KOMUNALNA ENERGETIKA / POWER ENGINERING 2014
KOMUNALNA ENERGETIKA 2014, _.
KOMUNALNA ENERGETIKA / POWER ENGINERING, 00
KOMUNALNA ENERGETIKA, _.
PROGRAMME
KOMUNALNA ENERGETIKA / POWER ENGINERING, 0
Programme
KOMUNALNA ENERGETIKA 2014, _.
KOMUNALNA ENERGETIKA / POWER ENGINERING, 000
MARČIČ, T.
Leading Lectures
KOMUNALNA ENERGETIKA / POWER ENGINERING, 1
ČERNILOGAR RADEŽ, M.
TOWARDS NEW ENERGY CONCEPTS IN REPUBLIC OF SLOVENIA
KOMUNALNA ENERGETIKA / POWER ENGINERING, 2
ŠMID, A.
PRINCIPLE OF SUSTAINABLE SPATIAL PLANNING
KOMUNALNA ENERGETIKA / POWER ENGINERING, 3
ŠTUMBERGER, G.
SMART GRIDS AND SMART BUILDINGS CONNECTION
KOMUNALNA ENERGETIKA / POWER ENGINERING, 4
VIDONJA, T.
ARE SMART GRIDS DOOMED TO FAIL?
KOMUNALNA ENERGETIKA / POWER ENGINERING, 5
JAHIĆ, A., KONJIĆ, T., PIHLER, J.
DISTRIBUTION SYSTEM PLANNING USING GENETIC ALGORITHM
KOMUNALNA ENERGETIKA / POWER ENGINERING, 6
Optimal configuration of a distribution system implies topology of the network with adequate conductor cross sections (power line sizes), and active and the reactive powers of source nodes which will simultaneously optimize several objective functions. At the same time all technical constraints must be satisfied like: voltage level limitations, radiality of the network, allowable continuous current limitations, as well as the limitations of the power delivered by the source nodes. The method of multi-objective optimization, as used in this work, is based on a Genetic algorithm and the Pareto principle of optimality. The obtained results verify the applicability of the proposed algorithm for a wide-range of distribution system planning problems.
PADINGER, R., TÜRK, A., GUBINA, A.
INCREASE - INCREASING THE PENETRATION OF RENEWABLE ENERGY SOURCES IN THE DISTRIBUTION GRID BY DEVELOPING NEW CONTROL STRATEGIES AND OFFERING ANCILLARY SERVICES
KOMUNALNA ENERGETIKA / POWER ENGINERING, 7
The INCREASE project is investigating ways to manage renewable energy sources in Low- and Medium Voltage networks, to provide ancillary services towards distribution- and transmission system operators, in particular voltage control and provision of reserve. The project will investigate the regulatory framework, grid code structure and ancillary market mechanisms, and propose adjustments to facilitate successful provisioning of ancillary service, necessary for the operation of the electricity grid.
The project will enable distributed renewable energy sources (DRES) and loads to go beyond just exchanging power with the grid which will enable the system operators to evolve from a congestion manager to capacity manager. This will result in a more efficient exploitation of the current grid capacity, thus facilitating higher DRES penetration at reduced cost.
A simulation platform will enable the validation of the proposed solutions and provides the distribution system operators with a tool they can use to investigate the influence of DRES on their distribution network. The solutions will be validated by lab tests, as well as in field trials in the real-life operational distribution network of Elektro Gorenjska (Slovenia), Stromnetz Steiermark (Austria), and Liander (the Netherlands).
The project runs from September 2013 till August 2017, co-ordinator is Gent University
Project, co-funded by the EC in the 7th Framework Programme, http://www.project-increase.eu/
SREĆKOVIĆ, N., BELIČ, E., ŠTUMBERGER, G.
COMPARISON OF METHODS FOR LOAD FLOW CALCULATION IN LOW VOLTAGE DISTRIBUTION NETWORK WITH CONNECTED DISPERSED PRODUCTION
KOMUNALNA ENERGETIKA / POWER ENGINERING, 8
Load flow analysis represents one of the core methods used in modern distribution system operation. Therefore, it is necessary to provide efficient, numerically robust load flow algorithms with fast convergence and minimum usage of memory, suitable for variety of operating scenarios. The paper presents, compares and evaluates two efficient methods for load flow calculation in distribution network – backward/forward sweep method and direct method. The procedure of modeling the distribution network elements – line sections, loads, distributed generation units, as well as the implementation of algorithms, has been presented. The analysis has been performed on low voltage distribution network system.
