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Showing records 899 to 923 of 1602. [First] Page: 1 33 34 35 36 37 38 39 40 41 Last
A Frequency Control Approach for Hybrid Power System Using Multi-Objective Optimization
Mohammed Elsayed Lotfy, Tomonobu Senjyu, Mohammed Abdel-Fattah Farahat, Amal Farouq Abdel-Gawad, Atsuhi Yona
July 26, 2019 (v1)
Keywords: frequency control, full-order observer, hybrid power system, multi-objective optimization, supply balance
A hybrid power system uses many wind turbine generators (WTG) and solar photovoltaics (PV) in isolated small areas. However, the output power of these renewable sources is not constant and can diverge quickly, which has a serious effect on system frequency and the continuity of demand supply. In order to solve this problem, this paper presents a new frequency control scheme for a hybrid power system to ensure supplying a high-quality power in isolated areas. The proposed power system consists of a WTG, PV, aqua-electrolyzer (AE), fuel cell (FC), battery energy storage system (BESS), flywheel (FW) and diesel engine generator (DEG). Furthermore, plug-in hybrid electric vehicles (EVs) are implemented at the customer side. A full-order observer is utilized to estimate the supply error. Then, the estimated supply error is considered in a frequency domain. The high-frequency component is reduced by BESS and FW; while the low-frequency component of supply error is mitigated using FC, EV and D... [more]
Effect on Torque and Thrust of the Pointed Tip Shape of a Wind Turbine Blade
Kyoungsoo Lee, Shrabanti Roy, Ziaul Huque, Raghava Kommalapati, SangEul Han
July 26, 2019 (v1)
Keywords: National Renewable Energy Laboratory (NREL) Phase VI, pointed tip blade, separation and transition, shear-stress-transport (SST) Gamma-Theta turbulent model, wind energy, wind turbine blade
This paper presents the effect of the tip shape of a wind turbine blade on aerodynamic forces, including the effects of separation, transition and stall. A National Renewable Energy Laboratory (NREL) Phase-VI wind turbine blade was used, in which the shape of the tip was modified to a pointed tip. Computational fluid dynamics (CFD) simulations were employed for the analysis and the results were compared with the original NREL blade CFD and experimental data using ANSYS CFX (Ansys Inc., Delaware, PA, USA). To predict the separation and separation-induced transition on both near wall and far away, the shear-stress-transport (SST) Gamma-Theta turbulent model was used. The stall onset of a 20° angle of attack and its effects were also analyzed and presented. The value of torque with the pointed tip blade was found to be 3%⁻8% higher than the original NREL blade showing the benefit of the pointed tip. Normal force coefficient is lower at the tip for the pointed tip blade, which results in l... [more]
Tie-Line Bias Control Applicability to Load Frequency Control for Multi-Area Interconnected Power Systems of Complex Topology
Chunyu Chen, Kaifeng Zhang, Kun Yuan, Xianliang Teng
July 26, 2019 (v1)
Keywords: load frequency control, ring network, tie-line bias control (TBC) applicability, topology
The tie-line bias control (TBC) method has been widely used in the load frequency control (LFC) of multi-area interconnected systems. However, it should be questioned whether the conventional TBC can still apply to LFC when considering the complication of structures of power systems. LFC, in essence, is to stabilize system frequency/tie-line power by controlling controlled outputs’ area control error (ACE). In this paper, relations between LFC control variables and controlled outputs are expressed as a system of equations, based on which an exemplary ring network is studied. Sufficient and necessary conditions for TBC applicability is presented, and a novel LFC mode is proposed for a general ring network where TBC cannot work. Finally, TBC applicability to multi-area systems with general topology is studied, and a general LFC mode is proposed for systems where TBC is not definitely applicable, thus rendering routines that may guide LFC design of future power systems with more complex t... [more]
A Mixed Logical Dynamical-Model Predictive Control (MLD-MPC) Energy Management Control Strategy for Plug-in Hybrid Electric Vehicles (PHEVs)
Jing Lian, Shuang Liu, Linhui Li, Xuanzuo Liu, Yafu Zhou, Fan Yang, Lushan Yuan
July 26, 2019 (v1)
Keywords: driving intention, mixed integer linear programming (MILP), mixed logic dynamical model, model predictive control (MPC), nonlinear auto-regressive (NAR) neural network
Plug-in hybrid electric vehicles (PHEVs) can be considered as a hybrid system (HS) which includes the continuous state variable, discrete event, and operation constraint. Thus, a model predictive control (MPC) strategy for PHEVs based on the mixed logical dynamical (MLD) model and short-term vehicle speed prediction is proposed in this paper. Firstly, the mathematical model of the controlled PHEV is set-up to evaluate the energy consumption using the linearized models of core power components. Then, based on the recognition of driving intention and the past vehicle speed data, a nonlinear auto-regressive (NAR) neural network structure is designed to predict the vehicle speed for known driving profiles of city buses and the predicted vehicle speed is used to calculate the total required torque. Next, a MLD model is established with appropriate constraints for six possible driving modes. By solving the objective function with the Mixed Integer Linear Programming (MILP) algorithm, the opt... [more]
