1. Spatiotemporal analysis and physicochemical profiling of ▫$PM_10$▫ and ▫$PM_2.5$ ▫ in SloveniaMaja Ivanovski, Ivan Anžel, Darko Goričanec, Danijela Urbancl, 2025, izvirni znanstveni članek Opis: Particulate matter (PM10 and PM2.5) is a key contributor to urban air pollution and poses significant health risks, particularly in densely populated areas. While conventional air quality monitoring focuses on particle size and concentration, this study emphasizes the importance of understanding chemical composition and emission sources for effective air pollution management. PM samples were collected between 2019 and 2022 at two locations in the Republic of Slovenia: a traffic-dominated urban site and an industrial area. Annual average PM10 concentrations ranged from 14 to 34 μg/m3, and those of PM2.5 ranged from 9 to 22 μg/m3. In addition to decreasing annual concentrations, a notable reduction in exceedance days was observed between 2019 and 2022, indicating the effectiveness of recent air quality improvement measures. Meteorological data and statistical models were used to assess environmental influences on PM variability. Advanced SEM-EDS analysis revealed substantial seasonal and spatial differences in particle composition, with key elements such as silicon (4.3–28.4%), carbon (13.1–61.7%), and trace amounts of lead and zinc varying across sites and particle types. Mineral dust (Si, Al, Ca, Fe, Mg), originating from soil resuspension, construction, and Saharan dust, was dominant. Combustion-related particles containing C, Pb, Zn, and Fe oxides were associated with vehicle emissions, industrial processes, and biomass burning. Secondary aerosols, such as sulphates and nitrates, showed seasonal trends, with higher concentrations in summer and winter, respectively. The results confirm that PM levels are driven by complex interactions between local emissions, weather conditions, and seasonal dynamics. The study supports targeted policy measures, particularly regarding residential heating and traffic emissions, to improve air quality. Ključne besede: air pollution, air quality, PM particles, SEM-EDS, Slovenia Objavljeno v DKUM: 30.05.2025; Ogledov: 0; Prenosov: 1
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2. Comparison of the new refrigerant R1336mzz(E) with R1234ze(E) as an alternative to R134a for use in heat pumpsJan Drofenik, Danijela Urbancl, Darko Goričanec, 2022, izvirni znanstveni članek Opis: R134a is currently the most widely used refrigerant, whose problem is the high value of the
global warming potential, and which will have to be replaced in the near future. Thus far, R1234ze(E)
has proven to be the most suitable alternative, but it is slightly flammable. Recently, R1336mzz(E) has
emerged as a possible alternative. During the research, the mentioned refrigerants were compared
with simulations using the Aspen Plus software package in the case of using groundwater as a heat
source. It was found that R1336mzz(E) could be a suitable alternative to R134a since the highest
value of coefficient of performance was obtained using it. However, it must be superheated with an
internal heat exchanger. The problem with using an internal heat exchanger is that the superheating
of the refrigerant vapors affects the isentropic efficiency of the heat pump compressor negatively and,
consequently, lowers the COP value of the heat pump. It has been shown that a one percent decrease
in isentropic efficiency results in a one percent decrease in the COP value. Ključne besede: heat pump, internal heat exchanger, HFO, HFC alternative, GWP Objavljeno v DKUM: 15.05.2025; Ogledov: 0; Prenosov: 0
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3. Improving lignocellulosic and non-lignocellulosic biomass characteristics through torrefaction processMaja Ivanovski, Danijela Urbancl, Aleksandra Petrovič, Janja Stergar, Darko Goričanec, Marjana Simonič, 2022, izvirni znanstveni članek Opis: In this study, three locally available biomasses, namely miscanthus, hops, sewage sludge,
and additionally, their mixtures, were subjected to the torrefaction process to improve their fuel
properties. The torrefaction process was conducted at 250–350 ◦C and 10–60 min in a nitrogen
(N2) environment. The torrefaction temperature and time were studied to evaluate the selected
biomass materials; furthermore, heating values, mass and energy yields, enhancement factors,
torrefaction severity indexes (TSI), and energy-mass co-benefit indexes (EMCI) were calculated. In
addition, thermogravimetric (TGA) and Fourier transform infrared analyses (FTIR) were performed
to characterize raw and torrefied biomass under the most stringent conditions (350 ◦C and 60 min).
