Power Density Limits Research Articles

Detecting Visible to Near-Infrared II Light via CsPbBr3 Nanocrystals/Y6 Heterojunctions.

In the endeavor to develop advanced photodetectors (PDs) with superior performance, all-inorganic perovskites, recognized for their outstanding photoelectric properties, have emerged as highly promising materials. Due to their unique electronic structure and band characteristics, the majority of all-inorganic perovskite materials are not sensitive to near-infrared (NIR) light. Here, we demonstrate the fabrication of a high-performance broadband PD comprising CsPbBr3 perovskite NCs/Y6 planar heterojunctions. The incorporation of Y6 not only facilitates charge transfer from CsPbBr3 NCs to Y6 for enhancing photodetection performance under visible illumination but also broadens the absorption spectrum range of the whole device toward the NIR regime. As a result, the heterojunction PD exhibits a photo-to-dark-current ratio above 105, a dynamic range of 149.5 dB, and an impressive lowest detection limit of incident power density of 1.6 nW/cm2 under 505 nm illumination. In the NIR regime, where photon energy is below the bandgap of CsPbBr3, electron-hole pairs can still be produced in the Y6 layer even when illuminated at 1120 nm. Consequently, photodetection is uniquely possible in PDs that incorporate heterojunctions when the illumination wavelength is longer than 565 nm. At 850 nm, the heterojunction device is capable of detecting light with power densities as low as 1.3 μW/cm2 corresponding to a LDR of 99.8 dB. The exceptional performance is attributed to the creation of a heterojunction between CsPbBr3 NCs and Y6. These findings propose a novel approach for developing broadband PDs based on perovskite NC materials.

Graphene oxide-based nanofluidic system for power generation from salinity difference

In converting a salinity difference to the electrical power by using an ion-selective membrane, achieving a high-power density necessitates both a high ion permeability and ion selectivity of the membrane. However, meeting these two requirements often leads to the conflicting tradeoff in the membrane properties. In this study, we introduce a new mechanistic approach to meeting both requirements by combining an ultra-thin (<100 nm thickness) graphene oxide-based membrane for a high permeability with an asymmetric access area for a high ion selectivity, forming a new type of ionic-diode nanofluidic system. With a graphene oxide/silk fibroin composite membrane, a large power density of 2kW/m2 is achieved with 32% conversion efficiency under a 1000-fold salt concentration ratio. This approach can be utilized to overcome the low power density limitation with any ultra-thin membranes, and thereby it will provide a new route to utilize blue energy in a reliable and efficient way.

Single-Mode Segmented Cladding Chalcogenide Glass Fiber With Ultra-Large Mode Area

Small core size in conventional single mode step-indexed chalcogenide fiber could reduce the ability of mid-infrared (mid-IR) laser power delivery due to its limitation of power density. An effective way to solve the problem is to increase mode area with large core size, but this may degrade the beam quality. In this work, a novel mid-IR segmented cladding fiber (SCF) with leakage structure based on chalcogenide glasses was proposed to obtain large mode area, as well as single-mode condition. The leakage loss and effective mode area of the SCF was analyzed by optimizing the segment number <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> , duty cycle γ and core radius <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</i> . The results show that, when <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> =4, γ=75% and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</i> =33 μm, the mode area is more than 2000 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in the wavelength range of 3-10 μm and the loss ratio of high order modes (LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ) to fundamental mode (LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> ) is more than 300, indicating the SCF can achieve single-mode operation with a large core. Then, a mid-IR SCF was fabricated via an extrude-and-stack technique based on chalcogenide glasses for the first time. The minimum fiber loss is 3.1 dB/m at 8.6 μm, the bend loss is 3 dB when bend radius is 6 mm. Compared with that in the traditional step-index single-mode fiber, it was found that, the mode area in SCF can be increased over 15 times. All these results demonstrate the SCF possesses the potential of high-power mid-IR laser transmission.

