RELEVANCE of the study lies in the increasing number of nonlinear loads and power electronic devices in 6-10 kV distribution networks is causing an increase in harmonic and interharmonic distortion. This distortion is disrupting the sinusoidal nature of the voltage and accelerating equipment aging. Traditional contact-based methods for measuring power quality parameters are limited by their operating conditions and require complex measurement setups.
OBJECTIVE of this study aims to develop an algorithm for identifying distortion sources in 6-10 kV networks by analyzing signals from non-contact electromagnetic field sensors that measure inductive and capacitive fields.
METHODS of the study include spectral analysis techniques, such as Fast Fourier Transform (FFT) and Short-Time Fourier Transform (STFT), to extract harmonic and interharmonic components from the data. These techniques form spectral fingerprints, which include informative features like the variation in amplitude and phase of the fundamental harmonic (50 Hz), total harmonic distortion (THD), and the sum of even and odd harmonic amplitudes. Laboratory experiments were conducted on a 6-10 kV distribution line segment, simulating different operating modes with asynchronous motors, three-phase diodes, and single-phase non-linear loads.
THE RESULTS. show that inductive sensors are sensitive to changes in current load and magnetic flux, while capacitive sensors can detect electric field distortions and phase asymmetries. For the asynchronous motor, the total harmonic distortion (THD) decreased by up to 12% and the amplitude of the main harmonic increased by 65%. High-frequency even harmonics were generated by the diode bridge with an amplitude growth of up to +1550%. Single-phase nonlinear loads introduced phase asymmetry and increased the THD by 2-4%.
CONCLUSION states that combination of inductive and capacitive non-contact sensors allows for distinct spectral signatures which can be used as features for further identification algorithms of distortion sources. The developed algorithm can form a reference spectrum library and serve as a basis for intelligent non-contact monitoring systems for power quality control in distribution networks of 6-10 kV.

THE RELEVANCE of this article lies in its timely and critical reassessment of the "green" energy trend. It serves as a "sober voice," advocating for a balanced evaluation, comprehensive risk assessment, and a shift from ideological approaches to scientificallygrounded, holistic analysis aimed at achieving genuine sustainability. This makes it a valuable contribution not only to academic discourse but also to the development of practical government policies and corporate strategies.
THE PURPOSE. This paper conducts a comprehensive critical analysis of the modern trends, technological solutions, and systemic challenges within the green energy sector and decarbonization efforts. It aims to evaluate their actual effectiveness, economic viability, and full lifecycle environmental impacts, moving beyond the prevailing optimistic narratives to provide a balanced assessment.
METHODS. The research employs a systematic review and comparative analysis of a wide range of scientific studies and technological case studies. The methodology critically examines wind, solar, and hydrogen energy, carbon capture, utilization, and storage (CCUS) technologies, hybrid systems, and various energy storage solutions. The assessment incorporates key technological, economic, and environmental metrics, including energy return on investment (EROI), levelized cost of energy (LCOE), capital and operational expenditures (CAPEX/OPEX), and carbon footprint across the entire value chain.
RESULTS. The study identifies significant contradictions and systemic challenges in the transition to renewables. It demonstrates that many promoted solutions, such as hydrogen economy and CCUS, remain at early development stages, characterized by high costs, low EROI, and unresolved end-of-life waste management issues for wind turbine blades, solar panels, and batteries. The analysis confirms the non-viability of renewable energy sources in regions with low natural potential without substantial government subsidies. Furthermore, the mass integration of inverter-based generation reduces the overall system inertia, creating substantial risks for grid stability and reliability. The research also highlights severe environmental and social costs associated with the extraction of critical materials like lithium and cobalt, revealing a hidden negative footprint of the green energy supply chain.
CONCLUSIONS. The study concludes that the declared benefits of the green energy transition are often offset by a complex array of hidden technological, economic, and environmental problems. The radical transformation of energy systems is not an unequivocally positive process and presents multifaceted challenges. It necessitates a balanced approach, deep systemic analysis, and the development of comprehensive strategies involving the state, business, and scientific community, rather than merely following trends. A critical revision of current assessment methodologies is required to fully account for the entire lifecycle of green technologies and their true systemic costs.

