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ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations

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Vol 63, No 3 (2020)
View or download the full issue PDF (Russian)
https://doi.org/10.21122/1029-7448-2020-63-3

ELECTRICAL POWER ENGINEERING

212-222 1143
Abstract

In this article, the authors consider the possibility of using a hybrid energy storage system to even out the load profile of the enterprise. Solving the problem of rational use of energy storage taking into account the initial variable load schedule will significantly reduce not only the cost of electricity consumption by the enterprise, but also the costs of its production. Detailed characteristics  of  batteries  with  various  types  of  electrolytes  and  supercapacitors  are  given. A model of the active scheme of a hybrid electric energy storage system consisting of a lithium-ion battery and a supercapacitor unit with the corresponding characteristics is presented. The model was carried out by using the SimPowerSystems software in MatLab. During the simulation, the temperature and the aging effects and of the batteries were not taken into account. The selfdischarge parameter of the battery was also not presented. As a result of the simulation, discharge characteristics of supercapacitors and batteries were obtained based upon which the expediency of their combined use for leveling load profiles of various types was substantiated. The paper presents the results of the simulation of operating modes of a hybrid energy storage device, combining the advantages of two types of energy storage devices, as well as a diagram of delivered power to the network, corresponding to the specified parameters. The paper provides a mathematical description of the increasing power by hybrid storage system resulting from the combined use of supercapacitors and batteries. The paper presents the dependence of the power increase ratio on the frequency and the pulse current duty ratio, which proves that the maximum possible output power of the hybrid storage system can be several times greater than the power of a single battery having the same parameters.

НEAT POWER ENGINEERING

223-235 1719
Abstract

The article concerns the problem of structure-and-parametric optimization of a cascade automatic control system (CACS) by an example of a boiler power controller and a fuel controller. This CACS, which is a part of automatic control systems for power units, consists of two loops, viz. of an inner loop (which purpose is stabilization of the system) and an outer loop (designed for the adjustment) and, also, of two controller, viz. an outer controller (which is a basic one) provided for stabilization of the output value of the object (in our case, of the actual power unit capacity) and of an inner controller (which is an auxiliary one) provided to regulate fuel consumption. The internal controller builds up the control action with the aid of the boiler load controller of the power unit. As compared to single-loop automatic control systems, the cascade  system provides better quality of transient control due to the higher performance of the internal loop of the system. This advantage is especially noticeable when compensating for disturbances that come through the channel of regulating impact. The article presents two methods of setting, viz. the fuel controller and the boiler power controller. The application of these methods can improve the quality of power control and reduce fuel consumption in transient modes in comparison with the setting of these controllers of a typical power unit automatic power control system. The results of computer simulation of transient processes in CACS for input step surge and internal perturbation confirm the advantages of the methods are presented in this article.

236-252 732
Abstract

Direct flaring of industrial waste flows specifically in the combustion chambers of heat generating plants makes it possible to significantly reduce the loss of thermal energy, as well as the capital costs of equipping thermal units without using of preliminary furnaces. However, given the increasingly strict environmental standards for the burning of various fuels, it seems important to determine the optimal combustion conditions depending on the composition of the waste products. The article shows that only a complex solution can be a successful solution to the problem of organizing high-quality combustion of industrial waste flows. On the one hand, it is necessary to obtain extremely environmentally friendly combustion products, and, on the other hand, the waste disposal process should be energy efficient. The article discusses the stages of the implementation of the projects of energy-efficient utilization of industrial waste in compliance with the established environmental standards for emissions of pollutants. The analysis of initial combustible chemical substances that are part of solid, liquid and gaseous wastes of industrial technologies is given. The main classes of fuels that determine combustion reactions are identified. Global chemical reactions and oxidation mechanisms are considered. The combustible properties, chemical composition, and degree of impact of the products of combustion of industrial waste on the environment are determined, depending on the content of various starting substances. The most difficult aspect of the flaming disposal of industrial waste flows is the presence of harmful substances of various hazard classes. The conditions for achieving complete fuel combustion, stoichiometry, and equilibrium conditions for different air/fuel ratios (depending on fuel composition) with incomplete combustion are determined. The analysis of products of incomplete combustion is given as well as of and hazard classes of the corresponding pollutants. The maximum value of the coefficient φ was determined beyond which solid carbon should be formed in a homogeneous mixture.

