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  Problemele energeticii regionale

E-Journal N2(54) 2022



1 Moisture Content and Aromatic Compounds Determination in Transformer Oil Using Spectral Method
Authors: Kozlov V.K., Kurakina O.E. Kazan State Power Engineering University, Kazan, Russian Federation
  Abstract: During operation, resulting from the thermochemical and electrical effects, the performance of the transformer oil decreases due to the measurement of the structural group composition. An increase in the content of the aromatic hydrocarbons leads to the appearance of a precipitate, and as well as due to its hygroscopicity, an increase in the moisture content. The latter is one of the transformer oil parameters that determines its quality. In power equipment, the presence of moisture of the order of 10 grams of water per ton of oil is allowed. At elevated water concen-trations, there is a risk of the power transformers’ failure. The aim of the work was to develop new methods for determining the aromatic compounds and water contents in the transformer oil in small quantities. This goal was achieved by conducting spectral studies of the transformer oil samples in the UV range and constructing correlation lines to determine the moisture content and concentration of aromatic compounds. The most significant result of the article was the estab-lishment of correlations between the optical density of the transformer oil in the region of 530 nm and the concentration of aromatic compounds and between the optical density in the region of 980 nm and moisture content in the oil. The significance of the obtained results lies in the fact that the optical method for determining the moisture content and aromatic hydrocarbons in transformer oils, using the constructed correlation lines, is highly accurate and does not require the use of additional reagents and complex calculations.
  Keywords: transformer oil, moisture content, aromatic compounds, absorption spectra.
2 Development of Low-Temperature Block Type Facility for Sea Water Desalination
Authors: Burdo O.G.1, Terziev S.G.2, Mordynskiy V.P.1, Sirotyuk I.V.1, Fateeva Ya.A.1, Molchanov M.Yu.1 1Odessa National Academy of Food Technologies, Odessa, Ukraine 2PRJSC “ENNI FOODS”, Odessa, Ukraine
  Abstract: This work is devoted to the fresh water deficit analysis. The importance of the research concern-ing water treatment is emphasized. A comparative analysis of water demineralization traditional methods is given and prospects for low-temperature desalination methods are shown. The in-crease in the world interest to the research of the block freezing innovative technologies was es-tablished, the priority in which belongs to the authors of this work. The aim of the work is to improve the block freezing devices during their transferring to a continuous operation mode. Achievement of this aim lies in a proposed universal design of the apparatus, in which the pro-cesses of crystallization, separation and melting of ice are sequentially implemented. A module for a continuous seawater desalination facility was developed. The energy and operational ad-vantages of the proposed method were described. The system modeling of this equipment was carried out. The target function of the modeling determined the key parameters of the process of the ice block gravitational separation — energy and salinity. It was proposed to correct the tradi-tional calculation principles for the outflow in channels by the “capillary drag” coefficient, which takes into account the relief surface of the ice capillaries. A technique for the engineering calculation of ice block salinity during separation was offered. The most significant result of the work lied in the fact of possibility to transfer the block freezing facilities to the continuous mode of sea water desalination with guaranteed salinity indicators. The significance of the work was that an energy-efficient freezing facility with ice recycling for the sea water demineralization in the flow was created.
  Keywords: heat and mass transfer, block freezing, separation, desalination, energy efficiency.
3 Medium-Term Hourly Electricity Tariff Forecasting Using Ensemble Models
Authors: Matrenin P.V., Arestova A.Yu., Antonenkov D.V. Novosibirsk State Technical University Novosibirsk, Russia
  Abstract: Forecasting electricity tariff rates is necessary for large suppliers, consumers, and power brokers working in the wholesale markets. Meanwhile, tariff rates of the retail market are also hourly changed for certain groups of electricity consumers. It creates more efficient electrical load regu-lation opportunities than the traditional load leveling approach. Power facilities that include con-trolled load consumers or local generation can use their capabilities by adjusting the load curve according to tariff rates. This work aims to study the potential for medium-term forecasting of retail electricity tariff rates and develop a predictive machine learning model. Hourly data on the retail market tariffs of the Novosibirsk region (Siberia) for four years were collected, several machine learning models were applied, and an analysis of the input parameters for forecasting was carried out. The most significant results are the proof of the possibility of obtaining the month ahead electricity tariff rate forecast with the mean absolute percentage error 4 %. It could be used for electricity costs reduction by regulating the load curve. It was shown that the discrete models based on ensembles of logical rules give higher accuracy than models based on continu-ous and piecewise continuous functions, such as neural networks. The significance of the ob-tained results is the proposed approach for month ahead electricity tariff rates forecasting, which was verified on a four-year dataset with an error of 4 %. The approach is based on open data and open-source machine learning models, which allow specialists with even a basic level of data science skills to put it into practice.
