The integration of plug-in electric vehicles (PEVs) in residential distribution networks demands a significant amount of electrical load where random and uncoordinated charging affects the quality and performance of the distribution network. Random and uncoordinated charging may increase the peak demand and can increase stress on critical network assets such as line, transformer, and switching devices. Moreover, the charging of PEVs in a low network reduces the voltage of the system below the lower limit. On the other hand, using PEVs as storage in the V2G mode can improve the network condition. Therefore, it is critical to properly manage the charging and discharging operation of PEVs. This paper proposes a multi-objective-based charging and discharging coordination of PEVs with the operation of the capacitor and on-load tap changer (OLTC). With the proposed strategy, the distribution network is operated safely, and charging is ensured for all PEVs connected to the network. The main c... [more]

To minimize the impact of snowfall and ice formation on safety of transportation, salt is sprinkled on the asphalt every winter. However, the use of salt has economical as well as ecological disadvantages. To resolve these problems, road heating systems are used in the northern regions of Europe and America. Despite their widespread usage, considerable potential of the operational optimization is evident. The current systems are controlled under predefined weather conditions such as start of operation at 5 °C air temperature, even when snowfall is absent. Consequently, loss of energy input to heat the system is caused. To avoid unnecessary financial and energetic expense, this study presents CFD-based performance investigation as a basis for a novel predictive controller to increase the operational efficiency of hydronic road heating systems (HRS). The simulation model was developed based on a real operational HRS located in Ingolstadt and composed of bridges and ramps for a total surf... [more]

The present paper proposes an integrated method for modelling and designing Energy Storage Systems (ESSs) based on Sodium Metal Halide Batteries (SMHBs). The implementation of the proposed methodology for designing an SMHB-ESS used for supporting telecommunication DC microgrids is presented. The motivation concerning this specific case study is the role assumed by battery technology in improving the reliability and robustness of telecommunication DC microgrids. In this context, the SMHBs, due to their operative temperature, dynamic power response and robustness against cell breakdown, represent one of the most suitable technologies, mainly when challenging environmental conditions occur. The motivation for implementing an integrated design approach is the non-linear behaviour of SMHBs, which requires a high accuracy in battery modelling and in managing DC-DC interfacing for full SMHB capacity exploitation. To highlight the advantages of this novel approach, a comparison between the SMH... [more]

With the increasing integration of HVDC tie-lines, the regional power systems in both the energy-exporting area and the energy-importing area have been gradually evolving into “strong DC, weak AC” systems. In this paper, a multi-period transmission expansion planning optimization model is proposed for an energy-exporting power grid with hybrid AC/DC interface. While the existing literature has not considered the dynamic security problem in TEP, this paper adopts the conventional total transfer capacity (TTC) index to evaluate the security limit of hybrid AC/DC interface under different transmission expansion schemes. Multiple objectives are considered to reduce the investment cost while promoting the consumption of renewables by enhancing the total transfer capacity of hybrid AC/DC interface. The non-dominated sorting genetic algorithm-II (NSGA-II) is used to compute the optimal solution for the proposed multi-period multi-objective transmission expansion planning problem. A case study... [more]

The operating parameters of the active direct methanol fuel cell (DMFC) are essential factors that affect cell performance. However, it is challenging to maintain the optimal maximum output power density due to the system’s complexity, the operating conditions variation, and the correlations between those parameters. This paper proposes an adaptive joint optimization method for fuel cell operating parameters. The methods include the adaptive numerical simulation of the operation parameters and the optimization for fuel cell performance. Based on orthogonal tests, a BP neural network is used to build a performance evaluation model that can quantify the influence of the operating parameters on fuel cell performance. The optimal combination of operating parameters for the fuel cell is obtained by a whale optimization algorithm (WOA) through the evaluation model. The experimental results show that the evaluation model could respond accurately and adaptively to the cell operating conditions... [more]

