Parasitic Losses Research Articles

A physics-based compact model of thermal resistance in RRAMs

In this paper, we present a physics-based compact model of thermal resistance in Resistive Random-Access Memory (RRAM) devices considering (a) thermal properties of electrode materials, (b) temperature-induced variations in material thermal conductivity, and (c) parasitic heat losses through the oxide surrounding the filament. Fully coupled numerical simulation data obtained from the self-consistent solution of the drift-diffusion equation (for vacancy migration), carrier continuity equation (for electronic conduction), and the Fourier heat diffusion equation (accounting for electro-thermal heating) has been used for developing and validating the proposed model. Excellent agreement is observed between the model and the numerical simulation results. The proposed model is validated with experimentally measured conductive filament temperature obtained from two different temperature sensing methods. Finally, we present a modeling framework to estimate the potential thermal-cross talk in RRAM crossbar arrays. Our results illustrate that a power-dependent thermal resistance model significantly improves the accuracy in estimating the electro-thermal effects in RRAMs.

Inhomogeneities in the Catholyte Channel Limit the Upscaling of CO2 Flow Electrolysers.

The use of gas diffusion electrodes that supply gaseous CO2 directly to the catalyst layer has greatly improved the performance of electrochemical CO2 conversion. However, reports of high current densities and Faradaic efficiencies primarily come from small lab scale electrolysers. Such electrolysers typically have a geometric area of 5 cm2, while an industrial electrolyser would require an area closer to 1 m2. The difference in scales means that many limitations that manifest only for larger electrolysers are not captured in lab scale setups. We develop a 2D computational model of both a lab scale and upscaled CO2 electrolyser to determine performance limitations at larger scales and how they compare to the performance limitations observed at the lab scale. We find that for the same current density larger electrolysers exhibit much greater reaction and local environment inhomogeneity. Increasing catalyst layer pH and widening concentration boundary layers of the KHCO3 buffer in the electrolyte channel lead to higher activation overpotential and increased parasitic loss of reactant CO2 to the electrolyte solution. We show that a variable catalyst loading along the direction of the flow channel may improve the economics of a large scale CO2 electrolyser.

Predicting primate-parasite associations using exponential random graph models.

Ecological associations between hosts and parasites are influenced by host exposure and susceptibility to parasites, and by parasite traits, such as transmission mode. Advances in network analysis allow us to answer questions about the causes and consequences of traits in ecological networks in ways that could not be addressed in the past. We used a network-based framework (exponential random graph models or ERGMs) to investigate the biogeographic, phylogenetic and ecological characteristics of hosts and parasites that affect the probability of interactions among nonhuman primates and their parasites. Parasites included arthropods, bacteria, fungi, protozoa, viruses and helminths. We investigated existing hypotheses, along with new predictors and an expanded host-parasite database that included 213 primate nodes, 763 parasite nodes and 2319 edges among them. Analyses also investigated phylogenetic relatedness, sampling effort and spatial overlap among hosts. In addition to supporting some previous findings, our ERGM approach demonstrated that more threatened hosts had fewer parasites, and notably, that this effect was independent of hosts also having a smaller geographic range. Despite having fewer parasites, threatened host species shared more parasites with other hosts, consistent with loss of specialist parasites and threat arising from generalist parasites that can be maintained in other, non-threatened hosts. Viruses, protozoa and helminths had broader host ranges than bacteria, or fungi, and parasites that infect non-primates had a higher probability of infecting more primate species. The value of the ERGM approach for investigating the processes structing host-parasite networks provided a more complete view on the biogeographic, phylogenetic and ecological traits that influence parasite species richness and parasite sharing among hosts. The results supported some previous analyses and revealed new associations that warrant future research, thus revealing how hosts and parasites interact to form ecological networks.

