POWER ENGINEERING: economics, technique, ecology

DETERMINATION OF THE TEMPERATURE FIELD DISTRIBUTION IN THE WINDING RODS OF THE STATOR OF TURBOGENERATORS OF TYPE TVV FOR PURPOSES OF CONTROL AND DIAGNOSTICS

2023-01-14T18:15:40+02:00

Turbogenerators were and remain the most unreliable element at nuclear power plants in Ukraine. The most dangerous disturbances in the operation of turbogenerators of the TVV type is complete or partial blockage of the hollow conductors of the stator winding. The systems of operational control and technical diagnostics today, in a number of cases, cannot cope with the identification of these phenomena. The complex application of adequate mathematical models, indications of the standard thermal control system and new diagnostic features give the opportunity with sufficient accuracy for practical purposes to detect blockages in the hollow conductors of the stator windings of these turbogenerators. The aim of the work is to develop a program for calculating the three-dimensional temperature field in the rods of the stator winding of a turbogenerator of the TVV-1000-2U3 type, taking into account the temperature field of the stator core, to carry out a test calculation and to compare the experimental and to calculated data. The problem is solved with the help of the finite difference method using the integro-interpolation method.

MODERN TECHNOLOGIES FOR INCREASING THE ENERGY AND ENVIRONMENTAL EFFICIENCY OF ENERGY PRODUCTION

2023-01-14T18:40:29+02:00

The problems of energy efficiency of energy production along with improving the environmental safety of enterprises are becoming increasingly relevant. One of the ways to solve these problems is the implemention of effective technologies, which include microflare incineration technology (MIT-technology) of gaseous fuels. The use of MIT- technology, in addition to a significant reduction in harmful emissions into the atmosphere, can simultaneously increase the energy efficiency of thermal power plants.

A significant positive effect can also be achieved by using contact energy exchange plants. A striking example of such a gas-steam plant “Aquarius” the operation of which exceeds the efficiency of gas turbine plants by 10-12% with a simultaneous significant decrease in the concentration of toxic nitrogen oxides NO_x and carbon monoxide CO in flue gases.

TECHNOLOGICAL ENERGY CAPACITY OF COMBINED CYCLES OF STEAM GAS STATIONS

2023-01-15T18:13:50+02:00

Offers a means of increasing the efficiency of the cycle by reducing par asitic loads such as the excess air compressor load and of capturing energy that might otherwise be wasted. However, this is not always the most effective way of increasing overall efficiency of energy conver sion. For large gas turbine based plants in particular, the best way of improving efficiency is to add a steam turbine bottoming cycle, creat ing a combined cycle power plan. A combined cycle plant is simply what its name suggests. Instead of relying on a single thermodynamic cycle to convert energy into electricity the plant uses more than one. These piggy-back one another with the first cycle using the highest temperature thermodynamic working fluid, followed by a second using the intermediate temperature fluid . In fact combined cycle plants with more than two cycles are not used commercially although they are theoretically possible. Much more significant for the modern power generation industry is the addition of a bottoming cycle to a gas turbine power plant. In this case the bottoming cycle is usually a steam turbine cycle, with heat from the gas turbine exhaust exploited to raise steam. This is the most common combined cycle power plant. It would be possible to add a third cycle to exploit the low grade heat remaining after steam generation. This could be achieved with a closed cycle turbine such as an organic Rankine cycle. Such turbines can exploit low grade heat to produce electricity and are used in some geothermal plants where the temperature of the geothermal reservoir is relatively low. However, it is unlikely to be economically viable to add this third cycle to a modern combined cycle plant. To determine the technological energy intensity of such stations, the whole cycle of energy production was considered. The main characteristics of combined cycles are given and the technological energy intensity of energy supply is calculated. The main advantages and disadvantages of these installations are given, and also the comparison of steam turbine and steam and gas stations is made with definition of possible potential at replacement.

