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Showing records 76 to 100 of 155. [First] Page: 1 2 3 4 5 6 7 Last
A Current Control Approach for an Abnormal Grid Supplied Ultra Sparse Z-Source Matrix Converter with a Particle Swarm Optimization Proportional-Integral Induction Motor Drive Controller
Seyed Sina Sebtahmadi, Hanieh Borhan Azad, Didarul Islam, Mehdi Seyedmahmoudian, Ben Horan, Saad Mekhilef
January 31, 2019 (v1)
Keywords: induction motor drives, matrix converter, Particle Swarm Optimization, Z-source network
A rotational d-q current control scheme based on a Particle Swarm Optimization- Proportional-Integral (PSO-PI) controller, is used to drive an induction motor (IM) through an Ultra Sparse Z-source Matrix Converter (USZSMC). To minimize the overall size of the system, the lowest feasible values of Z-source elements are calculated by considering the both timing and aspects of the circuit. A meta-heuristic method is integrated to the control system in order to find optimal coefficient values in a single multimodal problem. Henceforth, the effect of all coefficients in minimizing the total harmonic distortion (THD) and balancing the stator current are considered simultaneously. Through changing the reference point of magnitude or frequency, the modulation index can be automatically adjusted and respond to changes without heavy computational cost. The focus of this research is on a reliable and lightweight system with low computational resources. The proposed scheme is validated through bot... [more]
Using CPE Function to Size Capacitor Storage for Electric Vehicles and Quantifying Battery Degradation during Different Driving Cycles
Cong Zhang, Haitao Min, Yuanbin Yu, Dai Wang, Justin Luke, Daniel Opila, Samveg Saxena
January 31, 2019 (v1)
Keywords: battery, continuous power-energy, electric vehicle, hybrid energy storage system, super-capacitor
Range anxiety and battery cycle life are two major factors which restrict the development of electric vehicles. Battery degradation can be reduced by adding supercapacitors to create a Hybrid Energy Storage System. This paper proposes a systematic approach to configure the hybrid energy storage system and quantifies the battery degradation for electric vehicles when using supercapacitors. A continuous power-energy function is proposed to establish supercapacitor size based on national household travel survey statistics. By analyzing continuous driving action in standard driving cycles and special driving phases (start up and acceleration), the supercapacitor size is calculated to provide a compromise between the capacitor size and battery degradation. Estimating the battery degradation after 10 years, the battery capacity loss value decreases 17.55% and 21.6%, respectively, under the urban dynamometer driving schedule and the US06. Furthermore, the battery lifespan of the continuous po... [more]
A Generalized SOC-OCV Model for Lithium-Ion Batteries and the SOC Estimation for LNMCO Battery
Caiping Zhang, Jiuchun Jiang, Linjing Zhang, Sijia Liu, Leyi Wang, Poh Chiang Loh
January 31, 2019 (v1)
Subject: Other
Keywords: electrochemical process analysis, lithium-ion batteries, SOC estimation, SOC-OCV modeling
A state-of-charge (SOC) versus open-circuit-voltage (OCV) model developed for batteries should preferably be simple, especially for real-time SOC estimation. It should also be capable of representing different types of lithium-ion batteries (LIBs), regardless of temperature change and battery degradation. It must therefore be generic, robust and adaptive, in addition to being accurate. These challenges have now been addressed by proposing a generalized SOC-OCV model for representing a few most widely used LIBs. The model is developed from analyzing electrochemical processes of the LIBs, before arriving at the sum of a logarithmic, a linear and an exponential function with six parameters. Values for these parameters are determined by a nonlinear estimation algorithm, which progressively shows that only four parameters need to be updated in real time. The remaining two parameters can be kept constant, regardless of temperature change and aging. Fitting errors demonstrated with different... [more]
Auto-Mapping and Configuration Method of IEC 61850 Information Model Based on OPC UA
In-Jae Shin, Byung-Kwen Song, Doo-Seop Eom
January 31, 2019 (v1)
Keywords: abstract communication service interface (ACSI), IEC 61850, open-platform communication (OPC) unified architecture (UA), smart grid, system configuration description language (SCL)
