Energy Loss Analysis Research Articles

Analysis of energy losses in a hydraulic load sensing proportional valve

The paper presents modeling and simulation of a hydraulic proportional valve PVG 32 by Danfoss widely used in agricultural machinery. A suitable mathematical model is created in LMS Amesim and SolidWorks Flow simulation software programs with the analysis of its energy performance. Their outcomes are validated with the experimental results to correctly describe the real valve characteristics. Since the spool valves are designed with overrunning loads in mind, considerable throttling losses are observed in the discharge line when the machine is operating with a resistive load.Therefore; this paper suggests the possibility of implementing energy saving techniques in the valve by using independent metering and gives simulation model for further use.

Low temperature growth of Beryllium Oxide thin films prepared via plasma enhanced atomic layer deposition

Beryllium oxide (BeO) is a unique metal oxide that exhibits high thermal conductivity and a high dielectric constant, even though it has a large bandgap energy. These characteristics can potentially address the electromagnetic issues associated with contemporary nanoscale electronic devices. However, BeO is mainly used as a heat-dissipating and refractory layer in sintering powders. To extend the use of BeO in semiconductor front-end-of-line processes, we developed nanoscale BeO thin films by using state-of-the-art atomic layer deposition (ALD). The physical and electrical properties of the BeO thin films were evaluated by introducing O2 plasma and H2O vapor as oxidation sources for the ALD process. A controlled plasma-enhanced ALD (PEALD) process led to the production of c-axis grown crystalline wurtzite BeO (002) films with a high growth rate per cycle at low substrate temperatures. The plasma energy was found to be adequately compensate for the high substrate temperature required for thermal ALD (ThALD). The bandgap energy (7.9 eV), calculated via inelastic energy loss analysis, and the dielectric constant (8.75) and breakdown voltage (10.3 MV/cm), obtained from MOS capacitors, are optimal for nanoscale electronic device applications.

Analysis of mechanical energy losses in marine diesels

The object of research is marine diesel engine oils, which provide lubrication, cooling and separation of friction surfaces. The subject of the research is the process of ensuring minimum mechanical losses in marine diesel engines. A problematic point in ensuring the lubrication of the cylinder-piston group and motion bearings is the lack of analytical and experimental studies that establish the relationship between the structural characteristics of engine oils and mechanical losses arising in marine internal combustion engines. The degree of orientational ordering of molecules and the thickness of the boundary lubricating layer are considered as the structural characteristics of engine oils. The determination of these values was carried out using the optical method based on the anisotropy of the light absorption coefficient by the boundary lubricant layer and the isotropic volume of the liquid (engine oil). The assessment of the level of mechanical losses arising in marine diesel engines was carried out according to an indirect indicator – the overshoot of the rotational speed and the time to reach the steady state of operation in the event of a change in load. It has been experimentally established that for engine oils used in marine internal combustion engines, the thickness of the boundary layer can be 15–17.5 µm. Motor oils, which are characterized by a higher ordering of molecules and a thickness of the boundary lubricant layer, ensure the flow of transient dynamic processes with less overshoot and a shorter transient time. This ensures the level of minimal mechanical losses occurring in marine diesel engines. The technology for determining the structural characteristics of engine oils can be used for any type and grade of oil (mineral or synthetic; high or low viscosity; used in both circulating and cylinder lubrication systems). The method of indirect assessment of mechanical losses of marine diesel engines can be used for any types of internal combustion engines of ships of sea and river transport (low-, medium- and high-speed; as well as performing the functions of both main and auxiliary engines).

Investigation on the impeller-diffuser interaction on the unstable flow in a mixed-flow pump using a modified partially averaged Navier-Stokes model

In this paper, the effect of the impeller-diffuser interaction on the unstable flow in a mixed-flow pump operating under one part-load condition is investigated based on the local energy loss analysis using a modified SST k-ω partially averaged Navier-Stokes (MSST PANS) model. The comparison on the pump performance shows a good agreement between the experiment and simulation. The characteristic curve of the test pump presents a positive slope region, where hydraulic loss increases 90.75% in the impeller and 16.75% in the diffuser. The internal flow analysis depicts that the rotating stall evolution captured in the impeller passages involves larger energy transfer while the separating flow in the diffuser passage involves lower energy transfer. As the impeller blade tailing edge (TE) begins to interact with the diffuser blade leading edge (LE), the vortex attached to the impeller blade TE is cut off into two parts, one of which keeps propagating circumferentially and forms the rotating stall in the impeller, and the other is regarded as the shedding vortex, moving into the diffuser. Further analysis by the Fast Fourier Transform and proper orthogonal decomposition reveals the frequency of rotating stall is 1.49fn, and the frequency of the shedding vortex is 0.53fn.

