slow heating methods such as heating bath circulation or hot plate were used, followed by fast photothermal heating to raise the temperature of the fluidic resonators and the sample together. Of note, the major drawbacks of fast photothermal heating are the need for a complicated optical system and tedious alignment, and less precise and less quantitative temperature modulation. Integration of heating electrodes into fluidic resonators during device fabrication is considered to be the best option, although fabrication complexity and cost are expected to increase or device yield may be compromised. However, if heating electrodes are successfully integrated into fluidic resonators, new measurement modalities such as microcalorimetry and thermogravimetry would be enabled and a variety of coupled phenomena between dynamics, fluid mechanics and heat transfer could be effectively studied.Recently, we have developed heater-integrated fluidic resonators (HFRs), which allow fast, quantitative, alignment-free and wide-range temperature modulation [3]. Because the integrated heater can also act as a resistive thermometer, HFRs can track temperature and resonant frequency as they are heated by resistive thermometry and resonant densitometry. With and without a dispensing nozzle, HFRs are used for atomised spray dispensing, thermophysical property measurements and microchannel boiling studies. These are the first demonstrations of transient operation of fluidic resonators over a significantly extended temperature range. The performance of HFRs has been further enhanced by reducing mechanical and thermal losses in vacuum [4].Our current focus is on hyper-multimodal measurements with HFRs, providing primary properties (mass density, dynamic viscosity, thermal conductivity and specific heat) and secondary properties (thermal diffusivity, kinematic viscosity and Prandtl number) of various liquid samples at elevated temperatures. Once cooperatively combined with machine learning, such hyper-multimodal measurements appear to be exclusively useful for the identification and analysis of liquid mixtures. Measured spectra of mechanical and thermophysical properties of mixtures can be separated into corresponding spectra of individual components. We envisage that these will become the basis of mechanical and thermophysical spectroscopy, enabling separation-free analysis of liquid mixtures.

Laser micro/nano structuring of three-dimensional porous gradient graphene: Advanced heater for antibacterial surfaces and ion-selective electrode for sweat sensing

The development of three-dimensional (3D) gradient porous graphene (GPG) patterns, leveraging the remarkable properties and unique structure of graphene, has garnered considerable attention owing to their excellent electrochemical and electrothermal performances. Among the numerous graphene synthesis methods, laser-induced graphene (LIG) stands out as an eco-friendly and practical approach for creating patterned graphene structures on commercial films, with synthetic details varying depending on the application. Unlike conventional LIG with uniform geometric characteristics, we developed an innovative approach for circular line-scribed ultraviolet (UV)-LIG patterning; these approaches utilize a high overlapping factor and low power to achieve uneven graphitization. A comprehensive analysis of the 3D GPG was conducted via specific surface area measurements, contact angle analyses, sheet resistance measurements, X-ray photoelectron spectroscopy, and Raman spectroscopy. These 3D GPG structures exhibit large surface areas, low sheet resistance, and superior ion transport, thus improving heater and ion-selective electrode (ISE) performances. The fabricated 3D GPG heaters were successfully applied to antibacterial surfaces, and the ISEs were applied in a sweat sensor was demonstrated owing to the remarkable combination of high surface area, low electrical resistance, and unique 3D porous structure.

Thermal Performance of a Cylindrical Li[Ni0.6Co0.2Mn0.2]O2/Graphite Battery based on the Electrochemical-Thermal Coupling Model

The thermal safety of lithium-ion batteries has garnered significant attention due to its pivotal role in the field of new energy. In this work, a three-dimensional electrochemical-thermal coupling model based on the P2D model was established for predicting the thermal performance. The charge-discharge and temperature rise experiments via 18650 cylindrical Li[Ni0.6Co0.2Mn0.2]O2 / graphite batteries are designed to confirm the rationality of the model. The simulation results show that the highest temperature of the battery surface during discharging at 1 C and 4 C are 42.85 °C and 61.25 °C, and the experimental results are 42.50 °C and 62.85 °C, respectively. The electrode heat generation mainly comes from the reaction heat of cathode and anode during 1 C charge process, the maximum power is 1.2 W and 0.6 W, respectively. In the discharge process, the cathode dominates the reaction contribution of 1.02 W and the reaction heat power from the anode is only 0.016 W. The capacity of heat dissipation can be increased by enhancing the convective heat transfer coefficient and air velocity within a reasonable range. The proposed electrochemical-thermal coupling model is valuable to evaluate the heat behavior and promote the battery development.