The results showed that with increasing torrefaction temperature and duration, mass and energy
yields decreased, and heating values (HHVs) increased for all studied biomasses. The results of the
TSI and EMCI indexes showed that the optimum torrefaction conditions were as follows: 260 ◦C
and 10 min for pure miscanthus and hops, whilst this could not be confirmed for the sewage sludge.
Furthermore, the combination of sewage sludge and the above-mentioned types of lignocellulosic
biomass exhibited better fuel properties than sewage sludge alone. Ključne besede: lignocellulosic biomass, sewage sludge, torrefication, thermogravimetry, TSI Objavljeno v DKUM: 10.04.2025; Ogledov: 0; Prenosov: 14
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4. Ocena potenciala medsektorske integracije v Sloveniji s poudarkom vključevanja prometnega sektorja : zaključno poročiloAndreja Nemet, Miloš Bogataj, David Hvalec, Franco Krog, Klemen Rola, Sven Gruber, Jurij Avsec, Danijela Urbancl, Darko Goričanec, Zdravko Kravanja, 2025, končno poročilo o rezultatih raziskav Ključne besede: medsektorska integracija, prometni sektor Objavljeno v DKUM: 03.04.2025; Ogledov: 0; Prenosov: 6
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5. Cu(II) and Ni(II) adsorption on torrefied wood waste biomassMarjana Simonič, Darko Goričanec, Aleksandra Petrovič, Ilda Silić, Danijela Urbancl, 2025, izvirni znanstveni članek Opis: The aim of the research was to study the torrefaction processes of wood biomass, compare the product characteristics at different torrefaction temperatures, and assess both moisture adsorption on raw and torrefied samples, as well as metal (Cu(II) and Ni(II)) adsorption on torrefied biomass. The novelty of the research was to investigate whether the presence of adsorbed metals in torrefied biomass significantly affects the energetic properties of the torrefied biomass, compared to torrefied biomass without metals. First, wood samples were torrefied at temperatures of 250 °C, 350 °C, and 400 °C. Following torrefaction, thermogravimetric analysis (TGA) was performed to evaluate mass loss and thermal stability. Next, changes in surface functional groups were examined, and higher heating values (HHV) were measured to assess the energy content. The results showed that torrefaction significantly increased the hydrophobicity of the biomass, leading to reduced moisture adsorption and enhanced material properties. Additionally, the adsorption of Cu(II) and Ni(II) ions on torrefied biomass was investigated. The results showed that the adsorption efficiency for Cu(II) was higher, reaching 62.4%, compared to Ni(II) at 21.2%. The adsorption process followed a pseudo-second-order kinetic model, which indicated that chemisorption was the dominant mechanism. Ključne besede: adsorption, torrefication, nitrogen atmosphere, metals Objavljeno v DKUM: 12.03.2025; Ogledov: 0; Prenosov: 6
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6. Advancing energy recovery: evaluating torrefaction temperature effects on food waste properties from fruit and vegetable processingAndreja Škorjanc, Sven Gruber, Klemen Rola, Darko Goričanec, Danijela Urbancl, 2025, izvirni znanstveni članek Opis: Most organic waste from food production is still not used for energy production. From the perspective of energy production, one option is to valorise the properties of organic waste. The fruit juice industry is growing rapidly and generates large amounts of waste. One of the main wastes in food and fruit juice processing is peach pits and apple peels. The aim of this study was to analyse the influence of torrefaction temperature on the properties of food waste, namely apple peels, peach pits and pea shells, in order to improve their energy value and determine their potential for further use and valorisation as a renewable energy source. The aim was to analyse the influence of different torrefaction temperatures on the heating value (HHV), mass yield (MY) and energy yield (EY) in order to better understand the behavior of the