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Energies, Volume 6, Issue 2 (February 2013), Pages 566-1180

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Open AccessEditorial Energies Best Paper Award 2013
Energies 2013, 6(2), 1178-1180; https://doi.org/10.3390/en6021178
Received: 20 February 2013 / Accepted: 22 February 2013 / Published: 22 February 2013
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Abstract
To better recognize the outstanding papers in the area of energy technologies and applications published in Energies, we announce the institution of an annual award. We are therefore pleased to announce the first “Energies Best Paper Award” for 2013. Nominations were
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To better recognize the outstanding papers in the area of energy technologies and applications published in Energies, we announce the institution of an annual award. We are therefore pleased to announce the first “Energies Best Paper Award” for 2013. Nominations were made by the Editor-in-Chief and Editorial Board members from all papers published in 2009. The awards are issued to reviews and full research articles separately. [...] Full article
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Open AccessArticle Evaluation of Power Generation Efficiency of Cascade Hydropower Plants: A Case Study
Energies 2013, 6(2), 1165-1177; https://doi.org/10.3390/en6021165
Received: 26 November 2012 / Revised: 30 January 2013 / Accepted: 6 February 2013 / Published: 22 February 2013
Cited by 6 | PDF Full-text (689 KB) | HTML Full-text | XML Full-text
Abstract
Effective utilization of scarce water resources has presented a significant challenge to respond to the needs created by rapid economic growth in China. In this study, the efficiency of the joint operation of the Three Gorges and Gezhouba cascade hydropower plants in terms
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Effective utilization of scarce water resources has presented a significant challenge to respond to the needs created by rapid economic growth in China. In this study, the efficiency of the joint operation of the Three Gorges and Gezhouba cascade hydropower plants in terms of power generation was evaluated on the basis of a precise simulation-optimization technique. The joint operation conditions of the Three Gorges and Gezhouba hydropower plants between 2004 and 2010 were utilized in this research in order to investigate the major factors that could affect power output of the cascade complex. The results showed that the current power output of the Three Gorges and Gezhouba cascade complex had already reached around 90% of the maximum theoretical value. Compared to other influencing factors evaluated in this study, the accuracy of hydrological forecasts and flood control levels can have significant impact on the power generating efficiency, whereas the navigation has a minor influence. This research provides a solid quantitative-based methodology to assess the operation efficiency of cascade hydropower plants, and more importantly, proposes potential methods that could improve the operation efficiency of cascade hydropower plants. Full article
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Open AccessArticle Nonlinear Power-Level Control of the MHTGR Only with the Feedback Loop of Helium Temperature
Energies 2013, 6(2), 1142-1164; https://doi.org/10.3390/en6021142
Received: 6 November 2012 / Revised: 25 January 2013 / Accepted: 25 January 2013 / Published: 22 February 2013
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Abstract
Power-level control is a crucial technique for the safe, stable and efficient operation of modular high temperature gas-cooled nuclear reactors (MHTGRs), which have strong inherent safety features and high outlet temperatures. The current power-level controllers of the MHTGRs need measurements of both the
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Power-level control is a crucial technique for the safe, stable and efficient operation of modular high temperature gas-cooled nuclear reactors (MHTGRs), which have strong inherent safety features and high outlet temperatures. The current power-level controllers of the MHTGRs need measurements of both the nuclear power and the helium temperature, which cannot provide satisfactory control performance and can even induce large oscillations when the neutron sensors are in error. In order to improve the fault tolerance of the control system, it is important to develop a power-level control strategy that only requires the helium temperature. The basis for developing this kind of control law is to give a state-observer of the MHTGR a relationship that only needs the measurement of helium temperature. With this in mind, a novel nonlinear state observer which only needs the measurement of helium temperature is proposed. This observer is globally convergent if there is no disturbance, and has the L2 disturbance attenuation performance if the disturbance is nonzero. The separation principle of this observer is also proven, which denotes that this observer can recover the performance of both globally asymptotic stabilizers and L2 disturbance attenuators. Then, a new dynamic output feedback power-level control strategy is established, which is composed of this observer and the well-built static state-feedback power-level control based upon iterative dissipation assignment (IDA-PLC). Finally, numerical simulation results show the high performance and feasibility of this newly-built dynamic output feedback power-level controller. Full article
