Smart grid integrates computer, communication, and sensing technologies into existing power grid networks to achieve significant informatization-related advantages. It will provide communication between neighbors, localized management, bidirectional power transfer, and effective demand response. Smart grids (SG) replace conventional grids by integrating various operational measures, including smart automation appliances, smart meters, and renewable energy sources. Regarding energy management and resolving energy issues, SG is one of the most cutting-edge and potentially game-changing innovations. Even still, its complexity suggests that decentralization may provide significant gains. Because of its increasing digitization and interconnectedness, it is also vulnerable to cyber threats. Blockchain, in this sense, is a potential SG paradigm solution that provides several great benefits. Even though blockchains have been widely discussed to decentralize and strengthen smart grid cybersecur... [more]

This article deals with the development of renewable energy sources and their role in the transformation of energy. The main purpose of this article is to analyze the role of local governments in Poland in accelerating energy transformation at the local level through the implementation of municipal investments. The potential activities of the municipalities in the area of local eco-energy were presented, with particular emphasis on their own investment projects. The involvement of municipalities in the implementation of their own projects in the area of energy transformation was assessed, and the sources of financing for such projects were determined. A diagnosis of barriers and limitations to the increase in the participation of communes in this area was also made. This research was carried out in the Podkarpackie and Lublin regions in southern Poland. The research results indicate that local government authorities are willing to accept contributing to eco-energy projects, but only wh... [more]

Biogas production is the most important and promising alternative for replacing fossil fuels in an environmentally friendly manner. Along with the many renewable energy sources available, biogas production occupies an irreplaceable position due to the undeniable availability of biomass and the need to manage agro-commercial waste. The article reviews the current state of technology used in the production of biogas for selected European examples in terms of methane fermentation efficiency and actual energy production. The novelty of the article is its description of innovative trends that have great potential to play an important role in this field in the near future. The development of the biogas industry in Europe is evident, although the dynamics vary from country to country. Different models are presented, which are based on the different types of feedstock used for biogas production and the proportion of substrates used in co-digesters. Of course, Germany is the undisputed pioneer... [more]

Second-order ripples occur in the voltage and current during any DC−AC power conversion. These conversions occur in the voltage source inverters (VSIs), current source inverters (CSIs), and various single-stage inverters (SSIs) topologies. The second-order ripples lead to oscillating source node currents and DC bus voltages when there is an interconnection between the AC and DC microgrids or when an AC load is connected to the DC bus of the microgrid. Second-order ripples have various detrimental effects on the sources and the battery storage. In the storage battery, they lead to the depletion of electrodes. They also lead to stress in the converter or inverter components. This may lead to the failure of a component and hence affect the reliability of the system. Furthermore, the second-order ripple currents (SRCs) lead to ripple torque in wind turbines and lead to mechanical stress. SRCs cause a rise in the temperature of photovoltaic panels. An increase in the temperature of PV panel... [more]

We investigated the operation of an axial-flow cyclone as the most promising dust-cleaning equipment based on energy consumption. Numerical solutions were obtained for the gas-solids suspension flow equations in axial flow cyclones with different separation chambers’ geometry using FlowVision software. The chamber’s geometrical features determined the nature of the gas-solids suspension flow, directly affecting the dusty gases’ purification degree. The circulating gas flows and the turbulent “trace” after the swirl generator were found to negatively influence the cyclone efficiency and the hydraulic resistance values. A high chamber height also negatively affected the gas purification since the bulk of dust particles were removed from the gas-solids flow at the initial section. The initial section’s length coincided with the gas-solids suspension’s jet flow zone due to the flow coming off the swirl vanes’ edges. Due to turbulent mixing, the particles’ secondary entrainment and return t... [more]