(Invited) Recent Advances in Thermally Regenerative Batteries: A New Approach for Generating Electrical Power from Low-Grade Heat

Thermally regenerative flow batteries (TRBs) seek to tap into the unused terawatt-hours of low-grade heat that are currently being expelled from industrial plants and stationary power sources each year. Unlike typical flow batteries, TRBs can be recharged using thermal energy, therefore increasing grid efficiency by using an energy stream that is already widely available. This unique feature is accomplished through a thermally recoverable energy carrier that, when added or removed from an electrolyte, dramatically alters the standard electrode potential of an electrode reaction. To date, most TRBs use ammonia as the energy carrier, which lowers the standard electrode potential of their anode reaction by complexing with transition metal ions such as copper, silver, or zinc. Despite the early successes of TRBs relative to other emerging electrochemical technologies trying to harness low-grade thermal energy sources, they still lacked the energy efficiency and power densities needed to be economically viable. The first iterations of TRBs had peak power densities up to 3 mW cm-2 with competitive theoretical energy efficiencies (up to 1 %), but they suffered from extreme coulombic efficiency issues that limited realizable energy production values. Herein, we will discuss recent changes that have greatly improved the performance possible from these systems and discuss persistent challenges that remain to be solved. Coulombic inefficiencies were resolved by replacing unstable deposition-based reactions with all-aqueous alternatives that provided larger cell potentials and coulombic efficiencies for single metal and bimetallic-TRB systems. Electrolyte composition, operating temperature, and membrane transport all strongly influenced energy efficiency and power density limits from these new electrolyte chemistries. Peak power densities up to 100 mW cm-2 and theoretical energy efficiencies up to 12 % were identified through a preliminary survey of possible design choices. However, tradeoffs between attainable power density and energy efficiency limited cell performance values to a fraction of these values. Future work to better control diffusive transport without conductivity losses will be crucial for approaching theoretical battery performance limits.

High power density battery chargers with fast-charging utilizing heat storage

While wide bandgap semiconductor technology, such as gallium nitride, has considerably enhanced power density in mobile battery charger applications, the development of smaller, cost- and resource-effective systems is hindered by thermal constraints arising from miniaturized components and compact housings. This work proposes a transient thermal management system that dynamically adjusts converter output power according to thermal boundaries, utilizing latent and sensible heat storage to enable an initial boosted performance. An analytical and numerical sensitivity analysis of power density limits was conducted to evaluate the impact of thermal and electrical boundary conditions. A 40W hardware prototype of a quasi-resonant flyback converter with transient thermal management was realized using epoxy resin and phase change material filling. The findings show a 40% higher effective power density when charging a conventional 50Wh laptop battery, all within the same thermal boundaries as common operation at constant output power, with a power density measurement accuracy of 5.2%. The system was implemented using PI controller for inner component and surface temperature control. This novel approach to fast-charging highlights the optimization potential of current systems through converter heat storage utilization and provides valuable insights, including analytical and numerical models, for developing chargers capable of overcoming thermal barriers.

Interchangeable Biomass Fuels for Paper-Based Microfluidic Fuel Cells: Finding Their Power Density Limits.

Paper batteries are self-pumping emerging tools for powering portable analytical systems. These disposable energy converters must be low-cost and must achieve enough energy to power electronic devices. The challenge is reaching high energy while keeping the low cost. Here, for the first time, we report a paper-based microfluidic fuel cell (PμFC) equipped with Pt/C on a carbon paper (CP) anode and a metal-free CP cathode fed by biomass-derived fuels to deliver high power. The cells were engineered in a mixed-media configuration, where methanol, ethanol, ethylene glycol, or glycerol is electro-oxidized in an alkaline medium, while Na2S2O8 is reduced in an acidic medium. This strategy allows for optimizing each half-cell reaction independently. The colaminar channel of the cellulose paper was chemically investigated by mapping the composition, which reveals a majority of elements from the catholyte and anolyte on each respective side and a mixture of both at the interface, assuring the existing colaminar system. Moreover, the colaminar flow was studied by investigating the flow rate by considering recorded videos for the first time. All PμFCs show 150-200 s to build a stable colaminar flow, which matches the time to reach a stable open circuit voltage. The flow rate is similar for different concentrations of methanol and ethanol, but it decreases with the increase in ethylene glycol and glycerol concentrations, suggesting a longer residence time for the reactants. The cells perform differently for the different concentrations, and their limiting power densities are composed of a balance among anode poisoning, residence time, and viscosity of the liquids. The sustainable PμFCs can be interchangeably fed by the four biomass-derived fuels to deliver ∼2.2-3.9 mW cm-2. This allows choosing the proper fuel due to their availability. The unprecedented PμFC fed by ethylene glycol delivered 6.76 mW cm-2, which is the benchmark output power for a paper battery fed by alcohol.

