Volume 16 / Issue 1 JUNE 2023 www.fe.um.si/en/jet.html 2 JET JET 3 VOLUME 16 / Issue 1 Revija Journal of Energy Technology (JET) je indeksirana v bazah INSPEC© in Proquest’s Technology Research Database. The Journal of Energy Technology (JET) is indexed and abstracted in database INSPEC© and Proquest’s Technology Research Database. 4 JET JOURNAL OF ENERGY TECHNOLOGY Ustanovitelj / FOUNDER Fakulteta za energetiko, UNIVERZA V MARIBORU / FACULTY OF ENERGY TECHNOLOGY, UNIVERSITY OF MARIBOR Izdajatelj / PUBLISHER Fakulteta za energetiko, UNIVERZA V MARIBORU / FACULTY OF ENERGY TECHNOLOGY, UNIVERSITY OF MARIBOR Glavni in odgovorni urednik / EDITOR-IN-CHIEF Jurij AVSEC Souredniki / CO-EDITORS Bruno CVIKL Miralem HADŽISELIMOVIĆ Gorazd HREN Zdravko PRAUNSEIS Sebastijan SEME Bojan ŠTUMBERGER Janez USENIK Peter VIRTIČ Ivan ŽAGAR Uredniško izdajateljski svet / PUBLISHING & EDITORIAL COUNCIL Dr. Anton BERGANT, Litostroj Power d.d., Slovenia Prof. dr. Marinko BARUKČIĆ, Josip Juraj Strossmayer University of Osijek, Croatia Prof. dr. Goga CVETKOVSKI, Ss. Cyril and Methodius University in Skopje, Macedonia Prof. dr. Nenad CVETKOVIĆ, University of Nis, Serbia Prof. ddr. Denis ĐONLAGIĆ, University of Maribor, Slovenia JET 5 Doc. dr. Brigita FERČEC, University of Maribor, Slovenia Prof. dr. Željko HEDERIĆ, Josip Juraj Strossmayer University of Osijek, Croatia Prof. dr. Marko JESENIK, University of Maribor, Slovenia Prof. dr. Ivan Aleksander KODELI, Jožef Stefan Institute, Slovenia Prof. dr. Rebeka KOVAČIČ LUKMAN, University of Maribor, Slovenia Prof. dr. Milan MARČIČ, University of Maribor, Slovenia Prof. dr. Igor MEDVED, Slovak University of Technology in Bratislava, Slovakia Prof. dr. Matej MENCINGER, University of Maribor, Slovenia Prof. dr. Greg NATERER, Memorial University of Newfoundland, Canada Prof. dr. Enrico NOBILE, University of Trieste, Italia Prof. dr. Urška LAVRENČIČ ŠTANGAR, University of Ljubljana, Slovenia Izr. prof. dr. Luka SNOJ, Jožef Stefan Institute, Slovenia Prof. Simon ŠPACAPAN, University of Maribor, Slovenia Prof. dr. Gorazd ŠTUMBERGER, University of Maribor, Slovenia Prof. dr. Anton TRNIK, Constantine the Philosopher University in Nitra, Slovakia Prof. dr. Zdravko VIRAG, University of Zagreb, Croatia Prof. dr. Mykhailo ZAGIRNYAK, Kremenchuk Mykhailo Ostrohradskyi National University, Ukraine Prof. dr. Marija ŽIVIĆ, Josip Juraj Strossmayer University of Osijek, Croatia 6 JET Tehnični urednik / TECHNICAL EDITOR Sonja Novak Tehnična podpora / TECHNICAL SUPPORT Tamara BREČKO BOGOVČIČ Izhajanje revije / PUBLISHING Revija izhaja štirikrat letno v nakladi 100 izvodov. Članki so dostopni na spletni strani revije www.fe.um.si/si/jet.html / The journal is published four times a year. Articles are available at the journal’s home page - www.fe.um.si/en/jet.html. Cena posameznega izvoda revije (brez DDV) / Price per issue (VAT not included in price): 50,00 EUR. Informacije o naročninah / Subscription information: http://www.fe.um.si/en/jet/ subscriptions.html Lektoriranje / LANGUAGE EDITING TAIA INT d.o.o. Oblikovanje in tisk / DESIGN AND PRINT Tiskarna Saje d.o.o. Naslovna fotografija / COVER PHOTOGRAPH Jurij AVSEC Oblikovanje znaka revije / JOURNAL AND LOGO DESIGN Andrej PREDIN Ustanovni urednik / FOUNDING EDITOR Andrej PREDIN Izdajanje revije JET finančno podpira Javna agencija za raziskovalno dejavnost Republike Slovenije iz sredstev državnega proračuna iz naslova razpisa za sofinanciranje domačih znanstvenih periodičnih publikacij / The Journal of Energy Technology is co-financed by the Slovenian Research Agency. JET 7 Spoštovani bralci revije Journal of energy technology (JET) Zgodovina uporabe matematike sega vsaj nekaj deset tisoč let v zgodovino. Tako so na primer v zgornjem toku Nila našli približno 20.000 let staro kost, na kateri se vidijo zareze, ki naj bi pomenile neko vrsto štetja oz. evidence. Obstajajo tudi risbe, ki so veliko starejše od prvih pismenih zapisov in nakazujejo na znanje o matematiki in merjenju časa na podlagi navideznih leg zvezd na nočnem nebu. S pojavom pisnih besedil se je na raznolikih mestih tekom zgodovine ohranilo kar nekaj zapisov o uporabi matematike – že v starem Egiptu sta bili matematika in njena uporaba na relativno visokem nivoju. To znanje so Egipčani uporabljali pri vsakodnevnih opravilih, astronomiji, … Matematika kot znanstvena veda se tudi danes naglo razvija v vseh svojih smereh in sočasno z njenim razvojem se širi tudi uporaba matematike v energetiki. V povezavi z razvojem računalniških zmogljivosti ter razvojem matematike in energetike je uporaba matematike za reševanje energetskih problemov vse pomembnejša. Tako je tudi v tej številki predstavljenih kar nekaj člankov, ki vključujejo zanimivo uporabo matematike, še posebej pa izstopa članek, v katerem je predstavljena uporaba mehke logike. Ob izidu prve številke v šestnajsti izdaji želim vsem bralcem zanimivo in prijetno branje. Jurij AVSEC odgovorni urednik revije JET 8 JET Dear Readers of the Journal of Energy Technology (JET) The history of the use of mathematics goes back at least several tens of thousands of years. For example, a bone about 20,000 years old was found in the upper reaches of the Nile. You can see notches on it, which may indicate some kind of counting or recordkeeping. There are also drawings dating back to a time long before written records that suggest a knowledge of mathematics and timekeeping based on the apparent positions of the stars in the night sky. With the advent of written texts, quite a few records of the use of mathematics have been preserved in various places throughout history. In ancient Egypt, mathematics and its application was already at a relatively high level. The Egyptians used the knowledge of mathematics in everyday tasks, as well as for astronomy, etc. Mathematics, as a science, is witnessing significant development even today, branching out in multiple directions. Alongside this development in mathematics is its use in energy technologies. In connection with the development of computing capabilities, the development in mathematics and energy and the application of mathematics in solving energy problems is becoming even more important. Even in the presented issue, there are quite a few articles that include an interesting use of mathematics. The article that highlights the use of soft logic stands out in particular. With the release of the first issue in its sixteenth edition, I hope our readers find their reading experience engaging and enjoyable. Jurij AVSEC Editor-in-chief of JET JET 9 Table of Contents Kazalo The Impact of Plug-In Hybrid Vehicles in Low-Voltage Distribution Systems Using a Monte Carlo Simulation Vpliv priključnih hibridnih vozil na nizkonapetostne distribucijske sisteme z uporabo metode Monte Carlo Evica Smilkoska, Vasko Zdraveski, Jovica Vuletić, Jordančo Angelov, Mirko Todorovski . . . . . 11 Generalised fuzzy linear programming Generalizirano mehko linearno programiranje Janez Usenik, Maja Žulj . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Assessment of human exposure to electric and magnetic fields near transmission lines using FEMM Ocena izpostavljenosti človeka električnim in magnetnim poljem v bližini daljnovodov z uporabo FEMM Bojan Glushica, Blagoja Markovski, Andrijana Kuhar, Vesna Arnautovski Toseva . . . . . . . . . . 41 Analysis of revitalisation model behaviour for thermal power plants in different geographical areas Analiza odzivanja revitalizacijskega modela termoenergetska postrojenja na različnih geografskih lokacijah Martin Bricl, Jurij Avsec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Design of wfoil 18 albatross with hydrogen technologies Zasnova plovila wfoil 18 albatross z vodikovimi tehnologijami Nejc Zore, Jurij Avsec, Urška Novosel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Instructions for authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 10 JET JET Volume 16 (2023) p.p. 11-22 Issue 1, 2023 Type of article: 1.01 http://www.fe.um.si/si/jet.htm THE IMPACT OF PLUG-IN HYBRID VEHICLES IN LOW-VOLTAGE DISTRIBUTION SYSTEMS USING A MONTE CARLO SIMULATION VPLIV PRIKLJUČNIH HIBRIDNIH VOZIL NA NIZKONAPETOSTNE DISTRIBUCIJSKE SISTEME Z UPORABO METODE MONTE CARLO Evica Smilkoska1, Vasko Zdraveski, Jovica Vuletić, Jordančo Angelov, Mirko Todorovski2 Keywords: Plug-in Hybrid Electric Vehicle, Power Quality, Non-Deterministic Approach, Voltage Deviations, Power Losses, Distribution Systems. Abstract The growing presence and randomness of renewable-based Distributed Generation, such as solar, photovoltaic, and wind power, and heavy Plug-in Hybrid Electric Vehicle loads in residential distribution grids result in both a higher degree of imbalance and a wide range of voltage fluctuations. When increasing the number of Plug-in Hybrid Electric Vehicles that are simultaneously charged, the additional unpredicted load may cause several problems to the current grid in terms of voltage deviations, thermal overloads, power losses, increased aging of transformers and lines, decreased quality of supply, and power outages. This paper proposes an approach that models Plug-in Hybrid Electric Vehicles’ behaviour and performs power flow analysis on CIGRE low voltage benchmark grid to investigate the impact on the current distribution grid. 1 2 Evica Smilkoska, Elektrodistribucija DOOEL, Customer Center (KEC) Gostivar, Str. Goce Delchev no.45 Gostivar, R. N. Macedonia, E-mail: evica.smilkoska@evn.mk Ss. Cyril and Methodius University, Faculty of Electrical Engineering and Information Technologies, Rugjer Boskovic 18, Skopje, R. N. Macedonia, E-mails: vaskoz@pees-feit.edu.mk, jovicav@pees-feit.ukim.edu.mk, jordanco@pees-feit.edu.mk, mirko@pees-feit.edu.mk JET 11 E. Smilkoska, V. Zdraveski, J. Vuletić, J. Angelov and M. Todorovski JET Volume 16 (2023) Issue 1, 2023 Povzetek Vse večja prisotnost proizvodnje, ki temelji na obnovljivih virih energije, kot je sončna, fotovoltaična in vetrna energija, njena naključna porazdeljenost ter velike obremenitve priključnih hibridnih električnih vozil (EV) v stanovanjskih distribucijskih omrežjih povzročajo tako višjo stopnjo neravnovesja kot širok razpon nihanj napetosti. S povečanjem števila priključnih hibridnih EV, ki se sočasno polnijo, lahko dodatna nepredvidljiva obremenitev povzroči več težav trenutnemu omrežju – to so odstopanja napetosti, toplotne preobremenitve, izguba moči, hitrejše staranje transformatorjev in vodov ter zmanjšana kakovost oskrbe in izpad električne energije. V članku predlagamo pristop, ki modelira obnašanje priključnih hibridnih električnih vozil in izvaja analizo pretoka moči na nizkonapetostnem referenčnem omrežju CIGRE ter na ta način omogoča raziskavo vplivov EV na trenutno distribucijsko omrežje. 1 INTRODUCTION Distribution System Operators (DSOs) are responsible for operating their grid to follow a predicted demand with unidirectional power flows only. Most of the conventional distribution grids are of the radial type with different configurations and loads. They have one objective: to offer a quality of supply under certain technical and economic parameters that offer efficient and reliable grid operation. [1]-[2] Due to the fast development of power electronic technologies, the presence of Distributed Generation (DG) and connected Plug-in Hybrid Electric Vehicles (PHEVs), the bi/multidirectional power flow distribution grid is growing rapidly, which raises the question: Are the current conventional distribution grids ready for these new rapidly-growing types of loads? [3] The advancements in transportation electrification have changed the structure of traditional car manufacturing processes. This kind of rapid and increased development in the transportation electrification sector requires large-scale research and evaluation in order to measure the capability of the current conventional distribution systems to withstand the increased presence of PHEVs. [4] PHEVs are continuously opening up new perspectives and numerous possibilities. [5] These types of vehicles currently present on the market not only reduce pollution, but can also help in conserving natural resources. PHEV technology is one of the most promising forms of technology for reducing petroleum consumption associated with reducing the use of internal combustion engine vehicles, and they are seen as an opportunity to provide environmentally-friendly vehicles for transportation that do not release greenhouse gases into the atmosphere or cause smog. From an energy policy point of view, electro-mobility offers the opportunity to achieve the objectives of decarbonisation and decentralisation of electricity sources. [6] As one of the types of Electric Vehicles (EVs), PHEVs are recharged through a plug connected to the electric power grid. [4] Hence, PHEVs are changing the conventional load profile. [7]-[8] The main issues caused by their growing presence are mainly related to power quality. Power quality is a predominant aspect of the efficiency and security of grids and is likely to be strongly affected by PHEV development over the forthcoming years. [9] ‘Power Quality’ refers to providing a near sinusoidal voltage and current waveforms for the power grid at the rated magnitude and frequency. [10] Factors such as voltage and frequency variations, imbalance, interruption, flicker, and harmonics can determine power quality. As the number of PHEVs that are randomly charged on the grid is increasing rapidly, the unpredicted load profile 12 JET The Impact of Plug-In Hybrid Vehicles in Low-Voltage Distribution Systems Using a Monte Carlo Simulation may pose several problems to the current conventional grid in terms of voltage deviations, thermal overloads, power losses, increased aging of transformers and lines, decreased quality of supply and power outages. It is thus of great importance to investigate power quality concerns in distribution grids when considering PHEVs. The impact of PHEVs on the grid’s parameters can be consequential or inconsequential depending on the number of PHEVs attached to the grid, the grid’s characteristics, and the PHEV’s charging features. To conclude that supplied energy is of acceptable quality, the parameters that define it must be within limits defined by the DSO distribution regulation. [11] With the increased presence of PHEVs, and moving beyond the aforementioned problems associated with the quality of the distributed electric energy, the problem relating to the increased aging of transformers and lines is also significant. The solution to this problem is mainly focused on grid reinforcement. Researchers studying this problem have concluded that a large economic investment will be needed for the proposed solution. Different studies have proposed strategies as an economical alternative to grid reinforcement. [1] One of the proposed strategies involves PHEV charging schemes as an alternative for supporting the grid and enhancing both the efficiency and the reliability of the distribution grid. Numerous research studies show that intelligent integration, namely smart PHEV charging, can lower the impact on the power grid or provide different ancillary services. [12] The ancillary services provided by PHEVs are associated with the mode of discharging their batteries, i.e. discharging the stored energy for peak power shaving and spinning reserves. [13] On the other hand, the available energy stored in PHEVs can relieve the distribution grid from overloading at certain times or allow the grid to charge more PHEVs at any time of the day, including during peak hours. Introducing storage devices like PHEVs may result in revolutionary changes to the distribution grid, [14] such as voltage support, providing backup power in case of interruption, reducing losses, and postponing the need for distribution grid reinforcements. The way the distribution grid is connected and operated to provide power to a load that changes every minute requires a time analysis to see the effect on the grid, especially with changing household loading and the timing of PHEVs cycles of charging and discharging or, in other words, demand response. [15] The main purpose of this paper is to analyse a specific grid configuration where feeders, conductors, transformers and substations, DGs, and PHEVs perform well while simultaneously maintaining a radial configuration and the desired supply quality. [16] 2 PROBLEM FORMULATION The problem of connecting the injections generated by PHEVs in the distribution grid for 24-hour analysed intervals and analysing the power quality parameters is defined in this section using MATLAB functions. The PHEV types used in this simulation are defined in Table 1. [8] There are four different groups of PHEVs, with each group containing three different PHEVs according to their All-Electric Range (AER). The AER is defined as the possible distance driven by a PHEV with a fully charged battery. [4] Table 1 also shows the battery capacity of PHEVs with an AER of 48, 64, and 96 km, respectively. The data shows that a PHEV’s battery capacity can vary from 7.78 kWh to 27.44 kWh. In order to precisely define the PHEVs referred to in this paper, the battery’s State of Charge (SOC) has to be determined as one of the required parameters. SOC is a calculation estimate JET 13 E. Smilkoska, V. Zdraveski, J. Vuletić, J. Angelov and M. Todorovski JET Volume 16 (2023) Issue 1, 2023 that gives a rough estimate of the state of energy in the battery pack. [4] This paper defines the battery SOC as a random value between 0.3 and 0.9 of the battery capacity. These values reflect the minimum energy that must be stored in the PHEV’s battery and the maximum energy up to which the PHEV’s battery can be charged. Table 1: PHEVs battery capacity data Vehicle type PHEV48[kWh] PHEV64[kWh] PHEV96[kWh] Compact sedan 7.78 10.34 15.51 Mid-size sedan 8.95 11.93 17.89 Mid-size SUV 11.33 15.11 22.67 Full-size SUV 13.72 18.29 27.44 If the battery SOC of the PHEV is < 0.5, the vehicle attached to the grid has be charged or, in other words, take energy from the grid. Conversely, if the battery SOC is > 0.5 and < 0.9, then the vehicle must discharge or inject energy into the grid. The following parameters defining the PHEVs are the arrival and departure times of PHEVs. The arrival and departure times determine their availability during the 24-hour analysed interval. The arrival time and departure time of the PHEVs have been randomly chosen from real-life databases. [17] Suppose the value of the departure time is lower than that of the arrival time. In this case, the departure time of the vehicle is considered to be within the next day, which falls outside of the analysed interval. The departure time is thus rounded up to midnight or the last hour of the analysed interval. After determining the needed parameters, we can generate the injection of the PHEVs during the 24-hour analysed interval. 