Due to micro landforms and climate, the 110 kV transmission lines crossing the mountain areas are exposed to severe icing conditions for both their high voltage (HV) conductors and shield wires during the winter. Ice accumulation on the shield wire causes excessive sag, which leads to a reduced clearance between earth and HV wires, and could eventually result in tripping of the line due to phase-to-ground flashover. Due to the lack of effective de-icing techniques for the shield wires, removing them completely from the existing overhead line (OHL) structure becomes a reasonable solution to prevent icing accidents. Nevertheless, the risk of exposure to lightning strikes increased significantly after the shield wires were removed. In order to cope with this, the anti-thunder and anti-icing composite insulator (AACI) is installed on the OHLs. In this article, the 110 kV transmission line without shield wire is considered. The shielding failure after installation of the AACIs is studied us... [more]

The doubly fed induction machine (DFIM)-based DC voltage generator is equipped with a stator-connected diode rectifier. The six-pulse diode rectifier as a nonlinear circuit introduces harmonics in the stator and rotor current and distorts the machine stator voltage, as well as the stator flux. This causes electromagnetic torque oscillations and instantaneous power components oscillations. The torque oscillations adversely impact the mechanical parts of the drive-train and oscillations of the p component of instantaneous power influence DC-bus voltage oscillations. The oscillations can be somewhat cancelled by control methods. However, cancellation of electromagnetic torque is not strictly coupled with cancellation of oscillations of the p component of instantaneous power. The paper presents an analysis of influence of the control methods aimed at a reduction of torque oscillations on the output voltage oscillations level in the stand-alone DFIM-based DC voltage generator. Field-oriente... [more]

Seismic, core, drilling, logging, and thin-section data are considered to analyze the reservoir diversity in the east, middle, and west fan of the Liushagang Formation in the steep-slope zone of the Weixinan Sag, Beibuwan Basin. Three factors primarily affect the reservoir differences for steep-slope systems: (1) Sedimentary factors mostly control reservoir scales and characteristics and the drainage system and microfacies. Massive high-quality reservoirs have shallow burial depths. Channel development and sediment supply favor the formation of these reservoirs. The sedimentary microfacies suggest fan delta plain distributary channels. (2) Lithofacies factors primarily control reservoir types and evolution. The diagenesis of high-quality reservoirs is weak, and a weak compaction−cementation diagenetic facies and medium compaction−dissolution diagenetic facies were developed. (3) Sandstone thickness factors primarily control the oil-bearing properties of reservoirs. The average porosity... [more]

The speech intelligibility properties of classrooms greatly influence the learning process of students. Proper acoustics can promote the inclusion of foreign students and children with learning or hearing impairments. While awareness of the topic is increasing, there is still no parameter that can describe all aspects of speech transmission inside a room. This complicates the design of classrooms and requires designers to have extensive knowledge of theory and experience. In the scientific and technical literature, there is a lack of predictive tools, easy to use by designers, which can guide the choices in the early design stages in order to move towards technical solutions able to ensure adequate levels of speech intelligibility. For this reason, in this paper, the most relevant speech intelligibility parameters found in the literature were collected and discussed. Among these, the Clarity index and Speech Transmission Index were singled out as the most effective ones, whose predicti... [more]

Full utilization of renewable energy resources is a difficult task due to the constantly changing demand-side load of the electrical grid. Demand-side management would solve this crucial problem. To enable demand-side management, knowledge about the composition of the grid load is required, as well as the ability to schedule individual loads. There are proposed Smart Plugs presented in the literature capable of such tasks. The problem, however, is that these methods lack the ability to detect if a previously unseen electrical load is connected. Misclassification of such loads presents a problem for load estimation and scheduling. Open-set recognition methods solve this problem by providing a way to detect samples not belonging to any class used during the training of the classifier. This paper evaluates the novel application of open-set recognition methods to the problem of load classification. Two approaches were examined, and both offer promising results. A Support Vector Machine bas... [more]