Phosphonium-based deep eutectic solvents: Physicochemical properties and application in Zn-air battery

Electrolytes play a significant role in metal-air batteries and influence the battery's performance. Deep eutectic solvents (DESs) are viable and attractive candidates as high-performance electrolytes in batteries. This study investigated the temperature-dependent physicochemical properties of several phosphonium-based DESs such as the freezing point, density, viscosity, surface tension, and conductivity. The viscosity of the DES electrolyte is correlated as a function of molar conductivity using Walden's rule. Subsequently, the electrochemical characterizations of a Zn-air battery with the DES electrolyte, such as the cell voltage, power density, and current limit are studied. The electrochemical and physicochemical profiles of the phosphonium-based DESs possess dependence on the salt-to-hydrogen bond donor (HBD) molar ratio and appear viable for further exploration in metal-air battery applications. To the best of our knowledge, this is the first study that investigates the efficacy of the phosphonium-based DESs as the electrolyte in Zn-air batteries.

Eye Shielding against Electromagnetic Radiation: Optimal Design Using a Reduced Model of the Head

This article presents the design process of a structure that shields the electromagnetic field from the fifth-generation transmitter operating in the 3.5 GHz band. The purpose of this project is the limitation of power density in the eye region. For this reason, the structure is made of conducting wires forming a grid that is semitransparent to the light. The design was performed using computer simulations with a finite-difference time-domain method and an evolutionary-based optimization methodology. A simplified model of the face and eyes was developed to reduce the amount of time needed for the simulation. The construction of the shielding structure presented here can be easily fabricated in the form of protective goggles. The results of the computer simulations show that the power density in the eye region can be reduced by almost seven times compared with the unshielded case.

Developments of stitched monolithic pixel sensors towards the ALICE ITS3

The ALICE collaboration is pursuing the development of a novel and considerably improved vertexing detector called ITS3, to replace the three innermost layers of the Inner Tracker System during the LHC Long Shutdown 3. The primary goals are to reduce the material budget to the unprecedented value of 0.05% X0 per layer, and to place the first layer at a radial distance of 18 mm from the interaction point. These features will boost the impact parameter resolution by a factor two over all momenta and drastically enhance the tracking efficiency at low transverse momentum.The new detector will consist of true cylindrical layers. Each half-cylinder is based on curved wafer-scale monolithic pixel sensors. The bending radii are 18, 24 and 30 mm, and the length of the sensors in the beam direction is 27 cm. The sensors will be produced using a commercial 65 nm CMOS Imaging technology and a recent technique called stitching. This allows to manufacture chips reaching the dimensions of 27 cm × 9 cm on silicon wafers of 300 mm diameter. The sensors will be thinned down to 50 µm or below. The ITS3 concept foresees cooling by air flow, ultra-light carbon foam support elements and no flexible printed circuits in the active area. This demands a power density limit of 20 mW/cm2 for the sensor, and the need to distribute supply and transfer data over the entire sensors towards circuits located at the short edges of the chip.This contribution summarises the status of the microelectronic developments and presents selected results from the characterisation of the first prototype chips. Furthermore, it describes the ongoing efforts on the design of a first wafer-scale stitched sensor prototype, the MOSS (Monolithic Stitched Sensor) chip.

Computation of Absorbed Power Densities in High-Resolution Head Models by Considering Skin Thickness in Quasi-Millimeter and Millimeter Wave Bands

The fifth-generation wireless communications system has been increasingly deployed by telecommunication companies worldwide. This system uses a high-frequency band ranging from 24 GHz to 28 GHz. However, the number of studies assessing the human protection from the electromagnetic fields is limited in this frequency band. In addition, two main international bodies—the International Commission on Non-Ionizing Radiation Protection and IEEE—have revised their guidelines and standard in 2020 and 2019, respectively. One primary change is the exposure metric and corresponding exposure limit at frequencies >6 GHz because the penetration depth of the electromagnetic waves in biological tissues is 1 cm or less for these frequencies. Therefore, modeling of the skin and subcutaneous tissues is important. This study evaluated the total absorbed power (TAP), the absorbed power density (APD), and variations in APD owing to skin thickness in seven types of realistic human head models with different skin thicknesses. Our results showed that the model without surface smoothing resulted in higher TAP than the model with smoothing. The amount of the TAP change in frequency domain in the model with realistically varied skin thickness was less than that in the model with uniform skin thickness because of the suppression of strong standing waves. The maximum variations in the APD, averaging over 4 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> or 1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with respect to skin thickness, were approximately 20% and 10%, respectively. For the limit of incident power density, APDs were below the guideline. These results will be useful for future revisions of international guidelines.