Ensemble Prediction Model with Expert Selection for Electricity Price Forecasting
Bijay Neupane, Wei Lee Woon, Zeyar Aung
July 26, 2019 (v1)
Keywords: electricity price forecasting, ensemble model, expert selection
Forecasting of electricity prices is important in deregulated electricity markets for all of the stakeholders: energy wholesalers, traders, retailers and consumers. Electricity price forecasting is an inherently difficult problem due to its special characteristic of dynamicity and non-stationarity. In this paper, we present a robust price forecasting mechanism that shows resilience towards the aggregate demand response effect and provides highly accurate forecasted electricity prices to the stakeholders in a dynamic environment. We employ an ensemble prediction model in which a group of different algorithms participates in forecasting 1-h ahead the price for each hour of a day. We propose two different strategies, namely, the Fixed Weight Method (FWM) and the Varying Weight Method (VWM), for selecting each hour’s expert algorithm from the set of participating algorithms. In addition, we utilize a carefully engineered set of features selected from a pool of features extracted from the p... [more]
Detection of Internal Short Circuit in Lithium Ion Battery Using Model-Based Switching Model Method
Minhwan Seo, Taedong Goh, Minjun Park, Gyogwon Koo, Sang Woo Kim
July 26, 2019 (v1)
Keywords: battery safety, internal short circuit resistance, model updating method
Early detection of an internal short circuit (ISCr) in a Li-ion battery can prevent it from undergoing thermal runaway, and thereby ensure battery safety. In this paper, a model-based switching model method (SMM) is proposed to detect the ISCr in the Li-ion battery. The SMM updates the model of the Li-ion battery with ISCr to improve the accuracy of ISCr resistance R I S C f estimates. The open circuit voltage (OCV) and the state of charge (SOC) are estimated by applying the equivalent circuit model, and by using the recursive least squares algorithm and the relation between OCV and SOC. As a fault index, the R I S C f is estimated from the estimated OCVs and SOCs to detect the ISCr, and used to update the model; this process yields accurate estimates of OCV and R I S C f . Then the next R I S C f is estimated and used to update the model iteratively. Simulation data from a MATLAB/Simulink model and experimental data verify that this algor... [more]
Experimental Analysis and Full Prediction Model of a 5-DOF Motorized Spindle
Weiyu Zhang, Huangqiu Zhu, Hengkun Yang, Tao Chen
July 26, 2019 (v1)
Subject: Other
Keywords: experimental analysis, magnetic bearing, Modelling, prediction model, suspension force
The cost and power consumption of DC power amplifiers are much greater than that of AC power converters. Compared to a motorized spindle supported with DC magnetic bearings, a motorized spindle supported with AC magnetic bearings is inexpensive and more efficient. This paper studies a five-degrees-of-freedom (5-DOF) motorized spindle supported with AC hybrid magnetic bearings (HMBs). Most models of suspension forces, except a “switching model”, are quite accurate, but only in a particular operating area and not in regional coverage. If a “switching model” is applied to a 5-DOF motorized spindle, the real-time performance of the control system can be significantly decreased due to the large amount of data processing for both displacement and current. In order to solve this defect, experiments based on the “switching model” are performed, and the resulting data are analyzed. Using the data analysis results, a “full prediction model” based on the operating state is proposed to improve rea... [more]
An Optimal Augmented Monotonic Tracking Controller for Aircraft Engines with Output Constraints
Jiakun Qin, Jinquan Huang, Muxuan Pan
July 26, 2019 (v1)
Keywords: aircraft engines, genetic algorithms, min-max control, optimal augmented monotonic tracking control (OAMTC)
This paper proposes a novel min-max control scheme for aircraft engines, with the aim of transferring a set of regulated outputs between two set-points, while ensuring a set of auxiliary outputs remain within prescribed constraints. In view of this, an optimal augmented monotonic tracking controller (OAMTC) is proposed, by considering a linear plant with input integration, to enhance the ability of the control system to reject uncertainty in system parameters and ensure no crossing limits. The key idea is to use the eigenvalue and eigenvector placement method and genetic algorithms to shape the output responses. The approach is validated by numerical simulation. The results show that the designed OAMTC controller can achieve a satisfactory dynamic and steady performance and keep the auxiliary outputs within constraints in the transient regime.
