1. Quantifying power system frequency quality and extracting typical patterns within short time scales below one hourYounes Mohammadi, Boštjan Polajžer, Roberto Chouhy Leborgne, Davood Khodadad, 2024, izvirni znanstveni članek Ključne besede: quantifying power system frequency quality, statistical indices, pattern extracting, machine learning, short time scales, renewable energy sources
Objavljeno v DKUM: 23.08.2024; Ogledov: 50; Prenosov: 4
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2. Methods and models for electric load forecasting : a comprehensive reviewMahmoud A. Hammad, Borut Jereb, Bojan Rosi, Dejan Dragan, 2020, izvirni znanstveni članek Opis: Electric load forecasting (ELF) is a vital process in the planning of the electricity industry and plays a crucial role in electric capacity scheduling and power systems management and, therefore, it has attracted increasing academic interest. Hence, the accuracy of electric load forecasting has great importance for energy generating capacity scheduling and power system management. This paper presents a review of forecasting methods and models for electricity load. About 45 academic papers have been used for the comparison based on specified criteria such as time frame, inputs, outputs, the scale of the project, and value. The review reveals that despite the relative simplicity of all reviewed models, the regression analysis is still widely used and efficient for long-term forecasting. As for short-term predictions, machine learning or artificial intelligence-based models such as Artificial Neural Networks (ANN), Support Vector Machines (SVM), and Fuzzy logic are favored.
Ključne besede: methods, models, electric load forecasting, modeling electricity loads, electricity industry, power management, logistics
Objavljeno v DKUM: 22.08.2024; Ogledov: 95; Prenosov: 6
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3. Optimization of a circular planar spiral wireless power transfer coil using a genetic algorithmNataša Prosen, Jure Domajnko, 2024, izvirni znanstveni članek Opis: Circular planar spiral coils are the most important parts of wireless power transfer systems. This paper presents the optimization of wireless power transfer coils used for wireless power transfer, which is a problem when designing wireless power transfer systems. A single transmitter coil transfers power to a single receiving side. The performance of the wireless power transfer system depends greatly on the size and shape of the wireless power transfer system. Therefore, the optimization of the coils is of the utmost importance. The main optimization parameter was the coupling coefficient between the transmitter and the receiver coil in the horizontally aligned and misaligned position. A genetic evolutionary algorithm was used to optimize the coil, according to the developed cost function. The algorithm was implemented using the MATLAB programming language. The constraints regarding the design of the coils are also presented for the problem to be analyzed correctly. The results obtained using the genetic algorithm were first verified using FEM simulations. The optimized coils were later fabricated and measured to confirm the theory.
Ključne besede: wireless power transfer, coil optimization, genetic algorithm, coupling coefficient measurement
Objavljeno v DKUM: 14.08.2024; Ogledov: 77; Prenosov: 4
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5. Lower-limb muscle contractile properties, explosive power and the subjective response of elite soccer players to the Covid-19 lockdownArmin Paravlić, Boštjan Šimunič, Saša Pišot, Matej Kleva, Kaja Teraž, Matjaž Vogrin, Uroš Marušič, Rado Pišot, 2022, izvirni znanstveni članek Opis: The present study examined the effects of the lockdown period on basic anthropometric measures, countermovement jumping performance, skeletal muscle contractile properties derived from tensiomyography (TMG), injury incidence, and self-assessed general well-being in elite soccer players. A total of 266 players were assessed before (PRE) and 32 players were reassessed 11 days after (POST) the COVID-19 period. Significant changes in the TMG parameters were observed POST compared to PRE: contraction time (Tc) increased from 6% to 50% in vastus lateralis [VL] (p = 0.009) and biceps femoris [BF] (p < 0.001), respectively; whereas radial displacement (Dm) increased for 19% in BF (p = 0.036) and 17% in VL (p < 0.001), respectively. Jumping performance remained unchanged from PRE to POST In addition, athletes rated the lockdown period as a positive event and felt psychologically better during the lockdown, primarily because they spent more time with family members and friends. Although there were no differences in any of the variables describing lower limb muscle power following the two-month lockdown, the altered contractile properties of the assessed muscles suggest suboptimal conditioning of the football players.
Ključne besede: football, male football, power, explosive power, CMJ, tensiomyography, SJ, coronavirus, pandemics, lockdown
Objavljeno v DKUM: 11.07.2024; Ogledov: 80; Prenosov: 3
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6. Utilisation of renewable electricity to produce synthetic methaneKlemen 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: 203; Prenosov: 9
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7. Dimensional deviations in Ti-6Al-4V discs produced with different process parameters during selective laser meltingSnehashis 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: 219; Prenosov: 9
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8. Evaluation of system for economically viable thermal power plant operationMartin 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: 360; Prenosov: 13
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9. Food Waste to Energy through Innovative Coupling of CHP and Heat PumpJan 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: 3257; Prenosov: 19
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10. Investigating Winter Temperatures in Sweden and Norway : Potential Relationships with Climatic Indices and Effects on Electrical Power and Energy SystemsYounes 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: 311; Prenosov: 21
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