Low-voltage grid-connected microgrids rely on the exploitation of inverter-interfaced distributed energy resources (DERs) in order to feed loads and to achieve bidirectional power flow controllability at their point of common coupling (PCC) with the upstream grid. However, adverse operational conditions, such as the existence of DERs of different operation natures, DERs of non-equal power ratings, as well as the occurrence of non-steady and non-sinusoidal grid voltage scenarios, bring complications to microgrid energy management. Consequently, control strategies employed to coordinate DERs in dispatchable microgrids need to be resilient to such non-ideal conditions. Hence, this paper demonstrates that a multi-purpose strategy, so-called the Generalized Current-Based Control (GCBC) approach, is capable of steering DERs under such adverse operational scenarios, ensuring proportional current sharing among them while also regulating the microgrid power dispatchability at the PCC. The discu... [more]

Shallow geothermal energy is a clean and effective form of energy that can overcome the problems associated with the depletion of carbon-based energy carbon emissions. Due to the special hydrogeological conditions in karst regions, the heat transfer between heat exchange boreholes and the ground formation is a complicated, multi-physical process. The abundant groundwater flow plays an important role in the heat transfer process, and even presents an opportunity to mitigate the heat imbalance during the long term operation of ground-coupled heat pumps (GCHP). In this study, both laboratorial experiments and numerical simulations were performed to analyze the mechanism that shows how fracture water impacts on heat capacity and the thermal imbalance of the energy storage rock mass. The results showed that the overall temperature fluctuation of the rock mass was reduced by the fracture water, and the temperature curve with time became gentler, which means in practice that the heat imbalanc... [more]

This paper describes a system for the automatic determination of rock-breaking target poses for impact hammers used in underground mines. The rock-breaking target pose is defined as the position and angle at which the impact hammer must strike a rock in order to break it. The automatic determination of this pose is essential for the autonomous operation of an impact hammer. The proposed system takes as input sensor data composed of point clouds and images, and automatically determines a rock-breaking target pose. The system consists of a rock segmentation subsystem that receives the sensor data and identifies and individualizes the rocks/boulders present above the grizzly, and a rock-breaking target pose generation and evaluation subsystem that receives the rock information produced by the rock segmentation subsystem, and generates a list of rock-breaking target pose candidates, it evaluates them, and it selects the best candidate as the rock-breaking target pose. The system is evaluat... [more]

Universal power converters (UPCs) have aroused significant attention in performing multiple operations in a single power converter. Furthermore, they contribute to economic operation and improved system performance. In this work, a new configuration of the universal power converter (UPC) was proposed by using a simple switching arrangement. It can perform different modes of operations, such as AC−DC, DC−DC, DC−AC, AC−AC, and cyclo-converter operations. In DC−DC conversion, the proposed configuration can perform buck mode, boost mode, and buck−boost mode of operations. Moreover, in DC−AC conversion, it gives better total harmonic distortion (THD). The effectiveness of the proposed configuration was verified by an extensive simulation, using MATLAB/Simulink environment. A low-power prototype circuit was designed to test the viability of the proposed circuit configuration and validated with simulation results.

With the expansion of wind power grid integration, the challenges of sharp fluctuations and high uncertainty in preparing the power grid day-ahead plan and short-term dispatching are magnified. These challenges can be overcome through accurate short-term wind power process prediction based on mining historical operation data and taking full advantage of meteorological forecast information. In this paper, adopting the ERA5 reanalysis dataset as input, a short-term wind power prediction framework is proposed, combining light gradient boosting machine (LightGBM), mutual information coefficient (MIC) and nonparametric regression. Primarily, the reanalysis data of ERA5 provide more meteorological information for the framework, which can help improve the model input features. Furthermore, MIC can identify effective feature subsets from massive feature sets that significantly affect the output, enabling concise understanding of the output. Moreover, LightGBM is a prediction method with a stro... [more]

A deep review of the state of the electromobility in urban public transport by bus was conducted from all different charging strategies, types of chargers, and e-buses with a general overview and SWOT analysis. A review of five case studies worldwide was also conducted and a real case study with real data was shown in depth: EMT Madrid, where all chargers and charging systems were developed in a single operation center. Total Cost of Ownership (TCO) from the literature and from the case study for e-buses were shown as compared with different bus technologies.

This paper presents a dedicated system for de-icing trolley wires. The proposed issue is appropriately under the protection of intellectual property for solving as described in patent no.B1 230665 PL in the Patent Office of the Republic of Poland. In the solution presented herein, de-icing is achieved mainly by electrodynamic force excitation and secondarily as a result of heating. Because ice is removed primarily through vibrations, it avoids a large consumption of electricity associated with the high specific heat of water. More importantly, operation is nearly simultaneously applied to the total distance of the trolley power grid between two substations. For this reason, it requires less electricity consumption and less time to apply than in heating, mechanical, or chemical methods.