Thermochemical Storage of Middle Temperature Wasted Heat by Functionalized C/Mg(OH)₂ Hybrid Materials
Emanuela Mastronardo, Yukitaka Kato, Lucio Bonaccorsi, Elpida Piperopoulos, Candida Milone
July 26, 2019 (v1)
Subject: Materials
Keywords: carbon nanotubes, exfoliated graphite, graphene oxide, magnesium hydroxide, thermochemical storage
For the thermochemical performance implementation of Mg(OH)₂ as a heat storage medium, several hybrid materials have been investigated. For this study, high-performance hybrid materials have been developed by exploiting the authors’ previous findings. Expanded graphite (EG)/carbon nanotubes (CNTs)-Mg(OH)₂ hybrid materials have been prepared through Mg(OH)₂ deposition-precipitation over functionalized, i.e., oxidized, or un-functionalized EG or CNTs. The heat storage performances of the carbon-based hybrid materials have been investigated through a laboratory-scale experimental simulation of the heat storage/release cycles, carried out by a thermogravimetric apparatus. This study offers a critical evaluation of the thermochemical performances of developed materials through their comparison in terms of heat storage and output capacities per mass and volume unit. It was demonstrated that both EG and CNTs improves the thermochemical performances of the storage medium in terms of reaction r... [more]
Thermal Analysis of a Solar Powered Absorption Cooling System with Fully Mixed Thermal Storage at Startup
Camelia Stanciu, Dorin Stanciu, Adina-Teodora Gheorghian
July 26, 2019 (v1)
Keywords: ammonia-water absorption cooling, fully mixed thermal storage, parabolic trough collector, solar energy
A simple effect one stage ammonia-water absorption cooling system fueled by solar energy is analyzed. The considered system is composed by a parabolic trough collector concentrating solar energy into a tubular receiver for heating water. This is stored in a fully mixed thermal storage tank and used in the vapor generator of the absorption cooling system. Time dependent cooling load is considered for the air conditioning of a residential two-storey house. A parametric study is performed to analyze the operation stability of the cooling system with respect to solar collector and storage tank dimensions. The results emphasized that there is a specific storage tank dimension associated to a specific solar collector dimension that could ensure the longest continuous startup operation of the cooling system when constant mass flow rates inside the system are assumed.
