Resistive Power Loss Research Articles

Indirect Liftoff Mechanism for High‐Throughput, Single‐Source Laser Scribing for Perovskite Solar Modules

AbstractA high‐throughput, single‐source laser scribing method exploiting a transparent conducting oxide (TCO) indirect liftoff mechanism is developed to produce serially interconnected perovskite solar modules. The TCO‐based indirect liftoff mechanism relies solely on laser absorption in the front transparent electrode material reducing thermal damage to the overlying layers and allowing for fast scribing speeds with low‐cost μs‐pulse duration fiber laser systems. Minimal resistive power losses are observed with the method compared to conventional ablative laser scribes, maintaining the power conversion efficiencies of small‐area devices (≈0.2 cm2) across significantly larger deposition areas (≈1 cm2). Demonstrating > 3 m s−1 processing speeds, TCO‐based liftoff provides the highest throughput laser scribing method for thin‐film photovoltaic devices produced on glass/TCO substrates, capable of processing large‐area perovskite solar modules at a manufacturing scale.

Calculating some Powers and Traction Force for Two Plows in Primary Tillage

Traction force and power requirement when performing primary tillage occupy the minds of almost farmers, this field research had aim to determine and calculate the pulling force of the most commonly used moldboard and chisel plows, the research conducted in silt clay loam for chisel and moldboard plows as the main factor, two depths of tillage 18 and 25 cm as a second factor and three speeds of tractor 2.55, 4.30 and 6.15 km.h-1 as a third factor. Moldboard plow recorded least traction force 7.550 kN, drawbar power 11.583 hp, power losses due to slippage 1.088 hp, power on the rear axle of the tractor 15.770 hp and brake horse power 17.495 hp. Chisel plow recorded best traction efficiency 76.217 % and total traction efficiency 68.659 %. Depth of tillage 18 cm recorded least traction force 7.837 kN, drawbar power 12.190 hp, power losses due to slippage 0.986 hp. Speed tractor 2.55 km.h-1 recorded least traction force 8.246 kN, drawbar power 7.329 hp, power losses due to slippage 0.618 hp, resistance power losses due to motion 1.775 hp and power on the rear axle of tractor 9.723 hp. Correlation among performance indicators were positive and negative correlation significantly, also were insignificant correlation.

Current collector design strategies: The route to realising scale-up of structural power composites

Multifunctional structural power composites, which combine mechanical load-bearing and electrochemical energy storage, will transform electric vehicle design. This work focuses on structural supercapacitors, based on carbon aerogel-modified carbon fibre electrodes with copper current collectors. In common with many structural power embodiments, scale-up of these devices is currently limited by large internal resistances and the mass associated with current collection. There is a trade-off between the overall resistive power loss and the additional mass for the current collector material. However, in these devices, mechanical integrity is provided by the structural electrodes, allowing a range of collector designs to be considered. Using finite element simulations, these current collection strategies are explored quantitatively across a range of design space variables. The key conductivity parameters were measured experimentally, using the best existing materials, to inform direct current conduction simulations of the electrode/current collector assembly. For the present device configuration, the performance trade-off is governed by the area of the current collector. The most effective near-term strategy for power loss mitigation lies in reducing the contact resistance; however, improvements can also be obtained by modifying the collector geometry. The findings of this paper can be generalised to other structural power composites and monofunctional energy storage devices, which are relevant in many mass-sensitive electrochemical applications.

THE WATER FLOW MOVEMENT MODELING IN PASSIVE DISINTEGRATOR OF THE GRAIN MOLASSES’ INSTALLATION

The equipment features’ studying is important because the volume of small and medium sized businesses related to dairy and meat farming in our country is growing. It is also important for the energysaving technologies’ developing and improving. Due to the grain’s high demand as a farm animals’ feed element, its processing technologies are being developed and widely used. In particular, technologies and technical means of grain molasses preparing have been developed. The scheme of grain molasses preparation and modeling conditions are given, water movement in a passive shredder’s modeling results are presented. This modeling in the Star CCM+ program was carried out. The water flow around two grids located at a distance equal to 100 and 200 mm was set; the pipe diameter d = is 30 mm, calculated section length - 1 m. At looking through the fields’ velocity and fluid flow’s lines in the shredder, it was revealed that the flow rates in both cases under consideration are almost identical. There is a velocity clear increasing when the liquid passes through the openings of the gratings and the water bends around the gratings up to a value of 23 m/s. The gratings’ presence in the shredder leads to network resistance and flow power loss’s increasing. The distance between the grids increasing allows to reduce slightly the resistance of the network (in 3%) and flow power’s loss (in 5%). The fluid motion’s given modeling has shown that the passive shredder scheme in the form of a circular tube with two grids installed in it can be considered ineffective due to the proposed device’s high resistances.