RELEVANCE. The paper presents an algorithm for measuring the temperature of minimum voltage devices based on regression analysis. THE PURPOSE. Development of regression models for determining the contact temperature of circuit breakers, contactors and magnetic starters.
METHODS. The obtained models were validated by Cochran and Fisher's criterion and the significance of each of the coefficients was assessed by Student's criterion.
RESULTS. Graphical dependences for determining the contact heating temperature of the apparatuses for a number of values of rated currents at an ambient temperature of 40°C were plotted. The graphs were also constructed for the investigated devices when the ambient temperature changes from 5°C to 40°C. The constructed graphs allow to determine the value of heating temperature without preliminary calculations for circuit breakers for rated currents 40A, 63A, 100A, 160A, 250A and for contactors and magnetic starters for rated currents 40A, 63A, 100A, 250A, 400A. The obtained values of contact heating temperature were compared with GOST 403-73.
CONCLUSIONS. Models for determining the contact heating temperature allow the technical condition of the apparatus to be taken into account and can easily be modified when conditions and operating modes change.

THE RELEVANCE of the study lies in ensuring high-quality electricity supply to consumers against the background of an increasing number of technological connections. One of the most important indicators of high-quality electricity supply is the voltage in electrical networks. The article considers the problems of voltage regulation in distribution networks (DN), which helps to ensure the required quality of electricity, reduce electricity losses and increase the capacity of power transmission lines.
THE PURPOSE. Development of measures to ensure the quality of electricity using various methods of voltage regulation.
METHODS of the study include mathematical modeling of power transmission lines (PL) taking into account the static characteristics of the load, as well as modeling of processes in distribution networks using automatic voltage regulation points (AVRP) and 10/0.4 transformers equipped with tap-changer devices for high-voltage windings without excitation (PBB) with an extended voltage regulation range of up to ±10%.
RESULTS. The results of the study demonstrate the feasibility of introducing transformers with extended voltage regulation limits.
CONCLUSION. The conducted study demonstrates that both of the considered methods, namely the installation of a PARN and the transition to transformers with an extended range of PBB of ±10%, make it possible to solve a key problem: maintaining the quality of electricity within the requirements at all nodes of an extended distribution network.

THE PURPOSE. The purpose of this study is to conduct a comprehensive analysis of the impact of key parameters of the electric vehicle (EV) fleet and electric vehicle charging infrastructure (EVCI) on electricity consumption and peak power demand in Russia's power system in the medium and long term. In contrast to existing research, the focus is not only on forecasting the number of EVs but also on a scenario-based analysis of a wide range of influencing factors.
METHODS. A mathematical model was developed to calculate the electricity consumption and maximum power demand of EVCI for all Russian cities with a population exceeding 50,000. The model accounts for the regional distribution of the EV fleet, its structure and model composition, climatic conditions, EVCI specifications, and behavioral factors. The significance of the factors was assessed using multiple linear regression.
RESULTS. It was found that for an EV fleet of 1 million units, the variation in influencing factors can lead to changes in EVCI electricity consumption ranging from 0.14% to 0.62%, and in peak power demand from 0.09% to 2.26% of the 2024 levels of Russia's Unified Energy System (UES). The EVCI parameters have the greatest impact on peak power demand: the number of EVs per charging station (37.1%) and the share of fast chargers (20.8%), along with the share of plug-in hybrid electric vehicles (23.7%). Electricity consumption is most significantly influenced by the share of plug-in hybrids (32.3%), their utilization rate (26.3%), and the share of electric buses in the fleet (21.6%). The forecast up to 2050 shows that EVCI electricity consumption could reach 8.13-11.85%, and peak power demand could reach 11.54- 16.81% of the 2024 levels.