Performance Characteristics and Energy Loss Analyses of a High-Speed Centrifugal Pump with Straight Blades

Along with the rapid growth of cutting-edge petrochemical technology and the pressing demand for efficiency improvement, evaluation of the performance characteristics of high-speed pump is becoming increasingly important. In this paper, numerical simulation is presented on the flow instability of a 16 straight-blade high-speed centrifugal pump with flow rate of 3 m3/h and rotating speed of 8500 rpm. Combined with the analysis of flow stability, the entropy production method is introduced to evaluate regions of high mechanical energy loss and its distribution at different flow rates. Results show that approximately 96% of the energy loss of the pump is produced in the volute, gap, and front and back chambers. Large energy loss is observed near the trailing edge of the blade and volute tongue, which are caused by the small region including both the high and low pressure gradients and large momentum exchange by the flow separation, respectively. Moreover, the rotor–stator interaction causes much energy loss at the wall of the volute and front and back chambers. Owing to the circumferential pressure gradient and the 90° leading edge of the straight blade, the fluid tends to form counter-rotating recirculation vortices. The large number of blades narrows the passage and limits the formation of large vortices in flow channels, thus the backflow phenomenon seems not to worsen with the rise of flow rates. Hence, the entropy production in most of the flow parts are insensitive to flow rates.

Static hysteresis modeling for grain-oriented electrical steels based on the phenomenological concepts of energy loss mechanism

This paper proposes an advanced approach to construct static hysteresis loop of Grain-Oriented (GO) electrical steels for dynamic modeling and energy loss analysis. The proposed approach is in line with the magnetic hysteresis and phenomenological concepts of rate-dependent and rate-independent energy loss components of ferromagnetic materials under time-varying magnetic fields. The proposed method can predominantly describe energy loss mechanism and magnetization processes of the material. Accuracy of this technique was validated on Epstein size laminations of 3% GO silicon steels. The results explicitly confirmed the effectiveness of the proposed method in dynamic hysteresis modeling of GO electrical steels at magnetizing frequencies up to 1 kHz and peak flux densities up to 1.7 T.

Effects of Bionic Volute Tongue Bioinspired by Leading Edge of Owl Wing and Its Installation Angle on Performance of Multi-Blade Centrifugal Fan

Effect of the volute tongue of the multi-blade centrifugal fan on the performance of the machines is significance. The shape and installation angle of the volute tongue affect the circulating internal flow behavior of the volute as well as the energy loss around the volute tongue. In this study, the profile of the leading edge of the owl wing is applied to the volute tongue of a multi-blade centrifugal fan to improve the aerodynamic performance of the fan. The fan models with different volute tongue installation angles are numerically simulated under different flow conditions. The research results show that the proposed design is able to improve the aerodynamic performance of the fan at different flow rate conditions. In addition, an improved method for quantitatively evaluating the level of impeller-volute tongue interaction based on the unsteady simulation result is proposed and it is verified to be effective. Furthermore, the two parameters for evaluating the internal flow circulation which are influenced by the installation angle of the bionic volute tongue are analyzed, namely the recirculated flow coefficient and the reversed flow coefficient. Combined with the analysis of energy loss around the volute tongue, the mechanism of variation of the aerodynamic performance of the multi-blade centrifugal fan with different volute tongue installation angles is explained.

Multi-Point-of-View Energy Loss Analysis in a Refuse Truck Hydraulic System

In recent years, much research has focused on reducing the power consumption of mobile hydraulic machines due to rising fuel costs, regulations on combustion engine emissions and the need to reduce the size and weight of the storage devices in hybrid drives. Current approaches to improve the energy efficiency of a hydraulic system can be classified into four basic groups: reduction of the energy demand, recovery of part of the supplied energy (ERS systems), regeneration of part of the supplied energy and reuse of the recovered and regenerated energy (hybrid systems). Today’s mobile hydraulic systems are often complex, perform different tasks and work under different load conditions, which makes it difficult to analyse energy losses. A study of the energy losses of a hydraulic system from different points of view, such as an energy balance for a complete machine cycle, an analysis of the individual cycle phases and a power analysis for the different operation quadrants of the actuators, can give an global picture of the energy losses, being very useful to rate its energy efficiency, identify main power losses and decide which of the different energy-saving techniques to apply. This paper describes the data collection process, its analysis from various points of view and the summary of the results in easy to understand charts as useful tools to identify and quantify the main energy losses. Only system architecture losses are considered. Losses in the ICE engine or the electric motor, hydraulic pump losses and mechanical losses are outside the scope of this study.

