Energy Loss Analysis Research Articles

System-Level Dynamic Model of Redox Flow Batteries (RFBs) for Energy Losses Analysis

This paper presents a zero-dimensional dynamic model of redox flow batteries (RFBs) for the system-level analysis of energy loss. The model is used to simulate multi-cell systems considering the effect of design and operational parameters on energy loss and overall performance. The effect and contribution of stack losses (e.g., overpotential and crossover losses) and system losses (e.g., shunt currents and pumps) to total energy loss are examined. The model is tested by using literature data from a vanadium RFB energy storage. The results show that four parameters mainly affect RFB system performance: manifold diameter, stack current, cell standard potential, and internal resistance. A reduction in manifold diameter from 60 mm to 20 mm reduced shunt current loss by a factor of four without significantly increasing pumping loss, thus boosting round-trip efficiency (RTE) by 10%. The increase in stack current at a low flow rate increases power, while the cell standard potential and internal resistance play a crucial role in influencing both power and energy output. In summary, the modeling activities enabled the understanding of critical aspects of RFB systems, thereby serving as tools for system design and operation awareness.

Elemental mapping in single-particle reconstructions by reconstructed electron energy-loss analysis.

For macromolecular structures determined by cryogenic electron microscopy, no technique currently exists for mapping elements to defined locations, leading to errors in the assignment of metals and other ions, cofactors, substrates, inhibitors and lipids that play essential roles in activity and regulation. Elemental mapping in the electron microscope is well established for dose-tolerant samples but is challenging for biological samples, especially in a cryo-preserved state. Here we combine electron energy-loss spectroscopy with single-particle image processing to allow elemental mapping in cryo-preserved macromolecular complexes. Proof-of-principle data show that our method, reconstructed electron energy-loss (REEL) analysis, allows a three-dimensional reconstruction of electron energy-loss spectroscopy data, such that a high total electron dose is accumulated across many copies of a complex. Working with two test samples, we demonstrate that we can reliably localize abundant elements. We discuss the current limitations of the method and potential future developments.

Investigation into the Energy Loss Mechanism of Pump Turbine During the Runaway Process Based on Entropy Production Theory

Abstract The power-trip of the pump under certain conditions leads to the runaway of the unit, causing dangerous transitional process in pumped storage power stations. This process is characterized by transient hydraulic features like flow separation and vortex structures, which increase hydraulic losses significantly and severely impact unit efficiency and stability. This paper aims to elucidate the mechanism of energy loss due to unstable flow during pump turbine runaway. It focuses on a high-head model pump turbine, examining the transient flow process from pump conditions to runaway conditions. It conducts quantitative analysis of energy loss using entropy production theory, besides, further clarifies the location and causes of hydraulic losses by integrating with internal flow analysis. The results show that a significant high-entropy production zone is captured in the pump braking condition, indicating extremely chaotic internal flow in this area during the runaway transition process. Additionally, throughout the transition process, turbulent entropy production initially increases, then decreases. Turbulent entropy production accounts for more than 80% of total entropy production, indicating that turbulent entropy production dominates throughout the entire transition process. The energy of the water is primarily dissipated within the runner during the runaway process. The maximum proportion is 87%, which is in the pump braking condition. Correlation analysis between flow and hydraulic losses reveals that vortex structure induced by flow separation under off-design conditions is the primary contributor to increased hydraulic losses.

Parametric optimization and energy loss analysis of a solar thermophotonic energy converter

In the present work, the model of a solar thermophotonic energy converter (STEC) is established, of which the energy balance constraint equations at both the hot and cold sides are numerically solved to uncover the dependencies of the operating temperatures of the light emitting diode (LED) and photovoltaic (PV) cell on thermal, electrical, and structural parameters. For a given band-gap 0.36 eV of the semiconductor and a concentrated factor 20 of the concentrator, the LED’s bias voltage and the PV cell’s output voltage are optimized to achieve a local maximum efficiency 13% of the STEC. Furthermore, the conditions are optimized to attain an overall maximum efficiency of 15.94%. The distributions of energy losses are presented to reveal the underlying loss mechanisms. The results obtained in this work can provide theoretical guidance for the efficient utilization of solar energy.