THE PURPOSE of this work is to describe the cycling algorithms for fuel cell batteries with proton exchange membranes, which are suitable for use in regular operation in vehicles and during resource testing in laboratory conditions. To conduct a comprehensive assessment of the considered cycling algorithms and quantitatively evaluate the impact of internal processes on the duration of operation.
METHODS. To evaluate the proposed cycling algorithms, specialized software AVL Cruise M was used to create a digital 1D model of a fuel cell battery that describes the key processes occurring in fuel cells.
RESULTS. The article describes the mechanism of degradation processes that occur in fuel cells during their cyclic operation. A quantitative comparison was made of the results of applying two cycling algorithms based on the concentrations of platinum in the membrane, hydrogen peroxide, the specific electrochemical surface area of the catalytic layer, voltage reduction with each cycle, and other key indicators. The practical significance of the work lies in the detailed description of the two recommended fuel cell battery cycling algorithms: the first algorithm is applicable for the operation of fuel cell batteries in a vehicle, while the second is suitable for determining battery life. The latter algorithm will reduce the time spent on resource testing from 25,000 to 123 hours.
CONCLUSION. The results of the study showed that the main causes of increased degradation during cyclic operation are significant changes in the potentials on the catalytic layers of the fuel cells that make up the battery, as well as the diffusion of reagents, which can lead to the emergence of reverse current in certain areas of the fuel cells. When considering steady-state operation as the base process, it was found that in the first 50 hours of operation, there is a sharp decrease in voltage, which stabilizes only after 300 hours.

RELEVANCE. In this paper, the process of reverse electrodialysis (RED) using bipolar membranes is studied, aimed at converting the energy of the salinity and pH gradient into electrical energy.
THE PURPOSE was to study the effectiveness of this technology when working with model and industrial solutions, including regenerative waste from thermal power plants.
METHODS. During the experiments, key system parameters such as current density, specific power, internal resistance and efficiency were evaluated, as well as factors affecting plant performance were analyzed.
RESULTS. The results showed that bipolar RED allows not only to generate electricity, but also to produce acids and alkalis due to the dissociation of water in the membranes. The maximum achieved specific power was 3.5 W/m 2 at a current density of 12 A/m2 , and the energy efficiency exceeded 20%. At the same time, industrial solutions have demonstrated characteristics close to the model ones, which confirms the possibility of their use in real conditions. The scientific significance of the work lies in deepening the understanding of electrochemical processes in bipolar membranes and developing methods for optimizing the system. The practical value is associated with the creation of an environmentally friendly technology for waste disposal and simultaneous production of energy and chemical products.
CONCLUSION. The technology has potential for applications in water desalination, hydrogen energy, and the chemical industry, contributing to the transition to sustainable development. The study also revealed the main limitations, such as a narrow range of optimal operating parameters and energy losses due to parasitic processes. Further work should be aimed at increasing the selectivity of the membranes and reducing the internal resistance of the system. In general, bipolar RED represents a promising direction in renewable energy and resource conservation.

RELEVANCE of this study stems from the growing demands on the economic efficiency of thermal power plants (TPPs) operating in the balancing electricity market. Modern market mechanisms require high flexibility and precision in generation management, making prompt forecasting of the plant’s technical and economic indicators critically important.
THE PURPOSE. To develop a methodology for increasing the efficiency of CHP operation in a balancing electricity market by forecasting technical and economic indicators.
METHODS. We developed the algorithm by conducting a comprehensive analysis of long‑term operational data and applying the analogy method while accounting for equipment physical wear. This approach ensures high forecast accuracy – up to 0,53% – which significantly outperforms standard methods.
RESULTS. The practical implementation of our solution demonstrates a substantial reduction in financial losses: by 46-54% during night hours, when demand is minimal and electricity prices drop; by 29,2% when the plant operates at its technical minimum, constrained by stability and efficiency requirements. The annual economic benefit from applying this method reaches 109.1 million rubles.
CONCLUSION. We designed the research results for integration into systems that: manage TPP operating modes in real time; generate optimal price bids in the balancing market. This approach not only enhances the plant’s competitiveness but also promotes more efficient use of available resources. These benefits are particularly valuable under conditions of restricted new investments and the pressing need to improve energy efficiency.

