Increase In Power Density Research Articles

Thermal Design of Stacked Power Modules for Electric Drive Applications

This paper reports the thermal design of a stacked arrangement inserting four IGBT modules between five heat sinks to achieve good cooling performance while enabling them to be installed into the limited space. Such stacked four IGBT modules can be used for a variable voltage converter (VVC), a three-phase motor inverter (M-INV) and a three-phase generator inverter (G-INV) of one electric control system in one electric vehicle or hybrid electric vehicle. Work presented in this paper are the thermally related structure design and thermalelectric and computational fluid dynamics coupled simulation, while the prototyping and thermal test of the stacked arrangement are still ongoing. The simulation results indicate that the stacked arrangement can be designed into a compact 121 mm × 94.7 mm × 90.8 mm structure while achieving the maximum virtual junction temperature below 150°C under the coolant feed temperature of 70°C, flow rate of 10 L/min and pressure drop of 0.16 bar for the VVC delivering 150 kW, the M-INV delivering 100 kW and the G-INV delivering 50 kW. If validated with the ongoing work, the stacked arrangement can be employed to increase power density and improve electrical and thermal performance of the power modules in the electric control systems with multiple converters/inverters.

Mechanisms of enhanced heat transfer of piston oscillating cooling in a heavy-duty diesel engine

The thermal load and reliability of pistons become major concerns with the increase of power density of internal combustion engines. The oscillating cooling technology is often adopted to enhance the heat transfer of pistons in heavy-duty diesel engines. To understand the heat transfer mechanisms, this study developed an optical oscillating cooling piston based on a real heavy-duty engine. The characteristics of two-phase oscillating flows were optically observed under different conditions. As engine speed increased from 100 to 700 r/min or oil supply pressure decreased from 0.2 to 0.8 bar, the oscillation intensity of the two-phase flow gradually increased and the oscillating flow pattern developed from slug to intermittent mist flow. Furthermore, computational fluid dynamics simulations were performed to analyze the heat transfer mechanisms of oscillating cooling and optimize the structure of the piston. The results showed that the heat transfer coefficient of oscillating cooling can be decomposed into three components, namely conventional flow, oscillation enhanced and jet flushing parts. The conventional flow part accounts for the largest proportion of the total heat transfer coefficient, whose value is positively correlated with oil flow rate. The oscillation enhanced part is optimal when the oil filling rate is between 40 % and 60 %. The jet flushing part can lead to a higher temperature gradient in the outer cooling gallery and thus increased thermal stress. The cooling capacities of inner and outer galleries are mainly influenced by the diameters of the oil outlet and distributor pipes, respectively. The jet flushing part can be controlled by changing the inclination angle of the distributor pipe. Finally, optimization achieved an improvement of 8.3 % in cooling capacity of inner cooling gallery and a reduction of 27.5 % of heat dissipation inhomogeneity in the piston.

Boosting the power density of Zr and Ni co-doped BaFeO3 cathode for proton-conducing solid oxide fuel cells

A novel cathode material, denoted as BaZr0.26Fe0.64Ni0.1O3-δ (BZFN010), has been suggested for application in proton-conducting solid oxide fuel cells (H-SOFCs), aiming to enhance electrochemical performance. The introduction of Zr into the original BaFeO3-δ (BFO) results in improved chemical stability against CO2. However, despite this enhancement, the electrochemical performance remains unsatisfactory. Hence, we leveraged the outstanding stability of BZF and incorporated Ni, a well-known element renowned for its remarkable catalytic qualities, into the cell to augment its properties. This enhancement is substantiated by a combination of experimental and theoretical calculations. When employed as a cathode, the BZFN010 material exhibited markedly superior performance compared to the BaZr0.36Fe0.54O3 (BZF36) cathode. It demonstrated a 57% increase in power density, rising from 998 mW cm-2 to 1570 mW cm-2 at 700 °C. This study employs a chained-style cathode exploration strategy, commencing with the conventional BFO cathode, progressing to the enhanced stability of BZF36, and culminating in the optimized catalytic activity of BZFN010. Our work represents an intriguing strategy for the design of H-SOFC cathodes.

