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Energies, Volume 12, Issue 24 (December-2 2019) – 213 articles

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Cover Story (view full-size image) Multiphase machines are the main choice for multi-MW electric drives in a wide range of areas, such [...] Read more.
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Open AccessArticle
Increasing Benefits in High PV Penetration Distribution System by Using Battery Enegy Storage and Capacitor Placement Based on Salp Swarm Algorithm
Energies 2019, 12(24), 4817; https://doi.org/10.3390/en12244817 - 17 Dec 2019
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Abstract
This work aims to maximize the benefit of the low-voltage (LV) level distribution system with high photovoltaic (PV) penetration by using an optimal installation of a battery energy storage system (BESS) and capacitor. The 41-bus practical distribution system located in Thailand was focused [...] Read more.
This work aims to maximize the benefit of the low-voltage (LV) level distribution system with high photovoltaic (PV) penetration by using an optimal installation of a battery energy storage system (BESS) and capacitor. The 41-bus practical distribution system located in Thailand was focused on. The comprehensive objective function regarding the focused system was proposed. The Salp Swarm and Genetic Algorithms were applied to solve the optimization problem. The total net present value (NPV) of utility was performed as a beneficial indicator, and it was determined by the overall costs and benefits of BESS installation and capacitor placement. A comparison of total NPV in the cases of centralized BESS installation, BESS installation with LV capacitor placement, and decentralized BESS installation was indicated. The results showed that all cases of BESS installation could increasingly flatten the load on the transformer; meanwhile, the voltage profile of the system was significantly improved. Optimal installation of centralized BESS simultaneously with LV capacitor placement provides higher NPV than the case with only centralized BESS installation. In particular, the highest NPV was obtained in the case of installing decentralized BESS. The results can be utilized to maximize the benefits of the utility in the distribution system at a high PV penetration level. Full article
(This article belongs to the Section Electrical Power and Energy System)
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Open AccessArticle
Design and Analysis of a Permanent Magnet Synchronous Motor Considering Axial Asymmetric Position of Rotor to Stator
Energies 2019, 12(24), 4816; https://doi.org/10.3390/en12244816 - 17 Dec 2019
Viewed by 318
Abstract
This paper presents the design and analysis of a permanent magnet synchronous motor (PMSM) considering the axial asymmetric PM overhang for a smart actuator (SA) application such as an isokinetic exercise machine. This structure helps take advantage of the motor space effectively and [...] Read more.
This paper presents the design and analysis of a permanent magnet synchronous motor (PMSM) considering the axial asymmetric PM overhang for a smart actuator (SA) application such as an isokinetic exercise machine. This structure helps take advantage of the motor space effectively and makes the system small in size and light in weight. However, two drawbacks related to the performance of motor occur when the axial asymmetric PM overhang is used: (1) an axial attractive force (AAF) is created, which can produce motor noise and vibration; (2) the torque of motor is reduced compared with the symmetric PM overhang model. We used five steps to solve these problems. Firstly, the AAF according to the variation in axial position of the rotor to the stator was calculated and analyzed. Secondly, the torque was calculated under the same conditions to confirm that the system requirements were satisfied. The three-dimensional finite element analysis was used to determine the AAF and torque. Thirdly, the appropriate axial position of the rotor to the stator was suggested considering the analysis results and space inside the housing. Next, the commercial bearing type was chosen so that the total force acting on the bearing was below the bearing load limit to ensure motor stability. Finally, a prototype model was made and tested to confirm the accuracy of the analytical results. Through this study, by using the axial asymmetric PM overhang, the total length of SA was reduced by 5mm and the performance of motor was guaranteed. Full article
(This article belongs to the Special Issue Permanent Magnet Electrical Machines)
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Open AccessArticle
A Power-Forecasting Method for Geographically Distributed PV Power Systems using Their Previous Datasets
Energies 2019, 12(24), 4815; https://doi.org/10.3390/en12244815 - 17 Dec 2019
Viewed by 281
Abstract
The number of photovoltaic (PV) power systems being installed worldwide has been increasing. This has resulted in maintenance of an adequate balance between demand and supply becoming a great concern for power system operators. Forecasting PV power outputs is a promising countermeasure that [...] Read more.
The number of photovoltaic (PV) power systems being installed worldwide has been increasing. This has resulted in maintenance of an adequate balance between demand and supply becoming a great concern for power system operators. Forecasting PV power outputs is a promising countermeasure that has been garnering significant interest. Conventional methods for achieving this often use learning methods, such as neural networks and support vector regression. In contrast, this paper proposes a short-term power-forecasting method for geographically distributed PV systems that uses only their previous output power data. In the proposed method, first, the ratio of the power generation output to the maximum power output value for each observation instance in a designated period for each PV system at a certain date and time is obtained. Then, the future geographical distribution of the ratio is predicted from the temporal change (motion) of the preceding distribution. Finally, the predicted ratio is reconverted into the power output to perform short-term power forecasting. The results of total PV output power prediction in the Kanto area of Japan indicate that the proposed method has an average mean absolute percentage error of 4.23% and root mean square error of 0.69 kW, which verifies its efficacy. Full article
(This article belongs to the Section Solar Energy and Photovoltaic Systems)
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Open AccessArticle
Design and Implementation of a Blockchain-Based Energy Trading Platform for Electric Vehicles in Smart Campus Parking Lots
Energies 2019, 12(24), 4814; https://doi.org/10.3390/en12244814 - 17 Dec 2019
Viewed by 324
Abstract
This paper proposes a blockchain-based energy trading platform for electric vehicles in smart campus parking lots. Smart parking lots are smart places capable of supporting both parking and charging services for electric vehicles. The electric vehicle owner may want to charge energy at [...] Read more.