RELAP5-CFX COUPLING MODULE: TESTING ON SIMPLE THERMOHYDRAULIC MODELS

2023-01-15T18:22:11+02:00

The modern direction in the study of the safety of nuclear power plants is to ensure the maximum level of detail in process modeling with a satisfactory level of computational resources. One of the approaches of such task solving is the coupled use of special software with the required levels of detail, for example, systemic thermohydraulic codes with computational hydrodynamics codes.

This article describes the developed coupling module between the system thermohydraulic code RELAP5/Mod. 3.2 and the CFX computational hydrodynamics code, using an external explicit interfacing scheme without overlap, in which CFX acts as the main code and RELAP5 as the secondary one. The development of this module is part of the work on integrated coupled modeling of severe accidents and makes it possible to model the defining processes and phenomena that occur during a severe accident within the reactor vessel using the CFD model, and the elements of the reactor unit using the RELAP5 model with an acceptable cost of resources and with a high level of detail. To check the coupling technology, the module was tested on simplified models containing serially connected RELAP5- and CFD-models of horizontal pipes, as well as on a closed loop. In view of the further use of the interface module on a full-fledged model of the VVER-1000, testing is performed for three main interface types: "input flow", "output flow" and their combination "input/output flow" on a closed loop. After completion of the testing, the accuracy and credibility of the results of the coupled calculations was evaluated by comparing them with the results of autonomous RELAP5 calculations. Results of the tests calculations support the possibility of using the RELAP5-CFX coupling module on more complex and large-scale RELAP5 and CFD models.

EVALUATION OF ENERGY CONSUMPTION OF DRILLING TOOLS WHEN DRILLING WELLS ON KARSTED ROCK BLOCKS

2023-01-09T21:35:42+02:00

The article is devoted to the analysis of energy consumption in the process of drilling wells in karst rock blocks. The paper presents the results of experimental and analytical studies of the drilling process and energy consumption for the destruction of rock massifs with a complex structure characterized by the presence of karst cavities. The operation of the drilling machine during the drilling of the karst rock block was monitored. In the article, the use of the criterion of energy intensity of the well drilling process is proposed to assess the level of energy consumption by the drilling rig. On the basis of the conducted research, the dependence of the rotary power of the drilling machine on the productivity of drilling wells was established, and the dependence of the specific energy intensity of rock drilling on the drilling productivity was determined.

The results of the conducted analytical and experimental studies on the determination of the geological structures of well columns by the energy intensity of their drilling process allow the development of designs of well charges for effective and safe destruction of complex rock massifs.

MODELING AND ANALYZING THE EFFECT OF CONNECTION TO THE NETWORK OF A HARMONIC SOURCE HAVING VARIOUS TOTAL HARMONIC DISTORTION FACTORS ON LOAD SIGNAL WAVEFORMS

2023-01-10T12:09:15+02:00

This article examines the effect of a network connected source of harmonics having a total harmonic distortion factor varying from 5% to 15% on load voltage and current waveforms. When a source of higher harmonics is connected to the network, both in the network and in the load, the effective values of voltage and current increase, that can negatively affect the cable line insulation, accelerating its destruction and aging.

To analyze the consequences of a power quality deterioration, a 20 kV network was simulated, consisting of a 20 kV symmetrical generator, an XRUHAKXS-20(1x120/50) power cable line 20 km long, a step-down transformer 20/0.4 kV with a power of 2 MVA, with windings connected in delta-star, and a three-phase symmetrical load.

The values of the currents flowing through the cable conductor, obtained as the result of simulation were used to calculate the voltage drop between the cable conductor and its shield. Results obtained show that the connection of a harmonic distortion source to a network leads to a magnification of a current flowing through the cable conductor by more than 2%. The model proposed in the article can be used further for a more detailed study of solar photovoltaic plants connection to the grid.

One of the biggest problems regarding solar power plants is that its electricity generation is intermittent. Thus, future efforts should be focused on modeling and studying the higher harmonics generation during switching on and off of the solar photovoltaic plants.