14 JET The Impact of Plug-In Hybrid Vehicles in Low-Voltage Distribution Systems Using a Monte Carlo Simulation In terms of the grid load, the paper uses real-life data from the site Elektrodistribucija DOOEL. [18] The loading data applies to households with and without electric heating during 2021. Annual data for the scale of 24-hour distribution has been extracted for this simulation. Figure 1 presents a daily diagram of the households loading with electric heating and without electric heating, respectively, during 24 hours with its minimum, maximum, and mean values according to the legends shown on the diagrams. Based on the analysis, the load curves connected to the grid nodes are randomly selected between the highest and lowest values from the load profile curve area shown in Figure 1. Considering all of the uncertain variables in this paper, a Monte Carlo simulation is used to solve the power flow analysis in each iteration. A new loading curve is generated for every grid node, and the methodology is repeated for every iteration. The characteristic values that determine the loading data are presented in Table 2. It can be noticed that the loading values attached to the grid are within the interval of 0.9914 kW to 8.1298 kW for households with electric heating. While again, for households without electric heating, the loading values attached to the grid are within the interval of 1.6492 kW to 6.0206 kW. In this paper, in order to analyse the injection of PHEVs into the distribution grid and the characteristics that define the power quality, the CIGRE benchmark low voltage grid is used. [20] The grid’s topology is presented in Figure 2, with household loads connected to every grid node. JET 15 E. Smilkoska, V. Zdraveski, J. Vuletić, J. Angelov and M. Todorovski JET Volume 16 (2023) Issue 1, 2023 Figure 2: CIGRE Benchmark low voltage grid Table 2: Household loading data hno 1 2 3 4 5 6 7 8 9 10 11 16 JET With electric heating min [kW] max [kW] mean [kW] 1.3883 7.4191 3.6039 1.1536 6.5703 3.0390 1.0278 5.7731 2.6180 0.9914 5.1797 2.3705 1.0332 4.7751 2.3439 1.0819 4.7651 2.5352 1.1811 4.9939 2.7336 1.3583 4.8876 2.8093 1.5612 5.2129 2.9471 1.7215 5.7407 3.1316 1.8143 6.2004 3.2678 Without electric heating min [kW] max [kW] mean [kW] 2.3096 4.2115 3.0264 1.9192 3.3929 2.4341 1.7099 2.7751 2.0563 1.6492 2.3962 1.8760 1.6969 2.2351 1.9304 1.7812 2.8479 2.2125 1.9385 3.0982 2.5695 2.1587 3.3362 2.8082 2.5006 3.9948 3.1012 2.8639 4.4958 3.3943 3.0182 4.9054 3.6079 The Impact of Plug-In Hybrid Vehicles in Low-Voltage Distribution Systems Using a Monte Carlo Simulation 12 13 14 15 16 17 18 19 20 21 22 23 24 1.8520 1.8315 1.8228 1.8376 1.8596 1.8909 1.9282 2.0656 2.2005 2.2284 2.2481 2.0472 1.7388 6.4862 6.5069 6.4792 6.7738 6.8856 6.9139 7.1817 7.3305 7.3505 7.3101 7.2631 7.6929 8.1298 3.3325 3.3030 3.3098 3.4915 3.5979 3.6771 3.8842 4.0904 4.1649 4.1181 4.1809 4.4291 4.1697 3.0810 3.0469 3.0324 3.0571 3.0936 3.1458 3.2078 3.4363 3.6608 3.7072 3.7400 3.4057 2.8927 5.3181 5.4679 5.4789 5.4663 5.4246 5.5919 5.9616 6.0206 5.8126 5.5252 5.3398 5.2919 5.0012 3.7169 3.6963 3.6669 3.7338 3.8048 3.9519 4.2007 4.4399 4.5026 4.3869 4.3885 4.3145 3.7669 The Power Flow analysis of the low-voltage distribution grid is made using a suitable mathematical model. [21] The Power Flow analysis determines the power distribution in the grid branches and voltages in the grid’s nodes. 3 CASE STUDY The case study consists of two different case studies depending on the loading attached to the grid. Case One consists of loading data with electric heating, while Case Two consists of loading data without electric heating. The simulation for each case is performed once when there are PHEVs injections attached to the distribution grid and once when there are no PHEVs injections attached to the distribution grid in order to compare the results between the two Cases for the branch’s active power loss and node voltage drop. For every node of the CIGRE Benchmark low voltage distribution grid, a new injection for the 24-hour analysed interval from one randomly chosen PHEV is created, and a new curve for the loading profile is generated depending on the analysed case. Since the grid has 18 nodes, 17 new PHEV injections are generated, 17 different loading profiles are generated, and one power flow analysis is performed. Node R1 does not form part of the analysis. The result from one iteration is a 24-hour probability distribution (PD) for the branch’s active power loss and the node’s voltage drop interval. The simulation for Case One with PHEV injections attached to the distribution grid and Case One without PHEV injections attached to the distribution grid is performed 10,000 times to provide detailed information regarding the PD of the branch’s active power losses and the node voltage magnitudes. The same procedure is then repeated for Case Two. As mentioned earlier, this paper considers the Monte Carlo method for solving the power flow simulation. The values subject to analysis are randomly sampled during a Monte Carlo simulation. Each set of samples is called an iteration, and the resulting outcome from each sample is recorded. Here, the results recorded are the branch active power losses and node voltages. With the Monte Carlo simulation performed hundreds or thousands of times, the result is a probability distribution of possible outcome values of the branch active power losses and node voltages. As a result, the Monte Carlo simulation provides a much more comprehensive view of what may happen. JET 17 E. Smilkoska, V. Zdraveski, J. Vuletić, J. Angelov and M. Todorovski JET Volume 16 (2023) Issue 1, 2023 The desired output of the power flow analysis is the domain of the active power losses in the grid, presented by its min, max, and mean values, and the domain of the voltages in the nodes, respectively. It is expected that when the active power loss value in the grid is maximum, the node voltages values are minimum due to high values of the loading. The comprehensive presentation of the generated PHEV injections represented by their minimum, maximum, and mean values is presented in Figure 3. Figure 3: Domain of the generated PHEVs injections From the presented data of the generated injections, we note that the domain of the PHEVs attached to the grid is between 24.6939 kW and -13.7191 kW. The results for active power losses and node voltages for Case One after the simulation are presented in Figure 4 and Figure 5, respectively. Figure 4: Active power losses - left without PHEVs, right with PHEVs – Case One (with electric heating) 18 JET The Impact of Plug-In Hybrid Vehicles in Low-Voltage Distribution Systems Using a Monte Carlo Simulation Figure 5: Histogram of node voltages - left without PHEVs, right with PHEVs – Case One (with electric heating) Next is the simulation for Case Two. The results for active power losses and node voltages for Case Two are presented in Figure 6 and Figure 7, respectively. Figure 6: Active power losses - left without PHEVs, right with PHEVs – Case Two (without electric heating) Figure 7: Histogram of node voltages - left without PHEVs, right with PHEVs – Case Two (without electric heating) JET 19 E. Smilkoska, V. Zdraveski, J. Vuletić, J. Angelov and M. Todorovski JET Volume 16 (2023) Issue 1, 2023 From the presented results for Case One, the domain of the grid active power losses with and without PHEVs is mainly overlapped. The domain of the active power losses consists of larger values when no PHEVs are connected to the grid, which is unlike when PHEVs are connected to the grid, as confirmed by the presented results. When we analyse the scenario without PHEVs, the curves of the active power losses generally follow the curve of the loading profile, something which is not the case when we analyse the scenario with connected PHEVs. In such cases, the active power losses curve follows the same trend but with certain peak shaving, depending on the PHEVs injections. As for the results of the node voltages for Case One and the given constraints, almost all are beneath the nominal grid voltage (0.4 kV). However, besides this, all of the values are in the DSOs given constraints of ΔU = ± 10%, with and without connected PHEVs, respectively. From the presented results, we note a deviation of voltage magnitudes, which is more significant when PHEVs are connected to the grid and somewhat smaller when PHEVs are absent. When PHEVs are connected, the distribution grid performs well while maintaining both a radial configuration and the desired supply quality as defined by the DSO distribution regulation. Unlike Case One, Case Two is characterised by a different domain of the household loading curves, which means that the domain of the grid active power losses with and without PHEVs will differ. The domain of the active power losses in Case Two consists of slightly larger values than in Case One. According to the presented results, it is characterised by the same diversity both when PHEVs are connected to the grid and when PHEVs are absent. As for the results of the node voltages for Case Two, a difference in voltage magnitudes is noted from the presented results. When PHEVs are absent, the voltage magnitudes are lower the nominal grid voltage (0.4 kV), but nevertheless fulfil the DSO’s given constraints of ΔU = ± 10%. This is not the case when PHEVs are connected to the grid. In this case, one node, Node No 14, did not fulfil the DSOs given constraints ΔU = ± 10%. All the other voltage magnitudes are beneath the nominal grid voltage (0.4 kV). In this case, the households connected to that node will face a slight malfunction resulting in lowered power quality determined by several factors, such as voltage and frequency variations, imbalance, interruption, and flicker. 4 CONCLUSION The increasing presence of PHEVs in daily life is inevitable. Their presence in the years that follow will increase exponentially. According to the presented results, PHEVs will impact the current distribution grid. These impacts can be significant or insignificant, depending on the number of PHEVs attached to the grid, grid characteristics, and PHEV charging features. This is despite the negative impact of PHEVs’ charging/discharging cycles on battery life. Technical and economic factors must also be considered when reducing the impact of PHEVs on the distribution grid. The proposed methods align with integrating new charging schemes and coordinating their charging and discharging cycles. [22] With the smart charging of PHEVs, the peak from charging PHEVs will be shifted to periods with a lower peak from the household loading. The characteristic of PHEV for bi/multi-directional power flow can be used as a strategy for regulating the grid voltage. The active power control can also adjust the operation of PHEV charging, while the reactive power control can inject reactive power into the grid to support the network voltage. The proposed methods should be the subject of further research. 20 JET The Impact of Plug-In Hybrid Vehicles in Low-Voltage Distribution Systems Using a Monte Carlo Simulation References JET 21 E. Smilkoska, V. Zdraveski, J. Vuletić, J. Angelov and M. Todorovski 22 JET JET Volume 16 (2023) Issue 1, 2023 JET Volume 16 (2023) p.p. 23-40 Issue 1, 2023 Type of article: 1.01 http://www.fe.um.si/si/jet.htm GENERALISED FUZZY LINEAR PROGRAMMING GENERALIZIRANO MEHKO LINEARNO PROGRAMIRANJE Janez UsenikR , Maja Žulj14 3 Keywords: linear programming, fuzzy linear programming, generalised linear programming, generalised fuzzy linear programming Abstract Linear programming is one of the widely used methods for optimising business systems, which includes organisational, financial, logistic and control subsystems of energy systems in general. It is possible to express numerous real-world problems in a form of linear program and then solve by simplex method [1]. In the development of linear programming, we are facing a number of upgrades and generalisations, as well as replenishment. Particularly interesting in recent years is an option that decision variables and coefficients are fuzzy numbers. In this case we are dealing with fuzzy linear programming. If we also include in a fuzzy linear program a generalisation with respect to Wolfe’s modified simplex method [1], we obtain a generalised fuzzy linear program (GFLP). Usenik and Žulj introduced methods for solving those programs and proved the existence of the optimal solution in [2]. In the article, the simplex algorithm which enables the determining of an optimal solution for GFLP is described. There is a numerical example at the end of the article that illustrates the algorithm. Povzetek Linearno programiranje je najbolj uporabljena metoda optimizacije poslovnih sistemov, med katere štejemo tudi organizacijske, finančne, logistične in nasploh upravljalne podsisteme energetskega sistema. Veliko praktičnih problemov je mogoče izraziti v obliki linearnega programa, ki ga nato rešimo s simpleksno metodo [1]. Razvoj linearnega programiranja je doživel vrsto nadgradenj, posplošitev in dopolnitev. V zadnjih letih je še posebej zanimiva možnost, da so odločitvene spremenljivke in koeficienti mehka števila – v tem primeru gre za mehko linearno programiranje. Ko pa v ta program uvedemo še pojem generalizacije v Wolfejev pomenu [1], govorimo o generaliziranem mehkem linearnem programiranju (GMLP). Usenik in Žulj [2] sta razvila postopke reševanja takšnih programov in dokazala eksistenco optimalne rešitve. V članku opišemo algoritem simpleksnega postopka za GMLP, ki omogoča izračun optimalne rešitve, in na koncu dodamo numerični primer, ki ilustrira izvedeni algoritem. R 3 Corresponding author: Prof. Janez Usenik, PhD, Tel.: +38640 647 686, E-mail address: janez.usenik@guest.um.si 14 University of Maribor, Faculty of Energy Technology, Hočevarjev trg 1, 8270 Krško, Slovenia, E-mail address: maja.zulj@um.si JET 23 Janez Usenik, Maja Žulj 1 JET Volume 16 (2023) Issue 1, 2023 