High Power Density Research Articles

Application of chaotic teaching-learning-based optimization technique for estimating unknown parameters of proton exchange membrane fuel cell model.

Proton exchange membrane fuel cells (PEMFC) possess features like high specific power density, low operating temperature, and low operating pressure and thus are most widely used. The performance of PEMFC highly depends on its output voltage which further affects its efficiency. This research paper aims to improve this output voltage by minimizing the losses through parameter estimation technique for three well-known commercial PEMFC stacks, namely, 250W, BCS 500W, and Ballard Mark V. The multiobjective function framed for optimization serves two goals. One is to extract the unknown parameters of FC, and second is to achieve the minimum sum of squared errors (SSE) that occur due to the difference between experimental voltage and estimated voltage. Chaotic teaching-learning-based optimization (CTLBO) algorithm is used for optimization process. SSE values obtained for three commercial PEMFC stacks 250W, BCS 500W, and Ballard Mark V are 7.02267, 4.00150, and 0.8100, respectively. The applicability of this technique is further checked for different operating conditions of each model. The I-P (current-power) curve and I-V (current-voltage) curve obtained using estimated data closely matched the experimental data that showed the practical relevance and efficacy of the algorithm. A comparison is done among the SSE results obtained using CTLBO to other competitive algorithms mentioned in the literature. CTLBO showed its superiority over other algorithms in estimating the unknown parameters of PEMFC stack parameters.

Unit prediction horizon [formula omitted] based model predictive control for the fuel cell based plug-in hybrid electric vehicle with rule-based energy management system

Plug-in hybrid electric vehicles (PHEVs) provide a good alternative in achieving better performance and in the reduction of harmful gas emissions. The hybrid energy storage system (HESS) and the integrated charging unit constitute the PHEV under consideration. To meet the load demands, the proposed HESS is a coupled system comprising a fuel cell, high energy density battery, and high-power density super-capacitor. On-board charging involves the utilization of a DC–DC buck converter and an uncontrolled rectifier and two buck-boost converters are utilized to facilitate a smooth transfer of energy. A rule-based supervisory controller has been implemented for different load conditions which takes into account the state of charge of energy sources and also the total power inflow of the power sources. A model predictive control (MPC) technique is implemented to ensure that PHEVs function smoothly in terms of regulation of DC bus voltage and tracking of current. Unit prediction horizon i.e. only one step ahead looking into the future is considered for the MPC to make it computationally less expensive. MPC is designed in such a way that its performance is close to our favorite linear controller which in our case is the H∞ controller. The inverse optimal control technique is used for determining the weight matrices of the cost function. The proposed controller has been simulated using MATLAB. Also, the performance comparison is made between the designed MPC and the non-linear control approach i.e. integral sliding mode control and integral backstepping-based control to show that it achieves comparable or superior performance to the non-linear controller. The real-time performance of H∞ based MPC is verified using controller hardware in the loop experimental setup.

Boosting the Performance and Durability of Fe-N-C Fuel Cell Catalysts via Integrating Mo2C Clusters.

Carbon-supported nitrogen-coordinated iron single-atom (Fe-N-C) catalysts have been regarded among the most promising platinum-group-metal-free catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Nevertheless, their limited intrinsic activity and unsatisfactory stability have hindered their practical applications. Here, it is reported that the integration of Mo2C clusters effectively enhances the ORR activity and stability of Fe-N-C catalysts. The composite catalyst of Fe single atoms and Mo2C clusters co-embedded on nitrogen-doped carbon (FeSA/Mo2C-NC) exhibits an excellent ORR activity with a half-wave potential of 0.82V in acidic media and a high peak power density of 0.5W cm-2 in an H2-air PEMFC. Moreover, improved stability is achieved with nearly no decay under H2-air conditions for 80h at 0.4V. Experiments with theoretical calculations elucidate that the etching effect of the phosphomolybdic acid precursor optimizes the pore size distribution of the composite catalyst, thereby exposing more active sites. The Mo2C clusters modulate the electronic configuration of the Fe-N4 sites, optimizing adsorption energy for ORR intermediates and strengthening the Fe-N bond to mitigate demetalation. This work provides valuable insights into the construction of single-atom/nanoaggregate hybrid catalysts for efficient energy-related applications.