Looking Beyond 0 and 1: Principles and Technology of Multi-Valued Logic Devices.

Ever since the invention of solid-state transistors, binary devices have dominated the electronics industry. Although the binary technology links the natural property of devices to be in the ON or OFF state with two logic levels, it provides the least possible information content per interconnect. Multi-valued logic (MVL) has long been considered as a means of improving the computation efficiency and reducing the power consumption of modern chips. In view of the power density limits of the conventional complementary metal-oxide-semiconductor technology, MVL technologies have recently gained even more attention, and various MVL unit devices based on conventional and emerging materials have been proposed. Herein, the recentachievements toward the development of compact MVL unit devices are reviewed. First, basic principles of MVL technologies are introduced by describing methods of obtaining multiple logic states and discussing radix-related aspects of MVL computation. Next, MVL unit devices are classified and overviewed with emphasis on principles of operation, technologies, and applications. Finally, acomparative discussion of strengths and weaknesses is provided for each class of MVL devices, and the review concludes with the outlook for the MVL field.

Manipulation of Anode Nanostructure and Composition By Glancing Angle Deposition for Thin-Film Solid Oxide Fuel Cells

Co-sputtering is a simple yet effective technique for fabricating a thin film of composite materials and different compositions by adjusting the electrical power of each sputtering target. However, practical issues arise when depositing cermet materials such as Ni-YSZ and Ni-GDC because of the contrasting characteristics of metal and ceramic sputtering targets. For example, the surface binding energy of GDC is significantly higher than that of Ni, resulting in a considerably lower sputtering yield of GDC. The difference in sputtering yield is further exacerbated by the low power density limit of the GDC target, which is set by its unfavorable material properties such as brittleness and low thermal conductivity. In contrast, due to its magnetic property, Ni requires sufficiently high sputtering power during magnetron sputtering.This work combines co-sputtering with advanced sputtering techniques such as glancing angle deposition (GLAD) and oblique angle deposition (OAD) to fabricate otherwise unobtainable Ni-GDC anode microstructure with various compositions. Reduced flux capture area of Ni caused by the high incident angle of GLAD allowed control of thin-film compositions, and optimal composition was determined based on fuel cell performance and electrochemical impedance spectroscopy (EIS) analysis. A sufficient amount of GDC was necessary to expand the triple-phase boundary (TPB) and suppress the thermal agglomeration of highly mobile Ni.The effect of electrode nanostructure on fuel cell performance was also investigated. The ballistic shadowing effect during OAD was utilized to produce thin-film electrodes with various porosities. With the increase of the deposition angle, the porosity increased, whereas the in-plane electrical conductivity decreased due to the reduced density. The columnar structure was also manipulated by managing the substrate position through azimuthal rotation. As a result, various columnar structures such as vertical posts, slanted posts, and zig-zag were fabricated, and the optimal microstructure was determined via electrochemical examinations.

Design of a 120 W Electromagnetic Shock Absorber for Motorcycle Applications

Based on the shock absorber size and power and power density limitations in motorcycle application, a linear permanent magnet machine for a regenerative suspension system that recovers the kinetic energy originating from shock absorber vibration is investigated. To achieve the target power of 120 W, several design parameters were investigated. The eight-slot eight-pole combination was used due to its high power density. A hybrid permanent magnet structure was implemented which was a combination of a classical Halbach array and iron spacers. In addition, the dimensions of the permanent magnet, and stator inner radius were parametrically studied to enhance the air-gap flux density and coil volume, which are the main factors affecting performance. The detailed design generated 124 W of average power under the rated condition, assuming a vibration speed of 0.157 m/s. Despite the satisfaction of the output power and power density, the large magnetic force caused by the interaction between the iron core and permanent magnet is the main drawback of this design, which has a negative impact on driving safety and comfort. To commercialize the suggested device, additional studies will focus on size, electromagnetic reduction, as well as road test performance.