INTRODUCTION Linear programming is one of the most frequently used techniques in operations research, introduced in 1939 by Russian mathematician Leonid Vitalijevič Kantorovič, who also proposed a method for solving it. Between 1946 and 1947, American mathematician Georg Bernard Dantzig defined a general formulation of linear programming. In 1947, he introduced the so-called simplex method, a method that enables the successful solving of any linear programming problem [1]. Linear programming can be used in economic science and in the management of business or organisational systems, as well as in actions like production planning, the optimisation of the technological process, an optimal logistics service, optimal outsourcing, etc. Linear programming proved to be of considerable applicative importance at the time computers became more capable. Nowadays, a variety of competent computer software programs exist that even enable problems of enormous dimensions to be easily solved. The theory of linear programming is developing in different ways. Let us point out two alternatives in this field. In the first alternative we use a dynamic approach, where we study the optimal behaviour of variables, which are functions of time in this approach. This problem is called continuous variable dynamic linear programming [3], [4]. In [5] we can find a generalisation of c/b/A-continuous variable dynamic linear programming in the sense of Wolfe generalisation [1]. This generalisation is based on the condition that elements of some columns of matrix A(t ) , at the time of formulating the problem, are unknown, but linked convexly in columns. In this case, we talk about generalised continuous variable dynamic linear programming. The second alternative, which has attracted a lot of interest, especially in the last 20 years, is linear programming in conditions represented by fuzzy logic. In this matter, we are dealing with fuzzy linear programming. It is a tool for modelling imprecise data and it is based on fuzzy sets [6]. In 1978, Zimmermann proposed the formulation of fuzzy linear programming problems in [7]. Since then, researchers have developed a relatively large number of different methods to solve such problems. It also turns out that there are no obstacles for generalisation in fuzzy linear programming. In this case, we talk about generalised fuzzy linear programming. Usenik and Žulj introduced methods for solving those programs and proved the existence of the optimal solution in [2]. 24 JET Generalised fuzzy linear programming 2.2 Fuzzy linear programming (2.1) JET 25 Janez Usenik, Maja Žulj JET Volume 16 (2023) Issue 1, 2023 (2.2) 3 GENERALISED FUZZY LINEAR PROGRAMMING In the article we are dealing with the generalisation of fuzzy linear programming in accordance with the Wolfe approach [1], [3], [5]. Therefore, we tackle the problem concerning a linear program where technological coefficients and coefficients in an objective function are not precisely known. But we know that these coefficients are integrated in some known convex composition, i.e., the limited material, financial, logistic, energy, ecological or human resource that is required to produce some product, service, or similar. Consider the fully fuzzy linear program in standard and canonical form: 26 JET Generalised fuzzy linear programming JET 27 Janez Usenik, Maja Žulj 28 JET JET Volume 16 (2023) Issue 1, 2023 Generalised fuzzy linear programming 3.2 Initial feasible solution Solving of the generalised fuzzy linear program is based on Dantzig simplex algorithm and Wolfe’s modified simplex method. Thus, we solve the problem in two phases. In the first phase we look for an optimal feasible basic solution to problem (3.03) without varying vectors JET 29 Janez Usenik, Maja Žulj 30 JET JET Volume 16 (2023) Issue 1, 2023 Generalised fuzzy linear programming JET 31 Janez Usenik, Maja Žulj 3.4 32 JET Further feasible solutions JET Volume 16 (2023) Issue 1, 2023 Generalised fuzzy linear programming (3,10) JET 33 Janez Usenik, Maja Žulj 3.5 34 JET The existence of the optimal solution JET Volume 16 (2023) Issue 1, 2023 Generalised fuzzy linear programming 3.6 Degenerate solution 3.6 Degenerate solution In the given algorithm, degeneracy is also possible. The approach for solving problems in such cases is briefly described in [2]. 4 NUMERICAL EXAMPLE We want to solve the problem: JET 35 Janez Usenik, Maja Žulj Initial main program without varying columns is of the form: 36 JET JET Volume 16 (2023) Issue 1, 2023 Generalised fuzzy linear programming Modified main program of the first degree: JET 37 Janez Usenik, Maja Žulj 38 JET JET Volume 16 (2023) Issue 1, 2023 Generalised fuzzy linear programming JET 39 40 JET JET Volume 16 (2023) Issue 1, 2023 Type of article: 1.01 JET Volume 16 (2023) p.p. 41-50 http://www.fe.um.si/si/jet.html Issue 1, 2023 Type of article: 1.01 http://www.fe.um.si/si/jet.htm ASSESSMENT OF HUMAN EXPOSURE TO ELECTRIC AND MAGNETIC FIELDS NEAR TRANSMISSION LINES USING FEMM OCENA IZPOSTAVLJENOSTI ČLOVEKA ELEKTRIČNIM IN MAGNETNIM POLJEM V BLIŽINI DALJNOVODOV Z UPORABO FEMM Bojan Glushica1, Blagoja Markovski1, Andrijana Kuhar1, Vesna Arnautovski Toseva1 Keywords: finite elements method, transmission lines, electric field, magnetic field, electromagnetic computation Abstract The intensity of ELF electric and magnetic fields near transmission lines is of particular interest in environmental and equipment protection studies. The use of numerical tools is the most efficient method for their assessment. In this paper, we numerically compute the electric and magnetic fields near different configurations of high-voltage transmission lines using the open- source software FEMM 4.2. Computed fields are compared with reference levels related to human exposure to electromagnetic fields. The accuracy of the applied method is validated with published, numerically computed and measured results.  Corresponding author: M.Sc. Bojan Glushica, Ss. Cyril and Methodius University in Skopje, Faculty of Electrical Engineering and Information Technologies, Rugjer Boshkovikj 18, Skopje 1000, North Macedonia, Tel.: +389 71 326 521, E-mail address: glushica@feit.ukim.edu.mk 1 Ss. Cyril and Methodius University in Skopje, Faculty of Electrical Engineering and Information Technologies, Rugjer Boshkovikj 18, Skopje 1000, North Macedonia JET 41 1 Bojan Glushica, Blagoja Markovski, Andrijana Kuhar, Vesna Arnautovski Toseva JET Volume 16 (2023) Issue 1, 2023 Povzetek Intenzivnost električnih in magnetnih polj ELF v bližini daljnovodov je še posebej zanimiva za študije, ki so povezane z zaščito okolja in opreme. Uporabo numeričnih orodij lahko štejemo kot najučinkovitejšo metodo za njihovo ocenjevanje. V članku podamo prikaz numerično izračunanega električnega in magnetnega polja v bližini različnih konfiguracij visokonapetostnih daljnovodov z uporabo odprtokodne programske opreme FEMM 4.2. Izračunana elektromagnetna polja nato primerjamo z referenčnimi ravnmi, ki so povezane z izpostavljenostjo človeka elektromagnetnim poljem. Na koncu potrdimo natančnost uporabljene metode s podanimi numerično izračunanimi in merilnimi rezultati. 1 INTRODUCTION Overhead transmission lines (OTL) generate extremely low frequency (ELF) electric and magnetic fields that may interact with technical or biological systems and produce possible harmful effects in case of excessive exposure [1], [2]. Therefore, the intensity and distribution of electric and magnetic fields near OTL are of particular interest in studies related to their possible adverse effects on the environment, human health, sensitive electronic equipment and critical infrastructures. To address the variety of problems that can occur, numerous standards and protocols have been introduced that define methods for assessment and protection from the effects of electromagnetic fields [3]-[5]. The use of electromagnetic simulation tools can be considered the most efficient method, especially when dealing with large and complex systems where measuring procedures can be time-consuming, expensive or impractical. Another advantage of the simulation tools is in the possibility of analysing systems in the initial phase of their planning and construction, and the ability to test the effectiveness of different protection techniques. In this paper, we perform numerical analysis of the intensity and distribution of ELF electric and magnetic fields in the vicinity of OTL using the open-source software for analysing electromagnetic problems, FEMM 4.2, which is based on the finite element method (FEM) [6][8]. The modelling procedure is briefly described and validated using a full-wave electromagnetic model based on the method of moments (MoM) and by comparison of published and measured results. The analysis should provide general information for the expected field levels near 110 kV and 400 kV OTL. Therefore, different configurations of OTL and effectiveness of phase sequence transposition in double-circuit OTL are considered. Computed electric and magnetic field levels are compared with reference levels for human exposure to electromagnetic fields, established by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) [9]. 2 PROCEDURES FOR MODELLING THE ELECTROMAGNETIC PROBLEM IN FEMM Modelling electromagnetic problems in open space using the FEMM 4.2 software requires specifying a solution domain with suitable shape and size for the analysed problem and appropriate boundary conditions at its borders. The solution domain, in which the electromagnetic problem is solved, should have a circular shape. Since the height of the analysed OTL is nearly 40 m, to reduce the boundary’s influence, the domain’s radius is set to 300 m, which is more than seven 42 JET Assessment of human exposure to electric and magnetic fields near transmission FEMM Assessment of human exposure to electriclines and using magnetic fields near transmission lines using FEMM 3 ---------times larger than the height of the analysed OTL. The domain is divided into two sections. The ground, specific conductivity σ, and the top sectionσ,isand air. the The top horizontal of the OTL is at bottomwith section is ground, with specific conductivity sectionposition is air. The horizontal the centreofofthe theOTL domain (corresponding to domain distance(corresponding of 0 m in the tofigures). Because field position is at the centre of the distance of 0 mthe in the computation is a time-consuming process isand because we focus on theand fields above we the focus ground figures). Because the field computation a time-consuming process because onin the of thethe conductors, discretization of the solution domain is done separately the vicinity fields above ground in the vicinity of the conductors, the discretization of the solutionin sections, shownseparately in Fig. 1. The ground has lowest degree of discretization. The air is divided domain as is done in sections, as the shown in Fig. 1. The ground has the lowest degree into of two half circles The withair150 m and 300 radius, wherewith the inner has the highestwhere degree discretization. is divided into m two half circles 150 mcircle and 300 m radius, theof discretization to obtain moredegree accurate The solution domain discretized with about 340,000 inner circle has the highest of results. discretization to obtain moreisaccurate results. The solution nodes or 685,000 elements. domain is discretized with about 340,000 nodes or 685,000 elements. Figure1:1:Different Differentdegrees degreesof ofdiscretization discretization for for the the 110 110 kV Figure kV single-circuit single-circuittransmission transmissionline line The FEMM 4.2 software provides instantaneous values of computed fields (electric or magnetic), The FEMM software provides instantaneous values of exposure computedtofields (electric or fields magnetic), while RMS 4.2 values are further required to estimate human electromagnetic [9]. while RMS values are further required to estimate human exposure to electromagnetic fields To obtain the RMS values, we compute multiple samples of the instantaneous field values over Napaka! Viraofsklicevanja bilo observed mogoče najti.. Toequally obtain spaced the RMSsamples values, over we compute multiple one period 20 ms. Wenihave that 40 one period can samples of the instantaneous field values over one period of 20 ms. We have observed provide a good estimate of the RMS values of the 50 Hz fields. To automate this process that for all40 equally spaced samples over used one period canscripting provide language a good estimate ofincorporated the RMS values of the 50 Hz considered cases, we have the Lua which is in the FEMM fields. To automate this process for all considered cases, we have used the Lua scripting language 4.2 software. The electric and magnetic fields are computed at multiple points at a height of which is incorporated in the FEMM 4.2 software. The electric and magnetic fields are computed at 1 m above ground level, along a profile perpendicular to the centre of the transmission line, multiple points at a height of 1 m above ground level, along a profile perpendicular to the centre of as required by the standard [3]. The above-mentioned procedures are general for calculating the transmission line, as required by the standard [3]. The above-mentioned procedures are general electric and magnetic fields. In the following subsections, we describe some specific procedures for calculating electric and magnetic fields. In the following subsections, we describe some specific for computing the electric magnetic fields. procedures for computing the electric magnetic fields. 2.1 Procedures for obtaining the RMS electric field 2.1 Procedures for obtaining the RMS electric field The electric field and scalar potential are computed using the “Current Flow” module of FEMM 4.2.electric For thisfield module, fixedpotential voltages are are computed required. The condition potentials at the The and scalar usingboundary the “Current Flow” for module of FEMM 4.2. domain’s borders is set to 0 V. The same condition is applied for the ground wires. The phase For this module, fixed voltages are required. The boundary condition for potentials at the domain’s conductors phase voltages thatground correspond appropriate time borders is setare to 0set V. to Theinstantaneous same condition is applied for the wires. to Thethe phase conductors are points within one period 20 ms using a Lua script.toTwo are observed for thewithin doubleset to instantaneous phaseofvoltages that correspond thecases appropriate time points one circuitof power in athe caseTwo thecases phaseareconductors arethe untransposed, and in the second period 20 msline: using Luafirst script. observed for double-circuit power line: in the case they are transposed. The relative dielectric permittivity of the whole domain is ε = 1. first case the phase conductors are untransposed, and in the second case they are transposed. The 1 relative dielectric permittivity of the whole domain is ε1 = 1. JET 43 ---------- 2.2 Procedures for obtaining the RMS magnetic field Bojan Glushica, Blagoja Markovski, Andrijana Kuhar, Vesna Arnautovski Toseva JET Volume 16 (2023) Issue 1, 2023 The magnetic field and magnetic vector potential are computed using FEMM 4.2’s “Magnetics” module. A fixed current strength and magnetic vector potential are required for this module. The 2.2 Procedures for obtaining the RMS magnetic field boundary condition for the magnetic vector potential at the domain’s borders is set to 0 Wb/m. The current strength field in the wire is forced at are 0 A.computed The maximum load 4.2’s current of the TL is The magnetic andground magnetic vector potential using FEMM “Magnetics” considered the current currentstrength strengthand in magnetic the phasevector conductors. values for the module. for A fixed potentialThe are instantaneous required for this module. current strength of each phase are magnetic set basedvector on thepotential time points using a Lua borders script. For thetodoubleThe boundary condition for the at the domain’s is set 0 circuit power thestrength untransposed and transposed cases considered asload well.current The relative Wb/m. The line, current in the ground wire is forced at 0are A. The maximum of magnetic domain is μin 1. phase conductors. The instantaneous values r =the the TL permeability is consideredof forthe thewhole current strength for the current strength of each phase are set based on the time points using a Lua script. For the double-circuit power line, the untransposed and transposed cases are considered as well. The magnetic permeability of theAPPLIED whole domainMETHOD is μr = 1. 