COMPRESSING AIR IN A TANK PARTIALLY FILLED FROZEN WATER AND ITS USE TO DRAIN WATER FROM SOLAR COLLECTORS

2023-01-14T18:03:24+02:00

The use of the effect of increasing the volume of ice when freezing water to compress the air in a tank partially filled with water is considered. The aim of the study is to create conditions for the movement of the ice surface and determine the final air pressure after freezing water. A method of air compression has been developed and theoretical and experimental studies of the final air pressure have been performed. Experimental tests of a patented method of air compression with the provision of a movable ice surface by applying thermal insulation to the air chamber at the top of the tank were carried out. For this purpose, two air compressors of different sizes are made using cold air and a mixture of ice and salt. Obtained excess air pressures from 0.3 to 0.5 bar. The thermodynamic analysis of the process is carried out. The equation for determining the pressure at complete freezing of water, with a constant cross-section of the air compressor is obtained. Compression calculations are close to experimental data. Studies have shown the real technical possibility of air compression when water freezes in a rigid sealed tank and its use for automatic drainage of water from solar panels at the onset of frost. 1. The proposed and experimentally investigated method of ensuring the movement of the ice surface relative to the walls of the tank when compression of the air in the tank, by thermal insulation of the airspace. Obtained thermodynamic analysis of the equation for the final pressure of the air compressed by ice. When using a tank with a constant horizontal section, the final pressure does not depend on the area of the cross section and increases with increasing water level. The experiments on two installations showed that excess pressure reaches 0.3 - 0.5 bar. Freezing water tank is proposed to be used as a temperature sensor, and compressed air can drive a direct action valve. Calculations of water freezing time for compression of the air showed its significant reduction with the growth of the tank coefficient.

ANALYSIS OF APPROACHES TO DETERMINING THE QUANTITY OF THERMAL ENERGY FOR THE NEEDS OF HOT WATER SUPPLY IN THE ENERGY CERTIFICATION OF BUILDINGS

2022-12-25T22:00:32+02:00

In Ukraine, at the legislative level, as part of the implementation of EU Directives, mandatory energy certification has been introduced for certain types of new and reconstructed buildings. In addition, in order to receive financing from various investment funds and the possibility of participating in state or local thermomodernization programs, it is necessary to perform their energy audit and justify energy-saving measures, assess the energy efficiency class. In Ukraine, there is a complex of regulatory acts, methodical documents, construction norms and standards in the field of energy certification, which is constantly updated. The national methodology for calculating energy efficiency indicators has been passed and the by-laws have changed several times, in particular, in the part of accounting for energy consumption for hot water supply, which in turn affected the energy efficiency class. The article evaluates the influence of different approaches to the calculation and accounting of additional revenues from hot water pipelines on the example of a residential multi-story building in Kyiv. As part of the research, a detailed energy survey was carried out using instrumental and analytical methods, the geometric, thermal and energy characteristics of the building were specified, and a set of measures to increase the level of energy efficiency was proposed. As part of the research, a detailed energy survey was carried out using instrumental and analytical methods, a calculation model was formed and a series of calculations was performed. The impact on the specific energy demand, total energy consumption and energy efficiency class of the existing building of changes in the regulatory framework, the features of taking into account utilized heat losses, the number of consumers is shown.

EVALUATION CRITERIA OF INSTALLED TRANSFORMER POWER AT DISTRIBUTION SUBSTATIONS OF ELECTRICAL NETWORKS

2022-12-25T22:13:18+02:00

This work is devoted to approaches to determining and substantiating the optimal power value of transformers that installed at distribution substations. During the selection of the transformer under working the electrical load schedule of consumers of distribution substation in the power grid, it is necessary to ensure in full using of every unit of installed transformer capacity. For example, there are three transformers that belongs to the 10 kV, 35 kV and 110 kV voltage levels. It is shown the calculation of the optimal value of the transformer power and the selection of this power is performed, based on the nomenclature of transformers. It was carried out a technical and economic comparison of possible combinations in number and capacity of transformers to set the optimal power level.

Active energy losses, profit from the transporting of active energy and the total discounted costs function are the estimation of the installed transformer capacity. The transformers chosen for installation at the substation of the power grid are estimated for the ability to work at the highest ambient temperature level of +40°С, based on the temperature of the hot-spot point on the surface of the insulation of the windings.