The open-platform communication (OPC) unified architecture (UA) (IEC62541) is introduced as a key technology for realizing a variety of smart grid (SG) use cases enabling relevant automation and control tasks. The OPC UA can expand interoperability between power systems. The top-level SG management platform needs independent middleware to transparently manage the power information technology (IT) systems, including the IEC 61850. To expand interoperability between the power system for a large number of stakeholders and various standards, this paper focuses on the IEC 61850 for the digital substation. In this paper, we propose the interconnection method to integrate communication with OPC UA and convert OPC UA AddressSpace using system configuration description language (SCL) of IEC 61850. We implemented the mapping process for the verification of the interconnection method. The interconnection method in this paper can expand interoperability between power systems for OPC UA integration... [more]
The Impact and Determinants of Environmental Taxation on Economic Growth Communities in Romania
Jean Andrei, Mihai Mieila, Gheorghe H. Popescu, Elvira Nica, Manole Cristina
January 31, 2019 (v1)
Subject: Energy Policy
Keywords: development, economic growth, emergent economy, Energy, environment, renewables, taxation
Environmental taxation represents a key influence on sustainable development in post-transition countries. Romania has experienced important transformations of environmental policy, including taxation, due to sustained reliance on traditional energy sources to satisfy its energy needs. The aim of this paper is to show a possible causal relationship between the Romanian GDP and several explanatory variables related to taxation of environmental damage and energy generation and consumption in the country. In order to do this, the authors make use of several statistical tests to verify the existence of a meaningful relationship between economic variables expressed in time series. The study has also attempted to identify the influence of environmental taxation on ensuring green economic development, starting from the premise that for emergent economies these taxes provide both a GDP increase and prevent environmental degradation by decreasing the pollution and environmentally harmful suppli... [more]
A Rest Time-Based Prognostic Framework for State of Health Estimation of Lithium-Ion Batteries with Regeneration Phenomena
Taichun Qin, Shengkui Zeng, Jianbin Guo, Zakwan Skaf
January 31, 2019 (v1)
Keywords: cycle beginning time, hyperplane shift, lithium-ion batteries, rest time, state of health (SOH), support vector machine
State of health (SOH) prognostics is significant for safe and reliable usage of lithium-ion batteries. To accurately predict regeneration phenomena and improve long-term prediction performance of battery SOH, this paper proposes a rest time-based prognostic framework (RTPF) in which the beginning time interval of two adjacent cycles is adopted to reflect the rest time. In this framework, SOH values of regeneration cycles, the number of cycles in regeneration regions and global degradation trends are extracted from raw SOH time series and predicted respectively, and then the three sets of prediction results are integrated to calculate the final overall SOH prediction values. Regeneration phenomena can be found by support vector machine and hyperplane shift (SVM-HS) model by detecting long beginning time intervals. Gaussian process (GP) model is utilized to predict the global degradation trend, and nonlinear models are utilized to predict the regeneration amplitude and the cycle number o... [more]
Using Trajectory Clusters to Define the Most Relevant Features for Transient Stability Prediction Based on Machine Learning Method
Luyu Ji, Junyong Wu, Yanzhen Zhou, Liangliang Hao
January 31, 2019 (v1)
Keywords: feature extraction and selection, support vector machines, trajectory clusters, transient stability prediction