BELIČ, E., DEŽELAK, K., ŠTUMBERGER, G.
A LINE VOLTAGE DEPENDENCY ANALYSIS ON ACTIVE AND REACTIVE POWER FLOW AT DIFFERENTC LOW VOLTAGE LINES
KOMUNALNA ENERGETIKA / POWER ENGINERING, 9
The paper provided presents a line voltage dependency analysis on active and reactive power flow. The line voltage dependency is studied based on analytical expression. For the analysis it is assumed that one end of the line is connected to infinite bus, while at the other end voltage is observed in dependency of active and reactive power flow. The analysis covers three different low voltage cables with two different lengths. The results shows that in low voltage network voltage significantly depends on active power flow, while reactive power flow dependency is minimal. Voltage dependency increases, when low voltage lines are extended.
AŽBE, V., MIHALIČ, R.
FAULT-CURRENT LIMITATION IN SLOVENIAN ELECTRIC-POWER TRANSMISSION SYSTEM
KOMUNALNA ENERGETIKA / POWER ENGINERING, 10
Reinforcement of electric-power systems (EPS) with construction of new power lines, additional interconnections between networks, a growth in generating capacity and upgrade to a higher voltage levels (e.g., from 220 kV to 400 kV) is a natural and logical way of development of EPS in order to improve the stability and reliability. However, on the other side, these reinforced networks can reach or even exceed their limits with respect to the short-circuit current withstand capability. The problem of too high fault currents can be firstly expected in reinforced networks that supply big cities. This paper presents and discusses various methods for limiting these fault currents in 110 kV electric-power network. These methods can be either passive (i.e., increase of impedance at nominal and fault conditions) or active (i.e., small impedance at nominal load and fast increase of impedance at fault occurrence). As typical structure of substation at 110 kV level is in the form of double busbar with two transformers, special attention is paid on inserting fault-current limiters at the position of bus coupler. The results of application of various fault current limiters are presented on the case of Slovenian EPS for the year 2030.
THALER, S., HAUSER, R.
ENERGY STORAGE THROUGH THE USE OF PHASE CHANGE MATERIALS (PCM)
IMPLEMENTATION AND EVALUATION OF LATENT STORAGE TANKS FOR ECONOMICAL HEAT STORAGE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 11
Due to fluctuating electricity networks (electricity generation from wind, photovoltaic...) it will be increasingly important in the future to perform network smoothing. This should be done on smart grids. Once electricity is not storable, it may be a good idea to produce heat at current excess and store it.
Currently, water is still considered as the most appropriate storage medium. Furthermore, there are also latent heat storage materials such as zeolite (only at high temperatures) or salt mixtures (e.g. sodium acetate) available. Also paraffin and other materials in which a phase change (liquid to solid) takes places are available. These stores have at present, however, the problem of heat conduction within the storage mass.
It is now scheduled to integrate suitable PCM-tanks into an existing heat pump system. The modified system should be able to store the excess energy and to recirculate it into the heating system. This should lead to an economically use of the heating pump and also to compensate the fluctuating power generation. As a significant parameter in this case the influence of the charging and discharging times is considered. The expected results should provide innovative heat storage methods to overcome these new challenge
SOVIČ, B., GOVEDIČ, B., TOPLAK, F.
DEVELOPMENT OF BASIC PUBLIC INFRASTRUCTURE FAST CHARGERS ON HIGHWAY CROSS – AREA ELEKTRO MARIBOR
KOMUNALNA ENERGETIKA / POWER ENGINERING, 12
Development of basic public infrastructure of fast charging stations along the motorway network is crucial for the wider use of electric vehicles.
Fast charging stations, depending on the number of quick chargers and location of placement, require reinforcement of the electricity network and the associated investment costs.
ELBE, A., NIEDERMAYR, F., ZANDER, D., EGGER, W.
