1. Numerical analysis of low-enthalpy deep geothermal energy extraction using a novel gravity heat pipe designUrban Gselman, Vid Peršak, Darko Goričanec, 2024, original scientific article 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: 13
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2. Proizvodnja električne energije z geotermično gravitacijsko toplotno cevjo : magistrsko deloUrban Gselman, 2023, master's thesis Abstract: Geotermična energija v svetu po deležu proizvedene električne energije, glede na svojo nizkoogljičnost in prilagodljivost potrebam omrežja, zaseda nezavidljivo pozicijo. Glavne omejitve za razvoj projektov na tem področju so zahtevna razširitev na večje moči, nizke temperature blizu površja, pomanjkanje tehnoloških rešitev za izkoriščanje toplote globokih vrtin in negotovosti produktivnosti. Kot dodatek je iz večine geotermičnih polj možno črpati tudi ogljikovodike, kar pa je veliko manj tvegana investicija napram geotermični energiji. V magistrski nalogi obdelujemo projekt Pilotna geotermična elektrarna na obstoječi plinski vrtini Pg-8, kjer je implementirana tehnologija GGTC, nova tehnologija za izkoriščanje toplote globokih vrtin na obstoječih neproduktivnih plinskih ali naftnih vrtinah. Namen magistrskega dela je opisati delovanje geotermične elektrarne in tehnologije GGTC ter preveriti potrebnost modelnih programskih okolij za predvidevanje glavnih obratovalnih parametrov. Narejen je bil matematični model z uporabo polinomskega približka termodinamskega modela REFPORP ter simulacija v programskem okolju Aspen plus z uporabo termodinamskega modela UNIFAC in REFPORP. Izvedene so bile občutljivostne analize vhodnega tlaka v turbino, tlaka kondenzacije in masnega pretoka delovnega fluida. Rezultati simulacije in modela so bili analizirani, tako kot tudi odstopanja med modelom in simulacijo z uporabo obeh termodinamskih modelov stanja. Rezultati kažejo na maksimum proizvedene mehanske moči na turbini pri vhodnem tlaku 65 bar v matematičnem modelu in 85 bar ali 95 bar v simulaciji z uporabo REFPROP ali UNIFAC termodinamskega modela stanja. Podobno doseže maksimum potreben toplotni tok iz vrtine, in sicer pri vrednostih 37,5 bar v simulaciji z uporabo UNIFAC modela in 21 bar v matematičnem modelu in simulaciji z uporabo REFPROP modela. Ugotovljeno je bilo, da so relativna odstopanja občutljivostnih analiz ob mejah analiziranih področij dosegala vrednosti 40,7 %, generalno pa so se relativna odstopanja dosegala vrednosti do 10 %. Zaključeno je bilo, da polinomski približek termodinamskih veličin delovnega fluida ni zadovoljiv za izvajanje občutljivostnih analiz. Zaradi smernic razvoja na področju Slovenije, opredeljenih v NEPN-u so prihodnja raziskovanja na tem področju družbeno koristna.
Keywords: geotermična energija, ORC, GGTC, občutljivostna analiza, proizvodnja električne energije, Pg-8
Published in DKUM: 21.12.2023; Views: 366; Downloads: 0
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3. Hollow-Fibre forward osmosis membrane module stress tests : diplomsko delo univerzitetnega študijskega programa I. stopnjeUrban Gselman, 2020, undergraduate thesis Abstract: Humanity has recently begun to realize that resources on Earth are not infinite and that, consequently, it is imperative for us to start to use them sustainably and renewably. Aligned with this mentality, forward osmosis has been rigorously studied in the past few decades with some commercially available products already on the market. This thesis used one of those products, namely, the Aquaporin HFFO 2 membrane module, and assessed its stability in sodium metabisulfite solution and high salinity without flowing solutions under long-term storage conditions. The sodium metabisulfite preservation part was devised to upgrade the existing guidelines for prolonged storage of fouled membranes and the osmotic drying project was looking at a scenario where the modules would be exposed to a salt solution on the draw side and no flowing wastewater on the feed side. The assessments were made on pristine HFFO 2 membrane modules and with RO water prepared on site. Their performance after exposure was measured with an internal quality control procedure, producing values for water flux, reverse salt flux, normalized reverse salt flux and temperature, which were later compared with the initial values. The findings show us that the sodium metabisulfite and increased salinity have a detrimental effect on the membrane inside of the module, but not enough to be considered damaged and would need to be discarded. More valuable results will be gained if the measurements are done on fouled membranes, as the biggest factor in increasing the lifetime of a module is preventing algal and bacterial growth
Keywords: forward osmosis, Aquaporin HFFO 2, sodium metabisulfite, osmotic drying, prolonged storage.
Published in DKUM: 24.09.2020; Views: 983; Downloads: 18
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