Discharge Operation Research Articles

Machine‐Learning‐Based Accurate Prediction of Vanadium Redox Flow Battery Temperature Rise Under Different Charge–Discharge Conditions

ABSTRACTAccurate prediction of battery temperature rise is very essential for designing efficient thermal management scheme. In this paper, machine learning (ML)‐based prediction of vanadium redox flow battery (VRFB) thermal behavior during charge–discharge operation has been demonstrated for the first time. Considering different currents with a specified electrolyte flow rate, the temperature of a kW scale VRFB system is studied through experiments. Three different ML algorithms; linear regression (LR), support vector regression (SVR), and extreme gradient boost (XGBoost) have been used for prediction. The training and validation of ML algorithms have been done by the practical dataset of a 1 kW 6 kWh VRFB storage under 40 , 45, 50, and 60 A charge–discharge currents and 10 L min−1 of flow rate. A comparative analysis among ML algorithms is done by performance metrics such as correlation coefficient (R2), mean absolute error (MAE), and root mean square error (RMSE). XGBoost shows the highest R2 value of around 0.99, which indicates its higher prediction accuracy compared to other ML algorithms used. The ML‐based prediction results obtained in this work can be very useful for controlling the VRFB temperature rise during operation and act as an indicator toward further development of an optimized thermal management system.

On the in-situ determination of the effective secondary electron emission coefficient in low pressure capacitively coupled radio frequency discharges based on the electrical asymmetry effect

Abstract We present a method for the in-situ determination of the effective secondary electron emission coefficient (SEEC, γ) in a capacitively coupled plasma (CCP) source based on the γ-dependence of the DC self-bias voltage that develops over the plasma due to the Electrical Asymmetry Effect (EAE). The EAE is established via the simultaneous application of two consecutive radio-frequency harmonics (with a varied phase angle) for the excitation of the discharge. Following the measurement of the DC self-bias voltage experimentally, Particle-in-Cell/Monte Carlo Collision (PIC/MCC) simulations coupled with a diffusion-reaction-radiation (DRR) code to compute the argon atomic excited level dynamics are conducted with a sequence of SEEC values. The actual γ for the given discharge operating conditions is found by searching for the best match between the experimental and computed values of the DC self-bias voltage. The γ ≈ 0.07 values obtained this way are in agreement with typical literature data for the working gas of argon and the electrode material of stainless steel in the CCP source. The method can be applied for a wider range of conditions, as well as for different electrode materials and gases to reveal the effective SEEC for various physical settings and discharge operating conditions.

Reproducibility of operating potentials for a C12A7 electride plasma-based cathode with constant keeper current control

Hollow Cathodes are fundamental components for electric propulsion systems. In recent publications, the performance of a planar C12A7 electride cathode has been presented with promising results. This includes the endurance operation of the cathode, the heaterless ignition cycling, and the general performance mapping over a wide range of parameters. The present publication will add to these publications, presenting results of only one defined set of discharge parameters, allowing a statistical evaluation of repeated discharge operations. Overall, exceptable repeatability of the performance could be evaluated, confirming the overall performance trends observed in previous campaigns. The cathode was operated in self-heating mode using krypton as propellant in a current range of 100 mA to 600 mA. A discharge potential of 30 V with a slight increase for lower discharge currents is reported. Furthermore, means to reduce the variation in the test results by increasing the keeper current have been identified.

Iron-based bimetallic oxide carbon composites with superior lithium storage capabilities serve as anode in lithium-ion batteries