Insular power systems are a special case of infrastructure for power production due to their particular land morphology with extensive hills and ridges. For a higher renewable energy share in the power production, a dedicated design according to local constraints is required. The high wind and solar resources of such cases can be utilized with offshore wind turbines and concentrating solar power, respectively. In addition, pumped-hydro storage is a mature and suitable technology for such terrain. A case study is presented in the island of Rhodes to obtain a renewable energy penetration higher than 70%. The technical and financial requirements for this implementation support the design of this system, while the introduction of concentrating solar power enables significant energy savings during the periods of peak demand of the island. An annual RES penetration close to 80% can be achieved with the combined operation of both plants. The economic viability of the required investment can b... [more]

For the multi-energy power system composed of thermal power, wind power, and a pumped-storage power station aiming at minimizing coal consumption of the power grid, an optimal dispatch model is established in this paper. Its advantage is to allow the power grid to accept a high proportion of new energy while ensuring power demand. The dynamic programming method is used to solve the problem. In the solution process, the traditional dynamic programming method is improved by introducing the penalty function and the dynamic value of the state variable, which can ensure the reliability of the power supply while achieving the optimization goal, as well as realize the full utilization of energy. Using the example of a high proportion of wind power systems with a pumped-storage power station as the energy storage mode and considering the relevant constraints after the heating transformation of the thermal power plant, our built model solves these challenges. The results show that when the maxi... [more]

Sprinkler skipping is an important issue in fire spread. In general, two sprinklers are installed in air conditioner rooms at the ceiling and 30 cm below to avoid spray failure by energy recovery ventilator in the ceiling. However, there is a problem in that sprinkler skipping occurs in the air conditioner room. In this study, the sprinkler skipping phenomenon was analyzed through numerical analysis and the applicability of the open type of sprinkler operation method was reviewed. As a result, when the upper sprinkler works, sprinkler skipping occurred in all cases. The lower sprinkler shall not rise above the operating temperature of 68.3 °C with a maximum temperature of 65 °C. In particular, the spray failure caused by the energy recovery ventilator reduces the sprinkler head temperature by more than 8 °C by concentrating the spray droplets. As an open type, simultaneous operation of two sprinklers is capable of obtaining an appropriate fire extinguishing effect by covering the fire... [more]

Wearable technology represents a new technological paradigm for promoting physical activity, enabling monitoring of performances and athletic gestures. In addition, they can be employed for remote health monitoring applications, allowing continuous acquisition of users’ vital signs directly at home, emergency alerting, and computer-assisted rehabilitation. Commonly, these devices depend on batteries which are not the better option since researchers aim for dispositive who need minimal human intervention. Energy harvesting devices can be useful to extract energy from the human body, especially by integrating them into the garments, giving health monitoring devices enough energy for their independent operation. This review work focuses on the main new wearable technologies and devices to scavenge energy from the human body. First, the most suitable energy sources exploitable for wearable applications are investigated. Afterward, an overview of the main harvesting technologies (piezoelect... [more]

The objective of this paper is to investigate the future evolution of port systems considering the development of major and minor ports, inter-port competition, and feasible cargo shifts resulting from improved capacity or congestion faced by ports. The literature review on port system dynamics indicates that the relationships that emerge between major and minor ports located in the range stem from competition and cooperation. However, we argue that there are essential ports that play a predominant role in shaping these relationships, while inter-port relations in the system are based on competition. With the use of transshipment forecasts, existing and emerging interdependencies among major and minor ports in the system, and capacity development and/or changes in the level of capacity utilisation, the ex-ante dynamics of the port system are evaluated. The subject of research is two port systems, namely, the Polish port system and the Rhine−Scheldt Delta port system. We investigate the... [more]

Oil mist adversely affects the health of workplace workers, and for this reason, regulations on the limitation of the oil-mist exposure of workers are becoming stricter. In order to reduce the amount of the exposure of workers to oil mist, it is important to effectively remove oil mist from machine tools. In this study, the collection efficiency according to the geometry of the oil-mist-collection cyclone consisting of several disks and the output power and rotation speed of the motor were evaluated. Most of the generated oil mists were less than 10 μm, and the mist removal was assessed using an optical particle counter. The cyclone airflow rate increased linearly with the rotational speed, and the rate was affected more by the cyclone geometry than by the power consumption. The mist-removal performance was significantly enhanced when plate- and cone-type disks were added to the rotating blades. The removal efficiencies of PM10 and PM2.5 under the maximum operational conditions of 5000... [more]