Analysis of energy losses and head produced by a radial impeller using particle image velocimetry

Analysis of energy losses and head produced by a radial impeller using particle image velocimetry

Frequency optimization of the AUV wireless charging system for minimum energy dissipation

With the growing demand for ocean exploration, research on docking technology is gaining popularity, resulting in the development of various types of docking systems. In contrast to traditional cable-based systems, this paper introduces a self-powered docking system designed for AUV recovery and recharging. To minimize energy loss in the self-powered system, an analysis of eddy current loss produced by the coils in the seawater is conducted, and a calculation method for determining the equivalent eddy current impedance is proposed. This allows for the transformation of energy loss analysis from the magnetic field to circuit analysis. Then the efficiency of the inductively coupled power transmission system in seawater is analyzed, and a frequency optimization method is proposed to minimize dissipated energy during the AUV battery charging process. Finally, the effectiveness of the frequency optimization method is validated through laboratory experiments. Moreover, the results of the sea trial confirm the feasibility of the optimal wireless charging system operating in a seawater environment.

Photovoltaics Energy Potential in the Largest Greek Cities: Atmospheric and Urban Fabric Effects, Climatic Trends Influences and Socio-Economic Benefits

This comprehensive study explores the influence of aerosols and clouds on solar radiation in the urban environments of nine of Greece’s largest cities over the decade from 2014 to 2023. Utilizing a combination of Earth Observation data, radiative transfer models, and geographic information systems, the research undertook digital surface modeling and photovoltaic simulations. The study meticulously calculated the optimal rooftop areas for photovoltaic installation in these cities, contributing significantly to their energy adequacy and achieving a balance between daily electricity production and demand. Moreover, the research provides an in-depth analysis of energy and economic losses, while also highlighting the environmental benefits. These include a reduction in pollutant emissions and a decrease in the carbon footprint, aligning with the global shift towards local energy security and the transformation of urban areas into green, smart cities. The innovative methodology of this study, which leverages open access data, sets a strong foundation for future research in this field. It opens up possibilities for similar studies and has the potential to contribute to the creation of an updated, comprehensive solar potential map for continental Greece. This could be instrumental in climate change mitigation and adaptation strategies, thereby promoting sustainable urban development and environmental preservation.

Analysis of internal flow and energy loss in a LNG cryogenic submerged pump

Analysis of internal flow and energy loss in a LNG cryogenic submerged pump

A Comparative Analysis of Friction and Energy Losses in Hydrogen and CNG Fueled Engines: Implications on the Top Compression Ring Design Using Steel, Cast Iron, and Silicon Nitride Materials.

Optimizing the design of the top compression ring holds immense importance in reducing friction across both traditional Internal Combustion (IC) engines and hybrid power systems. This study investigates the impact of alternative fuels, specifically hydrogen and CNG, on the behavior of top piston rings within internal combustion (IC) engines. The goal of this approach is to understand the complex interplay between blow-by, fuel type, material behavior, and their effects on ring friction, energy losses, and resulting ring strength. Two types of IC engines were analyzed, taking into account flow conditions derived from in-cylinder pressures and piston geometry. Following ISO 6622-2:2013 guidelines, thick top compression rings made from varying materials (steel, cast iron, and silicon nitride) were investigated and compared. Through a quasi-static ring model within Computational Fluid Dynamics (CFD), critical tribological parameters such as the minimum film and ring friction were simulated, revealing that lighter hydrogen-powered engines with higher combustion pressures could potentially experience approximately 34.7% greater power losses compared to their heavier CNG counterparts. By delving into the interaction among the fuel delivery system, gas blow-by, and material properties, this study unveils valuable insights into the tribological and structural behavior of the top piston ring conjunction. Notably, the silicon nitride material demonstrates promising strength improvements, while the adoption of Direct Injection (DI) is associated with approximately 10.1% higher energy losses compared to PFI. Such findings carry significant implications for enhancing engine efficiency and promoting sustainable energy utilization.

Radiofrequency Induction Heating for Green Chemicals Manufacture: A Systematic Model of Energy Losses and a Scale-Up Case-Study.