Fuel efficiency and emissions reduction of hydroxy added gasoline fuel using HydroBoost technology

In the present work, using the HydroBoost technology, performance and emission characteristics of HHO added Gasoline is investigated. HydroBoost technology offers longevity to cell and increases the efficiency as it requires less power to break the bonds of water. Achieving good emission characteristics using HydroBoost technology is still unexplored. In the present work, following the EPA protocols, a comprehensive analysis of Total Hydrocarbon (THC), Methane (CH4), NOx, CO2, MPG emissions in four phases is performed. It is shown that harmful gas emissions are reduced in HHO added Gasoline in comparison to only Gasoline fuel. The stoichiometric air-fuel mixture has been achieved in the present work. BSFC (Brake Specific Fuel Consumption) is reduced by up to 11% and the overall emissions of HHO added gasoline are reduced by up to 13% for CO2, up to 72% for Total Hydrocarbons, up to 69% for Methane, up to 48% for NOx in relation to bare Gasoline fuel. The present technology enables Hydroxy gas to be produced on board the IC vehicle without creating an undesirable amount of parasitic loss or hazard, which can be immediately deployed to lower both BSFC and emissions including greenhouse gasses such as CO2.

Boost the Efficiency of Cu2ZnSn(S,Se)4 Solar Cell by Using Mn2+‐Induced Ultrathin CdS Buffer Layer

In this article, the efficiency of CZTSSe solar cell is improved by adding manganese chloride in the deposition solution of the CdS buffer layer. The mechanisms behind the experimental results are investigated. On one hand, the MnCl2 can facilitate the deposition of an ultrathin (≈10 nm) CdS buffer layer. The decreased thickness of the buffer layer can reduce the parasitic absorption loss of the solar cell. As the result, the short‐circuit current density of the solar cell is increased. On the other hand, the Mn2+ in the deposition solution can diffuse into the CZTSSe layer during the deposition of the buffer layer. The incorporation of Mn in CZTSSe would decrease the acceptor level of CZTSSe, reduce the defects at the CZTSSe/CdS interface, and increase the activation energy for the main recombination path in CZTSSe solar cell. These can lead to the reduction of the carrier recombination in the depletion region of the solar cell. As the result, the open‐circuit voltage of CZTSSe solar cell is improved. By using the ultrathin CdS buffer layers, the efficiency of CZTSSe solar cell is improved from 10.0% to 12.0% (active area efficiency).

Variation in Chloroplast Genome Size: Biological Phenomena and Technological Artifacts.

The development of bioinformatic solutions is guided by biological knowledge of the subject. In some cases, we use unambiguous biological models, while in others we rely on assumptions. A commonly used assumption for genomes is that related species have similar genome sequences. This is even more obvious in the case of chloroplast genomes due to their slow evolution. We investigated whether the lengths of complete chloroplast sequences are closely related to the taxonomic proximity of the species. The study was performed using all available RefSeq sequences from the asterid and rosid clades. In general, chloroplast length distributions are narrow at both the family and genus levels. In addition, clear biological explanations have already been reported for families and genera that exhibit particularly wide distributions. The main factors responsible for the length variations are parasitic life forms, IR loss, IR expansions and contractions, and polyphyly. However, the presence of outliers in the distribution at the genus level is a strong indication of possible inaccuracies in sequence assembly.

Active terahertz beam steering based on mechanical deformation of liquid crystal elastomer metasurface

Active metasurfaces are emerging as the core of next-generation optical devices with their tunable optical responses and flat-compact topography. Especially for the terahertz band, active metasurfaces have been developed as fascinating devices for optical chopping and compressive sensing imaging. However, performance regulation by changing the dielectric parameters of the integrated functional materials exhibits severe limitations and parasitic losses. Here, we introduce a C-shape-split-ring-based phase discontinuity metasurface with liquid crystal elastomer as the substrate for infrared modulation of terahertz wavefront. Line-focused infrared light is applied to manipulate the deflection of the liquid crystal elastomer substrate, enabling controllable and broadband wavefront steering with a maximum output angle change of 22° at 0.68 THz. Heating as another control method is also investigated and compared with infrared control. We further demonstrate the performance of liquid crystal elastomer metasurface as a beam steerer, frequency modulator, and tunable beam splitter, which are highly desired in terahertz wireless communication and imaging systems. The proposed scheme demonstrates the promising prospects of mechanically deformable metasurfaces, thereby paving the path for the development of reconfigurable metasurfaces.

