Electrical Energy Research Articles

A S-scheme 0D/2D heterojunction formed by decorating Cd0.5Zn0.5S nanoparticles on Cu2MoS4 plates for efficient photocatalytic hydrogen generation

Rationally designing a Step-scheme (S-scheme) hetero-structured photocatalyst with high redox capability and separation efficiency of photoinduced carriers is considered as an attractive approach to address the shortcomings of single component and traditional hetero-structured photocatalyst. Herein, enlightened by the predictions of density functional theory (DFT), a unique S-scheme heterojunction photocatalyst was successfully fabricated by incorporating zero-dimensional (0D) Cd0.5Zn0.5S (CZS) on two-dimensional (2D) lamellar Cu2MoS4 (CMS) plates via a facile coprecipitation method, which substantially enhances the photocatalytic activity for hydrogen (H2) generation. CZS nanoparticles deposited on the surface of CMS nanoplates play a crucial role in creating highly intimate heterojunction interfaces and abundant exposed reaction sites, laying the foundation for improved photocatalytic performance. Furthermore, the significant difference in Fermi levels and band structures between CZS and CMS result in the formation of the internal electric field (IEF) and energy band bending at the interface of the heterojunction. This S-scheme charge transfer path enables 0D/2D CZS/CMS heterojunction possesses an exceptional capacity to maintain the robust redox potential and boosts the separation efficiency of light-induced carriers, as verified by DFT calculations and energy band structure analyses. As expected, the optimal heterojunction exhibits a satisfactory H2 generation rate of 13.1 mmol·g-1·h−1, which is nearly 7.7-fold higher than that of individual CZS. This study is expected to inspire the design of morphology-controlled hetero-structured photocatalyst with S-scheme charge transfer route for photocatalytic H2 generation.

A S-scheme 0D/2D heterojunction formed by decorating Cd0.5Zn0.5S nanoparticles on Cu2MoS4 plates for efficient photocatalytic hydrogen generation

Rationally designing a Step-scheme (S-scheme) hetero-structured photocatalyst with high redox capability and separation efficiency of photoinduced carriers is considered as an attractive approach to address the shortcomings of single component and traditional hetero-structured photocatalyst. Herein, enlightened by the predictions of density functional theory (DFT), a unique S-scheme heterojunction photocatalyst was successfully fabricated by incorporating zero-dimensional (0D) Cd0.5Zn0.5S (CZS) on two-dimensional (2D) lamellar Cu2MoS4 (CMS) plates via a facile coprecipitation method, which substantially enhances the photocatalytic activity for hydrogen (H2) generation. CZS nanoparticles deposited on the surface of CMS nanoplates play a crucial role in creating highly intimate heterojunction interfaces and abundant exposed reaction sites, laying the foundation for improved photocatalytic performance. Furthermore, the significant difference in Fermi levels and band structures between CZS and CMS result in the formation of the internal electric field (IEF) and energy band bending at the interface of the heterojunction. This S-scheme charge transfer path enables 0D/2D CZS/CMS heterojunction possesses an exceptional capacity to maintain the robust redox potential and boosts the separation efficiency of light-induced carriers, as verified by DFT calculations and energy band structure analyses. As expected, the optimal heterojunction exhibits a satisfactory H2 generation rate of 13.1 mmol·g-1·h−1, which is nearly 7.7-fold higher than that of individual CZS. This study is expected to inspire the design of morphology-controlled hetero-structured photocatalyst with S-scheme charge transfer route for photocatalytic H2 generation.