Radiofrequency (RF) induction heating has generated much interest for the abatement of carbon emissions from the chemicals sector as a direct electrification technology. Three challenges have held back its deployment at scale: reactors must be built from nonconductive materials which eliminates steel as a design choice; the viability of scale-up is uncertain; and to date the reported energy efficiency has been too low. This paper presents a model that for the first time makes a comprehensive analysis of energy losses that arise from RF induction heating. The maximum energy efficiency for radio frequency induction heating was previously reported to be 23% with a typical frequency range of 200-400 kHz. The results from the model show that an energy efficiency of 65-82% is achieved at a much lower frequency of 10 kHz and a reactor diameter of 0.2 m. Energy efficiency above 90% with reactor diameters above 1 m in diameter are predicted if higher voltage radio frequency sources can be developed. A new location of the work coil inside of the reactor wall is shown to be highly effective. Losses arising from heating a steel reactor wall in this configuration are shown to be insignificant, even when the wall is immediately adjacent to the work coil. This analysis demonstrates that RF induction heating can be a highly efficient and effective industrial technology for coupling high energy demand chemicals manufacture electricity from zero carbon renewables.

Exploring the collision, acoustic and thermal energy dissipation distribution of discrete mass

This research delves into the transfer and loss of energy in a discrete mass when subjected to forced vibration. Using discrete element method (DEM), we analyzed the dynamic behavior of regular spherical granular assemblies and the energy distribution characteristics under different excitation frequencies and reduced accelerations. Moreover, the energy transfer and dissipation process of granular assemblies under different vibration states are studied using an experimental method. The results show that the granular assemblies will produce collision energy dissipation, thermal energy dissipation, acoustic energy dissipation and other forms of energy dissipation in the forced vibration state and the proportion of different energy dissipation under different excitation is given. The collision and friction of granular assemblies are the key to affecting other forms of energy dissipation. When the excitation increases, the energy dissipation forms are generated inside the granular assemblies, and the proportion of collision energy dissipation of the granular assemblies increases. The acoustic energy above 20 kHz occupies the main part of the acoustic energy dissipation. Thermal energy consumption always exists, which takes a long time to play a role. The granular also have other forms of energy loss, which is hard to be measured, including Rayleigh waves generated by granular collision. In this study, the relationship between the forced vibration state of the granular assemblies and the energy loss distribution is established. Various types of energy transfer and conversion distribution which further enriches the energy dissipation of discrete element calculation of the granular assemblies is discussed and provides a reference for the energy loss analysis of the granular assemblies.

Energy loss analysis in two-stage turbine of compressed air energy storage system: Effect of varying partial admission ratio and inlet pressure

The compressed air energy storage (CAES) system experiences decreasing air storage pressure during energy release process. To ensure system stability, maintaining a specific pressure difference between air storage and turbine inlet is necessary. Hence, adopting a judicious air distribution scheme for the turbine is crucial. Partial admission, based on reasoned nozzle governing methods, enhances system performance. This investigation explores the impact of varying partial admission ratio (PAR) and inlet pressure on flow dynamics and loss characteristics under rated output power. Full circumferential numerical simulations of a two-stage axial turbine within CAES system elucidates insights. First-stage efficiency declines linearly with decreasing PAR, while second-stage displays escalating reductions. Principally, turbine energy losses primarily stem from the entropy production rate (EPR) by turbulent dissipation and EPR arising from heat transfer with fluctuating temperature gradients. Partial admission significantly affects losses within the rotor, especially within the second stage. Leaving velocity loss for 50 % PAR is about 3 times that of 100 % PAR. The percentage of losses within R2 for 50 % PAR increases by 6.7 % compared with that for 100 % PAR. This research provides theoretical insights for designing, regulating, and optimizing nozzle governing and partial admission turbines in CAES systems.

The Influence of Lobe Top Clearance on the Performance of High-Speed Centrifugal Pumps

High-speed centrifugal pumps are widely used in several industries due to their high efficiency and small footprint. In actual applications, there are issues such as low operational efficiency and a small high-efficiency flow interval; particularly, the leakage occurring in the impeller channel gap presents a significant barrier to the pump’s performance and stability. This study takes the fully open impeller miniature high-speed centrifugal pump as the object and uses a numerical simulation calculation method. The objective of this research endeavor is to analyze the effects of different flow conditions on a high-speed centrifugal pump’s external characteristics, flow field characteristics, and energy loss. The findings indicate that lobe top clearance exerts a substantial impact on the efficiency of high-speed centrifugal pumps. Increasing the lobe top clearance will result in a reduction in pump head and efficiency, particularly under high flow conditions. The lobe top clearance has a significant impact on the complexity of the flow in the impeller, particularly the flow close to the suction surface of the impeller, according to an analysis of the flow field characteristics. The energy loss analysis further confirms the importance of reducing lobe top clearance for improving pump performance and reducing energy loss. These results provide valuable guidance for optimizing centrifugal pump designs with lobe top clearance.