A light Darwin implementation of Maxwell’s equations to quantify resistive, inductive, and capacitive couplings in windings

High operating frequency is an enabler of high key performance indicators, such as increased power density, in electrical machines. The latter enhances the cross-coupling of resistive–inductive–capacitive phenomena in windings, which may lead to significant loss in performance and reliability. The full-wave Maxwell’s equations can be employed to characterize this coupling. To address the frequency instability that arises as a result, a simplification known as the Darwin formulation can be employed, where the wave propagation effects are neglected. Still, this modification is prone to ill-conditioned systems that necessitate intricate pre-conditioning and gauging steps. To overcome these limitations, a fast 2D formulation is derived, which preserves the current continuity conservation along the model depth. This implementation is validated experimentally on a laboratory-scale medium-frequency transformer. The computed impedances for the open- and short-circuit modes of the transformer are validated using measurements and compared with the multi-conductor transmission line model that is widely adopted for the analysis mentioned above. The developed formulation demonstrates a high accuracy and outstanding frequency stability in a wide frequency range, becoming an efficient and computationally light method to investigate the interconnected resistive, inductive, and capacitive effects in windings.

Challenges in urban data center design

The data center market is experiencing significant growth, with each new facility requiring increased power density and cooling needs. This growth brings new challenges, including noise pollution and its impact on nearby communities, which becomes excessively difficult in urban environments. This presentation will explore the issues faced by data centers in urban environments and discuss potential solutions to create quieter facilities. Key points include:—Physical challenges: Every site design faces numerous physical constraints, including limited rooftop and equipment room space, tight and complex adjacencies of neighboring sites, and design and performance standards for equipment.—Political issues: Every site and community have a different set of laws and regulations that a site needs to meet, and often go beyond to ensure that the community will accept the site.—People issues: Data centers must navigate contentious relationships with neighbors and address noise concerns to maintain a positive reputation. By addressing these challenges, data centers can minimize noise pollution and maintain positive relationships with surrounding communities, ensuring a sustainable future for the industry in urban environments.

Frequency-multiplexed on-demand storage in five modes of atomic frequency comb through simultaneous application of control pulses.

In quantum communication with quantum repeaters, multiplexed quantum memory is expected to enhance communication rates. When using an atomic frequency comb (AFC) for on-demand storage, the frequency mode number is often limited by the optical power of the control pulses. Here, using a space-coupled waveguide electro-optic modulator, we increased the output power, allowing us to apply control pulses to multiple modes simultaneously. Further, through enhancement of an experimental setup that increases power density, we increased the number of modes. Consequently, we pioneered, to the best of our knowledge, on-demand storage using five modes of AFC. This technology is a significant achievement toward frequency-multiplexed on-demand quantum memory.

Enhancing bioelectricity generation from wastewater in microbial fuel cells using carbon nanomaterials

AbstractBACKGROUNDMicrobial fuel cells (MFCs) offer a promising approach for treating wastewater and generating electrical energy simultaneously. However, their implementation in wastewater treatment plants is hindered by the limited electricity generation, often attributed to the electrolyte's high resistance. This study aimed to improve bioelectricity generation in MFCs by adding nanomaterials to the electrolyte to enhance conductivity.RESULTSThree types of nanomaterials – carbon nanotubes (CNTs), graphitic carbon nitride (g‐C3N4), and reduced graphene oxide (r‐GO) – were synthesized and addition to the electrolyte at a concentration of 50 mg in 1.5 L. MFC performance was evaluated, employed a hydraulic retention time (HRT) of 140 h, and compared to a control with no nanomaterials added. The addition of nanomaterials significantly improved MFC performance. Compared to the control, the MFCs with CNTs, g‐C3N4, and r‐GO exhibited higher voltage: 1.301 V (CNTs), 1.286 V (g‐C3N4), 1.280 V (r‐GO) versus 0.570 V (control); increased power density: 14.11 mW m−3 (CNTs), 13.78 mW m−3 (g‐C3N4), 13.66 mW m−3 (r‐GO) versus 2.71 mW m−3 (control); enhanced areal power density: 21.06 mW m−2 (CNTs), 20.57 mW m−2 (g‐C3N4), 20.39 mW m−2 (r‐GO) versus 4.04 mW m−2 (control); and improved coulombic efficiency: 19.43% (CNTs), 19.19% (g‐C3N4), 19.11% (r‐GO) versus 8.54% (control).CONCLUSIONIncorporating nanomaterials into the MFC electrolyte significantly increased bioelectricity generation by 5.21 times and coulombic efficiency by 2.28 times compared to the control. This improvement is attributed to the high specific surface area of the nanomaterials, which facilitates the adhesion and growth of microorganisms around the anode, enhancing direct electron transfer. © 2024 Society of Chemical Industry (SCI).