Calculation of electrical energy losses in distribution networks for power supply using oil and vacuum circuit breakers

A method for approximate estimation of load losses in distribution networks from 6 to 10 kV, as well as for lower voltage networks, has been proposed. The main advantage of this method is that the root mean square current is calculated only once for a series of calculations. This approach significantly reduces the time required for calculations and improves their accuracy, as it eliminates the need for multiple determinations of the root mean square current for each individual calculation. The proposed approach contributes to a better understanding of the influence of various factors on load losses, which allows for more effective planning and management of distribution networks. This is particularly important in the context of increasing loads on electrical networks and higher demands for their reliability and efficiency. In the calculation of electrical energy losses in distribution networks from 6 to 10 kV, methods that use generalized coefficients of electrical circuits and operating modes in the form of regression equations are widely applied. The most significant and independent factors, such as the input of active energy, total line length, number of line sections, total number of transformers, and their total installed capacity, must be taken into account and are included in the calculation equation. Additionally, the components used and their regular maintenance play an important role in electrical energy losses in electrical networks. The main direction of research is the optimization of distribution network parameters, taking into account the latest technologies and materials, as well as the implementation of automated monitoring and control systems that will allow timely detection and elimination of problems associated with electrical energy losses. The proposed method for estimating load losses in distribution networks is a promising direction for the development of the energy sector, which will contribute to improving the efficiency and reliability of electrical networks, as well as reducing the costs of their operation and maintenance.

Experience in the development and use of simulators for professional training of specialists in the electric power industry

Issues of development of simulators for training and testing of electrical engineers and students of electrical engineering specialties were considered. They are based on modern knowledge in the field of electricity. The main characteristics of simulators and requirements for their computer support are given. The developments implement a new method of practical training and testing of electrical engineers and can be used at all stages of electrical engineer training. The considered simulators are based on a combination of practical and theoretical knowledge of the electric power industry. The purpose of the developments is to activate and increase the efficiency of the educational process due to the introduction of new learning technologies. The technical capabilities of the software implement both individual and team work of students and electric power personnel. It was noted that in recent years, two professional simulators, implemented in the form of two laboratory workshops, have been developed and implemented in the educational process at the department of electrical energy transmission of National technical university “Kharkiv polytechnic institute”. The first helps students study the main provisions of the Normative Documentation in the power industry, the second – the rules and sequence of operational switching in electrical networks. In addition, experts determine the high efficiency of training systems based on precedent-analytical models. The exercise program according to the plan-do-check-act cycle is considered. Its basis is the well-known concept of continuous quality improvement “Plan-Do-Check-Act” (Deming's cycle). For the electric power industry, a plan-do-check-act cycle approach can consist of cyclical planning of activities, implementation of planned actions, verification of results obtained and correction of non-conformance to expectations. The precedent-scenario method of constructing a training system based on the software platform of the training system based on the plan-do-check-act scenario is presented in detail.

Development of a conceptual model for management of technological losses of electricity in distribution networks 150-0.38 kV

The work developed a conceptual model of the process of managing the technological costs of electrical energy in 150-0.38kV distribution networks. The relevance and necessity of developing a conceptual model of the process of managing the technological costs of electricity, which is carried out in relation to the system of distribution of electrical energy (or the electrical distribution system) as a whole, including distribution electrical networks of 150-0.38 kV, is analyzed. The paper proposes a conceptual decomposition, considers the description and formalization of the power distribution system management process based on the criterion of reducing the technological costs of electricity. The proposed conceptual model describes the process of managing the technological costs of electricity in the power distribution system, as a process of regular improvement (optimization) of the functioning of the power distribution system and allows further optimization and automation of the process of managing the technological costs of electricity in the power distribution system, in order to achieve higher levels of energy efficiency of its functioning. It is shown that this model can be used to solve the tasks of not only strategic and tactical management (in terms of years and months) when forming development plans and current operation of distribution systems, but also operational optimization of technological costs of electricity at the pace of the process. Provided that the appropriate software is developed (including the forecasting of power distribution system modes and external environmental influences), the system for managing the technological costs of electrical energy is represented by three control loops that correspond to the stages of its development. Processes and information links between them are shown for each control loop. Each process in the conceptual model of the management of technological costs of electric energy has its own formal representation through generalized functional dependencies, and the information links between the processes correspond to the arguments and values of these functions. The conceptual model describes the process of managing the technological costs of electrical energy in the power distribution system as a process of regular improvement (optimization) of its functioning through increasing its energy efficiency.