Quantitative evaluation of the supercontinuum laser eye dazzling effect: in vivo experimental research

To quantitatively evaluate the dazzling effect of each spectrum band of the supercontinuum laser, we conducted experimental research to explore the safety and dazzling of animal eyes. Under the condition of dark adaptation, the rabbit eyes were irradiated with different power densities and spectral bands by frontal incident mode for 0.25 s, which was repeated ten times. The fundus of the rabbit eyes was examined using an ophthalmoscope, and the upper limit of safe power density was explored. Rabbit eyes were irradiated with different doses of dazzling light for 0.1 s. Visual electrophysiological signals were collected dynamically, and the recovery time of the electroretinogram (ERG)-b wave amplitude of the rabbit eyes was recorded and analyzed after laser irradiation. When the power density was 8.0 mW cm−2 in visible spectrum (vs.), the recovery time of the ERG-b wave in the rabbit eye was 4.11 ± 0.67 s. When the power density was 12.0 mW cm−2 in the full spectrum (FS), the recovery time of the ERG-b wave in the rabbit eye was 4.16 ± 0.55 s. The recovery time of the ERG-b wave was 4.50 ± 0.94 s at a power density of 4.6 mW cm−2 in FS-1 and 3.81 ± 0.11 s at a power density of 5.0 mW cm−2 in the FS-2. When the power density was 628.00 mW cm−2 in infrared spectrum (IS), the recovery time of the ERG-b wave was only 0.84 ± 0.09 s. The reference values for the upper limit of the safe irradiation power density of the supercontinuum laser are set as follows: 25.2 mW cm−2 in vs., 118.4 mW cm−2 in IS and 105.0 mW cm−2 in FS. The vs., FS, FS-1 and FS-2 of the supercontinuum laser had a good dazzling effect on rabbit eyes, and the dazzling effect was enhanced with increasing radiation power density, but the IS had little dazzling effect.

Efficient Low-Grade Heat Conversion and Storage with an Activity-Regulated Redox Flow Cell via a Thermally Regenerative Electrochemical Cycle.

Efficient and cost-effective technologies are highly desired to convert the tremendous amount of low-grade waste heat to electricity. Although the thermally regenerative electrochemical cycle (TREC) has attracted increasing attention recently, the unsatisfactory thermal-to-electrical conversion efficiency and low power density limit its practical applications. In this work, a thermosensitive Nernstian-potential-driven strategy in the TREC system is demonstrated to boost its temperature coefficient, power density, and thermoelectric conversion efficiency by rationally regulating the activities of redox couples at different temperatures. With a Zn anode and [Fe(CN)6 ]4-/3- -guanidinium as the catholyte, the TREC flow cell presents an unprecedented average temperature coefficient of -3.28mV K-1 , and achieves an absolute thermoelectric efficiency of 25.1% and apparent thermoelectric efficiency of 14.9% relative to the Carnot efficiency in the temperature range of 25-50°C at 1mA cm-2 . In addition, a thermoelectric power density of 1.98mW m-2 K-2 is demonstrated, which is more than 7 times the highest power density of reported TREC systems. This activity regulation strategy can inspire research into high-efficiency and high-power TREC devices for practical low-grade heat harnessing.

Study of electromagnetic radiation from mobile towers near schools and health centers in the Suhar city

Mobile information access and communication has become an important segment of modern life. At the same time, people wellbeing is taken into consideration for the safe use of technology. As per Bio-Initiative Report, the existing standards are to be relooked for proper healthy environment. Different countries are adopting different criteria for the limit of the radiation power density within the International Commission on Non-ionizing Radiation Protection limits. For the purpose, administrators and regulators in Sultanate of Oman are taking utmost care according to the guidelines setup by International and National agencies. With the focus to have awareness about the technical requirements to protect the health of the people, especially (kids, pregnant women and patients), the study was done to measure the power density radiated by mobile towers near schools and health centers within Suhar using the “Spectran” handheld analyzer for GSM 900 MHz range with maximum distance 250 meters within the study area. It was found that the measured power density decreases as the distance of point of measurement is increased. On all the measurement points the power density was well below the recommended range from ICNIRP infers the safe use the communication devices under the present conditions.