Slurry electrode properties for minimizing power loss of flowable electrochemical hydrogen storage systems

Electrochemical hydrogen storage in porous carbon particles in slurry electrodes is a function of particle size, shape, and material. Ideal slurry electrodes have high electrical (both electronic and proton) conductivity to minimise the electric resistance and ohmic power loss, and low viscosity to minimise parasitic pumping power, while utilising porous particles with high surface areas for hydrogen storage. In this paper we show that although carbon black (CB) particles have higher electronic conductivity than activated carbon (aC) particles, their proton conductivity is significantly lower, and they cannot be used for hydrogen storage. We increase the electronic conductivity of aC slurries by adding CB particles. We demonstrate that the addition of a 1:10 ratio by weight of CB to aC particles reduces the electric resistance and ohmic power loss by 50%, while parasitic pumping power increases by only 15% compared to slurries with no CB particles. We conclude that at low Reynolds numbers, for 5 to 20 wt% aC slurries with different particle sizes, slurries containing 20 wt% spherical aC particles smaller than 50 μm mixed with 2 wt% CB particles provide the highest electronic and proton conductivity, while not significantly increasing parasitic pumping power.

Hemolytic and biological assessment of lithium substituted hydroxyapatite nanoparticles for L929 and Hela cervical cancer cells

The improvement of performance and biological activity of bone substituted materials using nanotechnology is the main concern of dental and orthopedic surgery. Calcium orthophosphate-based biomaterials i.e. hydroxyapatite have a broad area of attractive biomedical implant operations. The current need for biomaterials implant surgery is bone substitute materials are characterized by biocompatibility, the good life of implants, bioactivity, there is not any post-surgery infections, good blood compatibility, all the mentioned properties are without the resistance or immune power loss is a big challenge for researchers and scientists. In the present investigation the synthesis, characterization, cell cytotoxicity, and blood compatibility of hydroxyapatite have been carried out. Enhancement of biocompatibility properties after incorporation of lithium in hydroxyapatite in physiochemical and biological conditions has been investigated. Lithium substituted hydroxyapatite samples were successfully synthesized by a modified solution combustion process with varying molar concentrations. X-ray diffraction (XRD) and transmittance electron microscopy (TEM) results confirm the structural and surface morphology of Li-HA nanoparticles, respectively. Two different cell lines i.e. L929 and Hela cervical cell lines were used for the biocompatibility of the Li-HA nanoparticles by using MTT assays for 12 and 24 h. The synthesized Li-HA is not only compatible with both cell lines but also is compatible with human blood and is plausible for further biomedical applications in orthopedic and dental applications.

Constructal design of top metallic contacts on a disc-shaped solar cell

Trends in crystalline silicon photovoltaic improvements demonstrate that some of the key factors that have contributed to reaching efficiency values up to 23 % are the introduction of the passivated emitter and rear cell structure with local rear contacts in low-cost large-volume fabrication; the reduction of the width of the front metallization fingers, from about 100 microm to less than 30 micro m in large volume production, and the re-emergence of mono-crystalline silicon wafers as a consequence of cost reduction in the Czochralski silicon ingot fabrication process. In the present work, we have developed a theoretical model that defines the geometric arrangement of a branched top metallic contacts network over a solar cell with a disc-shaped body. The solar cell considers two main regions: the solar cell material and an insert of metallic material for the collection of the photogenerated electrical current. The geometric characteristics of the network are defined from the minimization of the resistive power losses applying the constructal design method. As a fundamental result, the optimal lengths, branching angles, and geometrical relationships of the n-branched network are determined. The numerical results show that the dimensionless power losses of the branched arrangement of contacts present minimum values for the allocation of the metallic material and the disc size of the solar cell.

