1. Energy flexibility in aluminium smelting : a long-term feasibility study based on the prospects of electricity load and photovoltaic productionMarko Bizjak, Niko Uremović, Domen Mongus, Primož Sukič, Gorazd Štumberger, Haris Salihagić Hrenko, Dragan Mikša, Stanislav Kores, Niko Lukač, 2024, original scientific article Keywords: energy flexibility, aluminium smelting, renewable energy, virtual battery, solar production Published in DKUM: 17.12.2024; Views: 0; Downloads: 5
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2. Novel GPU-accelerated high-resolution solar potential estimation in urban areas by using a modified diffuse irradiance modelNiko Lukač, Domen Mongus, Borut Žalik, Gorazd Štumberger, Marko Bizjak, 2024, original scientific article Abstract: In the past years various methods have been developed to estimate high-resolution solar potential in urban areas, by simulating solar irradiance over surface models that originate from remote sensing data. In general, this requires discretisation of solar irradiance models that estimate direct, reflective, and diffuse irradiances. The latter is most accurately estimated by an anisotropic model, where the hemispherical sky dome from arbitrary surface’s viewpoint consists of the horizon, the circumsolar and sky regions. Such model can be modified to incorporate the effects of shadowing from obstruction with a view factor for each sky region. However, state-of-the-art using such models for estimating solar potential in urban areas, only considers the sky view factor, and not circumsolar view factor, due to high computational load. In this paper, a novel parallelisation of solar potential estimation is proposed by using General Purpose computing on Graphics Processing Units (GPGPU). Modified anisotropic Perez model is used by considering diffuse shadowing with all three sky view factors. Moreover, we provide validation based on sensitivity analysis of the method’s accuracy with independent meteorological measurements, by changing circumsolar sky region’s half-angle and resolution of the hemispherical sky dome. Finally, the presented method using GPPGU was compared to multithreaded Central Processing Unit (CPU) approach, where on average a 70x computational speedup was achieved. Finally, the proposed method was applied over a urban area, obtained from Light Detection And Ranging (LiDAR) data, where the computation of solar potential was performed in a reasonable time. Keywords: solar energy, solar potential, anisotropic diffuse irradiance, LiDAR, GPGPU Published in DKUM: 17.12.2024; Views: 0; Downloads: 3
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3. The impact of financial support mechanisms and geopolitical factors on the profitability of investments in solar power plants in SloveniaIztok Gornjak, Filip Kokalj, Niko Samec, 2024, original scientific article Abstract: This article examines the impact of financial support mechanisms and geopolitical factors on the profitability of investments in solar power plants within Slovenia. The European Union’s energy policy prioritizes increases in renewable energy sources, aiming to reduce dependency on unstable and volatile fossil fuel markets. Solar power plants play a vital role in this transition. The energy policy framework also includes mechanisms and support systems to operate such facilities. This article analyzes electricity price trends over the past decade and addresses which support type—guaranteed purchase or operational support—has proven more profitable for investments in solar power plants up to 50 kW in Slovenia, considering economic and geopolitical influences on the electricity market. Although the global energy market has been affected by various significant events in recent years, it was found that the COVID-19 pandemic had minimal impact on the electricity market. In contrast, the onset of the conflict in Ukraine has contributed to rising electricity prices and has influenced the support dynamics essential for the development and sustainability of renewable energy systems. Analyses from the past decade indicate a higher return on investment in solar power plants when operational support mechanisms are chosen over guaranteed purchase support. Keywords: renewable energy sources, solar power plants, support system, investment profitability factors, electricity price Published in DKUM: 16.12.2024; Views: 0; Downloads: 8
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4. Solar irradiance stability factorsBorut Jereb, 2024, original scientific article Abstract: In the field of renewable energies, the logistical intricacies of production, as well as the use
and storage of photovoltaic energy, have become critical issues. In addition to sheer quantity, the
stability of this type of energy is a crucial factor in ensuring the reliability and consistency of power
generation. This paper defines Solar Irradiance Stability Factors (SISFs) as indicators complementing
electricity production. When planning solar energy production in each geographical area, both the
quantity and stability of solar irradiance are necessary for exploitation and determining the quality of
solar irradiance. While the average production of solar energy per unit area in each time interval is a
widely used parameter in daily practice, the observation of the amplitude of solar irradiance and its
influence on energy production in the observed time interval is currently still rare. The SISFs defined
in this article are new metrics that mainly depend on the meteorological variability in an area, and
the observed time intervals should be in the range of seconds, minutes, or even hours. Larger time
intervals are not helpful for the stability of solar irradiance in energy production and logistics from
the source to the destination. They provide a complementary and more accurate measure of how
suitable a particular geographical area is for producing solar energy.