Synthetic nanoarchitectonics with ultrafast Joule heating of graphene-based electrodes for high energy density supercapacitor application

This study presents a novel approach for the development of high-performance supercapacitor (SC) electrodes using the Flash Joule Heating (FJH) method. Here, we report a direct and rapid synthesis of graphene-based electrodes via FJH. The technique involves microwave-assisted decomposition of citric acid and urea to form CNDs as precursors, followed by Flash Joule Heating (FJH) leading to the formation of graphene in seconds. The scalability of this method paves the way for the rapid production of graphene-based SC electrodes. Based on the characterisation using XRD, Raman, SEM and TEM, the FJH-treated CNDs yielded graphene on carbon fibre cloth with well-defined morphologies leading to superior electrochemical performance in supercapacitors. The FJH processed electrodes exhibited exceptional electrochemical performance with a specific capacitance of 279 F g⁻¹ at 1 A g⁻¹, significantly outperforming unflashed and low current flash processed electrodes. This exceptional performance can be attributed to the formation of high-quality, few-layered graphene with enhanced electrical conductivity and efficient ion transport properties. Moreover, a Symmetric supercapacitor is also assembled which demonstrated a specific capacitance of 106.5 F g⁻¹ at 1 A g⁻¹. It also exhibited an impressive energy density of 44.4 W h kg−1 at a power density of 1000 W kg⁻¹. This work demonstrates the feasibility of FJH as a rapid, scalable and cost-effective technique for the production of high-performance graphene-based electrodes for supercapacitor applications.

PERILAKU DISTORSI, KEKERASAN DAN KOROSI HASIL HARDFACING PADA PERMUKAAN BAJA KARBON MENGGUNAKAN ELEKTRODA HV-800 DENGAN BERBAGAI KETEBALAN

This research aims to look at the hardness and corrosion of the weld layer. In addition, distortions were also observed in the post-welding specimens. Weld layers were made with variations of one, two and three layers of welding using HV-800 electrodes. The first step in this research is a literature study, followed by preparing tools and materials, heating electrodes, welding process, observing distortion, cutting specimens for testing followed by hardness and corrosion testing, and data analysis and conclusions. From the results of observing the distortion, it can be seen that the thicker the weld layer, the greater the distortion that will occur. Distortions in specimens welded with one, two and three layers are 1.5, 4 and 6° respectively. Furthermore, based on the results of the hardness test, it can be seen that the thicker the weld layer, the greater the hardness. The hardness of the one, two and three layer welded specimens was 550.2, 632.82 and 650.68 HV respectively. Then, based on the weighing results, it can be seen that the longer the immersion time, the greater the reduction in mass during 120 hours of immersing. Finally, from the results of the corrosion rate calculation it can be seen that the thicker the weld layer, the lower the corrosion rate that will occur. The corrosion rates for specimens welded with one, two and three layers were 13.23, 11.02 and 10.29 mpy, respectively. All three specimens have good corrosion resistance because they fall into the "good" criteria.

Heat transfer performance and electrohydrodynamic characteristics optimization of a dividing-wall-type ionic wind heat exchanger

Heat exchangers play a major role in reducing emissions and conserving energy. There is a plethora of theoretical research on the enhancement of heat transfer caused by ionic wind, but there is still a lack of studies on the practical application of ionic wind in heat exchangers to increase heat exchange capacity. This work developed an original ionic wind heat exchanger with a dividing wall. It may be applied to difficult circumstances when conventional heat exchangers fail for air-to-air heat exchange. The study conducted experiments to investigate the impact of many factors, including intake air velocity, discharge spacing, and electrode distribution scheme, on the ionic wind intensity and the heat exchanger's increased heat transfer coefficient. A two-dimensional model was used to analyze the internal flow and thermal properties of the heat exchangers with wire emitters. By combining active and passive heat exchange technologies, an ionic wind heat exchanger with serrated grounded electrodes was presented. The outcomes demonstrated that a suitable intake air velocity enhances the heat exchanger's capacity for heat exchange. The improved heat exchange effect of ionic wind is more important when the inlet wind speed is less than 1 m/s. When the intake air velocity approaches 1.3 m/s, the ionic wind has less of an impact on the heat exchanger's capacity for heat exchange. The benefits of improved heat transfer are promoted by placing the emitter closer to the channel entry. Increasing the operating voltage further enhances the heat transfer enhancement ratio (HTER). The number and arrangement of wire electrodes should be chosen with consideration for the 'barrier effect' between neighboring emitters and the distance from the entrance when utilizing multiple wire electrodes. In comparison to the three-wire and five-wire electrodes, the four-wire electrode heat exchanger's HTER values were increased by 5.9 % and 14.3 %, respectively. The ionic wind heat exchanger's capacity for heat transfer is further increased using a zigzag grounding electrode. The zigzag uses a decreased aspect ratio, and the emitter is positioned slightly above the tip, improving the system's heat transfer capabilities. When compared to a heat exchanger with a flat plate grounded electrode, the four-wire electrode heat exchanger produced a 158 % increase in HTER value.