71‐3: Static Laser Phosphor for Projectors with Rotating Tilted Mirror

Laser excited phosphor has much higher brightness than that of LEDs and are suitable for many high power, low etendue applications. One of the major obstacles is heat sinking of the phosphor in high power applications with the phosphor material coated onto a rotating wheel. This paper presents a static phosphor plate system in which the phosphor plate is stationary and can be attached to traditional heat sinks for efficient removal of heat at high power, which cannot be achieved easily when the phosphor material is on a rotating wheel. The highest equivalent power density of estimated from 300 W to 600 W per sq. mm has been achieved, which is over 6 times higher than the original limit of the phosphor material. It is also found that the thickness of the phosphor plays an important role in the power density limits. Thinner phosphor plates are being investigated for even higher power operations with expected high limits.

Dynamic and Steady Model Development of Two-Chamber Batch Microbial Fuel Cell (MFC)

As an alternative source of renewable energy that has piqued researchers’ interest, Microbial Fuel Cell’s (MFC) limitation of low power density requires further development. Various factors affect the performance, but performing all will be costly and time-consuming. Through a combination of dynamic and steady-state mathematical model modified from past research, effect of microbe types towards dynamic biofilm formation and stead-state OCV can be observed, followed by steady-state simulation to determine maximum power density and its’ corresponding voltage. Similarity with previous research has been observed, with maximum OCV of 838.93 mV achieved by heterotrophic biomass in 75-100 hours with biofilm thickness of 2.087 x 10-4 m, while generating maximum power density of 2050.12 mW//m2 and voltage of 408.16 mV. Lowest OCV value of 838.76 mV was observed in C. sporogenes in 450-475 hours with a biofilm thickness of 2.079 x 10-4 m, while the lowest value of maximum power density was observed in anaerobic microbial communities at 8.48 mW/m2 with voltage of 90.43 mV. Furthermore, it has been observed that variations with higher and lower results in higher stead-state OCV in the shortest amount of time, while increasing power density and its’ corresponding voltage. @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-536869121 1107305727 33554432 0 415 0;}@font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-469750017 -1073732485 9 0 511 0;}p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman",serif; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-US;}.MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt; font-family:"Calibri",sans-serif; mso-ascii-font-family:Calibri; mso-fareast-font-family:Calibri; mso-hansi-font-family:Calibri; mso-ansi-language:IN; mso-fareast-language:IN;}div.WordSection1 {page:WordSection1;}

Conceptual design of gas cartridge loop components for the Versatile Test Reactor

In continuation of the Gas Cartridge Loop (GCL) development for the Versatile Test Reactor (VTR), General Atomics-Electromagnetic Systems (GA-EMS) conducted conceptual design studies of the GCL major components such as test articles, electromagnetic (EM) motor, heating elements, instrumentation and control (I&C), and pressure vessel. While the pre-conceptual design used a single test article and estimated the heating and cooling requirements of the GCL, the conceptual design used three test articles, with a reduced height by a factor of two, to enhance better experimental capabilities. The thermal-fluid analysis determined the performance requirements of the motor and heater, and confirmed the gas-cooled fast reactor (GFR) experimental conditions are achieved with the total test article power of 16.5 kW compared with 11 kW of the pre-conceptual design.The conceptual design of the motor is a four-pole three-phase high temperature induction motor. The motor and heater were designed with a 30% margin to the required power. Investigation was conducted on different heating element technologies, such as Nichrome, Kanthal, MoSi2, and SiC, for their temperature and power density limits. The conceptual design of the heater focused on material selection for the metal sheath and the heater rod arrangements. I&C design elaborated and clarified the conceptual design by defining the control logic and required number of lines for the redundancy and availability of the sensors and detectors of the GCL. Mechanical design analysis of the GCL pressure vessel conducted during the pre-conceptual design is still valid for the design limits of the stress and strain.

Research on Active Thermal Control: Actual Status and Future Trends

The trend toward integrating power electronic converters and pushing their device utilization toward physical limits puts the spotlight on the junction temperature of the devices. The physical limits of power density are directly tied to the maximum junction temperature and junction temperature cycles that are considered as the root cause of the aging and, finally, the failure of the device. Therefore, manipulating the junction temperature with smart control algorithms is a promising method to enhance the power density and the lifetime of future converter systems. To address these opportunities, recent research proposed methods that increase the overload capability, reduce thermal cycles, balance thermal stress, and share thermal loading of power converters. This article systematically analyzes the fundamental principle and the key objective of these methods and discusses their limitations and potential. Based on this discussion, it highlights important challenges, such as thermal state variable extraction, nonlinear aging, and minimizing the impact on system operation. These challenges must be addressed by future research to make active thermal control a key enabler of a smart power converter with superior power density and reliability.