In this paper, a method for rationally allocating energy storage capacity in a high-permeability distribution network is proposed. By constructing a bi-level programming model, the optimal capacity of energy storage connected to the distribution network is allocated by considering the operating cost, load fluctuation, and battery charging and discharging strategy. By constructing four scenarios with energy storage in the distribution network with a photovoltaic permeability of 29%, it was found that the bi-level decision-making model proposed in this paper saves 2346.66 yuan and 2055.05 yuan, respectively, in daily operation cost compared to the scenario without energy storage and the scenario with single-layer energy storage. After accessing IEEE-33 nodes for simulation verification, it was found that the bi-level decision-making model proposed in this paper has a good inhibition effect on voltage fluctuation and load fluctuation after energy storage configuration. In addition, this p... [more]

Reservoir characteristics and the occurrence mechanism of shale gas outside of the Sichuan Basin are the research hotspots of normally pressured shales in China. Taking shales on the Anchang syncline from the periphery of the Sichuan Basin as an example, X-ray diffraction, organic geochemistry, and rock physical experiments were carried out to analyze the reservoir characteristics and their main geological controls on the normally pressured shales. The mineralogical results show that the studied shales from the Anchang syncline are mainly siliceous shales with a high quartz content (average of 57%). The quartz content of these normally pressured shales is of biological origin, as shown by the positive correlation between the quartz and organic carbon (TOC) contents. The average porosity of the studied shales is about 2.9%, which is lower than shales inside the Sichuan Basin. Organic matter pores are likely the primary storage space of the normally pressured shale gas, as shown by the p... [more]

Since the structure of horizontal gas wells is more intricate than that of vertical wells, there is a lack of consistency in the form of liquid-carrying in different portions. Applying the commonly utilized liquid-carrying hypothesis of vertical gas wells into horizontal gas wells is therefore challenging. The maximum liquid volume that the gas flow could raise, the gas flow rate, and the maximum amount of energy that could be produced from a specific amount of gas flow should all be considered when determining the liquid volume that the gas flow could lift. This study is the first to integrate theoretical analysis with laboratory testing to analyze the gas−liquid flow law of drainage stability at varied tubing depths. The impact of gas drainage stability is then verified through the laboratory experiments. The novel model of various tubing depths, which is based on the energy of inflow and outflow from the horizontal well, is cleverly built. According to the study, the fluctuation is... [more]

An increase in reactive power consumption results in an increase in electricity costs. This negative phenomenon can be prevented by using reactive power compensation methods. One of them is the installation of capacitors. These capacitors are exposed to external conditions, such as temperature and humidity. As a consequence, the aging process occurs. Another negative phenomenon is the corrosion that occurs inside the capacitor as a result of moisture absorption. As a result of this phenomenon, the capacitor can be damaged. One of the symptoms of the ongoing corrosion of the inside of the capacitor is an increase in temperature. Capacitors designed for reactive power compensation operate at mains voltage. They are often placed in a switchgear. For this reason, the use of contact methods of temperature measurement is difficult and dangerous. An alternative is thermographic measurement. Determining the internal temperature of the capacitor by thermographic measurement of the temperature o... [more]

The growth of microgrids to fulfil electricity demand could lead to arguments or conflicts between the private microgrid system owners and the existing national distribution authority, especially in overlapping sales areas. The core issue identified in this paper is a distribution system management model based on the cooperative concept of unifying the multi-owned networks as a single system to ensure the natural monopoly function. This model can avoid complex wheeling charges across multi-owned grids within overlapping sales areas, in which all network users pay at the expense of the merged system charge. This paper proposes the model and shows numerical examples using a suitable distribution network pricing model to recover existing costs and plan for future system expansion. The proposed model and charging algorithm were tested on a modified IEEE 13 bus to examine their impacts. The result demonstrates that the model resolves the issues with the overlapping sales area and creates a... [more]

