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ELECTROENERETICS
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Mode of Operation of the Republic of Moldova Power System with Back-to-Back Installation at the Substation Vulcanesti
Authors: Postolaty V., Berzan V., Bykova Elena, Andronaty N. Institute of Power Engineering of the Academy of Science of Moldova Chisinau, Republic of Moldova
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Abstract: The results of analysis of the operating mode of power system of the Republic Moldova with the interconnection with the power system of Romania using the Back-to-Back (BtB) power unit at the transformer station Vulcanesti have been presented in the paper. Installation of BtB leads to the loading of overhead power line (OPL) 330kV Vulcanesti-Chisinau up to 571 MW with the change of the value and the direction of power flux in OPL from Chisinau toward Kuchurgan power station, the decrease of power flux entering the north of the country (OPL 330kV HPP Dnestrovsk - Balti) and in the OPL 330kV (Kotovsk- Kuchurgan power station). Essential changes of the active power flux occur at the buses of Kuchurgan power station toward Ukraine in comparison with the actual topology of power network (base regime). The change of the direction and of values of power flux through the unified power system has as a consequence the increase by 171MW (from 2961MW to 3132MW), as well as the increase by 7,1% of the losses of power in high voltage Moldovan network comparing with the base regime. It is pointed that the accomplishment of asynchronous interconnection with Romania has the impact at regional scale causing the change of power fluxes both in the power system of the Republic of Moldova and of Ukraine with Romania including the Kuchurgan power station. Assessment of financial aspects indicates to the trend of increasing of the project’s cost of the interconnection with Romania, but in the case of investment return considering the increase of the cost for the service of transmission of power is expected the necessity to increase the tariff with nearly 154% in comparison with the value of 2015 year, considering zero value of bank and inflation rates during the 10 years of investment return, as well as the constant exchange rate of MDL to EURO during the 10 years investment return period. |
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Keywords: interconnection, power system, distribution, power flux, active power losses, tariff.
DOI: https://doi.org/10.5281/zenodo.1207864
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Calculation of the Magnetic Fields of the Electric Power Line
Authors: PATSIUK V., BERZAN V., RYBACOVA G. Institute of Power Engineering of the Academy of Science of Moldova Chisinau, Republic of Moldova
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Abstract: The task of calculation of per unit length parameters of multi-conductor electrical overhead transmission lines has been treated in the paper. The calculation of distribution of electric and magnetic fields has been performed by means of the finite volume method for entire span of the line. The theoretical justification of the method for calculation the parameters of electromagnetic field taking into account the change of the vector of magnetic potential along the line has been given. The problems of electrostatic and magnetostatic for a single electric conductor and unlimited long conductor with current have been solved. For the inner and total inductivities of a single conductor under the current have been obtained relationships and drawn dependences. Dependence between the speeds of light and of electromagnetic wave’s propagation has been presented. Based on the characteristics of distribution of electric and magnetic fields of multi-conductor lines has been provided the method of calculation of the matrix of own and mutual capacitances and inductivities the calculated values of per unit length parameters of compact 110 kV electric line which is in concordance with one of basic physical constant – the speed of light. |
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Keywords: multi-conductor overhead line, magnetic field, matrix of per unit length parameters.
DOI: https://doi.org/10.5281/zenodo.1207876
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State Support for Promotion of Electrical Energy Produced in High Efficiency Cogeneration in Romania
Authors: MUSHATESCU V.1, PODASHCA C.2, OPRISH Ioana3 1National Romania Commitee of the World Energy Council 2National Autority for Regulation in Energy 3Politechnical University of Bucharest
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Abstract: Romania accumulated a useful experience in supporting high efficient cogeneration through a bonus type scheme. Spreading this experience to other countries that can choose a similar support scheme could lead to important savings and better results in developing this efficient tool. This state aid is operational, targeted to new investments stimulation for cogeneration technologies and replacement or existing plants rehabilitation. Present paper focuses on the results of support scheme after five years of its application: increase of number of producers who benefit of this aid, raising of general efficiency of high efficient cogeneration, important savings of primary energy and CO2 emissions avoided. On the other hand, use of this scheme showed a number of problems (to which this paper proposes adequate solutions) on institutional/administrative, investition, technical, economical-financial and social frameworks that influences beneficiaries and/or financiers of state aid. |
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Keywords: energy efficiency, cogeneration, state aid – bonus.
