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Abstract: 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.
Keywords: zrak, onesnaženost, kakovost, PM delci, SEM
Published in DKUM: 19.09.2024; Views: 0; Downloads: 9
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Abstract: 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.
Keywords: geothermal energy, geothermal gravity heat pipe, numerical modelling, single well closed-loop heat exchanger
Published in DKUM: 03.09.2024; Views: 41; Downloads: 6
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Abstract: This study examines the considerable volume of food waste generated annually in Slovenia, which amounted to over 143,000 tons in 2020. The analysis shows that 40% of food waste consists of edible parts, highlighting the potential for reduction through increased consumer awareness and attitudes towards food consumption. The study shows that the consumption phase contributes the most to waste food (46%), followed by primary production (25%) and processing/manufacture (24%). The study addresses various thermodynamic processes, in particular, thermal conversion methods, such as torrefaction pyrolysis and hydrothermal carbonization, which optimize energy potential by reducing the atomic ratio (H/C) and (O/C), thereby increasing calorific value and facilitating the production of solid fuels. The main results show the effectiveness of torrefaction, pyrolysis and hydrothermal carbonization (HTC) in increasing the energy potential of food waste.
Keywords: energy, thermodynamic conversions, pyrolysis, torrefaction, hydrothermal carbonization, food waste, energy potential, chemical composition
Published in DKUM: 28.08.2024; Views: 53; Downloads: 6
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Abstract: In this work, the thermochemical properties of municipal solid waste (MSW) are studied using the torrefaction process as the main method for investigation. Torrefaction experiments were carried out using an electric laboratory furnace, at temperatures of 200, 250, and 300 °C. The residence time was set to 90 min. Proximate and ultimate analysis were performed on the torrefied MSW samples and compared with the properties of the raw MSW samples. In addition, the thermal properties of the obtained torrefied MSW samples were evaluated by thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). The following could be stated: the obtained results showed that mass and energy yields (MY and EY, respectively) decrease with increasing when torrefaction temperature, while the heating values (HHV) increased under the same conditions (from 24.3 to 25.1 MJ/kg). Elemental analysis showed an increase in carbon content (C), from 45.7 ± 0.9 to 52.8 ± 1.05 wt.%, and decrease in oxygen content (O), from 45.6 ± 0.9 to 39.5 ± 0.8 wt.%, when torrefaction temperature is increased, which is consistent with the general definition of the torrefaction process. In addition, enhancement factors (EFs) and fuel ratios (FRs) were calculated, which ranged from 1.00 to 1.02 and 0.16 to 0.23, respectively. Some anomalies were observed during the thermal analysis, which are assumed to be related to the composition of the selected MSW. This study therefore shows that torrefaction pretreatment can improve the physicochemical properties of raw MSW to a level comparable to coal, and could contribute to a better understanding of the conversion of MSW into a valuable, solid biofuel.
Keywords: biomass, municipal solid waste, torrefication, energy yield, thermogravimetric analysis
Published in DKUM: 10.05.2024; Views: 255; Downloads: 19
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Abstract: The article presents a new carbon-free heat production technology for district heating, which consists of a combined heat and power generation fuel cell (FC CHP) with CO2 capture and a two-stage cascade high-temperature heat pump (TCHHP). The FC generates heat and electricity, the latter being used to drive the compressors of the TCHHP. During the winter period, the water temperature achieved can occasionally be too low, so it would be heated up with hydrogen gas boilers. The hydrogen would be produced by reforming natural gas, synthetic methane, or biogas. The results are presented with natural gas utilization—the ratio between the obtained heat flow transferred directly to the water for district heating and the input heat flow of natural gas. In the case of a return water temperature of 60 °C and district heating temperature of 85 °C, the TCHHP, whose heat source is groundwater, achieves plant efficiency of 270.04% in relation to the higher heating value (HHV) and 241.74% in relation to the lower heating value (LHV) of natural gas. A case with a TCHHP whose heat source is low-temperature geothermal water achieves a plant efficiency of 361.36% in relation to the HHV and 323.49% in relation to the LHV.
Keywords: carbon-free, decarbonization of district heating systems, fuell cell, high-temperature district heating, high-temperature heat pump
Published in DKUM: 10.05.2024; Views: 233; Downloads: 17
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