Improved Power Density Research Articles

Tailoring the electron free path in an ultra-lightweight gas-solid composite insulation system for high dielectric strength

Reliable electric insulation is the premise for the application of high-voltage technologies, such as power transmission, emergent electrified transportations, and advanced propulsion systems. With the current insulation strategy, the credibility of insulation system depends on the sufficient insulation materials usage, suffering from bulky structure, expensive production costs and environmental pollution. Here, we propose a strategy that applies a lightweight multiple-barrier skeleton in gas insulation to tailor electron free path and restrain electron avalanche, thus realizing a high insulation strength with less material usage. This strategy is verified by the composite insulation of porous polyimide aerogel and various types of insulating gases. It achieves a comparable insulation strength to conventional polymers by less than 10% materials usage. With above insulation strategy, a 152.5% improvement in power density and a 54.6% weight reduction are acquired in the cable system for more or all electric aircraft. This strategy inspires the design of efficient insulation solution with both high breakdown strength and lightweight.

Perovskite Nanocrystals Induced Core-Shell Inorganic-Organic Nanofibers for Efficient Energy Harvesting and Self-Powered Monitoring.

The emerging field of wearable electronics requires power sources that are flexible, lightweight, high-capacity, durable, and comfortable for daily use, which enables extensive use in electronic skins, self-powered sensing, and physiological health monitoring. In this work, we developed the core-shell and biocompatible Cs2InCl5(H2O)@PVDF-HFP nanofibers (CIC@HFP NFs) by one-step electrospinning assisted self-assembly method for triboelectric nanogenerators (TENGs). By adopting lead-free Cs2InCl5(H2O) as an inducer, CIC@HFP NFs exhibited β-phase-enhanced and self-aligned nanocrystals within the uniaxial direction. The interface interaction was further investigated by experimental measurements and molecular dynamics, which revealed that the hydrogen bonds between Cs2InCl5(H2O) and PVDF-HFP induced automatically well-aligned dipoles and stabilized the β-phase in the CIC@HFP NFs. The TENG fabricated using CIC@HFP NFs and nylon-6,6 NFs exhibited significant improvement in output voltage (681 V), output current (53.1 μA) and peak power density (6.94 W m-2), with the highest reported output performance among TENGs based on halide-perovskites. The energy harvesting and self-powered monitoring performance were further substantiated by human motions, showcasing its ability to charge capacitors and effectively operate electronics such as commercial LEDs, stopwatches, and calculators, demonstrating its promising application in biomechanical energy harvesting and self-powered sensing.

Airfoil flow field for proton exchange membrane fuel cells enhancing mass transfer with low pressure drop

Optimal configuration of bipolar plate (BP) embedding flow field is of great significance in improving the power density and durability of proton exchange membrane fuel cells (PEMFCs). Inspired by the airfoil in aircraft dividing the airflow into two streams causing pressure difference, a novel airfoil flow field (AFF) is designed to enhance the mass transfer capacity in channel and across the rib between two adjacent channels, which hardly increases the pressure drop in channel, unlike many baffle designs. The performance improvement achieved by implementing AFF in PEMFC is compared with common parallel flow field (PFF) and the wave flow field (WFF) by experimental test with respect to polarization curve and electrochemical loss and numerical simulation via a three-dimensional (3D) PEMFC model. The experimental results indicate that the novel AFF exhibits best fuel cell performance at various operation conditions (e.g. relative humidity, air stoichiometric ratio) mainly benefitted from the enhanced oxygen transfer, which contributes to the improvement of maximum power density by 8.85 % and 14.37 % compared to PFF and WFF, respectively. The modeling results indicate that the pressure drop increase in AFF is negligible compared with PFF, and is even slightly lower than WFF, indicating high practicability. Moreover, the utilization of AFF also helps the uniformity of oxygen concentration, current density and temperature in PEMFC.