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Open AccessArticle A Materials Life Cycle Assessment of a Net-Zero Energy Building
Energies 2013, 6(2), 1125-1141; https://doi.org/10.3390/en6021125
Received: 15 October 2012 / Revised: 15 January 2013 / Accepted: 6 February 2013 / Published: 21 February 2013
Cited by 34 | PDF Full-text (529 KB) | HTML Full-text | XML Full-text
Abstract
This study analyzed the environmental impacts of the materials phase of a net-zero energy building. The Center for Sustainable Landscapes (CSL) is a three-story, 24,350 square foot educational, research, and administrative office in Pittsburgh, PA, USA. This net-zero energy building is designed to
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This study analyzed the environmental impacts of the materials phase of a net-zero energy building. The Center for Sustainable Landscapes (CSL) is a three-story, 24,350 square foot educational, research, and administrative office in Pittsburgh, PA, USA. This net-zero energy building is designed to meet Living Building Challenge criteria. The largest environmental impacts from the production of building materials is from concrete, structural steel, photovoltaic (PV) panels, inverters, and gravel. Comparing the LCA results of the CSL to standard commercial structures reveals a 10% larger global warming potential and a nearly equal embodied energy per square feet, largely due to the CSL’s PV system. As a net-zero energy building, the environmental impacts associated with the use phase are expected to be very low relative to standard structures. Future studies will incorporate the construction and use phases of the CSL for a more comprehensive life cycle perspective. Full article
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Open AccessArticle Game Optimization Theory and Application in Distribution System Expansion Planning, Including Distributed Generation
Energies 2013, 6(2), 1101-1124; https://doi.org/10.3390/en6021101
Received: 15 November 2012 / Revised: 12 January 2013 / Accepted: 29 January 2013 / Published: 21 February 2013
Cited by 16 | PDF Full-text (552 KB) | HTML Full-text | XML Full-text | Correction | Supplementary Files
Abstract
Based on Game Theory and Multi-objective optimization problems (MOP), Game Optimization Theory (GOT) is discussed in this paper. Optimization Stability Analysis (OSA), Distance Entropy Multi-Objective Particle Swarm Optimization (DEMPSO) and Fuzzy Multi-weights Decision-making Method (FMW) are proposed as well. Game Optimization Theory, which
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Based on Game Theory and Multi-objective optimization problems (MOP), Game Optimization Theory (GOT) is discussed in this paper. Optimization Stability Analysis (OSA), Distance Entropy Multi-Objective Particle Swarm Optimization (DEMPSO) and Fuzzy Multi-weights Decision-making Method (FMW) are proposed as well. Game Optimization Theory, which is a comprehensive system, could not only handle multi-objective optimization problems effectively, but also could offset the disadvantages of traditional optimization theories, such as lack of framework and the insufficient consideration of relevant elements. In this paper GOT is used for the first time in solving the distribution systems planning (DSP) issue by implementing distributed generation. The proposed model integrates costs, losses, and voltage index to achieve optimal size and site of distributed generation. The model allows minimizing total system costs, system power losses and maximizing voltage improvement. A detailed DSP example is used for verifying the effectiveness and reasonableness of GOT in this context. Full article
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Open AccessArticle A Photovoltaic Power System Using a High Step-up Converter for DC Load Applications
Energies 2013, 6(2), 1068-1100; https://doi.org/10.3390/en6021068
Received: 26 December 2012 / Revised: 7 February 2013 / Accepted: 8 February 2013 / Published: 21 February 2013
Cited by 24 | PDF Full-text (1880 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a power system using a high step-up converter for dc load applications. The high step-up converter adopts a boost converter with interleaved mode and a coupled inductor to raise its powering ability and increase its step-up voltage ratio, respectively. In
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This paper presents a power system using a high step-up converter for dc load applications. The high step-up converter adopts a boost converter with interleaved mode and a coupled inductor to raise its powering ability and increase its step-up voltage ratio, respectively. In order to increase conversion efficiency, an active clamp circuit is introduced into the proposed one to provide soft-switching features to reduce switching losses. Moreover, switches in the converter and active clamp circuit are integrated with a synchronous switching technique to reduce circuit complexity and component counts, resulting in a lower cost and smaller volume. A perturb and observe method is adopted to extract the maximum power from photovoltaic (PV) arrays. Furthermore, a microchip associated with PWM IC is used to implement maximum power point tracking operation, voltage regulation and power management. Finally, a prototype PV power system with 400 V/6 A has been implemented for verifying the feasibility of the proposed PV power system. It is shown to be suitable for PV energy conversion applications when the duty ratios of switches in the dc/dc converter are less than 0.5. Full article