A paradigm shift in power systems is observed due to the massive integration of renewable energy sources (RESs) as distributed generators. Mainly, solar photovoltaic (PV) panels and wind generators are extensively integrated with the modern power system to facilitate green efforts in the electrical energy sector. However, integrating these RESs destabilizes the frequency of the modern power system. Hitherto, the frequency control has not drawn sufficient attention due to the reduced inertia and complex control of power electronic converters associated with renewable energy conversion systems. Thus, this article provides a critical summary on the frequency control of solar PV and wind-integrated systems. The frequency control issues with advanced techniques, including inertia emulation, de-loading, and grid-forming, are summarized. Moreover, several cutting-edge devices in frequency control are outlined. The advantages and disadvantages of different approaches to control the frequency o... [more]

Current-limiting reactors are widely used in industrial electrical grids to reduce the current amplitude in the equipment and stabilize the voltage on the busbar during short circuits. Their application is distinguished by high technical and economic efficiency. However, mechanical damage to the reactors has been observed within extensive industrial grids with many induction motors and internal synchronous generators. The article analyses a case study of the reactor damage in the true industrial grid during a short circuit. An analysis of the damaged reactor’s previous operation had shown that there was a weakening of the fastenings in the reactor design, caused by the repeated starting currents of the grid motors and generators. A study of grid transients during short circuits was carried out by Matlab/Simulink software. The simulation results showed that the reactor could be damaged by a critical peak current in an unfavourable combination of the grid configuration and the short circ... [more]

Utilization of unharnessed hydro-power necessitates designing fish-friendly hydraulic machinery. Towards this effort, the present work investigates various methods for tracking fish motion, ranging from particle tracking methods to accurate, but computationally expensive, body tracking methods, such as immersed boundaries and overset meshes. Moreover, a novel uncoupled 6-Degree of Freedom tracking technique is proposed, based on an approximated pressure field around the tracked body of interest, using steady-state flow field data, and including collision detection to walls. The proposed method shows promising results in terms of accuracy, being comparable to the more computationally expensive fully coupled methods at a tiny fraction of the execution time. The new method reveals location of fish−blade impact, as well as statistics of forces, pressure and flow shear that a passing fish is subjected to, both in the normal and reverse operation of the turbine. The low computational cost of... [more]

The time-varying, dynamic, nonlinear, and other characteristics of lithium-ion batteries, as well as the capacity regeneration phenomenon, leads to the low accuracy of the traditional deep learning models in predicting the remaining useful life of lithium-ion batteries. This paper established a sequence-to-sequence model for remaining useful life prediction by combining the variational modal decomposition with bi-directional long short-term memory and Bayesian hyperparametric optimization. First, variational modal decomposition is used for noise reduction processing to maximize the retention of the original information of capacity degradation. Second, the capacity declining trend after noise reduction is modeled and predicted by the combination of bi-directional long-short term memory and temporal attention mechanism. In addition, a Bayesian optimizer is used to adaptively adjust the hyperparameters while training the model. Finally, the model was validated on NASA and CALCE data sets,... [more]

This paper addresses the use of a geothermal heat-sink to remove the heat released in domestic-sized single and double-effect water−LiBr absorption chillers operating in hot climates. This study is the continuation of a previous work, which demonstrated the operational constraints of these absorption chillers working in hot Algerian climate-zones. After localizing the non-operation zones for both systems, the thermo-physical properties of the soil at several depths are investigated for the implementation of the underground heat-exchanger. This heat-exchanger is connected to the condenser and the absorber of both systems, to supply cooling water at inlet temperatures of 33 °C in hot climate conditions, with ambient temperatures varying from 38 °C to 42 °C. The results show a steady operation for both absorption chillers in climate conditions which had not previously allowed the two systems to operate in water or air-cooled modes. A maximum coefficient of performance of 0.76 and 1.25 is... [more]