3 relative VALIDATION OF THE In this we validate the of the appliedMETHOD method by comparison with published and 3 section, VALIDATION OFaccuracy THE APPLIED numerically computed results. In this section, we validate the accuracy of the applied method by comparison with published and numerically computed results. 3.1 Validation with published results 3.1 Validation with published results Validation of the procedures presented in Section 2 is performed by comparing the simulated results andValidation the results provided in thepresented European 62110:2009 [3] for thethe geometries of the procedures in standard Section 2 IEC is performed by comparing simulated and conditions provided in the standard. For the OTL, a 77 kV transposed double-circuit is considered. results and the results provided in the European standard IEC 62110:2009 [3] for the geometries Theand current strength is assumed to standard. be 200 A. For Thethe same geometry in Table 2 and Fig.is6 for conditions provided in the OTL, a 77 kVprovided transposed double-circuit the considered. transposed The double-circuit OTL without the to ground wire is used (asgeometry specifiedprovided in the standard current strength is assumed be 200 A. The same in Table [3]). and Fig.clearance 6 for the is transposed OTLshown withoutinthe is used (as specified The2ground hg = 11 m.double-circuit The results are Fig.ground 2. The wire differences in the simulated the standard [3]).and Themagnetic ground clearance hg 1= m 11 above m. Theground results level are shown in Fig. 2.toThe andinprovided electric field levelsis at are observed be less in the simulated and provided electric and magnetic field levels at 1 m above ground thandifferences 5%. level are observed to be less than 5%. Figure 2: Comparison between simulated and published results [3], Fig.A.5 A.5and andFig. Fig.B.3) B.3)for a) Figure 2: Comparison between simulated and published results (in(in [3], Fig. forRMS a) RMS electric field and b) RMS magnetic field for double-circuit OTL electric field and b) RMS magnetic field for double-circuit OTL The simulated magnetic field is also validated for underground transmission lines (UTL). A approach, as described in Section 2.2, for is used with different discretization around Thesimilar simulated magnetic field is also validated underground transmission lineslevels (UTL). A similar approach, as described in Section 2.2, is used with different discretization levels around the phase conductors. Double-circuit configuration with balanced 200 A current strength is considered. The 44 JET Assessment of human exposure to electric and magnetic fields near Assessment of human exposure to electric and magnetic fields near transmission lines using FEMM transmission lines using FEMM Assessment of human exposure to electric and magnetic fields near transmission lines using FEMM 55 ------------------phase conductors are placed vertically onconfiguration the same axis with 0.35 m separation, while the horizontal the phase conductors. Double-circuit balanced 200 A current strength is phase conductors are placed vertically on the same axis with 0.35 m separation, while the horizontal separation between the two circuits is 1m (as specified inon thethe standard [3]).with The 0.35 magnetic field levels considered. The phase conductors are placed vertically same axis m separation, separation between thelevel twowere circuits is 1 m (as in thedistances standardbetween [3]). Thethe magnetic levels atwhile 1 m the above ground calculated forspecified two circuits different andfield ground horizontal separation between the is 1 m (as specified in theUTL standard [3]). atlevel: 1 m above ground level were calculated for two different distances between the UTL and ground hg = 1.85 field m and hg = at 0.61m. results of this simulation are shown Fig.different 3, wheredistances less than The magnetic levels m The above ground level were calculated for in two level: hg = is 1.85 m and = 0.6 m. Thehresults ofmthis simulation are shown inofFig. 3,simulation where lessare than 5% error observed. between the UTL andhgground level: = 1.85 and h = 0.6 m. The results this g g 5%shown error isinobserved. Fig. 3, where less than 5% error is observed. Figure3:3:Comparison Comparisonbetween betweensimulated simulated and and published published results Figure results(in (in[3], [3],Fig FigB.10) B.10)for forRMS RMS magnetic field near double-circuit UTL at a depth of a) 1.85 m and b) 0.6 m field near double-circuit a depth of a) 1.85 and 0.6 mfor RMS Figuremagnetic 3: Comparison between simulatedUTL andatpublished results (inm[3], Figb)B.10) magnetic field near double-circuit UTL at a depth of a) 1.85 m and b) 0.6 m 3.2 Validation Validationwith withsimulated simulated results 3.2 results Additional validation hasbeen beenperformed performed 110 single-circuit =m 15(see m 3.2 Validation with simulated results g Additional validation has forfor thethe 110 kV kV single-circuit OTLOTL withwith hg =h15 (see6 Fig. and 2) Table 2) for the electric and magnetic field levels are expressed Fig. and 6 Table for the electric and magnetic field levels (the latter(the are latter expressed in terms of Additional validation has been performed for the 110 kV single-circuit OTL with h = 15 m (see in terms of the magnetic vector potentials). The same problem has also been the magnetic vector potentials). The same problem has also been simulated using gsimulated a full-wave Fig. 6 and Table 2)model for thebased electric magnetic levels (the are expressed using a full-wave electromagnetic model based on the method of moments [10]. Theinresults electromagnetic on and the method offield moments [10].latter The results provided interms Fig. 4of the magnetic vector potentials). The same problem has also been simulated using a full-wave provided in Fig. 4 show excellent agreement, with less than 3% difference in the calculated show excellent agreement, with less than 3% difference in the calculated electric and magnetic electromagnetic model based on the method of moments [10]. The results provided in Fig. 4 electric and magnetic field levels. field levels. show excellent agreement, with less than 3% difference in the calculated electric and magnetic field levels. Figure 4: Verification of the calculated RMS values of a) electric field and b) magnetic vector Figure 4: Verification of the calculated RMS values ofwith a) electric field and b)MoM magnetic vector potential for 110 kV single-circuit transmission line an independent approach potential for 110 kV single-circuit transmission line with an independent MoM approach Figure 4: Verification of the calculated RMS values of a) electric field and b) magnetic vector potential for 110 kV single-circuit transmission line with an independent MoM approach JET 45 6 Bojan Glushica, Blagoja Markovski, Andrijana Kuhar, Vesna Arnautovski Toseva JET Vol. 16 (2023) Issue 1 JET Volume 16 (2023) Issue 1, 2023 Bojan Glushica, Blagoja Markovski, Andrijana Kuhar, Vesna Arnautovski Toseva ---------- 3.3 Validation with measurement results 3.3 Validation with measurement results The numerical results obtained in FEMM are also validated with measured values for the electric and The numerical results obtained in FEMM are also validated with measured values for the electric magnetic field near OTL. The OTL in question is a 110 kV single-circuit tower with the position of the and magnetic field near OTL. The OTL in question is a 110 kV single-circuit tower with the position conductors provided in Table 1 (x values with respect to the centre of the OTL and y values with of the conductors provided in Table 1 (x values with respect to the centre of the OTL and y values respect to ground level). The measurements were performed with a NARDA EFA-300 field analyser with respect to ground level). The measurements were performed with a NARDA EFA-300 field with suitable probes for electric and magnetic field measurement, and the positions provided in analyser with suitable probes for electric and magnetic field measurement, and the positions Table 1 were obtained by obtained laser distance When theWhen measurements were taking provided in Table 1 were by lasermeter. distance meter. the measurements were place, taking the current strength of the conductors was nearly 100 A. place, the current strength of the conductors was nearly 100 A. Table 1: Position of the phase conductors and ground wire for the 110 kV single-circuit OTL Conductor 110 kV single-circuit x [m] y [m] Phase A 3.53 7.75 Phase B -3.07 9.55 Phase C 2.58 11.8 GW 0 17.5 Figure 5: Comparison between simulated and measured results for a) RMS electric field and b) RMSsimulated magnetic and fieldmeasured for a single-circuit tower Figure 5: Comparison between results for a) RMS electric field and b) RMS magnetic field for a single-circuit tower Fig. 5 shows the comparison between simulation and measurement results for the electric and magnetic fields at a height of 1 m from ground level, along a path perpendicular to the OTL, as Fig.required 5 shows comparison simulation measurement resultsis for theobserved electric and by the the standard [3]. Abetween good agreement withand a 5% difference in values mostly magnetic fields atand a height of fields, 1 m from toThe theerror OTL, as for the electric magnetic whileground at somelevel, pointsalong thereaispath up toperpendicular 20% difference. required the standard [3].influence A good agreement with a 5% 110 difference in values isOTL mostly may bebyexplained by the of a nearby parallel kV single-circuit at a observed distance for theofelectric magnetic whileOTL. at some points there is up 20% difference. The error nearlyand 40 m from thefields, analysed A better agreement of to results could be expected if may the be contribution the second was considered. explained by theofinfluence of OTL a nearby parallel 110 kV single-circuit OTL at a distance of nearly 40 m from the analysed OTL. A better agreement of results could be expected if the contribution of the second 46 JETOTL was considered. Assessment of human exposure to electric and magnetic fields near transmission lines using FEMM 7 Assessment of human exposure to electric and magnetic fields near transmission lines using FEMM ---------- 44 PARAMETRICANALYSIS: ANALYSIS:RESULTS RESULTS AND DISCUSSION PARAMETRIC AND DISCUSSION The subject subject of of analysis The analysis are are 110 110 kV kV single-circuit, single-circuit, 110 110 kV kV double-circuit, double-circuit, and and 400 400 kV kV single-circuit single-circuit overheadtransmission transmissionlines. lines.Details Details positions of the phase conductors and ground wire overhead forfor thethe positions of the phase conductors and ground wire (GW) (GW) are provided Fig.Table 6 and2.Table 2. The cross-sectional area conductor of each conductor the 110 are provided in Fig. 6inand The cross-sectional area of each of the 110ofkV OTL is 2 kV OTL 104 mm mmdiameter). (11.5 mmFor diameter). thethe 400 kV OTL, the area cross-sectional of the 104 mm2is(11.5 the 400 kVFor OTL, cross-sectional of the phasearea conductors phase conductors is 2mm x 245 mm2 (17.66 each) withof a mutual separation of 30 cm;it is 2 x 245 mm2 (17.66 diameter each) mm with diameter a mutual separation 30 cm; for the ground wire, 2 2 is (12.36 mmitdiameter). on each conductor’sBased previously mentioned surface area, the for120 themm ground wire, is 120 mmBased (12.36 mm diameter). on each conductor’s previously maximum current for the eachmaximum phase conductor is 800 for A and 1,920 A for the 110 kV and 400 kV mentionedload surface area, load current each phase conductor is 800 A and towers, Theand parameter hg represents the shortest distance between the conductors and 1,920 Arespectively. for the 110 kV 400 kV towers, respectively. The parameter hg represents the shortest the ground level. Inthe ourconductors analysis, weand consider two values m and 15we m.consider We assume with g: 30analysis, distance between the ground level.ofInhour twoearth values of specific σ assume = 0.01 S/m. problems haveS/m. been analysed following hg: 30 mconductivity and 15 m. We earthThe withelectromagnetic specific conductivity σ = 0.01 The electromagnetic similar procedures described in [11]. problems have been analysed following similar procedures described in [11]. Table 2: Position of the phaseconductors conductors and and ground thethe 110110 kV kV single-circuit, Table 2: Position of the phase groundwires wiresforfor single-circuit, 110double-circuit kV double-circuit and 400 overhead transmission transmission lines 110 kV and 400 kVkVoverhead lines Conductor Phase A Phase B Phase C GW 110 kV single-circuit x [m] y [m] 4.8 -4.1 3.4 0 hg hg +2.4 hg +4.8 hg +11 110 kV double-circuit x1 / x2 [m] y [m] -3.2 / 3.2 -3.5 / 3.5 -3.8 / 3.8 0 hg +6 hg +3 hg hg +9 400 kV single-circuit x [m] y [m] -8.47 0 8.47 -5.07 / 5.07 hg hg hg hg +4.45 Figure 6: Configuration of the analysed 110 kV and 400 kV overhead transmission lines Here we provide the simulation results for electric and magnetic fields for the different OTL configurations described in Fig. 6results and Table and we thefields results reference Here we provide the simulation for 2, electric andcompare magnetic forwith the the different OTL levels for human exposure to 6electromagnetic provided ICNIRP [9]. electriclevels and configurations described in Fig. and Table 2, andfields we compare theby results with theThe reference magnetic are computed at multiple points at a height of 1 m[9]. above along a for humanfields exposure to electromagnetic fields provided by ICNIRP The ground electric level, and magnetic profileare perpendicular the centre of the required by the standard The fields computed atto multiple points at transmission a height of line, 1 m as above ground level, along a[3]. profile reference levels public exposure to the field at Hzstandard are set to[3]. 