1. 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, original scientific article Abstract: 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.
Keywords: heat pump, internal heat exchanger, HFO, HFC alternative, GWP
Published in DKUM: 15.05.2025; Views: 0; Downloads: 0
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2. Recent advances in ejector-enhanced vapor compression heat pump and refrigeration systems : a reviewSven Gruber, Klemen Rola, Danijela Urbancl, Darko Goričanec, 2024, original scientific article Abstract: 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.
Keywords: ejector, heat pump, refrigeration, vapor compression system, review
Published in DKUM: 03.09.2024; Views: 51; Downloads: 17
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3. Carbon-free heat production for high-temperature heating systemsSven Gruber, Klemen Rola, Danijela Urbancl, Darko Goričanec, 2023, original scientific article 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: 20
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4. Food Waste to Energy through Innovative Coupling of CHP and Heat PumpJan Drofenik, Danijela Urbancl, Darko Goričanec, Zdravko Kravanja, Zorka Novak-Pintarič, 2023, original scientific article Abstract: This paper presents the conceptual design of a technological solution for the efficient conversion of food waste into heat and power. The distribution and composition of food loss and waste at different stages of the food supply chain in Slovenia and their potential for biogas production were determined. It was found that more than 50% of food waste comes from households. Therefore, a small plant was designed to convert food waste into biogas, which was innovatively coupled with a combined heat and power (CHP) unit and a heat pump. This doubles the amount of heat generated compared to conventional cogeneration. Based on the capacity of a micro commercial CHP unit, 3330 households (about 8000 residents) would supply food waste. The heat generated could replace 5% of the natural gas used for domestic water heating. The payback period would be 7.2 years at a heat price of about 80 EUR/MWh, however, for municipalities with more than 40,000 inhabitants the payback period would be reduced to less than 3 years. The cost price of the heat generated by this system would be about 25 EUR/MWh, taking into account the government subsidy for the operation of the CHP unit.
Keywords: food waste to energy, biogas, combined heat and power, CHP, heat pump, efficiency, conceptual design, preliminary economic assessment, sensitivity analysis
Published in DKUM: 16.02.2024; Views: 3257; Downloads: 32
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5. 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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6. Production, 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, published scientific conference contribution Abstract: The effects of global warming are a crucial issue in the near future. The combination of renewable energy sources (RES) and the use of alternative energy technology such as heat pumps and hydrogen technology could solve major ecological problems. In Central Europe, the energy demand for heating and cooling in residential buildings is clearly higher than for generation of electricity or energy for trucking e.g. In this paper, a new solar thermal absorber has been analysed which is produced by using the so called "roll bond" technology (ABS Network, 2018). The focus of this study lies on the determination of the energy efficiency by combining this solar thermal absorber with heat pumps and biomass or geothermal systems in the region of Central Europe.
Keywords: roll bond solar absorbers, thermal analysis, solar
systems, heat pump systems, heating and cooling in residential
buildings
Published in DKUM: 04.12.2023; Views: 332; Downloads: 33
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7. 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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8. Determination of produced and consumed electricity of a residential building using a graphical user interfaceEva Simonič, Iztok Brinovar, Sebastijan Seme, Klemen Sredenšek, 2021, professional article Abstract: The primary objective of this paper is to present a graphical user interface for the calculation of electricity produced by a photovoltaic system and electricity consumed by a heat pump. The produced electricity is determined by a multi-year average of measurements of the global and diffuse power density of solar radiation for several places in Slovenia, while consumed electricity is determined based on the required heat for heating a residential building and domestic water. The calculation of produced and consumed electricity is validated by measurements on a real system. The developed graphical user interface enables simple user inputs of the photovoltaic system, heat pump, and the considered residential building, and provides a comprehensive technical analysis for installing both systems at the same location.
Keywords: graphical user interface, photovoltaic system, heat pump, production of electricity, consumption of electricity
Published in DKUM: 13.11.2023; Views: 278; Downloads: 19
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9. Future trends in photovoltaics : hybrid photovoltaic/thermal systemKlemen Sredenšek, Iztok Brinovar, Gregor Srpčič, Miralem Hadžiselimović, Bojan Štumberger, Amor Chowdhury, Sebastijan Seme, 2022, published scientific conference contribution abstract Keywords: hybrid photovoltaic/thermal system, photovoltaic system, heat pump, waste heat
Published in DKUM: 27.10.2023; Views: 451; Downloads: 13
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10. Geothermal heat potential - the source for heating greenhouses in Southestern EuropeDanijela Urbancl, Peter Trop, Darko Goričanec, 2016, original scientific article Abstract: The paper presents economically evaluated solutions for heating greenhouses with geothermal potential, if the same greenhouse is placed in two different locations in Southeastern Europe, one in Slovenia and the other in Serbia. The direct geothermal water exploitation using heat exchangers is presented and the remaining heat potential of already used geothermal water is exploited using high temperature heat pumps. Energy demands for heating greenhouses are calculated considering climatic parameters of both locations. Furthermore, different constructions materials are taken into account, and energy demands are evaluated if the same greenhouse is made of 4 mm toughened single glass, double insulated glass or polycarbonate plates. The results show that the geothermal energy usage is economically feasible in both locations, because payback periods are in range from two to almost eight years for different scenarios.
Keywords: geothermal heat exploitation, greenhouses energy demands, high temperature heat pump, economic analysis
Published in DKUM: 07.07.2017; Views: 1519; Downloads: 398
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