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Open AccessArticle Exergy and Exergoeconomic Model of a Ground-Based CAES Plant for Peak-Load Energy Production
Energies 2013, 6(2), 1050-1067; https://doi.org/10.3390/en6021050
Received: 7 November 2012 / Revised: 11 December 2012 / Accepted: 22 January 2013 / Published: 19 February 2013
Cited by 20 | PDF Full-text (930 KB) | HTML Full-text | XML Full-text
Abstract
Compressed Air Energy Storage is recognized as a promising technology for applying energy storage to grids which are more and more challenged by the increasing contribution of renewable such as solar or wind energy. The paper proposes a medium-size ground-based CAES system, based
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Compressed Air Energy Storage is recognized as a promising technology for applying energy storage to grids which are more and more challenged by the increasing contribution of renewable such as solar or wind energy. The paper proposes a medium-size ground-based CAES system, based on pressurized vessels and on a multiple-stage arrangement of compression and expansion machinery; the system includes recovery of heat from the intercoolers, and its storage as sensible heat in two separate (hot/cold) water reservoirs, and regenerative reheat of the expansions. The CAES plant parameters were adapted to the requirements of existing equipment (compressors, expanders and heat exchangers). A complete exergy analysis of the plant was performed. Most component cost data were procured from the market, asking specific quotations to the industrial providers. It is thus possible to calculate the final cost of the electricity unit (kWh) produced under peak-load mode, and to identify the relative contribution between the two relevant groups of capital and component inefficiencies costs. Full article
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Open AccessArticle Recycling of Waste Engine Oils Using a New Washing Agent
Energies 2013, 6(2), 1023-1049; https://doi.org/10.3390/en6021023
Received: 3 December 2012 / Revised: 21 January 2013 / Accepted: 6 February 2013 / Published: 19 February 2013
Cited by 23 | PDF Full-text (773 KB) | HTML Full-text | XML Full-text
Abstract
This paper addresses recycling of waste engine oils treated using acetic acid. A recycling process was developed which eventually led to comparable results with some of the conventional methods. This gives the recycled oil the potential to be reused in cars’ engines after
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This paper addresses recycling of waste engine oils treated using acetic acid. A recycling process was developed which eventually led to comparable results with some of the conventional methods. This gives the recycled oil the potential to be reused in cars’ engines after adding the required additives. The advantage of using the acetic acid is that it does not react or only reacts slightly with base oils. The recycling process takes place at room temperature. It has been shown that base oils and oils’ additives are slightly affected by the acetic acid. Upon adding 0.8 vol% of acetic acid to the used oil, two layers were separated, a transparent dark red colored oil and a black dark sludge at the bottom of the container. The base oils resulting from other recycling methods were compared to the results of this paper. The comparison showed that the recycled oil produced by acetic acid treatment is comparable to those recycled by the other conventional methods. Full article
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Open AccessArticle Hydrate Formation/Dissociation in (Natural Gas + Water + Diesel Oil) Emulsion Systems
Energies 2013, 6(2), 1009-1022; https://doi.org/10.3390/en6021009
Received: 11 December 2012 / Revised: 19 January 2013 / Accepted: 1 February 2013 / Published: 18 February 2013
Cited by 8 | PDF Full-text (214 KB) | HTML Full-text | XML Full-text
Abstract
Hydrate formation/dissociation of natural gas in (diesel oil + water) emulsion systems containing 3 wt% anti-agglomerant were performed for five water cuts: 5, 10, 15, 20, and 25 vol%. The natural gas solubilities in the emulsion systems were also examined. The experimental results
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Hydrate formation/dissociation of natural gas in (diesel oil + water) emulsion systems containing 3 wt% anti-agglomerant were performed for five water cuts: 5, 10, 15, 20, and 25 vol%. The natural gas solubilities in the emulsion systems were also examined. The experimental results showed that the solubility of natural gas in emulsion systems increases almost linearly with the increase of pressure, and decreases with the increase of water cut. There exists an initial slow hydrate formation stage for systems with lower water cut, while rapid hydrate formation takes place and the process of the gas-liquid dissolution equilibrium at higher water cut does not appear in the pressure curve. The gas consumption amount due to hydrate formation at high water cut is significantly higher than that at low water cut. Fractional distillation for natural gas components also exists during the hydrate formation process. The experiments on hydrate dissociation showed that the dissociation rate and the amount of dissociated gas increase with the increase of water cut. The variations of temperature in the process of natural gas hydrate formation and dissociation in emulsion systems were also examined. Full article