Design and Implementation of Hybrid DC-DC Converter: A Review

The advancement in Power Management Integrated Circuit (PMIC) has driven the DC-DC conversion technology into a System-on-Chip (SoC) solutions, leveraging CMOS technology scaling from 180nm to 22nm and on-chip passive element integration. Concurrently, as the applications demand smaller form factor solution towards device portability with optimized power qualities, switched-capacitor-inductor hybrid architectures with fully-integrated passives have become a popular choice for a compact and high efficiency converter solution, in contrast to bulky and discrete component based alternatives. This article reviews the latest advancements in hybrid dc-dc topologies, specifically for low-power applications to address the downsides such as charge sharing loss, high current ripple, limited conversion ratio, low power density and efficiency. An overview of capacitor and inductor technology is discussed in terms of on-chip parasitic losses, and miniaturization. A comprehensive comparison in the state-of-the-art hybrid dc-dc converter work is tabulated with power density and efficiency as the primary performance metrics, highlighting their operability in low-power applications. Moreover, a discussion is included with quantified benchmarks to justify the viability of converters, along with the future recommendation of realizing ultra-high switching frequency for smaller footprint inductor and design approach to resolve the current tradeoff bottlenecks.

Multi-objective optimization of an air cooling battery thermal management system considering battery degradation and parasitic power loss

The battery thermal management system (BTMS) can effectively ensure that the batteries work in a safe temperature range and solve the problems caused by high temperature. This paper investigates an air cooling BTMS with 32 cylindrical lithium-ion batteries (LIBs). Previous BTMS studies pay little attention to cost, this work focuses on the economic cost to address the cost problem caused by the parasitic power consumption of BTMS. First, the battery degradation model is established, and the cycle life of the battery is determined through capacity loss. Second, the computational fluid dynamics (CFD) simulation is used to study the influence of design parameters on the maximum temperature (MT) of the battery module and the pressure drop. Then, this study proposes to use cyclical cost (including battery cycle life and parasitic power loss) to evaluate the economy. The MT and cyclical cost are simultaneously considered as the optimization objectives to form an optimization model via the surrogate model method. Finally, two multi-objective optimization algorithms are used to drive the optimization process. The results suggest that the MT drops from 314.58 K to 314.22 K, while the cyclical cost drops from 0.92 €/cycle to 0.85 €/cycle, a reduction of 7.6 %. The developed method could improve the economy while ensuring the heat dissipation performance of the battery, which provides guidance for the design of BTMS to meet the needs of consumers.

Parasitic Capacitance Associated With Inductive Sensors Used in MIT Imaging

Magnetic induction tomography (MIT) has recently been accomplished using a single inductive sensor, but under the assumption that it behaves as an ideal inductor. When performing a scan with a sensing coil that typically consists of a collection of concentric circular printed circuit board (PCB) copper traces connected in series, small amounts of parasitic capacitance arise that contribute to measured tank circuit loss. Results of this work quantify the magnitude of parasitic capacitance and associated losses. For current inductive sensors, capacitance-related loss is shown to diminish considerably when the coil is positioned more than ~2 cm from a target boundary. Recognizing that single-coil MIT scans generally position the coil within 2 cm of a target boundary, a correction is proposed, which enables a more accurate measurement of true inductive loss. Previously published scan data over agarose phantoms are then reexamined to show the negative impact on imaging fidelity that results when capacitance-related losses are ignored. Image comparisons are made using full 3-D image reconstruction, demonstrating that failure to compensate for parasitic capacitance loss can degrade image fidelity.