Large-scale optical switches by thermo-optic waveguide lens

Optical switches are desired in telecom and datacom as an upgrade to electrical ones for lower power consumption and expenses while improving bandwidth and network transparency. Compact, integrated optical switches are attractive thanks to their scalability, readiness for mass production, and robustness against mechanical disturbances. The basic unit relies mostly on a microring resonator or a Mach–Zehnder interferometer for binary “bar” and “cross” switching. Such single-mode structures are often wavelength / polarization dependent, sensitive to phase errors and loss-prone. Furthermore, when they are cascaded to a network, the number of control units grows quickly with the port count, causing high complexity in electronic wiring and drive circuit integration. Herein, we propose a new switching method by thermo-optic waveguide lens. Essentially, this multimode waveguide forms a square law medium by a pair of heater electrodes and focuses light within a chip by robust 1 × 1 imaging. A 1 × 24 basic switch is demonstrated with 32 electrodes and only two are biased at a time for a chosen output. By two-level cascading, the switch expands to 576 ports and only four electrodes are needed for one path. The chips are fabricated on wafer scale in a low-budget laboratory without resorting to foundries. Yet, the performance goes beyond state of the art for low insertion loss, low wavelength dependence and low polarization dependence. This work provides an original, alternative, and practical route to construct large-scale optical switches, enabling broad applications in telecom, datacom and photonic computing.

Deformable Joule heating electrode based on hybrid layers of silver nanowires and carbon nanotubes and its application in a refreshable multi-cell Braille display.

Stretchable electrodes are an essential component in soft actuator systems. In particular, Joule heating electrodes (JHEs) are required for thermal actuation systems. A highly stretchable, patternable, and low-voltage operating JHE based on hybrid layers of silver nanowires (AgNWs) and carbon nanotubes (CNTs) is reported. The conductive layers were applied on a locally pre-strained bistable electroactive polymer (BSEP) membrane to form a wrinkled conductive surface with a low resistance of 300 Ω/sq, and subsequently patterned to a serpentine trace by laser engraving. The resistance of the resulting electrode remains nearly unchanged up to ~80-90% area strain. By applying a voltage of 7 - 9 V to the electrode, the temperature of the BSEP membrane increased to more than 60 °C, well above the polymer's phase transition temperature of 46 °C, thereby lowering its modulus by a factor of 103. An electronic Braille device based on the JHEs on a BSEP membrane was assembled with a diaphragm chamber. The electrode was patterned into 3 × 2 individually addressable pixels according to the standard U.S. Braille cell format. Through Joule heating of the pixels and local expansion of the BSEP membrane using a small pneumatic pressure, the pixels deformed out of the plane by over 0.5 mm to display specific Braille letters. The Braille content can be refreshed for 20,000 cycles at the same operating voltage.

Electrode Surface Heating with Organic Films Improves CO2 Reduction Kinetics on Copper.

Management of the electrode surface temperature is an understudied aspect of (photo)electrode reactor design for complex reactions, such as CO2 reduction. In this work, we study the impact of local electrode heating on electrochemical reduction of CO2 reduction. Using the ferri/ferrocyanide open circuit voltage as a reporter of the effective reaction temperature, we reveal how the interplay of surface heating and convective cooling presents an opportunity for cooptimizing mass transport and thermal assistance of electrochemical reactions, where we focus on reduction of CO2 to carbon-coupled (C2+) products. The introduction of an organic coating on the electrode surface facilitates well-behaved electrode kinetics with near-ambient bulk electrolyte temperature. This approach helps to probe the fundamentals of thermal effects in electrochemical reactions, as demonstrated through Bayesian inference of Tafel kinetic parameters from a suite of high throughput experiments, which reveal a decrease in overpotential for C2+ products by 0.1 V on polycrystalline copper via 60 °C surface heating.