Construction of the structure of rural electric networks taking into account the availability of renewable sources of electricity

It is noted that although the share of renewable electricity sources continues to grow and develop rapidly, the industry still faces many challenges, including how to continue to reduce electricity losses and annualized costs, improve operation and maintenance efficiency, maintain grid stability, ensure safety and reliability of the power supply system containing renewable sources of electrical energy. It is shown that an effective solution to these problems is possible only on the basis of the analysis of the prospects for the development of local electric power systems that contain renewable sources of electric energy, the development of technical and organizational support mechanisms that will contribute to the construction of modern system (schematic) solutions. It is proposed to apply the potential surface method for building the optimal structure of the rural electrical network during its design and modernization in the presence of renewable sources of electrical energy, which allows optimizing the structure of the network from the point of view of electrical energy losses and reducing annualized costs. The algorithm for forming the structure of power supply systems is described, which implements the simultaneous solution of the tasks of determining the number of load nodes, distributing electrical receivers between them, determining the design of power sources, taking into account the discreteness of the design of system elements. The results of numerical modeling based on the proposed algorithm are presented on the example of solving the problem of reconstruction of a section of the rural electricity network.

ТЕПЛОФИЗИЧЕСКАЯ МОДЕЛЬ И РЕЗУЛЬТАТЫ ЭКСПЕРИМЕНТАЛЬНОГО ИССЛЕДОВАНИЯ ГАЗИФИКАЦИИ ДРЕВЕСНЫХ И РАСТИТЕЛЬНЫХ ОТХОДОВ

The article compares the calculation results using the developed thermophysical composition model for the study of thermal gasification of wood and plant waste – renewable natural energy resources in a gas generator with the reverse combustion process and forced steam-air blast, which allows to achieve minimal formation of a by-product – resin. Based on the thermophysical model, the optimal consumption of solid fuel – wood and plant waste and oxidizer – atmospheric air is determined. The work can be used by technical engineers at enterprises in Russia and abroad for the environmentally friendly disposal of wood and plant waste in autonomous energy technology installations with combustion gas generators to generate thermal and electrical energy for the consumer. In particular, large volumes of wood and plant waste accumulate at wood processing and agricultural enterprises in the Tyumen region, which are an additional cheap source of energy.

Experience in the development and use of simulators for professional training of specialists in the electric power industry

Issues of development of simulators for training and testing of electrical engineers and students of electrical engineering specialties were considered. They are based on modern knowledge in the field of electricity. The main characteristics of simulators and requirements for their computer support are given. The developments implement a new method of practical training and testing of electrical engineers and can be used at all stages of electrical engineer training. The considered simulators are based on a combination of practical and theoretical knowledge of the electric power industry. The purpose of the developments is to activate and increase the efficiency of the educational process due to the introduction of new learning technologies. The technical capabilities of the software implement both individual and team work of students and electric power personnel. It was noted that in recent years, two professional simulators, implemented in the form of two laboratory workshops, have been developed and implemented in the educational process at the department of electrical energy transmission of National technical university “Kharkiv polytechnic institute”. The first helps students study the main provisions of the Normative Documentation in the power industry, the second – the rules and sequence of operational switching in electrical networks. In addition, experts determine the high efficiency of training systems based on precedent-analytical models. The exercise program according to the plan-do-check-act cycle is considered. Its basis is the well-known concept of continuous quality improvement “Plan-Do-Check-Act” (Deming's cycle). For the electric power industry, a plan-do-check-act cycle approach can consist of cyclical planning of activities, implementation of planned actions, verification of results obtained and correction of non-conformance to expectations. The precedent-scenario method of constructing a training system based on the software platform of the training system based on the plan-do-check-act scenario is presented in detail.

