IMPROVED CONTROL OF ENERGY CONSUMPTION BY A PHOTOVOLTAIC SYSTEM EQUIPPED WITH A STORAGE DEVICE TO MEET THE NEEDS OF A LOCAL FACILITY

As the share of green energy, including small (local facilities (LFs) with renewable sources), increases, there is an increasing number of issues related to ensuring the balance of energy both in the energy system in general and in local microgrids. This is primarily due to the mismatch between generation peaks and the peaks of consumption. That has led to new development trends and approaches to system design, including a reduction in green tariffs [1]. An effective, but expensive, solution is the use of storage devices. Also rational is the approach to using energy where it is generated, when LF (a small business object, cottage) takes on the role of the prosumer in the energy market system [2, 3]. The ability to shift consumption from peak hours to less active night and day periods, when there is a storage battery (SB) in the photovoltaic system (PVS), contributes to ensuring the balance of energy in the grid. However, the use of SB in PVS leads to an increase in the cost of the system, so the return on investment, along with the improved reliability of the electricity supply, is achieved by reducing costs. Thus, it is a relevant task to improve the management of energy consumption by PVS with a storage device in order to meet the LF needs while reducing the cost of electricity consumed from a distribution grid (DG).

The possibility of a comprehensive assessment of the efficiency of the operation of a district heating system based on the indicator of the overall efficiency of the equipment OEE (overall equipment efficiency) and its extension to the system as a whole is considered. The disunity of the direction of existing approaches in assessing the efficiency of operation of district heating systems does not allow a comprehensive assessment of the overall efficiency of the functioning of the technological sequence of the entire system.
It is proposed to consider efficiency as the probability of full functioning of all elements of the heat supply system.
It is shown that the heat output of the boiler house is proportional to the power consumption of the boiler house and is approximated by a periodic function.
It is shown that the main element of the heat supply system, which determines its efficiency, is the heat-generating source. As a result of the study, it is determined that the efficiency of the heatgenerating source functioning increases as the maximum value of its efficiency is reached.
Numerical modeling has shown that the flexible use of the installed heat generator capacity contributes to an increase in the efficiency factor from 0.53 to 0.70 and the overall efficiency of the heat supply system can be increased by more than 30 %. When designing a boiler house, it was recommended to provide for the installation of capacities with gradation 1; 0.5; 0. 25. It is shown that the OEE indicator allows one to characterize the efficiency of both the heat supply system as a whole and its individual components, and can be used in the design and analysis of the operation of systems.
Keywords: heat supply system, heat supply modes, central boiler houses, efficiency criterion, efficiency assessment. Development of the scheme of combined heating system using seasonal storage of heat from solar plants. Eastern Oleh Kislov National Aerospace University "Kharkiv Aviation Institute", Kharkiv, Ukraine ORCID: https://orcid.org/0000-0003-4814-9368

Mykhailo Shevchenko
National Aerospace University "Kharkiv Aviation Institute", Kharkiv, Ukraine ORCID: https://orcid.org/0000-0002-0806-6632 Determination of specific fuel consumption of air-breathing engines is one of the problems of modeling their performance. As a rule, the estimation error of the specific fuel consumption while calculating air-breathing engine performance is greater than that of thrust. In this work, this is substantiated by the estimation error of the fuel-air ratio, which weakly affects thrust but significantly affects the specific fuel consumption. The presence of a significant error in the fuel-air ratio is explained by the use of simplified methods, which use the dependence of enthalpy as a function of mixture temperature and composition without taking into account the effect of pressure. The developed method to improve the calculation accuracy of specific fuel consumption of air-breathing engines is based on the correction of the fuel-air ratio in the combustor, determined by the existing mathematical models. The correction of the fuel-air ratio is made using the dependences of enthalpy on mixture temperature, pressure and composition. The enthalpy of the mixture is calculated  through the average isobaric heat capacity obtained by integrating the isobaric heat capacity, depending on mixture temperature, pressure and composition. The calculation accuracy of the fuel-air ratio was verified by comparing it with the known experimental data on the combustion chamber of the General Electric CF6-80A engine (USA). The average calculation error of the fuel-air ratio does not exceed 3 %. The developed method was applied for correcting the specific fuel consumption for calculating the altitude-airspeed performance of the D436-148B turbofan engine (Ukraine), which made it possible to reduce the estimation error of the fuel-air ratio and specific fuel consumption to an average of 3 %. Keywords: fuel-air ratio, specific fuel consumption, combustor, isobaric heat capacity, air-breathing engine. This paper outlines the prospect of obtaining water from atmospheric air by cooling it to the dew point temperature using refrigeration machines in order to partially reduce water scarcity in the arid regions of our planet. To minimize energy costs in the systems for obtaining water from atmospheric air, it is proposed to utilize solar energy with absorption refrigeration units (ARUs) acting as a source of artificial cold.
The characteristic thermodynamic processes have been analyzed in a modernized ARU, capable of working at a lower thermal energy source's temperature than its analogs. The possibility has been studied to reduce the temperature of the heat source by including a solution vaporizer in the ARU scheme. The analysis involved an authentic method based on the balance of specific streams of ARU working body components and actual boundary conditions at characteristic points of the cycle. A limit was shown for the level of a minimum boiling temperature in the ARU generator (from 90 °C) when the systems for obtaining water from atmospheric air are operated under current climatic conditions.
The simulation of heat-and-mass exchange processes during contact interaction between a steam-gas mixture and ammonia water solution was carried out.
Based on variant calculations, it has been shown that the proposed ARU structure with an adiabatic solution vaporizer could work as part of systems to obtain water from atmospheric air at a hot spring temperature above 100 °C and constructively enough fits into the element base of standard models.
It has been proposed to use two types of solar thermal energy sources to operate ARU. In a tropical climate, with vacuum solar collectors or solar energy hubs; in a temperate climate zone, with solar collectors with water as a heat carrier.