AKKU4FUTURE - MEASUREMENT METHODES FOR STATE INDICATION OF LITHIUM ION ACCUMULATORS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 13
Lithium ion batteries require a strict operation window in terms of terminal voltage, load current and cell temperature. Battery management systems (BMS) have to ensure the safe operation of lithium ion batteries. The functionality of such a BMS features the estimation of the state of the cell in terms and to provide some information (mostly the state of charge) to the user. The state indication is of high importance due to the fact that the knowledge about the health of the battery enables the BMS to act if the battery health gets worse, or even can slow down battery aging processes by acting preventively.
This paper describes measurement strategies to create data for the quantification of the state of charge (SOC) and the state of health (SOH) of a lithium ion battery. A measurement setup has been established to enable automated cycling of the test cells to age the rapidly. During cycling the cell capacity is monitored, because it is representative for the aging of the cell. The measurements are used to fit an equivalent electrical circuit. The derived parameters can be used to estimate the actual state of the cell. The understanding of the cell is the key to be able to design a sufficient and accurate state indication system.
SUKIČ, P., DREVENŠEK, D., BELIČ, E., ŠTUMBERGER, G.
EFFICIENCY OF INVERTERS IN SOLAR POWER PLANTS WITH REACTIVE POWER GENERATION
KOMUNALNA ENERGETIKA / POWER ENGINERING, 14
The paper discusses possibilities for reactive power generation using inverters for solar power plants. Measurements performed on an inverter for solar systems were performed for different values of generated active and reactive power in order to determine the efficiency characteristic. The obtained characteristic is approximated with a surface. It is applied to evaluate increase of inverter losses due to reactive power generation as well as to evaluate the potential of inverters in solar power plants for reactive power generation.
BELAK, L., MARUŠA, R., FERLIČ, R., RIBIČ, J., PIHLER, J.
ANALYSIS OF THE SLEET CONSEQUENCES IN 2014 IN THE ELES TRANSMISSION SYSTEM
KOMUNALNA ENERGETIKA / POWER ENGINERING, 15
Republic of Slovenia and part of the neighboring countries in the end of January and beginning of February cover weather storm snow, sleet and rain. LED is a natural weather phenomenon that occurs periodically in different parts of Slovenia, particularly in mountain bulkheads where they encounter different climates. LED 2014 hit large parts of Slovenia and the large amount of ice, which cling variety of items including paralyzed. Most damage is caused to forests, power, rail and road infrastructure. During this period, around 10% of Slovenia's population were been without electricity. In this article we summarize the weather situation, past experience and damage to the transmission network. At the end of the article we show an analysis of the transmission network for the period before and after the ice 2014.
TOROŠ, Z.
RISKS AND CONTINUITY OF SUPPLY OF ELECTRIC ENERGY
KOMUNALNA ENERGETIKA / POWER ENGINERING, 16
Distribution power system remains one of the cornerstones of the entire society. Regulator of the electricity market provides and monitors the quality of power supply system. The most important requirement is the continuity of supply of electricity, which is regulated by the regulator of the electricity market.
Extreme weather conditions, as they were this year, in January and February, pose high risks and significant impact on the continuity of supply of electrical energy.
This paper describes the basic concept of risk management in relation to extreme weather conditions.
KITAK, P., PIHLER, J., l GLOTIĆ, A., HORVAT, D., ŠPELIČ, D., ŽALIK, B., TIČAR, I.
APPROACHES TO SPATIAL VISUALIZATION OF OVERHEAD LINES ELECTROMAGNETIC FIELD
KOMUNALNA ENERGETIKA / POWER ENGINERING, 17
This paper deals with the art of voxel visualization technique of electromagnetic radiation on the high voltage transmission line. Results are useful for the electrical engineering society, in education, for environmental agencies and other non-experts. Paper covers three main subjects, i.e. the numerical analysis of electromagnetic field by the finite element method, classical electromagnetic field presentation in postprocessor of numerical program tool and visualization of the electromagnetic field with the volume ray casting technique. In the last representation, for each pixel of the displayed image a ray of sight is shot into voxel space and intersection is calculated. This method enables the representation of results independently of the numerical program tools.
VORŠIČ, Ž., PIHLER, J., KITAK, P.