DOI: https://doi.org/10.5281/zenodo.1207882
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The Control of Fluxes of Electric Power in Networks by Means of Phase-switching Booster Transformers
Authors: Govorov F.P., Govorov V.F., Romanova T.I. A.N. Beketov Kharkiv National University of Municipal Economy Kharkiv, Ukraine
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Abstract: Problems of increasing the efficiency of the operation of electrical networks based on the utilization of booster transformers (BT) with electronic control, applied on the base of active elements in smart electric grids of power systems and giving the function of automatic correction of the parameters of the network, assuring the conditions of optimal common operation are studied in the paper. The mathematic model of the processes in the electric networks with booster transformer has been developed; the opportunity of control by means of the phase-switching BT for power fluxes in the networks has been established. It has been shown that for the groups of switching the windings 1-5 of BT occurs additional consumption of power from the supply network, but for the groups 7-11 its recuperation to the load network. Respectively, switching the windings of BT to the group 1-5 assures the shift of load current to the direction of lag, but in the case of switching to the group 7-11 – towards the outrunning. Wherein, for the groups of switching 10-11 and 1-2 one can observe the increasing of the voltage at the output of BT, but for the groups 7-8 and 4-5 it is decreasing. Based on the analysis of the results of research the diagram and constructive models of the transformer have been proposed. The quasi-stationary and transient regimes were investigated and the conditions of reliable operation at these the regimes have been determined. The ways for increasing the efficient common operation for the transformer and network in the case of switching the thyristors into the circuit of the primary winding of the transformer have been proposed. |
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Keywords: booster transformer, thyristor, active power, reactive power.
DOI: https://doi.org/10.5281/zenodo.1207886
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Assessing Losses of Power and Electrical Energy in Unbalanced Medium Voltage Distribution Networks
Authors: Toader C.1, Golovanov N.1, Porumb R. 1, Trishtiu I.1, Bulac C.1, Mandish Al.1, M. Tirshu2 University Polytechnic of Bucharest, Bucharest, Romania 2Institute of Power Engineering of Academy of Sciences of Moldova, Chisinau, Republic of Moldova
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Abstract: The work is dedicated to calculating electricity losses related to power lines average voltage overhead or underground, which in terms of construction can be three-phase (three or four wire) in unbalanced sinusoidal harmonic, determining energy efficiency indicators (such as positive and negative factors of unbalance) thereof. It examines a case study and argues the results. |
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Keywords: indicators of unbalance of electricity, power and energy loss calculation.
DOI: https://doi.org/10.5281/zenodo.1207897
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A Comparative Analysis of the Efficiency of Thermal and Electric Energy Production in the District Heating Systems
Authors: Berzan V., Postolaty V., Bikova Elena, Babich V. Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova
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Abstract: In the base of the technical and economic indicators of the exploitation, an analysis of the efficiency of operation of Combined Heat and Power stations (CHP) in the district heating system at various loads during the year have been provided. The value of specific indicators of operation of the CHPs have been determined: a specific consumption of the fuel, the cost of the fuel per unit of energy produced, as well as the difference between the selling price of energy and acquisition costs of the fuel. As have been found, the optimization of CHP’s of the district heating loading during the year in the Chisinau municipality can offer an economic benefit amounted at 13-19 mln. lei MD in comparison with the current practice of CHP’s generation capacity use. |
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Keywords: CHP, efficiency, assessment, specific consumption, the share of energy produced fuel cost.