The Effect of the Angle of Inclination on the Efficiency in a Medium-Temperature Flat Plate Solar Collector
Orlando Montoya-Marquez, José Jasson Flores-Prieto
July 26, 2019 (v1)
Keywords: covered solar collectors, inclined solar collector, overall heat loss coefficient, tilt solar collector
In this experimental work, the effects of the inclination angle β and the (Ti − Ta)/G on the efficiency and the UL-value were investigated on a medium-temperature flat plate solar collector. The experiments were based on steady-state energy balance, by heat flow calorimetry at indoor conditions and considering the standard American National Standard Institute/American Society of Heating Refrigerating and Air Conditioning Engineers (ANSI/ASHRAE) 93-2010. The solar radiation was emulated by the Joule effect using a proportional integral derivative (PID) control considering two conditions of the absorber temperature, Case 1: (To − Ti) > 0, and Case 2: (To − Ti) = 0. The inclination angles were 0°⁻90° and the (Ti − Ta)/G were 0.044⁻0.083 m²·°C/W and 0.124⁻0.235 for Case 1 and Case 2, respectively. The variations of β and (Ti − Ta)/G cause efficiency changes up to 0.37⁻0.45 (21.6%) and 0.31⁻0.45 (45.0%), respectively, for Case 1. Also, the UL(β) reached changes up to 10.1⁻12.0 W/m²·°C (19.2... [more]
Stability Analysis and Stability Enhancement Based on Virtual Harmonic Resistance for Meshed DC Distributed Power Systems with Constant Power Loads
Huiyong Hu, Xiaoming Wang, Yonggang Peng, Yanghong Xia, Miao Yu, Wei Wei
July 26, 2019 (v1)
Keywords: meshed DC distributed power systems, stability criterion, stability enhancement, virtual harmonic resistance
This paper addresses the stability issue of the meshed DC distributed power systems (DPS) with constant power loads (CPLs) and proposes a stability enhancement method based on virtual harmonic resistance. In previous researches, the network dynamics of the meshed DC DPS are often ignored, which affects the derivation of the equivalent system impendence. In addition, few of them have considered the meshed DC DPS including multiple sources with voltage-controlled converters and CPLs. To tackle the aforementioned challenge, this paper mainly makes the following efforts. The component connection method (CCM) is employed and expanded to derive the stability criterion of the meshed DC DPS with CPLs. This stability criterion can be simplified to relate only with the network node admittance matrix, the output impendences of the sources, and the input admittances of the CPLs. A virtual harmonic resistance through the second-order generalized integrator (SOGI) is added in the source with the vol... [more]
Energy Rebound as a Potential Threat to a Low-Carbon Future: Findings from a New Exergy-Based National-Level Rebound Approach
Paul E. Brockway, Harry Saunders, Matthew K. Heun, Timothy J. Foxon, Julia K. Steinberger, John R. Barrett, Steve Sorrell
July 26, 2019 (v1)
Keywords: aggregate production function (APF), constant elasticity of substitution (CES) function, Energy Efficiency, energy policy, energy rebound, Exergy, Exergy Efficiency, macroeconomic rebound
150 years ago, Stanley Jevons introduced the concept of energy rebound: that anticipated energy efficiency savings may be “taken back” by behavioural responses. This is an important issue today because, if energy rebound is significant, this would hamper the effectiveness of energy efficiency policies aimed at reducing energy use and associated carbon emissions. However, empirical studies which estimate national energy rebound are rare and, perhaps as a result, rebound is largely ignored in energy-economy models and associated policy. A significant difficulty lies in the components of energy rebound assessed in empirical studies: most examine direct and indirect rebound in the static economy, excluding potentially significant rebound of the longer term structural response of the national economy. In response, we develop a novel exergy-based approach to estimate national energy rebound for the UK and US (1980⁻2010) and China (1981⁻2010). Exergy—as “available energy”—allows a consistent,... [more]
Impact of Battery Energy Storage System Operation Strategy on Power System: An Urban Railway Load Case under a Time-of-Use Tariff
Hyeongig Kim, Jae-Haeng Heo, Jong-Young Park, Yong Tae Yoon
July 26, 2019 (v1)
Keywords: battery energy storage system (BESS), energy storage owner (ESO), operation strategy, price-based demand response, time-of-use tariff, urban railway load
