Total Energy Loss Research Articles

Energetics of spreading droplets and role of capillary waves at low Weber numbers below 10

In this study, we investigate the energy conversion and dissipation mechanisms of spreading droplets on a solid surface at a low Weber number regime, which neither conventional energy-balance-based theories nor empirical scaling laws can completely explain. The energetic analysis presented in this study shows that on a hydrophilic surface, the actual primary energy source driving the spreading process is the initial surface energy not the initial kinetic energy. The conventional energy-balance-based approaches are found to be valid only for the spreading process on a hydrophobic surface. Particular attention is also paid to the roles of the capillary waves. The capillary waves are found to play significant roles in all of the important flow physics, that is, the interfacial structure, the oscillatory motions and the rapid collapse of the liquid film, the onset of the viscous regime, and the energy loss mechanism. It is also shown that the energy dissipation caused by the capillary-wave-induced phenomena can be estimated to be 25%–35% and 55%–65% of the total energy loss for a hydrophilic and a hydrophobic surface, respectively, at the low Weber number regime.

Equipment Maintenance Effect on Energy Losses Reduction at Medium Voltage Distribution Network

The energy loss is one of primary problems at medium voltage distribution network. The declining quality of distribution network equipment is main factor of energy losses. The equipment maintenance has a significant correlation with energy losses reduction. This research discussed the effect of equipment maintenance on energy losses reduction at medium voltage distribution network. The research object was a feeder of 20 kV medium voltage overhead line at Bontoala Substation, Makassar. The research method was the quantitative calculation of energy losses in a month based on empirical formulas, with and without maintenance condition. The calculation was performed on three distribution network equipment: connector, transformer, and insulators. Based on the calculation results, the total energy losses without maintenance were 118,373.429 kWh. With maintenance, the value of losses can be reduced to 36,960.339 kWh or equal with 68.776% reduction. The research result shows the significant impact on equipment maintenance to distribution network energy losses.

Photovoltaic-based Distributed Generation Allocation in Distribution Network for Energy Loss Minimization

Nowadays, there is a global consensus that integrating renewable energy sources (RESs) is highly needed to meet the increasing electricity demand and reduce the overall carbon footprint of energy production. However, large-scale integration of RES-based distributed generation (DG) units often poses several technical challenges in the system from stability, reliability, and power quality perspectives. However, these problems are usually mitigated by the optimal integration of DG units in the distribution networks (DNs). In this regard, the optimal sizing and placement of the DGs are crucial. Otherwise, network performance will deteriorate. This paper proposes to apply a novel population-based technique called the dung beetle optimization (DBO) algorithm for the optimal allocation of Photovoltaic (PV) based DG units to minimize total active energy loss subject to equality and inequality constraints in the DN. A DBO is inspired by the behaviours of dung beetles, including ball-rolling, dancing, foraging, stealing, and reproducing. A standard 33-bus system has been used to demonstrate the proposed method's effectiveness. The simulation results and comparison with other techniques demonstrate our proposed approach's significant energy loss reduction and a suitable voltage profile.

Optimal Sizing and Sitting of Distributed Generation in Distribution Network considering Power Generation Uncertainty

This paper presents an application of the recent metaheuristic Geometric Mean Optimizer (GMO) for the allocation of renewable energy sources (RES), including wind turbine (WT) and biomass-based Distributed Generation (DG) units in the distribution network (DN). The primary objective function is to minimize the total power and energy losses. The Weibull probability distribution function (PDF) is employed to describe the uncertainty of wind speed. The high penetration of RES with intermittent availability and demand variations has introduced many challenges to DN, such as power fluctuations, voltage rise, high losses, and low voltage stability. Therefore, the use of dispatchable biomass is considered to smooth out supply fluctuations and maintain supply continuity. A standard IEEE 69-bus test system is used to verify the performance of the proposed approach. The simulation results and comparison with other techniques demonstrate the significant energy loss reduction achieved by the proposed technique.