5 kV/m, and the perpendicular to for thegeneral centre of the transmission line,electric as required by50 the The reference magnetic field at public the same frequency set to 200 ground of and the transmission levels for general exposure to theiselectric fieldμT. at For 50 Hz are setclearance to 5 kV/m, the magnetic field the same set to are 200represented μT. For ground of the lines equalare to linesat equal to hg =frequency 30 m, theisresults by clearance dashed lines; fortransmission hg = 15 m, the results hrepresented results are represented by dashed lines; for hg = 15 m, the results are represented by solid lines. g = 30 m, theby solid lines. In Fig. 7, the results of the electric and magnetic fields for the single-circuit OTL are shown. It is observed the of maximum value of magnetic the electric field thesingle-circuit 400 kV OTLOTL is 1.68 lower In Fig. 7, thethat results the electric and fields forforthe are times shown. It is than the that reference levels, and forofthe kV OTL, 12.2 times lower for times the hglower = 15 than m case. observed the maximum value the110 electric field it foristhe 400 kV OTL is 1.68 the reference levels, and for the 110 kV OTL, it is 12.2 times lower for the hg = 15 m case. In comparison, JET 47 8 BojanGlushica, Glushica,Blagoja Blagoja Markovski, Markovski, Andrijana Andrijana Kuhar, Bojan Kuhar,Vesna Arnautovski Toseva Vesna Arnautovski Toseva Vol. 16 16 (2023) (2023) JET JET Volume Issue 1,Issue 20231 ---------In comparison, the values are further reduced by a factor of 3.54 for the hg = 30 m case. The maximum values of the electric appear close thehorigin at xcase. = 0 m, below the OTL’s the values are further reduced byfield a factor of 3.54 fortothe Thedirectly maximum values of the g = 30 m centralfield axis.appear The 400 kV tower an exception, at below x = 0 athe sharp drop of the RMS electric close to the is origin at x = 0 m,where directly OTL’s central axis. Theelectric 400 kV field isisobserved mainly due at to xthe of of thethe fields each phase one period. However, tower an exception, where = 0annulment a sharp drop RMSofelectric field isinobserved mainly due to theannulment range between m and 20 mphase distance on the x-axis is of concern where the highest the of the10 fields of each in one period. However, the range between 10 m values and 20 the electric system’s geometry described Table 2, field this isappear. close mof distance on field the appear. x-axis isConsidering of concern the where the highest values of thein electric to the shortest ground level and 2, thethis nearest phase conductor. reality, Considering the distance system’s between geometrythe described in Table is close to the shortestIn distance between theofground level and may the nearest reality, height aoflower the conductors the height the conductors be lowerphase alongconductor. the powerInline. If wethe consider value for may be lower along the power we consider lower for OTL hg, which is not constant along hg, which is not constant alongline. theIflength of the aOTL, thevalue 400 kV can represent a potential the of thehealth. OTL, the 400 kV OTL can represent a potential risk to human health. risklength to human Themaximum maximummagnetic magneticfield fieldvalue value the 400 OTL is 9.4 times lower, kV OTL The forfor the 400 kVkV OTL is 9.4 times lower, andand forfor thethe 110110 kV OTL it is it istimes 68 times the reference for hthe h = 15 m case. For the h = 30 m case, there 68 lowerlower than than the reference levelslevels for the = 15 m case. For the h = 30 m case, there is a g g g g further decrease by a factor of 3.6.of 3.6. is a further decrease by a factor Fig. electric and and magnetic magnetic fields fields for for the thedouble-circuit double-circuit towers. towers.The The Fig.88 provides provides the the results results of the electric maximum and magnetic fields appear when the phases are untransposed. In the maximumvalues valuesforforelectric electric and magnetic fields appear when the phases are untransposed. untransposed case the case maximum electric field is 7.5 field timesislower, and in the transposed it is 21.2 In the untransposed the maximum electric 7.5 times lower, and in thecase transposed times than the reference levels hg = 15 m. In the the maximum case magnetic case lower it is 21.2 times lower than the for reference levels foruntransposed hg = 15 m. In case the untransposed the field is 40 times lower,field and in transposed is 72.9 times lower case than it theis reference levels for maximum magnetic is the 40 times lower,case andit in the transposed 72.9 times lower hthan m. For h = 30 m, more than three times lower values are observed. g = 15the g reference levels for hg = 15 m. For hg = 30 m, more than three times lower values are observed. Figure 7: a) RMS electric field and b) RMS magnetic field for single-circuit OTL Figure 8: a) RMS electric field and b) RMS magnetic field for double-circuit towers 48 JET ---------- 5 CONCLUSION Assessment of human exposure to electric and magnetic fields near transmission lines using FEMM In this paper, we have numerically computed the RMS values of ELF electric and magnetic fields near 110 kV and 400 kV overhead transmission lines. Simulations were performed using the open-source 5 CONCLUSION software FEMM 4.2, using an automated procedure that has been briefly described. The electric and magnetic fieldwe levels fornumerically different OTL configurations were compared theand reference levels for In this paper, have computed the RMS values of ELF with electric magnetic fields human exposure to electromagnetic fields established by the ICNIRP. Additional computation and near 110 kV and 400 kV overhead transmission lines. Simulations were performed using the validation were done for different configurations. It was observed that an error of less open-source software FEMM 4.2, OTL usingand anUTL automated procedure that has been briefly described. than 5% occurred between the computed and the reference values for validation. A comparison with The electric and magnetic field levels for different OTL configurations were compared with measured values near an OTL was also provided, where good agreement with the computed values the reference levels for human exposure to electromagnetic fields established by the ICNIRP. was observed. Therefore, in safety-related studies, the presented approach can be considered a Additional computation and validation were done for different OTL and UTL configurations. It decent substitute and an efficient method for assessing human exposure to ELF electric and was observed that an error of less than 5% occurred between the computed and the reference magnetic fields. values for validation. A comparison with measured values near an OTL was also provided, where good agreement with the computed values was observed. Therefore, in safety-related studies, the presented approach can be considered a decent substitute and an efficient method for assessing human exposure to ELF electric and magnetic fields. Acknowledgments Acknowledgments This work was supported by the Ss. Cyril and Methodius University in Skopje, Project NIP.UKIM.20- This work was supported by the Ss. Cyril and Methodius University in Skopje, Project NIP. 21.10. UKIM.20-21.10. References [1] A. W. Wood, K. Karipidis (Eds.): Non-Ionizing Radiation Protection - Summary of Research and Policy Options. Part V: Extremely Low-Frequency (ELF) Electric and Magnetic Fields, John Wiley & Sons, Hoboken, p.p. 257-338, 2017 [2] IEC TR 61000-5-1, Electromagnetic compatibility (EMC) - Part 5-1: Installation and mitigation guidelines - General considerations, 1996 [3] IEC 62110, Electric and magnetic field levels generated by AC power systems - Measurement procedures with regard to public exposure, 2009 [4] EN 50443, Effects of electromagnetic interference on pipelines caused by high voltage a.c. electric traction systems and/or high voltage a.c. power supply systems, 2011 [5] Directives concerning the protection of telecommunication lines against harmful effects from electric power and electrified railway systems. CCITT Directives, Vol. II, Geneva, 1989 [6] M. V. K. Chari, S. J. Salon: Numerical Methods in Electromagnetism, Academic Press, p.p. 283-357, 2000 [7] M. N. O. Sadiku: Numerical Techniques in Electromagnetics, CRC Press, Second Edition, ch. 6, 2000 [8] M. Shabbir, M. Malik, M. Ahmad, A. Pervaiz, R. Siddique: Finite Element Solution for Two Dimensional Laplace Equation with Dirichlet Boundary Conditions, Pakistan Journal of Engineering and Applied Sciences, Vol. 10, p.p. 97-102, 2012 JET 49 10 Bojan Glushica, Blagoja Markovski, Andrijana Kuhar, Vesna Arnautovski Toseva Bojan Glushica, Blagoja Markovski, Andrijana Kuhar, Vesna Arnautovski Toseva ---------- JET Vol. 16 (2023) Issue 1 JET Volume 16 (2023) Issue 1, 2023 [9] International Commission on Non Ionizing Radiation Protection (ICNIRP): Guidelines for Limiting Exposure to Time-Varying Electric and Magnetic Fields (1 Hz - 100 kHz), Health Physics, Vol. 99, Iss. 6, p.p. 818-836, 2010 [10] B. Markovski, L. Grcev, V. Arnautovski-Toseva: Fast and Accurate Transient Analysis of Large Grounding Systems in Multilayer Soil, IEEE Transactions on Power Delivery, Vol. 36, Iss. 2, p.p. 598-606, 2021 [11] E. Lunca, S. Vornicu, A. Salceanu, O. Bejenaru: 2D Finite Element Model for computing the electric field strength-rms generated by overhead power lines, Journal of Physics: Conference Series, Vol. 1065, Iss. 5, p.p. 1-4, 2018 50 JET JET Volume 16 (2023), p.p. 1 - 10 Issue 1, 2023 JET Volume 14 (2021)Issue 1, 2023 p.p. 51-66 Type of article: Issue 1,1.01 2023 Type of article: 1.01 http://www.fe.um.si/si/jet.htm http://www.fe.um.si/si/jet.html ANALYSIS OF REVITALISATION MODEL BEHAVIOUR FOR THERMAL POWER PLANTS IN DIFFERENT GEOGRAPHICAL AREAS ANALIZA ODZIVANJA REVITALIZACIJSKEGA MODELA TERMOENERGETSKA POSTROJENJA NA RAZLIČNIH GEOGRAFSKIH LOKACIJAH Martin Bricl , Jurij Avsec1 Keywords: revitalisation model, solar tower, heliostat field, solar irradiance, geographical location Abstract The implementation of renewable sources for electricity production into the energy portfolio of European countries has been a priority in recent years, especially taking into account the current geo-political changes. Even though coal is the fuel of the past, its use cannot be put aside that easily; firstly, because of the high fluctuation of electricity production from renewable sources, and secondly because of the possible negative economic impact on the economy resulting from a change in electricity prices when exiting coal. Based on the Rankine process, the authors of this paper designed a solar tower installation with a heliostat field, which enables electricity production based on solar irradiation. This combination also foresees an additional installation for flue gas desulphurisation. This combination of three processes is named the ‘revitalisation model’ for thermal power plants (TPPs). Based on the computer model and energy market parameters, the authors tested the ‘revitalisation model’ for pessimistic and optimistic scenarios. In the scope of the paper, the authors analyse the performance of the proposed ‘revitalisation model’ for three different  Corresponding author: Martin Bricl, Rudis d.o.o. Trbovlje, Trg revolucije 25b 1420 Trbovlje, Tel: +386 3 56 12 409, E-mail address: martin.bricl@rudis.si 1 University of Maribor, Faculty of Energy Technology, Hočevarjev trg 1, SI-8270 Krško, Slovenia JET 51 Martin Bricl, Jurij Avsec JET Volume 16 (2023) Issue 1, 2023 geographical locations – Berlin in Germany, Wuwei in China, and Hyderabad in India. The results of the analysis are described and shown graphically. Povzetek Uvajanje obnovljivih virov za proizvodnjo električne energije v energetski portfelj evropskih držav je v zadnjih letih postala prednostna naloga, še posebej zaradi spreminjajočih se geopolitičnih razmer. Premog je gorivo preteklosti, vendar ga ne moremo tako zlahka opustiti. Vodila razloga za to sta veliko nihanje proizvodnje električne energije iz obnovljivih virov in negativni ekonomski vpliv na gospodarstvo, ki bi ga lahko povzročila sprememba cen električne energije s prenehanjem uporabe premoga. Zraven obstoječega procesa Rankine smo zasnovali instalacijo solarnega stolpa s heliostatskim poljem, ki omogoča proizvodnjo električne energije na osnovi sončnega obsevanja. V tej kombinaciji smo tudi predvideli dodatno napravo za razžveplanje dimnih plinov. Ta tri-fazni proces smo poimenovali revitalizacijski model termoenergetskih postrojenj. Na podlagi računalniškega modela in parametrov energetskega trga smo preizkusili model revitalizacije za pesimistični in optimistični scenarij. V članku bomo analizirali uspešnost predlaganega modela revitalizacije za tri različne geografske lokacije – Berlin v Nemčiji, Wuwei na Kitajskem in Hyderabad v Indiji – ter prikazali rezultate analize v pisni in grafični obliki. 1 INTRODUCTION The proposed ‘revitalisation model’ comprises three main elements that make up the entire proposed plant. The first component is the Rankine process [1], which represents an existing thermal power plant and has a certain operational energy and exergy efficiency in the process [2]. Coal is the primary fuel of the Rankine process (or steam process). The combustion of coal in a steam boiler releases heat, which generates steam, which is fed into a steam turbine where a shaft drives a generator for electricity production. The second component is the solar power plant, which consists of a solar tower on which the concentrated sunbeam receiver is located, and a field in which heliostatic mirrors are arranged to direct the sun’s rays to a common point on the concentrated sunbeam receiver [3-5]. All the absorbed solar energy is concentrated at a certain point, thus obtaining a high temperature and consequently a high concentration of energy at a point on the solar radiation receiver. The working medium in a solar tower plant is a salt solution, which can be heated to a higher temperature than the evaporation temperature of the water. This energy (heat) is used in the evaporator to produce steam, which is conducted from the solar process back to the steam process [6]. This reduces the amount of steam that the steam boiler needs to produce to be able to run the high-pressure and low-pressure steam turbines, which rotate the generator shaft to produce electricity. This enables the energy of solar radiation [7-8] to be used to produce steam, and the load of the steam boiler in the production of steam during solar radiation can be reduced proportionally [9-13] by the amount of steam that can be produced from the solar process. Due to the lower load and production of steam from the steam boiler, the consumption of coal – a fossil fuel – is also reduced, which also reduces the required amount of carbon emission coupons, as the amount of flue gases and greenhouse gas emissions is lower at the lower load of the steam boiler in the steam process. 52 JET Analysis of revitalisation model behaviour for thermal power plants in different geographical areas 3 Analysis of revitalisation model behaviour for thermal power plants in different geographical areas ---------- Figure 1: The proposed ‘revitalisation model’ combines the traditional Rankine cyclecycle withwith a solar Figure 1: The proposed ‘revitalisation model’ combines the traditional Rankine central receiver system a solar central receiver system third component proposed model revitalisation TPPsis isa aplant plantforforflue fluegas TheThe third component of of thethe proposed model of of thethe revitalisation of of TPPs gas cleaning using the wet calcite process, which is most often identified as the best solution cleaning using the wet calcite process, which is most often identified as the best solution based on on the the best possible technology. The of isthe plant is to thebased guidelines forguidelines selecting for theselecting best possible technology. The purpose ofpurpose the plant primarily primarily reduce the acidic components the flue and consequently the impact reduce the to acidic components in the flue ingases andgases consequently reduce reduce the impact on the on the environment living beings. The advantage ofprocess the wetisprocess is theand cheap and easily environment and living and beings. The advantage of the wet the cheap easily accessible accessible reagent as integrity well as the for the environment of the gas cleaning by-product reagent as well as the forintegrity the environment of the flue gasflue cleaning by-product and the and the specimen in it. Properly designed desulphurisation technology can achieve bothlevels high of specimen in it. Properly designed desulphurisation technology can achieve both high levels of purification of acidic components – sulphur dioxide as well as other air pollutants such purification of acidic components – sulphur dioxide as well as other air pollutants such as dust and as dust and some[14-15]. heavy metals [14-15]. As of a by-product of flue gas cleaning, gypsumwhich is formed, some heavy metals As a by-product flue gas cleaning, gypsum is formed, can be which can be used for commercial purposes (possible purchase from cement plants and gypsum used for commercial purposes (possible purchase from cement plants and gypsum board board manufacturers), orused it cantobestabilise used tofly stabilise fly the ash bottom from theofbottom of the steam boiler. manufacturers), or it can be ash from the steam boiler. 2 2 2.1 OPTIMISTIC AND PESSIMISTIC OPERATION SCENARIOS FOR THE CHOSEN GEOGRAPHICAL LOCATIONS OPTIMISTIC AND PESSIMISTIC OPERATION SCENARIOS FOR THE CHOSEN GEOGRAPHICAL LOCATIONS Geographical location Velenje, Slovenia Figure 2, shown below, illustrates the economic performance of the proposed model. As can be seen, with the help of solar energy [16-18], the proposed model is profitable when taking 2.1into Geographical locationscenario, Velenje, Slovenia consideration the optimistic which covers all the costs of fossil fuels, the flue gas cleaning process, infrastructure maintenance and other regular maintenance costs. In this case, Figure shown below, economic proposed As canbelow, be seen, the 2, proposed modelillustrates would stillthe generate EURperformance 1,075,400.00ofinthe annual profit.model. In the figure withthethe help of solar energy [16-18], the proposed model is profitable when taking into optimistic scenario is represented by the deletion-related dots and the corresponding right consideration the optimistic scenario, which covers all the costs of fossil fuels, the flue gas cleaning y-axis. The sum of monthly net profits from electricity sales is the annual economic result of the process, infrastructure considered scenario.maintenance and other regular maintenance costs. In this case, the proposed model would still generate EUR 1,075,400.00 in annual profit. In the figure below, the optimistic scenario is represented by the deletion-related dots and the corresponding right y-axis. TheJET sum 53 of monthly net profits from electricity sales is the annual economic result of the considered scenario. 