The output of power unit No 2 of the Belarusian NPP to the level of neutron power development of 100 % of the nominal level has changed the structure of generation of the Unified Energy System (UES) of Belarus. At the current loads of the inter-heating period of 2023, the share of a nuclear power plant with two power units operating at full capacity in the daily generation structure of the Republic is about 50 %. In order to balance the UES of Belarus during the operation of two power units of a nuclear power plant at night, the application of adjustment regulatory measures that exceed the available capabilities is required. The almost complete use of the adjusting range of the CHP will forcibly cause, on a larger scale, to the shutdown of the blocks during the load failures at night, followed by the start-up from the non-cooled and hot statuses. These operating modes of generating equipment are inevitable in the current conditions of the electricity market, which has led to the emergence of most complex tasks to assess the economic and technical efficiency of involving or another equipment of power plants in such modes. The paper proposes an approach to solving the problem of achieving an effective combination of reliability and efficiency of energy systems on the example of gas turbines and CCGT power units. A generalized desirability function has been obtained, which includes a number of parameters for choosing a rational relationship and mutual influence between the reliability and efficiency of electricity production with the participation of thermal power plant equipment in regulating the daily load schedule. The proposed mathematical model is an effective means of analyzing the suitability of equipment for use in the required operating modes.

At industrial CHP plants which are characterized, in particular, by steam supply to industrial consumers, in cases with significant condensate losses, it is proposed to develop a system of feed water regenerative heating by utilizing low-temperature waste heat flows those are available directly at the CHP plant. The regenerative use of low-temperature heat flows within the CHP that is proposed is possible only on the basis of heat pumps use. In this context, the use of electrically-driven heat pumps (EHP) and absorption heat pumps (AHP) is considered. It is shown that, despite the higher heating coefficient of the EHP, the thermodynamic (exergetic) efficiency and economic efficiency of the AHP are higher. Furthermore, the latter also has operational advantages. It is possible to use heat flows with various heat carriers as AHP drive, those are required for the transfer of thermal energy from a cold source to a hot receiver. In this paper, using the example of the “PT-60” steam turbogenerator unit, which is the most common type for CHP plants of the Belarusian power system, the indicators of the primary fuel use efficiency growth at the CHP plant for the AHP with a steam drive are determined. Three scenarios of the use of AHP as part of the thermal scheme of the CHP are considered, viz. with an increase in generation, with the maintenance of generation or with a decrease in the generation of electric energy. The latter is relevant in the current situation with the Unified Energy System of Belarus. In this case, while maintaining the minimum steam flow into the condenser of 12 t/h, the following increase in the plant efficiency has been obtained: electrical efficiency increased by 0.90 %, energy efficiency – by 0.55 %, and exergetic efficiency – by 0.23 %.

. Currently, there is a tendency to diversify the generation of heat and electricity and to improve solid fuel technologies. These trends actualize the search for mathematical tools for describing and predicting the operation of apparatuses with a fluidized bed of dispersed fuel materials. However, since the mechanics of heterogeneous media (and dispersed media in particular) is to a certain extent in its infancy in relation to the mathematical foundations of modeling, it is often difficult to predict the operation of equipment. In particular, the poor quality of mathematical basis does not allow predicting the fields of concentrations and velocities of the phases of the fluidized bed, although this knowledge serves as the fundamental basis for calculating heat and mass transfer and chemical processes. In the present work, a computational and experimental study of the local hydromechanical characteristics of a monodisperse fluidized bed has been carried out. The mathematical apparatus of the theory of Markov chains was used as a basis for modeling. The tasks were solved in a one-dimensional formulation, which implied the division of the bed in height into cells of small but finite sizes. Fluidized bed phase distributions were described by state vectors whose evolution was controlled by transition probability matrices. The elements of these matrices were matched to the physical parameters of the processes. The model was verified by comparing the calculated predictions with the data of a full-scale experiment conducted as part of the study, aimed at measuring the local velocities of the gas phase inside the fluidized bed. The experimental data with a good accuracy for engineering calculations were described by the proposed model, which makes it possible to consider it as a reliable scientific basis for the computer method for calculating installations using the fluidization technique.