  Keywords: electricity market, medium-term forecasting, demand response, ensemble model, decision trees.
4 Design of Robust Decentralized Control Systems for Distillation Columns
Authors: Stopakevych A.O.1, Stopakevych O.A.2 1 National University of Intellectual Technologies and Communications 2 Odessа Polytechnic National University Odessa, Ukraine
  Abstract: This paper is devoted to the development of a decentralized control system design method with improved robustness, applicable to distillation columns control problem. The aim is attained by solving the following tasks: selection of representative models of columns; development of an effective transfer function identification algorithm; development of a decentralized controller design algorithm, which takes into account the cross-links impact; verification of the developed method for the selected models of columns. The most important result is the developed design method, which includes two algorithms. The first algorithm can be used to identify simplified models of the effective transfer functions. The second algorithm makes it possible to design a decentralized control system based on the ratio between the diagonals of the original model and effective transfer functions. Modified PI controller is used. The achievement of the distillation column control system robustness to the synchronous technologically conditioned deviation of the model parameters by up to three hundred percent of the nominal value is the paper signifi-cant result. The digital implementation of the designed controllers is simple. The analysis of the literature shows that none of the previously proposed methods for designing decentralized automatic control systems solved such a problem. The efficiency of the developed algorithms is illustrated using the known models of dynamics of distillation columns. The analysis of limita-tions of the method as well as its significant differences to the Biggest Log Tuning and H∞ loop shaping methods is presented.
  Keywords: robustness, distillation column, parametric uncertainty, MIMO, multivariable, coupled system, decentralized control system, effective transfer function.
5 Increasing the Energy Efficiency of Blast-Furnace Smelting by Choosing Rational Parameters for Loading a Multicomponent Charge
Authors: Ivancha N.G., Muraviova I.G., Vishniakov V.I., Shcherbachov V.R., Ermolina K.P. Iron and Steel Institute of Z.I.Nekrasov National Academy of Sciences of Ukraine Dnipro, Ukraine
  Abstract: The purpose of this study was to develop a calculation tool for researchers and technologists - metallurgists, providing the ability to quickly assess the distribution of charge materials in a blast furnace when it is loaded with a multicomponent charge. The goal is achieved by analyzing and summarizing the multidimensional matrix of values for the content of the charge components in the annular zones of the blast furnace, obtained using a mathematical model of its loading under various modes, changing the content of pellets in the charge and the moment the pellets are unloaded onto the main conveyor. The most important results of the studies carried out are the substantiation of the possibility of obtaining and applying calculated dependencies to determine the characteristics of the distribution of charge components with an accuracy acceptable for technological practice, as well as the established relationship between the content of the component in the charge and the value of the set point for the start of unloading it onto the conveyor with the content of this component in the annular zones of the top. Estimated composition of mixtures of charge materials formed in different zones of a blast furnace makes it possible to predict the properties of melts formed from them and to correct them in order to achieve the required level of energy efficiency in melting a multicomponent charge by promptly choosing rational parameters of the loading mode.
  Keywords: multicomponent charge, mixtures of iron ore materials, conveyor, distribution of components along the radius, calculated dependencies.
