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Utilisation of renewable electricity to produce synthetic methane
Klemen Rola, Sven Gruber, Danijela Urbancl, Darko Goričanec, 2023, izvirni znanstveni članek

Ključne besede: power-to-methane, P2M, synthetic methane, CO2 methanation, Aspen Plus, Aspen Adsorption
Objavljeno v DKUM: 18.04.2024; Ogledov: 134; Prenosov: 7
.pdf Celotno besedilo (5,00 MB)
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Dimensional deviations in Ti-6Al-4V discs produced with different process parameters during selective laser melting
Snehashis Pal, Marijana Milković, Riad Ramadani, Janez Gotlih, Nenad Gubeljak, Radovan Hudak, Igor Drstvenšek, Matjaž Finšgar, Tomaž Brajlih, 2023, izvirni znanstveni članek

Opis: When manufacturing complicated products where both material and design play a role, especially thin and curved components, it is difcult to maintain accurate dimensions in Selective Laser Melting. Considering these difculties, this article presents the dimensional errors in the fabrication of Ti-6Al-4V discs and their thermomechanics during manufacturing. Various combinations of laser processing parameters were used to fabricate the 2.00 mm thick discs with a diameter of 5.70 mm. It was found that the thickness shortened and the round shape changed to an oval shape for most of the discs. The thickness decreased along the build-up direction from the bottom to the top and formed a taper that increased with increasing energy density (ED). The horizontal diameter of the discs changed slightly, while the vertical diameters changed remarkably with increasing ED. On the other hand, reducing the laser power resulted in a reduction of the roundness error, while it caused a reduction of the thickness. The hatch spacing signifcantly afected the volume of the melt pool and caused a change in the vertical diameter. The central part of the curved surface of the discs became concave and the concavity increased due to the increasing ED.
Ključne besede: dimension, Ti-6Al-4V, lase power, scanning speed, hatch spacing, selective laser melting
Objavljeno v DKUM: 29.03.2024; Ogledov: 127; Prenosov: 8
.pdf Celotno besedilo (4,48 MB)
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Evaluation of system for economically viable thermal power plant operation
Martin Bricl, Jurij Avsec, 2019, izvirni znanstveni članek

Opis: Taking into consideration the impacts of global warming and strict European Union policy 2030 climate & energy framework, it is imminent for conventional thermal power plants to modernize their infrastructure for achieving economically viable operation on demanding electricity market. In the scope of the paper is presented author%s individual research work - economic evaluation of conventional thermal power plant operation with solar central receiver system and flue gas desulphurization installation. The goal of research work is to determine whether the designed model is profitable on current European electricity market or not. Based on analytical calculations and gathered numerical data for the designed model, a program code was generated in mathematical environment Matlab, that enables simulation of operation for the designed model in the annual time period. Positive and pessimistic scenarios were analyzed. Results are presented numerically and also graphically and show a positive contribution to the economically viable operation of conventional thermal power plants.
Ključne besede: thermal power plant, economically viable operation, a solar central receiver system, renewable technologies, flue gas desulphurization
Objavljeno v DKUM: 22.02.2024; Ogledov: 240; Prenosov: 11
.pdf Celotno besedilo (1019,76 KB)
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Food Waste to Energy through Innovative Coupling of CHP and Heat Pump
Jan Drofenik, Danijela Urbancl, Darko Goričanec, Zdravko Kravanja, Zorka Novak-Pintarič, 2023, izvirni znanstveni članek

Opis: This paper presents the conceptual design of a technological solution for the efficient conversion of food waste into heat and power. The distribution and composition of food loss and waste at different stages of the food supply chain in Slovenia and their potential for biogas production were determined. It was found that more than 50% of food waste comes from households. Therefore, a small plant was designed to convert food waste into biogas, which was innovatively coupled with a combined heat and power (CHP) unit and a heat pump. This doubles the amount of heat generated compared to conventional cogeneration. Based on the capacity of a micro commercial CHP unit, 3330 households (about 8000 residents) would supply food waste. The heat generated could replace 5% of the natural gas used for domestic water heating. The payback period would be 7.2 years at a heat price of about 80 EUR/MWh, however, for municipalities with more than 40,000 inhabitants the payback period would be reduced to less than 3 years. The cost price of the heat generated by this system would be about 25 EUR/MWh, taking into account the government subsidy for the operation of the CHP unit.
Ključne besede: food waste to energy, biogas, combined heat and power, CHP, heat pump, efficiency, conceptual design, preliminary economic assessment, sensitivity analysis
Objavljeno v DKUM: 16.02.2024; Ogledov: 3128; Prenosov: 15
.pdf Celotno besedilo (19,44 MB)
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Investigating Winter Temperatures in Sweden and Norway : Potential Relationships with Climatic Indices and Effects on Electrical Power and Energy Systems
Younes Mohammadi, Aleksey Palstev, Boštjan Polajžer, Seyed Mahdi Miraftabzadeh, Davood Khodadad, 2023, izvirni znanstveni članek