ENVIRONMENTAL IMPACT OF SEMIINSULATED CONDUCTORS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 18
For overhead power lines, there are increasingly used compact conductors with carbon core. If such a conductor is »incomplete« isolated, we get covered conductorm which is mechanically stronger and what is even more important, it is spatially less wasteful. Furthermore, because of the isolation the electric field strength is lower near such a conductor.
There is a design of a covered conductor given in this article, which we could install on the existing 220 kV columns and so increase the transmission capacity of the Slovenian electricity network. The integration of regular energy infrastructure is increasingly demanding, therefore we investigated the impact of such covered conductor for the highest voltage levels to the environment. We compared the analytical calculation of the electric field strength near the proposed covered conductor with the method of finite elements. The results were evaluated according to the regulation on electrictromagnetic radiation in the natural and living environment.
ROŠER, M., ŠKOF, R., ŠTUMBERGER, G.
EARTH FAULT IN MEDIUM VOLTAGE DISTRIBUTION NETWORKS WITH RESONANT NEUTRAL EARTHING
KOMUNALNA ENERGETIKA / POWER ENGINERING, 19
Reliability of electricity supply is directly related to the supply interruptions, mostly caused by earth faults that appear in medium voltage distribution networks. One of very effective measures, that can substantially reduce the supply interruptions due to the earth fault in medium voltage distribution networks, is resonant neutral earthing. It compensates capacitive currents and reduces the current flowing through the fault which establishes better conditions for arc self-extinguishing at the earth fault location. The paper deals with conditions at the location where vegetation touches the conductor and establishes an earth fault. The results of field-testing performed in substation Krško, where earth faults were established under controlled conditions, using specially for this purpose build mechanical device, are presented and discussed.
MARUŠA, R., VORŠIČ, J., PIHLER, J., FERLIČ, R., BELAK, L., RIBIČ, J., MARUŠA, L.
TESTING SLIDING GROUNDING CLAMP FOR EARTHING CONDUCTORS TO DOUBLE-CIRCUIT 110 KV TRANSMISSION LINE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 20
This paper presents the testing Sliding clamps for grounding conductor transmission line. For the purpose of an effective transmission line grounding in working with vicinity of high voltage a special form of sliding clamps for grounding has been designed. Grounding device is intended for grounding transmission line conductors, which are dragged along conductor installation on a double-circuit transmission line, the second system operates normally which represents a significant risk for single-phase ground fault . The device must provide such a connection during the sliding along the guide, so that it prevents the arc and effectively discharges ground current into the ground.
Prior to regular usage, it was necessary for grounding the device to perform a series of tests, which are described in this article. A test with the realization of single-phase ground fault was also carried out on the transmission network of 110 kV ELES. All tests have been successful and positive.
TRBUŠIĆ, M., PIHLER, J.
PLANNING OF LABORATORY TESLA TRANSFORMER
KOMUNALNA ENERGETIKA / POWER ENGINERING, 21
Paper presents a calculation of the Tesla transformer, which was built in Powerlab at the Faculty of Electrical Engineering and Computer Science at the University of Maribor. The mathematical model is defined using differential equations and is solved by finding the eigenvalues and the corresponding eigenvectors in Matlab. Inductances and ground capacitance of the HV winding are obtained from the magnetostatic and electrostatic energies, respectively, and calculated using FEMM 4.2. The calculation method described represents the basis for the construction of the Tesla transformer.
HOSNAR, J., KOVAČ KRALJ, A.
RECONSTRUCTION OF ENERGY-CHEMICAL PROCESSES
KOMUNALNA ENERGETIKA / POWER ENGINERING, 22
Low efficiency, negative impacts on the environment and non-profitable operation is the main shortcomings of outdated energy-chemical plants. In order to ensure flexible production and optimum operation, it is not enough just to look for savings in utility costs (UC), but it also makes sense to adapt processes. The reconstruction direction would be effective with the sustainable development and interesting market chemical products. Promising alternative fuel is also dimethyl-ether (DME). The examined study of this paper focuses on the development of the reconstruction technique for update irrational process systems or complete plants. Reconstruction method can be implemented in the case study of the existing MeOH plant. This is unprofitable and consequently not operating. The conceptual model developed in the direction of new-product production, is a good tool for reconstruction of energy-chemical processes. The objectives of the set method are: i.) Maintain the existing process units and chemical processes to a greater extent, ii.) Enable the potential for finding new process alternatives and technology solutions, iii.) Provide a streamlined operation of all subsystems and systems, and iv.) Promote environmental and social acceptability. In the paper they were validated lower operating costs one-step, compared with the two-step synthesis of DME from NG.