Synergetic enhancement of moisture-electric generation through interfacial evaporation and active electrode

Ion migration-based moisture-electric generator holds the open-circuit voltage to power portable electronics, the Internet of Things, and wireless transmission. However, most devices still encounter challenges with the attainment of high-density power generation in continuous mode. Here, we introduce a sustainable and high-power density ion-selective bipolar moisture-electric generator that relies on Au-Al electrodes, capillary water supply, and interfacial evaporation. The device generates electricity by exploiting the salinity gradient between the capillary waterways in the photothermal and waste heat layers. This process is synergized by electrochemical reactions of the electrodes, which propel the migration of cations and anions through ion-selective bipolar hydrogels toward the intermediate waterway. It demonstrates a short-circuit current density of 52.2 A m−2 and a power density of up to 33.8 W m−2 over 0.5 cm × 0.5 cm electrodes. Connecting 13 devices in series in darkness successfully illuminates an LED lamp with a rated power of 1 W together with an operating voltage of 2.0–2.8 V. This work offers an off-grid, environmentally friendly, and affordable solution for high-density moisture power generation.

Effect of sub-micron deformations at opposing strain rates on the micromagnetic behaviour of non-oriented electrical steel

We are entering an era of re-electrification, seeking high-power density electrical machines with minimal resource use. Significant performance gains in electrical machines have been achieved through precise manufacturing processes, including the shaping/cutting of soft magnetic materials. However, most studies have evaluated magnetic performance at a macro level, focusing on components, while the fundamental mechanisms, e.g., how the micromagnetic behaviour is affected by mechanical interference, remain unclear. In this study, we examine the impact of sub-micron deformations at opposing strain rates (10−2 to 101 s−1) on the micromagnetic behaviour of soft magnetic non-oriented electrical steel. Using a diamond probe to indent within a single grain of polycrystalline material at different velocities, we induce quasi-static and dynamic mechanical loading. Our analysis, employing magnetic force microscopy, transmission Kikuchi diffraction, and scanning transmission electron microscopy with a pixelated detector, reveals that magnetic texture disturbances rely on the time-dependent dislocation dynamics of the Fe-BCC material. Additionally, we compress micro-pillars to further investigate these effects under bulk-isolated deformation. These findings highlight the importance of considering even ultra-small loads, such as nano-indentations and micro-pillar compressions, in the manufacturing of next-generation electric machines, as they can affect magnetic texture and performance.

Enhanced energy storage performance in NBT-based MLCCs via cooperative optimization of polarization and grain alignment

Dielectric ceramics possess a unique competitive advantage in electronic systems due to their high-power density and excellent reliability. Na1/2Bi1/2TiO3-based ceramics, one type of extensively studied energy storage dielectric, however, often experience A-site element volatilization and Ti4+ reduction during high-temperature sintering. These issues may result in increased energy loss, reduced polarization and low dielectric breakdown electric field, ultimately making it challenging to achieve both high energy storage density and efficiency. To address these issues, we introduce a synergistic optimization strategy that combine polarization engineering and grain alignment engineering. First principles calculations and experimental analyses show that the doping of Mn2+ can suppress the reduction of Ti4+ in Na1/2Bi1/2TiO3-based ceramics and enhance ion off-centering displacements, thereby reducing energy loss and improving polarization. In addition, we prepared multilayer ceramic capacitors with grains oriented along the <111> direction using the template grain growth method. This approach effectively reduces electric-field-induced strain by 37% and markedly enhances breakdown electric field by 42% when compared with nontextured counterpart. As a result of this comprehensive strategy, <111 >-textured Na1/2Bi1/2TiO3-based multilayer ceramic capacitors achieve an ultra-high energy density of 15.7 J·cm−3 and an excellent efficiency beyond 95% at 850 kV·cm−1, exhibiting a superior overall energy storage performance.