Piston Compression Ring Elastodynamics and Ring–Liner Elastohydrodynamic Lubrication Correlation Analysis

Friction loss in an internal combustion engine largely depends on elastohydrodynamic lubrication. The piston compression ring is a contributor to such parasitic losses in the piston subsystem. The complex elastodynamics of the ring are responsible for the transient and regime-altering film that affects the elastohydrodynamic lubrication of the ring liner contact conjunction. The current paper will discuss the ring radial, lateral deformation, and axial twist, and its effect on the film profile of the compression ring and its subsequent effect on tribological characteristics like elastohydrodynamic pressure, friction, and lubricant. A finite difference technique is used to solve the elastohydrodynamic issue of elastodynamic piston compression by introducing the elastodynamically influenced film thickness into the lubrication model. The results show that consideration of the elastodynamics predicts a 23.53% reduction in friction power loss in the power stroke due to the elastodynamic ring compared to the rigid ring. The elastodynamic effect improves the lubricant oil flow into the conjunction. A finite element simulation predicts a von-Mises stress of 0.414 N/mm2, and a maximum deformation of 0.513 µm at the core and coating interface is observed at the ring–ring groove contact. The sustainability of EHL in this case largely depends on the ring–liner elastodynamics.

Observation and analysis of lower-hybrid-current-drive density limit in EAST

Lower hybrid current drive (LHCD) experiments with line-averaged density up to ∼5.1 × 1019 m−3 were performed in EAST L-mode plasmas. When the line-averaged density rises above a critical value, the hard x-ray (HXR) emission falls to the noise level, indicating that the LHCD density limit is encountered. The experimental results show that the LHCD density limit can be increased with higher wave source frequency (f 0) and higher magnetic field (B t). Although a higher LHCD density limit is obtained by a higher magnetic field for both 2.45 GHz and 4.6 GHz waves, the results show a stronger dependence on the magnetic field for the 4.6 GHz case. Analysis suggests that, for normal operation with a relatively low magnetic field (1.6 T ⩽ B t ⩽ 2.5 T) on EAST, the dominant mechanisms responsible for the LHCD density limit are different between the 2.45 GHz and 4.6 GHz waves. The wave accessibility plays a more significant role during 4.6 GHz LHCD experiments, while parasitic losses due to parametric decay instability (PDIs) dominate the accessibility issue in the 2.45 GHz case. Collisional loss in the scrape-off layer (SOL) may explain the 4.6 GHz result when combined with the accessibility limit at high density and low temperature.

Organic Solar Cells Improved by Optically Resonant Silicon Nanoparticles.

Silicon nanophotonics has become a versatile platform for optics and optoelectronics. For example, strong light localization at the nanoscale and lack of parasitic losses in infrared and visible spectral ranges make resonant silicon nanoparticles a prospect for improvement in such rapidly developing fields as photovoltaics. Here, we employed optically resonant silicon nanoparticles produced by laser ablation for boosting the power conversion efficiency of organic solar cells. Namely, we created colloidal solutions of spherical nanoparticles with a range of diameters (80-240 nm) in different solvents. We tested how the nanoparticles' position in the device, their concentration, silicon doping, and method of deposition affected the final device efficiency. The best conditions optimization resulted in an efficiency improvement from 6% up to 7.5%, which correlated with numerical simulations of nanoparticles' optical properties. The developed low-cost approach paves the way toward highly efficient and stable solution-processable solar cells.

Increasing the efficiency of perovskite solar cells using Cs4CuSb2Cl12 quantum dots as an interface layer: A numerical study