Design of a flow channel with vortex generators for performance improvement of flow-electrode capacitive mixing under low pressure drop conditions

Salinity gradient power generation is a novel renewable energy technology that generates electricity by exploiting the disparity in salt concentration between bodies of water with high and low salt content, using techniques such as capacitive mixing with flow electrodes (F-CapMix). In this research, we conducted a comprehensive numerical analysis to examine the fluid dynamics and particle behavior of saline water and activated carbon within a flow electrode system equipped with vortex generators on the inner walls of the flow channels. The maximum and net power densities of the F-CapMix for a flow channel with vortex generators were evaluated experimentally. On average, the introduction of vortex generators into the flow channel resulted in a 35.6 % increase in the maximum power density of the F-CapMix compared to a plain channel. Furthermore, when a vortex generator was incorporated, the net power density, considering the pumping power, showed an average enhancement of 26.3 % at flow rates of 15 ml/min or less. Therefore, we anticipate that the flow channel with integrated vortex generators can be effectively utilized in the F-CapMix electrode system with a negligible impact on the pressure drop.

High Frequency Modeling of Electric Machines Using Finite Element Analysis Derived Data

The use of wide band gap semiconductor switching devices in electric machine drives leads to a significant increase in power density and efficiency compared to conventional silicon-based solutions. However, this technology also presents challenges for the insulation design of electric machines since partial discharges (PDs) may occur due to high peak voltage stress as a result of fast and high frequency switching. To evaluate the risk of PD, it is necessary to understand the voltage distribution within the windings and associated insulation of an electric machine during converter operation. To this end a suitable high frequency model of the machine windings capable of predicting the internal voltage distribution is required. This paper proposes a method of constructing such a model based on finite element analysis (FEA) derived data. The FEA data used to parameterise the model in this work incorporates frequency dependant properties and homogenisation techniques to produce data which captures the high frequency behaviour of the machine. The developed model is compared with measurements in both frequency and time domains, demonstrating the utility and accuracy of the model.

Design Constraints Generalization for Series-Stacked Buffer-Based Active DC Links

Series-stacked buffer (SSB) based active DC links aim to increase power density by replacing bulky DC link capacitor with series connection of significantly lower valued capacitor and auxiliary bidirectional DC/AC converter. SSB design constraint describing quantitative relation between passive components values and system power rating was established to achieve minimal remaining DC link voltage ripple magnitude. This letter generalizes the above requirement, revealing that allowing non-minimum magnitude of residual DC link voltage ripple releases other design constraints, yielding a more optimal solution in terms of full-rating capacitance utilized and/or auxiliary bidirectional DC/AC converter volt-ampere rating. Experimental results validate the proposed methodology, matching corresponding analytical predictions.

Tailoring flow straighteners’ architectures through additive manufacturing to enhance power performance and scale-up microbial fuel cell technology

In an aim to scale up the microbial fuel cell (MFC), this research is a first attempt to investigate the impact of two lattice structures flow straighteners: gyroid and X lattice to compare with the conventional honeycomb flow straightener, fabricated via additive manufacturing. The study focused on assessing their effect on the degradation of domestic wastewater and power generation in a dual chamber recirculation MFC. Other than the geometry, structures were also tested at flow rates of 20 mL/min, 60 mL/min, and 100 mL/min. Our study found that MFC equipped with a gyroid structure flow straightener produced the highest power density of 2871.89mWm−2, followed by the X lattice flow straightener of 2626.56 mWm−2 and 2096.03 mWm−2 with honeycomb flow straightener. ANSYS simulations revealed that this increased power density is attributed to the enhanced mixing of wastewater. Traditional honeycomb-based flow straighteners showed straight streamlines, causing bacteria to settle and leading to lower output voltage. The novel X lattice and gyroid lattice designs ensured uniform substrate mixing, addressing the issue of substrate settling and consequently boosting the MFC's power performance. An optimized flow rate of 60 mL/min yielded the best output. Overall, this study successfully introduced two novel lattice structures for flow straighteners, demonstrating their potential in enhancing power performance and the scalability of this technology when produced using additive manufacturing.