The accumulation of energy from non-programmable renewable sources is a crucial aspect for the energy transition. Using surplus electricity from renewable energy sources, power-to-gas plants allow to produce a substitute natural gas (SNG) that can be injected in the existing infrastructure for large-scale and long-term energy storage, contributing to gas grid decarbonisation. The plant layout, the method used for carbon dioxide capture and the possible cogeneration of electricity can increase the efficiency and convenience of SNG synthesis plants. In this work, a system for the simultaneous production of SNG and electricity starting from biomass and fluctuating electricity from renewables is proposed, using a plant based on the Allam thermodynamic cycle as the power unit. The Allam power cycle uses supercritical CO2 as evolving fluid and is based on the oxycombustion of gaseous fuels, thus greatly simplifying CO2 capture. In the proposed system, oxycombustion is performed using biomass... [more]

Optimization-based design tools for energy systems often require a large set of parameter assumptions, e.g., about technology efficiencies and costs or the temporal availability of variable renewable energies. Understanding the influence of all these parameters on the computed energy system design via direct sensitivity analysis is not easy for human decision-makers, since they may become overloaded by the multitude of possible results. We thus propose transferring an approach from explaining complex neural networks, so-called locally interpretable model-agnostic explanations (LIME), to this related problem. Specifically, we use variations of a small number of interpretable, high-level parameter features and sparse linear regression to obtain the most important local explanations for a selected design quantity. For a small bottom-up optimization model of a grid-connected building with photovoltaics, we derive intuitive explanations for the optimal battery capacity in terms of different... [more]

After deep mining, the discontinuous deformation characteristics of roadway roofs become more and more obvious, resulting in the emergence of separation fractures in the rock mass, which seriously affects the stability of the roof rock mass. By taking the air return roadway 21204 (ARR 21204) in Hulusu Coal Mine as the engineering background, this article reveals the discontinuous deformation characteristics of deep buried roadway roofs through field research, numerical simulation, theoretical analysis and engineering practice. After roadway excavation, the rock masses in different shallow roof horizons show different degrees of stress unloading, resulting in the occurrence of discontinuous deformation phenomena in rock masses. With the rise of the roof rock horizon, the degree of discontinuous deformation fades away until a continuous deformation zone with small deformation and stable rock strata appears. In addition, with the increase in the roadway buried depth, the extent of the dis... [more]

The large and growing volume of tire waste and sewage sludge requires disposal, for which thermochemical processes such as gasification can be used. Co-gasification of these two waste products allows the tire char to be used as a charge stabilizer and the sewage sludge to improve reactivity and efficiency. The purpose of this study was to evaluate the effect of the composition of a waste tire char and sewage sludge fuel blend on the gasification process, using steam as the gasification agent. Tests were carried out for tire char, municipal sewage sludge, and blends of the two in ratios of 90:10 and 67:33. An analysis of the materials used was carried out (ultimate and proximate analysis as well as ash composition), and isothermal measurements of steam gasification were taken using the thermal volumetric method for temperatures of 800, 850, and 900 °C at an elevated pressure of 1 MPa. On the basis of the results, the formation curves of the main gasification products (H2, CO, CO2, and C... [more]

The present article focuses on the efficient deployment of dual locomotives in regional rail freight transport considering the quantification of traction energy and energy savings. In the first part of the article, a categorization of dual locomotives, according to their power output in electric and alternative traction (and ratio of both power outputs) is proposed. The potential of deployment of chosen dual locomotives in Central European conditions (a sub-network of Czech railway network around mainlines electrified with AC) is verified by calculation of traction energy consumption of the model train (with two examples of dual locomotives). In addition to non-stop running through the entire line, traction energy consumption of stop (and following acceleration) in each intermediate station is calculated, for a particular direction. Then, appropriate freight train paths for passing passenger trains and saving of traction energy are proposed. The results are supplemented by sensitivity... [more]