KRMELJ, V., MIRT, B.
ENERGY PLANNING IN LOCAL COMMUNITY
KOMUNALNA ENERGETIKA / POWER ENGINERING, 23
Spatial planning has a key role in the transition to a low carbon future. The need to achieve climate and broader environmental goals requires new approaches through which energy is recognized as an integral part of the planning. Effective local plans based on the integration of space, energy use and energy production contribute to addressing key issues related to the climate change and on the long term they bring significant environmental, social and economic benefits to the local communities. In the article theoretical principles and the importance of integration of spatial and energy planning as well as preparation of Energy card are presented following with the presentation of current activities of the Municipality of Maribor in this area.
COPOT, A., KRMELJ, V., TEKAVEC, S.
SUSTAINABLE USE OF WOODEN BIOMASS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 24
Energy needs are from year to year higher because of increasing economic growth. Energy is obtained from non-renewable sources such as fossil fuels (coal, gas and oil). From their use we are polluting environment and risking our health. The trend shows that we will soon use all stocks of fossil fuels. Therefore are growing demands for renewable energy sources. Among renewable energy sources belongs wooden biomass which is CO2 neutral. Slovenia has very large biomass potential, because more than half of the country is covered with forests.
COPOT, A., KRMELJ, V.
ELECTRICITY AS AN ALTERNATIVE FUEL AND LEGISLATIVE DEMANDS FOR SUSTAINABLE MOBILITY
KOMUNALNA ENERGETIKA / POWER ENGINERING, 25
Transport is becoming one of the biggest polluters of our environment in all countries - Slovenia is no exception. The biggest impact is most evident in the urban areas. Consequently in the cities, there are big traffic jams, noise, air pollution and increased vibration.
There is no doubt that people will still use cars as a basic means of transport, so we are looking for more environmentally friendly - alternative fuels. A good alternative is the electric mobility that is becoming increasingly popular. Driving cars on electricity which is produced from renewable energy sources.
HORVAT, B., ČEPIČ, B., VARL, N.
CONTRACTUAL PROVISION EFFICIENT ENERGY CONSUMPTION - REFURBISHMENT OF AN HEATING OIL HEATING PLANT
KOMUNALNA ENERGETIKA / POWER ENGINERING, 26
Heating apartments and business premises is not only a necessity for normal life and work, but also an economic category, because it represents costs and a health category, because it pollutes the air with CO2 and causes harmful effects on our health with particulate matter (PM10, PM2,5), nitrogen oxides and other substances.
In order to achieve business strategies and European environmental commitments in the field of environmental and energy policies, Energija plus included in its sales program beneath electricity also the sale of natural gas and biomass, and implemented the refurbishment of an heating plant and district heating system in Pobrežje, Maribor. The project refers to the heating of 580 residential units, covering total 26.510 m2 of heated living area. The heating plant was built in 1974 and based on mazut. That was later changed to the heating oil. The walls of the buildings were simple and without insulation also without insulating doors and windows. During the period between 2010 and 2014 the owners accomplished energy renovation of apartment buildings by changing external doors and windows, additional thermal insulation of the facade and in partnership with Energija plus refurbishment of heating.
Users of the heating system got with renovation a modern heating plant and heating system which provides less harmful emissions in their local environment and significantly lower cost of heating. Fixed costs of heating system management together with the costs of financing the project remained the same as they were before the investment. Variable costs decreased by more than 30 %, which was a primary objective of the users.
OSTRELIČ, R.
EXPERIENCES WITH ENERGY PROJECT FINANCING
KOMUNALNA ENERGETIKA / POWER ENGINERING, 27
KRMELJ, V.
EKO SKLAD AS A SOURCE OF FUNDING
KOMUNALNA ENERGETIKA / POWER ENGINERING, 28
RUDNIK, M.