6 Influence of Wind Turbines on the Operating Modes of the Distribution Network
Authors: Lupu M., Zaitsev D., Tirsu M., Golub I. Institute of Power Engineering Chisinau, Republic of Moldova
  Abstract: The paper aim was to study the normal functioning modes of consumers power supply by the distribution network, taking into account the electricity production using wind turbines, as well as to develop recommendations that allow optimizing power consumption modes. The goal was achieved by analyzing the initial information on the network section topology, the technical characteristics of linear and transformer equipment, as well as consumption and generation profiles. The most significant result of the paper was the determination of the fact that the connection of wind turbines according to the “install and forget” principle without prior justification of both connection place and wind turbine capacity often leads to significant change in the operating characteristics and additional technical losses of active power. In this case, the main part of the losses falls on power lines. The significance of the obtained results lies in the fact that the main problems, associated with the coordination of the operating modes of distributed generation facilities and load, were identified and possible technical solutions were proposed to improve the situation. Based on the obtained results it is possible to conclude that when connecting a wind turbine to a distribution network, it is necessary to take into account both the capacity and the installation location of the equipment, which significantly change the values of the operating parameters of electrical networks. It has been shown that use of energy storage devices, as well as the network reconstruction, can make it possible to minimize active power losses and carry out balance of regimes.
  Keywords: operation mode of the distribution network, active power losses, distributed generation, wind turbines, electric energy storage devices.
7 Automatic Control of the Hybrid Heat Pump for Heating of Multi-Storey Buildings
Authors: Sit M.L., Juravliov A.A., Timchenko D.V. Institute of Power Engineering Kishinau, Republic of Moldova
  Abstract: The work is devoted to control systems for hybrid heat pumps using the heat of return network water and outside air, designed to operate in district heating systems based on CHPP. The aim of the research is to develop control systems for heat pump operating on qualitative, quantitative and quantitative-qualitative heat schedules. The set goal is achieved by introducing two con-trolled heat exchangers: one of "refrigerant-water" type, installed after the evaporator and "re-frigerant-air" type, installed after the gas cooler. The most important results are the hydraulic scheme of the heat pump, the control system scheme of gas superheater installed after the evap-orator and gas supercooler installed after the gas cooler. The significance of the obtained results consists in obtaining a technical solution, which ensures the operation of the heat pump at dif-ferent heating schedules. Equations of heat pump apparatuses have been obtained, in which the influence of flow rate and temperature of the working body on the heat pump operating mode is emphasized. The obtained heat balance equations allowed obtaining structures of automatic con-trol systems for heat exchange apparatuses, compressors and controlling valves of the hybrid heat pump. The developed scheme of the heat pump air duct allowed using a minimum of heat of return network water in the heat pump. It has been established that the scheme of this automatic con-trol system should include a functional converter linking the temperature of the outside air and the coordinates of the working body state at the outlet of the gas subcooler.
  Keywords: carbon dioxide heat pump, district heating, automatic control.
8 The Sufficient Condition for Ensuring the Reliability of Perception of the Steganographic Message in the Walsh-Hadamard Transform Domain
Authors: Kobozeva A.A., Sokolov A.V. Odessa Polytechnic National University, Odessa, Ukraine
  Abstract: In view of the high compatibility of the Walsh-Hadamard transform to the architecture of mod-ern computing facilities, it is sensible to use it in methods of steganography and steganalysis. Now, there are some efficient steganographic methods that use the Walsh-Hadamard transform domain for information embedding presented in the literature. It is known that to ensure the reli-ability of the steganographic message perception, information should be embedded in its high-frequency components; nevertheless, the issues of the correspondence of the Walsh-Hadamard transformants to the frequency components of the original matrix of the cover image are poorly researched. The purpose of this paper is to develop a formal sufficient condition for ensuring the reliability of perception of steganographic messages in the Walsh-Hadamard transform do-main. This purpose was achieved by establishing the relationship between the Walsh-Hadamard transformants and the discrete cosine transform transformants, which was theoretically substan-tiated in two ways, and also experimentally confirmed. Based on the established relationship between the Walsh-Hadamard transform and the discrete cosine transform, as well as the com-ponents of the singular value decomposition of the corresponding matrices, a sufficient condi-tion has been developed to ensure the reliability of the perception of steganographic messages in the Walsh-Hadamard transform domain. The sufficient condition consists in the fact that after embedding of additional information using any steganographic method, those Walsh-Hadamard transformants that correspond to the singular triples of the matrix corresponding to small (small-est) in value singular numbers, should change.