Smart meters (SMs) can play a key role in monitoring vital aspects of different applications such as smart grids (SG), alternative currents (AC) optimal power flows, adversarial training, time series data, etc. Several practical privacy implementations of SM have been made in the literature, but more studies and testing may be able to further improve efficiency and lower implementation costs. The major objectives of cyberattacks are the loss of data privacy on SM-based SG/power grid (PG) networks and threatening human life. As a result, losing data privacy is very expensive and gradually hurts the national economy. Consequently, employing an efficient trust model against cyberattacks is strictly desired. This paper presents a research pivot for researchers who are interested in security and privacy and shade light on the importance of the SM. We highlight the involved SMs’ features in several applications. Afterward, we focus on the SMs’ vulnerabilities. Then, we consider eleven trust... [more]

This article aims to analyze agents’ behavior in a competitive hydrothermal energy market. The idea is to investigate how much the day-to-day behavior of the market can be different from the predictions presented by cost-based models because of the risk perception of each agent (hydroelectric energy producer, in this case) as a participant of the market. The main contribution is in determining the impact on the agents’ revenue in the short-term market due to the variation in the amount of energy generated and the market price, which other methodologies may not be able to capture. For this reason, a case study was made using daily simulations in a given month, observing the strategy and bids of eight hydroelectric agents for a central market operator emulated by an energy price offer simulator called SOPEE. The study reflected qualitative and quantitative examples of how the risk perception and the behavior of each agent can influence market behavior due to the variation in their percep... [more]

As a retailer between the energy suppliers and end users, the integrated energy service provider (IESP) can effectively coordinate the energy supply end and the energy use end by setting energy prices and energy management. Because most of the current research focuses on the pricing of electricity retailers, there are few studies on IESP energy pricing and management, which are still at the initial stage. At the same time, the existing research often does not consider the impact of demand response (DR) and uncertainties, such as natural gas and electricity wholesale prices, on the pricing of IESP. It is necessary to model the DR and uncertainties in the integrated energy system. Aiming at the inadequacy of the existing research and to address the energy pricing and management of IESP, this paper develops a two-stage stochastic hierarchical framework, which comprehensively considers the DR strategy of the user end, characteristics of the electricity/gas/heat storage and the uncertaintie... [more]

This paper presents the performance of the 26 kVA inductive high-current transformer (HCT) during operation in the frequencies range of transformed harmonics from 50 Hz to 5 kHz. Performed research concerns the determination of the possibility of obtaining an order of the higher harmonic of a given RMS value in its distorted output current for the required RMS value of the main component and the maximum safe instantaneous value of the input voltage equal to 400 V. The results are presented for serial, serial-parallel and parallel configurations of primary and secondary windings (9 cases). Therefore, the most favourable configuration of the primary and secondary windings sections may be chosen. The tests are performed for the transformation of the distorted current containing a fundamental component and one higher harmonic of order from the 5th changed by the 5 up to the 100th. The constant 10% higher harmonic level in relation to the main component of the distorted secondary current is... [more]

Due to the insufficient consideration of medium and long-term wind power contract power in short-term dispatch, long-term planning and real-time consumption of wind power cannot be effectively undertaken, resulting in a large amount of abandoned wind power. A way to improve the wind power absorption capacity has become an urgent problem to be studied. According to the characteristics of the market and dispatching in the process of wind-fire integration construction, this paper constructs a wind power consumption model that connects the mid- and long-term transaction power decomposition and short-term dispatch. Considering the unit output characteristics and maintenance, the monthly contract electricity is decomposed into daily electricity, and the nesting of medium and long-term transactions and short-term scheduling is realized; the second stage is a short-term multi-objective optimal scheduling model considering the decomposition of contract electricity and the output of non-bidding... [more]

The production of syngas with optimal energy usage, a minimal environmental impact, and an adjustable H2/CO molar ratio is possible using tri-reforming of methane (TRM). Despite the number of studies dedicated to the TRM process, this process is still in its infancy, with many technical obstacles to overcome. Except for its kinetics and catalysts, which have been reviewed elsewhere, the TRM process is evaluated thoroughly in this work. First, feasibility studies of TRM and the TRM process are presented. Second, the impacts of various operating conditions on the rate of gas conversions, syngas production, and coke formation are discussed. Third, different reactor configurations are compared. This review then goes through the energy and energetic efficiency, economic, environmental, and safety aspects of the TRM process. Finally, a research path for the future is suggested.