thermal properties of individual selected samples. The torrefaction process was carried out at temperatures of 250 ◦C, 350 ◦C and 450 ◦C. The obtained biomass was compared with dried biomass. For apple peels, HHV after torrefaction was (28 kJ/kg), MY decreased by (66–34%), while EY fell by (97–83%). Peach pits, despite a higher HHV after torrefaction (18 kJ/kg), achieved low MY (38–89%) and EY (59–99%), which reduces their efficiency in biochar production. Pea peels had EY (82–97%) and a lower HHV after torrefaction (11 kJ/kg), but their high ash content limits their wider use. The results confirm that, with increasing temperature, MY and EY for all selected biomasses decrease, which is a consequence of the degradation of hemicellulose and cellulose and the loss of volatile compounds. In most cases, increasing the torrefaction temperature improved the resistance to moisture adsorption, as this is related to the thermal process that causes structural changes. The results showed that the torrefaction process improved the hydrophobic properties of the biomass samples. Temperature was seen to have a great impact on mass energy efficiency. Apple peels generally had the highest mass and energy yield. Ključne besede: torrefaction, food waste, energy from waste, higher heating value, energy potential Objavljeno v DKUM: 07.02.2025; Ogledov: 0; Prenosov: 16
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7. Analiza onesnaženosti zraka z delci PM10 in drobnimi delci PM2,5 na območju Slovenije v obdobju med 2019 in 2022Lia Čotar, 2024, diplomsko delo Opis: Onesnažen zrak je eden najbolj perečih problemov sodobnega časa, zato je kontrola koncentracije onesnažil ključna za doseganje želene kvalitete življenja. Nadzor kakovosti zraka v Sloveniji opravlja Javna agencija Republike Slovenije za okolje (ARSO) in podatke redno objavlja na svoji spletni strani. Namen diplomske naloge je bil primerjati vrednosti onesnažil PM10 in PM2,5 v zraku v določenem časovnem obdobju. Analiza je bila izvedena na podlagi javno dostopnih podatkov na dveh merilnih mestih v Sloveniji, ki se razlikujeta po gostoti poselitve, reliefu in meteoroloških parametrih. Prvo merilno mesto je bilo prometno in urbano središče, drugo pa se je nahajalo v bližini večjega termoenergetskega objekta. Ugotovljeno je bilo, da se onesnaženost zraka s PM10 in PM2,5 tekom let zmanjšuje in da je onesnaženost s PM10 in PM2,5 večja na merilnem mestu z večjo gostoto poselitve, večjo količino prometa in manj ugodnim reliefom, ki otežuje izločanje onesnažil iz ozračja. Poleg tega je bila koncentracija delcev na obeh merilnih mestih najvišja pozimi, zaradi uporabe kurilnih peči v gospodinjstvih, ki so glavni vir izpustov, in najnižja poleti. Pandemija COVID-19 na zmanjšanje emisij delcev ni imela večjega vpliva.
Nazadnje je bila izvedena še SEM-EDS analiza filtrov. Najpogosteje zastopani elementi na obeh merilnih mestih so bili ogljik, kisik in silicij, pri čemer je bila koncentracija ogljika na prvem merilnem mestu več kot dvakrat večja, najbrž zaradi večje količine izpustov iz prometa. Ostali elementi so bili na obeh merilnih mestih zastopani v približno enakem razmerju in jih gre predpisati različnim naravnim in antropogenim procesom. Ključne besede: zrak, onesnaženost, kakovost, PM delci, SEM Objavljeno v DKUM: 19.09.2024; Ogledov: 0; Prenosov: 29
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8. Primerjava toplotnih črpalk z različnim hladilnim medijemBlaž Vesenjak, 2024, diplomsko delo Opis: Namen diplomskega dela je z računalniškimi simulacijami pridobiti rezultate, ki omogočajo primerjavo ključnih parametrov, kot so hladilni medij, pretoki snovi, koeficient učinkovitosti (COP) in stroški. Cilj je pomagati podjetjem in uporabnikom toplotnih črpalk pri izbiri najustreznejše naprave za njihove potrebe. Toplotne črpalke so ključne tako za stanovanjske objekte, kjer zagotavljajo udobje in toploto, kot tudi za industrijo, kjer se uporabljajo za različne procese, kot so ogrevanje materialov, destilacija in koncentriranje raztopin.