This work ends by conclusion in comparison of the results of two approaches to estimating the lifetime and residual operation life - when the hot-spot point is in stationary and when it moves during electric load changes.

THE COMPREHENSIVE EDUCATION OF ELECTRICAL ENGINEERING AT THE POWER SUPPLY DEPARTMENT OF IGOR SIKORSKY KYIV POLYTECHNIC INSTITUTE

2023-01-09T18:59:48+02:00

The concept of the "green" energy transition involves, first of all, the transformation of views on the development of energy, in particular, the electric power industry in the context of its greening and decarbonization, with special attention to the problems of combating climate change within the framework of the sustainable development paradigm. Such a transformation requires the education of high-quality electrical enguneers, who are aware of the new role and place of the consumer in the liberalized electricity markets within the Smart Grid concept. End-to-end three-level training at the Department of Power Supply of Igor Sikorsky Kyiv Polytechnic Institute bachelors, masters (professional and scientists) and Ph.D. during the 25 years under the educational and professional programs "Systems for providing consumers with electrical energy" and "Energy management and energy-efficient technologies" specialty 141 "Electric power engineering, electrical engineering and electromechanics" in the field of knowledge 14 "Electrical engineering" made it possible to provide industrial, energy, communal, commercial and other companies and organizations, as well as authorities and local self-governments of Ukraine with qualified specialists in the power supply of the built environment, industrial enterprises and agricultural objects and energy managers, capable of jointly solving complex the task of reliable electricity supply to consumers with high-quality electrical energy with the introduction of energy-efficient technologies, reduction of the use of fossil fuels and reduction of harmful emissions on the basis of sustainable development.

DETERMINATION OF ELECTRICAL LOSSES BASED ON NODAL ELECTRICAL LOAD FORECASTS

2023-01-09T19:16:49+02:00

This study proposed the use of forecasting methods based on artificial neural networks for calculating and forecasting energy losses. The calculation of energy losses was performed on the CIGRE test network. Several approaches were developed to determine energy losses: prediction of electrical energy losses using artificial neural networks, and calculation of losses using nodal load prediction based on artificial neural networks, which were compared with the classical method of calculating losses based on summer and winter peak load coefficients. Depending on forecasting problems, when using artificial neural networks, the amount of electrical energy losses in distribution networks decreased by three times compared to the calculation of losses using coefficients.

FEATURES OF ORGANIZATION AND USE OF ENERGY STORAGE SYSTEMS IN DISTRIBUTION NETWORKS

2023-01-09T21:08:40+02:00

The article analyzes the features and formulates recommendations for the most effective use of the energy storage systems in electrical distribution systems and microgrids in the context of expanding the use of local renewable energy sources. Information about various energy storage technologies is summarized and recommendations are formulated regarding their best applying for various applications in the electric power industry. The tasks that can and should be solved by energy storage systems in distribution networks are considered, as a result of which the expediency of forming hybrid storage systems is substantiated. Based on the analysis of the bibliography and consideration of international experience, the main problems have been identified that require further research for a reasonable choice of the structure, parameters, locations and modes of operation of hybrid energy storage systems, taking into account the specifics of the structure and operation of domestic electric distribution systems with local energy sources. Under the implementation of hybrid energy storage systems, a fundamentally new problem of determining the optimal parameters of individual components of such systems arises, which was practically not covered in published works on this issue. Additionally, difficulty in solving this task is the need for its complex solution, since, firstly, the parameters of the individual components of the hybrid energy storage system are most likely interdependent, and secondly, it is necessary to take into account the involvement of the storage systems in the solution of a number of optimization problems inherent in the electrical distribution systems. In order to facilitate the use of energy storage devices, it is advisable to create a comprehensive standard that allows you to evaluate and compare the quality and performance of different technologies, helps energy storage users justify the type and parameters, as well as optimal placement for maximum benefit.