FINANCIAL RESOURCES WITHIN THE EUROPEAN INVESTMENT BANK
KOMUNALNA ENERGETIKA / POWER ENGINERING, 29
VOVČKO, B., VOVČKO, B., ŠTRICELJ, A., SEME, S.
MATHEMATICAL MODEL OF SOLAR CELL COMPOSED IN MATLAB/SIMULINK
KOMUNALNA ENERGETIKA / POWER ENGINERING, 30
This article presents a mathematical model of solar cell composed in Matlab/Simulink. Mathematical models of solar cell presented in the article are differ in the complexity of the structure and consequently the accuracy of the responses to the input parameters and they are named as ideal, simple, single-diode and two-diode model. In Matlab/Simulink are mathematical models of solar cell assembled with the help of terms, which describe the operation of solar cell. We compared mathematical models of solar cell with each other and we were evaluated them by comparing with the measured values of the actual solar cell.
VOVČKO, B., VOVČKO, B., ŠTRICELJ, A., SEME, S.
MATHEMATICAL MODEL OF SOLAR POWER PLANT BRESTANICA
KOMUNALNA ENERGETIKA / POWER ENGINERING, 31
This article presents a mathematical model of solar power plant composed of Matlab/Simulink. For the evaluation of simulation results of the mathematical model of the solar power plant we use the results of measurements from the actual solar power plant Termoelektrarna Brestanica d. o. o. We evaluate the results of simulation calculations and measurements of the actual plant for different days of the year. The results show good correlation between calculated and measured values of solar power, which is a good basis for further use of mathematical model of solar power for the analysis of voltage profiles of the network.
HORVAT, J., RAJH, A.
EVALUATION OF WATER COURSE LOBNICA AND THE CONSTRUCTION OF RUŠE SHPP
KOMUNALNA ENERGETIKA / POWER ENGINERING, 32
Construction of small hydropower palnts is necessary to meet EU and national strategic objectives in the field of power generation and security as well as preservation of the environment. Environmental restrictions and complicated administrative procedures in the Republic of Slovenia make it very difficult to select the appropriate site for construction, complicate construction procedures and consequently render power generation more difficuit. The available hydro potential in the Republic of Slovenia is above the EU average and enables meeting EU objectives; nevertheless, it has not been utilised efficiently. This paper addresses limitations we were faced with during the evaluation of water course Lobnica and the construction of Ruše sHPP.
KOKALJ, F., ZABUKOVNIK, M., SAMEC, N.
DESIGN AND OPERATION OF FIRST SLOVENIAN HEATING PLANT TO THE ENERGY-RICH FRACTION WASTE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 33
Each year modern society produces more waste. Domestic habits and economic standard places us next to other developed countries thus statistically taken every person produces around a kilogram of waste per day. Taking into account the average heating value of waste this equals around a quarter of liter of heating oil or almost one-hundred liters per year. This energy potential is presently deposited in landfills across the country, causing shortage of deposition space, emission of green-house gases and production of polluted leaching water.
The utilization of this semi-renewable national energy source represents great challenge of the present time. Waste- to – energy means utilization of domestic energy source and greater import independence. The utilization of this energy is only possible with district energy systems. Our country has committed itself to utilize by the year 2020 25% of total consumed energy from renewable sources. The energy of waste can contribute to fulfil this commitment.
This paper is going to present a modern integral waste management system in Celje region and utilization of energy rich waste fraction after mechanical and biological treatment. The Celje heating plant is in operation for five years and it utilizes combustible fractions of the waste and produces power (electric energy) and hot water. The latter is distributed to the citizens of Celje over the existing district heating system
ROŽMAN, M.
NATURAL GAS IN TRAFFIC
KOMUNALNA ENERGETIKA / POWER ENGINERING, 34
The presentation is divided into seven sections, through which we intend to present the project of introducing natural gas to the transport. We will present functioning of the cars on natural gas, describe the latest technological solutions in this area, say a few words about the availability of such vehicles and present the advantages and disadvantages of them. After that we will present filling techniques from small scale stations for home use to professional public filling stations. A few words will be given to the newly-established brand, over which we have decided to sell and introduce natural gas in transport use. In the last part we will present our achievements and our short- and long-term plans in natural gas application to the transport market.