(This article belongs to the Special Issue Natural Gas Hydrate 2013)
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Open AccessReview A Generic Framework for the Evaluation of the Benefits Expected from the Smart Grid
Energies 2013, 6(2), 988-1008; https://doi.org/10.3390/en6020988
Received: 23 November 2012 / Revised: 5 January 2013 / Accepted: 25 January 2013 / Published: 13 February 2013
Cited by 10 | PDF Full-text (348 KB) | HTML Full-text | XML Full-text
Abstract
The Smart Grid has the potential to bring significant value to the various stakeholders of the electricity market. A methodology for the evaluation of the smart grid benefits is required to facilitate the decision making by quantifying the benefits expected from a smart
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The Smart Grid has the potential to bring significant value to the various stakeholders of the electricity market. A methodology for the evaluation of the smart grid benefits is required to facilitate the decision making by quantifying the benefits expected from a smart grid project. The present paper proposes a generic framework to assess these expected benefits taking into account the regulatory, business and technical challenges focusing particularly on Distributed Systems Operators (DSOs) and end users. An indicative study case is presented where the proposed cost-benefit approach assesses the expected value of DSOs from the Smart Grid and determines whether and under what conditions such an investment should be initiated. Full article
(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)
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Open AccessArticle Evaluating the Economic Performance of High-Technology Industry and Energy Efficiency: A Case Study of Science Parks in Taiwan
Energies 2013, 6(2), 973-987; https://doi.org/10.3390/en6020973
Received: 23 December 2012 / Revised: 20 January 2013 / Accepted: 31 January 2013 / Published: 13 February 2013
Cited by 9 | PDF Full-text (644 KB) | HTML Full-text | XML Full-text
Abstract
High-technology industries provide opportunities for economic growth, but also raise concerns because of their energy-demanding nature. This paper provides an integrated evaluation of both economic benefits and energy efficiency of high-technology industries based on the real data from one of the globally recognized
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High-technology industries provide opportunities for economic growth, but also raise concerns because of their energy-demanding nature. This paper provides an integrated evaluation of both economic benefits and energy efficiency of high-technology industries based on the real data from one of the globally recognized high-technology industrial clusters, the national science parks in Taiwan. A nation-wide industrial Input-Output Analysis is conducted to demonstrate the positive effects of science parks on national economic developments and industrial upgrades. The concept of energy intensity and an energy-efficient economy index are applied to an integrated assessment of the relationship between economic growth and energy consumption. The proposed case study suggests that economic and energy efficiency objectives can be simultaneously achieved by the development of high-technology industries, while three energy policy implications are considered. First, a nation-wide macro viewpoint is needed and high-technology industries should be considered as parts of the national/regional economies by governmental agencies. Second, a proper industrial clustering mechanism and the shared environmental facilities supported by the government, such as planned land and road usage, electricity and water supply, telecommunications system, sewerage system and wastewater treatments, can improve energy efficiency of high-technology industries. Third, the governmental policies on the taxing and management system in science parks would also direct energy-efficient economy of high-technology industries. Full article
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Open AccessArticle Retrofitting Conventional Electric Domestic Hot Water Heaters to Solar Water Heating Systems in Single-Family Houses—Model Validation and Optimization
Energies 2013, 6(2), 953-972; https://doi.org/10.3390/en6020953
Received: 14 December 2012 / Revised: 15 January 2013 / Accepted: 22 January 2013 / Published: 12 February 2013
Cited by 5 | PDF Full-text (712 KB) | HTML Full-text | XML Full-text
Abstract
System cost reductions and development of standardised plug-and-function systems are some of the most important goals for solar heating technology development. Retrofitting hot water boilers in single-family houses when installing solar collectors has the potential to significantly reduce both material and installation costs.