AGGREGATION PRICE MODELS FOR MICROGRIDS WITH DISTRIBUTED ENERGY RESOURCES

2022-12-25T20:45:35+02:00

The development of Microgrid states the problem of choosing the optimal technologies for its composition.
This paper is to present cost based demand-side management methods for the Microgrids with Distributed
Generation sources to optimize their operation. While implementing variable pricing models the aggregator
should take into account characteristics of different Distributed Energy Resources (DER) (diesel engines, gas
turbines, fuel cells, solar panels, small hydropower plants and wind turbines) and LCOE for each type of DER to
stimulate each local electricity market participant separately. The system Microgrid using three diesel generators
and the option of replacing one generator with a solar electric and wind generator installation was considered.

ACCIDENT LESSONS AT THE FUKUSHIMA-DAIICHI NPP FOR THE SAFETY OF THE NUCLEAR POWER INDUSTRY IN UKRAINE

2023-01-15T18:38:20+02:00

The main causes of destructive steam and gas explosions with catastrophic environmental consequences during the accidents at Fukushima-Daiichi NPP were the loss of tightness of the passive safety systems of the reactor residual fuel removal safety system and the critical residual heat removal function in the spent nuclear fuel holding tank . The main lesson of the Fukushima accident for the environmental safety of Ukraine's nuclear power industry is the need to anticipate the possibility of unlikely emergency events with catastrophic environmental consequences. Such unlikely events include: flooding of the nuclear power plant site, complete long-term blackout, steam-gas destructive explosions, joint action of external extreme phenomena. Based on this, the following lessons of the Fukushima accident were formulated for the nuclear power industry of Ukraine regarding unlikely emergency events with catastrophic environmental consequences: lesson 1 - the need for reliable isolation of diesel generator rooms from external extreme events; lesson 2 - the need to improve strategies and methods of managing accidents with complete long-term blackout and lesson 3 - the need to determine the conditions of steam-gas explosions. The lessons of the Fukushima accident and the known results of the analysis of explosive conditions in nuclear power plants with WWER determine the need to improve methods for modeling the conditions and consequences of steam and gas explosions at the dynamic stages of emergency processes.The lessons of the Fukushima accident and the results of the calculated modeling of accidents with complete long-term power outages of nuclear power plants with WWER determine the need to improve strategies and ways to prevent and manage accidents with complete long-term power outages.A promising approach is the integrated use of additional passive safety systems to ensure the function of feeding steam generators with turbopumps (area for high pressures) and natural circulation (area for low pressures).

METHOD OF IDENTIFYING HAZARDS AND PREDICTING THE EMERGENCY SITUATIONS IN CASE OF SOIL CONTAMINATION BY HEAVY METAL COMPOUNDS

2023-01-15T19:26:39+02:00

Purpose. The goal of the article is to develop a method for identifying hazards and predicting the possibility of a technogenic emergency caused by the spread of compounds with heavy metals in the soil during long-term storage of galvanic sludge in open areas.

Methodology. The method is developed on the basis of a mathematical model that allows estimating changes in the depth of distribution and level of soil salinity over time using initial information about soil structure and its characteristics (molecular diffusion coefficient, volume humidity), annual volumes and conditions of sludge storage in the enterprise. Restrictions are set: the presence of harmful substances on the soil surface with a concentration that exceeds the permissible level; inadmissibility of harmful substances to aquifers.

Results. The practical use of the method made it possible to identify the main dangers and predict the possibility of an emergency situation with negative environmental consequences during long-term storage of galvanic waste in open areas. The dynamics of soil salinity levels and the depth of penetration of heavy metals increase over twenty years of conservation has been determined, as well as the possibility of hazardous compounds entering groundwater has been assessed.

Originality. The non-linear, non-stationary mathematical model is based on the theory of physico-chemical hydrodynamics of cellular media. The process of motion of metal salts has been described by the differential equation of motion and conservation of mass of matter for vertical mass transfer of matter.

Practical value. Formalization of information about the hazards arising during the storage of industrial waste with chemically active elements allows to consider the subject area as a complex dynamic system consisting of objects of different nature, the totality of which determines the level of danger of emergencies with environmental consequences. The developed method makes it possible to transfer the obtained results to decision-making support systems, predicting possible consequences and material costs associated with post-emergency measures, motivating the management to take measures in advance.