Relationship between viscosity, foaming, and structure of CaO–SiO2–Al2O3–MgO–FeO slag with the addition of SiO2 and Al2O3

Optimizing the foaming characteristics of slag in electric arc furnaces (EAF) presents a challenging task, affecting electrode heating efficiency and increasing smelting cost. This study explores the impact of adding silicon dioxide (15–35 wt%) and a small quantity of alumina (5–10 wt%) on the viscosity and foaming properties of CaO–SiO2–Al2O3–MgO–FeO slag. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to investigate structural changes in the slag melt. The findings reveal that higher levels of silica or a slight increase in alumina content enhance slag polymerization and foaming efficiency. Specifically, a 10 wt% alumina content, in contrast to 5 wt%, leads to high silica content, leading to faster polymerization but relatively lower viscosity. Structural analysis confirms that increasing alumina content, particularly when silica content is high, results in a less stable Al–O–Si structure, causing a shift from Q0 and Q1 units to Q2 and Q3 units, which ultimately reduces viscosity. When the alumina content remains at 5 wt% and silica content increases from 15 wt% to 35 wt%, foaming efficiency improves from 13.06 cm min to 94.97 cm min, a remarkable 627% rise. Moreover, when silica content is 30 wt% and alumina is slightly increased by 5 wt%, there is a notable enhancement in foaming efficiency, rising from 47.11 cm min to 89.16 cm min, while the effect on viscosity is not prominent.

3D Multimodal Sensing and Feedback Finger Case for Immersive Dual‐Way Interaction

AbstractWith the rapid development of virtual reality (VR) technology, artificial intelligence , and the Internet of Things , a new era of immersive interaction with the digital world has emerged. In this context, a novel soft finger case with 3D multi‐modal sensing and feedback functions (3D‐SFC) is presented. The device leverages multiple material properties to create a modulated fingertip haptic feedback for the perception of orientation and force, triboelectric nanogenerator (TENG) sensing with dynamic and static responses and control of movement, and thermal feedback based on resistive heating of TENG electrodes. The integrated TENG tactile sensing unit in the device is capable of recognizing the texture of an object's surface, providing users with a more natural and intuitive way of interacting with digital objects. The spatial consistency of multi‐modal sensing and feedback enhances human‐machine interaction in various fields such as healthcare, manufacturing and assembly, and gaming, etc. The proposed device represents a new intelligent sensing solution for achieving cross‐space sensory interaction, opening up new possibilities for the future of VR and digital interaction.

Reliability of FET-type gas sensor with asymmetric air-gap micro-heater structure considering thermoelectric effect

Poly-silicon has a wide range of applications because of its interesting properties in the thermoelectric effect. We propose an optimal field-effect transistor-type (FET-type) gas sensor platform with an embedded poly-silicon micro-heater designed considering both power consumption and reliability. Since the poly-silicon micro-heater has a thermoelectric effect, the reliability of the micro-heater can be improved without a significant increase in power consumption by adopting asymmetric etch-holes (finally asymmetric air-gap) along the heater electrode. The sensor with the shorter etch-hole (10 µm) around one electrode of the heater electrode increases power consumption by only 1.22 times but can increase lifetime by 14.2 times. The heat distribution and contact temperature of symmetric and asymmetric air-gap heaters are compared using COMSOL Multiphysics. Sensors with different lengths of etch-holes are fabricated, and the thermal response and reliability of the fabricated sensors are measured and analyzed. In addition, in a sensor in which a thin film of indium oxide is deposited as a sensing material on the gas sensor platform, the effect of air-gap design change on the gas sensing characteristics is investigated. Depending on the polarity of the voltage applied between the two terminals of the heater, the difference in void formation and damage at the heater contacts is confirmed by TEM and EDS analysis.