Boosting the proton conductivity, chemical stability, and fuel cell performance of nafion membrane at high operating temperatures and low humidity levels by incorporating phytic acid

Nafion as a conducting polymer faces conduction challenges at high operating temperatures and low humidity levels, leading to an undesired fuel cell performance. Here, we offer a step forward towards the use of Nafion as a high-temperature/low-humidity membrane in fuel cells through the incorporation of phytic acid (IP6) by a doping process. The synergetic effect of IP6 on the physicochemical properties, mechanical characteristics, oxidative durability, proton conductivity, and fuel cell performance of Nafion membrane is studied. Compared to the pristine Nafion, the Nafion-IP6 membrane has shown a 3-fold increase in Young's modulus, a 83%-increase in water uptake, and around 6-fold increase in proton conductivity at 100 °C under 25% RH. The Ea has reached 8.3 kJ/mol, indicating a vehicular/Grotthuss proton conduction mechanism. The Nafion-IP6 based MEA has shown a 71%-increase in the output power density and a 54%-increase in the limiting current density compared to the pristine Nafion-based MEA.

Exogenous electric field as a biochemical driving factor for extracellular electron transfer: Increasing power output of microbial fuel cell

Although microbial fuel cells (MFCs) offer a promising avenue for clean power production, they are hindered by inefficient extracellular electron transfer (EET), thereby resulting in a low power output. This study focused on augmenting MFC power by boosting the EET rate using an exogenous electric field (EEF). By leveraging the dual benefits of microbial electrolysis cells (MECs) in organic waste treatment and energy recovery, we developed an MFC–MEC system that utilizes the EEF from MEC as a connecting link. Two configurations, EEF in the same direction (SD-MFC–MEC) and EEF in the reverse direction (RD-MFC–MEC), were used to examine the EET kinetic rate at the MFC anode in the EEF environment using various electrochemical methods for quantitative evaluation. Our findings revealed that EEF significantly enhanced MFC anode biofilm formation and electrochemical activity, leading to a prominent improvement in electrode reaction rates. The EET rate constants in the SD-MFC–MEC and RD-MFC–MEC were more than double those in the control R-MFC, with power density increases of 117.8% and 108.4%, respectively. The formation of electrochemically active sites within the biofilm induced by EEF has emerged as a crucial factor in amplifying the EET rate, and consequently, the MFC power output. Additionally, the variation in EET rate constants between the SD-MFC–MEC and RD-MFC–MEC was minimal, thereby indicating the negligible impact of the EEF orientation on the EET efficiency. This study provides a novel method for quantitatively examining EET rates, opens up new avenues for further facilitating microbe-to-electrode electron transfer, and promotes the application of MFC–MEC systems in energy recovery, CO2 emission reduction, and waste treatment.

A Comprehensive Review on Matrix-Integrated Single-Stage Isolated MF/HF Converters

A matrix-integrated single-stage isolated MF/HF AC-AC/DC-AC/AC-DC converter topology stands out as an innovative concept, offering a multitude of advantages including minimal output current THDs, near UPF, 4Q operation, smooth BPF capability, and increased power density leading to the converter’s enhanced efficiency, cost-effectiveness, and reliability. These characteristics render it an exemplary choice for RE-based power conversion applications. In fact, the matrix-integrated single-stage isolated MF/HF converters have witnessed an increased adoption of RE-based grid interconnection in recent years, specifically within solar PV, WECS, grid-tied offshore WF, and FC-based applications. RE sources produce variable and intermittent AC power by nature, further necessitating conversion to a stable and grid-compatible AC voltage and frequency. This is where MCs offer distinct advantages when contrasted with the conventional indirect dual-stage VSC-based rectifier–inverter topology. In this paper, a total of 22 matrix-integrated HF isolated converter topologies are broadly explored. Our study provides a comprehensive analysis and classification of matrix-integrated isolated single-stage MF/HF AC-AC converters, DC-AC inverters, and AC-DC rectifier topologies including modified topology architectures, control method, modulation techniques along with significant applications. Within this scope, the matrix-integrated converter topologies are categorized based on their architectures and other relevant subvariants. Our primary objective of this study is to impart a clear understanding of the overarching framework and principles of the matrix-integrated single-stage isolated MF/HF converter topologies and stimulate the creation of new topologies that cater to specific requirements for grid-interconnected systems.