Enhancing Heavy Crude Oil Flow in Pipelines through Heating-Induced Viscosity Reduction in the Petroleum Industry

The process of transporting crude oil across pipelines is one of the most critical aspects of the midstream petroleum industry. In the present experimental work, the effect of temperature, pressure drop, and pipe diameter on the flow rate of heavy crude oil have been assessed. Moreover, the total discharge and energy losses have been evaluated in order to demonstrate the improvements potentially achievable by using solar heating method replacing pipe, and adjusting the value of the initial pressure difference. Crude oil of API = 20 has been used for the experiments, with the studied pipelines sections connecting the separator unit to the storage tank operating at a temperature of 25°C–100°C, pressure drop of 3, 4, 5, and 6 kg/cm², and with pipe diameter of 4, 6, and 8 in. The results show that on increasing the temperature and/or the pressure drop, the flow rate through the pipeline becomes higher, thus raising the total pumping energy (as the pipe diameter increase), while energy losses increase from the last separator to the storage tank in the field. A pipe diameter increase can also produce a growth of the total pumping energy (i.e., energy losses increase). The results of the present analysis suggest that employing an optimal temperature (50°C) is needed to ensure good performance.

A Novel 4H-SiC Double Trench MOSFET with Built-In MOS Channel Diode for Improved Switching Performance

This study proposed a novel 4H-SiC double trench metal-oxide-semiconductor field-effect-transistor (DTMCD-MOSFET) structure with a built-in MOS channel diode. Further, its characteristics were analyzed using TCAD simulation. The DTMCD-MOSFET comprised active and dummy gates that were divided horizontally; the channel diode operated through the dummy gate and the p-base and N+ source regions at the bottom of the dummy gate. Because the bult-in channel diode was positioned at the bottom, the DTMCD-MOSEFT minimized static deterioration. Despite having a 5.2% higher specific on-resistance (Ron-sp) than a double-trench MOSFET (DT-MOSFET), the DTMCD-MOSFET exhibited a significantly superior body diode and switching properties. In comparison to the DT-MOSFET, its turn-on voltage (VF) and reverse recovery charge (Qrr) were decreased by 27.2 and 30.2%, respectively, and the parasitic gate-drain capacitance (Crss) was improved by 89.4%. Thus, compared with the DT-MOSFET, the total switching energy loss (Etot) was reduced by 41.4%.

A novel combo‐transmission system of cold energy and electricity for aluminium profile production: Using liquid nitrogen and superconductor technologies

AbstractAluminium production needs the most energy‐intensive technologies among all the metal processing sectors. During the process of aluminium profile extrusion, the whole production line needs bulk electricity, and the mold inside the extrusion equipment needs robust cold energy for rapid cooling of the metal surface. This paper presents a new combo‐transmission that can simultaneously deliver cold energy together with electricity to the aluminium profile extrusion line. Thanks to the superiority of virtually zero loss and compact size, the powerful superconducting cable is used to replace the conventional copper cable. The entire superconducting cable assembly is fully installed into a cryogenic pipeline and cooled by liquid nitrogen at 77 K. In addition to keeping a favourable cryogenic environment for the superconducting cable, liquid nitrogen can also provide a large amount of cold energy for cooling the metal surface. For a typical 100 MN aluminium extrusion production line, the design and optimization of 10 kA class superconducting cable with the pipeline cooling system for aluminium production are presented in detail. The simulation results and comparisons show that the total energy loss of superconducting transmission is about 46% of conventional copper cable, and the energy saved in a year can be up to about 240.6 MWh. Moreover, the net profit increases almost linearly along with the increases of the extrusion speed when the liquid nitrogen cooling is applied to the 100 MN production line. For the case of 23% increase in extrusion speed, the net profit can be up to 1.48 M$ in a year. Overall, the novel design, technical evaluation, and economic analysis of the combo‐transmission system (cold energy + electricity) can provide a promising solution for future high‐dense aluminium production sectors.