Customer-owned battery energy storage systems (BESS) have been used to reduce electricity costs of energy storage owners (ESOs) under a time-of-use (TOU) tariff in Korea. However, the current TOU tariff can unintentionally induce customer’s electricity usage to have a negative impact on power systems. This paper verifies the impact of different BESS operation strategies on power systems under a TOU tariff by analyzing the TOU tariff structure and the customer’s load pattern. First, several BESS operation strategies of ESO are proposed to reduce the electricity cost. In addition, a degradation cost calculation method for lithium ion batteries is considered for the ESO to determine the optimal BESS operation strategy that maximizes both electricity cost and annual investment cost. The optimal BESS operation strategy that maximizes ESO’s net benefit is illustrated by simulation using an urban railway load data from Namgwangju Station, Korea. The results show that BESS connected to urban r... [more]
Performance Analysis of Data-Driven and Model-Based Control Strategies Applied to a Thermal Unit Model
Cihan Turhan, Silvio Simani, Ivan Zajic, Gulden Gokcen Akkurt
July 26, 2019 (v1)
Keywords: advanced control design, Artificial Intelligence, model-based and data-driven approaches, modelling and simulation for control, thermal unit nonlinear system
The paper presents the design and the implementation of different advanced control strategies that are applied to a nonlinear model of a thermal unit. A data-driven grey-box identification approach provided the physically⁻meaningful nonlinear continuous-time model, which represents the benchmark exploited in this work. The control problem of this thermal unit is important, since it constitutes the key element of passive air conditioning systems. The advanced control schemes analysed in this paper are used to regulate the outflow air temperature of the thermal unit by exploiting the inflow air speed, whilst the inflow air temperature is considered as an external disturbance. The reliability and robustness issues of the suggested control methodologies are verified with a Monte Carlo (MC) analysis for simulating modelling uncertainty, disturbance and measurement errors. The achieved results serve to demonstrate the effectiveness and the viable application of the suggested control solution... [more]
Assessment against Experiments of Devolatilization and Char Burnout Models for the Simulation of an Aerodynamically Staged Swirled Low-NOx Pulverized Coal Burner
Marco Torresi, Francesco Fornarelli, Bernardo Fortunato, Sergio Mario Camporeale, Alessandro Saponaro
July 26, 2019 (v1)
Keywords: char burnout, computational fluid dynamics (CFD), devolatilization, industrial burner, NOx formation, pollutant emissions, pulverized coal combustion
In the next few years, even though there will be a continuous growth of renewables and a loss of the share of fossil fuel, energy production will still be strongly dependent on fossil fuels. It is expected that coal will continue to play an important role as a primary energy source in the next few decades due to its lower cost and higher availability with respect to other fossil fuels. However, in order to improve the sustainability of energy production from fossil fuels, in terms of pollutant emissions and energy efficiency, the development of advanced investigation tools is crucial. In particular, computational fluid dynamics (CFD) simulations are needed in order to support the design process of low emission burners. Even if in the literature several combustion models can be found, the assessment of their performance against detailed experimental measurements on full-scale pulverized coal burners is lacking. In this paper, the numerical simulation of a full-scale low-NO x , ae... [more]
Thermal Performance for Wet Cooling Tower with Different Layout Patterns of Fillings under Typical Crosswind Conditions
Ming Gao, Chang Guo, Chaoqun Ma, Yuetao Shi, Fengzhong Sun
July 26, 2019 (v1)
Keywords: crosswind, non-uniform layout filling, thermal performance, wet cooling tower