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System cost reductions and development of standardised plug-and-function systems are some of the most important goals for solar heating technology development. Retrofitting hot water boilers in single-family houses when installing solar collectors has the potential to significantly reduce both material and installation costs. In this study, the TRNSYS simulation models of the retrofitting solar thermal system were validated against measurements. Results show that the validated models are in good agreement with measurements. On an annual basis a deviation of 2.5% out of 1099 kWh was obtained between the auxiliary energy from results and from the simulation model for a complete system. Using the validated model a system optimization was carried out with respect to control strategies for auxiliary heating, heat losses and volume of auxiliary storage. A sensitivity analysis was carried out regarding different volumes of retrofitted hot water boiler, DHW profiles and climates. It was estimated that, with adequate improvements, extended annual solar fractions of 60%, 78% and 81% can be achieved for Lund (Sweden), Lisbon (Portugal) and Lusaka (Zambia), respectively. The correspondent collector area was 6, 4 and 3 m2, respectively. The studied retrofitted system achieves a comparable performance with conventional solar thermal systems with the potential to reduce the investment cost. Full article
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Open AccessArticle Modeling of the Partial Discharge Process in a Liquid Dielectric: Effect of Applied Voltage, Gap Distance, and Electrode Type
Energies 2013, 6(2), 934-952; https://doi.org/10.3390/en6020934
Received: 29 November 2012 / Revised: 1 February 2013 / Accepted: 4 February 2013 / Published: 8 February 2013
Cited by 9 | PDF Full-text (1191 KB) | HTML Full-text | XML Full-text
Abstract
The partial discharge (PD) process in liquid dielectrics is influenced by several factors. Although the PD current contains the information representing the discharge process during the PD event, it is difficult to determine the detailed dynamics of what is happening in the bulk
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The partial discharge (PD) process in liquid dielectrics is influenced by several factors. Although the PD current contains the information representing the discharge process during the PD event, it is difficult to determine the detailed dynamics of what is happening in the bulk of the liquid. In this paper, a microscopic model describing the dynamics of the charge carriers is implemented. The model consists of drift-diffusion equations of electrons, positive and negative ions coupled with Poisson’s equation. The stochastic feature of PD events is included in the equation. First the model is validated through comparison between the calculated PD current and experimental data. Then experiments are conducted to study the effects of the amplitude of the applied voltage, gap distance and electrode type on the PD process. The PD currents under each condition are recorded. Simulations based on the model have been conducted to analyze the dynamics of the PD events under each condition, and thus explain the mechanism of how these factors influence the PD events. The space charge generated in the PD process is revealed as the main reason affecting the microscopic process of the PD events. Full article
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Open AccessArticle System Identification and Integration Design of an Air/Electric Motor
Energies 2013, 6(2), 921-933; https://doi.org/10.3390/en6020921
Received: 5 December 2012 / Revised: 4 February 2013 / Accepted: 5 February 2013 / Published: 8 February 2013
Cited by 3 | PDF Full-text (413 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an integration design and implementation of an air motor and a DC servo motor which utilizes a magnetic powder brake to integrate these two motors together. The dynamic model of the air/electric hybrid system will be derived and eventually leads
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This paper presents an integration design and implementation of an air motor and a DC servo motor which utilizes a magnetic powder brake to integrate these two motors together. The dynamic model of the air/electric hybrid system will be derived and eventually leads to successful ECE-40 driving cycle tests with a FPGA-based speed controller. The testing results obtained by using the proposed experimental platform indicate that the total air consumption is about 256 L under air motor mode and the electric charge consumption is about 530 coulombs under DC servo motor mode. In a hybrid mode, the current reduction of the battery is about 18.5%, and then the service life of the battery can be improved. Furthermore, a prototype is built with a proportional-integral (PI) speed controller based on a field-programmable gate array (FPGA) in order to facilitate the entire analysis of the velocity switch experiment. Through the modular methodology of FPGA, the hybrid power platform can successfully operate under ECE-40 driving cycle with the PI speed controller. The experimental data shows that the chattering ranges of the air motor within ±1 km/h and ±0.2 km/h under DC servo motor drive. Therefore, the PI speed controller based on FPGA is successfully actualized. Full article
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Open AccessArticle Modeling Supermarket Refrigeration Systems for Demand-Side Management
Energies 2013, 6(2), 900-920; https://doi.org/10.3390/en6020900
Received: 29 September 2012 / Revised: 19 December 2012 / Accepted: 21 January 2013 / Published: 8 February 2013
Cited by 24 | PDF Full-text (647 KB) | HTML Full-text | XML Full-text
Abstract
Modeling of supermarket refrigeration systems for supervisory control in the smart grid is presented in this paper. A modular modeling approach is proposed in which each module is modeled and identified separately. The focus of the work is on estimating the power consumption
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Modeling of supermarket refrigeration systems for supervisory control in the smart grid is presented in this paper. A modular modeling approach is proposed in which each module is modeled and identified separately. The focus of the work is on estimating the power consumption of the system while estimating the cold reservoir temperatures as well. The models developed for each module as well as for the overall integrated system are validated by real data collected from a supermarket in Denmark. The results show that the model is able to estimate the actual electrical power consumption with a high fidelity. Moreover a simulation benchmark is introduced based on the produced model for demand-side management in smart grid. Finally, a potential application of the proposed benchmark in direct control of the power/energy consumption is presented by a simple simulation example. Full article
(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)
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