Comparison of Weldability and Microstructure in Resistance Spot Welding of Aluminum 5052-H32 Alloy and Al 6014-T4 Alloy

This study was performed to compare the resistance spot weldability of Al 5052-H32 alloy and Al 6014-T4 alloy, and the cause of the differences in the weldability was investigated. In general, the surface of the aluminum alloy has an oxide film several nm thick, and local heat input is generated at the electrode-sheet interface and the sheet-sheet interface during resistance spot welding. XPS analysis proved that the Al 5052- H32 alloy has a relatively thick magnesium oxide film on the surface and contains a large amount of magnesium solute element. As a result, Al 5052-H32 has a higher resistance, in both the contact resistance of the electrodesheet interface and sheet-sheet interface, compared with the Al 6014-T4 alloy. Therefore, the Al 5052-H32 alloy has a larger nugget diameter at the same welding current as compared to the Al 6014-T4 alloy, but the surface contamination of the electrode is aggravated due to local heat input. The results indicated that a difference in oxide film type and thickness can significantly influence resistance heat generation and electrode cooling effects, as well as produce welds with different weld morphology and microstructure. In addition, the Al 5052-H32 alloy had more pores and shrinkage in the weld than Al 6014-T4 alloy, and longitudinal cracks were observed in the center of the nugget, but had relatively excellent mechanical properties.

Электрический озонатор-излучатель воздуха для сельскохозяйственных помещений:результаты исследований автономного модуля

The air environment of livestock buildings requires disinfection and improvement of the gas composition. The most effective method is ozonation. In order to improve the air inside livestock buildings, the authors have developed an electric ozonizer-emitter. Its emitter module consists of two ceramic bases with different-potential tungsten electrodes, one base having an electrode in the form of a honeycomb cell, and the other - in the form of a rod. The ozone productivity is regulated by changing the discharge gap between the emitter electrodes and the conducting plane. It has been theoretically established that ozone formation in a corona discharge depends on the electric field strength between the different-potential electrodes and their heating temperature. In this case, the maximum strength is achieved with a discharge gap from 25 to 35 mm and electrodes with a radius of no more than 2 mm. The effect of electrode heating temperature on ozone formation was studied on the developed design of the ozonizer-emitter in a laboratory of 180 m3 at an air temperature of 25°C above zero. The air gap between the electrodes was 30 mm, the voltage on the emitter varied from 10 to 30 kV, the duration of the ozonizer-emitter operation ranged between 0 and 80 min, the airflow rate induced by the electric fan was 0.3 m/s. It was experimentally established that stable operation of the ozonizer-emitter is observed when the electrode temperature does not exceed 30°C. In the future, the authors plan to introduce the ozonizer-air emitter into the ventilation and air conditioning system of agricultural buildings.

Structure and properties of modified shungite concrete during electrode heating

Concrete composition modifying by different electrically conductive components is one of less laborious but relatively effective methods between wide variety of electrode concrete heating effectiveness improvement methods. The purpose of this study is investigation of special aspects of cement systems modified by powdered shungite (Ssp 400 m2/kg) in combination with active mineral and plasticizing admixtures that harden under electrode heating at below zero temperatures. By the method of differential thermal analysis anomaly of exothermic reaction of cement stone specimens was discovered, that is due to formation of hydrated calcium silicate С2SH (A) discovered by the method of quantitative XRDA, and is verified by results received from scanning electron microscopy method, which among other factors provides higher strength and low permeability to these composites. Stability of cement systems modified by shungite and curing under electrode heating has been proved.

Optimization and comprehensive comparison of thermo-optic phase shifter with folded waveguide on SiN and SOI platforms

The thermo-optic phase shifter (TOPS) using metal heaters is widely used in various integrated photonics devices for its advantages of simple fabrication, low loss, and low cost. While folded waveguides are commonly employed to enhance the performance of these phase shifters, a comprehensive understanding of how varying the number of folds and the dimensions of heaters impact the device's performance is still lacking. In this paper, we conducted a comprehensive comparison and optimization into the impact of the number of folded waveguides and the width of heater on the performance of folded waveguide thermo-optic phase shifter (FW-TOPS) on silicon nitride (SiN) and silicon-on-insulator (SOI) platforms using the finite element method (FEM). The research has revealed that both the number of waveguides and the width of the heater exert a substantial influence on the performance of FW-TOPS, particularly on platforms with low refractive index contrast. In cases where the number of waveguides is the same, and the width of the heater electrode is identical, the comparison indicates that on the SiN platform, the FW-TOPS in waveguide Combination 2 (waveguide 1 is a single-mode waveguide, while waveguide 2 is a multi-mode waveguide) exhibits superior overall performance, compared to waveguide Combination 1 (both waveguide 1 and waveguide 2 are single-mode waveguides). However, on the SOI platform, FW-TOPS with waveguide Combination 1 demonstrates better overall performance compared to waveguide Combination 2. Furthermore, the simulation results indicate that although air trenches can significantly reduce the power consumption of the FW-TOPS, they also lead to a substantial decrease in the response speed. Therefore, on the 300 nm-thick SiN and 220 nm-thick SOI platforms, air trenches do not effectively enhance the overall performance of the FW-TOPS.