A thermal-state model experimental study was performed in lab to investigate the thermal performance of a wet cooling tower with different kinds of filling layout patterns under windless and 0.4 m/s crosswind conditions. In this paper, the contrast analysis was focused on comparing a uniform layout pattern and one kind of optimal non-uniform layout pattern when the environmental crosswind speed is 0 m/s and 0.4 m/s. The experimental results proved that under windless conditions, the heat transfer coefficient and total heat rejection of circulating water for the optimal non-uniform layout pattern can enhance by approximately 40% and 28%, respectively, compared with the uniform layout pattern. It was also discovered that the optimal non-uniform pattern can dramatically relieve the influence of crosswind on the thermal performance of the tower when the crosswind speed is equal to 0.4 m/s. For the uniform layout pattern, the heat transfer coefficient under 0.4 m/s crosswind conditions decr... [more]
Power Consumption Analysis of Electrical Installations at Healthcare Facility
Emmanuel Guillen-Garcia, Angel L. Zorita-Lamadrid, Oscar Duque-Perez, Luis Morales-Velazquez, Roque Alfredo Osornio-Rios, Rene de Jesus Romero-Troncoso
July 26, 2019 (v1)
Keywords: data acquisition, data analysis, energy consumption estimation, power quality
This paper presents a methodology for power consumption estimation considering harmonic and interharmonic content and then it is compared to the power consumption estimation commonly done by commercial equipment based on the fundamental frequency, and how they can underestimate the power consumption considering power quality disturbances (PQD). For this purpose, data of electrical activity at the electrical distribution boards in a healthcare facility is acquired for a long time period with proprietary equipment. An analysis in the acquired current and voltage signals is done, in order to compare the power consumption centered in the fundamental frequency with the generalized definition of power consumption. The results obtained from the comparison in the power consumption estimation show differences between 4% and 10% of underestimated power consumption. Thus, it is demonstrated that the presence of harmonic and interharmonic content provokes a significant underestimation of power con... [more]
Non-Linear Behavioral Modeling for DC-DC Converters and Dynamic Analysis of Distributed Energy Systems
Xiancheng Zheng, Husan Ali, Xiaohua Wu, Haider Zaman, Shahbaz Khan
July 26, 2019 (v1)
Keywords: behavioral modeling, distributed energy system (DES), electronic power distribution, non-linear, power electronics converter
In modern distributed energy systems (DES), focus is shifting from the conventional centralized approach towards distributed architectures. However, modeling and analysis of these systems is more complex, as it involves the interface of multiple energy sources with many different type of loads through power electronics converters. The integration of power electronics converters allows distributed renewable energy sources to become part of modern electronics power distribution systems (EPDS). It will also facilitate the ongoing research towards DC-based DES which is mostly composed of commercial DC-DC converters whose internal structure and parameters are unknown. For the system level analysis, the behavioral modeling technique is the only choice. Since most power electronics converters are non-linear systems and linear models can’t model their dynamics to a desired level of accuracy, hence non-linear modeling is required for accurate modeling. The non-linear modeling approach presented... [more]
Investigation of Ethanol Production Potential from Lignocellulosic Material without Enzymatic Hydrolysis Using the Ultrasound Technique
Manoj Kandasamy, Ihsan Hamawand, Leslie Bowtell, Saman Seneweera, Sayan Chakrabarty, Talal Yusaf, Zaidoon Shakoor, Sattar Algayyim, Friederike Eberhard
July 26, 2019 (v1)
Subject: Biosystems
Keywords: bagasse, bioethanol, biofuel, Biomass, lignocellulose, pre-treatment
This research investigates ethanol production from waste lignocellulosic material (sugarcane bagasse). The bagasse was first pretreated using chemicals and ultrasound techniques. These pretreatment techniques were applied separately and combined. The pretreated bagasse was then fermented anaerobically for biofuel production without enzymatic hydrolysis. The results showed higher ethanol production than those reported in the literature. The maximum ethanol production of 820 mg/L was achieved with a combination of ultrasound (60 amplitude level, 127 W) and acid (3% H₂SO₄ concentration). The combination of two-step pretreatment such as an ultrasound (50 amplitude level, 109 W) with acid (3% H₂SO₄ concentration) and then an ultrasound with alkaline (23% NaOH concentration) generated 911 mg/L of ethanol.