Improved energy storage properties through multilayer stacking of relaxor ferroelectric and antiferroelectric thin films

Abstract Multilayers of relaxor ferroelectric (Pb0.92La0.08Zr0.52Ti0.48O3) and antiferroelectric (Pb0.96La0.04Zr0.98Ti0.02O3) thin films were fabricated on Pt/Ti/SiO2/Si substrates by Chemical Solution Deposition (CSD) method. The properties of the independent relaxor ferroelectric (RFE denoted as R) and antiferroelectric (AFE denoted as A) thin films were compared with their various stack configurations made by alternatively coating the R and A layers in the patterns of R/A, R/A/R, R/A/R/A/R/A, A/R, A/R/A, and A/R/A/R/A/R. The crystallographic studies confirmed the coexistence of both RFE and AFE phases in the multilayer stacks which was further verified by electrical characterizations. The multilayer stack showed improved power density (PD), energy efficiency (η), and reduced dielectric loss compared to individual R and A films. Among all the multilayer configurations, the stack with A/R/A/R/A/R layer exhibited significant improvement in energy efficiency (94%) which is higher than the reported results so far on multilayer structures.

Ni and Ru bimetal nanoparticles-anchored porous Mo2C nanorods used as an internal reforming catalyst layer for hydrocarbon-fueled solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are considered the most efficient technology for the direct conversion of hydrocarbons to electrical energy. Although the commonly used Ni/YSZ cermet materials in SOFCs show excellent electrocatalytic properties in H2 fuel, they suffer from carbon deposition problem when hydrocarbon fuels are used. In this work, we study the use of Ni0·05Ru0.05-Mo2C with a porous nanorod-shaped morphology as an internal reforming catalyst layer for methane-fueled SOFCs to solve the degradation of cell performance due to carbon deposition. The electrochemical performance and coking tolerance of two types of cells with and without the catalyst layer were systematically studied using methane and hydrogen as fuels. With the catalyst layer, the single cell using methane as fuel exhibits an improvement in peak power density by 24%, increasing from 297 to 367 mW cm−2 and there was no diffusion barrier for fuel gases within the cell. Furthermore, the cell can stably run for 100 h in methane at 700 °C. The improvement of electrochemical performance is attributed to the synergistic effect of Ni and Ru sites anchored on the porous Mo2C nanorods catalyst based on strong metal-support interactions, promoting the effective catalytic conversion of CH4 to CO and H2. This study demonstrates that the integration of a catalyst layer for internal reforming is an effective strategy for the direct use of methane in SOFCs.

Design and investigation of novel gradient flow fields for proton exchange membrane fuel cell

Ensuring sufficient gas supply and high distribution uniformity are crucial issues in the flow field design to improve the performance and durability of proton exchange membrane fuel cell (PEMFC). However, previous studies often ignore the gas-water distribution variations along the flow direction and adopt identical design for the entire flow field, resulting in unsatisfactory performance. To fill in this gap, this paper innovatively proposes two types of gradient flow field (gradient narrowing and gradient droplet) considering the gas-water distribution characteristics. The channel of the gradient narrowing flow field gradually decreases in all directions along the flow direction, and the gradient droplet flow field is composed of staggered droplet blocks, and the distribution density gradually decreases along the flow direction. The Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method is used for the comprehensive evaluation of flow fields. The results demonstrate that the gradient flow field can significantly improve the performance and physical field distribution. The gradient narrowing flow field has the best performance, with 11.39 % improvement in peak power density, 77.96 % increment in average oxygen mass fraction, and 43.11 % improvement in oxygen uniformity compared to parallel flow field. Further, the key geometric parameters sensitivity analysis of gradient narrowing flow field is carried out. This study contributes to understanding the underlying mechanism of mass transfer properties in the novel gradient flow field, and exploring its potential for high-performance flow fields design.