Wind energy harvesting with building-integrated ducted openings: CFD simulation and neural network optimization

Building-integrated wind energy harvesting offers a promising local and decentralized energy generation solution, reducing transmission losses and infrastructure expenses. However, the complex urban wind patterns demand accurate aerodynamic optimization for optimal performance. This study seeks to optimize the geometric design of building-integrated ducted openings to maximize wind energy harvesting. The research aims to create a data-driven model predicting the openings' performance accurately, explore the interlinked impacts of different geometrical variables, find optimal configurations across different building heights, and understand underlying aerodynamic mechanisms. The proposed design comprises a nozzle, throat, and diffuser. To increase power density, a data-driven design optimization method is employed. The optimization process involves determining the optimum opening height from the ground, along with five geometrical variables: inlet diameter, throat diameter, outlet diameter, nozzle length, and diffuser length. A comprehensive test matrix is developed using design of experiments (DoE) to build an artificial neural network (ANN) model. This neural network is developed using computational fluid dynamics (CFD) simulations validated with experimental data. Subsequently, a gradient-based global optimization method fine-tunes the neural network and identifies optimal designs for various heights. The research concludes that nozzle and diffuser opening angles within the range of 19° ≤ ΦNoz ≤ 23°and 7.5° ≤ ΦDif ≤ 8.2°, respectively, result in the optimal converging-diverging ducted opening geometry. This optimal opening can yield a power density increase of 31.5 to 35.5 times when compared to freestream flow and 17.5 to 22.4 times in comparison to cylindrical openings, depending on the opening location along the building height.

Revamping Triboelectric Output by Deep Trap Construction.

High output performance is critical for building triboelectric nanogenerators (TENGs) for future multifunctional applications. Unfortunately, the high triboelectric charge dissipation rate has a significant negativeimpact on its electrical output performance. Herein, a newtribolayer is designed through introducing self-assembled molecules with large energy gaps on commercial PET fibric toform carrier deep traps, which improve charge retention while decreasing dissipation rates. The deep trap density of the PET increases by two orders of magnitude, resulting in an 86% reduction in the rate of charge dissipation and a significant increase in the charge density that can be accumulated on tribolayer during physical contact. The key explanation is that increasing the density of deep traps improves the dielectric's ability to store charges, making it more difficult for the triboelectric charges trapped by the tribolayer to escape from the deep traps, lowering the rate of charge dissipation. This TENG has a 1300% increase in output power density as a result of altering the deep trap density, demonstrating a significant improvement. This work describes a simple yetefficient method for building TENGs withultra-high electrical output and promotes their practical implementation in the sphere of the Internet of Things.

GMP/Al2O3/ZnO/PDMS thermal interface materials with anisotropic thermal conductivity and electrical insulation ability obtained by 3D‐printing method