To achieve rapid real-time transient stability prediction, a power system transient stability prediction method based on the extraction of the post-fault trajectory cluster features of generators is proposed. This approach is conducted using data-mining techniques and support vector machine (SVM) models. First, the post-fault rotor angles and generator terminal voltage magnitudes are considered as the input vectors. Second, we construct a high-confidence dataset by extracting the 27 trajectory cluster features obtained from the chosen databases. Then, by applying a filter⁻wrapper algorithm for feature selection, we obtain the final feature set composed of the eight most relevant features for transient stability prediction, called the global trajectory clusters feature subset (GTCFS), which are validated by receiver operating characteristic (ROC) analysis. Comprehensive simulations are conducted on a New England 39-bus system under various operating conditions, load levels and topologie... [more]
Carbon Auction Revenue and Market Power: An Experimental Analysis
Noah Dormady
January 31, 2019 (v1)
Subject: Energy Policy
Keywords: cap-and-trade, carbon auctions, Clean Air Act, Clean Power Plan, climate change, government revenue, market power
State and regional governments in the U.S. and abroad are looking to market-based approaches to mitigating greenhouse gas emissions from the electric sector, and in the U.S. as a compliance approach to meeting the aggressive targets of the Environmental Protection Agency (EPA)’s Clean Power Plan. Auction-based approaches, like those used in the Northeast U.S. and California, are both recommended strategies under the Plan and attractive to state governments because they can generate significant revenue from the sale of emissions permits. However, given the nature of imperfect competition in existing electricity markets, particularly at the state and regional level, the issue of market power is a concern at the forefront. This paper provides the results from a controlled laboratory experiment of an auction-based emissions market in the electricity sector. The results show that government revenue from auctioning emissions permits is substantially lower when market concentration is only mo... [more]
Assessment of the Agronomic Feasibility of Bioenergy Crop Cultivation on Marginal and Polluted Land: A GIS-Based Suitability Study from the Sulcis Area, Italy
Giuseppe Pulighe, Guido Bonati, Stefano Fabiani, Tommaso Barsali, Flavio Lupia, Silvia Vanino, Pasquale Nino, Pasquale Arca, Pier Paolo Roggero
January 31, 2019 (v1)
Subject: Biosystems
Keywords: agronomic feasibility, Biomass, geographic information system (GIS), land suitability, marginal land, spatial analysis
In the context of environmental sustainability there has been an increasing interest in bioenergy production from renewable resources, and is expected that European biofuel production from energy crops will increase as a consequence of the achievement of policy targets. The aim of this paper is to assess the agronomic feasibility of biomass crop cultivation to provide profitable renewable feedstocks in a marginal and heavy-metal polluted area located in the Sulcis district, Sardinia (Italy). Results from literature review and unpublished data from field trials carried out in Sardinia were analysed to establish the main agronomic traits of crops (e.g., yield potential and input requirements). A Geographical Information System (GIS)-based procedure with remotely sensed data is also used to evaluate the land suitability and the actual land use/cover, considering a future scenario of expansion of energy crops on these marginal areas avoiding potential conflicts with food production. The re... [more]
A Long-Term Wind Speed Ensemble Forecasting System with Weather Adapted Correction
Yiqi Chu, Chengcai Li, Yefang Wang, Jing Li, Jian Li
January 31, 2019 (v1)
Keywords: ensemble forecasting, statistical correction, weather classification, wind forecasting, wind power
Wind forecasting is critical in the wind power industry, yet forecasting errors often exist. In order to effectively correct the forecasting error, this study develops a weather adapted bias correction scheme on the basis of an average bias-correction method, which considers the deviation of estimated biases associated with the difference in weather type within each unit of the statistical sample. This method is tested by an ensemble forecasting system based on the Weather Research and Forecasting (WRF) model. This system provides high resolution wind speed deterministic forecasts using 40 members generated by initial perturbations and multi-physical schemes. The forecasting system outputs 28⁻52 h predictions with a temporal resolution of 15 min, and is evaluated against collocated anemometer towers observations at six wind fields located on the east coast of China. Results show that the information contained in weather types produces an improvement in the forecast bias correction.