After being neglected for a long time, in the last years, ships have been recognized and studied as sound emitters. The sound energy they generate impacts the outside, but it can also affect the indoor quality of life if the environments are not properly designed. In fact, acoustic comfort plays a pivotal role, particularly in recreational crafts. In the present work, room acoustics and acoustic camera measurements were performed, inside a 50 m length overall yacht, chosen as a case study in order to evaluate the acoustic comfort. The Italian classification procedure UNI 11367:2010 for buildings was applied, and results have been compared to other international comfort classes. However, all of these are based on prescription for standard buildings, and the present work highlights that they do not account for the effective ship’s acoustic issues: sound energy transfer from impacts over ceilings and sound energy leakage. While attention of shipbuilders in acoustic comfort is shown in the... [more]

In this paper, we propose dynamic, short-term, financial risk management strategies for small electricity producers and buyers that trade in the wholesale electricity markets. Since electricity is mostly nonstorable, financial risk coming from extremely volatile electricity prices cannot be reduced by using standard finance-based approaches. Instead, a short-term operational planing and a proper trade diversification might be used. In this paper, we analyze the price risk in terms of the Markowitz mean−variance portfolio theory. Hence, it is crucial to forecast properly the variance of electricity prices. To this end, we jointly model day-ahead and intraday or balancing prices from Germany and Poland using ARX-GARCH type models. We show that using heteroscedastic volatility significantly improves probabilistic price forecasts according to the pinball score, especially if variance stabilizing transformation is applied prior to a model estimation. The price forecasts are then used for co... [more]

An inexpensive bio-mass-derived hard carbon from tamarind pods was used as an anode, and nitrogen and nitrogen (N)/sulfur (S) co-doped graphene were used as a cathode for novel hybrid Na-ion supercapacitors. The structural and surface morphological analyses are investigated using a range of techniques. The 3D network of the heteroatom-doped graphene skeleton edges for N and NS-doping conformations were assigned as N-RGOs (N1s-5.09 at.%) and NS-RGOs (N1s-7.66 at.% and S1s-2.22 at.%) based on energy dispersive X-ray spectroscopy elemental mapping. The negative electrode (T-HC) hard carbon was pre-treated by pre-sodiation with a half-cell process by galvanostatic charge−discharge in a sodium-ion battery at 0.01−2.5 V vs. Na/Na+. The T-HC//NS-RGO, T-HC//N-RGO, and T-HC//RGO were used to construct the Na-ion supercapacitor device. In the CV experiments, the electrochemical galvanostatic charge−discharge was studied at 1.0−4.2 V. The specific capacitance was 352.18 F/g for the T.HC/NS-RGO de... [more]

The aim of this study was to propose the workflow for integrated analysis of the 3D geostress and 1D geomechanics of an exploration in a new gas field. This integrated analysis will allow for problems associated with the inaccuracy of 1D geomechanical analysis to be overcome in a region with obvious anticline/syncline structures. The 1D geomechanical analysis of the well in the exploration of a new gas field mainly included the prediction of pore pressure and calculation of the mud weight window for safe drilling. In general, this integrated workflow included both a method for pore pressure prediction and a method for the calculation of the mud weight window, with the numerical solution of 3D geostress plus the interval velocity of formations. The procedure for the calculation of the 3D geostress of a target block was also introduced. Numerical solution of the 3D geostress of the target gas field, as well as solutions of 1D geomechanical analysis, have demonstrated the efficiency and p... [more]

Phase change material (PCM) is an effective thermal management method to improve the thermoelectric conversion performance of a system. PCM can not only absorb excessive thermal energy at high temperature to protect the thermoelectric module (TEM) and increase the maximum available temperature range, but also compensate for intermittent energy to extend the working time of the TEM. In the paper, the transient performance is improved by adding PCM to a traditional thermoelectric generator (TEG) system. Due to the low thermal conductivity of PCM, metal fins are used to improve the thermal conductivity of PCM. To achieve maximum efficiency of the TEG system, the Taguchi method is employed. Four factors are heat source thermal power, PCM type, height of the PCM box, and filling ratio of the PCM, respectively. The results show that heat source thermal power has the greatest effect, and PCM has the least effect on the conversion efficiency of the TEG system. Conversion efficiency from therma... [more]