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RENEWABLE ENERGY SOURCES
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The Use of the Biomass in the Republic of Belarus. Status and Prospects of Development
Authors: Vasilevich S., Malko M., Shevchik N. Institute of Power Engineering of the National Academy of Sciences of Belarus Minsk, Republic of Belarus
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Abstract: The status and prospects of development in the field of biomass use as a fuel and energy resources in the Republic of Belarus are discussed in the paper as a fuel and energy resources. Currently, the main use of biomass in the energy sector of country is based on the use of wooden biomass for boilers of the Ministry of Housing and Communal Services, for mini- CHP of the concern “BelEnergo” of the Ministry of Power and as well as fuel in rural settlements of Belarus. In recent years, the development of biogas technology that uses crop residues, wastes of livestock and poultry farming. Contribution of these 2 types of biomass in Belarus to the total consumption of fuel and energy resources of country is about 5,6% at present. |
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Keywords: biomass, wooden chips, fuel, biogas technology.
DOI: https://doi.org/10.5281/zenodo.1207901
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Techno-economical Analysis of Hybrid PV-WT-Hydrogen FC System for a Residential Building with Low Power Consumption
Authors: Badea G.1, Felseghi R.-A.1, Raboaca M.-S.2, Ashchilean I.1, Bolboaca A.1, Mureshan D.1, Moldovan E.1, Shoimoshan T.-M.1 1 Building Services Engineering Department, Technical University of Cluj-Napoca, Romania 2 National Researches and Development Institute for Cryogenics and Isotopic Technologies - ICSI, Rm.Valcea, Romania
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Abstract: This paper shows a techno-economical analysis on performance indicators of hybrid solar-wind-hydrogen power generation system which supply with electricity a low - energy building, located in Cluj-Napoca. The case study had the main objectives, as follows: cost estimation, evaluation of energy and environmental performance for a fuel cell integrated into a small-scale hybrid system power generation and estimation of electrolytic hydrogen production based on renewable energy resources available on the proposed site. The results presented in this paper illustrate a case study for location Cluj-Napoca. The wind and solar resource can play an important role in energy needs for periods with "peak load" or intermittent energy supply. However, hydrogen production is dependent directly proportional to the availability of renewable energy resources, but the hydrogen can be considered as a storage medium for these renewable resources. It can be said that this study is a small-scale model analysis, a starting point for a detailed analysis of Romania's potential electrolytic production of hydrogen from renewable resources and supply electricity using fuel cells integrated into hybrid energy systems. |
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Keywords: fuel cell, hydrogen, hybrid system, renewable energies, low energy building.
DOI: https://doi.org/10.5281/zenodo.1207923
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Stochastic Optimization of Power System Operation in Presence of Renewable Energy Sources
Authors: Dumbrava V., Lazaroiu G.C., Bazacliu G., Teliceanu M. University POLITEHNICA of Bucharest. Bucharest, Romania
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Abstract: The liberalization process of the energy market structure determined significant changes in the electric utility industry, from both generating and transmission perspectives, and new generation technologies emerged, deeply influencing the industry profile. Nowadays, based on the governmental incentives and free access to the power systems, the share of renewable energy sources in the bulk power system generation is increasing. With respect to the classical fuel-based sources, the renewable energy sources (like photovoltaic and wind turbines) have an intermittent character determined by the meteorological conditions. Their production cannot be known exactly, but can be forecasted with some degree of accuracy. Thus, within the power system, network measures must be adopted for ensuring its safe operation. |
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Keywords: renewable energy, electric energy market, stochastic optimization.
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HEAT POWER ENGINEERING
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Numerical Analysis of Aerodynamic Characteristics of the Finned Surfaces with Cross-inclined Fins
Authors: Lagutin A. E., Stoyanov P. F. Educational and Scientific Institute of Refrigeration Cryotechnologies Ecology and Energetic Odessa National Academy of Food Technologies, Odessa, Ukraine
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Abstract: This paper presents results of numerical research and analyses air-side hydraulic performance of tube bundles with cross inclined fins. The numerical simulation of the fin-tube heat exchanger was performed using the Comsol Femlab software. The results of modeling show the influence of fin inclination angle and tube pitch on hydraulic characteristics of finned surfaces. A series of numerical tests were carried out for tube bundles with different in-clination angles (γ =900, 850, 650, 60), the fin pitch u=4 mm. The results indicate that tube bundles with cross inclined fins can significantly enhance the average integral value of the air flow rate in channel between fins in comparison with conventional straight fins. Aerody-namic processes on both sides of modificated channel between inclined fins were analyzed. The verification procedures for received results of numerical modeling with experimental data were performed. |
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Keywords: numerical research, aerodynamics, finned tubes, experiment, inclined fins, energy efficiency.