Transition metal oxides (TMOs) have emerged as highly promising electrode materials for lithium-ion batteries (LIBs) owing to their versatile valence states and distinctive morphological attributes. Bimetallic oxides, in particular, exhibit the ability to mitigate the volume expansion associated with lithium alloying and de-alloying processes. Despite these advantages, metal oxides often suffer from drawbacks such as poor conductivity, limited cycle stability, and a propensity for lithiation. Addressing the challenges of low electronic conductivity, significant volume expansion, and inadequate uniformity, we synthesized two bimetallic oxide-based carbon composites via a “one-pot” solvothermal approach: ZnFe2O4@C and MnFe2O4@C. These composites are enveloped in a carbon shell derived from anhydrous ethanol. Notably, the specific discharge capacities of ZnFe2O4@C and MnFe2O4@C surpass those of their respective single metal oxide counterparts. Following nearly 300 cycles of charge and discharge operations at a current density of 100 mA g−1, ZnFe2O4@C exhibited a specific discharge capacity of 1528 mAh g−1, while MnFe2O4@C demonstrated a capacity of 1283 mAh g−1. The synthesis method offers simplicity, high yield, and uniform morphology, making it a promising avenue for enhancing the performance of LIBs electrode materials.

A Conceptual Model for Automation of Small Ports

Abstract For large ports and terminals, the loading and discharge operations have to a great extent been automated already. However, for the vast number of small ports, for instance all Norwegian ports, this large-scale automation is not possible due to the small size of the ports compared to the cost of introducing full automation. Still, these small ports are important logistics hubs in the transport system. They facilitate the shift from congested roads to the sea by allowing the goods to arrive closer to the final destination by using smaller, possibly autonomous, vessels. However, this puts pressure on the ports to facilitate reduced laytime in the port, to increase the port efficiency and to improve interoperability towards hinterland systems and terminals. For small ports, this means that manual and automated work processes need to exist side by side, and that it will be important to get an overview of which processes to automate and which will remain manual, in addition to the handling of the hand-over between humans and automation. This paper describes a conceptual model that can be used by small ports as a starting point on their way to introduce automation of their services supporting the cargo flow through the port. The model includes a description of port functions, tasks and responsibilities and use the concept of operational envelope to define the overall capabilities of the system, including both automation and human. This will be the starting point for how to structure the description of an operation centre that monitor and control the maritime terminal operations. The starting point for this work is a use case analysis performed in some small ports in Norway, and their need to optimize the utilization of their assets. The work is done as part of the AutoPort project which is a research project funded by the Norwegian Research Council (project number 337211). The goal of this work is to describe a methodology on how to identify the interface between automation and human operators when it comes to small ports and the movement of cargo through its terminals, and by this give a description on how different levels of automation can be implemented. The methodology consists of several steps, including definition of the context (big picture of the use case, actors and their roles, and communication), the scenario (port activities and processes), and the use cases including the control tasks performed by the automated systems.

Numerical study on positive streamer in parallel-rod dielectric barrier discharge in atmospheric air

In this work, a parallel-rod dielectric barrier discharge (DBD) operating in atmospheric air is investigated through the two-dimensional plasma fluid model. The effects of applied voltage (Vp), secondary electron emission coefficient (γ), and photoionization are examined. Photoionization can significantly influence streamer dynamics by accelerating and broadening both volumetric and surface streamers and enhance the impact of the applied voltage. Without photoionization, the propagation distance of the surface streamer along the curved dielectric surface is limited to 0.1–0.2 mm under applied voltages of 8–8.5 kV. In contrast, with photoionization, this distance can extend to 0.3–0.6 mm. Achieving the same distance requires much higher voltages (10–11 kV) if without photoionization. The “double-layer” structure of the surface streamer is investigated, revealing that γ predominantly affects the surface branch with little impact on the volumetric branch. The critical charge density for streamer onset is found to be about 1018 m−3, and the volume-to-surface streamer transition is attributed to the lateral electric field provided by the space charges. This work provides insights into the regulation strategies and underlying mechanisms of streamer dynamics in parallel-rod DBDs in atmospheric air.