This paper proposes a blockchain-based energy trading platform for electric vehicles in smart campus parking lots. Smart parking lots are smart places capable of supporting both parking and charging services for electric vehicles. The electric vehicle owner may want to charge energy at a low price and sell it during peak hours at a higher price. The proposed system architecture consists of two layers: the physical infrastructure layer and the cyber infrastructure layer. The physical infrastructure layer represents all of the physical components located in the campus distribution power system, such as electric vehicles charging stations, transformers, and electric feeders, while the cyber infrastructure layer supports the operation of the physical infrastructure layer and enables selling/buying energy among participants. Blockchain technology is a promising candidate to facilitate auditability and traceability of energy transactions among participants. A real case of a parking lot with a realistic parking pattern in a university campus is considered. The system consists of a university control center and various parking lot local controllers (PLLCs). The PLLC broadcasts the electricity demand and the grid price, and each electric vehicle owner decides whether to charge/discharge based on their benefits. The proposed system is implemented on Hyperledger Fabric. Participants, assets, transactions, and smart contracts are defined and discussed. Two scenarios are considered. The first scenario represents energy trading between electric vehicles as sellers and the PLLC as a buyer, while the second scenario involves energy trading between electric vehicles as buyers and the PLLC as a seller. The proposed platform provides profits for participants, as well as enables balancing for the university load demand locally. Full article
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Open AccessArticle
Dynamic Carbon-Constrained EPEC Model for Strategic Generation Investment Incentives with the Aim of Reducing CO2 Emissions
Energies 2019, 12(24), 4813; https://doi.org/10.3390/en12244813 - 17 Dec 2019
Viewed by 278
Abstract
According to the European Union Emissions Trading Scheme, energy system planners are encouraged to consider the effects of greenhouse gases such as CO 2 in their short-term and long-term planning. A decrease in the carbon emissions produced by the power plant will result [...] Read more.
According to the European Union Emissions Trading Scheme, energy system planners are encouraged to consider the effects of greenhouse gases such as CO 2 in their short-term and long-term planning. A decrease in the carbon emissions produced by the power plant will result in a tax decrease. In view of this, the Dynamic carbon-constrained Equilibrium programming equilibrium constraints (DCC-EPEC) Framework is suggested to explore the effects of distinct market models on generation development planning (GEP) on electricity markets over a multi-period horizon. The investment incentives included in our model are the firm contract and capacity payment. The investment issue, which is regarded as a set of dominant producers in the oligopolistic market, is developed as an EPEC optimization problem to reduce carbon emissions. In the suggested DCC-EPEC model, the sum of the carbon emission tax and true social welfare are assumed as the objective function. Investment decisions and the strategic behavior of producers are included at the first level so as to maximize the overall profit of the investor over the scheduling period. The second-level issue is market-clearing, which is resolved by an independent system operator (ISO) to maximize social welfare. A real power network, as a case study, is provided to assess the suggested carbon-constrained EPEC framework. Simulations indicate that firm contracts and capacity payments can initiate the capacity expansion of different technologies to improve the long-term stability of the electricity market. Full article
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Open AccessArticle
Factors Affecting the Corrosive Behavior of Used Cooking Oils and a Non-Edible Fish Oil That Are in Contact with Ferrous Metals
Energies 2019, 12(24), 4812; https://doi.org/10.3390/en12244812 - 17 Dec 2019
Viewed by 279
Abstract
The corrosion behavior of three used cooking oils and one non-edible fish oil was experimentally investigated by the immersion test of iron rods at room temperature. The corrosivity of the tested oils was indirectly determined from the amount of the dissolved iron in [...] Read more.
The corrosion behavior of three used cooking oils and one non-edible fish oil was experimentally investigated by the immersion test of iron rods at room temperature. The corrosivity of the tested oils was indirectly determined from the amount of the dissolved iron in the tested oils after the immersion test. Different factors that affect the corrosive behavior of the tested oils were assessed. Among the tested oils, the fish oil showed the highest amount of dissolved iron owing to its chemical properties such as high water content and acid number. In general, water content and acid number have direct effects on the amount of dissolved iron. The addition of oleic acid to the used cooking oil resulted in a 60% less amount of dissolved iron. It was suggested that the addition of oleic acid prompted the formation of a monolayer, which inhibited the permeation of oxygen and water to the surface of the iron rod. Moreover, the addition of glycerol gave the lowest amount of dissolved iron in the oil sample owing to its ability to bind water molecules and form microemulsions in the presence of a surfactant (for example, oleic acid). Full article
(This article belongs to the collection Bioenergy and Biofuel)
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Open AccessArticle
Roles and Perspectives When Estimating Energy and Environmental Potentials of Urban Consolidation
Energies 2019, 12(24), 4811; https://doi.org/10.3390/en12244811 - 17 Dec 2019
Viewed by 294
Abstract
Urban consolidation centers (UCCs) are presumed to provide more efficient goods distribution in cities and lead to decreased environmental impact and energy usage. There is, however, limited knowledge as to the actual performance of UCCs, and what roles and perspectives the involved actors [...] Read more.
Urban consolidation centers (UCCs) are presumed to provide more efficient goods distribution in cities and lead to decreased environmental impact and energy usage. There is, however, limited knowledge as to the actual performance of UCCs, and what roles and perspectives the involved actors have in the performance measurement. The overall aim of this paper is to investigate the roles and perspectives of involved actors when estimating and evaluating the performance of UCCs. The article is based on a study of one case that evaluates the performance of a UCC involving several actors. Interviews were triangulated with documents from the case. The results showed that actors have different roles in performance measurements and even if they share a mutual interest in conducting the measurements, they did not share opinions regarding factors such as system limits or performance indicators. The study provides a deeper understanding of the importance of inter-organizational interaction when conducting performance measurements. The study provides additional insights into the roles of the actors and their perspectives in logistics performance measurement that targets energy usage and environmental impact. These aspects are seldom addressed in less complex estimations or mathematical modelling estimations. Full article
Open AccessArticle
Enhancement on the Fault Ride through Capability of Power Distribution Systems Linked by Distributed Generation due to the Impedance of Superconducting Fault Current Limiters
Energies 2019, 12(24), 4810; https://doi.org/10.3390/en12244810 - 17 Dec 2019
Viewed by 234
Abstract
Recently, studies on connecting distributed generation (DG) to power distribution systems through DC links have been actively conducted. When a fault in feeder of this power distribution system occurs, a voltage dip can happen in the grid. In order to prevent voltage dips, [...] Read more.