Electromagnetic performance analysis of a novel radial compound differential field-modulated magnetic gears

Purpose The purpose of this study is to propose a new magnetic gearing device and the proposed transmission model can be applied in the field of wind power and wave energy generation gearboxes. Design/methodology/approach A novel radial differential field-modulated two-stage magnetic gear is introduced, using a unique radial differential linkage to integrate two single-stage magnetic gears. This design incorporates a magnetic isolation ring to enhance transmission efficiency by minimizing magnetic interference and preventing power circulation. The two-stage modulating ring rotor operates synchronously via a connecting bridge, ensuring system stability and efficiency. This configuration not only boosts the gear ratio but also maintains a compact structure, improving power density and efficiency. Leveraging the magnetic field modulation and differential transmission, a finite element model of this gear is developed and its electromagnetic performance is analyzed. Findings The torque density of the new radial differential field-modulated two-stage magnetic gear has increased by 44.97% compared to the traditional tandem two-stage magnetic gear. It achieves a high transmission ratio of 64 and maintains comparable power density, indicating strong torque transfer capabilities suitable for low-speed, high-torque applications. During steady-state operation, the torque pulsation difference between the two stages is minimal, ensuring stable working torque. Social implications This research not only propels the forefront of magnetic gear technology through heightened efficiency and streamlined design but also bears profound societal significance in fostering sustainable energy paradigms. By facilitating superior energy conversion efficiencies in wind turbines and wave energy converters, it plays a pivotal role in mitigating carbon emissions and accelerating the global pivot towards cleaner, renewable energy landscapes. Originality/value A magnetic gear transmission device is proposed, which can achieve high power density and large transmission ratio at the same time, and this study provides a useful reference for the design optimization of new high-performance multistage magnetic gears.

Design and Performance Analysis of Windings Considering High Frequency Loss and Connection Mode of a Starter Generator

The starter generator is the key component of the aircraft’s starter generation system. A high power density, efficiency, and reliability are essential for an aircraft’s starter generator. The configuration of the windings is closely related to the performance of the starter generator. In this paper, the winding performance analysis and design are studied. Considering the skin effect, circulation effect, and proximity effect, a calculation model of winding loss under high-frequency operation is established. The motor performance under different winding connections is compared. Through a comprehensive comparison of starting performance, generation loss, and process performance differences, the optimum configuration of windings is identified. The performance of the starter generator including winding resistance, current, and no-load loss was tested on the prototype platform to verify the rationality and correctness of the analysis and design methods.

A Decoupled Modulation Strategy for Constant Voltage/Current Wireless Charging System Under High Coils Misalignment

ABSTRACTOutput fluctuation and lower transmission efficiency under load and mutual inductance variation are hot concerned in the wireless charging system for power batteries. In this paper, a decoupled tracking strategy is proposed to realize constant voltage (CV) or current (CC) output and high transmission efficiency. The circuit model of series–series compensation network is built, and corresponding transmission characteristics can be derived. First, the load and mutual inductance value can be estimated by measuring the primary electrical information, including the inverter output voltage, current, and the phase error between them. Then load‐independent voltage or current output characteristics under coils misalignment can be maintained by tracking the optimal switching frequency of inverter part. In addition, the value of output voltage or current can be adjusted flexibly for different operation occasions by the employment of pulse‐width modulation. As a result, the load‐independent output characteristics realization and output adjustment can be decoupled. Based on only the primary measuring information, the CV/CC output can be maintained via the proposed hybrid control strategy when the coils misalignment and load variation happen, increasing the robustness of whole wireless power transfer (WPT) system. Furthermore, the soft switching of all power switches in the inverter part can be realized to reduce the switching loss. Compared with previous research, the proposed wireless charging system has a higher power density and a simplified control strategy. Finally, an experimental platform with 60‐V charging voltage and 3.6‐A charging current is built to verify the feasibility of the proposed sys‐tem and control method.

Two-Stage Multiple-Vector Model Predictive Control for Multiple-Phase Electric-Drive-Reconstructed Power Management for Solar-Powered Vehicles

Electric-drive-reconstructed onboard chargers (EDROCs), also known as electric-drive-reconstructed power management systems, are a promising alternative to conventional onboard chargers due to their characteristics of low cost and high power density. The model predictive control offers a fast dynamic response, simple implementation, and the ability to control multiple targets simultaneously. In this paper, a two-stage multi-vector model predictive current control (MPCC) of a six-phase EDROC for solar-powered electric vehicles (EVs) is proposed. Firstly, the topology for the EDROC incorporating a six-phase symmetrical permanent magnet synchronous machine (PMSM) is introduced, and the operation principles of the DC charge mode, the drive mode, and, especially, the in-motion charge mode are analyzed in detail. After that, a two-stage multi-vector MPCC method is proposed by using the multi-vector MPC technique and designing a two-stage MPC structure to eliminate the regulation of the weighting factor of the MPC. Finally, the effectiveness of the proposed method is verified on a self-designed 2 kW EDROC platform.

