1. Energetsko načrtovanje hladilnice jabolk : magistrsko deloŽan Bregar, 2024, master's thesis Abstract: V okviru magistrske naloge smo se posvetili projektiranju hladilnice za skladiščenje jabolk, kjer smo podrobno raziskali ključne vidike načrtovanja in izvedbe kompleksnih sistemov za ohranjanje kakovosti sadja. Naša analiza je zajemala pregled uporabljene opreme za hlajenje, izračune potrebne hladilne moči, določitev optimalne debeline izolacije ter temeljito preučevanje osvetlitve celotne hladilnice. Pravilno načrtovanje hladilnic ima ključno vlogo pri ustvarjanju optimalnih pogojev za shranjevanje jabolk, kar omogoča dolgoročno ohranjanje svežine in kakovosti sadja. Izračuni potrebnih hladilnih moči in debeline izolacije nudijo trdne osnove za tehnično izvedbo hladilnice, ki učinkovito vzdržuje predpisane temperature in vlago.
Keywords: hladilnice, hladilna moč, izolacija, strojna oprema, skladiščenje
Published in DKUM: 12.06.2024; Views: 156; Downloads: 29
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3. Multi-purpose use and lifecycle analysis of solar panelsDušan Strušnik, Urška Novosel, Jurij Avsec, 2020, original scientific article Abstract: The combined use of renewable energy technologies and alternative energy technologies is a promising approach to reduce global warming effects throughout the world. In this paper, the solar panel is used in combination with a heat pump or with biomass sources to obtain heat, electricity, and hydrogen. Based on the Rankine thermodynamic cycle, hydrogen could be obtained from water with electrolysis and the CuCl thermochemical cycle. Furthermore, this study contains a life cycle analysis of solar panels.
Keywords: heat pump, life cycle analysis, Rankine cycle, solar panel, thermochemical cycle
Published in DKUM: 01.12.2023; Views: 393; Downloads: 4
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4. HRSG system description and water-steam analysis at the HRSG cold start-upDušan Strušnik, 2021, original scientific article Abstract: The basic purpose of this paper is to present the HRSG system description in detail and possibility analysis of preventing the HRSH water-steam generated release into the atmosphere through the sky valves during the HRSG cold start-up. The steam released into the atmosphere by the cross sky valve is not an adequate solution for the following reasons: Noise prevention, water losses, thermal heat release into the environment, etc. In this paper, the possibilities and solutions are investigated in order to avoid the HRSG start-up sky venting. For this purpose, the steam quality data at HRSG cold start-up is analysed, and the possibility is examined of discharging the HRSG generated steam at the start-up via a new start-up pipeline into the existing dump condenser, or into the start-up flash tank or into the blowdown tank. The results show that, at the first 3 minutes of cold start-up, the HRSG generated only water, and this water should not be discharged into the HP or IP pipeline headers. The HRSG generates a mixture of water and steam only after 4 minutes from the start-up. For that reason it is not recommended to drain the water-steam mixture at the HRSG start-up into the new start-up pipeline, but it is recommended to drain the water and steam mixture formed during the HRSG start-up into the new start-up flash tank, or into the blowdown tank. The flash tank, and also the blowdown tank, should be appropriately dimensioned.
Keywords: boiler, duct, flue gas, heat recovery, stack, steam generator, superheater
Published in DKUM: 13.11.2023; Views: 427; Downloads: 12
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5. Energo-economics payback investment calculation modelling of gas-steam combined cycle power plantDušan Strušnik, Jurij Avsec, 2022, original scientific article Abstract: The paper deals with energo-economic payback calculation modelling of the combined gassteam cycle operation, demonstrating the basic characteristic properties of cycle behaviour in different operating regimes and calculating the payback period of the investment. The calculation of the payback period of the investment is based on the calculation of the net present value and with actual obtaining data sets from a recently built gas-steam combined cycle power plant. The results of the calculation modelling show that the gas-steam combined cycle power plant can achieve a useful efficiency of up to 88% in the back-pressure operation of the steam turbine. The useful efficiency of the gas turbine is up to 40%. The payback period of the investment depends on the investment costs, the quantity and market price of the consumed fuel, the quantity and market price of the generated electricity and thermal energy. The results show that with a price ratio fuel/electricity of 0.36, the payback period of the investment is 4 years, with a price ratio fuel/electricity of 0.54, the payback period of the investment is as much as 17 years.