Development of a conceptual model for management of technological losses of electricity in distribution networks 150-0.38 kV

The work developed a conceptual model of the process of managing the technological costs of electrical energy in 150-0.38kV distribution networks. The relevance and necessity of developing a conceptual model of the process of managing the technological costs of electricity, which is carried out in relation to the system of distribution of electrical energy (or the electrical distribution system) as a whole, including distribution electrical networks of 150-0.38 kV, is analyzed. The paper proposes a conceptual decomposition, considers the description and formalization of the power distribution system management process based on the criterion of reducing the technological costs of electricity. The proposed conceptual model describes the process of managing the technological costs of electricity in the power distribution system, as a process of regular improvement (optimization) of the functioning of the power distribution system and allows further optimization and automation of the process of managing the technological costs of electricity in the power distribution system, in order to achieve higher levels of energy efficiency of its functioning. It is shown that this model can be used to solve the tasks of not only strategic and tactical management (in terms of years and months) when forming development plans and current operation of distribution systems, but also operational optimization of technological costs of electricity at the pace of the process. Provided that the appropriate software is developed (including the forecasting of power distribution system modes and external environmental influences), the system for managing the technological costs of electrical energy is represented by three control loops that correspond to the stages of its development. Processes and information links between them are shown for each control loop. Each process in the conceptual model of the management of technological costs of electric energy has its own formal representation through generalized functional dependencies, and the information links between the processes correspond to the arguments and values of these functions. The conceptual model describes the process of managing the technological costs of electrical energy in the power distribution system as a process of regular improvement (optimization) of its functioning through increasing its energy efficiency.

Construction of the structure of rural electric networks taking into account the availability of renewable sources of electricity

It is noted that although the share of renewable electricity sources continues to grow and develop rapidly, the industry still faces many challenges, including how to continue to reduce electricity losses and annualized costs, improve operation and maintenance efficiency, maintain grid stability, ensure safety and reliability of the power supply system containing renewable sources of electrical energy. It is shown that an effective solution to these problems is possible only on the basis of the analysis of the prospects for the development of local electric power systems that contain renewable sources of electric energy, the development of technical and organizational support mechanisms that will contribute to the construction of modern system (schematic) solutions. It is proposed to apply the potential surface method for building the optimal structure of the rural electrical network during its design and modernization in the presence of renewable sources of electrical energy, which allows optimizing the structure of the network from the point of view of electrical energy losses and reducing annualized costs. The algorithm for forming the structure of power supply systems is described, which implements the simultaneous solution of the tasks of determining the number of load nodes, distributing electrical receivers between them, determining the design of power sources, taking into account the discreteness of the design of system elements. The results of numerical modeling based on the proposed algorithm are presented on the example of solving the problem of reconstruction of a section of the rural electricity network.

Calculation of electrical energy losses in distribution networks for power supply using oil and vacuum circuit breakers

A method for approximate estimation of load losses in distribution networks from 6 to 10 kV, as well as for lower voltage networks, has been proposed. The main advantage of this method is that the root mean square current is calculated only once for a series of calculations. This approach significantly reduces the time required for calculations and improves their accuracy, as it eliminates the need for multiple determinations of the root mean square current for each individual calculation. The proposed approach contributes to a better understanding of the influence of various factors on load losses, which allows for more effective planning and management of distribution networks. This is particularly important in the context of increasing loads on electrical networks and higher demands for their reliability and efficiency. In the calculation of electrical energy losses in distribution networks from 6 to 10 kV, methods that use generalized coefficients of electrical circuits and operating modes in the form of regression equations are widely applied. The most significant and independent factors, such as the input of active energy, total line length, number of line sections, total number of transformers, and their total installed capacity, must be taken into account and are included in the calculation equation. Additionally, the components used and their regular maintenance play an important role in electrical energy losses in electrical networks. The main direction of research is the optimization of distribution network parameters, taking into account the latest technologies and materials, as well as the implementation of automated monitoring and control systems that will allow timely detection and elimination of problems associated with electrical energy losses. The proposed method for estimating load losses in distribution networks is a promising direction for the development of the energy sector, which will contribute to improving the efficiency and reliability of electrical networks, as well as reducing the costs of their operation and maintenance.