253-263 719
Abstract

The kinetic model of wood pyrolysis under pressure is discussed in the present paper taking into account the diffusion of the resulting gas-phase products (i.e. heavy hydrocarbons) and their decomposition reactions. This model is based on a simplified mechanism of wood pyrolysis, including two parallel chemical reactions, viz. the primary decomposition reaction of  wood biomass with the formation of solid and gaseous components and the thermal decomposition reaction in the biomass pores of hydrocarbons formed in the primary process. The model takes into account the diffusion processes of the primary pyrolysis products from the resulting pores and thermal decomposition in the pores of these products. Based on the developed model, a computer program for calculating the main parameters of the pyrolysis process under pressure was created and the mass yield of solid pyrolysis products under various conditions was calculated. The calculation took into account the main parameters that affect the yield of solid wood biomass products, viz. temperature and pyrolysis pressure, particle sizes, porosity, etc. The calculations demonstrated that the increase of the pressure at which the pyrolysis of wood biomass is carried out causes an increase of the formation of the amount of solid products, which corresponds to the available experimental data. It was established that at a pressure of 1 atm when a sample size is of 0.025 m, the maximum yield of solid products is observed at the temperature of 600 °C. As the pressure increases the maximum yield increases, while the temperature at which the maximum is reached decreases. So, at a pressure of 10 atm when a particle size is of 0.025 m, the maximum yield of solid products is observed at the temperature of about 500 °C, and it is higher than that at 1 atm by 1.18 times. It was also determined that the temperature of the maximum yield of charcoal decreases with increasing sizes of pyrolyzable samples. Thus, when a sample size is of 0.5 m, this temperature is about 400 °C at 10 atm.

264-284 694
Abstract

An experimental facility has been developed and manufactured to study the disruptive flow in an air heat pump. The propeller of the heat pump does not produce pulling or pushing forces. The external air flow is created by a high speed propeller perpendicular to the plane of rotation of the heat pump propeller and acts as a ventilator. Herewith, a disruptive flow in the back side of the heat pump propeller is being created and conditions for converting the thermal component of the ventilator air flow into electrical energy by an electric power generator are realized. An aerodynamic model of the flow around the propeller blades of the heat pump in mutually perpendicular airflow has been developed. Experimental studies of the operating propeller as a heat pump, taking into account the friction during rotation of the rotor in the stator of the electric generator, were carried out. In order for the air heat pump to perceive the impacting air flow from the ventilator, it must rotate with minimal power. As a result, for two standard twin-bladed propellers mounted on a 100 W engine under the wind generated by the ventilator which speed is 2.17 m/s the conversion factor was 5.04. As the speed of air flow from the ventilator increased, the  conversion  coefficient  decreased  sharply.  When  placing  the  two  specified  propellers  on a 300 W motor, the minimum pre-rotation power was 5.7 W. In this case, when an air flow speed is of 1.08 m/s, the conversion coefficient reached only 2.93 and also fell sharply with the increase in the air flow speed. When a three-blade propeller with blades was used on a 300 W motor, then situation has changed dramatically. When the motor with a special propeller with a power of 12.1 W was spun and the air flow was formed at a speed of 3.2 m/s, the conversion coefficient was 12.4. With the reduction in the power of the spinup down to 5.9 W and in the speed of the air flow created by the ventilator to 1.7 m/s, the conversion coefficient increased to 14.9. The theoretical calculation of heat pump conversion coefficient is confirmed by experimental data. The conditions under which this coefficient reaches its maximum value are set. Computer modeling of different designs of heat pump propeller blades was performed. It is demonstrated that an air heat pump is a complex open energy system.

285-296 2750
Abstract

The current growth of energy consumption, which is directly related to the use of a large number of fossil fuels, and, as a result, causes environmental pollution, requires the search for ways to conserve energy and use traditional energy resources economically, as well as to preserve environmental well-being. In such a situation, a good solution to this problem can be the use of energy production technologies based on the use of non-traditional and renewable energy sources, and, in particular, the use of wind energy. In heat supply systems, wind energy can be involved in heat production technologies and then used for heating cities and towns. The method of heat supply of buildings through the use of a combined system of energy sources, consisting of a boiler house and wind power plants, is considered. The methodical basis of a very specific heat supplying system has been developed. The specificity of this system is that the boiler comes into operation, complementing the wind turbine operation, only if the wind is weak or absent at all. In other cases, the heat supply is provided by wind turbines, and the boiler house is waiting for the heating load. An assessment of the possible use of wind power facilities together with a boiler house in providing a heating load schedule for consumers located in an area with an increased potential of the wind which average annual speed is at the level of ~7 m/s is presented. The duration of the heating season in this area is 9–10 months a year. It is shown that the joint use of the boiler house and wind power plants for heat supply purposes during the year can reduce the share of the boiler house in the heat supply of consumers by 50–70 % or more.



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ISSN 1029-7448 (Print)
ISSN 2414-0341 (Online)