Dimensionless Maps for the Validity of Analytical Ground Heat Transfer Models for GSHP Applications
Paolo Conti
January 31, 2019 (v1)
Keywords: analytical models, dimensionless analysis, finite cylindrical heat source, finite linear heat source, ground heat transfer, ground-source heat pump systems, infinite cylindrical heat source, infinite linear heat source, purely-conductive media
This article provides plain and handy expressions to decide the most suitable analytical model for the thermal analysis of the ground source in vertical ground-coupled heat pump applications. We perform a comprehensive dimensionless analysis of the reciprocal deviation among the classical infinite, finite, linear and cylindrical heat source models in purely conductive media. Besides, we complete the framework of possible boreholes model with the “hollow” finite cylindrical heat source solution, still lacking in the literature. Analytical expressions are effective tools for both design and performance assessment: they are able to provide practical and general indications on the thermal behavior of the ground with an advantageous tradeoff between calculation efforts and solution accuracy. This notwithstanding, their applicability to any specific case is always subjected to the coherence of the model assumptions, also in terms of length and time scales, with the specific case of interest.... [more]
Analytical Modeling of Static Eccentricities in Axial Flux Permanent-Magnet Machines with Concentrated Windings
Yunkai Huang, Baocheng Guo, Ahmed Hemeida, Peter Sergeant
January 31, 2019 (v1)
Subject: Other
Keywords: analytical model, axial flux permanent magnet (AFPM) machines, back electromotive force (EMF), conformal mapping (CM), double rotor, Finite element (FE) model, static eccentricity (SE), torque
The aim of this paper is to calculate the static eccentricity (SE) of a double rotor axial flux permanent magnet (AFPM) machine by using a general analytical model. The flux density in the air gap under healthy conditions is calculated firstly, where the axial and circumferential magnetic flux densities are obtained using a coupled solution of Maxwell’s equations and Schwarz-Christoffel (SC) mapping. The magnetic flux densities under SE conditions are calculated afterwards using a novel bilinear mapping. Some important electromagnetic parameters, e.g., back electromotive force (EMF), cogging torque and electromagnetic (EM) torque, are calculated for both SE and healthy conditions, and compared with the finite element (FE) model. As for the double rotor AFPM, SE does not contribute much effect on the back EMF and EM torque, while the cogging torque is increased. At each calculated section, FE models were built to validate the analytical model. The results show that the analytical predic... [more]
Economic Growth, Electricity Consumption, Labor Force and Capital Input: A More Comprehensive Analysis on North China Using Panel Data
Huiru Zhao, Haoran Zhao, Xiaoyu Han, Zhonghua He, Sen Guo
January 31, 2019 (v1)
Subject: Energy Policy
Keywords: economic growth, electricity consumption, granger causality test, labor force and capital input, panel co-integration test
Over the past three decades, China’s economy has witnessed remarkable growth, with an average annual growth rate over 9%. However, China also faces great challenges to balance this spectacular economic growth and continuously increasing energy use like many other economies in the world. With the aim of designing effective energy and environmental policies, policymakers are required to master the relationship between energy consumption and economic growth. Therefore, in the case of North China, a multivariate model employing panel data analysis method based on the Cobb-Douglas production function which introduces electricity consumption as a main factor was established in this paper. The equilibrium relationship and causal relationship between real GDP, electricity consumption, total investment in fixed assets, and the employment were explored using data during the period of 1995⁻2014 for six provinces in North China, including Beijing City, Tianjin City, Hebei Province, Shanxi Province... [more]
Communication Channel Reconstruction for Transmission Line Differential Protection: System Arrangement and Routing Protocol
Xu Chen, Xianggen Yin, Bin Yu, Zhe Zhang
January 31, 2019 (v1)
Keywords: communication channel, differential protection, routing protocol, wireless sensor network (WSN)