. Currently, the transition to alternative fuel during the operation of thermal power plants (TPP) occurs due to the reduction and unreliability of coal supplies, deterioration of its quality, proposals for the use of cheaper fuel, tightening environmental requirements. Alternative fuel means such coal, for the use of which the boilers have not been designed during their design or reconstruction, as well as coal that has not previously undergone industrial or experimental combustion at this TPP. When converting boilers to alternative fuels, the main problems are: slag of the furnace shields and heating surfaces located above the furnace; fouling of convective heating surfaces; instability of non-designed fuel combustion; abrasion of the convective part of boilers; reduction of environmental performance; change in operating conditions of dust preparation, slag removal, ash collection and fuel supply systems. Before conducting experimental combustion of alternative fuels, it is advisable to carry out a preliminary assessment of its combustion possibility using numerical simulation, which makes it possible to identify emerging problems in advance. The most important factor in assessing the possibility of using alternative fuels is the influence of thermal performance, fuel and ash characteristics on the slagging of heating surfaces in the furnace. For a long time, the ability of ash to slagging was determined by the results of a fusibility test by changing the shape of a pyramid of ash particles during its gradual heating to various states according to the specific temperatures, viz. the initial deformation temperature, the softening temperature, the hemispherical temperature. The fusibility test cannot predict the real situation that occurs during the boiler operation. In addition, it does not allow ranking coals according to their tendency to slagging, which is necessary for the preliminary selection of alternative coal. Therefore, it is proposed to use the Watt - Fereday method with Bomkamp’s refinement for calculating the slagging index for ranking coals according to suitability as non-design fuels.

The paper discusses the circumstances and technical solutions that contribute to the integration of electrical and thermal networks of urban neighborhoods within the framework of a surplus of electricity generating capacities arising from the imbalance in the development of energy generation and consumption, stochastic processes of market economy development, the transfer of energy-intensive industrial production to other countries, the desire to diversify fuel energy resources, passion for the construction of energy sources for alternative energy resources in counterbalance to traditional energy facilities without taking into account all aspects of the interaction of the former with the environment, etc. With regard to district heating systems of electrical and thermal networks of urban neighborhoods, the use of hybrid heating points is achieved, which, unlike standard solutions, are equipped with electric boilers, thermal accumulators and heat pumps. According to the time of use of generating capacities, preference should be given to options for covering the hot-water load. Based on the average daily load, the power usage time in this case lies in the range of 6000–6500 hours / year. When choosing the capacity of the equipment, it should be borne in mind that the daily load of hot water supply is extremely uneven and also depends on the  day of the week, while the maximum load exceeds the average daily by 2.5 – 3.0 times. When integrating electricity and heat supply systems, it is advisable to consider options for only night-time electricity consumption or night-time consumption plus consumption during the hours of daytime failures of the electricity consumption schedule. If during the new construction the power of the electrical network may vary depending on the selected option, then during the modernization of the heat supply system, the problem is solved if there is a limitation on the available electrical power. Therefore, the definition of these restrictions is a separate issue. In comparison with the direct consumption of electricity for the needs of heat supply, which is a priori energetically and economically inefficient, the use of hybrid systems in heat supply allows us to solve the multifunctional task of increasing the reliability of energy supply and the stability of the functioning of the power system, which is primarily achieved by solving the problem of balancing the capacity of production and energy consumption from the position of aligning  schedules of energy generation and consumption.

The study involves scenario modeling based on the construction of energy chains that determine the flow of energy from the extraction and import of energy resources through technologies for transforming energy forms, transmission and distribution to the final consumer. A fundamental model of the energy system of the Republic of Belarus was also built. The principle of minimizing total system costs is chosen as the objective function for modeling, provided that a number of restrictions imposed on the power system are met. For the purpose of energy system balancing, it was proposed to use the potential of hydropower, viz. existing hydroelectric power plants for scenario 1 and technically possible potential for scenario 2. As a result of the modeling, the structure of electricity production was obtained according to two scenarios. Based on the resulting structure, the cost of producing electrical energy was determined. Two approaches were considered: approach 1 that took into account the cost of electricity production at nuclear power plants which can be classified as new, and approach 2 that took into account the cost of electricity production at nuclear power plants, which can be attributed to the existing generation. The production cost of electricity by 2030 is predicted. When approach 1 is used its level is of 63.3 US dollars/(MW·h) under scenario 2 versus 65.3 US dollars/(MW·h) under scenario 1; when approach 2 is used, its level is of 37.5 US dollars/(MW·h) versus 39.4 US dollars/(MW·h), respectively. Also, the economically feasible potential for using solar energy was determined, which by 2025 will amount to 0.91–1.45 billion kW·h/year, and by 2030 – 2.15–3.46 billion kWh/year; the same for wind energy is 1.55–2.39 billion kW·h/year and 3.69–5.67 billion kWh/year, respectively; the same for hydropower is 1.11–1.45 billion kW·h/year throughout the entire period under review until 2030. Based on the study, it became possible to find out that in the Republic of Belarus it is economically feasible and technically possible to replace up to 20.0 % of electrical energy generation by 2030 with energy produced from renewable energy sources.