Two-Stage Optimal Active-Reactive Power Coordination for Microgrids with High Renewable Sources Penetration and Electrical Vehicles Based on Improved Sine−Cosine Algorithm

As current global trends aim at the large-scale insertion of electric vehicles as a replacement for conventional vehicles, new challenges occur in terms of the stable operation of electric distribution networks. Microgrids have become reliable solutions for integrating renewable energy sources, such as solar and wind, and are considered a suitable alternative for accommodating the growing fleet of electrical vehicles. However, efficient management of all equipment within a microgrid requires complex solving algorithms. In this article, a novel two-stage scheme is proposed for the optimal coordination of both active and reactive power flows in a microgrid, considering the high penetration of renewable energy sources, energy storage systems, and electric mobility. An improved sine-cosine algorithm is introduced to ensure the day-ahead optimal planning of the microgrid’s components aiming at minimizing the total active energy losses of the system. In this regard, both local and centralized control strategies are investigated for multiple generations and consumption scenarios. The latter proved itself a promising control scheme for the microgrid operation, as important energy loss reduction is encountered when applied.

Multi-Objective Hybrid Optimization for Optimal Sizing of a Hybrid Renewable Power System for Home Applications

An optimal energy mix of various renewable energy sources and storage devices is critical for a profitable and reliable hybrid microgrid system. This work proposes a hybrid optimization method to assess the optimal energy mix of wind, photovoltaic, and battery for a hybrid system development. This study considers the hybridization of a Non-dominant Sorting Genetic Algorithm II (NSGA II) and the Grey Wolf Optimizer (GWO). The objective function was formulated to simultaneously minimize the total energy cost and loss of power supply probability. A comparative study among the proposed hybrid optimization method, Non-dominant Sorting Genetic Algorithm II, and multi-objective Particle Swarm Optimization (PSO) was performed to examine the efficiency of the proposed optimization method. The analysis shows that the applied hybrid optimization method performs better than other multi-objective optimization algorithms alone in terms of convergence speed, reaching global minima, lower mean (for minimization objective), and a higher standard deviation. The analysis also reveals that by relaxing the loss of power supply probability from 0% to 4.7%, an additional cost reduction of approximately 12.12% can be achieved. The proposed method can provide improved flexibility to the stakeholders to select the optimum combination of generation mix from the offered solutions.

Study on the trajectory of tip leakage vortex and energy characteristics of mixed-flow pump under cavitation conditions

To investigate the mechanism of tip leakage vortex (TLV) and energy loss caused by pump cavitation. The SST k-ω turbulence model coupled with the Reynolds-averaged Navier-Stokes equations, combined with the homogeneous flow cavitation model is employed. And the accuracy of the numerical simulation is verified experimentally. The results show that the cavitation intensity seriously affects the load distribution on suction side (SS), and the variation pattern of the low-pressure area distribution on SS is related to the cavitation location. As cavitation deteriorates, the working capacity of the impeller is weakened and the guide vane is also affected, resulting in a sharp drop in the energy performance of the pump. The malignant cavitation becomes the main reason for the decreasing head and unstable operation of the mixed flow pump. Cavitation deterioration reduces the output power of the impeller, and the power distribution characteristics are affected by the degree of cavitation. Malignant cavitation leads to increased frictional and turbulent dissipation losses and increased total energy loss, resulting in a decrease in the effective energy obtained, leading to a decrease in the overall pump performance. The results can provide theoretical reference for improving the cavitation performance of the pumps.

Entropy production analysis of a radial inflow turbine with variable inlet guide vane for ORC application

The fluctuation of heat source conditions leads to the off-design operation and efficiency reduction of the radial inflow turbine (RIT). The adjustment of the outlet angle of inlet guide vane (IGV) is an important way to improve the turbine performance under off-design conditions. Since the energy dissipation caused by friction and flow separation is the main reason for the reduction of RIT efficiency, the entropy production analysis method is used to diagnose the location with high local energy loss in the RIT and evaluate its total energy loss under different working conditions in this paper. Firstly, an appropriate outlet angle of the IGV is determined according to the inlet pressure and outlet pressure of the RIT in organic Rankine cycle (ORC). Then, the effects of inlet pressure and outlet pressure on its energy loss are studied. The results indicate that the average entropy production rate (EPR) of the rotor in the RIT is the highest, which is mainly from the tip clearance and the inlet region. More than 70% of total entropy production of the turbine comes from the rotor, followed by the diffuser. The turbine can achieve lower total entropy production at higher outlet pressure or lower inlet pressure. Compared with a fixed IGV, the turbine with variable IGV can achieve higher turbine efficiency and output power under off-design conditions. The maximum increase in the efficiency and output power of the turbine with variable IGV under different inlet pressures is 3.8% and 12.9%, respectively.