4 Martin Bricl, Jurij Avsec Martin Bricl, Jurij Avsec ---------- JET Vol. 16 (2023) Issue 1 JET Volume 16 (2023) Issue 1, 2023 Figure 2: Economic behaviour of the ‘revitalisation model’model’ for thefor geographical location Figure 2: Economic behaviour of proposed the proposed ‘revitalisation the geographical of Velenje, Slovenia location of Velenje, Slovenia Takinginto into account accountthe the pessimistic pessimisticscenario, scenario,the thecosts costsof of allowances allowancesfor forCO2 CO2 emissions emissions must must be Taking addedtotoallallthe theaforementioned aforementionedcosts, costs,asasthey theyare are a form taxation operation TPPs. added a form ofof taxation forfor thethe operation of of TPPs. In In the ofpessimistic the pessimistic scenario, assuming the of CO2 emission allowances is the casecase of the scenario, assuming that thethat price of price CO2 emission allowances is expected to be higher with eachwith additional year thatyear a that TPP aoperates, the model wouldwould generate EUR expected to be higher each additional TPP operates, the model generate 353,050.00 in losses per year. not isa not bad aachievement, as, without a central solar tower EUR 353,050.00 in losses per This year.isThis bad achievement, as, without a central solar system, the annual loss of aloss TPPofwould evenbegreater. As illustrated in Figure 2, the pessimistic tower system, the annual a TPP be would even greater. scenario is shown with columns and the corresponding left y-axis. The sum of monthly net profits As illustrated Figure 2, the pessimistic scenario is shown with columns and the corresponding from electricityinsales is the annual economic result of the pessimistic scenario under consideration. left y-axis. The sum of monthly net profits from electricity sales is the annual The proposed model and its economic benefits will play an important role in theeconomic transitionresult from of the pessimistic under consideration. The proposed andallow its economic benefits conventional fossil scenario fuels to renewable energy sources (RES), as model it would the simultaneous will play anofimportant the transition from conventional fossil to renewable production electricity role frominthermal power and renewable sources – afuels central solar powerenergy plant, sources (RES), asaitstable wouldelectricity allow the distribution simultaneous production of electricity from thermalof, power thus maintaining network and reducing the consumption and and renewable sources dependence on, fossil fuels.– a central solar power plant, thus maintaining a stable electricity distribution network and reducing the consumption of, and dependence on, fossil fuels. 2.2 Wuwei, China 2.2 Geographical Geographicallocation location Wuwei, China For 3.3. Figure 4 Forthe thelocation locationofofthe thecity cityofofWuwei, Wuwei,China, China,effective effectivesolar solarirradiance irradianceis isshown shownininFigure Figure Figure illustrates the pessimistic and optimistic scenarios for the chosen location. Table 1 represents the 4 illustrates the pessimistic and optimistic scenarios for the chosen location. Table 1 represents income per corresponding month for the optimistic and pessimistic scenarios. the income per corresponding month for the optimistic and pessimistic scenarios. 54 JET Analysis of revitalisation model behaviour for thermal power plants in different geographical areas Analysis of revitalisation model behaviour for thermal power plants in different 5 5 geographical areas Analysis of revitalisation model behaviour for thermal power plants in different geographical areas ------------------- Figure 3: Effective solar irradiance geographicallocation locationofof Wuwei, China Figure 3: Effective solar irradianceby bymonth month for for the the geographical Wuwei, China [19][19] Figure 3: Effective solar irradiance by month for the geographical location of Wuwei, China [19] In Figure 3, it can be seen that the effective sun irradiance expressed in hours per month is equally In Figure 3, it can seen that irradiance expressed inofhours month is equally spread across the be whole year.the In effective Figure 4,sunwhere the realisation the per model is presented In Figure 3,the it can be seen that the effective sun irradiance expressedofinthe hours per month is spread across whole year. In Figure 4, where the realisation model is presented (pessimistic and optimistic scenarios) the operation of the model in the summer months is not that equally spread across the whole year. In Figure 4, where the realisation of the model is presented (pessimistic and the operation thesummer model in the summer months is not that promising, due to optimistic the optimistic regularscenarios) monsoon periods duringofthe (pessimistic scenarios) the operation of the model months. in the summer months is not promising, due toand the regular monsoon periods during the summer months. that promising, due to the regular monsoon periods during the summer months. Figure 4:4:Economic behaviour of proposed the geographicallocation locationof of Figure 4: Economic behaviour of the proposed‘revitalisation ‘revitalisationmodel’ model’ for Figure Economic behaviour ofthe the proposed ‘revitalisation model’ for the the geographical geographical location Wuwei, China ofWuwei, Wuwei,China China JET 55 January 171,020.00 54,138.00 February 78,180.00 -31,591.00 March Martin Bricl, Jurij Avsec 80,020.00 JET Volume 16 (2023) Issue 1, 2023 -37,073.00 77,160.00 -37,709.00 Table 1:April Economic values of model operation for an individual month in the case of optimistic or pessimistic scenarios May Month June January FebruaryJuly March April August May September June JulyOctober August November September October December November December TOTAL: TOTAL: 2.3 70,310.00 Optimistic scenario [€] 84,280.00 171,020.00 78,180.00 108,230.00 80,020.00 92,710.00 77,160.00 70,310.00 98,430.00 84,280.00 108,230.00 151,820.00 92,710.00 140,403.00 98,430.00 151,820.00 141,340.00 140,403.00 141,340.00 1,293,903.00 1,293,903.00 -48,579.00 Pessimistic scenario [€] -31,960.00 54,138.00 -31,591.00 -11,227.00 -37,073.00 -26,416.00 -37,709.00 -48,579.00 -18,101.00 -31,960.00 -11,227.00 33,619.00 -26,416.00 30,524.00 -18,101.00 33,619.00 24,256.00 30,524.00 24,256.00 -100,119.00 -100,119.00 Geographical location Berlin, Germany 2.3 Geographical location Berlin, Germany For the location of the city of Berlin, Germany, effective solar irradiance is shown in Figure 5. Figure 6 For the the pessimistic location of the of Berlin, scenarios Germany, effective solar irradiance shown2inshows Figurethe 5. income illustrates andcity optimistic for the chosen location.is Table Figure 6 illustrates the pessimistic and optimistic scenarios for the chosen location. Table 2 shows per corresponding month for the optimistic and pessimistic scenarios. the income per corresponding month for the optimistic and pessimistic scenarios. Figure 5: Display thetime timeof ofeffective effective solar forfor thethe citycity of Berlin, Germany [20] [20] Figure 5: Display ofof the solarradiation radiation of Berlin, Germany 56 JET Analysis of revitalisation model behaviour for thermal power plants in different geographical areas 7 Analysis of revitalisation model behaviour for thermal power plants in different geographical areas ---------- Figure 6: Optimistic and pessimistic operating scenarios for the of Berlin Figure 6: Optimistic and pessimistic operating scenarios for the citycity of Berlin Table 2: Economic values of model operation for an individual month in the case of optimistic scenarios Table 2: Economic values of model operation fororanpessimistic individual month in the case of optimistic or pessimistic scenarios Month January Month February January March April February May March June July April August May September October June November December July TOTAL: August Optimistic scenario [€] Pessimistic scenario [€] -120,500.00 Optimistic12,650.00 scenario [€] Pessimistic scenario [€] 6,100.00 -115,350.00 12,650.00 -120,500.00-87,510.00 36,780.00 81,600.00 6,100.00 -115,350.00-32,580.00 79,940.00 -37,360.00 36,780.00 -87,510.00 110,730.00 -1,840.00 125,020.00 81,600.00 -32,580.00 7,630.00 96,470.00 -20,220.00 79,940.00 -37,360.00-24,610.00 92,610.00 63,230.00 -63,650.00 110,730.00 -1,840.00 8,570.00 -119,490.00 -5,490.00 125,020.00 7,630.00 -139,640.00 708,210.00 -755,120.00 96,470.00 -20,220.00 92,610.00 2.4 September Geographical location Hyderabad, India-24,610.00 October 63,230.00 -63,650.00 For the location of the city of Hyderabad, India, effective solar irradiance is shown in Figure 7. Figure 8 illustrates the pessimistic and optimistic scenarios for the chosen location. Table 3 November 8,570.00 -119,490.00 represents the income per corresponding month for the optimistic and pessimistic scenarios. December -5,490.00 -139,640.00 TOTAL: 708,210.00 -755,120.00 JET 57 For the location of the city of Hyderabad, India, effective solar irradiance is shown in Figure 7. Figure 8 illustrates the pessimistic and optimistic scenarios for the chosen location. Table 3 JET Volume 16 (2023) Martin Bricl, Jurij Avsec month for the optimistic and pessimistic represents the income per corresponding scenarios. Issue 1, 2023 Figure 7: Display of the time of effective solar radiation for the city of Hyderabad, India [21] Figure 8: Optimistic and pessimistic operating scenario of the model for the Hyderabad site Table 3: Economic values of model operation for an individual month in the case of optimistic or pessimistic scenarios Month January February March April May June July 58 JET Optimistic scenario [€] 230,010.00 114,300.00 107,820.00 95,180.00 74,370.00 76,250.00 85,690.00 Pessimistic scenario [€] 119,330.00 10,380.00 -5,170.00 -16,890.00 -43,860.00 -41,120.00 -36,570.00 Analysis of revitalisation model behaviour for thermal power plants in different geographical areas August September October November December TOTAL: 3 79,260.00 108,340.00 181,880.00 181,270.00 192,150.00 1,526,520.00 -41,720.00 -6,990.00 66,610.00 71,178.00 80,940.00 156,118.00 REVITALISATION MODEL RESPONSE FOR CHANGED MARKET PARAMETERS The designed model was further analysed by considering the following parameters for the geographical location of the cities of Berlin, Hyderabad and Wuwei: 3.1 • number of hours of effective solar radiation • local coal price • the price of electricity for the country in which the selected geographical location is located • the price of carbon dioxide emissions if such a taxation scheme is located in the country of the selected geographical location Geographical location Wuwei, China For the geographical location of Wuwei, China, when analysing the behaviour of the model, the authors considered the change in parameters that depend on local regulations and limits, as shown in Table 4. Table 4: Display of considered changed parameters for the location of Wuwei, China Parameter Coal price CO2 emission coupon price Salaries Electricity price Quantity 60.00 / 9.50 82.00 Unit [€ / t] [€ / t] [€ / h] [€ / MWh] Figure 9 and Table 5 show the graphically and numerically expected realisation of the considered model for the selected location of Wuwei. JET 59 Figure 9 and Table 5 show the Jurij graphically and numerically expectedJET realisation Volume 16 (2023)of the Martin Bricl, Avsec Issue 1, 2023 considered model for the selected location of Wuwei. Figure 9: Display of of thethe expected of the themodel modelbased based changed entry Figure 9: Display expectedrealisation realisation of onon thethe changed entry parameters for the location of Wuwei parameters for the location of Wuwei Table 5: Numerical representation the expected realisation of the realistic scenarioaccording Table 5: Numerical representation of the of expected realisation of the realistic scenario according to the changed entry parameters for the location of Wuwei to the changed entry parameters for the location of Wuwei Month Month January January February March February April MarchMay June April July May August September JuneOctober November JulyDecember TOTAL August September 3.2 Realistic scenario Realistic scenario[€][€] 375,650.00 375,650.00 343,480.00 370,990.00 343,480.00 332,130.00 339,600.00 370,990.00 307,160.00 332,130.00 325,540.00 329,490.00 339,600.00 294,720.00 307,160.00 332,680.00 346,000.00 325,540.00 360,770.00 4,058,210.00 329,490.00 294,720.00 Geographical location Berlin, Germany For the geographical location of Berlin, the analysis of the model behaviour took into account the change in parameters that depend on local regulations and limits, as shown in Table 6. 60 JET For the geographical location of Berlin, the analysis of the model behaviour took into account the change in parameters that depend on local regulations and limits, as shown in Table 6. Analysis of revitalisation model behaviour for thermal power plants in different geographical areas Table 6: Display of considered changed parameters for Berlin, Germany Parameter Quantity Unit Table 6: Display of considered changed parameters for Berlin, Germany Coal price 51.00 – 85.00 [€ / t] Parameter Quantity Unit CO2 emission coupon price 25.00 [€ Coal price 51.00 – 85.00 [€/ t] / t] CO2 emission coupon price 25.00 [€ / t] Salaries 30.00 [€ / h] Salaries 30.00 [€ / h] Electricity price 120.00 [€ / MWh] Electricity price 120.00 [€ / MWh] FigureFigure 10: Illustration of the of expected realisation of the of model with changed input parameters 10: Illustration the expected realisation the model with changed input for the location of Berlin parameters for the location of Berlin Table 7: Numerical representation of the expected realisation of the realistic scenario according to the changed entry parameters for the location of Berlin Month January February March April May June July August September October November December Realistic scenario [€] -507,000.00 -362,090.00 -217,830.00 -19,180.00 320.00 31,700.00 530.00 -39,210.00 -110,040.00 -289,830.00 -441,730.00 -510,920.00 TOTAL -2.465,280.00 JET 61 JET Volume 16 (2023) Issue 1, 2023 Martin Bricl, Jurij Avsec 3.3 Geographical location Hyderabad, India For the geographical location of Hyderabad, the analysis of model behaviour took into account the change in parameters that depend on local regulations and constraints, as shown in Table 8. Table 8: Display of considered changed parameters for Hyderabad, India Parameter Quantity Unit Coal price 70.00 [€ / t] CO2 emission coupon price / [€ / t] Salaries 8,35 [€ / h] Analysis of revitalisation model behaviour for thermal power plants in different Electricity price 95.00 [€ / MWh] geographical areas 13 ---------- Figure 11: Illustration of the expected realisation of theofmodel with changed inputinput parameters Figure 11: Illustration of the expected realisation the model with changed for thefor location of Hyderabad parameters the location of Hyderabad Table 9: Numerical representation of the expected realisation of the realistic scenario according to the changed entry parameters for the location of Hyderabad 62 JET Month Realistic scenario [€] January 252,980.00 February 145,090.00 March 139,520.00 April 128,810.00 Analysis of revitalisation model behaviour for thermal power plants in different geographical areas Table 9: Numerical representation of the expected realisation of the realistic scenario according to the changed entry parameters for the location of Hyderabad 3 Month January February March April May June July August September October November December Realistic scenario [€] 252,980.00 145,090.00 139,520.00 128,810.00 110,130.00 108,970.00 120,440.00 117,770.00 144,400.00 223,240.00 215,090.00 221,840.00 TOTAL 1,928,280.00 CONCLUSION Table 10 summarises the results of the considered model for different geographical locations and parameters. The results for two different cases are summarised and shown for three additional locations – Wuwei, Berlin and Hyderabad,. The first example takes into account the change of