Optimized front TCO and metal grid electrode for module‐integrated perovskite–silicon tandem solar cells

AbstractTo unlock the full potential of perovskite–silicon tandem solar cells with >30% efficiency at presumably low cost, the transparent conductive oxides (TCOs) and metal grid at the front side need to be adapted compared to classical silicon heterojunction (SHJ) solar cells. By means of optical and electrical modelling, we consider the main aspects to optimize the front electrode for the tandem case, where in contrast to silicon single junction devices, there are (i) different optical properties including a lower refractive index of the perovskite absorber (ii) about half the current, thus quarter the resistive power losses for the same series resistance contribution (iii) lateral transport at the front needs to be provided solely by the front TCO layer and (iv) lower thermal stability of the perovskite, which affects TCO deposition conditions and results in a less efficient sintering of the silver screen printing pastes. This study concludes that compared to silicon heterojunction cells, the thickness of the front TCO should be reduced from 75 nm to around 20 nm, resulting in less parasitic absorption and a potential cost reduction of 1.46 €ct/cell for ITO. We investigate the impact of different front metallization including plating and silver screen printing and showcase that for multi‐wire interconnection concepts, the number of wires can be reduced from 18 wires to 9 or even less depending on the front metallization. Finally, we give an outlook on the silver consumption and levelized cost of electricity.

Miniaturization of InGaP/InGaAs/Ge solar cells for micro‐concentrator photovoltaics

AbstractMicro‐concentrator photovoltaic (CPV), incorporating micro‐scale solar cells within concentrator photovoltaic modules, promises an inexpensive and highly efficient technology that can mitigate the drawbacks that impede standard CPV, such as resistive power losses. In this paper, we fabricate micro‐scale multijunction solar cells designed for micro‐CPV applications. A generic process flow, including plasma etching steps, was developed for the fabrication of complete InGaP/InGaAs/Ge microcells with rectangular, circular, and hexagonal active areas down to 0.089 mm2 (0.068‐mm2 mesa). Large cells (>1 mm2) demonstrate good electrical performance under one sun AM1.5D illumination, but a degradation in the open‐circuit voltage (VOC) is observed on the smallest cells. This effect is attributed to perimeter recombination for which a passivation effect by the antireflective coating partially recovers the VOC. The VOC penalty for small cells is also reduced under high‐intensity illumination, from 3.8% under sun to 1.0% at 974 suns. High intensity illumination yields an efficiency of 33.8% under 584 suns for a 0.25‐mm2 and microcells are expected to show higher efficiency than standard cells under very high concentration.

A Symmetric Multichamber Hydraulic Cylinder With Variable Piston Area: An Approach to Compact and Efficient Electrohydrostatic Actuation

Abstract This paper presents an approach for designing symmetric (effective cylinder area during extension is the same as that during retraction) multichamber cylinders with discretely variable piston area. The design methodology is presented in a generalizable manner and is demonstrated on an example five-chamber cylinder design. A method for finding symmetric multichamber cylinder configurations from a given cylinder topology is presented, and subsequently, a method for discretely varying the effective piston area is developed, subject to a cylinder symmetry constraint. Furthermore, an algorithm is presented to optimally switch the effective cylinder area of an electrohydrostatic actuation system either to minimize the magnitude of motor torque or to minimize resistive power losses in the system. Additionally, a method for optimizing standard (constant area) hydraulic cylinders to minimize motor torque magnitude or resistive power losses is presented. These methods are then demonstrated on an example electrohydrostatic actuation system via simulation. Results indicate that this multichamber cylinder approach with discretely variable piston area may allow for the design of compact and efficient actuators relative to standard methods.

Tire and soil effects on power loss: Measurement and comparison with finite element model results

In the present study, the effect of vertical load, tire inflation pressure and soil moisture content on power loss in tire under controlled soil bin conditions were investigated. Also a finite element model of tire-soil interaction in order to achieve a suitable model for predicting power loss in tire was created. Increasing the vertical load on the tire had a noteworthy impact on increasing the tire contact volume with the soil, reducing the percentage of slip, and increasing the rolling resistance; although, reducing the load on the tire had the opposite effect. At a constant inflation pressure, by increasing the vertical load on the tire, the amount of power loss due to the rolling resistance and the total power loss in the tire increased. Increase in soil moisture content increased the power loss caused by slip. Increasing the inflation pressure at a constant vertical load, also increasing the soil moisture content, led to an increase in the power loss caused by rolling resistance, and increase total power loss. The obtained error for estimating power loss of rolling resistance and total power loss was satisfactory and confirmed the acceptability of the model for power loss estimation.