  Keywords: steganographic communication channel, steganographic message perception reliability, digital image, Walsh-Hadamard transform, sequence, discrete cosine transform, singular value decomposition of a matrix.
9 Anaerobic Digestion Combined with Electrolysis of Poultry Manure and Activated Sludge Inoculum
Authors: Chernysh Y.Yu.1,2,3, Shtepa V.N.2, Plyatsuk L.D.1,2, Chubur V.S.1,3, Danylov D.V.1 1Sumy State University Sumy, Ukraine 2International Innovation and Applied Center "Aquatic Arteria", Sumy, Ukraine 3Czech University of Life Sciences Prague, Prague, Czech Republic
  Abstract: The aim of the work was to study the effect of electrolysis on the process of anaerobic digestion in the example of poultry manure with an inoculum of activated sludge from a municipal wastewater treatment plant. The set aim was achieved by solving the following tasks: microcopiing of anaerobic activated sludge during the digestion of poultry manure under the influence of electrolysis treatment; studying the dynamics of biogas yield and its component composition under electrolysis treatment; studying the change in pH values and redox potential (ORP) in experiments with a combination of a bioreactor with electrolysis treatment and without treatment. Evaluation of the effect of stimulating the metabolic activity of microorganisms during treatment in the bioreactor-electrolyser was the most significant result. In addition, improved biodegradability of complex organic components of poultry manure was substantiated. Thus, methane yield on the 28th day was 640.5 ml from the total volume of 1525 ml of biogas, and under conventional conditions, methane yield was 33.4 ml from 50 ml of total volume. The decrease of H2S content in biogas under the influence of electrolysis was determined. A low ORP value of - 495 mV was achieved in the control experiment (without electrolysis treatment). ORP gradually increased in the bioreactor-electrolyser at all stages of digestion and reached -53 mV on day 28. pH stabilized at a neutral level. The positive effect of combining anaerobic digestion with electrolysis on the intensification of biogas production with a large volume of methane has been experimentally confirmed.
  Keywords: biogas, electrolysis, anaerobic digestion, activated sludge, manure, intensification.
10 Fluidized Bed Seed Dewatering System
Authors: 1Tirșu M.S., 2Popescu V.S., 2Balan M.M., 2Kurdov I.S., 2Balan T.V., 2Rotari V.V. 1Institue of Power Engineering 2State Agrarian University of Moldova Kishinau, Republic of Moldova
  Abstract: The aim of this work is to improve the efficiency of the dehydration process of seeds of agricultural plants by applying the fluidized bed treatment method. In order to achieve the aim of the work, an experimental plant for the dehydration of seeds in fluidized layer was developed, based on which the research was carried out. Convection and SHF were used as sources of fluidized bed seed treatment. The efficiency of the dehydration process with the application of the developed experimental plant was estimated for 3 types of seeds of agricultural alleaginous plants: grape seeds, flax seeds and white buckthorn seeds. These types of seeds were selected for research because at present their dehydration is a problem and they have a great potential for the food industry, traditional medicine, cosmetic industry, pharmaceutical industry, etc. The main results obtained in the application of the developed plant to the treatment of seeds of agricultural plants in a fluidized layer are: increase of the dehydration process speed, reduction of the treatment time, reduction of electricity consumption, increase of the seed quality and reduction of the processing costs. Again, the plant is simple in terms of construction, easy to use, low in cost and during operation has demonstrated a high level of operational safety. The significance of the results obtained lies in the efficiency of the process of dehydration of oilseeds of agricultural plants, based on fluidized bed treatment, mainly with a reduction in the cost of technological processing and an increase in the quality of these seeds, for subsequent use in the food industry, traditional medicine, cosmetics industry, pharmaceutical industry, etc.
  Keywords: seed dehydration, treatment method, experimental plant, fluidized bed.
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