Impact of Power Electronic Converter Ripples on Vanadium Redox Flow Batteries

The worldwide effort to decarbonize the electricity grid has made battery energy storage system (BESS) an essential technology. A promising technology for long duration storage on the grid is Vanadium Redox Flow Batteries (VRFBs), which can support the grid by regulating peak load, reducing intermittency of large-scale renewables, and as emergency power supply. There are two primary methods of integrating a BESS to the grid. Frist, the BESS is directly connected to the DC-link of a DC-AC converter that interfaces with the grid. Second, the BESS is connected to a DC-DC converter that in turn interfaces with the DC-link of a DC-AC converter. These converters all have a characteristic ripple voltage and current during operation. The magnitude and frequency of the ripples depend on topology and switching frequency of a converter, controller design and protocol, type of connection to the grid, voltage magnitude and load characteristics. Currently, studies on the impact of ripples have been limited to Lithium-ion and Lead-Acid batteries. The impact of ripple current and voltage has not been studied in VRFBs. In a VRFB, potential impact includes excessive gassing of hydrogen and carbon corrosion of the bipolar plate and porous electrode and cell heating. To better integrate and operate VRFBs to the electricity grid, the impact of ripples needs to be studied in detail.Using a novel experimental platform, where both magnitude and frequency of ripples will be incorporated, we will emulate the performance of different power electronic converter configurations. It will comprise standard 5cm2 VRFB cells with a carbon felt electrode and Nafion ion exchange membrane. The various converter ripples in an electricity grid setting will be emulated by superimposing the signals from a potentiostat (constant current) and a high frequency transformer (modulated ripples), which will be connected to the cathode of the cells.The experimental testbed will be used to cycle the VRFB cells at various states of charge with ripples that emulate the performance of power electronic converters during grid operations and disturbances. Varied parameters will include ripple amplitude, ripple frequency, electrolyte flow rate, applied current density and state of charge. Measurement data from monitoring voltage of each electrode, cell voltage and current, gas generation, electrolyte crossover and electrolyte loss will be analyzed to determine the impact of ripples on VRFB cells. Finally, the cells will be monitored for signs of gas generation and postmortem signs of carbon corrosion.Our analysis will determine the impact of various ripple magnitude and frequencies on VRFBs in a simulated grid integration environment. This work will facilitate the development of design standards for power electronic converters that are intended for battery applications, while also informing future efforts to optimize VRFB cell and stack performance.

Analyzing Temperature Distribution, Mass Transport, and Cell Performance in PEM Fuel Cells with Emphasis on GDL Face Permeability and Thermal Contact Resistance Parameters.

Temperature distribution, mass transport, and current density are crucial parameters to characterize the durability and output performance of proton exchange membrane fuel cell (PEMFC), which are affected by thermal contact resistance (TCR) and gas diffusion layer (GDL) face permeability within both cathode and anode GDL porous jumps. This study examined the effects of TCR and GDL face permeability on a single PEM fuel cell's temperature profiles, mass transport, and cell performance using a three-dimensional, nonisothermal computational model with an isotropic gas diffusion layer (GDL). This model calculates the ideal thermal contact resistance by comparing the expected plate-cathode electrode temperature difference to the numerical and experimental literature. The combined artificial neural network-genetic algorithm (ANN-GA) method is also applied to identify the optimum powers and their operating conditions in six cases. Theoretical findings demonstrate that TCR and suitable GDL face permeability must be considered to optimize the temperature distribution and cell efficiency. TCR and GDL face permeability lead to a 1.5 °C rise in maximum cell temperature at 0.4 V, with a "Λ" shape in temperature profiles. The TCR and GDL face permeability also significantly impacts electrode heat and mass transfer. Case 6 had 1.91, 6.58, and 8.72% higher velocity magnitudes, oxygen mass fractions, and cell performances than case 1, respectively. Besides, the combined ANN-GA method is suitable for predicting fuel cell performance and identifying operation parameters for optimum powers. Therefore, the findings can improve PEM fuel cell performance and give a reference for LT-PEMFC design.