PURPOSE. Determination of quantitative characteristics of nitrogen oxide emissions during combustion of gas mixtures containing hydrogen, carbon monoxide and methane.
RESULTS. Several types of gases with different chemical compositions and quantitative content of components were considered: CH₄; CO; H₂; 7 types of synthesis gas with different content of CH₄, CO, H₂, CO₂, N₂. These types of synthesis gas had low, medium and high values of heat of combustion. When performing numerical studies of the parameters and composition of combustion products, an approach based on the chemical equilibrium state of a multicomponent reacting mixture at a minimum value of isobaric-isothermal potential was used. The values of the main parameters of combustion products and estimates of nitrogen oxide emissions were obtained at different ratios of the initial components in the gas mixture and different values of the excess air coefficient. The values of the relative indicators of combustion product consumption correlate quite strongly with the values of the relative indicators of nitrogen oxide emissions.
CONCLUSION. Numerical estimates of the relationship between the combustion heat of generator gases, the flow characteristics of the combustion products determined by the composition of the initial gas mixture, and nitrogen oxide emissions are obtained. The quantitative indicator W_ps, determined by the ratio of the mass flow rates of the combustion products of the base fuel and alternative generator gas, under the condition of the same thermal power of the power plant, makes it possible to preliminary compare the expected level of NO_x emissions. At W_ps ≈ 1, the level of NO_x emissions for the compared fuel compositions is approximately the same. Accordingly, at values of this indicator greater or less than one, the levels of nitrogen oxide emissions during combustion of the alternative generator gas are higher or lower than during combustion of the base fuel. The practical use of the W_ps indicator is most effective at the stages of development and design of new power plants, including optimization of planning of computational and full-scale experiments, as well as during the transfer of operating power plants to alternative gas fuel.

THE PURPOSE of this paper is to analyze the efficiency of a seasonal UTES for heating a residential building and optimize its operational modes based on experimental data from 2022-2024. Addressing the seasonality of this energy source will increase energy generation and achieve net-zero carbon for energy-efficient buildings.
SIGNIFICANCE. For the first time, the actual operating modes of UTES in combination with flat-plate solar collectors have been experimentally assessed under conditions of a long cold period. The temperature limit for safe operation of the UTES with XPS thermal insulation (83.7°C) has been determined, which allows for increased design reliability. The data obtained has been used to adapt and refine mathematical models in TRNSYS, improving the accuracy of system operation prediction. Practical significance: achieving a reduction in energy consumption for heating and hot water supply of up to 42% compared to the baseline. Extension of the heating system operation period without turning on the heat pump – until December 20, 2024. Confirmation of the achievability of net-zero carbon for individual building. Potential application of the results in the design of energy-efficient buildings in cold climates.
METHODS. Experimental measurements of equipment temperatures and energy consumption in 2022-2024. Mathematical modeling of thermal processes: ANSYS Steady State Thermal – determination of the maximum safe temperature of the heating system. TRNSYS – forecasting system performance in winter.
RESULTS. The experimental and computational study enabled comprehensive analysis and evaluation of thermal energy production and consumption monitoring data The integrated heat pump and solar collector installation yielded substantial energy conservation: Electricity consumption for the heat supply system of building, thanks to the use of a heat pump and solar collectors, decreased from 4420 kWh in 2022 to 3050 kWh in 2023, i.e. by 31%, and in 2024 decreased to 2568 kWh, i.e. by 42%.
CONCLUSION. The use of a UTES and solar collectors for the heat supply system, in combination with photovoltaic panels and electric car charging, ensured the achievement net-zero carbon in 2023 and 2024.

RELEVANCE. The nozzle block is the important element of block burners, determining the efficiency and reliability of the burners. Most commercially available nozzle blocks incorporate a disk with swirl vanes to generate flow turbulence; however, such disks create significant gas-dynamic drag.
THE PURPOSE. To study the influence of combustible gas feed angles (angle to the axis β and chord angle α) on gas distribution across the cylinder cross-sections, the degree of flow swirl, and the degree of vacuum using forced air supply by an axial fan without the use of swirl disks.
METHODS. The study was performed numerically for isothermal jets and flow in the ANSYS Fluent software package using the SST k-ω turbulence model.
RESULTS. The minimum variation coefficient for all considered configurations was found to be achieved at a swirl number of about S=0.4-0.5. Vacuum pressure depends on the combination of angles β and α, the maximum was achieved at β = 90°/α = 15°. The swirl rate depends on both the swirl number S and the combination of angles β and α, with each angle β having its own range of S variation to maintain the maximum swirl rate.
CONCLUSION. A configuration (β = 90°/α = 26°) was found to achieve a compromise between a high swirl (S=0.58-0.48), an extended low-pressure zone (with a peak point of -433 Pa) and uniform gas distribution in the sections of the nozzle block: variation coefficient varied within the range from 41% (1 caliber from the inlet section) to 13% (outlet section). The results of the work are of practical value for the design of burner devices and further calculations using the combustion model.