Opis: This paper presents a comprehensive study of winter temperatures in Norway and northern Sweden, covering a period of 50 to 70 years. The analysis utilizes Singular Spectrum Analysis (SSA) to investigate temperature trends at six selected locations. The results demonstrate an overall long-term rise in temperatures, which can be attributed to global warming. However, when investigating variations in highest, lowest, and average temperatures for December, January, and February, 50% of the cases exhibit a significant decrease in recent years, indicating colder winters, especially in December. The study also explores the variations in Atlantic Meridional Overturning Circulation (AMOC) variations as a crucial climate factor over the last 15 years, estimating a possible 20% decrease/slowdown within the first half of the 21st century. Subsequently, the study investigates potential similarities between winter AMOC and winter temperatures in the mid to high latitudes over the chosen locations. Additionally, the study examines another important climatic index, the North Atlantic Oscillation (NAO), and explores possible similarities between the winter NAO index and winter temperatures. The findings reveal a moderate observed lagged correlation for AMOC-smoothed temperatures, particularly in December, along the coastal areas of Norway. Conversely, a stronger lagged correlation is observed between the winter NAO index and temperatures in northwest Sweden and coastal areas of Norway. Thus, NAO may influence both AMOC and winter temperatures (NAO drives both AMOC and temperatures). Furthermore, the paper investigates the impact of colder winters, whether caused by AMOC, NAO, or other factors like winds or sea ice changes, on electrical power and energy systems, highlighting potential challenges such as reduced electricity generation, increased electricity consumption, and the vulnerability of power grids to winter storms. The study concludes by emphasizing the importance of enhancing the knowledge of electrical engineering researchers regarding important climate indices, AMOC and NAO, the possible associations between them and winter temperatures, and addressing the challenges posed by the likelihood of colder winters in power systems.
Ključne besede: winter temperatures, biogas, Atlantic Meridional Overturning Circulation, AMOC, weaking, NAO, North Atlantic Oscillation, SSA, Singular Spectrum Analysis, electrical power and energy systems
Objavljeno v DKUM: 15.02.2024; Ogledov: 242; Prenosov: 16
.pdf Celotno besedilo (8,94 MB)
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Visiting nuclear reactors : safety and security aspects
Barbara Pavlakovič Farrell, 2022, izvirni znanstveni članek

Opis: Visiting nuclear reactors is a niche tourism offer within energy (industrial) tourism, which leads tourists through areas that are not primarily meant for them. Hence, safety and security issues are even more critical in this case. This study aims to highlight different aspects of safety and security issues in nuclear power plant tours and to present measures taken to address these concerns. In addition, we studied the connection between plant visits and the public image of nuclear energy. Information was gathered through participant observation (personal visits of factory tours) and an online survey. There, we identified safety and security nuclear power plant visit protocols and a positive correlation between the visit variable and the two variables of the public image of nuclear energy, which suggests energy (industrial) tourism as a suitable tool to enhance awareness and knowledge about nuclear energy.
Ključne besede: Nuclear power plants, Energy (industrial) tourism, Safety, Security, Risk, Participant observation
Objavljeno v DKUM: 17.01.2024; Ogledov: 193; Prenosov: 10
.pdf Celotno besedilo (508,34 KB)
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Power line magnetic field deviations for three different definitions of current unbalance
Danka Antic, Anamarija Juhas, Miodrag Milutinov, 2019, strokovni članek

Opis: An estimation procedure of the public's exposure to the low-frequency magnetic field generated by overhead power lines, according to the international standards, implies measurement and an extrapolation. It is necessary to measure both the magnetic field around the lines and the current in the lines simultaneously. The extrapolation procedure implies the calculation of the maximum magnetic field that will occur when the line current achieves its maximum. The calculation relies on a proportion between the current in the power line and the magnetic field around the power line, which is valid only when the currents are balanced. Unfortunately, the standards do not cover the unbalanced cases. The relation between the current unbalance and magnetic field could improve the estimation procedure. In the literature, several different definitions of the current unbalance could be found. In this paper, a comparison of three different definitions of current unbalance and their relation to the deviation of a magnetic field are considered. The magnetic field is calculated in the vicinity of the bus bar. The same procedure could also be applied around overhead power lines. The definitions for the current unbalance used in this paper are derived from the existing definitions of the voltage unbalance. Only one of these three definitions considers phase unbalance. The relationships between current unbalance and the maximum deviation of the magnetic field are found to be proportional.
Ključne besede: magnetic field, power delivery, measurement, public exposure assessment
Objavljeno v DKUM: 22.12.2023; Ogledov: 426; Prenosov: 3
.pdf Celotno besedilo (1,86 MB)
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An alternative method of increasing the transmission performance of a conventional 110 kV cable line
Dardan Klimenta, Dragan Tasić, Miroljub S. Jevtić, 2019, strokovni članek

Opis: The purpose of this paper is to show that a significant increase in the ampacity of a 110 kV underground cable line is achievable, if a hydronic asphalt pavement system is applied along the entire line, and if the cable trench is completely filled with high thermal conductivity bedding in order to improve the conduction of heat between the line and the surface of the earth. In such a way, it would be possible to simultaneously collect and then store heat from the sun and cable line. The mutual thermal effects between the 110 kV cable line and the hydronic asphalt pavement, in the presence of solar radiation, wind-driven convection and heat emission along the earth surface, are simulated using FEM-based models for the most unfavourable summer conditions and the most common winter conditions. An adequate experimental background is also provided based on the existing measurements relevant to the thermal analysis performed. It was found that, compared to the associated base cases, the cable ampacity can be increased up to 92.3% for the most unfavourable summer conditions, and up to 60.3% for the most common winter conditions.
Ključne besede: ampacity, finite-element method, hydronic asphalt pavement, power cable, thermal analysis
Objavljeno v DKUM: 05.12.2023; Ogledov: 295; Prenosov: 4
.pdf Celotno besedilo (921,99 KB)
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