Quantifying the effect of energetic disorder on organic solar cell energy loss

•Correlation between non-radiative energy loss and CT-state energetic disorder •D-A interface optimization strategy for reduced non-radiative energy loss •Universal energy loss metric incorporating disorder Understanding the factors affecting energy loss in organic photovoltaics (OPVs) is imperative to achieve further improvements in their efficiency and to establish design rules for the development of new materials. Here, we provide direct experimental evidence supporting correlation between charge-transfer (CT) state static disorder and energy loss. Specifically, upon studying several planar and bulk heterojunction solar cells, we demonstrate that the non-radiative energy loss component quadratically increases with increasing Gaussian CT-state disorder. We also show that by defining the total energy loss in terms of the peak of the CT-state distribution, obtained from temperature-dependent external quantum efficiency measurements, the effect of disorder on OPV performance can be unambiguously identified, offering a universal metric for quantifying energy loss across various devices. Understanding the factors affecting energy loss in organic photovoltaics (OPVs) is imperative to achieve further improvements in their efficiency and to establish design rules for the development of new materials. Here, we provide direct experimental evidence supporting correlation between charge-transfer (CT) state static disorder and energy loss. Specifically, upon studying several planar and bulk heterojunction solar cells, we demonstrate that the non-radiative energy loss component quadratically increases with increasing Gaussian CT-state disorder. We also show that by defining the total energy loss in terms of the peak of the CT-state distribution, obtained from temperature-dependent external quantum efficiency measurements, the effect of disorder on OPV performance can be unambiguously identified, offering a universal metric for quantifying energy loss across various devices.

Pitch stability control of variable wheelbase 6WID unmanned ground vehicle considering tire slip energy loss and energy-saving suspension control

Acceleration on a ramp and emergency braking are common driving conditions for special vehicles. Due to the complex coupling between the suspension and the chassis structure, the body attitude maintenance and stability control face huge challenges. Aiming at the control problem of pitch stability of the existing six-wheel independent drive unmanned vehicle (6WID UGV) with variable wheelbase during acceleration and deceleration, this paper designs an interconnected active hydro-pneumatic suspension (IAHPS) that can autonomously adapt to the change of wheelbase. Based on this system, a pitch stability control strategy considering the lowest energy consumption of the chassis is proposed. Firstly, a PID-type sliding mode controller (SMC) is used in the upper controller to calculate the desired anti-pitching torque. The disturbance caused by the nonlinearity and uncertainty of the model is estimated by the extended state observer (ESO). Secondly, with the goal of minimizing the energy consumption of the suspension system, the PSO algorithm is used in the middle controller to decide the pressure of the two accumulators in IAHPS. Thirdly, the lower controller again uses the PSO algorithm to achieve wheel torque distribution to minimize tire slip energy loss; Finally, simulation tests in multiple scenarios verify the effectiveness of the designed layered control strategy in terms of the pitching stability control. Under random road and horizontal road, the energy consumption for active adjustment of suspension is reduced by 28.35% and 29.41% respectively; The total energy loss of tire slip is reduced by 65.16% and 41.52%.

Numerical Study of the Energy Flow Characteristics of Multi-Stage Pump as Turbines

Multi-stage pump as turbine (PAT) has a wider range of heads and application intervals compared to single-stage PAT. In our research, we have conducted experimental and numerical simulation studies on this issue. In this paper, based on experimental research, numerical simulation is applied to calculate the multi-stage PAT flow field. The flow characteristics of multi-stage PAT under different working conditions are studied using the entropy production theory. Finally, the Pearson correlation coefficient is used to evaluate the relationship between the hydraulic loss and entropy production of the impellers and guide vanes. The entropy production theory is used to determine the location where the multi-stage PAT energy loss occurs compared with the traditional pressure drop assessment method. The results show that the trend of the numerical simulation results is consistent with the experimental results. The energy loss in the multi-stage PAT is calculated combined with the impeller and guide vane which accounts for 69.1–73% of the total energy loss under all flow conditions. The total entropy production rate of each component under design flow conditions is listed in decreasing order: impeller, guide vane, front and back chamber, a balance disk, and inlet and outlet volute. The first stage component has a larger energy loss compared with the rest of the stages. The magnitude of energy loss is closely related to physical quantities such as flow field velocity and skin friction coefficient. Furthermore, the distribution of streamlines and vortex cores at the impellers reflects that flow domain stability increases from the first stage impeller to the fifth stage impeller. The correlation between entropy production and hydraulic loss was evaluated by the Pearson correlation coefficient. Therefore, using the entropy production theory can effectively identify the characteristics of the flow field and the location of energy losses. It provides a reference for the targeted optimization of multi-stage PAT.