RELEVANCE. Epoxy foams produced by thermal expansion of polymer microspheres show promise as sandwich panel cores. During secondary heating of epoxy foams, significant shrinkage or thermal expansion may occur, depending on the foam composition. Research and prediction of these processes is necessary for the design of sandwich products with epoxy foam cores.
THE PURPOSE. To study the thermal expansion and shrinkage of epoxy foams during secondary heating. To estimate the pressure created in a confined tooling space due to expansion.
METHODS. Dynamic mechanical analysis was used to estimate the glass transition temperature of epoxy foams. The foaming process of microspheres was studied using thermomechanical analysis. Thermal expansion and shrinkage were assessed by measuring the linear dimensions and volume of the foam before and after heat treatment. The pressure during the thermal expansion of foam plastics was assessed using pressure sensors and recorded using the DiamonPlus dielectric composite molding process monitoring system (INASCO).
RESULTS. It was shown that secondary heating of epoxy foam plastics can cause shrinkage or expansion of the material depending on the microsphere content. Thermal expansion pressure increases with increasing foam plastic density.
CONCLUSIONS. The temperature conditions for secondary heat treatment were selected, and thermal expansion studies were conducted for epoxy foam plastics with different microsphere contents and initial densities. It was shown that the initial minimum foam density decreases, while the density after heat treatment increases with increasing microsphere concentration. With an increase in the initial foam plastic density at a constant microsphere concentration, the foam plastic density after heat treatment decreases. For foam plastics with a high initial density and a high microsphere content, anisotropy of expansion and contraction after heat treatment is observed.

RELEVANCE. Due to the significant variety of configurations of heat exchange elements and designs of heat exchangers, coefficients of the criterion equation are proposed, which allows for a more accurate comparative evaluation of the efficiency of coil heat exchangers based on springtwisted channels.
THE PURPOSE. Carrying out calculations of coil heat exchangers of the "pipe in a pipe" type with a variable bending radius of a helical spiral based on spring-twisted channels and evaluating the energy efficiency of such devices in comparison with smooth-walled analogues.
OBJECT of this study is a conical apparatus with coaxially mounted coil tubes. In this case, the inner tube is made in the form of a spring-twisted channel of circular cross-section, and the outer one is made of smooth pipe.
METHODS. As part of the work, the engineering calculation of the conical coil apparatus has been adjusted, based on theoretical research and solving the related heat exchange problem, and includes the equations of the modified Ieshke correction factor, criterion equations for calculating heat exchange with heated (hot) and heated (cold) water, and the determination of heat transfer and heat transfer coefficients through the heat exchange surface.
RESULTS. In a coil heat exchanger with spring-wound pipes, the temperature of the heated coolant is 8.88°C (60.98°C versus 52.1°C) higher than in smooth-walled pipes. The thermal efficiency of such structures is higher: the power is 25.6 kW at a drop of 20.7°C versus 23.5 kW and 20.4°C, respectively. Heat transfer coefficient of spring-twisted pipes (1543 W/(m2·K)) higher due to turbulence and secondary flows. Hydrodynamic analysis shows a reduction in the cost of pumping heat carriers based on springtwisted channels to 1,438 Watts compared with 1,590 watts for smooth-walled structures. This is due to the shorter required length of the heat exchange element. The superiority of spring-twisted channels is confirmed by a higher value of the Kirpichev criterion (17,83) compared to smoothwalled analogues (14,77), which characterizes their improved energy performance.
CONCLUSION. Calculations of coil heat exchangers of the "pipe in a pipe" type with a variable bending radius of the spiral were carried out on the basis of two variants of heat exchange elements: a spring-twisted channel and a smooth pipe, the data obtained are consistent with the results of mathematical modeling. The results of the calculation confirm the technical and energy feasibility of replacing smooth tubes with spring-twisted tubes in the designs of heat exchangers. This modification makes it possible to simultaneously increase the thermal performance of the system and reduce the operational energy consumption for moving the coolant, which leads to a significant increase in the overall energy efficiency of the system. Thus, the use of spring-wound elements in heat exchangers is an innovative solution that improves the efficiency and reliability of heat exchange technology.