Subcell Segmentation for Current Matching and Design Flexibility in Multijunction Solar Cells

Subcell segmentation is a method to obtain nearly ideal current-matching while employing nonideal bandgap combinations in high-efficiency multijunction solar cells. By splitting each subcell into multiple semitransparent pn junctions, called segments, current-matching can be satisfied by layer design rather than material selection. This architecture replaces the standard requirement for an optimal combination of bandgaps with a simpler requirement for optimal layer thicknesses in each series-connected segment. The total device current is divided across all segments, reducing the resistive power loss especially under nonuniform illumination or high to extreme concentration. Detailed balance-based analysis of three- and four-subcell devices in both terrestrial concentrator and one-sun space applications demonstrates that the segmented architecture can approach the theoretical efficiency peak using a broad range of physically realizable bandgap combinations. For example, detailed-balance analysis reveals a 7.5%–8.1% absolute efficiency improvement for 1-cm2 segmented cells compared with standard InGaP/InGaAs/Ge designs under 1000-suns AM1.5D illumination. Higher-order segmentation multiplies the number of segments in all subcells by a common multiple, which further reduces the device current, resistive power loss, and segment thicknesses.

EV fuse design cost reduction based on Thermal-Electric Conduction analyses

The focus of the study is set to evaluate design change which is modification of terminals of the EV fuse from L-type to axial type as well as modification of forming element material. Main target is to decrease cost of the product by shortening terminals and, mainly, by minimizing Ag material volume for cladding element. This is done through determining thermal distribution, operating time at specific currents (It-curves) and resistance (power loss) at interconnections by series of simulation analyses over virtual prototypes. Analyses methodology is based on initial model adjustment using physical tests data that allows to adjust virtual model to improve simulation accuracy. The study demonstrates an efficient combination of physical and virtual prototyping in product design development process.

Buck converter with adaptive pass device employing capacitive and resistive power loss equalization

This paper presents a novel control technique to efficiently supply a wide range of output load current in a buck converter using an adaptive pass device at the output stage. The adaptive pass device segment size control technique is based on equalization of capacitive power loss and resistive power loss terms by taking into account load current, input supply voltage, temperature, process, and aging conditions; thus, leading to optimum efficiency at the output stage in a broad operating region. Power calculations are done in analog domain using a novel arithmetic cell called the adaptive gm stage. The additional power consumption introduced by the power calculation blocks is less than 1.4 μA, which enables high efficiency operation even in low load currents. The circuit and layout are designed in a standard 130 nm CMOS technology and simulation results show 5–35% efficiency increase for mid/low load currents compared to a fixed output stage buck converter. Compared to other reported adaptive pass device buck converters, 4% increase in peak power efficiency with 3× broader load current range has been achieved.

Loss Minimization Control Strategy for Linear Induction Machine in Urban Transit Considering Normal Force

Linear induction machine (LIM) in urban transit suffers greatly from poor efficiency due to the large air-gap length and the end-effects, including both transversal edge- and longitudinal end-effects caused by the cut-open magnetic circuit and different width between primary and secondary. Besides, the unique normal force existing in LIM that could be as high as four times of the thrust would create undesired additional resistance force and power loss, bending of the guide way, and tire wear. Addressing these issues, this paper proposes a novel loss minimization control (LMC) strategy for LIM to reduce the steady-state loss and normal force simultaneously. First, an improved loss model of LIM is proposed on the basis of the analysis of LIM copper and core loss. Second, the LIM normal force including both attractive and repulsive components is modeled in the same manner as the loss model. Third, a novel loss minimization cost function is set up, based on which the optimal solution is obtained through both analytical and numerical approaches, and thus an improved LMC strategy is carried out to achieve the minimization of steady-state loss and normal force at the same time. The proposed method is comprehensively investigated on one 3-kW arc induction machine (one prototype for actual LIM), and its effectiveness is fully validated through both simulation and experimental results.