Ion Migration in the Process of Water Freezing under Alternating Electric Field and Its Impact on Insulator Flashover
Xingliang Jiang, Quanlin Wang, Zhijing Zhang, Jianlin Hu, Qin Hu, Chengzhi Zhu
July 26, 2019 (v1)
Subject: Other
Keywords: alternating electric field, flashover voltage, insulator, ion migration, melting water conductivity
Ice flashover threatens the security and reliability of power transmission. However, the ice flashover mechanism of insulators remains poorly understood. This study analyses water droplet freezing and ion distribution in ice layer under alternating electric field. It also investigates ion migration during icing process of insulator string under alternating electric field and its effects on insulator flashover. Results showed that the average freezing time of water droplets was related to electric field strength. The extent of ion migration during freezing decreased with increasing electric field strength. The maximal melting water conductivity of the ice layer and icicle of the insulator formed under energized condition was higher than the corresponding freezing water conductivity but lower than that under non-energized condition. Furthermore, the hanging location of each insulator significantly affected the melting water conductivity of the ice layer. The surface conductivity of the i... [more]
Battery Internal Temperature Estimation for LiFePO₄ Battery Based on Impedance Phase Shift under Operating Conditions
Jiangong Zhu, Zechang Sun, Xuezhe Wei, Haifeng Dai
July 26, 2019 (v1)
Keywords: electric vehicles (EVs), impedance, internal temperature estimation, lithium-ion battery, phase shift
An impedance-based temperature estimation method is investigated considering the electrochemical non-equilibrium with short-term relaxation time for facilitating the vehicular application. Generally, sufficient relaxation time is required for battery electrochemical equilibrium before the impedance measurement. A detailed experiment is performed to investigate the regularity of the battery impedance in short-term relaxation time after switch-off current excitation, which indicates that the impedance can be measured and also has systematical decrement with the relaxation time growth. Based on the discussion of impedance variation in electrochemical perspective, as well as the monotonic relationship between impedance phase shift and battery internal temperature in the electrochemical equilibrium state, an exponential equation that accounts for both measured phase shift and relaxation time is established to correct the measuring deviation caused by electrochemical non-equilibrium. Then, a... [more]
Development of an Nearly Zero Emission Building (nZEB) Life Cycle Cost Assessment Tool for Fast Decision Making in the Early Design Phase
Hae Jin Kang
July 26, 2019 (v1)
Subject: Energy Policy
Keywords: cost optimal model, designer’s proposed model, investment cost, LCC analysis, nearly Zero Emission Building, operation cost
An economic feasibility optimization method for the life cycle cost (LCC) has been developed to apply energy saving techniques in the early design stages of a building. The method was developed using default data (e.g., operation schedules), energy consumption prediction equations and cost prediction equations utilizing design variables considered in the early design phase. With certain equations developed, an LCC model was constructed using the computational program MATLAB, to create an automated optimization process. To verify the results from the newly developed assessment tool, a case study on an office building was performed to outline the results of the designer’s proposed model and the cost optimal model.
Design Parameters of Vortex Pumps: A Meta-Analysis of Experimental Studies
Angela Gerlach, Paul Uwe Thamsen, Sebastian Wulff, Christian Brix Jacobsen
July 26, 2019 (v1)
Keywords: design parameters, enlarged side chamber, experimental studies, meta-analysis, operating principle, recessed impeller, vortex pump
Vortex pumps can impel solid-containing fluids and are therefore widely applied, from wastewater transport to the food industry. Despite constant efforts to improve vortex pumps, however, they have remained relatively inefficient compared to conventional centrifugal pumps. To find an optimized design of vortex pumps, this paper provides a systematic analysis on experimental studies that investigated how variations in geometric parameters influence vortex pump characteristics, in particular the pump head, the pressure coefficient and the efficiency for best point operation. To this end, an extensive literature search was conducted, and eighteen articles with 53 primary investigations were identified and meta-integrated. This showed that it is not yet clarified how vortex pumps operate. Two different assumptions of the underlying operating principle of a vortex pump lead to diverging design principles. From the results of this meta-analysis, we deduce recommendations for a more efficient... [more]
Energy Performance and Radial Force of a Mixed-Flow Pump with Symmetrical and Unsymmetrical Tip Clearances
Yue Hao, Lei Tan, Yabin Liu, Yun Xu, Jinsong Zhang, Baoshan Zhu
July 26, 2019 (v1)
Subject: Other
Keywords: mixed-flow pump, radial force, symmetrical and unsymmetrical, tip clearance
The energy performance and radial force of a mixed flow pump with symmetrical and unsymmetrical tip clearance are investigated in this paper. As the tip clearance increases, the pump head and efficiency both decrease. The center of the radial force on the principal axis is located at the coordinate origin when the tip clearance is symmetrical, and moves to the third quadrant when the tip clearance is unsymmetrical. Analysis results show that the total radial force on the principal axis is closely related to the fluctuation of mass flow rate in each single flow channel. Unsteady simulations show that the dominant frequencies of radial force on the hub and blade correspond to the blade number, vane number, or double blade number because of the rotor stator interaction. The radial force on the blade pressure side decreases with the tip clearance increase because of leakage flow. The unsymmetrical tip clearances in an impeller induce uneven leakage flow rate and then result in unsymmetrica... [more]
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