Empowering energy management in smart buildings: A comprehensive study on distributed energy storage systems for Sustainable consumption

The increment of photovoltaic generation in smart buildings and energy communities makes the use of energy storage systems desired to increase the self-consumption efficiency. This paper proposes and explores a model for energy storage systems management that considers local renewable generation, local demand, and retailer energy prices. The proposed model was tested at both energy community-level and the smart building level, demonstrating their capabilities of deployment. To validate the proposed model, a case study with two scenarios, including a 251 members energy community, was executed. The results demonstrate significant cost reductions for community members when adopting energy storage systems and the proposed management model. Regarding the smart building application four scenarios were tested, it is demonstrated that the demand for energy from the retailer could be set to zero during periods of time to enable its participation in demand response events. Overall, this paper contributes to the state-of-the-art by identifying and evaluating a model that manages the energy storage systems charge and discharge operation to actively reduce energy costs at the community-level (19.26%) and building level (11.75%) and to demonstrate that part of the loads can be optimized to understand if the building can be energy net-zero.

Design and implementation of tilting‐plate drainage equipment for paddy field

AbstractDrainage equipment is an important part of paddy field drainage and irrigation system, and its performance research and application are conducive to the promotion and implementation of high‐standard farmland construction. Aiming at the different water demand of rice in different growing stages, low water level control precision, large manual operation and extensive management of existing drainage machinery, a tilting‐plate drainage equipment using upper overflow mode was proposed in this paper. Based on the Geneva mechanism principle, a unique linkage mechanism is designed, which can realize water retaining operation and silt discharge operation through a single motor drive, and the relationship between the motor angle and the water retaining height is established. Through mechanical analysis and dynamic simulation of the mechanism, the motion characteristics of the water baffle, silt plate and the change of the motor torque are studied. A remote control system based on a 4G module is designed to control the drainage equipment easily through the user layer. The performance test of the prototype shows that the precision error of the optimized water retaining height control is less than 3.75%. The maximum height of water retaining operation is 180 mm, and the maximum load of silt discharge operation is 10 kg, which can meet the actual operation requirements. The design is beneficial to improve the precision and intelligence level of paddy field drainage management, and the research process can provide some help for the development and application of this kind of equipment.

WP4.5 - Changes in Social Care Post Major Emergency General Surgery Procedures

Abstract Introduction Emergency General Surgery (EGS) is a major part of the provision of healthcare and patients undergoing EGS are at elevated risk of morbidity and mortality. The aim of this study is to determine factors contributing to patients losing their independence and being discharged to residential and nursing homes having previously lived in their own residences. Methods Data from patients in the NELA database (2014-2022) was analysed, considering demographics, ASA score, admission and discharge dates, presenting pathology, operation type, and discharge destination. Comparative analyses segmented patients based on post-discharge EGS destinations. Multivariable logistic regression identified factors linked to residential/nursing home placement post-discharge. Significance was set at p<0.05. Results Data from all patients in the NELA database (n=1,611) was analysed. Nearly one in ten patients over the age of 70 never returned home. Patients requiring additional support were on average 8.6 years older (p=0.008). Over the age of 80 years, the need for extra social support increased substantially with each increasing year in age and those over the age of 85 years old were more than twice as likely to require extra support than 80-year-olds (p<0.001). Patients who died were 11.4 years older compared to those discharged without additional support (p<0.001). Conclusion A significant proportion of patients, particularly the elderly, do not return to their usual place of residence and require a higher level of care post-emergency surgery. These important social factors need to be considered before operating as they may have significant quality of life and economic implications.

A Novel Hybrid Approach for Remaining Useful Life (RUL) and Short-Term Capacity Prediction of Batteries

Lithium-ion battery management requires an accurate determination of the batteries’ remaining usable lives. A novel hybrid method used for the RUL and short-term capacity prediction of batteries is presented in this manuscript. The proposed technique is combined with a White Shark Optimizer (WSO) with the Multi-kernel Support Vector Machine (MSVM); therefore, it is called the WSO-MSVM technique. The major goal of this WSO-MSVM method is to attain effective future capacities and RUL forecast for the Lithium-Ion Battery (LIB) with reliable management of uncertainty. The hybrid technique solves the difficulty of forecasting the RUL of LIB. This proposal trains the WSO-MSVM model using the LIB data. The trained model is utilized to forecast the capacity and RUL of LIBs. In this proposed system, capacity, current, and voltage are considered in the discharge operation. The proposed technique validates good reliability and prediction accuracy with this suitable mechanism. Compared to the existing techniques like artificial neural network (ANN), ant lion optimizer-optimized artificial neural network, and adaptive network-based fuzzy inference system, the proposed technique shows fewer errors under charge and discharge conditions. In addition, the uncertainty intervals of the proposed WSO-MSVM technique for the predicted RUL may include the actual remaining life of the battery. The proposed technique’s charging error is lower the other exciting methods.