Keywords: calculation, efficiency, investment, market, modelling, payback
Published in DKUM: 30.10.2023; Views: 503; Downloads: 5
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6. Off-design flow analysis of cogeneration steam turbine with real process dataDušan Strušnik, Igor Kuštrin, Jurij Avsec, 2022, original scientific article Abstract: This paper presents the concept of reconstruction of the existing coal-fired combined heat and power plant to comply with new European environmental policies. The existing coal-fired boiler will be replaced by two new dual pressure heat recovery steam generators, which will utilize the exhaust gas heat from two new gas turbines. The steam from the heat recovery steam generators will be fed to the existing steam turbine. After the reconstruction, the nominal turbine inlet steam mass-flow of 40 kg/s will be reduced to 30 kg/s. During periods of low heat demand, only one gas turbine and one heat recovery steam generator will be in operation and the live steam mass-flow may drop even to 12 kg/s. Prior to the reconstruction, dedicated tests of the existing steam turbine were carried out using the steam from the existing coal-fired boiler. The goal of the test was to verify the viability of operation with such an extremely low mass-flow. The results of tests show that such operation is possible but inefficient from a power generation point of view. Besides this, the turbine control algorithm needs to be accommodated to this extreme operating regime and additional measures like displacement of the extraction points and steam cooling will be required to control the temperature of the steam extractions. The novelty of this paper is using real prereconstruction process data for the assessment of feasibility and efficiency of the post-reconstruction operation of a combined heat and power turbine.
Keywords: cogeneration, control valves, exhaust gas, heat recovery, steam turbine
Published in DKUM: 30.10.2023; Views: 248; Downloads: 21
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7. Hydrogen production using a thermochemical cycleJurij Avsec, Urška Novosel, Dušan Strušnik, 2022, original scientific article Abstract: Sustainable methods of clean fuel production are needed throughout the world due to depleting oil reserves and the need to reduce carbon dioxide emissions. The technology based on fuel cells for electricity production or the transport sector has already been developed. However, a key missing element is a large-scale method of hydrogen production. The copper-chlorine (CuCI) combined thermochemical cycle is a promising thermochemical cycle that can produce large amounts of cheap hydrogen. A particularly promising part of this process is its use in combination with nuclear or thermal power plants. This paper focuses on a CuCl cycle and describes the models used to calculate thermodynamic and transport properties. This paper discusses the mathematical model for computing the thermodynamic properties for pure HCl and CuCl2. The mathematical model developed for the solid phase takes into account vibrations of atoms in molecules and intermolecular forces. This mathematical model can be used for the calculation of the thermodynamic properties of polyatomic crystals on the basis of the Einstein and Debye equations. The authors of this paper developed the model in the low temperature and high temperature region. All the analytical data have been compared with some experimental results and show a relatively good match. For the solid phase, the authors developed a model to calculate thermal conductivity based on electron and phonon contributions.
Keywords: thermodynamics, energy, hydrogen production, solid phase, fluid phase
Published in DKUM: 30.10.2023; Views: 375; Downloads: 8
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8. Black-out diesel engine operation modelling for the CHPP start-upDušan Strušnik, Marko Agrež, Jurij Avsec, 2022, published scientific conference contribution Abstract: Modelling power plants using real process data is crucial in determining the cost-effectiveness and flexibility of systems. The quality of the elaborated model is determined with the validation of the model, which can also give results for the operating regimes of the plant, which are not often used in practice. In this way, also the operation and responsiveness of power plants outside the range of planned operation are determined. The model simulates the operation of a diesel engine (DE) required to start a combined heat & power plant (CHPP) from a black-out or loss of the electrical power network supply. The model is made on the basis of data provided by the manufacturer and the measured DE data. The results of the model enable detailed insight into the characteristics of the DE behaviour at different operating regimes. The economic and ecological rationale ranges of operation of the DE can be determined from the characteristics of operation. The results of the model show that the DE operates with a 41.72% average efficiency, consumes from 0.114 kg/s of diesel fuel for its operation and up to 3.68 kg/s of air, the air ratio ranges from 2.2 to 2.5. DE develops shaft power up to 2170 kW.
Keywords: air-fuel equivalence ratio, black-out, diesel engine, thermal efficiency, shaft power
Published in DKUM: 27.10.2023; Views: 530; Downloads: 9
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10. Method of the best available technology and low carbon future of a combined heat and power plantDušan Strušnik, Marko Agrež, 2022, original scientific article Abstract: The low-carbon development strategy and ecological awareness of a combined heat and power (CHP) plant is the key factor that enables further development of such systems. CHP plants are subject to rigid European ecological guidelines, which dictate the pace of development of global thermal power engineering. For this purpose, the European Union issued a special Directive for the promotion of heat and power cogeneration, and is established with the best available technology (BAT) method. Even though the production of electricity using carbon-free technologies is on the rise, the production of electricity by fossil fuel combustion cannot be avoided completely. The meaning of the operation of the CHP plant is reflected particularly in the provision of tertiary services to the electric power system, regulation of the network frequency, particularly in winter months, when electricity production using carbon-free technologies is limited. In CHP systems, the low-carbon future is linked intricately to high investment costs and these impacts the final price of energy. Using the BAT method, the article presents the advantages of energy production in a combined heat and power plant, an example of the restructuring of a larger CHP system into a low-carbon plant and guidelines for further development.
Keywords: alternative facilities, best available technology, combined plant, heat recovery, hydrogen, low-carbon, methanisation, natural gas, steam recovery
Published in DKUM: 26.10.2023; Views: 331; Downloads: 8
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