Recently, studies on connecting distributed generation (DG) to power distribution systems through DC links have been actively conducted. When a fault in feeder of this power distribution system occurs, a voltage dip can happen in the grid. In order to prevent voltage dips, there are several solutions such as the application of a superconducting fault current limiter (SFCL). If a SFCL with a larger impedance is applied, the voltage dip of the grid is effectively prevented. However, this action can bring about the malfunction or the delayed operation of the over-current relay (OCR) due to the decreased fault current, which causes another problem of protection coordination between the protective relays. On the other hand, if the impedance of the SFCL is too low, excessive reactive power is supplied by the fault ride-through (FRT) regulation and the active power is reduced. This causes an active power imbalance on the DC link and increases the DC link’s voltage. As previous solutions to prevent the rise of DC links’ voltage, the deloading method and the application of a chopper resistor have been suggested. In this paper, a technique called active power tracking control (APTC), was proposed to suppress the rise of DC links’ voltage. Case studies considering the impedance of SFCL in the constructed power distribution system were carried out, and the rise of DC links’ voltage could be effectively suppressed without any significant delay in the operation of the OCR. This study is expected to solve both the voltage dip of the grid and the rise of DC links’ voltage when distributed generation is connected to a grid. Full article
(This article belongs to the Special Issue High Voltage Converters and Smartgrids Applications)
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Open AccessArticle
Simplified Layer Model for Solid Particle Clusters in Product Oil Pipelines
Energies 2019, 12(24), 4809; https://doi.org/10.3390/en12244809 - 17 Dec 2019
Viewed by 270
Abstract
Pipe corrosion caused by the pressure tests using water before starting the normal operation occurs often in Chinese product oil pipelines because of remaining water. To explore the migration of the corrosion impurities in the product oil pipelines, this study started from the [...] Read more.
Pipe corrosion caused by the pressure tests using water before starting the normal operation occurs often in Chinese product oil pipelines because of remaining water. To explore the migration of the corrosion impurities in the product oil pipelines, this study started from the force balance principle and considered the entire particle cluster as the research object. This paper established a one-dimensional migration model, and proposed the Froude number equality criterion to calculate the particle cluster length in the equilibrium state. The proposed criterion was verified by experiments. A loop was built to conduct the tests and obtain the migration velocities of the particle cluster from the non-equilibrium state to the equilibrium state in the pipeline. The proposed model was verified using the experimental data. Verification results demonstrate that the model can describe the development process from the non-equilibrium state to the equilibrium state of particle clusters after sudden external disturbance and accurately predict some important parameters, including the velocity of the particle cluster in the equilibrium state and the critical velocity that leads to the transition from fixed bed flow to moving bed flow. The model provides the theoretical basis and calculation method to remove corrosion impurities from product oil pipelines. Full article
(This article belongs to the Special Issue Selected Papers from the 16th UK Heat Transfer Conference (UKHTC2019))
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Open AccessArticle
Analysis of Local Measurement-Based Algorithms for Fault Detection in a Multi-Terminal HVDC Grid
Energies 2019, 12(24), 4808; https://doi.org/10.3390/en12244808 - 17 Dec 2019
Viewed by 230
Abstract
One of the most important challenges of developing multi-terminal (MT) high voltage direct current (HVDC) grids is the system performance under fault conditions. It must be highlighted that the operating time of the protection system needs to be shorter than a few milliseconds. [...] Read more.
One of the most important challenges of developing multi-terminal (MT) high voltage direct current (HVDC) grids is the system performance under fault conditions. It must be highlighted that the operating time of the protection system needs to be shorter than a few milliseconds. Due to this restrictive requirement of speed, local measurement based algorithms are mostly used as primary protection since they present an appropriate operation speed. This paper focuses on the analysis of local measurement based algorithms, specifically overcurrent, undervoltage, rate-of-change-of-current, and rate-of-change-of-voltage algorithms. A review of these fault detection algorithms is presented. Furthermore, these algorithms are applied to a multi-terminal grid, where the influence of fault location and fault resistance is assessed. Then, their performances are compared in terms of detection speed and maximum current interrupted by the HVDC circuit breakers. This analysis aims to enhance the protection systems by facilitating the selection of the most suitable algorithm for primary or backup protection systems. In addition, two new fault type identification algorithms based on the rate-of-change-of-voltage and rate-of-change-of-current are proposed and analyzed. The paper finally includes a comparison between the previously reviewed local measurement based algorithms found in the literature and the simulation results of the present work. Full article
(This article belongs to the Special Issue Control and Protection of HVDC-Connected Offshore Wind Power Plants)
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Open AccessArticle
Influence of Manufacturing and Assembly Defects and the Quality of Materials on the Performance of an Axial-Flux Switched Reluctance Machine
Energies 2019, 12(24), 4807; https://doi.org/10.3390/en12244807 - 17 Dec 2019
Viewed by 251
Abstract
This paper investigated the influence of manufacturing and assembly defects and the quality of materials on the performance of an axial-flux switched reluctance machine (AFSRM). An AFSRM drive was designed and built for the in-wheel propulsion of an electric scooter. The motor was [...] Read more.
This paper investigated the influence of manufacturing and assembly defects and the quality of materials on the performance of an axial-flux switched reluctance machine (AFSRM). An AFSRM drive was designed and built for the in-wheel propulsion of an electric scooter. The motor was tested according to the standard IEC 60349-Part 1, but the obtained results were below the expected result. The causes of the discrepancy between the simulated and experimental results were analyzed. After an exhaustive study, manufacturing and assembly deficiencies and the quality of materials were identified as the main causes of the mentioned discrepancies. Static torque was used to assess the impact of the different causes in these discrepancies. Finally, some recommendations are proposed to improve the construction of this kind of machine. Full article
(This article belongs to the Special Issue Design and Analysis of Electric Machines)
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Open AccessArticle
On the Equivalence of the Switched Inductor and the Tapped Inductor Converters and its Application to Small Signal Modelling
Energies 2019, 12(24), 4806; https://doi.org/10.3390/en12244806 - 17 Dec 2019
Viewed by 190
Abstract
Switched inductor (SI) converters are popular in applications requiring a steeper conversion ratio. However, these converters operate a twin inductor switching cell, which complicates the small-signal modeling. This paper proposes an expeditious small-signal analysis method to model the SI converters. The offered modeling [...] Read more.