geographical location only and the consequent change of hours of effective solar radiation. The second example involves changing several parameters. In addition to changes in geographical location, local fuel (coal) prices, local electricity prices, and local labour or personnel prices are also taken into account. When analysing the operation of the plant, it was found that due to high fuel costs, the production of electricity exclusively from steam generated by a steam boiler is unprofitable. Thus, the contribution of the central receiver system (CRS) is essential for the cost-effective operation of the assumed model. As demonstrated by the positive operating scenario, the proposed system would achieve positive market results in the current market situation. In the case of the pessimistic scenario, the system would only operate profitably for four months a year, which is a low amount, however, it should be noted that most TPPs operate at a loss and the state provides financial assistance for uninterrupted electricity production. The pessimistic scenario shows a positive impact of upgrading the CRS system, as the loss at the annual level of operations is reduced almost 10-fold. JET 63 positive operating scenario, the proposed system would achieve positive market results in the current market situation. In the case of the pessimistic scenario, the system would only operate profitably for four months a year, which is a low amount, however, it should be noted that most JET Volume 16 (2023) Martin Bricl, Jurij Avsec TPPs operate at a loss and the state provides financial assistance for uninterrupted Issue electricity 1, 2023 production. The pessimistic scenario shows a positive impact of upgrading the CRS system, as the loss at 10: the Results annual level of considered operations ismodel reduced 10-fold. Table of the foralmost different geographical locations and parameters Table 10: Results of the considered model for different geographical locations and parameters Location PARAMETER Velenje Wuwei Berlin Hyderabad ① ② ① ② ① ② Effective sun irradiance [h] 1,112.3 1,267.9 1.267,9 912.7 912.7 1,427.5 1,427.5 Coal savings [t] 25,227 28,984 28.982 20,742 20.701 32,377 32,375 Amount of emitted CO2 [t] 266,508 260,000 260.757 273,300 273.441 255,500 255,538 Amount of cleaned SO2 [t] 111.8 109 109,3 114 114.6 107 107.2 Optimistic scenario [mio €] 1.07 1.29 4,05 0.71 -2.46 1.52 1.92 Pessimistic scenario [mio €] -0.35 -0.10 / -0.75 / 0.15 / *① - Results of the considered model at the changed geographical locations (number of hours of effective solar radiation) *② - The results of the considered model with the following parameters changed: • Number of hours of effective solar radiation • Number of hours of effective solar radiation • Consideration of the local coal price • Observance of the local electricity price • Taking into account the local price of labour or employees The model represents a possible upgrade and modernisation of conventional TPPs to ensure an uninterrupted supply of electricity even in the event of an increased disruption in the thermal power system due to the production of electricity from renewable sources. Rising fossil fuel prices, and limiting them, will increase interest in the implementation of the model described and similar solutions. 64 JET uninterrupted supply of electricity even in the event of an increased disruption in the thermal power system due to the production of electricity from renewable sources. Rising fossil fuel prices, and limiting them, will increase interest in the implementation of the model described Analysis of revitalisation model behaviour for thermal power plants in different geographical areas and similar solutions. References [1] J. Oman: Generatorji toplote, Univerza v Ljubljani, Fakulteta za strojništvo, Ljubljana 2005 [2] M. Tuma: Energetski sistemi: preskrba z električno energijo in toploto, 3. izdaja; Ljubljana, Fakulteta za strojništvo, 2004 [3] C. Baliff, D. Favrat, V. Aga, M. Romero, A. Steinfeld: Germain Augsburger – Thermoeconomic optimisation of large solar tower power plants, Ecole Politehique Federale De Lausanne, Suisse 2013 [4] S. Doruk, T. Murat, O. Taylan: Investment Analysis of a New Solar Power Plant, International Journal of Renewable and Sustainable Energy, Vol.2, No.6, 2013, Pages 229– 241 [5] B. Burger: Fraunhofer institute for solar energy systems - Electricity production from solar and wind in Germany in 2014, Freiburg, 29 December 2014 [6] P.S. Nolan: Babcock & Wilcox Company - Emission Control Technologies for Coal-Fired Power Plants, Ministry of Electric Power Seminar; Beijing China, 1996 [7] R. Soltani, P. Mohammadzadeh Keleshtery, M. Vahdaty, M. Rahbar, M. Amidpour: Theoretical utilization of high temperature solar power tower technology in a 30 MW cogeneration cycle, Journal of Clean Energy Technologies, Vol.1, 2013 [8] D. E. Chelghoum, A. Bejan: Second-law analysis of solar collectors with energy storage capability, Transactions of ASME, Vol.107, August 1985, Pages 244–251 [9] O. Bahar, A. Khellaf, K. Mohammedi: A review of studies on central receiver solar thermal power plants. Renewable and Sustainable Energy Reviews, Vol.23, 2013, Pages 12–39 [10] H. L. Zhang, J. Baeyens, J. Degreve, G. Caceres: Concentrated solar power plants: Review and design methodology, Renewable and Sustainable Energy Reviews, Vol.22, 2013, Pages 466–481 [11] P. A. Curto, G. Stern: Central solar receivers – applications for utilities and industry, Mechanical Engineering, Vol.104, No.7, 1982 [12] J. Sanz-Bermejo, V. Gallarado-Natividad, J. Gonzales-Aguilar, M. Romero: Comparative Martin Bricl, Jurij Avsec JET Vol. 16 (2023) 16 system performance analysis of direct steam generation central receiver solar thermal Issue 1 power plants in megawatt range, Journal of Solar Energy Engineering, Vol.136, 2014, (9 ---------pages) [13] S. C. Ksushik, V. Reddy Siva, S.K. Tyagi: Energy and exergy analyses of thermal power plants – a review, Renewable and sustainable energy reviews, December 2010 [14] H.R. Kulkarni, P.P. Revankar, S.G. Hadagal: Energy and exergy analysis of coal-fired power plant, International Journal of Innovative Science and Research Technology, Vol.1, No.3 [15] Babcock & Wilcox Company: Steam its generation and use, Edition 41; Ohio, U.S.A., 1992 [16] L. Chao, Z. Rongrong: Thermal performance of different integration schemes for a solar tower aided coal-fired power system, Energy Conversion and Management, Vol.171, 2018, Pages 1237–1245 [17] E. Spayde, P. Mango: Evaluation of a solar-powered organic Rankine cycle using dry organic working fluids, Cogent Engineering, Vol.2, 2015 – Issue 1 JET 65 [18] Povprečno trajanje sončnega obsevanja. (n.d.). V Meteo. Pridobljeno s www.meteo.si [15] Babcock & Wilcox Company: Steam its generation and use, Edition 41; Ohio, U.S.A., 1992 [16] L. Chao, Z. Rongrong: Thermal performance of different integration schemes for a solar JET Volume 16 (2023) Martin Bricl, Jurijsystem, Avsec tower aided coal-fired power Energy Conversion and Management, Vol.171, 2018, Issue 1, 2023 Pages 1237–1245 [17] E. Spayde, P. Mango: Evaluation of a solar-powered organic Rankine cycle using dry organic working fluids, Cogent Engineering, Vol.2, 2015 – Issue 1 [18] Povprečno trajanje sončnega obsevanja. (n.d.). V Meteo. Pridobljeno s www.meteo.si [19] Efektivno sončno obsevanje za mesto Wuwei. (n.d.). V Photovoltaic geographical information system. Pridobljeno s https://re.jrc.ec.europa.eu/pvg_tools/en/#MR [20] Efektivno sončno obsevanje za mesto Berlin. (n.d.). V Photovoltaic geographical information system. Pridobljeno s https://re.jrc.ec.europa.eu/pvg_tools/en/#MR [21] Efektivno sončno obsevanje za mesto Hyderabad. (n.d.). V Photovoltaic geographical information system. Pridobljeno s https://re.jrc.ec.europa.eu/pvg_tools/en/#MR Nomenclature (Symbols) 66 JET (Symbol meaning) t time h hour CO2 carbon dioxide SO2 sulphur dioxide € euros mio million GEN generator MWh megawatt hour JET Volume 16 (2023), p.p. 1 - 10 Issue 1, 2023 JET Volume 16 (2023) p.p. 67-77 Issue 1, 1.02 2023 Type Typeofofarticle: article: 1.04 http://www.fe.um.si/si/jet.htm http://www.fe.um.si/si/jet.html DESIGN OF WFOIL 18 ALBATROSS WITH HYDROGEN TECHNOLOGIES ZASNOVA PLOVILA WFOIL 18 ALBATROSS Z VODIKOVIMI TEHNOLOGIJAMI Nejc Zore1, Jurij Avsec 1, Urška Novosel 1 Keywords: wFoil 18 Albatross, hydrofoil, fuel cell drive, hydrogen technology Abstract This article discusses the design of fuel cell propulsion for 18 albatross foil vessels. The purpose of this article determined the economic viability of such propulsion. WFoil 18 Albatross was chosen for a high-speed, low-power propulsion system. The hydrogen propulsion system for the Albatross vessel consists of the following parts: Electric motor (Emrax 188) to convert electricity into mechanical energy; Battery (LG RESU 3.2EX | LG Battery System), which provides electricity in case of emergency or adds the necessary energy to run the engine at maximum power; Controller (EmDrive 500), which provides enough energy to pass between the elements of the propulsion system; Fuel cell (Hydrogenics HYPM-HD 30 POWER MODULE), which is the primary source of energy; The tank (tank for hydrogen gas type 3) stores fuel, which in our case is hydrogen.  Corresponding author: Nejc Zore, University of Maribor, Faculty of Energy Tehnology, Hočevarjev trg 1 SI-8270, Krško, E-mail address: nejczore20@gmail.com 1 University of Maribor, Faculty of Energy Tehnology, Hočevarjev trg 1 SI-8270, Krško, Slovenia JET 67 Nejc Zore, Jurij Avsec, Urška Novosel JET Volume 16 (2023) Issue 1, 2023 The brackets indicate the parts that have been selected for the hydrogen propulsion system. The approximate weight of all these parts is about 249.1 kg and the price of all these parts is about 55254 €. All prices are from 2020 and are subject to change. The main idea in the construction of this charging station is the use of seawater and solar energy or renewable energy sources for hydrogen production. The components of the charging station are Solar cells (LG NeON 2), Desalination (CRYSTAL EX PURE), Electrolysis (Nel C Series C10), and Charging station (Haskel (Version with air compressor)). The brackets indicate the parts that have been selected for the charging station. The approximate weight of all these parts is about 10236 kg and the price of all these parts is about 517664 €. All prices are from 2020 and are subject to change. Povzetek Ta članek obravnava zasnovo pogona na gorivne celice za 18 plovil albatrosa. Namen tega članka je določil ekonomsko upravičenost takšnega pogona. WFoil 18 Albatross je bil izbran za pogonski sistem visoke hitrosti in nizke moči. Pogonski sistem na vodik za plovilo Albatros je sestavljen iz naslednjih delov: - Elektromotor (Emrax 188) za pretvorbo električne energije v mehansko; - Baterija (LG RESU 3.2EX | LG Battery System), ki zagotavlja elektriko v nujnih primerih ali doda potrebno energijo za delovanje motorja z največjo močjo; - Krmilnik (EmDrive 500), ki zagotavlja dovolj energije za prehajanje med elementi pogonskega sistema; - Gorivna celica (Hydrogenics HYPM-HD 30 POWER MODULE), ki je primarni vir energije; - Rezervoar (rezervoar za plin vodik tip 3) hrani gorivo, ki je v našem primeru vodik. Oklepaji označujejo dele, ki so bili izbrani za pogonski sistem na vodik. Približna teža vseh teh delov je približno 249,1 kg, cena vseh teh delov pa je približno 55254 €. Vse cene so od leta 2020 in se lahko spremenijo. Glavna ideja pri izgradnji te polnilnice je uporaba morske vode in sončne energije oziroma obnovljivih virov energije za proizvodnjo vodika. Sestavni deli polnilne postaje so sončne celice (LG NeON 2), razsoljevanje (CRYSTAL EX PURE), elektroliza (Nel C serije C10) in polnilna postaja (Haskel (različica z zračnim kompresorjem)). Oklepaji označujejo dele, ki so bili izbrani za polnilno postajo. Približna teža vseh teh delov je približno 10236 kg, cena vseh teh delov pa je približno 517664 €. Vse cene so od leta 2020 in se lahko spremenijo. 1 INTRODUCTION 1.1 Platform The basis of the platform is a trimaran to which four hydrofoils are attached: the main or rear pair of hydrofoils and the front or stabilizer pair of hydrofoils, as shown in Figure 1. In principle, we can say that all four hydrofoils determine the whole, since they only work stably around the longitudinal and transverse axes of movement. The vessel maintains its position along these two directions and requires only vertical rudder to maintain course. 68 JET Design of wfoil 18 albatross with hydrogen technologies Figure 1: Distribution of hydrogen propulsion elements throughout the vessel In addition to stability, the double “V” arrangement of hydrofoils has an advantage over classic vessels by enabling both calm sailing in rough, wavy seas and (due to the folding system, otherwise relatively long hydrofoils) the possibility of sailing in very shallow seas and even landing on sandy beaches. This makes the vessel an economical, comfortable and very useful platform for various types of vessels. When sailing at high speed, the hulls are quite high above the surface of the water, so that the waves do not affect the sailing itself. The vessel has been tested in extreme conditions and has always offered calm sailing with much less strain on its structure. Figure 2 shows two different graphs of water resistance and speed for two different concepts, namely for the constantly wetted system and for the wFoil system. Figure 2: Graph of water resistance and speed From the above description, we can understand that the wFoil platform offers the following properties, which are far ahead of the properties of classic vessels and also of other hydrofoil vessels: JET 69 Nejc Zore, Jurij Avsec, Urška Novosel JET Volume 16 (2023) Issue 1, 2023 - By increasing the sailing speed, the vessel rises above the water surface, so that the hulls of the vessel do not touch the waves. Hydrofoils are relatively long compared to the size of the vessel, which allows calm, fast, comfortable and safe navigation in rough seas. - At higher speeds, the hydrodynamic resistance of the vessel is lower than that of other vessels - even vessels that use hydrofoils. This feature occurs because the wetted part of hydrofoils decreases with increasing sailing speed. - wFoil vessel is also useful in very shallow waters. We can also land on sandy beaches, which is possible thanks to the unique system of folding the otherwise relatively long hydrofoils under the transverse supports of the platform structure. - The wFoil platform, with its hydrofoil arrangement, only enables stability around the transverse and longitudinal axes of movement. This allows the vessel’s platform to remain in a more or less horizontal position without the use of complicated systems to maintain stability. 1.2 Benefits The main advantages of the wFoil platform are listed below: - Directivity and stability of the vessel Smaller hydrodynamic resistance Greater range of useful vessel speeds Folding hydrofoils Wave compensation - Economical construction and easy maintenance. 2. CONSTRUCTING A HYDROGEN PROPULSION 2.1 Conceptual design of a hydrogen drive The hydrogen propulsion system for the Albatross vessel consists of parts as shown in Figure 3: - Electric motor for converting electrical energy into mechanical energy; A battery that provides electricity in case of emergency or adds the necessary energy for the engine to operate at maximum power; A controller that provides enough energy to pass between the elements of the drive assembly; Fuel cell, which is the primary source of energy; - The tank stores the fuel, which in our case is hydrogen. - Figure 4 shows the distribution of propulsion elements across the vessel. 