Experimental investigation on an innovative serpentine channel‐based nanofluid cooling technology for modular lithium‐ion battery thermal management

AbstractMany nations have committed to becoming carbon neutral by 2050 as a means of addressing the global warming challenge. To achieve carbon neutrality, transportation is one of the most essential and important tasks. Energy‐efficient pure electric vehicles (EVs) and hybrid electric vehicles (HEVs) with green energy power are being developed in response to the worldwide energy and environmental crises, as the potential replacements for the current generation of combustion‐engine automobiles. EVs require batteries more than ever before. In this perspective, lithium‐ion batteries (LIBs) stand out as remarkable energy storage technologies and have been widely used due to their numerous impressive benefits. Owing to LIBs sensitivity to temperature, EVs typically use the battery thermal management system (BTMS). The working temperature span of a lithium‐ion battery in an electric car is 15°C–35°C, which is achieved by the use of a BTMS. The production of internal heat during charging and discharging also affects how well lithium‐ion batteries work. A battery heat control system is therefore required. The temperature of the LIB pack might be efficiently controlled by liquid‐cooled systems in discharge and charge scenarios. Based on Al2O3 nanofluid (NF), the current experimental study suggests a novel active cooling technology for regulating the heat produced by the 18650‐format lithium‐ion batteries. A thorough analysis is conducted on the impact of charge/discharge C‐rates, Al2O3 nanoparticle (NP) volume fractions, inflow coolant velocity, and intake liquid temperature on the thermal efficiency of the LIB pack. By incorporating aluminum oxide NPs into the water at varying volume fractions of 0.3%, 0.5%, and 1%, the LIB pack's maximum temperature was significantly reduced by 7.9%, 18.09%, and 19.56%, respectively. With increase in mass flow rate of coolant from 0.0290 to 0.5810 kg/s, the maximum temperature has been substantially reduced by 3.7%–8.6%. Results show that using higher fluid inflow temperature significantly increased both the highest experienced temperature and temperature diversity throughout the discharge operation by about, 6°C and 5°C, respectively. The outcomes of the study indicate that NFs exhibit superior cooling performance compared to conventional coolants such as water and ethylene glycol.

Suitable material design of temperature-stabilizing device using phase change materials for electric power supply of nanosatellites

This study proposes a new passive thermal-control device utilizing phase-change materials (PCMs) that require minimal active thermal support, such as heaters, to achieve a high-performance and high-reliability power supply for nanosatellites and other space applications. This study evaluated two different PCMs as candidate materials for the device and compares their performances as thermal control devices. One was a solid–solid PCM based on vanadium dioxide doped with tungsten (VWO2), and the other was a microencapsulated PCM containing n-paraffin (NPH-MPCM). For integration into nanosatellites, it is essential to form a PCM as solid blocks. This report adopted a solidification method using epoxy resin (EP) as the binder and determined the optimal block composition for each PCM. The thermal-insulation properties of both PCM blocks in vacuum and low-temperature environments were evaluated and found to be almost equivalent. Considering that the latent heat of VWO2 is only approximately one-fifth that of NPH-MPCM, the practical application of VWO2 as a PCM was demonstrated. Furthermore, VWO2 exhibits a phase-change temperature hysteresis of 4 °C, which is significantly smaller than the 23 °C of NPH-MPCM. This characteristic is expected to help maintain a more constant temperature for power supplies in earth-orbiting micro/nanosatellites. Moreover, lithium-ion battery cells were incorporated into both VWO2-based and NPH-MPCM-based PCM blocks, and their charge–discharge behaviors were evaluated. Only the VWO2-based PCM block could maintain appropriate temperatures to ensure stable charge–discharge operation. Vacuum resistance results suggested that the VWO2-based PCM block is well-suited as a temperature-stabilizing device for electric power supplies in nanosatellites.