Pri izbiri hladilnega medija smo upoštevali več dejavnikov, zlasti okoljske vplive, saj smo želeli delati s snovmi, ki bodo v prihodnosti še vedno dovoljene. Preverili smo njihovo vnetljivost, toksičnost ter vrednosti ODP in GWP, ki so ključne za določanje podnebnih vplivov. Eksperimentalni del naloge je bil večinoma izveden s pomočjo programske opreme Aspen Plus, kjer smo izvajali simulacije različnih toplotnih črpalk in analizirali njihove rezultate. Pri osnovnih simulacijah smo fiksirali masni pretok vode pri 1000 kg/h in simulacije optimizirali glede na hladilno sredstvo pri treh različnih temperaturnih režimih izstopne vode (40 °C, 50 °C in 60 °C). Prva analiza je pokazala, da so hladilni mediji z nižjimi masnimi pretoki učinkovitejši pri prenosu toplote, kar vpliva na celotno učinkovitost toplotnih črpalk. Pri analizi občutljivosti pa smo ugotovili, da je COP na splošno višji pri nižjih izstopnih temperaturah vode, optimalen pretok grelne vode pa zagotavlja najboljše ravnovesje med prenosom toplote in energijsko porabo, kar vodi do najvišjega COP. Ključne besede: subkritična toplotna črpalka, transkritična toplotna črpalka, hladilni medij, koeficient učinkovitosti, okoljski vplivi Objavljeno v DKUM: 10.09.2024; Ogledov: 19; Prenosov: 28
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9. Numerical analysis of low-enthalpy deep geothermal energy extraction using a novel gravity heat pipe designUrban Gselman, Vid Peršak, Darko Goričanec, 2024, izvirni znanstveni članek Opis: Geothermal energy, derived from the Earth’s internal heat, can be harnessed due to the
geothermal gradient between the Earth’s interior and its surface. This heat, sustained by radiogenic
decay, varies across regions, and is highest near volcanic areas. In 2020, 108 countries utilised
geothermal energy, with an installed capacity of 15,950 MWe for electricity and 107,727 MWt for
direct use in 2019. Low-enthalpy sources require binary systems for power production. Open-loop
systems face issues like scaling, difficult water treatment, and potential seismicity, while closed-loop
systems, using abandoned petroleum or gas wells, reduce costs and environmental impacts greatly.
The novel geothermal gravity heat pipe (GGHP) design eliminates parasitic power consumption by
using hydrostatic pressure for fluid circulation. Implemented in an abandoned well in north-east
(NE) Slovenia, the GGHP uses a numerical finite difference method to model heat flow. The system
vaporises the working fluid in the borehole, condenses it at the surface, and uses gravitational flow
for circulation, maintaining efficient heat extraction. The model predicts that continuous maximum
capacity extraction depletes usable heat rapidly. Future work will explore sustainable heat extraction
and potential discontinuous operation for improved efficiency.
Ključne besede: geothermal energy, geothermal gravity heat pipe, numerical modelling, single well closed-loop heat exchanger Objavljeno v DKUM: 03.09.2024; Ogledov: 41; Prenosov: 15
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10. Recent advances in ejector-enhanced vapor compression heat pump and refrigeration systems : a reviewSven Gruber, Klemen Rola, Danijela Urbancl, Darko Goričanec, 2024, izvirni znanstveni članek Opis: The incorporation of ejectors into heat pump and refrigeration cycles has been the subject
of growing interest, largely due to their simple structure, high reliability, and cost-effectiveness. This
paper investigates the recent advancements in novel design concepts of ejector-enhanced vapor
compression heat pump and refrigeration cycles. An overview of novel single-stage and twostage compression cycles utilizing a single or multiple ejectors is provided. First, the system setup,
operational principles, description, and figures of the existing schemes are provided. Second, the
main results, such as the coefficient of performance (COP), volumetric heating capacity and exergy
destruction, are discussed. In conclusion, the paper presents a coherent summary of the current
developments, future prospects, and the current knowledge gap. A plethora of research is present
in developing theoretical systems with high efficiency. However, experimental tests for real-life
implementations are limited. This review aims to provide the reader with an overview of recent
theoretical and experimental studies.
Ključne besede: ejector, heat pump, refrigeration, vapor compression system, review Objavljeno v DKUM: 03.09.2024; Ogledov: 51; Prenosov: 20
Celotno besedilo (10,04 MB) |