Renewable energy sources (RES) are seen as a means of the fuel and energy complex carbon footprint reduction but the stochastic nature of generation complicates RES integration with electric power systems. Therefore, it is necessary to develop and improve methods for forecasting of the power plants generation using the energy of the sun, wind and water flows. One of the ways to improve the accuracy of forecast models is a deep analysis of meteorological conditions as the main factor affecting the power generation. In this paper, a method for adapting of forecast models to the meteorological conditions of photovoltaic stations operation based on machine learning algorithms was proposed and studied. In this case, unsupervised learning is first performed using the k-means method to form clusters. For this, it is also proposed to use studied the feature space dimensionality reduction algorithm to visualize and estimate the clustering accuracy. Then, for each cluster, its own machine learning model was trained for generation forecasting and the k-nearest neighbours algorithm was built to attribute the current conditions at the model operation stage to one of the formed clusters. The study was conducted on hourly meteorological data for the period from 1985 to 2021. A feature of the approach is the clustering of weather conditions on hourly rather than daily intervals. As a result, the mean absolute percentage error of forecasting is reduced significantly, depending on the prediction model used. For the best case, the error in forecasting of a photovoltaic plant generation an hour ahead was 9 %.

This article discusses the factors that affect the electrical resistance of the current spreading of the grounding device. The issue of the electrophysical parameters of the soil that affect its resistivity and the consideration of such parameters in the design of grounding devices is considered. It is shown that keeping moisture in the near-electrode space of the grounding electrode, as well as maintaining it at a certain level, facilitates improving the quality and reliability of the grounding. A relationship has been established between the ability to retain moisture and the magnitude of seasonal fluctuations in the electrical resistance of the soixl, and also the season factor, which takes into account changes under different climatic environmental conditions. The issues of application of various methods of reducing the resistivity of the soil during mounting of grounding devices are considered. One of the main ways to reduce ground resistance is the use of solutions of various mineral salts. This method is not optimal, as it accelerates the corrosion processes in the materials of the ground electrodes. Therefore, the paper also considers other ways to reduce the resistance of the ground loop; in particular, the authors propose a method for reducing the resistance of a grounding device based on the method of partial replacing the soil in the near-electrode region with a mixture with a lower resistivity capable of collecting moisture based on graphite and hydrogel. This type of mixture is environmentally friendly when used, as well as it is non-aggressive to the material of the ground loop. The principle of operation of this mixture is based on the fact that the hydrogel makes it possible to stabilize the moisture at the site of laying the circuit, while graphite increases the overall conductivity of the mixture. The paper presents the results of laboratory studies, which have been carried out in accordance with GOST 9.602–2016. For this purpose, control samples were placed in containers made of a non-conductive material (plexiglas) and dependence of resistivity on moisture, temperature, specific content of graphite and hydrogel was measured. The article presents graphs of the dependences of the mixture specific resistance on moisture, temperature, and the quantitative content of the hydrogel. From the results obtained, it can be concluded that the mixture in can be used in the energy sector to improve the reliability of electrical installations and ensure electrical safety.

A need in finding of new ways of energy saving at open switchgears of power plants is substantiated. In order to increase energy saving efficiency, an auxiliary breaker is suggested to be inserted between a transformer of a block and its two high-voltage circuit breakers. The reasonability of such an insertion is proved on the basis of comparing of calculations resultsof under-discharge of electricity (UE) by the tabular-logical method (Yu. B. Guk) of the obtained schemes and of the traditional ones. For the calculations, the conditions that arose due to the change in the main circuit of a power plant are studied. Also, equations are given for calculation of a decrease in UE, damage due to it during reconstruction, and costs for the construction of a power plant (the costs are assumed to be the same in all options). Russian statistical data and the predicted failure rate λEV of a 750 kV SF6 circuit breaker are used. An option of the introduction of an SF6 circuit breaker with and without replacement of other circuit breakers with SF6 circuit breakers is considered. The results of calculations of UE, damage, and costs for the introduction suggested are tabulated, where changes in them due to the introduction of the circuit breaker are estimated for 18 ring circuits and 17 “3/2” and “4/3” circuits of 330–750 kV switchgears at condensation, nuclear, and hydroelectric power plants. It is demonstrated that the presence of a generator breaker in the blocks makes it possible to reduce these energy-saving efficiency indicators several times. A technique for determining the failure rate of a hypothetical circuit breaker, which, in the case of traditional replacement, is capable of producing the same effect as an SF6 circuit breaker inserted is proposed. An example of determining this frequency is given. Results of the calculated reduction of UE, damage and costs for the case of an air circuit breaker having been substituted to an SF6 circuit breaker are presented.

A system with distributed parameters in its mechanical part is considered. Examples of such a system are given. The reason for taking into account the distribution of parameters in such systems is indicated. Existing methods of research and calculation of control systems are considered. The boundary value problem for a system with distributed parameters is presented. The use of a surveillance device as one of the ways to implement a control system for a system with distributed parameters is proposed. The necessity of using a closed control system and the complexity of its implementation are demonstrated. A block diagram of the control method being developed is presented. Also, transfer functions describing a system with distributed parameters are given; the mathematical calculation of the surveillance device is given as well. A method for implementing a closed control system along an intermediate coordinate for an electromechanical system with distributed parameters in the mechanical part using a surveillance device has been obtained. The surveillance device is in feedback and restores the output speed without measuring it directly. A general view of the transfer function is determined for the surveillance device. The advantages and disadvantages of the transfer function of the surveillance device and a graphical view of a simple implementation of the surveillance device with a dedicated auxiliary device in feedback are presented. An approximation that is used for systems with distributed parameters is described. Approximation conclusions are obtained. According to the parameters of the experimental installation, approximated transfer functions of the mechanical part of the system with distributed parameters without a surveillance device and with a surveillance device are obtained. The LACH of the mechanical part of the system with distributed parameters with a surveillance device and without a surveillance device for an experimental installation for the simplest case is presented, as well as a method for implementing a closed control system along an intermediate coordinate for an electromechanical system with distributed parameters in the mechanical part using a surveillance device.