Numerical investigation of non-uniform inflow effects on internal and external characteristics of an axial-flow pump

This paper investigates the effects of non-uniform inflow on the internal and external characteristics of an axial-flow pump. Numerical simulation is employed to study two different configurations: one with an intake sump (referred to as the intake system) and another without an intake sump (referred to as the pump system), where the intake sump introduces non-uniform inflow conditions. First, under low flow conditions, typical unstable flow phenomena are observed in the impeller, including leading edge spillage and tip leakage vortex, which are consistent with previous research findings. Second, the analysis reveals that the non-uniform inflow causes the pump system to enter the hump zone earlier, as indicated by the external characteristic curves. Energy loss analysis identifies the increased energy loss at the bell mouth due to backflow from the impeller as the main contributor to the head drop. Finally, it is observed that submerged vortices exist at the bottom of the intake sump; however, their swirling strength is insufficient to significantly affect the hump characteristics of the intake system under low flow conditions. The distinguishing factor between the two systems is the distribution of axial velocity along the radial direction in the bell mouth. The higher axial velocity near the casing of the bell mouth in the pump system supplements the energy of the liquid near the shroud side of the impeller, thus delaying the occurrence of backflow.

Research on the starting-up process of a prototype reversible pump turbine with misaligned guide vanes: An energy loss analysis

With fossil fuel depletion and rising demand for renewable energy, reversible pump turbines (RPTs) are crucial for balancing energy supply. Understanding the dynamics of RPTs during starting-up is essential for optimal performance and stability in renewable energy systems. The unique “S" curve of RPTs can lead to instability under transient conditions. This study aimed to investigate the impacts of misaligned guide vanes (MGV) devices on prototype RPT stability, pressure pulsation, and performance improvement during the starting-up process. Using CFD simulation, flow characteristics and energy loss during start-up were analyzed and validated against experimental data. The results show that MGV enhances stability but induces significant energy loss. The analysis of entropy production, vorticity transport, and pressure fluctuation revealed high energy loss regions and the evolution of vortices during the starting-up process. This study provides new insights into hydrodynamic challenges and energy loss with MGV in prototype RPT start-up, with implications for optimizing pumped storage hydropower operations. Overall, this study has valuable engineering significance for the development and application of RPT in renewable energy systems.

Design, Analysis, and Comparison of Electric Vehicle Drive Motor Rotors Using Injection-Molded Carbon-Fiber-Reinforced Plastics

Due to their excellent mechanical strength, corrosion resistance, and ease of processing, carbon fiber and carbon-fiber-reinforced plastics are finding wide application in diverse fields, including aerospace, industry, and automobiles. This research explores the feasibility of integrating carbon fiber solutions into the rotors of 85-kilowatt electric vehicle interior permanent magnet synchronous motors. Two novel configurations are proposed: a carbon fiber wire-wound rotor and a carbon fiber injection-molded rotor. A finite element analysis compares the performance of these models against a basic designed rotor, considering factors like no-load back electromotive force, no-load voltage harmonics, cogging torque, load torque, torque ripple, efficiency, and manufacturing cost. Additionally, a comprehensive analysis of system efficiency and energy loss based on hypothetical electric vehicle parameters is presented. Finally, mechanical strength simulations assess the feasibility of the proposed carbon fiber composite rotor designs.

Energy loss analysis of a double-suction centrifugal pump using in pump mode and turbine mode

As an economical energy recovery device, pump as turbine (PAT) is widely used in micro-hydropower stations and the chemical industry. The inlet and outlet pipelines connected to the double-suction pump are on the same horizontal line. As the pipeline layout is very convenient, in some chemical industries, the way of residual pressure energy utilization is increasing using the double-suction pump as a turbine. Based on numerical simulation, experimental verification, and entropy generation theory, the energy loss rule of each flow component in the pump mode and turbine mode under different flow rates is compared and analyzed. The results show that when the double-suction pump is used as a turbine, the flow rate at the best efficiency point (BEP) in the turbine mode shifts to a large flow rate by 30.89% and the BEP efficiency decreases by 1.30%. In the pump mode and turbine mode, the main energy loss component is the impeller, and the turbulent entropy generation power and the wall entropy generation power are the main sources of energy loss. The energy loss in the suction chamber and impeller increases sharply, and the energy loss is primarily enhanced in the blade trailing edge and the tongue near due to the unsteady flow in the turbine mode. Due to the complex structure, the spiral suction chamber is not suitable for the flow direction of the fluid flow out of the impeller, and the flow state inside the impeller is negatively affected by the suction chamber in the turbine mode. This paper provides a theoretical basis for the design and application of double-suction centrifugal PAT.