Effects of Clearance and Operating Conditions on Tip Leakage Vortex-Induced Energy Loss in an Axial-Flow Pump Using Entropy Production Method

Abstract Tip leakage flow (TLF) is a typical flow phenomenon in the internal flow of axial-flow pumps that has a serious impact on their safety and stability. In this study, numerical simulations are performed to investigate the influence of various tip clearances and operating conditions on the characteristics of the tip leakage vortex (TLV) and energy loss of a prototype of a vertical axial-flow pump. First, based on entropy production theory, the TLV-induced energy loss is quantitatively studied. The entropy production rate caused by turbulence dissipation (EPTD), which is caused by pulsating velocity, contributes the most to the total energy loss. The EPTD at the impeller is principally distributed on the leading edge of the blade due to the influence of the tip clearance. Then, the spatial shape and trajectory of the core of the TLV are discussed, and their correlations with pressure and vorticity are investigated to reveal the spatial distribution characteristics and formation mechanism of TLVs. With increasing tip clearance, the trajectory of the vortex core extends radially outward, and the low-pressure area near the blade tip is consistent with the trajectory of the core of the TLV, which accompanies high vorticity. Fundamentally, pressure gradients and flow separation at the leading edge are the root causes of the TLVs. Lastly, the spatial evolution of TLVs under different calculation schemes is discussed by utilizing the vorticity transport equation, demonstrating that the Coriolis force (CORF) is the main factor that affects the location of a TLV, whereas the vorticity stretching term (VST) has a greater influence on the vorticity variation rate of the TLV than the CORF and plays a predominant role in the spatial development of the TLF.

Iterative Dynamic Programming—An Efficient Method for the Validation of Power Flow Control Strategies

The operation of electrical networks, microgrids, or heterogeneous battery systems, especially the dispatch of single units within the system, requires sophisticated power flow control strategies. If objectives such as efficiency are demanded for the operation of the energy system, typical control strategies lack the ability to verify the optimality of the operation. Dynamic programming is a widely used method for determining the global optima of trajectory problems. In the context of energy systems and power flow optimization, it is restricted to applications with a low number of states and decisions. The reason for this is the rapid growth of computational effort with increasing dimensionality of the state and decision space. The approach of iterative dynamic programming (iDP) makes dynamic programming applicable to the planning and benchmarking of complex power flow optimization problems. To illustrate this, a heterogeneous battery energy storage system is introduced for which the iDP optimizes the power split at the point of common coupling to minimize the total cumulative loss of energy. The method can be adopted for a broad range of energy systems such as microgrids, utility grids, or electric vehicles. The applicability is limited only by the computation time, which depends on the model complexity and the length of the time series. To verify the functionality of the iterative dynamic programming, its results are directly compared to those of the standard dynamic programming. The total computation time can be reduced by 98% in the tested scenario. As relevant use cases, static and dynamic methods of power sharing are validated and benchmarked. The iDP offers a novel and computationally efficient method for the design and validation of power flow control strategies.