Overview of the KSTAR experiments toward fusion reactor

Abstract The KSTAR has been focused on exploring the key physics and engineering issues for future fusion reactors by demonstrating the long pulse operation of high beta steady-state discharge. Advanced scenarios are being developed with the goal for steady-state operation, and significant progress has been made in high ℓi, hybrid and high beta scenarios with βN of 3. In the new operation scenario called FIRE, fast ions play an essential role in confinement enhancement. GK simulations show a significant reduction of the thermal energy flux when the thermal ion fraction decreases and the main ion density gradient is reversed by the fast ions in FIRE mode. Optimization of 3D magnetic field techniques, including adaptive control and real-time machine learning (ML) control algorithm, enabled long-pulse operation and high-performance ELM-suppressed discharge. Symmetric multiple shattered pellet injections and real-time DECAF are being performed to mitigate and avoid the disruptions associated with high-performance, long-pulse ITER-like scenarios. Finally, the near-term research plan will be addressed with the actively cooled tungsten divertor, a major upgrade of the NBI and helicon current drive heating, and transition to a full metallic wall.

Modeling the Dynamics of Supercapacitors by Means of Riemann–Liouville Integral Definition

The application of fractional calculus to obtain dynamic models for supercapacitors represents an alternative approach to obtaining simpler and more accurate models. This paper presents a model for the supercapacitor in the time domain, based on the use of the fractional or non-integer order integral. This fractional model is compared with the conventional simple model, which is typically used in industrial applications. This fractional integral-based model provides satisfactory fits in relation to the number of parameters used in the model. Furthermore, an interpretation of the effect of the application of fractional integration is presented for constant current charging and discharging processes at constant current, using the Riemann–Liouville definition for the non-integer order integral. Supercapacitors are devices that exhibit non-linear behavior, with a distinct charging and discharging operation. There are several methods of dynamic analysis for the characterization of supercapacitors. The information extracted from these methods is essential for understanding the behavior of supercapacitors and, thus, ensuring that processes involving supercapacitors are as efficient as possible. This paper presents a dynamic analysis based on charge and discharge operations with constant currents. The conclusion is that the fractional model provides fairly accurate fits.

Voltage fault diagnosis and prognostic of lithium-ion batteries in electric scooters based on hybrid neural network and multiple thresholds

Voltage fault diagnosis and prognostics of lithium-ion batteries (LIBs) are critical in ensuring their safe and reliable operation, and timely voltage prediction can help detect the oncoming fault of LIBs effectively. To this end, this study develops an efficient voltage fault diagnosis and prognostic method for LIBs based on voltage prediction and multiple thresholds. Firstly, a hybrid neural network integrating convolutional neural network and gated recurrent unit is established to extract both temporal and spatial features from the current operation data and predict voltage. Then, a residual calculator is devised to generate the voltage residuals, and the maximum voltage residuals of the fault-free data during charge and discharge operations are leveraged to constitute the multiple thresholds of fault diagnosis and prognostics strategy. The robustness, reliability and feasibility of voltage prediction are validated under the conditions of different driving scenarios, different dynamic temperature and real-world operation data. Moreover, the validation results on the fault electric scooter reveals that the proposed method can reliably diagnose the battery over-voltage and under-voltage faults and their alarm levels. Additionally, the warning moment by this method is at least 630s earlier than the alarm time in the battery management system, highlighting its efficient prognostic functionality.