Natural disasters may be of significant impact on overhead transmission lines and cause communication outage related to pilot protection. This paper aims at reconstructing communication channels and maintaining functions of pilot-wire differential protections after the main channel fails. With the development of smart grids as well as new communication technologies, wireless sensor networks (WSNs) have been potential means for realizing reconstructed communication channels (RCCs) without further installation. For a reliable design, system arrangement and the communication structure were presented. Theoretical planning of sensor nodes was formulated, which enjoys advantages such as high reliability, cost optimization, and capacity of satisfying the connectivity of the communication network. To meet the need of time delay, a novel routing protocol for WSNs was proposed with three stages including route establishment, route discovery and route maintenance, which ensured the directional pr... [more]
Design and Analysis of Generic Energy Management Strategy for Controlling Second-Life Battery Systems in Stationary Applications
Mohamed Abdel-Monem, Omar Hegazy, Noshin Omar, Khiem Trad, Sven De Breucker, Peter Van Den Bossche, Joeri Van Mierlo
January 31, 2019 (v1)
Keywords: battery management system (BMS), energy storage system (ESS), energy/power management strategy, lithium-ion (Li-ion) batteries, multi-port power converter, rule-based control strategy, second-life batteries, self-consumption of photo-voltaic profile, stationary applications
Recently, second-life battery systems have received a growing interest as one of the most promising alternatives for decreasing the overall cost of the battery storage systems in stationary applications. The high-cost of batteries represents a prominent barrier for their use in traction and stationary applications. To make second-life batteries economically viable for stationary applications, an effective power-electronics converter should be selected as well. This converter should be supported by an energy management strategy (EMS), which is needed for controlling the power flow among the second-life battery modules based on their available capacity and performance. This article presents the design, analysis and implementation of a generic energy management strategy (GEMS). The proposed GEMS aims to control and distribute the load demand between battery storage systems under different load conditions and disturbances. This manuscript provides the experimental verification of the propo... [more]
Scrap Tyre Management Pathways and Their Use as a Fuel—A Review
Amir Rowhani, Thomas J. Rainey
January 31, 2019 (v1)
Subject: Energy Policy
Keywords: bio-oil, pyrolysis, recycling, scrap tyre, tyre management
This article provides a review of different methods for managing waste tyres. Around 1.5 billion scrap tyres make their way into the environmental cycle each year, so there is an extreme demand to manage and mitigate the environmental impact which occurs from landfilling and burning. Numerous approaches are targeted to recycle and reuse the tyre rubber in various applications. Among them, one of the most important methods for sustainable environmental stewardship is converting tyre rubber components into bio-oil. In this study, scrap tyre management techniques including landfill, retreading, recycling, combustion, and conversion to liquid fuels was reviewed (including gasification, hydrothermal liquefaction, and pyrolysis). The effects of parameters such as reactor types, pyrolysis temperature, and catalyst on the oil, gas and solid products in pyrolysis process were investigated.
Application of a LiFePO₄ Battery Energy Storage System to Primary Frequency Control: Simulations and Experimental Results
Fabio Massimo Gatta, Alberto Geri, Regina Lamedica, Stefano Lauria, Marco Maccioni, Francesco Palone, Massimo Rebolini, Alessandro Ruvio
January 31, 2019 (v1)
Subject: Materials
Keywords: battery energy storage system (BESS), LiFePO4 battery, primary frequency control
This paper presents an experimental application of LiFePO₄ battery energy storage systems (BESSs) to primary frequency control, currently being performed by Terna, the Italian transmission system operator (TSO). BESS performance in the primary frequency control role was evaluated by means of a simplified electrical-thermal circuit model, taking into account also the BESS auxiliary consumptions, coupled with a cycle-life model, in order to assess the expected life of the BESS. Numerical simulations have been carried out considering the system response to real frequency measurements taken in Italy, spanning a whole year; a parametric study taking into account different values of governor droop and of BESS charge/discharge rates (C-rates) was also performed. Simulations, fully validated by experimental results obtained thus far, evidenced a severe trade-off between expected lifetime and overall efficiency, which significantly restricts the choice of operating parameters for frequency cont... [more]
Effects of Power Tracking Algorithms on Lifetime of Power Electronic Devices Used in Solar Systems
Canras Batunlu, Mohamad Alrweq, Alhussein Albarbar
January 31, 2019 (v1)
Keywords: availability of photovoltaic solar systems, power management algorithms (PMAs), thermal stress of boost converters