Formation the coefficient of growth for the power scale of transformers taking into account the operational indicators of substations

The article describes the sequence of formation of the growth coefficient of the transformers power scale, taking into account the operational indicators of substations. For this purpose, an expression for finding the optimal power of 110 kV transformers has been developed on the basis of a technical-economic model of costs for the transformation of electrical energy. The developed expression is used to find the optimal power of transformers of 110 kV in conventional units, taking into account the load of substations, which is the basis for the formation of the growth coefficient of the transformers power. The search for optimal power was performed on the basis of deviations of the indicators of the maximum load of transformers and the time of maximum losses. The time indicators of maximum losses and maximum load are calculated according to the hourly load data of transformers, taking into account the presence of generation nodes on the secondary voltage buses. The formation of the growth coefficient of the scale of transformers is performed by finding the mathematical expectation of the optimal power and its shift based on the boundaries of the distribution of two adjacent powers of transformers. The substantiation of the formed coefficient of growth of the transformers power was performed according to the criterion of minimum technological losses of electrical energy, by comparing the daily loses schedules in transformers. According to the research results, it follows that the application of the obtained coefficient allows to reduce the level of technological losses. The study was carried out on the example of operating substations with two-winding transformers of 110 kV using the scheme of the established mode of operation of the electric network.

Galvanostatic Electroshock Synthesis of Low Loading Au-Pt Nanoalloys onto Gas Diffusion Electrodes as Multifunctional Electrocatalysts for a Glycerol-Fed Electrolyzer.

Water electrolysis is increasingly considered a viable solution for meeting the world's growing energy demands and mitigating environmental issues. An inventive strategy to mitigate the energy requirements involves substituting the energy-intensive oxygen evolution reaction (OER) with biomass-derived glycerol electrooxidation. Nonetheless, the synthesis of electrocatalysts for controlling the selectivity towards added-value chemicals at the anode and efficient H2 generation at the cathode remains a critical bottleneck. Herein, we implemented a galvanostatic electroshock synthesis approach to control the reduction kinetics of Au(III) and Pt(IV) to grow ultra-low amount of gold-platinum alloys on a gas diffusion electrode (12-26 µgmetal cm‒2) for glycerol-fed hydroxide anion exchange membrane based electrolyzer. The symmetric GDE-Au100-xPtx||GDE-Au100-xPtx systems showed a notable improvement in electrolyzer performance (GDE-Au64Pt36 = 201 mA cm-2) as compared to monometallic versions (GDE-Au100Pt0 = 18 mA cm-2, GDE-Au0Pt100 = 81 mA cm-2). Chromatography (HPLC) analysis underscores the critical importance of bulk electrolysis methodology (galvanostatic vs potentiostatic) for the efficient conversion of glycerol into high-value-added products. Regarding the electrical energy required to produce 1 kg of H2 for such an electrolyzer fed at the anode with glycerol, our results confirm a drastic decrease by a factor of at least two compared with conventional water electrolysis.

The Strategic Importance of Cyber Security in Electric Energy Policies

The Strategic Importance of Cyber Security in Electric Energy Policies

Development of solid-state hybrid capacitor using carbon nanotube film as current collector

Structural energy-storage devices are receiving considerable attention because they can simultaneously store electrical energy and provide structural support, thereby offering high volumetric and gravimetric capacities. Although carbon fiber–based materials have been the most popular choice for current collectors, their conductivity and specific surface area are relatively low; this limits the ability to load other active materials on to the current collector. Carbon nanotube (CNT) fiber is a promising alternative for lightweight structural materials because it has a density of less than 1 g cm−3 as well as high strength and electrical conductivity. In this study, we produced a light, strong, and porous CNT film (CNTF) via direct spinning for use as a current collector. The CNTF exhibited a high specific strength compared with Al foil. We also created an activated carbon–lithium titanium oxide hybrid capacitor with the CNTF current collector, which achieved a capacity similar to that of a capacitor having an Al current collector. Furthermore, a planar pouch cell created using a solid polymer electrolyte achieved a capacity of 74.1 mAh g−1, which is comparable to that of coin cells. Thus, our findings highlight the feasibility of CNTF as a material for current collectors and provide a foundation to develop manufacturing processes for structural batteries.