Adaptive Frequency-Based Power Management for Off-Grid Hybrid Photovoltaic Converters

The intermittency in photovoltaic systems (PV) can lead to power quality issues, especially in off-grid applications. In these cases, adding an energy storage element helps to cope with the intermittency to provide adequate power to the local load. In this scenario, combining Li-Ion batteries and supercapacitors as a hybrid energy storage system (HESS) is powerful due to the battery's high energy density and the supercapacitor's high power density. The HESS demands adequate power management to operate adequately. This paper proposes an adaptive frequency-based power management for a Li-Ion battery and supercapacitor HESS applied to an off-grid PV converter. The main idea of this strategy is to guarantee a smoother current in the battery and reduce the power dissipation in the HESS. The smoother battery current transition helps avoid excessive battery stress and improves lifespan. The proposed strategy is compared with two other strategies. The results show that the proposed approach is more efficient in reducing the HESS' power dissipation and providing smooth current variations to the battery.

Wedge-loading planetary traction drive: Modeling and performance analysis

The continuous development of motors with high speed and high power density has significantly increased the demand for high-speed reducers. Traction drive has emerged as a new option for high-speed reducers due to its high transmission efficiency and accuracy in high-speed transmission. In the previous theoretical studies on traction drive, the traction coefficient was set as a fixed value, and the influence of elastohydrodynamic lubrication (EHL) on the traction coefficient was ignored. Therefore, this paper investigated the wedge-loading planetary traction drive (WL-PTD) and established a theoretical model combining the macroscopic and microscopic traction mechanisms of the traction drive based on Hertzian contact and mixed elastohydrodynamic lubrication (mixed EHL). The loading principle and transmission performance of WL-PTD were studied through numerical computations, and the effects of different design parameters on transmission performance were discussed. When the input speed of WL-PTD was 10,000 rpm, the peak value of the global sliding coefficient was approximately 1.27×10−5, and the maximum transmission efficiency reached 97.41%, indicating an excellent transmission performance of the WL-PTD. The findings of this study can provide theoretical guidance for subsequent optimization design.

Flexible Micro‐supercapacitors with Enhanced Energy Density Utilizing Flash Lamp Annealed Graphene‐Carbon Nanotube Composite Electrodes

As demand for micro‐power sources grows, micro‐supercapacitors (MSCs) have become critical for miniaturized devices, offering robust electrochemical energy storage. However, the challenge remains to develop a simple, scalable fabrication method that achieves both high energy and power densities. In this study, we present a refined approach to fabricating MSCs with 3D interconnected graphene/carbon nanotube (CNT) composite electrodes. Our method combines flash lamp annealing (FLA) and laser ablation, where FLA converts graphene oxide (GO) and CNT composite films into 3D‐structured graphene/CNT electrodes, and laser ablation precisely patterns them into interdigitated designs. This dual‐process technique produces MSCs with exceptional electrochemical performance, including an impressive areal capacitance of 26.11 mF/cm2 and a volumetric capacitance of 31.88 F/cm3. These devices also achieve energy densities of 3.72 μWh/cm2 and 4.43 mWh/cm3, maintaining 97% of their initial capacitance under extreme bending, demonstrating outstanding mechanical flexibility and durability. Furthermore, the scalability of this method was validated by configuring MSCs in series and parallel, achieving enhanced voltage and current outputs without additional interconnections. Overall, the integration of FLA and laser ablation holds significant promise for advancing the performance and scalability of micro‐sized energy storage devices, addressing the growing need for efficient, flexible, and high‐capacity micro‐power sources.