Assessment of Hysteresis Models for LiFePO4

The selection of the cathode material is an important task in the design phase of batteries for mobile applications. One material of increasing interest is LiFePO4 (LFP) due to its improved energy density, good thermal stability and durability. In contrast to other commonly used cathode materials, LFP features a clear phase separation between the lithium rich and the lithium poor phase, leading to a pronounced voltage plateau over wide ranges of state of charge (SOC). The level of this plateau also changes for charge and discharge operation, even at very low C-rates. This voltage hysteresis in combination with the wide plateau gives some ambiguity to the correlation between voltage and SOC, which is a challenge for battery management systems. Thus its correct description is crucial if a cell model is meant to serve as virtual twin supporting control function development and calibration. Beyond that, a highly dynamic battery development process requires models that run significantly faster than real-time and parametrization processes which allow for accurate validation and easy adaptation to modified electrodes. A simulation approach complying with these requirements is the electrochemical pseudo-two dimensional (P2D) model, though adaptions to the core model are needed to appropriately capture hysteresis-affected voltage plateau characteristics for phase-separating materials such as LFP.The goal of this study is to extend an existing P2D framework with two approaches capable of describing hysteresis effects and analyzing these extensions regarding result plausibility, computational cost and effort of parametrization. The first model of interest is based on the one-state hysteresis model proposed by Plett. This approach allows for fast simulation and accurate reproduction of the charge and discharge voltages at low C-rates but lacks deeper physical consideration of the phase-separating origin of the hysteresis and thus might lose accuracy to predict system responses on dynamic pulses. In this approach, the voltage hysteresis is not a simulation result, it is due to the input of two separate open circuit voltages for charge and discharge. The second model of interest applies variable solid diffusion (VSSD) featuring a reduced Fickian diffusion coefficient in the plateau region. Lower diffusion at a given C-rate leads to steeper concentration gradients between lithium rich and lithium poor phase. With this approach, effective phase boundaries within the representative particles can be obtained. In the limiting case, when the Fickian diffusion coefficient becomes zero or even negative at some lithium concentration, phase separation persists also when no current is applied. In this setting, the voltage hysteresis at low C-rates is an emergent phenomenon, it is not an input. The physical basis of the approach also allows to consider mechanical stresses and their impact on the voltage gap between charge and discharge. Concentration gradients cause a mismatch of volume demands and thus lead to local stresses, which in turn alter the chemical potential.Results emphasizing advantages and disadvantages of the two hysteresis models are presented. Charge and discharge simulations are performed for several C-rates and the voltage hysteresis is extrapolated to infinitely small currents. Furthermore, the effect of resting phases with zero current as in Galvanostatic Intermittent Titration Technique measurements is discussed. As hysteresis models are often tested only on charge/discharge cycles with constant currents over large SOC regions, the responses of the simulation models are also assessed in pulse tests and dynamic profiles giving a realistic picture of automotive applications. Here special focus is put on energetical aspects of the one-state model and on intra-particle concentration profiles for the VSSD model.

Practical Pouch Cell Supercapacitor Electrodes by Electrophoretic Deposition of Activated Carbon on Nickel Foam

AbstractThis study highlights for the first‐time the utilization of nickel foam coated with activated carbon (AC) via the electrophoretic deposition (EPD) method in the fabrication of A7 sized pouch cell supercapacitors. The scale‐up of electrodes via EPD from coin to pouch cells with mass loadings (10 mg cm−2) and thicknesses (>130 μm) that match industrial standards is also reported. Research investigations include: (a) comparison of a two dimensional (2D) aluminum foil current collector's performance with three dimensional (3D) microporous nickel foam current collectors, (b) impact of EPD of AC onto small (10 cm2) and large areas (50 cm2) of nickel foam, and (c) scaling‐up of coin to pouch cells along with a comparison against electrodes prepared via the standard doctor blade coating (or slurry casting) method. We demonstrate practical cell performance, including specific current loading (40 A g−1), hundred thousand of successive charge and discharge operation (150,000 cycles), power (27 kW kg−1) and energy densities (37.7 W h kg−1), capacitance (174 F g−1), capacitance retention (80 %) and coulombic efficiency (close to 100 %).