Switched inductor (SI) converters are popular in applications requiring a steeper conversion ratio. However, these converters operate a twin inductor switching cell, which complicates the small-signal modeling. This paper proposes an expeditious small-signal analysis method to model the SI converters. The offered modeling approach is hinged on the analogy existing between the SI converters and certain Tapped Inductor (TI) converters. It is suggested here that by virtue of the analogy of the SI converters and TI converters the small-signal model of the SI converter is identical to that of its ideal TI counterpart. Hence, the recently developed Tapped Inductor Switcher (TIS) methodology can be applied to the modeling of the SI converters as well. As an example, the small-signal model of the Switched Inductor Buck converter is obtained. Theoretical analysis was confirmed by simulation and experimental results. In addition, several other SI converters and their TI counterparts are identified. Full article
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Open AccessArticle
Modeling and Controlling of Temperature and Humidity in Building Heating, Ventilating, and Air Conditioning System Using Model Predictive Control
Energies 2019, 12(24), 4805; https://doi.org/10.3390/en12244805 - 17 Dec 2019
Viewed by 298
Abstract
Nowadays, by huge improvements in industrial control and the necessity of efficient energy consumption for buildings, unified managing systems are established to monitor and control mechanical equipment and energy usage. One of the main portions of the building management system (BMS) is the [...] Read more.
Nowadays, by huge improvements in industrial control and the necessity of efficient energy consumption for buildings, unified managing systems are established to monitor and control mechanical equipment and energy usage. One of the main portions of the building management system (BMS) is the cooling and heating equipment called heating and ventilation and air-conditioning (HVAC). Based on temperature slow dynamic and presented uncertainty in modeling, a model predictive control (MPC) strategy to track both temperature and humidity is proposed in this study. The main goal of this study is to provide a framework to describe temperature and humidity elements required for dynamic modeling. Following that, by utilizing a predictive approach, a control strategy is obtained, which optimizes the tracking error of two interactional channel and performs the effort control by minimizing the optimization index. Other articles have mostly only had control over the temperature variable, but in our article, we tried to study the equations of temperature and humidity as well as their interference and according to the ASHRAE standard, both temperature and humidity controls must be accurate. The humidity was the novelty in our article. Simulation results proved the effectiveness of the proposed approach compared to the conventional proportional-integral controller. Evidently, the key idea behind the control objective is providing the comfort condition while consuming the least possible energy. Full article
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Open AccessArticle
An Ultrasonic Pulse-Echo Method to Detect Internal Defects in Epoxy Composite Insulation
Energies 2019, 12(24), 4804; https://doi.org/10.3390/en12244804 - 17 Dec 2019
Viewed by 220
Abstract
Voids or cracks in basin insulators inside a GIS (gas-insulated metal-enclosed switchgear) could trigger partial discharges or surface flashover under electrical stresses, threatening safe GIS operation. For this paper, some epoxy composite specimens were made from similar materials and manufacturing processes to make [...] Read more.
Voids or cracks in basin insulators inside a GIS (gas-insulated metal-enclosed switchgear) could trigger partial discharges or surface flashover under electrical stresses, threatening safe GIS operation. For this paper, some epoxy composite specimens were made from similar materials and manufacturing processes to make 252 kV GIS basin insulators. Some voids with different diameters or cracks with different diameters and orientations were artificially made in the specimens with different thicknesses. An ultrasonic pulse-echo system was set up, and ultrasonic tests were carried out on the specimens with voids or cracks. A method to calculate the depth of a defect was proposed by the propagation time of defect reflected waves. The results showed that a depth of 50 mm, a diameter φ of 2 mm void, and a diameter φ of 1 mm crack in epoxy composite insulation were detected by the ultrasonic system using a 1 MHz transducer. Full article
(This article belongs to the Section Electrical Power and Energy System)
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Open AccessArticle
Research on Model Predictive Control of IPMSM Based on Adaline Neural Network Parameter Identification
Energies 2019, 12(24), 4803; https://doi.org/10.3390/en12244803 - 17 Dec 2019
Viewed by 280
Abstract
This paper reports the optimal control problem on the interior permanent magnet synchronous motor (IPMSM) systems. The control performance of the traditional model predictive control (MPC) controller is ruined due to the parameter uncertainty and mismatching. In order to solve the problem that [...] Read more.
This paper reports the optimal control problem on the interior permanent magnet synchronous motor (IPMSM) systems. The control performance of the traditional model predictive control (MPC) controller is ruined due to the parameter uncertainty and mismatching. In order to solve the problem that the MPC algorithm has a large dependence on system parameters, a method which integrates MPC control method and parameter identification for IPMSM is proposed. In this method, the d-q axis inductances and rotor permanent magnet flux of IPMSM motor are identified by the Adaline neural network algorithm, and then, the identification results are applied to the predictive controller and maximum torque per ampere (MTPA) module. The experimental results show that the optimized MPC control proposed in this paper has a good steady state and robust performance. Full article
(This article belongs to the Special Issue Control and Monitoring of Permanent Magnet Synchronous Machines)
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Open AccessArticle
A Never-Ending Learning Method for Fault Diagnostics in Energy Systems Operating in Evolving Environments
Energies 2019, 12(24), 4802; https://doi.org/10.3390/en12244802 - 16 Dec 2019
Cited by 1 | Viewed by 366
Abstract
Condition monitoring (CM) in the energy industry is limited by the lack of pre-classified data about the normal and/or abnormal plant states and the continuous evolution of its operational conditions. The objective is to develop a CM model able to: (1) Detect abnormal [...] Read more.