DOI: https://doi.org/10.5281/zenodo.1207931
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Investigation of Heat Exchange Efficiency in the Heat Exchanger Waste Heat Recovery with Granular Nozzle
Authors: Boshkova I.L., Solodkaya A.V. The Department of power engineering and pipeline transport energy carriers Institute of Refrigeration, Cryogenic Technologies and EcoEnergetic Odessa National Academy of Food Technologies, Odessa, Ukraine
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Abstract: The article analyzes the characteristics of the heat transfer process between the dispersed and gaseous medium for the moving and fixed layer of particulate material. The methods of calculus of thermal and hydraulic regimes of heat exchangers with a dense layer of particles were elaborated. The results of experimental studies of the process of heating of different kinds of granular material, intended for use as a nozzle in the recuperative heat exchanger. The influence of the height of heating chamber, the particle diameter on the output temperature of the granular material has been determined. The dependence of the temperature of the gas and solid components of the height of the nozzle has been presented. |
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Keywords: a granular material, a nozzle, the heat transfer coefficient, Interconnects heat exchange, intensification, aerodynamic drag.
DOI: https://doi.org/10.5281/zenodo.1207958
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Improving the Efficiency of the Heat Pump Control System of Carbon Dioxide Heat Pump with Several Evaporators and Gas Coolers
Authors: Sit M.L., Juravliov A.A., Sit B.M., Timchenko D. Institute of Power Engineering of the ASM, Chisinau, Republic of Moldova
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Abstract: The problem of coordination of the values of the refrigerant flow through the evaporators and gas coolers of the heat pump for the simultaneous production of heat and cold is studied. The compensation of the variations of the total flow through the evaporators is implemented using the variation of the capacity of the compressor and a corresponding change in flow through the auxiliary gas cooler of the heat pump. Control system of this gas cooler is constructed using the invariance principle of the output value (outlet temperature of the heated agent) with respect to perturbations on the control channel (the refrigerant flow through the gas cooler). Principle of dual-channel compensation of the disturbance and advancing signal on input of control valve of the refrigerant through the gas cooler is ensured. Due to proposed solution, the intensity of the disturbances on the flow of refrigerant is reduced. Due to proposed technical solution power consumed by the heat pump compressor drive under transients is decreased. |
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Keywords: heat pumps, simultaneous production of heat and cold, control systems using the principle of invariance.
DOI: https://doi.org/10.5281/zenodo.1207960
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The method of Determining the Limits of Possible Increase of Tariffs for Energy and Other Material Costs in the Sectors of the Economy of Republic of Moldova, on the Basis of the Analysis of National Accounts
Authors: Postolaty V.M. Institute of Power Engineering of the Academy of Science of Moldova, Chisinau, Republic of Moldova
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Abstract: A method for calculating the limits of possible increase of tariffs for energy and other material costs in the sectors of the economy of Moldova, on the basis of the analysis of national accounts was elaborated. The analysis of macroeconomic indicators of the Republic of Moldova's economy for the period 2002-2014 was performed. The formulas that allow for practical calculations of allowable limits the possible establishment of tariffs for energy and other material costs to consumers at the stage of production and the end of its consumption with the use of national accounts were proposed. Proposals based on the fact that the real tariff increases should not exceed the growth of gross value added and real gross domestic product should be taken into account the purchasing power of consumers and the consumer price index. |
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Keywords: energy tariffs, production, gross value added, gross domestic product, intermediate consumption deflator index, the consumer price index.
DOI: https://doi.org/10.5281/zenodo.1207962
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MEMORY George V. Chaly(1916 - 1996)
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