Keywords: solar irradiance, stability metrics, photovoltaic energy, meteorological variability, geographical area Published in DKUM: 23.09.2024; Views: 0; Downloads: 2
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5. Investigating the influence of reflective materials on indoor thermal environment and solar reflectance in buildingsJihui Yuan, Yasuhiro Shimazaki, Masaki Tajima, Shaoyu Sheng, Zhichao Jiao, Marko Bizjak, 2024, original scientific article Abstract: This in-depth study explores the intricate dynamics of reflective materials, emphasizing their impact on the indoor thermal environment and urban heat island (UHI) mitigation. Examining diffuse highly reflective (DHR), general reflective (GR), and retro-reflective (RR) materials on a simplified building model during summer days, the research utilizes outdoor experiments to analyze air and surface temperatures, as well as solar radiation. Prioritizing key metrics—mean radiant temperature (MRT), operative temperature (OT), and solar reflectance (ρ)—the study uncovers nuanced distinctions in DHR, GR, and RR materials. Solar reflectance calculations consistently show higher values for DHR and RR materials compared to GR material, highlighting reflectance's pivotal role in influencing surface temperatures and indoor thermal environment. When evaluating the impact of exterior wall materials on building temperatures, RR material with a 76% reflectance performs similarly to DHR material (82%). Notably, with a 6% lower reflectance in RR, the temperature contrast between external and internal walls is only about 1.5 °C at its maximum, underscoring RR's effectiveness as an outer wall material for UHI mitigation and building energy conservation, surpassing both DHR and GR materials. Keywords: urban heat island, reflective materials, indoor thermal environment, solar reflectance, simplified building model Published in DKUM: 23.08.2024; Views: 110; Downloads: 9
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6. Prices of conventional and renewable energy as determinants of sustainable and secure energy development : regression model analysisSandi Knez, Goran Šimić, Anica Milovanović, Sofia Starikova, Franc Željko Županič, 2022, original scientific article Abstract: Background
The prices of energy resources are important determinants of sustainable energy development, yet associated with significant unknowns. The estimates of the impact of prices of energy products in the domestic market (for domestic consumers) are rare—hence the importance and novelty of this research. Therefore, the main goal of the paper is to assess the impact of domestic prices of gasoline, gas, coal, and solar energy on sustainable and secure energy future.
Methods
The research includes 14 countries (of which 7 are developed and 7 are developing countries) and a period of 5 years (2014–2018). The model also includes discrete variables: level of development (developing or developed), and the fact as to whether the country is an energy exporter or not. For the purposes of analysis, the following elements were used: Panel Data Analysis, Linear regression (with random and fixed effects), Durbin–Wu–Hausman test, and Honda test, with the use of R-studio software for statistical computing.
Results
The research showed that the biggest negative impact on energy sustainability was recorded by an increase in the price of coal and the smallest one by an increase in the price of solar energy. An increase in the price of gasoline has a positive impact, while an increase in the price of gas has no impact. The basic methodological result showed that the fixed effects linear model is more accurate than the random effect model.
Conclusions
The results of the paper, important as a sustainable energy policy recommendation, showed that the impact of changes in energy product prices is significantly greater in developing countries, but that the status of the country as an energy exporter has no significance. In addition, the paper points to the need to intensify the research on the assessment of the impact of energy product prices for domestic consumers on their ability to pay that price, because with a certain (so far undefined) increase in energy product prices, a certain group of domestic consumers moves into a category that is not in line with sustainable energy development and is extremely undesirable in every respect—energy poverty. Keywords: sustainable energy development, conventional energy prices, solar prices, developing countries, R-studio Published in DKUM: 26.06.2024; Views: 133; Downloads: 14
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7. Evaluation of system for economically viable thermal power plant operationMartin Bricl, Jurij Avsec, 2019, original scientific article Abstract: 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. Keywords: thermal power plant, economically viable operation, a solar central receiver system, renewable technologies, flue gas desulphurization Published in DKUM: 22.02.2024; Views: 360; Downloads: 21
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8. Cotton woven fabrics as protective polymer materials against solar radiation in the range of 210–1200 nmPolona Dobnik-Dubrovski, Darinka Fakin, Alenka Ojstršek, 2023, original scientific article Abstract: The proposed paper describes the influence of woven fabric constructional parameters (type of weave, relative fabric density) and colouration (obtained by eco-friendly dyeing) on the solar transmittance of cotton woven fabrics in the range of 210-1200 nm. The cotton woven fabrics in their raw state were prepared according to Kienbaum's setting theory, at three levels of relative fabric density and three levels of the weave factor, and then exposed to the dyeing process with natural dyestuffs (beetroot, walnut leaves). After ultraviolet/visible/near-infrared (UV/VIS/IRA) solar transmittance and reflection in the range of 210-1200 nm were recorded, the influence of the fabric construction and colouration were analysed. The guidelines for fabric constructor were proposed. The results show that the walnut-coloured satin samples at the third level of relative fabric density provide the best solar protection in the whole solar spectrum. All the tested eco-friendly dyed fabrics offer good solar protection, while only raw satin fabric at the third level of relative fabric density can be classified as solar protective material with even better protection in IRA region than some coloured samples. Keywords: fabric engineering, solar protection, woven fabric structure, natural dyeing of polymer material, testing Published in DKUM: 15.02.2024; Views: 296; Downloads: 17
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9. High-resolution spatiotemporal assessment of solar potential from remote sensing data using deep learningMitja Žalik, Domen Mongus, Niko Lukač, 2024, original scientific article Keywords: deep learning, fully convolutional neural network, LiDAR data, digital elevation model, solar energy, solar potential Published in DKUM: 26.01.2024; Views: 244; Downloads: 8
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10. Thermal analysis and application of roll bond solar absorbers for heating and cooling in residential buildingsJurij Avsec, Daniel Brandl, Helmut Schober, Urška Novosel, Janko Ferčec, 2019, original scientific article Abstract: The use of renewable energy sources will have to be increased significantly over the coming decades. The potential of solar energy in Slovenia represents the largest share of renewable energy sources. This article shows the use of roll bond solar absorbers for the heating and cooling of houses. For this purpose, we performed a numerical simulation of solar absorbers and theoretical calculations. Keywords: roll bond technology, STAF panel, solar technology, heat pump Published in DKUM: 05.12.2023; Views: 306; Downloads: 5
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