Condition monitoring (CM) in the energy industry is limited by the lack of pre-classified data about the normal and/or abnormal plant states and the continuous evolution of its operational conditions. The objective is to develop a CM model able to: (1) Detect abnormal conditions and classify the type of anomaly; (2) recognize novel plant behaviors; (3) select representative examples of the novel classes for labeling by an expert; (4) automatically update the CM model. A CM model based on the never-ending learning paradigm is developed. It develops a dictionary containing labeled prototypical subsequences of signal values representing normal conditions and anomalies, which is continuously updated by using a dendrogram to identify groups of similar subsequences of novel classes and to select those subsequences to be labelled by an expert. A 1-nearest neighbor classifier is trained to online detect abnormal conditions and classify their types. The proposed CM model is applied to a synthetic case study and a real case study concerning the monitoring of the tank pressure of an aero derivative gas turbine lube oil system. The CM model provides satisfactory performances in terms of classification accuracy, while remarkably reducing the expert efforts for data labeling and model (periodic) updating. Full article
(This article belongs to the Section Electrical Power and Energy System)
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Open AccessArticle
Transfer Path Analysis for Semisubmersible Platforms Based on Noisy Measured Data
Energies 2019, 12(24), 4801; https://doi.org/10.3390/en12244801 - 16 Dec 2019
Viewed by 299
Abstract
A new energy transfer path analysis (TPA) method that aims to analyze the transfer path of components with characteristic frequencies in semisubmersible platform structures is proposed in this paper. Due to the complexity of semisubmersible platforms, traditional TPA methods based on measurements are [...] Read more.
A new energy transfer path analysis (TPA) method that aims to analyze the transfer path of components with characteristic frequencies in semisubmersible platform structures is proposed in this paper. Due to the complexity of semisubmersible platforms, traditional TPA methods based on measurements are no longer applicable. In the proposed method, the structure is considered to be a “source-path-receiver” system and the vibration signals from the source-points are analyzed first to determine the characteristic components. Then, the signals from the source-points and the receiver-points are decomposed by introducing a state–space model. Through correlation functions, the characteristic components can be extracted, and the transfer path can be obtained by calculating the transmissibility functions. By using transmissibility functions, the proposed method only relies on the output responses and avoids the measurement of force and transfer functions. Three examples, one numerical example containing a two-degree-of-freedom (2-DOF) model and a 5-DOF model, one experiment implemented on a barge, and the data from a dynamic positioning (DP) cabin of a semisubmersible platform were used to investigate the performance of the proposed method. The results show that the proposed method can be used to assess the transfer path quantitatively and has potential value of application in engineering. Full article
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Open AccessArticle
The Impact of Economic Growth, FDI and Energy Intensity on China’s Manufacturing Industry’s CO2 Emissions: An Empirical Study Based on the Fixed-Effect Panel Quantile Regression Model
Energies 2019, 12(24), 4800; https://doi.org/10.3390/en12244800 - 16 Dec 2019
Viewed by 274
Abstract
Since the reform and opening-up, China’s CO2 emissions have increased dramatically, and it has become the world’s largest CO2 emission and primary energy consumption country. The manufacturing industry is one of the biggest contributors to CO2 emission, and determining the [...] Read more.
Since the reform and opening-up, China’s CO2 emissions have increased dramatically, and it has become the world’s largest CO2 emission and primary energy consumption country. The manufacturing industry is one of the biggest contributors to CO2 emission, and determining the drivers of CO2 emissions are essential for effective environmental policy. China is also a vast transition economy with great regional differences. Therefore, based on the data of China’s provincial panel from 2000 to 2013 and the improved STIRPAT model, this paper studies the impact of economic growth, foreign direct investment (FDI) and energy intensity on China’s manufacturing carbon emissions through the fixed-effect panel quantile regression model. The results show that the effects of economic growth, FDI and energy intensity on carbon emissions of the manufacturing industry are different in different levels and regions, and they have apparent heterogeneity. In particular, economic growth plays a decisive role in the CO2 emissions of the manufacturing industry. Economic growth has a positive impact on the carbon emissions of the manufacturing industry; specifically, a higher impact on high carbon emission provinces. Besides, FDI has a significant positive effect on the upper emission provinces of the manufacturing industry, which proves that there is a pollution paradise hypothesis in China’s manufacturing industry, but no halo effect hypothesis. The reduction of energy intensity does not have a positive effect on the reduction of carbon emissions. The higher impact of the energy intensity of upper emission provinces on carbon emissions from their manufacturing industry, shows that there is an energy rebound effect in China’s manufacturing industry. Finally, our study confirms that China’s manufacturing industry has considerable space for emission reduction. The results also provide policy recommendations for policymakers. Full article
(This article belongs to the Special Issue Energy Markets and Economics Ⅱ)
Open AccessArticle
Multifunctional Distributed MPPT Controller for 3P4W Grid-Connected PV Systems in Distribution Network with Unbalanced Loads
Energies 2019, 12(24), 4799; https://doi.org/10.3390/en12244799 - 16 Dec 2019
Cited by 1 | Viewed by 317
Abstract
The integration of photovoltaic (PV) systems with three-phase four-wire (3P4W) distribution networks has imposed several challenges related to existing unbalanced loads, reactive power generation and harmonics content. In this paper, a multifunctional distributed maximum power point (MPPT) controller for grid integration of PV [...] Read more.
The integration of photovoltaic (PV) systems with three-phase four-wire (3P4W) distribution networks has imposed several challenges related to existing unbalanced loads, reactive power generation and harmonics content. In this paper, a multifunctional distributed maximum power point (MPPT) controller for grid integration of PV systems is proposed. The proposed distributed MPPT controller is developed based on employing a four-leg three-level T-type multilevel inverter. The proposed inverter performs multifunctionalities, including distributed MPPT, neutral current compensation for the unbalanced loads, supplying reactive power into the grid and the grid integration. Moreover, the proposed inverter overcomes the stochastic behavior of both the PV generation with partial shading problems and its operation with unbalanced loads as well. Furthermore, the new proposed controller injects sinusoidal output currents with decreased levels of total harmonic distortion (THD) into the grid. The tested case study is investigated for the various operating scenarios of PV generation and load demands. The results and tabulated performance comparisons have proven the superior performance of the proposed multifunctional PV generation system. The results show the ability of the proposed controller to efficiently extract distributed MPPT for all PV modules at all the tested scenarios. Additional improvement of the energy efficiency is achieved through the elimination of the neutral current due to existing unbalanced loads. Full article
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The Smart City Business Model Canvas—A Smart City Business Modeling Framework and Practical Tool
Energies 2019, 12(24), 4798; https://doi.org/10.3390/en12244798 - 16 Dec 2019
Viewed by 445
Abstract
Cities are challenged with increasing population growth and need to implement smart solutions to become more resilient to economic, environmental, and social challenges posed by ongoing urbanization. This study reviewed business model development frameworks and developed a practical tool to help cities assess [...] Read more.