Within the framework of the policy of “decarbonization” of the economy, a technology for hydrogen producing from local fuels (LF) and combustible waste of human activity is proposed as a part of the development of the functionality of heating cycles of energy production. The aim of the present study is to evaluate the energy efficiency of a steam-powered mini-CHP plant operating on local fuels with a thermochemical hydrogen production module. A brief literature review of thermochemical cycles of hydrogen production is presented, and it is shown that hybrid copper-chlorine Cu–Cl cycles are recognized as the most promising. In the Aspen Hysys software environment, a mathematical model of a mini-CHP plant with a five-stage hydrogen production cycle was synthesized, which can later be used as a component in the digital twin. According to the results of the analysis of the mathematical model, it was determined that the specific consumption of electric energy per 1 kg of hydrogen for such a scheme will be 9.11 (kW×h)/kg, which is on average more than five times less than in the production of hydrogen by electrolysis, the rest of the required energy is replaced by thermal one, while the maximum fuel utilization factor of mini-CHP with a hydrogen production module using wood waste as fuel amounted to 83.1 %, including a thermal efficiency of 51.5 %, the efficiency of hydrogen production at the lowest calorific value is 31 %, the electrical efficiency for the supply of electricity to the grid is 0.6 %. For comparison, the maximum fuel utilization of a steam-powered mini-CHP of the same electrical capacity reaches 90.9 %. The expansion of mini-CHP options operating on local fuels by introducing a hydrogen production unit by hybrid thermochemical method into its scheme makes it possible to increase the maneuverability of the station, which implies the possibility of organizing the operation of mini-CHP in accordance with the requirements of thermal consumers and electrical graph-reducing the loads of the power system during the hours of maxima and minima of its consumption by changing the electrical power supply to the network or increasing the power consumption of electricity from the external network to the power required for hydrogen production. In conclusion, the possibility of developing the studied scheme of a mini-CHP operating on local fuels towards further utilization of combustion products in order to generate artificial natural gas, which in this case can be called “green”, is indicated.

Currently, in a number of countries an urgent task for development of fuel and energy complexes is to increase the share of generation by involving solid fuels in circulation. Among such projects, those that allow the disposal of waste from various industries are particularly significant. Expired food products in this context are represented as a renewable local energy resource. However, such products require serious activities to prepare them for incineration or other type of high-temperature processing in order to obtain energy. The purpose of the present work is to improve methods of preparing fuel from recycled carrot fruits (unsuitable for use in the food sector). During the fuel preparation of carrots, the drying stage is limiting for the rational organization of its processing in boilers. In addition, the drying stage is extremely energy-consuming, so reliable prediction of its kinetics largely determines the efficiency of the entire technological process. In the course of the study, the following tasks were solved: a numerical method was developed for describing the processes of internal and external heat and mass transfer problems using an explicit difference approximation of differential equations of heat and mass transfer; parametric identification of the proposed one-dimensional mathematical model was performed using empirical dependencies known from literature sources; empirical verification of the proposed mathematical model was carried out by comparing the calculated forecasts obtained with the results of their own field experiments. The fact that the proposed mathematical model and the results of the full-scale experiment are independent, while the calculated forecasts and experimental data are in good agreement, makes us possible to consider the proposed calculation method as a reliable scientific basis for a computer method for calculating of heat and mass transfer processes when organizing the preparation of fuel from carrot fruits.

Schemes of polygeneration plants based on carbon dioxide are presented, in which the energy source are secondary energy resources and a gas turbine plant. These polygeneration schemes make it possible to simultaneously produce electricity, heat, cold, carbon dioxide in liquid and gaseous aggregate state, as well as to dispose of part of the carbon dioxide emitted into the atmosphere, due to its absorption from combustion products and use for commercial and technological purposes. The structure of the mathematical model of the program that has been developed for the exergetic analysis of polygeneration schemes is presented. With the help of the program, an exergetic analysis of polygeneration schemes was performed, in which polygeneration turbine units with different parameters of carbon dioxide in front of the turbine, as well as single and double overheating of carbon dioxide were compared. The exergetic electrical efficiency of polygeneration plants as a whole and its individual elements were taken as the criteria to be compared. Polygeneration plants with double overheating and supercritical parameters of carbon dioxide in front of the turbine have the greatest efficiency. A method for calculating of the economic indicators of polygeneration schemes is presented, which makes it possible to take into account the influence of double overheating and carbon dioxide parameters in the cost of a polygeneration plant. The economic efficiency indicators of various versions of polygeneration schemes, such as the internal rate of return, net discounted income, static and dynamic payback periods are obtained. It has been established that all variants of polygeneration schemes have acceptable indicators of economic efficiency, the static payback period of the proposed polygeneration schemes does not exceed 5 years, while the internal rate of return does not decrease by less than 22,8%.