Smart cities are aimed at connecting urban infrastructures to enhance the efficiency of their operation and services while taking sustainability goals into consideration. As a result of the intermittency associated with renewable generation, smart city systems such as smart grids and microgrids may not be able to ensure the security of supply. This can be mitigated by allowing these systems to trade surplus energy with other neighboring systems through local energy markets based on peer-to-peer schemes. Such an approach can play an important role on achieving sustainability due to the positive impacts at the economic, social, and environmental level. Therefore, this work explores the design of local energy markets to help determine how they are relevant to smart grid and microgrid applications and what their contributions are to sustainability in smart cities. Essentially, this is achieved by performing a literature review to address key characteristics related to the design of local e... [more]

The natural gas quality fluctuates in complex natural gas pipeline networks, because of the influence of the pipeline transmission process, changes in the gas source, and fluctuations in customer demand in the mixing process. Based on the dynamic characteristics of the system with large time lag and non−linearity, this article establishes a deep−learning−based dynamic prediction model for calorific value in natural gas pipeline networks, which is used to accurately and efficiently analyze the dynamic changes of calorific value in pipeline networks caused by non−stationary processes. Numerical experiment results show that the deep−learning model can effectively extract the effects of non−stationary and large time lag hydraulic characteristics on natural gas calorific value distribution. The method is able to rapidly predict the dynamic changes of gas calorific value in the pipeline network, based on real−time operational data such as pressure, flow rate, and gas quality parameters. It h... [more]

Hybrid propulsion dedicated to light duty vehicles is seen as an evolutionary change from internal combustion engine (ICE) to electric propulsion. Widespread direct replacement of convection ICEs in the current energy system is impossible because ICEs are vehicles’ main source of mechanical energy. The hybrid powertrain uses the advantages of electric propulsion with the ability to charge the traction battery or have the internal combustion engine assist the system. The article compares different types of hybrid drives (with a small share of plug-in hybrid propulsion) under typical urban driving conditions. Nine vehicles were tested, and the tests were conducted over several months in various cities in Poland. The terms of the research conducted were not under the requirements of the driving test. However, they are authoritative when using the vehicle in real traffic conditions. Such conditions take into account many aspects that are relevant to a road test. It was found that urban con... [more]

Algae have the potential to be used as a feedstock for the synthesis of valuable compounds and biofuels. In addition, algal waste can be further transformed into biofuel, biogas, and biochar using different thermochemical processes such as microwave pyrolysis, pyrolysis, torrefaction, and hydrothermal conversion. Due to its high specific surface area, rapid electron transport, and graphitic carbon structure, algal biochar carbonized at high temperatures has shown outstanding performance for applications as CO2 adsorbents, supercapacitors, and persulfate activation. Due to the combination of various functional groups and porous structures, the algae biomass pyrolysis at a moderate temperature produced high-quality biochar that shows high performance in terms of pollutant removal, while low-temperature pyrolysis produces coal fuel from algae via torrefaction. Over time, there have been exponentially more petroleum-based polymers created that have harmful impacts on both humans and the en... [more]

Near-zero carbon emission power (NZCEP) plants, consisting of gas-fired units; wind turbines; power-to-gas (P2G); and carbon capture, utilization and storage (CCUS) systems, have recently received a lot of attention due to their enormous benefits in reducing carbon emissions and increasing the consumption of renewable energy. However, a complex environment of interest and a combination of risks makes their development very slow. This paper establishes a risk analysis framework for NZCEP considering multi-stakeholder participation. Firstly, a synthetic risk factor system was constructed based on stakeholders’ interests. Subsequently, interval type II trapezoidal fuzzy numbers were used and final weights were calculated from both subjective and objective aspects. Finally, we applied an acronym in Portuguese of the interactive and multi-criteria decision-making (TODIM) method to site selection to achieve a balance of interests of all stakeholders. In addition, a case study was conducted.... [more]