Cities are challenged with increasing population growth and need to implement smart solutions to become more resilient to economic, environmental, and social challenges posed by ongoing urbanization. This study reviewed business model development frameworks and developed a practical tool to help cities assess business models by adapting components of the Business Model Canvas (BMC) and adding new ones that operationalize the smart city dimensions. The Smart City BMC (SC-BMC) proposed provides a practical framework that supports developing and communicating a more holistic and integrated view of a smart city business model. It also supports creatively innovating toward more sustainable value creation. As a framework, the SC-BMC bridges sustainable value creation for business model development and smart city innovation. Full article
(This article belongs to the Special Issue Energy Economics and Innovation of Smart Cities)
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Open AccessArticle
Analysis and Introduction of Effective Permeability with Additional Air-Gaps on Wireless Power Transfer Coils for Electric Vehicle Based on SAE J2954 Recommended Practice
Energies 2019, 12(24), 4797; https://doi.org/10.3390/en12244797 - 16 Dec 2019
Viewed by 288
Abstract
The wireless power transfer (WPT) method for electric vehicles (EVs) is becoming more popular, and to ensure the interoperability of WPT systems, the Society of Automotive Engineers (SAE) established the J2954 recommended practice (RP). It includes powering frequency, electrical parameters, specifications, testing procedures, [...] Read more.
The wireless power transfer (WPT) method for electric vehicles (EVs) is becoming more popular, and to ensure the interoperability of WPT systems, the Society of Automotive Engineers (SAE) established the J2954 recommended practice (RP). It includes powering frequency, electrical parameters, specifications, testing procedures, and other contents for EV WPT. Specifically, it describes the ranges of self-inductances of the transmitting coil, the receiving coil, and coupling coefficient (k), as well as the impedance matching values of the WPT system. Following the electrical parameters listed in SAE J2954 RP is crucial to ensure the EV wireless charging system is interoperable. This paper introduces a method for adjusting the effective permeability of the ferrite blocks in the standard model, to tune the self-inductance of the coils as well as the coupling coefficient. To guarantee the given values of the self-inductance of the coil and coupling coefficient matched those in the standard, we slightly modified the air-gap between the ferrite tiles in a specific region. Based on this method, it was possible to successfully tune the self-inductance of the transmitting coil and receiving coil as well as the coupling coefficient. The proposed method was verified by simulation and experimental measurements. Full article
(This article belongs to the Special Issue Wireless Power for Electric Vehicles)
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Open AccessArticle
Fuzzy Logic Control for Low-Voltage Ride-Through Single-Phase Grid-Connected PV Inverter
Energies 2019, 12(24), 4796; https://doi.org/10.3390/en12244796 - 16 Dec 2019
Viewed by 261
Abstract
This paper presents a control scheme for a photovoltaic (PV) system that uses a single-phase grid-connected inverter with low-voltage ride-through (LVRT) capability. In this scheme, two PI regulators are used to adjust the power angle and voltage modulation index of the inverter; therefore, [...] Read more.
This paper presents a control scheme for a photovoltaic (PV) system that uses a single-phase grid-connected inverter with low-voltage ride-through (LVRT) capability. In this scheme, two PI regulators are used to adjust the power angle and voltage modulation index of the inverter; therefore, controlling the inverter’s active and reactive output power, respectively. A fuzzy logic controller (FLC) is also implemented to manage the inverter’s operation during the LVRT operation. The FLC adjusts (or de-rates) the inverter’s reference active and reactive power commands based on the grid voltage sag and the power available from the PV system. Therefore, the inverter operation has been divided into two modes: (i) Maximum power point tracking (MPPT) during the normal operating conditions of the grid, and (ii) LVRT support when the grid is operating under faulty conditions. In the LVRT mode, the de-rating of the inverter active output power allows for injection of some reactive power, hence providing voltage support to the grid and enhancing the utilization factor of the inverter’s capacity. The proposed system was modelled and simulated using MATLAB Simulink. The simulation results showed good system performance in response to changes in reference power command, and in adjusting the amount of active and reactive power injected into the grid. Full article
(This article belongs to the Special Issue Power Electronics in Renewable Energy Systems Ⅱ)
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Open AccessArticle
Formation of Conductive Oxide Scale on 33NK and 47ND Interconnector Alloys for Solid Oxide Fuel Cells
Energies 2019, 12(24), 4795; https://doi.org/10.3390/en12244795 - 16 Dec 2019
Viewed by 317
Abstract
: Two grades of chromium-free alloys were studied in order to apply them as interconnectors for solid oxide fuel cells. The surface modification methods were proposed for each alloy with the purpose of forming of oxide scales considering the required physicochemical properties. Investigations [...] Read more.
: Two grades of chromium-free alloys were studied in order to apply them as interconnectors for solid oxide fuel cells. The surface modification methods were proposed for each alloy with the purpose of forming of oxide scales considering the required physicochemical properties. Investigations of the structure and properties of the obtained oxide scales were performed and the efficiency of the chosen surface modification methods was approved. The samples with the surface modification exhibited higher conductivity values in comparison with the nonmodified samples. A compatibility study of samples with surface modification and glass sealant of chosen composition was accomplished. The modified samples demonstrated good adhesion during testing and electrical resistance less than 40 mOhm/cm2 at 850 °C in air, which allowed us to recommend these alloys with respective modified oxide scales as interconnectors for SOFC. Full article
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Open AccessArticle
Financial Impacts of Net-Metered Distributed PV on a Prototypical Western Utility’s Shareholders and Ratepayers
Energies 2019, 12(24), 4794; https://doi.org/10.3390/en12244794 - 16 Dec 2019
Viewed by 223
Abstract
Distributed solar photovoltaic (DPV) under net-energy metering with volumetric retail electricity pricing has raised concerns among utilities and regulators about adverse financial impacts for shareholders and ratepayers. Using a pro forma financial model, we estimate the financial impacts of different DPV deployment levels [...] Read more.