70 JET ---------- Design of wfoil 18 albatross with hydrogen technologies Figure 3: Scheme of the hydrogen drive. Electric motor Battery Fuel cell H2 tank Controller Figure 4: Distribution of hydrogen propulsion elements throughout the vessel 2.2 Figure 4: Distribution of hydrogen propulsion elements throughout the vessel. Components Electric motor: Emrax 188 2.2 Components Battery: LG RESU 3.2EX | LG Battery System Controller: EmDrive 500 Electric motor: Emrax 188 Fuel cell: Hydrogenics HYPM-HD 30 POWER MODULE Battery: LG RESU 3.2EX | LG Battery System Reservoir H2: Reservoir for hydrogen gas type 3 Controller: EmDrive 500 Fuel cell: Hydrogenics HYPM-HD 30 POWER MODULE Reservoir H2: Reservoir for hydrogen gas type 3 JET 71 Nejc Zore, Jurij Avsec, Urška Novosel 6 JET Vol. 16 (2023) Nejc Zore, Jurij Avsec, Urška Novosel 6 Issue 1 Vol. 16 JETJET Volume 16(2023) (2023) Issue Issue 1, 2023 1 Nejc Zore, Jurij Avsec, Urška Novosel ------------------Table 1: Hydrogen propulsion components Table 1: Hydrogen propulsion components Voltage [V] Electric Electric motor motor 110 Current [A] 0 - 800 Voltage [V] Current [A] Table 1: Hydrogen propulsion components 110 0 - 800 ∅ 188 Dimensions ∅×188 Dimensions 77 [mm] × 77 [mm] Mass [kg] 7,2 Mass [kg] 7,2 Controller Controller 30 - 125 30 - 125 Fuel Cell Fuel Cell 60 - 120 / Battery Battery / Total Total 45,2 – 45,258,1 – / 58,1 0 - 800 0 - 500 / / 0 - 800 0 - 500 / / / 78 × 310 719 × 406 ∅ 460 230 × 664 78××205 310 719 406 ∅ 460 × 664 × ×261 × 991 230 × 165 / × 205 60 - 120 H2 Tank H2 Tank / / 4,9 75 × 261 102 60 × 165 249,1 4,9 75 × 991 / 102 60 249,1 Efficiency Efficiency [%] [%] Price [€] Price [€] 96 96 9696 5353 / / 85 85 / 3.700 3.700 1.900 1.900 39.000 39.000 5.090 5.090 5.564 5.564 55.254 55.254 Model Model Emrax Emrax 188(LV) (LV) 188 EmDrive EmDrive 500 500 HD30 HD30 LG RESU/ SHCSHC 90L90L LG RESU 3.2 EX 700700 bar bar 3.2 EX 2.3 2.3 / / Calculation propulsion system Calculationfor forthe thehydrogen hydrogen propulsion system Calculation of hydrogen propulsion system for the Calculation ofthe thetotal totalweight weightofofthe the hydrogen propulsion system for Albatross the Albatross 7,2 𝑘𝑘𝑘𝑘 + 4,9 𝑘𝑘𝑘𝑘 + 75 𝑘𝑘𝑘𝑘 + 102 𝑘𝑘𝑘𝑘 + 60 𝑘𝑘𝑘𝑘 = 249,1 𝑘𝑘𝑘𝑘 (2.1) 0,96 + 0,96 + 0,53 = 0,488 (2.2) 0,96 + 0,96 + 0,85 = 0,78 (2.3) 3700€ + 1900€ + 39000€ + 5090€ + 5564€ = 55254€ (2.4) 7,2 𝑘𝑘𝑘𝑘 + 4,9 𝑘𝑘𝑘𝑘 + 75 𝑘𝑘𝑘𝑘 + 102 𝑘𝑘𝑘𝑘 + 60 𝑘𝑘𝑘𝑘 = 249,1 𝑘𝑘𝑘𝑘 (2.1) Calculation of total efficiency for operation on fuel cells Calculation of total efficiency for operation on fuel cells 0,96 + 0,96 + 0,53 = 0,488 Calculation of total efficiency for battery operation Calculation of total efficiency for battery operation 0,96 + 0,96 + 0,85 = 0,78 Calculation of the final price of all elements in the drive Calculation of the final price of all elements in the drive 3700€ + 1900€ + 39000€ + 5090€ + 5564€ = 55254€ 2.4 2.4 (2.2) (2.3) (2.4) Comparison between a gasoline engine and a hydrogen engine Comparison between a gasoline engine and a hydrogen engine Figure 5 shows a comparison between gasoline engine and hydrogen drives. The figure includes 2.4 between a gasoline gasoline engine and hydrogen engine the fuel5Comparison for botha drives, the yields and the products produced by theadrives. Figure shows comparison between engine and hydrogen The figure includes the fuel for both drives, the yields and the products produced by the drives. Figure 5 shows a comparison between gasoline engine and hydrogen drives. The figure includes the fuel for both drives, the yields and the products produced by the drives. 72 JET Design of wfoil 18 albatross with hydrogen technologies 7 Design of wfoil 18 albatross with hydrogen technologies ---------- Figure 5: Comparison of energy conversions. Calculation for a gasoline engine: 0,75 12 𝑘𝑘𝑘𝑘 𝑙𝑙 𝑘𝑘𝑘𝑘ℎ 𝑘𝑘𝑘𝑘 × 25 𝑙𝑙 = 18,75 𝑘𝑘𝑘𝑘 × 18,75 𝑘𝑘𝑘𝑘 = 225 𝑘𝑘𝑘𝑘ℎ 225 𝑘𝑘𝑘𝑘ℎ × 0,25 = 56,25 𝑘𝑘𝑘𝑘ℎ (2.5) (2.6) (2.7) Calculation for hydrogen propulsion: 33,33 𝑘𝑘𝑘𝑘ℎ 𝑘𝑘𝑘𝑘 × 3,5 𝑘𝑘𝑘𝑘 = 116,66 𝑘𝑘𝑘𝑘ℎ 116,66 𝑘𝑘𝑘𝑘ℎ × 0,53 = 61,83 𝑘𝑘𝑘𝑘ℎ 61,83 𝑘𝑘𝑘𝑘ℎ × 0,96 = 59,35 𝑘𝑘𝑘𝑘ℎ 59,35 𝑘𝑘𝑘𝑘ℎ × 0,96 = 56,98 𝑘𝑘𝑘𝑘ℎ (2.8) (2.9) (2.10) (2.11) JET 73 8 Nejc Zore, Jurij Avsec, Urška Novosel JET Vol. 16 (2023) JET Volume Issue 1 16 (2023) Issue 1, 2023 Nejc Zore, Jurij Avsec, Urška Novosel ---------- 3. 3 CONSTRUCTINGAAHYDROGEN HYDROGEN CHARGING STATION CONSTRUCTING CHARGING STATION 3.1 Conceptual design of the charging station 3.1 Conceptual design of the charging station The main idea in constructing this charging station is the use of seawater and solar energy or sources for thecharging productionstation of hydrogen. Figures 8 show the process The mainrenewable idea in energy constructing this is the use 7ofand seawater and solarforenergy or obtaining andsources storing hydrogen. 6 showsof thehydrogen. charging station, which7was in the the process renewable energy for the Figure production Figures andmade 8 show computer program Solidworks. for obtaining and storing hydrogen. Figure 6 shows the charging station, which was made in the computer program Solidworks. Figure 6: Charging station Figure 6: Charging station of wfoilmust 18 albatross with hydrogenElectricity technologies is obtained from solar cells, and in case For proper use,Design seawater be desalinated. 9 For proper use,the seawater must begrid. desalinated. obtained fromitsolar cells, and in case of bad weather from electricity When Electricity water is isdesalinated, goes through electrolysis, of bad weather fromserves the electricity When desalinated, it goes through electrolysis, yielding hydrogen, which as ourgrid. fuel. Thewater nextisstep is to increase the pressure to 700 bar yielding hydrogen, which serves as---------our fuel. The next step is to increase the pressure to 700 bar and storeand it in a pressure vessel until the next filling. store it in a pressure vessel until the next filling. Figure 8: Sheme of the desalination proces. Figure 7: Scheme of the charging station. 74 JET Figure 8: Sheme of the desalination proces. Design of wfoil 18 albatross with hydrogen technologies 3.2 10 Components Nejc Zore, Jurij Avsec, Urška Novosel JET Vol. 16 (2023) Solar cells: LG NeON 2 Nejc Zore, Jurij Avsec, Urška Novosel Desalination: 10 CRYSTAL EX PURE ---------Electrolysis: Nel C Series C10 Charging station: Haskel (Implementation with the help of an airstation compressor) Table 2: Components of the charging Solar cells ---------- Electrolysis Charging Table 2: Components station Table 2: Componentsofofthe thecharging charging station Consumption Consumption Dimensions [m] Dimensions [m] Mass [kg] Mass [kg] Product Product Price [€] Price [€] Model Model 3.3 Solar cells 29,26 MWh/year 29,26 MWh/year / / Desalination Desalination 27,5 kWh/𝑚𝑚3 27,5 kWh/𝑚𝑚3 0,4 × 0,35 × 0,55 Electrolysis 68,9 kWh/kg H2 68,9 kWh/kg H2 × 1,16 2,52 × 2,01 station 6000 10.236 6000 10.236 Electricity (AC) Electricity Clean Water (Class Clean2)Water 30.550 3.114 Hydrogen gas Hydrogen atHydrogen 30 bar gas gas at 700 Hydrogen bar at 30 bar gas at 700 240.000 244.000 bar (AC) 30.550 LG and Fronius LG and Fronius (Class 2) 3.114 Crystal Ex Pure Crystal Ex Pure 240.000 Nel C10 Nel C10 Total (max) 3×3×3 1.386 2.734 Issue 1 Total 2,52 × 1,16 × 2,01 2.734 216 JET Vol. 16 (2023) Charging station 1.680 kWh/day 1.680 (max) kWh/day 3×3×3 0,4 × 0,35 216 × 0,55 1.386 Issue 1 244.000 517.664 517.664 Haskel air driven Haskel air driven option option Calculation for the charging station 3.3 Calculation for the charging station Calculation of the mass of the charging station: Calculation of the mass of the charging station: 1386 𝑘𝑘𝑘𝑘 + 216 𝑘𝑘𝑘𝑘 + 2734 𝑘𝑘𝑘𝑘 + 6000 𝑘𝑘𝑘𝑘 = 10336 𝑘𝑘𝑘𝑘 1386 𝑘𝑘𝑘𝑘 + 216 𝑘𝑘𝑘𝑘 + 2734 𝑘𝑘𝑘𝑘 + 6000 𝑘𝑘𝑘𝑘 = 10336 𝑘𝑘𝑘𝑘 (3.1) (3.1) Calculation of the charging station price: Calculation of the charging station price: 30550€ + 3114€ + 240000€ ++ 244000€ 30550€ + 3114€ + 240000€ 244000€==517664€ 517664€ (3.2) (3.2) 355355 𝑊𝑊 ×𝑊𝑊75 𝑘𝑘𝑘𝑘𝑘𝑘𝑘𝑘 ×= 7526625 = 26625 (3.3) (3.3) 26625 × 1100 𝑘𝑘𝑘𝑘ℎ = 29288 𝑀𝑀𝑀𝑀ℎ 26625 𝑘𝑘𝑘𝑘𝑘𝑘𝑘𝑘 × 1100 𝑘𝑘𝑘𝑘ℎ = 29288 𝑀𝑀𝑀𝑀ℎ (3.4) (3.4) 364€ ×= 7527300€ = 27300€ 364€ × 75 (3.5) (3.5) Nominal power of the system: Nominal power of the system: Amount of expected annual production: Amount of expected annual production: of solar panels: PricePrice of solar panels: JET 75 Amount of expected annual production: 26625 𝑘𝑘𝑘𝑘 × 1100 𝑘𝑘𝑘𝑘ℎ = 29288 𝑀𝑀𝑀𝑀ℎ Nejc Zore, Jurij Avsec, Urška Novosel Price of solar panels: Design of wfoil 18 albatross with hydrogen technologies 364€ × 75 = 27300€ Total prices of inverter and solar panels: (3.4) JET Volume 16 (2023) Issue 1, 2023 11 (3.5) ---------- 27300€ + 3234€ = 30534€ (3.6) How much hydrogen is produced per hour? 10 22,4 = 0,45 𝑘𝑘𝑘𝑘𝑘𝑘𝑘𝑘/ℎ 0,45 𝑘𝑘𝑘𝑘𝑘𝑘𝑘𝑘 ℎ × 2 = 0,9 𝑘𝑘𝑘𝑘/ℎ (3.7) (3.8) How much energy do we get from 1 kg of hydrogen? 𝑘𝑘𝑘𝑘ℎ 33,33 𝑘𝑘𝑘𝑘 × 0,488 = 16,27 𝑘𝑘𝑘𝑘ℎ/𝑘𝑘𝑘𝑘 (3.9) How much energy do we get from a full tank of hydrogen? (The amount should be comparable to 25 liters of gasoline, which is enough for about 2 hours of sailing). 16,27 𝑘𝑘𝑘𝑘ℎ 𝑘𝑘𝑘𝑘 × 3,5 𝑘𝑘𝑘𝑘 = 56,59 𝑘𝑘𝑘𝑘ℎ (3.10) How many kilograms do we need to fill the tank four times? 3,5 𝑘𝑘𝑘𝑘 × 4 = 14 𝑘𝑘𝑘𝑘 (3.11) How long does it take to produce the necessary fuel? 14 𝑘𝑘𝑘𝑘 0,9𝑘𝑘𝑘𝑘/ℎ = 16 ℎ (3.12) How many liters of water are needed to produce fuel? 𝑙𝑙 9 × 16ℎ = 144 𝑙𝑙 ℎ (3.13) How much electricity do we need for such production? 68,9 4 𝑘𝑘𝑘𝑘ℎ 𝑘𝑘𝑘𝑘 × 14 𝑘𝑘𝑘𝑘 = 964,6 𝑘𝑘𝑘𝑘ℎ (3.14) CONCLUSION The current fuel cell technology is suitable for propulsion of the wFoil 18 Albatross, but it is not economically comparable to a petrol engine. Another drawback is the heavier weight than the internal combustion drive. Until material and production prices are reduced, hydrogen technologies will remain uncompetitive with internal combustion engines. However, they are environmentally friendly and have higher efficiencies than 76 JETconventional propulsion systems. Design of wfoil 18 albatross with hydrogen technologies 4. CONCLUSION The current fuel cell technology is suitable for propulsion of the wFoil 18 Albatross, but it is not economically comparable to a petrol engine. Nejc Zore, Jurij Avsec, Urška Novosel Vol. 16 (2023) 12 drawback is the heavier weight than the internal combustion drive. UntilJETmaterial Another and production prices are reduced, hydrogen technologies will remain uncompetitive with internal Issue 1 combustion engines. However, they are environmentally friendly and have higher efficiencies ---------than conventional propulsion systems. Additional Additionalproblems problemsarise arisewhen whensetting settingup upthe thesystem system and and obtaining obtaining appropriate appropriate approvals. approvals. To To continue research for an alternative drive for the wFoil Albatross, batteries only are continue research for an alternative drive for the wFoil Albatross, batteries only are recommended, recommended, but this also likely toovessel's heavy for the vessel's current limitations. but this is also likely tooisheavy for the current limitations. References References [1] N. Zore: Zasnova plovila WFoil 18 Albatross z vodikovimi tehnologijami, Diplomska naloga, 2020 [2] T. Zore: Naprava za premikanje po vodi in/ali po zraku in/ali po kopnem, P-200900187, 2012 [3] Gostota bencina. Fizične in kemične lastnosti. Internet archive wayback machine. Dosegljivo: https://web.archive.org/web/20020820074636/http:/www.sefsc.noaa.gov/HTMLdocs/G asoline.htm [datum dostopa: 28.9.2022] [4] Energetske vrednosti bencina in vodika. Idealhy. Dosegljivo: https://www.idealhy.eu/index.php?page=lh2_outline&fbclid=IwAR3sASHkd5P1C8wPvM DKKrU0ZAR-rDnqhn631pPoD7tJHDzdxh18zON895k [datum dostopa: 28.9.2022] Nomenclature (Symbols) % (Symbol meaning) percent NOx Nitric oxide CO2 Carbon dioxide SOx Sulfur oxides CO Carbon monoxide H2O water € euro JET 77 Author instructions Author instructions http://www.fe.um.si/sl/jet.html http://www.fe.um.si/si/jet.htm MAIN TITLE OF THE PAPER SLOVENIAN TITLE Author1, Author 2, Corresponding author  Keywords: (Up to 10 keywords) Abstract Abstract should be up to 500 words long, with no pictures, photos, equations, tables, only text. Povzetek (Abstract in Slovenian language) Submission of Manuscripts: All manuscripts must be submitted in English by e-mail to the editorial office at jet@um.si to ensure fast processing. Instructions for authors are also available online at http://www.fe.um.si/en/jet/author-instructions.html. Preparation of manuscripts: Manuscripts must be typed in English in prescribed journal form (MS Word editor). A MS Word template is available at the Journal Home page. A title page consists of the main title in the English and Slovenian language; the author(s) name(s) as well as the address, affiliation, E-mail address, telephone and fax numbers of author(s). Corresponding author must be indicated. Main title: should be centred and written with capital letters (ARIAL bold 18 pt), in first paragraph in English language, in second paragraph in Slovenian language. Key words: A list of 3 up to 6 key words is essential for indexing purposes. (CALIBRI 10pt) Corresponding author: Title, Name and Surname, Organisation, Department, Address, Tel.: +XXX x xxx xxx, E-mail address: x.x@xxx.xx  1 Organisation, Department, Address 2 Organisation, Department, Address 78 JET 2 Authors names and surnames Paper title JET Vol. 16 (2023) Issue 1 ---------Abstract: Abstract should be up to 500 words long, with no pictures, photos, equations, tables, text only. Povzetek: - Abstract in Slovenian language. Main text should be structured logically in chapters, sections and sub-sections. Type of letters is Calibri, 10pt, full justified. Units and abbreviations: Required are SI units. Abbreviations must be given in text when first mentioned. Proofreading: The proof will be send by e-mail to the corresponding author in MS Word’s Track changes function. Corresponding author is required to make their proof corrections with accepting or rejecting the tracked changes in document and answer all open comments of proof reader. The corresponding author is responsible to introduce corrections of data in the paper. The Editors are not responsible for damage or loss of submitted text. Contributors are advised to keep copies of their texts, illustrations and all other materials. The statements, opinions and data contained in this publication are solely those of the individual authors and not of the publisher and the Editors. Neither the publisher nor the Editors can accept any legal responsibility for errors that could appear during the process. Copyright: Submissions of a publication article implies transfer of the copyright from the author(s) to the publisher upon acceptance of the paper. Accepted papers become the permanent property of “Journal of Energy Technology”. All articles published in this journal are protected by copyright, which covers the exclusive rights to reproduce and distribute the article as well as all translation rights. No material can be published without written permission of the publisher. Chapter examples: 1 MAIN CHAPTER (Arial bold, 12pt, after paragraph 6pt space) 1.1 Section (Arial bold, 11pt, after paragraph 6pt space) 1.1.1 Sub-section (Arial bold, 10pt, after paragraph 6pt space) Example of Equation (lined 2 cm from left margin, equation number in normal brackets (section.equation number), lined right margin, paragraph space 6pt before in after line): Equation (1.1) JET 79 3 Paper title Authors names and surnames ---------- JET Volume 16 (2023) Issue 1, 2023 Tables should have a legend that includes the title of the table at the top of the table. Each table should be cited in the text. Table legend example: Table 1: Name of the table (centred, on top of the table) Figures and images should be labelled sequentially numbered (Arabic numbers) and cited in the text – Fig.1 or Figure 1. The legend should be below the image, picture, photo or drawing. Figure legend example: Figure 1: Name of the figure (centred, on bottom of figure, photo, or drawing) References [1] N. Surname: Title, Journal Title, Vol., Iss., p.p., Year of Publication [2] N. Surname: Title, Publisher, Year of Publication [3] N. Surname: Title [online], Publisher or Journal Title, Vol., Iss., p.p., Year of Publication. Available: website (date accessed) Examples: [1] J. Usenik: Mathematical model of the power supply system control, Journal of Energy Technology, Vol. 2, Iss. 3, p.p. 29 – 46, 2009 [2] J. J. DiStefano, A.R. Stubberud, I. J. Williams: Theory and Problems of Feedback and Control Systems, McGraw-Hill Book Company, 1987 [3] T. Žagar, L. Kegel: Preparation of National programme for SF and RW management taking into account the possible future evolution of ERDO [online], Journal of Energy Technology, Vol. 9, Iss. 1, p.p. 39 – 50, 2016. Available: http://www.fe.um.si/images/jet /Volume 9_Issue1/03-JET_marec_2016-PREPARATION_OF_NATIONAL.pdf (7. 10. 2016) Example of reference-1 citation: In text [1], text continue. Nomenclature (Symbols) t 80 JET (Symbol meaning) time JET 81 82 JET 9 771855 574008 JET I Journal of Energy Technology I Vol. 16, Issue 1, Junij 2023 I University of Maribor, Faculty of Energy Technology ISSN 1855-5748