Linear discharge model, power losses and overall efficiency of the solid oxide fuel cell with thin film samarium doped ceria electrolyte. Part II: Power losses and overall efficiency

Samarium doped ceria (SDC) shows obvious electronic conduction in a reducing atmosphere, which results in internal short-circuiting of the SOFC. In this work, we initiatively combine the Gorelov modified electromotive force (EMF) method and the Liu modified EMF method to determine the internal electronic resistance of the SOFC with 60 μm SDC film electrolyte. The internal electronic resistance determined with the Gorelov modified EMF method is a little larger than that determined with the Liu modified EMF method. The power loss of the SOFC is mainly resulted from the internal short-circuiting, oxygen ionic resistance and electrode polarization resistance. At low external current density, the internal short-circuiting power loss is predominant, while at high current density the oxygen ionic resistance power loss is predominant. Temperature has little effect on the maximum efficiency of the SOFC. When the SOFC works at the maximum power output, the efficiency of the cell is about 30%, but if the electronic conduction of the SDC electrolyte could be eliminated, the efficiency could be improved by 2.5 times.

Design optimization with computational fluid dynamic analysis of β-type Stirling engine

The real performance of Stirling engine always deviates from prescribed theoretical potential. This is mainly because of complex interaction of different engine parameters, heat transfer process of oscillating flows and fluid dynamics. In order to develop an effective methodology to optimize geometric design of Stirling engines a beta-type rhombic drive Stirling engine was investigated whose initial experimental efficiency and output power was relatively low. This paper presents a sensitivity analysis of β-type Stirling model and proposed a combined method to carry out multi-objective optimization of a Stirling engine using detailed information of pressure and volume provided by CFD analysis. The geometric parameters of heat exchangers including heater and cooler tubes diameter with length, regenerator length, matrix mesh and wire diameter were considered for maximizing thermal efficiency, output power and minimizing flow resistance power loss in Stirling engine. CFD analysis covers a detailed study of real and optimized model with best experimental agreement. The CFD results include the detailed description of Stirling cycle with temperature contour, velocity vectors and pressure–volume variation in compression and expansion spaces. The proposed modification results an increase of 2 percentage points in thermal efficiency and more than 80W in power output when the dead volume of heater, cooler and regenerator is reduced up to 54%, 42% and 24% respectively. The additional dead volume leads to a phase shift of the pressure which is also the main reason of lowering output results.

Energy breakdown in capacitive deionization

We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages. We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). We show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency.

High aspect ratio and large area metallic nanogrids as transparent electrodes on optoelectronic devices

The authors demonstrate high aspect ratio and large area metallic nanogrids as transparent electrodes with reduced series resistance on GaAs based optoelectronic devices. The fabrication process uses ultraviolet photolithography techniques, pulsed reactive ion etching, and two metallization steps: a vapor deposited contact seed layer and a thickening step by electrodeposition. As a result, a threefold reduction in resistive power losses is achieved with a contact grid transmission comparable to state-of-the-art devices.

Two-dimensional current flow in stringed PV cells and its influence on the cell-to-module resistive losses

In a c-Si wafer based photovoltaic (PV) module, the current generated in each solar cell must flow to the ribbons soldered onto its front and rear surfaces. Conventionally, a simplified current flow pattern is assumed in calculating the resistive power losses in the cell plane and the ribbons. However, it is found in this work that this approach leads to more than 30% overestimation for the resistive loss on the rear-side ribbons for a typical monofacial solar cell. This work uses a detailed two-dimensional network simulation, which accurately solves the current flow patterns in both cell surface planes. It is found from this work that the conventional approach is sufficiently accurate in the case of an H-pattern finger-busbar metallization scheme, but not with a full-area metallization pattern, as commonly used on the rear of silicon wafer solar cells. For a c-Si PV module using 3-busbar monofacial solar cells, the actual resistive loss on the rear metallization plane is only 67% of the value calculated conventionally. Also, 17% of the cell interconnection resistive loss comes from the rear metal sheet, which is often ignored. To correct the results of the conventional approach, we introduce correction factors for c-Si PV modules using monofacial cells. Using the correction factors we achieve a significantly better prediction of the module’s fill factor. We apply this approach to explain why the fill factor gain from replacing full-size solar cells by halved cells in a c-Si PV module is higher for bifacial than for monofacial solar cells. Experimentally, we find a 1.7% relative fill factor increase for monofacial halved-cell PV module, and a 2.0% relative increase for bifacial halved-cell PV module. The simulation results agree quite well with the experimental results. Since the influence from the cell metallization pattern on the cell-to-module resistive loss has not been investigated before, this work can be very useful correction and compensation for established methods analysing the cell-to-module losses. It also offers the guideline for PV module optimization in terms of further reducing the resistive loss.