With the gradual depletion of fossil energy sources and the improvement in environmental protection attention, efficient use of energy and reduction in carbon emissions have become urgent issues. The integrated electricity and heating energy system (IEHS) is a significant solution to reduce the proportion of fossil fuel and carbon emissions. In this paper, a stochastic optimization model of the IEHS considering the uncertainty of wind power (WP) output and carbon capture power plants (CCPs) is proposed. The WP output in the IEHS is represented by stochastic scenarios, and the scenarios are reduced by fast scenario reduction to obtain typical scenarios. Then, the conventional thermal power plants are modified with CCPs, and the CCPs are equipped with flue gas bypass systems and solution storage to form the integrated and flexible operation mode of CCPs. Furthermore, based on the different load demand responses (DRs) in the IEHS, the optimization model of the IEHS with a CCP is construct... [more]

The paper presents the methodology that should be used to optimize hybrid power system configurations, i.e., the chosen microgrid scenario. The methodology was developed with the aim of evaluating the different production capacities of a system and comparing them with alternative connections to the main grid. It has a step-by-step structure and includes part of the steps performed by simulations in a computer program. It provides us with not only a basic but also a representative idea of an actual microgrid configuration, which is further used as support in the system’s design. An algorithm has been developed to check the energy flows and correct the selling price. The program HOMER Pro is used as the program support in performing the hybrid optimization simulation. In the analysis, it was found that the maximum share of generation from renewable energy sources in relation to the power grid is 143%, while the share of renewable energy sources in the generated energy is 65.3%. Greenhous... [more]

Research on batteries’ State of Charge (SOC) estimation for equivalent circuit models based on the Kalman Filter (KF) framework and machine learning algorithms remains relatively limited. Most studies are focused on a few machine learning algorithms and do not present comprehensive analysis and comparison. Furthermore, most of them focus on obtaining the state space parameters of the Kalman filter frame algorithm models using machine learning algorithms and then substituting the state space parameters into the Kalman filter frame algorithm to estimate the SOC. Such algorithms are highly coupled, and present high complexity and low practicability. This study aims to integrate machine learning with the Kalman filter frame algorithm, and to estimate the final SOC by using different combinations of the input, output, and intermediate variable values of five Kalman filter frame algorithms as the input of the machine learning algorithms of six main streams. These are: linear regression, supp... [more]

Electroosmotic flow (EOF) commonly involves inhomogeneous fluids in practical applications. EOF hysteresis, which is defined as direction-dependent flow behavior, has been extensively investigated for dissimilar solution pair systems. Hitherto, there is no investigation being conducted to examine the effect of microchannel diameter on the hysteresis phenomenon. In this investigation, current monitoring experiments and finite element numerical simulations were performed to examine the intensification of the hysteretic behavior with reduction in the microchannel diameter. Three solution pairs were selected for the study, namely KCl−NaCl (dissimilar ionic species with similar concentration), NaCl and KCl (similar ionic species but different concentrations) solution pairs, with microchannels of 5 μm and 100 μm internal diameters. EOF hysteresis augmentation for reduced channel diameter (i.e., 5 μm microchannel) is due to the coupling effect of the resultant wider/tighter interfacial width... [more]

(1) Background: The economic impact of supply and demand in the energy industry can be seen throughout raw material production, processing and distribution. The purpose of this study is to provide academic information to prepare for crisis management through prediction using indices. (2) Method: In order to predict a crisis of the energy industry, the Crisis Index presented by the Korea Institute of Science and Technology Information was utilized instead of the economic indicators that have hitherto been widely used. Specifically, we propose a new forecasting model based on the concept of economic momentum theory used in financial research and the proper weighting of the earning downside risk theory. Then, statistical empirical analysis was performed to verify the new prediction model. (3) Results: As the result of the empirical analysis, the risk index prediction model proposed in this study showed statistically significant results in predicting the future risk index. (4) Conclusions:... [more]