Double B-type magnetic integrated transformer based input-parallel output-parallel LLC resonant converter modules

The LLC resonant converter used in high-power situations suffers from the problems of high conduction loss and current stress, which can be solved using input-parallel output-parallel (IPOP)-connected converter modules. However, this leads to a multiple increase in the number of magnetic components, which reduces power density. Magnetic integration technology is an effective way to reduce the volume of converters. Currently, the magnetic integrated transformer based on EE-type cores is widely used to realize miniaturization, and it uses leakage inductance instead of resonant inductance to improve power density. However, leakage inductance is difficult to control, and the external radiated magnetic field will produce serious eddy current loss and electromagnetic interference. This article proposes a novel double B-type magnetic integrated transformer, which can integrate the magnetic components of two LLC resonant converters simultaneously and where the resonant inductances are wound independently. The structure contains four low reluctance branches, which are used as the cores of the transformer and the resonant inductance. The decoupling integration method, which integrates the four components into a single core, has been used to increase core utilization and improve power density. On this basis, the transformer’s high- and low-voltage windings are cross-arranged to reduce the magnetic field intensity in space, further decreasing the loss and electromagnetic interference. Compared with the EE-type magnetic integrated transformer, the volume of the proposed structure is reduced by 5.9%. A 400W experimental prototype is built, and the results verify the validity of the design.

Design of Z source converter with the genetic-based chicken swarm algorithm for closed loop control of PV integrated grid

A single-phase grid coupled PV system with a switched Z-source boost converter is analysed on the basis of closed-loop control using a novel hybrid algorithm. As PV results in low-voltage DC, it is vital to step up this low-voltage DC and so a suitable DC-DC converter is needed. A switched Z-source boost converter is utilized for the step-up process as this converter uses minimum passive components, thereby reducing the cost with improved power density. Control of the converter is carried out by a closed loop control using a PI controller tuned with a novel genetic-based chicken swarm (GBCS) algorithm which combines the merits of both genetic and chicken swarm able to deal with complex problems, simple with fast convergence. The output of the converter is then given to the grid through a single-phase VSI in which DC–AC conversion takes place. While connecting PV to the grid, another factor to be taken care of is grid synchronization which is accomplished by a PI controller in which the actual and reference power are analogized. The proposed control scheme is simulated in a MATLAB environment and the outcomes are observed. The grid current THD of 1.6% and reactive power compensation is accomplished.

Isotonic separation enabled efficient low-grade heat conversion with thermal-responsive ionic liquids

The osmotic heat engine (OHE) stands out as a promising approach for converting low-grade heat into electricity owing to its scalability. However, challenges arise from the substantial latent heat consumption or the restricted concentration difference during the regeneration stage, constraining improvements in energy efficiency and power density. Here, we introduce an isotonic separation process to a thermal-responsive ionic liquid (IL)-based OHE system, where the water-rich phase of the IL after phase transition is further filtrated into pure water and another part of the IL-rich phase with constant osmotic pressure. This isotonic process amplifies the net energy generated in the mixing process. Ultimately, a state-of-the-art Carnot-relative efficiency of 48% is achieved within a temperature difference of 25–40 °C, where the hot side is maintained at 60 °C. Additionally, a forward-osmosis device yields an exemplary peak power density of 10.9 W/m2.

DC Cascaded Energy Storage System Based on DC Collector With Gradient Descent Method

With the continuous development of distributed energy, the energy storage system (ESS) is indispensable in improving power quality. Aiming at the application of large-capacity storage battery access to medium voltage dc power grid, a dc cascaded energy storage system based on the dc collector is proposed, and the characteristic, topology and control are presented in detail. In this scheme, the low-voltage storage batteries are accessed to medium voltage dc bus directly with dc collectors, which not only has higher efficiency, but also improves power density. Especially, the diversity of state of charge (SOC) is only reflected in the duty cycle of submodules (SMs), rather than the voltage deviation. Further, a variable angle carrier phase-shifted modulation with gradient descent method is discussed to eliminate the dominant current harmonics. By calculating the harmonic amplitude and solving the Jacobian matrix, the gradient that reduces harmonic current is obtained, and the optimal combination of the carrier phases is deduced by iterative calculation. Meanwhile, the method can be extended in the dc collector with any number of SMs to eliminate the dominant harmonics. Finally, the experimental prototype is built and the benefit of proposed solution is verified.