High-efficiency metal-free CO2 mineralization battery using organic redox catalysts

CO2 batteries offer a promising avenue for mitigating CO2 emissions and conversion, but encounter challenges such as high costs, dendrite, corrosion, flooding and slow kinetics stemming from the use of metal electrodes. CO2 mineralization is thermodynamically favorable (ΔGCO2), presenting an opportunity for processing solid waste and reducing CO2 emissions while potentially producing energy. However, the lack of direct electron transfer in the CO2 mineralization reaction hinders the direct generation of electrical energy. Here, we propose an organic CO2 mineralization battery (OCMB) without using metal, which efficiently harnesses CO2 to mineralize solid waste carbide slag, maximizing the recovery of mineralization reaction energy to generate electricity and produce carbonate products, without requiring renewable electricity charging. We employ a high-solubility, stable under strong alkaline conditions, and fast kinetics organic phenazine derivative—DSPZ as the electron and proton carrier, which facilitates the conversion of ΔpH between electrodes by interacting with alkaline wastes and CO2 into electricity. Simultaneously, the OCMB undergoes regeneration cycles through mineralization reactions. The theoretical model predicted the open circuit voltage (OCV) and discharge behavior of OCMB, offering insights for improved battery engineering. We demonstrate an impressive peak power density exceeding 227.5 W/m2 for the OCMB, with an estimated electricity production of ∼ 178.03 kWh per ton of CO2 mineralization. This research underscores the potential integration of OCMBs into CO2 energy systems, waste treatment processes, and chemical production, offering both economic and environmental benefits.

Synthetic ester-based forced flow immersion cooling technique for fast discharging lithium-ion battery packs

Rapid advancements in Li-ion battery technology are being made to meet the growing demand for efficient energy storage solutions in electric vehicles and portable electronics. However, heat generation during rapid charging and discharging remains a significant challenge, as it can lead to overheating, fire, and explosion. To address this issue, battery thermal management systems require improvements in cooling strategies. This study aims to optimize the thermal performance of Li-ion battery packs during fast discharge operation by single-phase synthetic ester oil-based forced flow immersion cooling (FFIC) technique. The study analyzes the thermal performance of the FFIC of a 4S2P LIB pack based on various flow rates, pressure drops, and pump power consumption and compares it with various conventional cooling methods and dielectric fluids. The MSMD-based NTGK battery modeling approach is used to analyze the electrical and thermal characteristics of the battery pack at 3C discharge and environmental temperature of 25 °C. The simulation findings revealed that the synthetic ester oil has a superior cooling effect than mineral oil in the 4S2P Li-ion battery pack. The experimental results showed that the synthetic ester-based FFIC Li-ion battery pack achieves an optimal pack temperature of 31.3 °C and uniform temperature distribution at the flow rate of 5 L/min and pressure drop of 228.44 Pa. Moreover, FFIC reduces temperature rise by 51 % compared with natural air convection and 35 % compared with static flow immersion cooling (SFIC) in the 4S2P lithium-ion battery pack. Also, the practical significance of the SEO-based FFIC immersion cooling technique is assessed across extreme climate zones such as −10 °C and 40 °C and determined its superior performance in Li-ion batteries. Hence, this study proved that the FFIC technique is suitable for Li-ion batteries in electric vehicle applications in terms of optimal performance, reliability, and safety during high-current discharge operations.

Optical emission characterization of an atmospheric pressure dielectric barrier discharge in nitrogen: Evolution of CN emissions during PTFE etching

AbstractThe present work investigates the etching of coated polytetrafluoroethylene (PTFE) films using an atmospheric pressure dielectric barrier discharge operating in nitrogen in a filamentary regime. For different treatment durations, the optical emission spectra were recorded over time. Most of the emissions are attributed to the N2 second positive system. The presence of CN is also observed, and its emissions rise with the exposure time of PTFE. This rise is attributed to the density of CN produced. The X‐ray photoelectron spectroscopy surface characterization suggests two etching regimes. This is linked with a change in slope in the intensity evolution of the optical emissions of the CN. At longer times, a fluorinated deposit on the electrode is observed, confirming a different nature of the etched material.