Recently, the advantages of perovskite solar cells (PSCs) and a significant increase in power conversion efficiency (PCE) have played an essential role in the preference for these materials. Although different methods are used to increase PCE and reduce losses at the interfaces in PSCs, placing a new layer between the absorber/hole transfer layer (HTL) or between the absorber/electron transfer layer (ETL) stands out as one of the most common methods. In this study, considering stability, sustainability, mobility, and non-toxicity, Cs4CuSb2Cl12 (CCSC) perovskite quantum dots (PQDs) were preferred as the interface layer between absorber and HTL in CsPbI3 and formamidinium lead iodide (FAPI)-based PSC devices. While SnO2, Cu2O, and nickel were used as ETL, HTL, and back contact, respectively, CsPbI3 and FAPI perovskites were utilized as absorber materials separately. Simulations were conducted on Solar Cell Capacitance Simulator (SCAPS-1D) software and the current density (J) and voltage characteristics were compared. By choosing different interface layer thicknesses, different radiative recombination coefficients (RRCs), and different defect sites, the cell efficiency of the PQD interlayer solar cells were simulated. Simulations were also carried out using different series resistance (Rs) and different shunt resistance (Rsh) values to show the effect of parasitic losses on cell efficiency, and it was observed that device efficiency increased where Rs was low and Rsh was high. In addition, in FAPI-based structure, with the addition of a PQD layer between the absorber and HTL, it was observed that the short circuit current density increased from 17.6 mA/cm2 to 25.67 mA/cm2, while the cell efficiency increased by 30%. Furthermore, according to the results obtained using CsPbI3 as an absorber, adding a PQD layer between CsPbI3 and HTL increased the short circuit current density from 17.8 mA/cm2 to 20.7 mA/cm2 and cell efficiency by 16%. To sum up, these simulation results demonstrate that inserting a PQD layer between the absorber and HTL significantly enhances the efficiency and charge carrier capacity of solar cells.

Stretchable thermoelectric generators with enhanced output by infrared reflection for wearable application

Flexible thermoelectric generators can directly convert body heat into electricity to power wearable electronics, which is recognized as a potential candidate for durable energy supply. Nevertheless, the parasitic heat loss and inadequate waterproofing have greatly limited its practical application. Here we propose a compliant engineering solution for encapsulated thermoelectric generators that ensures sufficient alignment of thermal gradient based on infrared reflection effect, which realized both the increased infrared radiation insulation at hot end and the reduced radiation heating of cold end. It contributes to a remarkable increase in temperature difference as compared to the unencapsulated one when subjected to a same heat source, presenting up to ∼35% increase in voltage output. Owing to waterproof encapsulation, this TE wristband is reliable in a variety of real-life activities such as running and swimming. Moreover, the design concepts of thermoelectric wristband described here can bring new inspiration for realizing body energy harvesting.

LPT6510 development up to flight model

The LPT6510 is a compact integral pulse-tube cryocooler for 50–120 K applications, with a design derived from the Thales Cryogenics MPTC compressor developed under ESA TRP and the Absolut System SSC80 pulse-tube.An update will be given on tests and development performed on the LPT6510 cooler, including test results up to TRL6, additional work done towards the build of flight coolers in the frame of the TRISHNA project, and planned future work.Detailed cryogenic performance results will be shown over the entire operational envelope, the environmental test campaign will be highlighted, and specific aspects such as off-state parasitic losses and induced vibrations will be discussed.

Dopant‐free passivating contacts for crystalline silicon solar cells: Progress and prospects

AbstractThe evolution of the contact scheme has driven the technology revolution of crystalline silicon (c‐Si) solar cells. The state‐of‐the‐art high‐efficiency c‐Si solar cells such as silicon heterojunction (SHJ) and tunnel oxide passivated contact (TOPCon) solar cells are featured with passivating contacts based on doped Si thin films, which induce parasitic optical absorption loss and require capital‐intensive deposition processes involving flammable and toxic gasses. A promising solution to tackle this problem is to employ dopant‐free passivating contact, involving the use of transparent and cost‐effective wide band gap materials. In this review, we first introduce the dopant‐free passivating contact, from carrier transport mechanisms, material classification to evaluation methods. Then we focus on the advances in different strategies to improve cell performance, including material property optimization, structural and interfacial engineering, as well as various post‐treatments. At the end, the challenge and perspective of dopant‐free passivating contact c‐Si solar cells are discussed.image

Electrochemical Desalination Using a Hybrid Redox-Flow Cell with a Ceramic Ion Conductor