The European Green Deal declares climate neutrality as a goal for the year 2050. It establishes an EU binding target to reduce greenhouse gas emissions by 55 percent by 2030 compared to 1990. The market, through the EU Emissions Trading Scheme, will determine how EU member states contribute to this target. The Effort Sharing Regulation defines binding national targets to reduce the remaining GHG emissions not covered by the EU ETS. In this paper, an energy optimization model is applied to analyze the capability of Czechia to meet the climate change targets by 2030 and 2050. We define a baseline scenario derived from the National Energy and Climate Plan and three policy scenarios to assess impacts of the extension of the EU ETS to buildings and transport (EU ETS 2) and the coal phase-out on the Czech energy system. One of the policy scenarios aims at approaching climate neutrality in 2050. In addition, another scenario does not assess the impacts of the EU ETS 2 and coal phase-out but s... [more]

Condition diagnosis of power transformers using acoustic signals is a nonstop, contactless method of equipment maintenance that can diagnose the transformer’s type of abnormal condition. To heighten the accuracy and efficiency of the abnormal method of diagnosing abnormalities by sound, a method for abnormal diagnosis of power transformers based on the Attention-CNN-LSTM hybrid model is proposed. This collects the sound signals emitted by the real power transformer in the normal state, overload, and the discharge condition. It preprocesses the sound signals to obtain the MFCC characteristics of the sound signals. It is then grouped into a set of sound feature vectors by the first- and second-order differences, and enters the Attention-CNN-LSTM hybrid model for training. The training results show that the Attention-CNN-LSTM hybrid model can be used for the status sound detection of power transformers, and the recognition of the three states can achieve an accuracy rate of more than 99%.

This paper presents economic value estimation of improved biogas utilization systems of public wastewater treatment plants in Republic of Korea. Since a large amount of biogas produced at digestion facilities is being wasted as a by-product, the biogas energy utilization system needs to be enhanced. In this paper, three operating options able to utilize the produced biogas are proposed, and then their monetary benefits are estimated by means of net present value calculation. Real operational data from the public wastewater treatment plant located in Sejong city, Republic of Korea, is used to reflect a variation of the rated daily gas production and its concentration according to the weather and seasons, resulting in calculating more reliable results. Additionally, to minimize the estimation errors due to uncertainties of the gas concentration and the gas selling price, a Monte Carlo simulation considering the variation of critical input data is carried out. As a result, the proposed ap... [more]

The underground mining industry is at the forefront when it comes to unsafe conditions at workplaces. As mining depths continue to increase and the mining fronts move away from the ventilation shafts, gas hazards are increasing. In this article, the authors developed a statistical polynomial model for nitrogen oxide (NOx) emission prediction of the LHD vehicle with a diesel engine. The best-achieved prediction accuracy by the 4th order polynomial model for 11 and 10 input variables is about 8% and 13%, respectively. It is comparable with the sensors’ accuracy of 10% at a stable regime of loading and 20% in the transient periods of operation. The obtained results allow planning of ventilation system capacity and power demand for the large fleet of vehicles in the deep underground mines.

Energy consumption reduction and thermal quality improvement constitute two major aspects of building design and/or retrofitting. Following the current energy transition trends, a state-of-the-art solution is the implementation of Adaptive Dynamic Building Envelopes (ADBEs), which are capable of integrating different technologies and components. The purpose of this investigation is to assess the annual performance improvement of two actual building spaces retrofitted with ADBEs, consisting of Building Integrated Photovoltaics (BIPVs), additional thermal insulation, mechanical ventilation system with heat recovery, and solar air heaters (SAHs). Both buildings are pilot sites for the EU Horizon 2020 Plug-n-Harvest project and are located in two rather different climate zones, i.e., Cardiff, Wales, and Grevena, Greece. Moreover, through detailed dynamic modeling with the use of Modelica language, this study attempts to accurately capture all interactions between buildings and all the afor... [more]