Boosted electron accumulation around Fe atom by asymmetry coordinated FeN3S1 for efficient oxygen reduction reaction

Catalysts with atomically dispersed Fe–N4 active sites have emerged as promising alternatives for noble-metal catalysts in oxygen reduction reaction (ORR). However, the sluggish reaction kinetics limit their further utilization. Herein, asymmetry active sites FeN3S1 located on mesoporous carbon matrix (Fe–N3S1/Cmeso) are constructed and verified as efficient ORR catalysts with fast reaction kinetics. The synthesized Fe–N3S1/Cmeso catalysts exhibit a half-wave potential of 0.92 V in alkaline electrolyte, a higher power density (178 mW cm−2) and a long-term durability (350 h) in Zn-Air battery. Mechanism study demonstrates that the specific structure induces accumulated electronic density and decreased d band center of Fe atoms which optimize the adsorption energy with OH∗ intermediates thus boosting the intrinsic activity. Moreover, the uniform mesoporous structure significantly increases the accessibility of active sites. This work offers a new perspective to optimize the adsorption strength of reaction intermediates for enhanced ORR.

High-performance hydrogel membranes with superior environmental stability for harvesting osmotic energy

A collection of innovative nanofluidic systems has been developed to harness Gibbs free energy and convert it into osmotic energy. Nevertheless, these systems frequently encounter challenges such as low output power density, inadequate mechanical stability, and diminished performance in extreme conditions. In this work, we utilized a simple thermal polymerization method to fabricate a charged phytic acid (PA)–acrylic acid (AA)–3-sulfopropyl acrylate potassium salt (SPAK) hydrogel (PASH) membrane with anti-drying and anti-freezing properties, alongside mechanical stability. Using a silicon window with a testing area of 3 × 10−8 m2, a high power density of 30.94 W/m2 was achieved in artificial seawater and river water environments (0.5/0.01 M NaCl). Notably, an even higher power density of 103.9 W/m2 was attained in artificial saline lake and river water environments (5/0.01 M NaCl). Meanwhile, the PASH membrane demonstrated outstanding performance in low temperatures and various acidic and alkaline environments, offering the potential for osmotic power generation in extreme conditions. This work provides essential theoretical foundations and experimental evidence for the development of sustainable osmotic energy conversion technologies, contributing to the advancement and innovation in the field of blue osmotic energy.

Enhanced energy storage efficiency of an innovative three-dimensional nickel cobalt metal organic framework nanocubes with molybdenum disulphide electrode material as a battery-like supercapacitor

Recently, metal-organic frameworks (MOFs) with transition metal sulfides have gained much attention as electrode materials for supercapacitors (SCs). In this work, 3D-NCMOF@MS NCs, incorporating two-dimensional molybdenum disulphide (2D-MS) nanosheets and three-dimensional nickel cobalt-MOF nanocubes (3D-NCMOF NCs) are synthesized by a solvothermal and precipitation process. Owing to their enhanced electrical conductivity and huge surface area, the 3D-NCMOF@MS NCs produce superior electrochemical responses in SCs compared to 2D-MS and 3D-NCMOF NCs. The results demonstrate that the synergistic 3D-NCMOF@MS NCs increased specific capacitance up to 1048 Fg−1 at 1 Ag−1, revealing outstanding cycle stability with a capacitance retention of 99.06 %. Besides, the exposed high-power density of 3D-NCMOF@MS NCs reached 400 W kg−1 as well as an outstanding maximum energy density of 188.64 Wh kg−1. Such synergistic effects of the multivalent states of Ni, Co, and Mo promote electrochemical characteristics, implying that the 3D-NCMOF@MS NCs could potentially be used in energy storage systems, boosting electrochemical performance.

Synergy of high-intensity chromium ion implantation and ion beam energy impact on the zirconium alloy surface

The peculiarities and modes of material modification with high-intensity, high-power density ion beams on the irradiated surface are studied for the first time. Chromium ions are implanted into a zirconium alloy using a 25 kW/cm2, 450 μs beam at the pulse repetition rates within 8–35 pps. Every high-energy ion pulse impact is followed by ultrafast cooling of the surface due to heat removal into the target material. Three modes are studied at the temperatures of 580, 700, and 900 °C with an additional pulsed heating. An increase in the average target temperature from 580 to 700 °C within 1 h at the same pulse power density allows increasing the depth of chromium ion alloying from 1.5 to more than 7 μm. The use of ultrafast cooling of the Zr1%Nb alloy surface offers a grain size reduction from a few μm to approximately 50–250 nm, without any microstructural changes throughout the sample volume. An inhomogeneous chromium ion distribution over the target surface and depth is observed.