Vortex Cleaning Device for Rice Harvester: Design and Bench Test

To solve the problem of increased grain impurity rate and grain loss rate caused by clogging of sieve holes during the cleaning process of ratooning rice, a spiral step cleaning device was designed, which disturbed the flow field at the sieve holes through vortex in the slot and disrupted the force balance of the blockages at the sieve holes. The device mainly includes a cleaning separation core and a cleaning separation core shell. Firstly, the main parameters of the cleaning separation core were determined, and the critical shear airflow velocity was obtained through theoretical analysis. Through energy loss analysis, the fan wind speed was determined to be 11.5 m/s. Secondly, the CFD-DEM coupling method was used to analyze the flow patterns inside the slot and the movement patterns of blockages on the sieve surface, confirming the effectiveness of vortex guided blockage removal. Finally, a prototype was designed and built for testing, and the results showed that when the wind speed of the fan was 11.5 m/s, the grain impurity rate was 1.35%, the grain loss rate was 2.13%, and the average sieve blockage rate was ≤0.1%. All indicators were better than traditional cleaning devices and could meet the cleaning requirements. During the continuous operation of the spiral step cleaning device, performance indicators such as sieve hole blockage rate remained basically unchanged.

Reconfiguration of distribution network-based wind energy resource allocation considering time-varying load using hybrid optimization method

This study proposed a method for optimizing a radial distribution network by integrating wind turbine allocation, considering fluctuating load demands, through the use of a hybrid Grey Wolf Optimizer-Genetic Algorithm (HGWOGA). This approach aims to decrease the network’s energy loss costs. By incorporating genetic algorithm techniques, the method enhances the Grey Wolf Optimizer’s efficiency, speeding up convergence and avoiding local optima. The strategy determines the network’s open lines and the placement and capacity of wind turbines, adhering to radiality and operational constraints. It categorizes load levels into residential, commercial, and industrial, providing a comprehensive analysis of energy losses and their cost implications under various scenarios, including constant and dynamic loads. The study suggests that managing time-varying demand offers a more accurate depiction of network challenges, enabling effective reconfiguration throughout different demand phases. Moreover, HGWOGA demonstrates its ability to find the global optimum efficiently, even with reduced population sizes—a feat not achievable with the Grey Wolf Optimizer alone. Comparative analyses reveal HGWOGA’s effectiveness in curbing network energy loss costs better than previous methodologies. By simultaneously applying network reconfiguration and wind turbine allocation, as opposed to merely reconfiguring the network, this approach notably reduces power loss, diminishes the cost of losses, and enhances the voltage profile. This synergistic strategy leverages the dynamic allocation of wind turbines within the network, optimizing energy flow and distribution efficiency, thereby offering a substantial improvement over conventional network reconfiguration methods.

Enhancing Damage Detection in 2D Concrete Plates: A Comprehensive Study on Interpolation Methods and Parameters

In an era marked by increasing demands for stability and durability in construction, the importance of damage detection in concrete structures cannot be overstated. As these structures underpin the safety and longevity of vital assets, this paper embarks on a comprehensive exploration of methodologies to enhance precision and reliability in 2D concrete plate damage detection. By focusing on the interpolation of damage index values and leveraging the insights gained from energy loss analysis and the characterization of the time of arrival of signals, we address the pressing need for improved non-destructive damage detection techniques. Our study encompasses a range of simulation attempts, each involving various interpolation parameters, and systematically evaluates their performance. The culmination of this research identifies the most effective combination of techniques and parameters, leading to the best results in damage detection. This multidimensional investigation promises to provide valuable contributions to the field of structural health monitoring, benefiting both researchers and practitioners engaged in the evaluation of concrete structures.