In photovoltaic solar energy systems, power management algorithms (PMAs), usually called maximum power point tracking (MPPT) algorithms, are widely used for extracting maximum available power at every point in time. However, tracking the maximum power has negative effects on the availability of solar energy systems. This is due, mainly, to the created disturbances and thermal stresses on the associated power electronic converters (PECs). This work investigates the effects of PMA on the lifetime consumption, thermal stresses and failures on DC-DC converters used in solar systems. Firstly theoretical analysis and modelling of photovoltaic solar systems including converter’s electro thermal characteristics were developed. Subsequently, experiments on photovoltaic solar systems were carried out using two different PMAs, namely, perturb and observe (P&O) and incremental conductance (IC). Real-time data was collected, under different operating conditions, including thermal behavior using... [more]
Two-Stage Multi-Objective Collaborative Scheduling for Wind Farm and Battery Switch Station
Zhe Jiang, Xueshan Han, Zhimin Li, Wenbo Li, Mengxia Wang, Mingqiang Wang
January 31, 2019 (v1)
Keywords: battery switch station, dependent chance programming, electric vehicle, power system, wind farm
In order to deal with the uncertainties of wind power, wind farm and electric vehicle (EV) battery switch station (BSS) were proposed to work together as an integrated system. In this paper, the collaborative scheduling problems of such a system were studied. Considering the features of the integrated system, three indices, which include battery swapping demand curtailment of BSS, wind curtailment of wind farm, and generation schedule tracking of the integrated system are proposed. In addition, a two-stage multi-objective collaborative scheduling model was designed. In the first stage, a day-ahead model was built based on the theory of dependent chance programming. With the aim of maximizing the realization probabilities of these three operating indices, random fluctuations of wind power and battery switch demand were taken into account simultaneously. In order to explore the capability of BSS as reserve, the readjustment process of the BSS within each hour was considered in this stage... [more]
Exergy and Thermoeconomic Analyses of Central Receiver Concentrated Solar Plants Using Air as Heat Transfer Fluid
Claudia Toro, Matteo V. Rocco, Emanuela Colombo
January 31, 2019 (v1)
Keywords: concentrated solar plant, exergoeconomic cost analysis, exergy cost analysis
The latest developments in solar technologies demonstrated that the solar central receiver configuration is the most promising application among concentrated solar power (CSP) plants. In CSPs solar-heated air can be used as the working fluid in a Brayton thermal cycle and as the heat transfer fluid for a Rankine thermal cycle as an alternative to more traditional working fluids thereby reducing maintenance operations and providing the power section with a higher degree of flexibility To supply thermal needs when the solar source is unavailable, an auxiliary burner is requested. This configuration is adopted in the Julich CSP (J-CSP) plant, operating in Germany and characterized by a nominal power of 1.5 MW, the heat transfer fluid (HTF) is air which is heated in the solar tower and used to produce steam for the bottoming Rankine cycle. In this paper, the J-CSP plant with thermal energy storage has been compared with a hybrid CSP plant (H-CSP) using air as the working fluid. Thermodynam... [more]
Nonlinear Coupled Dynamics of a Rod Fastening Rotor under Rub-Impact and Initial Permanent Deflection
Liang Hu, Yibing Liu, Wei Teng, Chao Zhou
January 31, 2019 (v1)
Subject: Other
Keywords: bifurcation, contact, coupled dynamic characteristic, D’Alembert principle, initial permanent deflection, rod fastening rotor
A nonlinear coupled dynamic model of a rod fastening rotor under rub-impact and initial permanent deflection was developed in this paper. The governing motion equation was derived by the D’Alembert principle considering the contact characteristic between disks, nonlinear oil-film force, rub-impact force, unbalance mass, etc. The contact effects between disks was modeled as a flexural spring with cubical nonlinear stiffness. The coupled nonlinear dynamic phenomena of the rub-impact rod fastening rotor bearing system with initial permanent deflection were investigated by the fourth-order Runge-Kutta method. Bifurcation diagram, vibration waveform, frequency spectrum, shaft orbit and Poincaré map are used to illustrate the rich diversity of the system response with complicated dynamics. The studies indicate that the coupled dynamic responses of the rod fastening rotor bearing system under rub-impact and initial permanent deflection exhibit a rich nonlinear dynamic diversity, synchronous p... [more]
A Short-Term Outage Model of Wind Turbines with Doubly Fed Induction Generators Based on Supervisory Control and Data Acquisition Data