Distributed solar photovoltaic (DPV) under net-energy metering with volumetric retail electricity pricing has raised concerns among utilities and regulators about adverse financial impacts for shareholders and ratepayers. Using a pro forma financial model, we estimate the financial impacts of different DPV deployment levels on a prototypical Western U.S. investor-owned utility under a varied set of operating conditions that would be expected to affect the value of DPV. Our results show that the financial impacts on shareholders and ratepayers increase as the level of DPV deployment increases, though the magnitude is small even at high DPV penetration levels. Even rather dramatic changes in DPV value result in modest changes to shareholder and ratepayer impacts, but the impacts on the former are greater than the latter (in percentage terms). The range of financial impacts are driven by differences in the amount of incremental capital investment that is deferred, as well as the amount of incremental distribution operating expenses that are incurred. While many of the impacts appear relatively small (on a percentage basis), they demonstrate how the magnitude of impacts depend critically on utility physical, financial, and operating characteristics. Full article
(This article belongs to the Special Issue Operation, Regulation and Planning of Power and Natural Gas Systems)
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Open AccessArticle
Power to Hydrogen Through Polygeneration Systems Based on Solid Oxide Cell Systems
Energies 2019, 12(24), 4793; https://doi.org/10.3390/en12244793 - 16 Dec 2019
Viewed by 243
Abstract
This study presents the design and analysis of a novel plant based on reversible solid oxide cells driven by wind turbines and integrated with district heating, absorption chillers and water distillation. The main goal is produce hydrogen from excess electricity generated by the [...] Read more.
This study presents the design and analysis of a novel plant based on reversible solid oxide cells driven by wind turbines and integrated with district heating, absorption chillers and water distillation. The main goal is produce hydrogen from excess electricity generated by the wind turbines. The proposed design recovers the waste heat to generate cooling, freshwater and heating. The different plant designs proposed here make it possible to alter the production depending on the demand. Further, the study uses solar energy to generate steam and regulate the heat production for the district heating. The study shows that the plant is able to produce hydrogen at a rate of about 2200 kg/day and the hydrogen production efficiency of the plant reaches about 39%. The total plant efficiency (energy efficiency) will be close to 47% when heat, cool and freshwater are accounted for. Neglecting the heat input through solar energy to the system, then hydrogen production efficiency will be about 74% and the total plant efficiency will be about 100%. In addition, the study analyses the plant performance versus wind velocity in terms of heating, cooling and freshwater generation. Full article
(This article belongs to the Special Issue Advances in Hydrogen Production and Hydrogen Separation)
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Open AccessArticle
Modelling of Refrigerant Distribution in an Oil-Free Refrigeration System using R134a
Energies 2019, 12(24), 4792; https://doi.org/10.3390/en12244792 - 16 Dec 2019
Viewed by 289
Abstract
Increasing number of refrigeration units has led to an increase of CO2 emissions and the destruction of the ozone layer. Using low global warming potential (GWP) refrigerants, improving the efficiency of vapour compression refrigeration (VCR) units, and minimising refrigerant leakages can reduce [...] Read more.
Increasing number of refrigeration units has led to an increase of CO2 emissions and the destruction of the ozone layer. Using low global warming potential (GWP) refrigerants, improving the efficiency of vapour compression refrigeration (VCR) units, and minimising refrigerant leakages can reduce the global warming effect. Investigating the refrigerant distribution under varied operating conditions can provide a deeper understanding of refrigerant charge optimization. This study proposed a model of refrigerant mass distribution in a prototype oil-free VCR system using a linear compressor with variable strokes and R134a. The absence of the oil lubricant allows the adoption of compact heat exchangers, such as micro-channels, so that the total refrigerant charge can be reduced significantly. The predicted total refrigerant charge has a Mean Absolute Percentage Error (MAPE) of 3.7%. The simulation results indicate that refrigerant distributed in the condenser is most sensitive to operating conditions and total refrigerant charges. The refrigerant accumulated in the condenser is 6.8% higher at a total refrigerant charge of 0.33 kg than that of 0.22 kg. For a total refrigerant charge of 0.33 kg, 72.1% of the total refrigerant can accumulate in the condenser. At a fixed pressure ratio, the refrigerant as a two-phase form in the condenser decreases slightly with the increase of compressor strokes, resulting in a larger mass flow rate, thus cooling capacity. The present model can be adapted for optimization of a refrigeration unit and its components. Full article
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Open AccessArticle
Optimization of Programmed Temperature Vaporization Injection for Determination of Polycyclic Aromatic Hydrocarbons from Diesel Combustion Process
Energies 2019, 12(24), 4791; https://doi.org/10.3390/en12244791 - 16 Dec 2019
Cited by 1 | Viewed by 233
Abstract
In this study, programmed temperature vaporization in the solvent vent mode (PTV-SV) of gas chromatography-mass spectrometry was optimized and validated for the analysis of particle-phase and gas-phase polycyclic aromatic hydrocarbons from diesel engine combustion. Because of the large number of experimental and response [...] Read more.
In this study, programmed temperature vaporization in the solvent vent mode (PTV-SV) of gas chromatography-mass spectrometry was optimized and validated for the analysis of particle-phase and gas-phase polycyclic aromatic hydrocarbons from diesel engine combustion. Because of the large number of experimental and response variables to be studied, central composite inscribed design was used to optimize the PTV-SV injection factors, including initial inlet temperature, vaporization flow and time. The optimized PTV-SV method was validated by linearity, accuracy and sensitivity. For the 16 Polycyclic aromatic hydrocarbons (PAHs) studied, the correlation coefficients for the calibration plots of peak areas versus concentrations (0.5–300 ng mL−1) ranged from 0.9812–0.9998. Limits of detection ranged from 0.016–20,130.375 ng mL−1, and limits of quantification ranged from 0.055–1.25 ng mL−1. The optimized method was used for the analysis of real samples collected from a diesel engine, which included particle-phase and gas-phase PAHs. The results showed that the improved PTV-SV method was satisfying for simultaneously identifying and quantifying PAHs produced during diesel combustion. Full article
(This article belongs to the Section Energy and Environment)
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Open AccessArticle
Internet of Energy (IoE) and High-Renewables Electricity System Market Design
Energies 2019, 12(24), 4790; https://doi.org/10.3390/en12244790 - 16 Dec 2019
Viewed by 288
Abstract
The growing importance of the Internet of Energy (IoE) brands the high-renewables electricity system a realistic scenario for the future electricity system market design. In general, the whole gist behind the IoE is developed upon a somewhat broader idea encompassing the so-called “Internet [...] Read more.