Impact of Laser Ablation Strategies on Electrochemical Performances of 3D Batteries Containing Aqueous Acid Processed Li(Ni0.6Mn0.2Co0.2)O2 Cathodes with High Mass Loading

Lithium-ion batteries are currently one of the most important energy storage devices for various applications. However, it remains a great challenge to achieve both high energy density and high-power density while reducing the production costs. Cells with three-dimensional electrodes realized by laser ablation are proven to have enhanced electrochemical performance compared to those with conventional two-dimensional electrodes, especially at fast charging/discharging. Nevertheless, laser structuring of electrodes is still limited in terms of achievable processing speed, and the upscaling of the laser structuring process is of great importance to gain a high technology readiness level. In the presented research, the impact of different laser structuring strategies on the electro-chemical performance was investigated on aqueous processed Li(Ni0.6Mn0.2Co0.2)O2 cathodes with acid addition during the slurry mixing process. Rate capability analyses of cells with laser structured aqueous processed electrodes exhibited enhanced performance with capacity increases of up to 60 mAh/g at high current density, while a 65% decrease in ionic resistance was observed for cells with laser structured electrodes. In addition, pouch cells with laser structured acid-added electrodes maintained 29–38% higher cell capacity after 500 cycles and their end-of-life was extended by a factor of about 4 in contrast to the reference cells with two-dimensional electrodes containing common organic solvent processed polyvinylidene fluoride binder.

An electrical double-layer supercapacitor based on a biomass-activated charcoal electrode and ionic liquid with excellent charge-discharge cycle stability&amp;nbsp;

Supercapacitors that exhibit high power density and safety are emerging as alternative energy storage devices. The construction and performance of a supercapacitor using the ionic liquid, triethylammonium thiocyanate, as the electrolyte and biomass-activated charcoal films as the electrode are described. Enhancements in both energy and power density were observed even for 10,000 charge-discharge cycles. The fabricated supercapacitor with ionic liquid and activated charcoal-based electrodes showed an impressive specific capacitance retention of 142% even after 10,000 cycles at a scan rate of 500 mv s-1, which is attributed to the clearing of ion conducting pathways and enhanced charge transport with increasing temperature. Impedance analysis confirmed the reduction of resistive losses with increasing cycle numbers. The initial energy and power densities of the Electrical double-layer capacitance (EDLC) were 0.926 W h kg-1 and 5681 W kg-1, and they showed 42.2 % and 60.6 % increments after supercapacitors cycles. The study reveals low-cost biomass-based activated carbon electrodes and trimethylamine thiocyanate can be used to prepare supercapacitors with remarkable cycling performances.

Dual Fe/I Single-Atom Electrocatalyst for High-Performance Oxygen Reduction and Wide-Temperature Quasi-Solid-State Zn-Air Batteries.

Oxygen reduction reaction (ORR) electrocatalysts are essential for widespread application of quasi-solid-state Zn-air batteries (ZABs), but the well-known Fe-N-C single-atom catalysts (SACs) suffer from low activity and stability because of unfavorable strong adsorption of oxygenated intermediates. Herein, the study synthesizes dual Fe/I single atoms anchored on N-doped carbon nanorods (Fe/I-N-CR) via a metal-organic framework (MOF)-mediated two-step tandem-pyrolysis method. Atomic-level I doping modulates the electronic structure of Fe-Nx centers via the long-range electron delocalization effect. Benefitting from the synergistic effect of dual Fe/I single-atom sites and the structural merits of 1D nanorods, the Fe/I-N-CR catalyst shows excellent ORR activity and stability, superior to Pt/C and Fe or I SACs. When the Fe/I-N-CR is employed as cathode for quasi-solid-state ZABs, a high power density of 197.9mW cm-2 and an ultralong cycling lifespan of 280h at 20mA cm-2 are both achieved, greatly exceeding those of commercial Pt/C+IrO2 (119.1mW cm-2 and 47h). In addition, wide-temperature adaptability and superior stability from -40 to 60 °C are realized for the Fe/I-N-CR-based quasi-solid-state ZABs. This work provides a MOF-mediated two-step tandem-pyrolysis strategy to engineer high-performance dual SACs with metal/nonmetal centers for ORR and sustainable ZABs.