The paper aims to give a universal methodology for assessing the storage capacity of a bedded rock salt formation in terms of the operational and strategic storage facilities for liquid fuels. The method assumes the development of a geological model of the analyzed rock salt formation and the determination of the salt caverns’ size and spacing and the impact of convergence on their capacity during operation. Based on this method, the paper presents calculations of the storage capacity using the example of the bedded rock salt formations in Poland and their results in the form of storage capacity maps. The maps show that the analyzed rock salt deposits’ storage capacity in northern Poland amounts to 7.1 B m3 and in the Fore-Sudetic Monocline to 10.5 B m3, in the case of strategic storage facilities. The spatial analysis of the storage capacity rasters, including determining the raster volumes and their unique values, allowed us to quantify the variability of the storage capacity in the... [more]

This paper presents an efficient and fast fault-tolerant control scheme for a bidirectional Z-source inverter (BiZSI)-fed induction-motor drive system for vehicular applications. The proposed strategy aims for the fault detection, localization and diagnosis of the proposed system during switch failures in the inverter module. Generally, power−semiconductor switch failures in inverter modules occur due to open- and short-circuit faults. An efficient modulation scheme is proposed and design specifications are thoroughly derived to obtain high voltage gains across the BiZSI network. A suitably fast detection and diagnosis scheme to isolate the faulty leg and resume the normal operation is discussed in this paper. The control scheme is provided such that the faulty leg is isolated and the motor phase is fed from a redundant leg to resume the operation. A feasible localization algorithm based on experimentally derived values and switching vectors is implemented. In addition, a fast fault di... [more]

With the rapid development of electric vehicles (EVs), many EV batteries have entered the retirement stage, leading to increasing concerns about the impact of resource recycling and environmental sustainability. Some countries have successfully applied reward−penalty and deposit−refund mechanisms in similar fields, such as lead-acid and waste portable batteries. However, whether these mechanisms are conducive to collecting waste EV batteries is unclear. This study aims to comprehensively analyze the influence of reward−penalty and deposit−refund mechanisms in EV battery collection by developing a Stackelberg game theoretical model. In the model, the recycling enterprise is the leader and the EV manufacturer is the follower. Furthermore, the total social welfare is used as the indicator to select the optimal incentive mechanisms. The results show that (1) both mechanisms could improve collection rates and recycling enterprises’ profits, though the collection rate is lower under the rewa... [more]

With the completion of the Lianghekou Reservoir, with a multiyear regulation capacity, the operation relationship of the cascade reservoirs in the Yalong River is becoming increasingly complex. In order to study an optimal operation mode of the cascade reservoirs in the Yalong River under different inflow frequencies, based on the shortcomings of the existing single reservoir operation mode and the local joint operation mode of the cascade reservoirs, this paper first proposed a global joint operation mode for the cascade reservoirs to develop the power generation potential of daily regulating reservoirs and then gave a solution method for the cascade reservoirs’ operational model based on an improved stochastic fractal search (ISFS) algorithm. Finally, taking the maximum power generation as the goal and the inflow data of five typical years as the model inputs, this paper analyzed the differences in the power generation and water abandonment results of the cascade reservoirs in the mi... [more]

In the slider-crank mechanism, where the rotational motion is transformed into the translational motion, the input torque is highly variable due to the inertial effect. The consequence of fluctuating torque is that it causes the load upon the prime mover to be inconsistent, which might likely results in higher stresses in the components, higher joint friction, and the necessity for higher driving power. In this paper, a technique of reduction of the dynamic torque and joint forces in the slider-crank mechanism using mechanical resonance is described. A comparative result of the conventional system in the process of gas compression, as a practical application example, is presented. The result shows that the utilization of resonance has the advantage of providing lower dynamic torque and rotating joint forces compared to the conventional operation. Since the compression of the air itself takes effect as a spring compression, in the gas compression process, the narrow torque and force reg... [more]

To date, along with the rapid development of urban rail transit (URT) in China, the evaluation of operational efficiency and energy efficiency has become one of the most important topics. However, the extant literature regarding the efficiency of URT at the line level and considering carbon emissions is limited. To fill the gap, an evaluation model based on slacks-based measure (SBM) data envelopment analysis (DEA) is proposed to measure the efficiencies, which is applied to 61 URT lines in China’s four megacities. The findings are summarized as follows: (1) The average operational efficiency and energy efficiency of URT lines are low, and both have great room for improvement. (2) There are significant disparities in the efficiency of URT lines in the case cities. For instance, the average operational efficiency of URT lines in Guangzhou is higher than that of other cities, while the average energy efficiency of URT lines in Shanghai is higher than that of other cities. (3) The URT lin... [more]