Failure type and failure level detection of insulators according to monitored leakage current

Due to the ever-increasing growth of electric energy consumption, the production of high-quality, reliable and high-reliability electricity is very important. Therefore, it is essential to have distribution and sub-transmission networks with a good reliability factor. In power distribution and sub-transmission lines, it is necessary to somehow isolate the conductors under voltage from the towers, and insulators are used for this purpose. These insulators have two main tasks. One of the main tasks of insulators is to isolate (insulate) the line conductor from the body of the tower. The insulators must be able to isolate the high voltages of the lines from the body of the tower without having a leakage current, and on the other hand, the insulators must be able to withstand the mechanical forces resulting from the weight of the conductors and the applied forces caused by wind and ice. Also, leakage current is one of the important parameters for condition monitoring of insulators in power grid lines. Failure to inspect the insulation for contamination and health conditions will lead to insulator failure and will cause faults in the electrical system. Therefore, it is very important to monitor the condition of the insulator. Based on this, in this paper, according to the data related to leakage current and also according to the introduced wear out function, a procedure for measuring the condition of insulators has been obtained. Finally, the condition of each insulator will be determined according to the defined indicators. Also, the failure level of each monitored data will be obtained using sensitivity analysis.

Mapping the Potential of Zero-Energy Building in Greece Using Roof Photovoltaics

The present study investigates the incorporation of renewable rooftop photovoltaic systems in fully electrified residential buildings and estimates the zero-energy demand building potential in relation to the climatic data of Greece. Specifically, the aim of the analysis is to calculate the maximum possible number of stories and therefore the total building height for a complete transformation to zero-net-energy building. The energy analysis, which is conducted using the DesignBuilder software, focuses on single-floor up to seven-story buildings. The importance of the present work lies in the acknowledgment of the diversity of the Greek residential sector, the adherence to national energy policies, and the European goal of fully electrified buildings. The examined case studies are equipped with electrically driven air-to-air heat pumps serving the space heating and cooling demands and with an air-to-water heat pump covering the domestic hot water requirements. The investigated locations are the four main cities of Greece, Athens, Thessaloniki, Chania, and Kastoria, which represent the country’s four climatic categories. The conducted analysis allows for the mapping of the zero-energy building potential for the climatic data of Greece, demonstrating the possibility of striking a positive building energy balance through the integration of on-site renewable energy sources and the production of necessary electrical energy. The novelty of the present work lies in the identification of a key factor, namely, the building height, which determines the feasibility of transforming multifamily buildings into zero-energy buildings. According to the analysis results, the critical number of stories is calculated at six for Chania, five for Athens, four for Thessaloniki, and two for Kastoria. Regarding a three-story residential building, the incorporation of a renewable photovoltaic system can result in an annual surplus electricity production of 13,741 kWh (Chania), 10,424 kWh (Athens), and 6931 kWh (Thessaloniki), and a corresponding coverage of 100% (Chania), 69.0% (Athens), 38.9% (Thessaloniki) and 0% (Kastoria).

Enhancing Biogas Plant Efficiency for the Production of Electrical and Thermal Energy

Enhancing Biogas Plant Efficiency for the Production of Electrical and Thermal Energy

High-precision state of charge estimation of electric vehicle lithium-ion battery energy storage system based on multi-scale optimized time-varying bounded smoothing variable structure filtering algorithm

High-precision state of charge estimation of electric vehicle lithium-ion battery energy storage system based on multi-scale optimized time-varying bounded smoothing variable structure filtering algorithm

Repeatable test of a control valve with air pressure generated by an independent electric energy source

Repeatable test of a control valve with air pressure generated by an independent electric energy source