System-Level Performance Degradation Prediction for Power Converters Based on SSA–Elman NN and Empirical Knowledge

The degradation of power converter perfor-mance is one of the most critical issues of complex system with the improvement of power capacity and density. Power converter bears severe electrical and thermal stress, resulting in an increase in the probability of failure and significant economic losses. Most research addresses performance evaluation either through reliability theory without physical understanding or through data-driven methods requiring high experimental cost. Few studies focus on predicting system-level performance degradation, which is technically difficult as many components degrade randomly. Identifying the parameters of electronic com-ponents based on sensor data has become possible with the development of neural networks and computational power. Therefore, this paper proposes a novel system-level power degradation predicting framework, which combines the advantages of neural networks in nonlinear fitting and empirical knowledge to predict the degradation of power converter. In addition, a comprehensive and improved feature parameter screening method is proposed to iden-tify the most critical feature parameters of the power con-verter systems. Furthermore, the neural network parameter identification method based on SSA-Elman NN (Sparrow Search Algorithm - Elman Neural Network) is introduced to improve prediction accuracy. Finally, the result shows that the proposed method can accurately predict the degrada-tion of the system by using a DC-DC converter as an ex-ample.

Self-assembly and low-temperature sintered La0.6Sr0.4CoO3-δ @ Gd0.1Ce0.9O2-δ composite cathode with rich electrode/electrolyte interface and enhanced performance in harsh condition

In order to improve cost competitiveness and the further application of metal-supported cells, it is important to explore cathodes suitable for low-temperature sintering. However, decreasing cathode sintering temperature while maintaining robust interface of cathode/electrolyte and decent electrochemical performances is challenging for solid oxide fuel cells. Herein, by combining the Pechini method with one-pot method, La0.6Sr0.4CoO3-δ @ Gd0.1Ce0.9O2-δ (LSC@GDC) composite cathodes are prepared and investigated, compared with mechanically mixed LSC-GDC cathodes. At the cathode sintering temperature of 800 °C, the LSC@GDC cathode single cells perform better performances, with deceased resistances, improved power density outputs and better feasibility to wide oxygen partial pressures from 0.21 atm down to 0.03 atm. The optimum composition of 70:30 wt% for LSC@GDC is proposed. The anode supported single cell with LSC@GDC30 cathode exhibits a maximum power density of 0.789 W/cm2 and 0.545 W/cm2 at 750 °C, under cathode oxygen partial pressure of 0.21 atm and 0.03 atm, respectively. Moreover, the low temperature sintered LSC@GDC50 cathode performs decent durability during repeatedly controlled thermal cycling over 10 times.

High‐power microbial‐fuel‐based hybrid cells with three‐dimensional graphene‐coated iron foam as an anode control Fe3+ release

AbstractMicrobial fuel cells (MFCs) benefit from the introduction of iron in the anode, as its multiple valence states and high electron‐catalytic activity led to improved power densities in MFCs. However, the effect of long‐term Fe3+ release into the electrolyte on the power density of MFCs is often overlooked. Herein, an anode consisting of a three‐dimensional iron foam uniformly coated by reduced graphene oxide (rGO/IF) with a suitable loading density (8 g/m2) and a large specific surface area (0.05 m2/g) for high‐density bacterial loading was prepared. The hybrid cells based on the rGO/IF anode exhibit a maximum power density of 5330 ± 76 mW/m2 contributed by MFCs and galvanic cells. The rGO/IF anode enables continuous Fe3+ release for high electron‐catalytic activity in the electrolyte during the discharging of the galvanic cells. As a result, the hybrid cells showed a power density of 2107 ± 64 mW/m2 after four cycles, facilitated through reversible conversion between Fe3+ and Fe2+ in the electrolyte to accelerate electron transfer efficiency. The results indicate that the rGO/IF anode can be used for designing and fabricating high‐power MFCs by optimizing the rate of release of Fe3+ in the electrolyte.

A high power metal-supported protonic ceramic fuel cell using increased proton conductivity in the cathode functional layer of La1−xSrxScO3 (LSSc, x = 0.1–0.25)

Metal-supported protonic ceramic fuel cells (PCFCs) with LSSc layers achieve enhanced proton conductivity and improved power density.