Electrochemical desalination is a potentially energy-efficient strategy for distributed, small-scale purification of brackish sources, especially as compared to conventional processes that are reliant on heat or reverse osmosis. One promising subcategory of electrochemical desalination systems features a combination of sodium-intercalating electrodes and polymer-based anion-exchange membranes. Although desalination is technically feasible with this design, polymer-based ion-exchange membranes tend to have imperfect permselectivities and to be susceptible to water crossover between diluate and concentrate streams. These issues result in parasitic losses that increase the energetic cost of desalination.We propose a hybrid flow cell design that features a redox-active electrolyte separated from a solid, anion-converting or anion-intercalating electrode with a solid ceramic ion-exchange membrane. By making use of a dense, ceramic membrane with a far greater selectivity for sodium ion conduction than analogous polymeric ion-exchange membranes, the parasitic issues described above are avoided. We discuss considerations that will impact the relationship among electrode and electrolyte properties, operational parameters (e.g. current density, concentration factor and water recovery percentage) and the energetic cost of desalination.

(Invited, Digital Presentation) Advanced Passivating Contacts for Silicon Photovoltaics

Carrier selective passivating contacts, which provide dual functions of surface defect passivation and extracting one type of charge carriers, is a key enabler for high efficiency Si solar cells. Here we introduce two passivating contact materials developed in our lab: one is the hydrogenated nanocrystalline silicon (nc-Si:H) and the other is the metal-oxide (non-silicon) material. For the nc-Si:H, it is demonstrated that the use of the (p)nc-Si:H/(i)a-Si:H stack instead of the conventional (p)a-Si:H/(i)a-Si:H in silicon heterojunction solar cells provides not only a mitigation of the parasitic absorption loss but also improvements in passivation and electrical contact properties. This results in an efficiency increase by 0.3-0.6% absolute compared to our reference cell, and a best cell efficiency of 23.5%. For metal-oxide material, we have developed an atomic-layer-deposited titanium oxide (TiOx) that functions as an efficient and transparent hole-selective passivating contact without using buffer layer, leading to the proof-of-concept solar cells with efficiencies above 20%. An example of applying the developed contact material as a recombination junction layer of the perovskite/Si tandem solar cell will be presented.

Membrane Transport and Performance in the All-Aqueous Copper Thermally Regenerative Battery

Redox flow batteries are emerging as a promising method to provide grid-scale power and long-duration energy storage safely and economically. The thermally regenerative ammonia battery (TRAB) is a new redox flow battery category that can be recharged using low-grade waste heat rather than electric energy, adding further flexibility to the applicability of flow battery systems. Recently, a new TRAB with all-aqueous electroactive species (referred to as the Cuaq-TRAB), as opposed to deposition-dissolution reactions, was found to have superior energy and power densities relative to competing TRABs. The use of bromide and ammonia stabilizes for both Cu(I) and Cu(II) oxidation states, while also creating a cell potential of up to 1.0 V. The potential can be recovered by thermally separating ammonia from the electrolyte and adding it back to alternate electrolyte chambers in successive cycles. Potential improvements in overall cell performance are possible by reducing ohmic losses associated with membrane selection. However, the ideal membrane for the Cuaq-TRAB is not obvious and raises interesting transport questions relative to the dominant redox-active copper species being negatively charged in the catholyte but positively charged in the anolyte. Furthermore, membrane crossover of ammonia, a small, uncharged molecule, was previously shown to be a primary source of parasitic losses for TRABs. Therefore, we investigated how different membrane types (cation, anion, and non-selective) affected ion transport and TRAB performance. A batch symmetry cell was used to determine membrane conductivity in the Cuaq-TRAB environment and membrane diffusion coefficients of each species in the electrolytes. Flow cell experiments were also conducted to find peak power, energy density, average power during discharge, and capacity fade over successive electric charge/discharge cycles. Tradeoffs between membrane conductivity and permeability observed in the symmetry cell are manifested in flow cell results as either high peak and average power or high energy density and low capacity fade. These results expand on potential methods for controlling transport in redox flow batteries and demonstrate the potential for non-selective membranes for electrochemical energy technologies.