The growing importance of the Internet of Energy (IoE) brands the high-renewables electricity system a realistic scenario for the future electricity system market design. In general, the whole gist behind the IoE is developed upon a somewhat broader idea encompassing the so-called “Internet of Things” (IoT), which envisioned a plethora of household appliances, utensils, clothing, smart trackers, smart meters, and vehicles furnished with tiny devices. These devices would record all possible data from all those objects in real time and allow for a two-way exchange of information that makes it possible to optimize their use. IoT employs the Internet Protocol (IP) and the worldwide web (WWW) network for transferring information and data through various types of networks and gateways as well as sensor technologies. This paper presents an outline stemming from the implications of the high-renewables electric system that would employ the Internet of Energy (IoE). In doing so, it focuses on the implications that IoE brings into the high-renewables electricity market inhabited by smart homes, smart meters, electric vehicles, solar panels, and wind turbines, such as the peer-to-peer (P2P) energy exchange between prosumers, optimization of location of charging stations for electric vehicles (EVs), or the information and energy exchange in the smart grids. We show that such issues as compatibility, connection speed, and most notoriously, trust in IoE applications among households and consumers would play a decisive role in the transition to the high-renewables electricity systems of the 21st century. Our findings demonstrate that the decentralized approach to energy system effective control and operation that is offered by IoE is highly likely to become ubiquitous as early as 2030. Since it may be optimal that large-scale rollouts start in the early 2020s, some form of government incentives and funding (e.g. subsidies for installing wind turbines or solar panels or special feed-in-tariffs for buying renewable energy) may be needed for the energy market to make early progress in embracing more renewables and in reducing the costs of later investments. In addition, there might be some other alternative approaches aimed at facilitating this development. We show that the objective is to minimize the overall system cost, which consists of the system investment cost and the system operating cost, subject to CO2 emissions constraints and the operating constraints of generation units, network assets, and novel carbon-free technologies, which is quite cumbersome given the trend in consumption and the planned obsolescence. This can be done through increasing energy efficiency, developing demand side management strategies, and improving matching between supply and demand side, just to name a few possibilities. Full article
(This article belongs to the Special Issue Market Design for a High-Renewables Electricity System)
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Open AccessArticle
Open Source Data for Gross Floor Area and Heat Demand Density on the Hectare Level for EU 28
Energies 2019, 12(24), 4789; https://doi.org/10.3390/en12244789 - 16 Dec 2019
Viewed by 284
Abstract
The planning of heating and cooling supply and demand is key to reaching climate and sustainability targets. At the same time, data for planning are scarce for many places in Europe. In this study, we developed an open source dataset of gross floor [...] Read more.
The planning of heating and cooling supply and demand is key to reaching climate and sustainability targets. At the same time, data for planning are scarce for many places in Europe. In this study, we developed an open source dataset of gross floor area and energy demand for space heating and hot water in residential and tertiary buildings at the hectare level for EU28 + Norway, Iceland, and Switzerland. This methodology is based on a top-down approach, starting from a consistent dataset at the country level (NUTS 0), breaking this down to the NUTS 3 level and further to the hectare level by means of a series of regional indicators. We compare this dataset with data from other sources for 20 places in Europe. This process shows that the data for some places fit well, while for others, large differences up to 45% occur. The discussion of these results shows that the other data sources used for this comparison are also subject to considerable uncertainties. A comparison of the developed data with maps based on municipal building stock data for three cities shows that the developed dataset systematically overestimates the gross floor area and heat demand in low density areas and vice versa. We conclude that these data are useful for strategic purposes on aggregated level of larger regions and municipalities. It is especially valuable in locations where no detailed data is available. For detailed planning of heating and cooling infrastructure, local data should be used instead. We believe our work contributes towards a transparent, open source dataset for heating and cooling planning that can be regularly updated and is easily accessible and usable for further research and planning activities. Full article
(This article belongs to the Special Issue Open Data and Energy Analytics)
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Open AccessArticle
Profitability Analysis and Capital Cost Estimation of a Thermochemical Energy Storage System Utilizing Fluidized Bed Reactors and the Reaction System MgO/Mg(OH)2
Energies 2019, 12(24), 4788; https://doi.org/10.3390/en12244788 - 16 Dec 2019
Viewed by 267
Abstract
The storage of industrial waste heat through thermochemical energy storage (TCES) shows high potential to reduce the dependency on fossil fuels. In this paper the capital cost investment of a TCES system utilizing fluidized bed reactors and the reaction system MgO/Mg(OH) 2 is [...] Read more.
The storage of industrial waste heat through thermochemical energy storage (TCES) shows high potential to reduce the dependency on fossil fuels. In this paper the capital cost investment of a TCES system utilizing fluidized bed reactors and the reaction system MgO/Mg(OH) 2 is estimated and a profitability analysis is performed. The study estimate is based on a simulation study that considers the mass and energy balance of the proposed preliminary heat storage and release processes utilizing fluidized bed reactors. Furthermore, transport, operation and maintenance as well as utility costs were estimated in order to evaluate the profitability of the system. It is concluded that for the selected boundary conditions, the specific investment costs per kW stored heat are approximately 900 €/kW and that the systems should not be installed at sites where less than around 5 MW of waste heat are available. Finally, a sensitivity analysis was conducted, to identify the key process and economic parameters critical for a positive net present value. Full article
(This article belongs to the Special Issue Development in Thermochemical Energy Storage)
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