Triplet exciton formation for non-radiative voltage loss in high-efficiency nonfullerene organic solar cells

<h2>Summary</h2> Nonfullerene acceptor (NFA) organic solar cells (OSCs) with power conversion efficiency (PCE) reaching up to 18% has shown tremendous potential toward practical applications. However, the non-radiative recombination loss in high-efficiency NFA OSCs is evidently large, and the origin remains unclear. Herein, by combining transient absorption spectroscopy, photovoltaic characterization, and detailed energy loss analysis, we unambiguously show the formation of NFA triplet exciton from free carrier recombination as a main non-radiative recombination and energy loss channel. More importantly, in contrast to the previous energetics point of view, we show side-chain fluorination in high-efficiency NFA OSCs has little effect on charge transfer energy landscapes but efficiently inhibits charge recombination to NFA triplet excitons, leading to higher <mml:math><mml:mrow><mml:mi>V</mml:mi>OC</mml:mrow></mml:math> and PCE. Our findings provide a new view about energy loss in NFA OSCs and pave the way toward OSCs with lower <mml:math><mml:mrow><mml:mi>V</mml:mi>OC</mml:mrow></mml:math> loss and efficiency exceeding 20%.

Numerical and experimental exploration towards a 26% efficiency rear-junction n-type silicon solar cell with front local-area and rear full-area polysilicon passivated contacts

In this work, structure designs and the corresponding energy loss analysis are conducted to achieve the high-efficiency n-type rear-junction solar cells with polysilicon passivated contact. We focus on the front-side structure design of solar cells, considering that the primary efficiency loss of the conventional n-type polysilicon passivated contact cells with boron-diffusion emitter is from the front side. A well-designed rear-junction solar cell with front localized n-type and rear full-area p-type polysilicon passivated contacts is expected to overcome these problems. However, the efficiency of rear-junction solar cells is sensitive to the front-side electrode contact resistivity. To accurately assess the practically achievable efficiency that the current technology can reach, we develop a simple modified TLM with wet-chemical etching to measure the contact resistivity of the n-type polysilicon contact. This method does not require relatively expensive photolithography and reactive ion etching tools and is easy to be used. When the contact resistivity of the front-side localized n-type polysilicon contact reaches 0.002 Ω·cm2 with a saturation current density of ~10 fA/cm2 in the front-side un-diffused area, the efficiency of the rear-junction n-type solar cell is expected to be ~26%, showing its potential for application in mass-production of high-efficiency crystalline silicon solar cells.

Phase analysis of hydrogen contained Zr-2.5wt%Nb CANDU pressure tube using plasmon energy loss analysis

Canada Deuterium Uranium (CANDU) reactors use Zr-2.5Nb alloys as the pressure tube material. Ensuring optimal performance of Zr-2.5Nb pressure tubes is vital to the safety of CANDU-type heavy water reactors. Long-term use of the pressure tube induces hydrogen pickup and hydride precipitation, causing delayed hydride cracking. Therefore, to evaluate the mechanical integrity of the pressure tube, it is critical to determine the phase distributions inside the pressure tube during hydrogen charging. This study focuses on visually expressing the hydride phasesusingscanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS).By using EELS, two phase characterization possibilities were noted at the phase boundary between α-Zr and δ-hydride: nucleated β-Zr and γ-hydride and a mechanical mixture of α-Zr and δ-hydride. The first characterization possibility was reported previously by Barrowet al., and the second possibility is described comprehensively in this paper.