AbstractDue to the continuous increase in power density and power consumption, thermal management has become a crucial issue in electronic devices like integrated circuits. Polymer‐based thermal conductive composites possess excellent thermal and mechanical properties, making them ideal materials for thermal management in the modern microelectronic industry. In this work, we present a combination of filler hybridization strategy and 3D‐printing technology to synergistically enhance the thermal conductivity of graphite microplatelets (GMP)/alumina (Al2O3)/zinc oxide (ZnO)/polydimethylsiloxane (PDMS) composite (o‐GAZP). When the content of GMP reaches 4.5 vol%, the 3D‐printed composite material exhibits a directional thermal conductivity of up to 4.51 W m−1 K−1. This value is significantly higher than the thermal conductivity of a randomly mixed GMP/Al2O3/ZnO/PDMS composite (1.98 W m−1 K−1). The remarkable thermal conductivity can be attributed to the anisotropic structural design, which benefits from the orientation of GMP and the creation of a multi‐scale dense structure through filler compounding. Additionally, the presence of Al2O3 and ZnO effectively separates the GMP particles, preventing the formation of electron transfer pathways and improving the electrical insulation performance of the composites. Furthermore, the impact of the anisotropic structural design on the thermal conductivity of the composites was verified through finite element simulation. This study demonstrates that constructing efficient thermally conductive and electrically insulating pathways by densely packing highly oriented two‐dimensional anisotropic graphite‐based fillers with uniformly dispersed thermally conductive and electrically insulating fillers is a simple and effective method to enhance the composites' thermal conductivity, electrical resistivity, and mechanical properties simultaneously. These findings hold great potential for various scalable thermal‐related applications. By implementing this approach, composites can exhibit excellent thermal conductivity, high electrical resistivity, and superior mechanical performance.

A New Concept of Direct Oil Cooling System for AFPM Machines, Numerical Analysis and Optimization

Given the strong growth of the electric drive industry, the automotive sector needs to increase the power density of its motors, leading to a size decrease and, consequently, to economic savings. The increase in power density brings with itself the consequence of increasing the Joule effect losses in the active conductors of the machine. For this reason, the problem of cooling turns out to be of utmost importance precisely because of its direct coupling with mechanical and electromagnetic design. This paper has the aim to perform a CFD analysis concerning the cooling system of a permanent magnet axial flux electric machine. The innovative cooling system studied is a direct one which takes advantage of oil to cool down the DC powered coils. The innovation brought by the present research lays in both the direct axial ejection and the use of oil as coolant. At the current state of art, the coolant flows tangentially and, moreover, water is usually employed instead of oil. The main aim of this analysis will be, after a validation of the numerical code by comparison of the literature data, to minimize the maximum temperature of the coil by means of the proper positioning of the nozzle.

Модификация наноструктурированного диоксида титана методом гидротермальной обработки для улучшения электрических параметров бета-вольтаических элементов

New technologies of microelectronics are emerging to reduce the size of devices and combine them into more compact ultra-low power systems. Betavoltaic power sources (BVPSs) can serve as power generators of such order. BVPSs consist of a combination of betavoltaic cells (BVCs) based on long-lived radioisotopes of beta radiation and semiconductor converters (SCs). One of the key tasks for increasing the power of BVC is the selection of SCs that can efficiently convert the energy of beta particles into electricity. Currently, semiconductor structures with a developed surface and a high band gap are considered to be perspective SCs. In present work, arrays of titanium dioxide nanopores (TiO2 NPs) synthesized by common electrochemical anodization was chosen as a SCs. These SCs were part of BVCs based on nickel-63 with an activity of ~ 10 Ci/g. TiO2 NPs with an amorphous structure in the composition of BVC demonstrated low electrical parameters. To increase them, we modified TiO2 NPs by the hydrothermal method in a solution of Sr(OH)2 with a concentration of 0.05 mol/l at various times. These experiments were carried out in order to convert TiO2 (anatase) into structure-like SrTiO3. We found that the electrical parameters of the SCs increased with the duration of the modification time. The best result was obtained in case of 3 h modification — the BVC generated a short circuit current 2,9 nA, open circuit voltage 0,8 V and had a maximum power 0,8 nW at 0,45 – 0,5 V. The obtained electrical parameters in combination with the miniature dimensions of the BVCs open up the potential possibility of creating a BVPS with an increased power density.

Fully Soft-Switched Buck–Boost Bridgeless PFC Converters With Single-Magnetic Core

This paper proposes new fully soft switched bridgeless buck-boost power factor correction converters using single magnetic core with capability of realizing positive or negative output voltages. Full ZVS operation is provided for the main switches independent of the load and grid voltage variations. Also, the proposed converters have common ground and single ended output which increase power density and alleviates common mode noise. The proposed converters operate under discontinuous conduction mode (DCM) to shape the input current inherently. A 120W, 100kHz laboratory prototype with negative output voltage is implemented to verify the theoretical analysis and the effectiveness of the proposed topologies. The results demonstrate efficiency of 96.2% and total harmonic distortion (THD) of 4% at full load condition.