Peng Sun, Jian Li, Junsheng Chen, Xiao Lei
January 31, 2019 (v1)
Keywords: prediction model, short-term outage model, supervisory control and data acquisition (SCADA) data, wind turbine (WT)
This paper presents a short-term wind turbine (WT) outage model based on the data collected from a wind farm supervisory control and data acquisition (SCADA) system. Neural networks (NNs) are used to establish prediction models of the WT condition parameters that are dependent on environmental conditions such as ambient temperature and wind speed. The prediction error distributions are discussed and used to calculate probabilities of the operation of protection relays (POPRs) that were caused by the threshold exceedance of the environmentally sensitive parameters. The POPRs for other condition parameters are based on the setting time of the operation of protection relays. The union probability method is used to integrate the probabilities of operation of each protection relay to predict the WT short term outage probability. The proposed method has been used for real 1.5 MW WTs with doubly fed induction generators (DFIGs). The results show that the proposed method is more effective in W... [more]
Condensation Risk Due to Variations in Airtightness and Thermal Insulation of an Office Building in Warm and Wet Climate
Wanghee Cho, Shizuo Iwamoto, Shinsuke Kato
January 31, 2019 (v1)
Subject: Other
Keywords: airtightness, condensation risk (CR), microbial growth, office building, thermal insulation, warm and wet climate
Condensation in a building encourages microbial growth, which can have an adverse effect on the health of occupants. Furthermore, it induces the deterioration of the building. To prevent problems caused by condensation, from the design step of a building, predictions of the spatial, temporal and causation for condensation occurrences are necessary. By using TRNSYS simulation coupled with TRNFLOW, condensation assessment of an entire office building in Tokyo, Japan, was conducted throughout the year, including when the air-conditioning system was not operated, by considering the absorption-desorption properties of the building materials and papers in the office and the airflow within the entire building. It was found that most of the condensation occurred during winter and was observed mainly in the non-air-conditioned core parts, especially the topmost floor. Additional analyses, which identified the effect of variations in the thermal insulation of the external walls, roof and windows... [more]
A Study on Electric Vehicle Heat Pump Systems in Cold Climates
Ziqi Zhang, Wanyong Li, Junye Shi, Jiangping Chen
January 31, 2019 (v1)
Keywords: economized vapor injection, electric vehicle, heat pump
Electric vehicle heat pumps are drawing more and more attention due to their energy-saving and high efficiency designs. Some problems remain, however, in the usage of the heat pumps in electric vehicles, such as a drainage problem regarding the external heat exchangers while in heat pump mode, and the decrease in heating performance when operated in a cold climate. In this article, an R134a economized vapor injection (EVI) heat pump system was built and tested. The drainage problem common amongst external heat exchangers was solved by an optimized 5 mm diameter tube-and-fin heat exchanger, which can meet both the needs of a condenser and evaporator based on simulation and test results. The EVI system was also tested under several ambient temperatures. It was found that the EVI was a benefit to the system heating capacity. Under a −20 °C ambient temperature, an average improvement of 57.7% in heating capacity was achieved with EVI and the maximum capacity was 2097 W, with a coefficient... [more]
A Review of Frequency Response Analysis Methods for Power Transformer Diagnostics
Saleh Alsuhaibani, Yasin Khan, Abderrahmane Beroual, Nazar Hussain Malik
January 31, 2019 (v1)
Keywords: condition assessment, diagnostics, frequency response analysis (FRA), power transformer
Power transformers play a critical role in electric power networks. Such transformers can suffer failures due to multiple stresses and aging. Thus, assessment of condition and diagnostic techniques are of great importance for improving power network reliability and service continuity. Several techniques are available to diagnose the faults within the power transformer. Frequency response analysis (FRA) method is a powerful technique for diagnosing transformer winding deformation and several other types of problems that are caused during manufacture, transportation, installation and/or service life. This paper provides a comprehensive review on FRA methods and their applications in diagnostics and fault identification for power transformers. The paper discusses theory and applications of FRA methods as well as various issues and challenges faced in the application of this method.
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