A new prediction method for dust explosion venting at high static activation pressures

Venting is an effective way to prevent harmful dust explosions, but the existing prediction methods are imprecise and are suitable only for applications with low activation pressures. A new method is proposed for predicting pressures based on an analysis of energy losses at high activation pressures and verified by aluminum dust explosion experiments. Compared with the experimental results, the results of the new model are relatively stable under working conditions with different activation pressures and venting areas. Based on the analysis of energy losses, the changes in the energy loss rate, temperature, and venting velocity during venting are found to be asynchronous. The thermal energy loss, which accounts for over 80 percent of the total, is expected to be larger than the kinetic energy loss. The thermal energy loss rate changes rapidly during venting, while the kinetic energy loss rate remains relatively stable. The new model is more accurate than the NFPA68 standard, which fails to consider the thermal energy loss. Neglecting the thermal energy loss may result in an underestimation of the pressure reduction; this error increases with decreasing activation pressure.

Optical Excitations with Electron Beams: ChallengesandOpportunities.

Free electron beams such as those employed in electron microscopes have evolved into powerful tools to investigate photonic nanostructures with an unrivaled combination of spatial and spectral precision through the analysis of electron energy losses and cathodoluminescence light emission. In combination with ultrafast optics, the emerging field of ultrafast electron microscopy utilizes synchronized femtosecond electron and light pulses that are aimed at the sampled structures, holding the promise to bring simultaneous sub-Å–sub-fs–sub-meV space–time–energy resolution to the study of material and optical-field dynamics. In addition, these advances enable the manipulation of the wave function of individual free electrons in unprecedented ways, opening sound prospects to probe and control quantum excitations at the nanoscale. Here, we provide an overview of photonics research based on free electrons, supplemented by original theoretical insights and discussion of several stimulating challenges and opportunities. In particular, we show that the excitation probability by a single electron is independent of its wave function, apart from a classical average over the transverse beam density profile, whereas the probability for two or more modulated electrons depends on their relative spatial arrangement, thus reflecting the quantum nature of their interactions. We derive first-principles analytical expressions that embody these results and have general validity for arbitrarily shaped electrons and any type of electron–sample interaction. We conclude with some perspectives on various exciting directions that include disruptive approaches to noninvasive spectroscopy and microscopy, the possibility of sampling the nonlinear optical response at the nanoscale, the manipulation of the density matrices associated with free electrons and optical sample modes, and appealing applications in optical modulation of electron beams, all of which could potentially revolutionize the use of free electrons in photonics.

Energy loss analysis of a large scale BIPV system for university buildings in tropical weather conditions: A partial and cumulative performance ratio approach

This paper evaluates and discusses the building-integrated photovoltaic (BIPV) system energy losses during the energy conversion process from sunlight into electricity. An approach based on partial performance ratio (P-PR) and cumulative performance ratio (C-PR) is used. The P-PR and C-PR are evaluated considering eight stages possible in the energy conversion stage in photovoltaic (PV) energy systems. A large-scale BIPV system is proposed by retrofitting the existing university buildings is investigated, and the observed results depict the impact of energy losses over the performance ratio decline. Results showed that the P-PR of the BIPV as per eight energy conversion stages varies between 85.6 and 100%. The C-PR varies between 74 and 100%, recording an overall system performance ratio (PR) of 74% under tropical weather conditions. The energy losses are varied within the range of −0.27 to −14.8% (−4 to −223 kWh/kWp) in different energy conversion stages. The total energy losses in the BIPV system account for 26% (−419 kWh/kWp). Based on the observations, reasons for various losses and their mitigation strategies are explored. Thus, we believe this study could provide useful information on the feasibility of considering retrofitting the university buildings with the BIPV modules.

Energy performance and loss analysis of 100 kWp grid-connected rooftop solar photovoltaic system

In the present work, simulation and energy analysis of a grid-tied 100 kWp solar photovoltaic power plant mounted on an institute's building rooftop in Bhopal city of India are carried out. The present study provides insight into the solar power plant's performance linked to the medium range grid under actual operating conditions in Central India. It is observed that the standard performance ratio and the capacity factor of the plant are 80.72% and 19.27% respectively. The average monthly energy produced is highest in April and lowest in July. Simulation results using different simulation tools have been compared and are shown to be in near agreement with the real calculated values. This plant set-up is expected to gain profit after a period of 5.9 years with a capacity to mitigate 136 tons of CO2 emission annually. Practical application: This study estimates the energy output, system losses and performance parameters for a 100 kWp rooftop grid connected solar photovoltaic system. This helps to check the feasibility of such a system at this location. Also the payback period and reduction in carbon footprint are calculated to highlight the economic and environmental benefits. This would attract public interest for installation of more such plants on rooftops of buildings in the near future.