Energy Recovery and Utilization Efficiency Improvement for Motor-Driven System Using Dynamic Energy Distribution Method

The hybrid energy storage system with the battery as the main energy source and the supercapacitor as the auxiliary energy source has been widely applied in the motor-driven system. However, the uncoordinated distribution of energy between energy storage units would cause unnecessary energy loss in the system. The energy recovery and utilization efficiency of the system needs to be further improved. In this paper, a power tracking control strategy considering total energy loss is proposed. The energy flow path of the motoring or generating process is investigated. The energy loss prediction models of the battery, the supercapacitor and the bidirectional DC/DC converter are established, respectively. Afterward, the objective optimization control function is deduced from the perspective of the minimum comprehensive energy loss. Dynamic power distribution ratios are obtained under the constraints. The superiorities of the supercapacitor are fully utilized and the dynamic supply-demand power balance is maintained. The results of simulations and experiments verify that energy recovery and utilization efficiency of the system is increased by 26.4% using the proposed control strategy in one running cycle.

Effect of electron energy distributions on the electron density in nitrogen inductively coupled plasmas

The effect of the electron energy distribution function (EEDF) on the behavior of the electron density (n e) is investigated under various gas pressures of nitrogen (N2) in inductively coupled plasma (ICP) operated at low and high input powers. A Langmuir probe is used to measure the EEDFs and electron densities, and the antenna coil current is measured to obtain the absorbed power in the plasma (P abs). At gas pressures above 2.67 Pa (20 mTorr) and 2500 W, P abs increases continually with increasing the gas pressure, but the electron density slightly decreases. In this case, the EEDF has a Maxwellian distribution with a high-energy tail. On the other hand, at 300 W, P abs decreases slightly with increasing gas pressure, but the electron density dramatically decreases, and the EEDF evolves from a bi-Maxwellian to a non-Maxwellian distribution with substantially highly depleted high-energetic part (high-energy tail). To analyze the difference in the behavior of the decrease rate in electron density, the total energy loss per electron–ion pair lost (ε T) is measured through the probe diagnostics, and the measured electron density is compared with the calculated electron density from the global model. An additional experiment is performed in Ar plasma under the same discharge conditions as N2 plasma to compare the EEDF effect. This study provides experimental evidence that the EEDF has a decisive effect on the behavior of the electron density in plasmas.

Techno-economic assessment of soiling losses in CSP and PV solar power plants: A case study for the semi-arid climate of Morocco

Many sites suitable for photovoltaic (PV), concentrated solar power (CSP) or hybrid CSP/PV plants are located in the desert or arid and semi-arid areas, where they can suffer from soiling accumulation on the surfaces of solar collectors. The aim of this research is to assess the impact of soiling on the annual performance of CSP and PV solar power plants from a technical and economic perspective. The yield analysis of 1MWe linear Fresnel CSP and 1MWe PV solar power plant is performed under the semi-arid climate of Morocco. One year of ground-based and quality-checked meteorological data, as well as one year of soiling data collected from two soiling monitoring sensors (a Tracking Cleanliness Sensor (TraCS) and a DustIQ) are considered in the analysis. The optical soiling loss is 5 to 6 times higher in case of CSP compared to PV, with an annual average daily of 1.21 %/day and 0.24 %/day, respectively. The total annual energy loss due to soiling, considering a monthly cleaning frequency, is equivalent to 17.76 % and 1.95 % for CSP and PV, respectively. The energy loss depends not only on the optical efficiency drop due to soiling, but also on the available solar resources at the location. The LCoE increases significantly if the impact of soiling is accounted, especially for CSP technology. The analysis of the different cleaning profiles reveals that the cleaning frequency of 3 weeks gives the highest profitability for both PV and CSP solar plants.

Evidence of proton-proton correlations in the 116Sn+60Ni transfer reactions

One and two proton transfer channels have been measured in 116Sn+60Ni with the magnetic spectrometer PRISMA by making an excitation function at several bombarding energies, from above to well below the Coulomb barrier. The total kinetic energy loss distributions show the predominance of quasi-elastic processes in the sub-barrier regime. The data have been compared with calculations performed with the GRAZING program, based on semiclassical formalism, and in the Distorted Wave Born Approximation (DWBA), which provided a good theoretical description of the extracted transfer probabilities for the one proton transfers. The much larger values of the experimental two proton transfers compared with those evaluated within an independent particle transfer mechanism, indicate the presence of strong proton-proton correlations. The results complement the ones of the previously analyzed one- and two-neutron transfers, providing significant new information on the subject compared to past works.