Improved Model Predictive Control With Reduced DC-Link Capacitor RMS Current for Back-to-Back Converter-Fed PMSM Drives

A low root mean square (RMS) current flowing through the intermediate DC-link capacitor is always desired in the back-to-back (BTB) voltage source converters (VSCs)-fed motor drive, such that the designed capacitor lifespan can be extended or a lower DC-link size could be the alternative with improved power density. The conventional modulator-based control involves the inherent carrier-based switching operation, and hence the dominant harmonics at carrier frequency multiplier and carrier sideband are introduced into the capacitor current. Therefore, the finite-control-set model predictive control (FCS-MPC) is proposed to optimize the capacitor RMS current. The direct switching pulse generation without using the carrier can give a distinctive capacitor current spectrum and more possible current pulse cancellation between the BTB VSCs can be conveniently achieved through the cost function. Besides, the acceptable grid-current quality and the motor performance are maintained by using a tunable weighting factor. The simulated and experimental results highlight the effectiveness and benefits of the proposed method in terms of 20%-35% capacitor RMS current reduction compared to the synchronous carrier-based space vector pulse-width modulation (SVPWM) scheme and also significant improvements over the distributed predictive manner.

Realizing one-step two-electron transfer of naphthalene diimides via a regional charge buffering strategy for aqueous organic redox flow batteries.

Naphthalene diimide derivatives show great potential for application in neutral aqueous organic redox flow batteries (AORFBs) due to their highly conjugated molecular structure and stable two-electron storage capacity. However, the two-electron redox process of naphthalene diimides typically occurs via two separate steps with the transfer of one electron per step ("two-step two-electron" transfer process), which leads to an inevitable loss of voltage and energy. Herein, we report a novel regional charge buffering strategy that utilizes the core-substituted electron-donating group to adjust the redox properties of naphthalene diimides, realizing two electron transfer via a single-step redox process ("one-step two-electron" transfer process). The symmetrical battery testing of NDI-DEtOH revealed exceptional intrinsic stability lasting for 11 days with a daily decay rate of only 0.11%. Meanwhile, AORFBs with NDI-DMe/FcNCl and NDI-DEtOH/FcNCl exhibited a remarkable 40% improvement in peak power density at 50% state of charge (SOC) in comparison to NDI/FcNCl-based AORFBs. In addition, the battery's energy efficiency has increased by 24%, resulting in much more stable output power and significantly improved energy efficiency. These results are of great significance to practical applications of AORFBs.

Carbon nanofiber/graphene hybrids anchoring Fe, N, and S heteroatoms simultaneously enhancing extracellular electron transfer and biofilm adhesion in microbial fuel cells

The aerogel structure composed of FeS/Fe3C@CNFs and rGO has a 3D stereoscopic structure, which can provide sufficient sites for biofilm attachment and nutrient transportation, facilitating the improvement of MFC power density.

Thermal Optimization Design of a Intelligent Programmable Controller Based on CFD Software

With the increasing functionality of intelligent programmable controllers and the continuous improvement in power and component density, the problem of rapidly rising temperatures during operation has become increasingly prominent, directly affecting the controller's lifespan and stability[1]. Therefore, improving the heat dissipation efficiency of intelligent programmable controller modules has become a key focus of research. This paper introduces a method of installing aluminum alloy heat sinks on the core chip of the controller and carefully designing the fin shape and size of the heat sink to enhance heat conduction and heat convection effects, improving heat dissipation performance. This paper also constructs a thermal equivalent model of the controller and simulates the impact of different fin parameters on heat dissipation performance. Experimental results show that when the fin height is 5 millimeters, thickness is 2 millimeters, and spacing is 4 millimeters, the heat sink exhibits the highest thermal conductivity and the lowest thermal resistance, achieving optimal heat dissipation effectiveness.

Improved power density based magnetically isolated better power quality bidirectional integrated on-board charger

Improved power density based magnetically isolated better power quality bidirectional integrated on-board charger

Improved power density based magnetically isolated better power quality bidirectional integrated on-board charger

Improved power density based magnetically isolated better power quality bidirectional integrated on-board charger