Analysis of Irreversible Thermodynamic Losses in Emissive-Energy Harvesters Based on Photon Beams

An analysis of irreversible energy losses that happen upon emissive-energy conversion is presented in this article. For this, we show that in these converters, the total amount of entropy produced in the conversion is proportional to the number of emitted photons, which justifies their description as counterparts of thermophotovoltaic engines. In the last part of this article, using a model of low-intensity photon beams and the detailed balance principle, we show the effects of irreversibilities on the output power and efficiency of emissive-energy harvesters.

Smith-Purcell radiation based on the transmission enhancement of a subwavelength hole array with inner tunnels.

The use and control of the extraordinary optical transmission through subwavelength hole arrays has enormous application potential in photonic devices. In this paper, we propose a subwavelength hole array with inner tunnels, for which the Smith-Purcell radiation (SPR) with this enhanced transmission phenomenon in THz is excited when the transmission peak locates in the SPR band. The SPR is monitored using particle-in-cell simulations in order to analyze the mechanisms responsible for improving the radiation coherence. Analysis of the electron energy loss reveals that the proposed subwavelength hole array with inner tunnels outperforms a conventional subwavelength grating array with respect to SPR generation efficiency. As SPR plays a significant role in research on particle diagnosis and terahertz radiation sources, the performance of the proposed structure suggests that it has high application potential.

Energy loss analysis of the storage tank coil heating process in a dynamic thermal environment

Abstract With the increasing demand for crude oil reserves, storage tanks are being developed on a large scale, and heating energy consumption is gradually increasing. Hence, it is necessary to study energy utilization. The variable physical parameters of crude oil and dynamic thermal environment are considered to establish a coil heating theoretical model of a large crude oil storage tank. On this basis, according to the first and second laws of thermodynamics, the energy loss mechanism of the multiple links in the heating process is analysed. Moreover, the energy consumption evaluation index of the storage tank heating process is established, and the energy consumption mechanism accounting for the tank oil level, the coil heat flow density and the external environmental conditions for the heating process with different coil structures is proposed. The results reveal that the energy loss is affected by the external solar radiation and the dynamic change in the atmospheric temperature, which exhibits fluctuating and rising trends. The external heat loss discharged to the environment through heat dissipation is far lower than the internal heat loss of the tank. Among the different coil structures, an integral large vortex structure is formed for a serpentine coil, with the bottom coil acting as the power element. This large-scale vortex structure obtains energy from time-averaged flow through turbulent shear, which promotes the heat transfer process of natural convection. Additionally, each coil provides a certain buoyancy to the crude oil, and the heat absorption of the crude oil accelerates; thus, the crude oil has a high and stable effective energy utilization degree.

Fundamentals and Prospects of Catalysis (Catalysis: Current and Future Developments – Volume 1)

The homogeneity of hydrogen termination on single-crystal CVD diamond surfaces exposed to air was studied with a new approach that encloses a combination of sheet resistance measurements, performed using four-point-probe method in Van Der Pauw configuration, and electron reflectivity measurements performed at intermediate kinetic energy to derive surface sensitive information on the chemical terminations (inelastic mean free path <0.8 nm). The coherence between the 2-dimensional spatial distributions of sheet resistance and electron reflectivity maps, as well as their similar dynamic range and consistency with an electron energy loss analysis, demonstrates that the proposed combined approach allows for a reliable and easy evaluation of both the effectiveness and homogeneity of the hydrogen-termination process of a diamond surface.

Combined electrical resistivity-electron reflectivity measurements for evaluating the homogeneity of hydrogen-terminated diamond surfaces

The homogeneity of hydrogen termination on single-crystal CVD diamond surfaces exposed to air was studied with a new approach that encloses a combination of sheet resistance measurements, performed using four-point-probe method in Van Der Pauw configuration, and electron reflectivity measurements performed at intermediate kinetic energy to derive surface sensitive information on the chemical terminations (inelastic mean free path <0.8 nm). The coherence between the 2-dimensional spatial distributions of sheet resistance and electron reflectivity maps, as well as their similar dynamic range and consistency with an electron energy loss analysis, demonstrates that the proposed combined approach allows for a reliable and easy evaluation of both the effectiveness and homogeneity of the hydrogen-termination process of a diamond surface.