| | SLO | ENG | Cookies and privacy

Bigger font | Smaller font

Search the digital library catalog Help

Query: search in
search in
search in
search in
* old and bologna study programme

Options:
  Reset


1 - 10 / 17
First pagePrevious page12Next pageLast page
1.
Carbon-free heat production for high-temperature heating systems
Sven 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: 91; Downloads: 4
.pdf Full text (3,32 MB)
This document has many files! More...

2.
Food Waste to Energy through Innovative Coupling of CHP and Heat Pump
Jan 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: 3086; Downloads: 15
.pdf Full text (19,44 MB)
This document has many files! More...

3.
Thermal analysis and application of roll bond solar absorbers for heating and cooling in residential buildings
Jurij 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: 209; Downloads: 4
.pdf Full text (1,44 MB)
This document has many files! More...

4.
Production, thermal analysis and application of roll bond solar absorbers for heating and cooling in residential buildings
Jurij 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: 223; Downloads: 14
.pdf Full text (18,06 MB)
This document has many files! More...

5.
Reversible pump-turbines - a study of pumping mode off-design conditions
Uroš Ješe, Aleš Skoták, 2020, original scientific article

Abstract: The role of pumped storage power plants (PSP) in electrical grid systems has been changing in recent years. Demands for switching from pumping to generating mode are becoming increasingly frequent. Moreover, the operating ranges of the reversible pump-turbines used in PSP systems are becoming wider in order to use the PSP as a regulator and a stabilizer of the electrical grid. The primary challenges in the development of pump-turbines are the hydraulic instabilities that occur in pumping and generating modes. The present paper focuses on partial load pumping mode instabilities, such as cavitation and rotating stall. Modern tools, such as CFD, are used for the analysis of the phenomena along with conventional experimental approaches. Rotating stall has been investigated in hydraulic laboratory experimentally and reproduced numerically using commercial CFD code. Three rotating stall cells with a rotational frequency of 2.5% of nominal pump-turbine frequency have been identified. Cavitating vortices related to rotating stall were found in the guide vanes region. Both phenomena indicate highly unstable and potentially dangerous operating conditions that need to be investigated in detail. Understanding the causes for the instabilities will lead to an improved pump-turbine design that will enable safer, more flexible and more reliable operating with fewer unwanted instabilities.
Keywords: pump-turbine, rotating stall, cavitation, Pumping mode instabilities
Published in DKUM: 01.12.2023; Views: 283; Downloads: 3
.pdf Full text (2,46 MB)
This document has many files! More...

6.
Multi-purpose use and lifecycle analysis of solar panels
Dušan 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: 274; Downloads: 3
.pdf Full text (1,36 MB)
This document has many files! More...

7.
Determination of produced and consumed electricity of a residential building using a graphical user interface
Eva 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: 191; Downloads: 8
.pdf Full text (2,75 MB)
This document has many files! More...

8.
Future trends in photovoltaics : hybrid photovoltaic/thermal system
Klemen 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: 343; Downloads: 9
.pdf Full text (14,78 MB)
This document has many files! More...

9.
Geothermal heat potential - the source for heating greenhouses in Southestern Europe
Danijela 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: 1396; Downloads: 382
.pdf Full text (1,02 MB)
This document has many files! More...

10.
Experimental investigation review of biodiesel usage in bus diesel engine
Breda Kegl, Marko Kegl, 2017, original scientific article

Abstract: This paper assembles and analyses extensive experimental research work conducted for several years in relation to biodiesel usage in a MAN bus Diesel engine with M injection system. At first the most important properties of the actually used neat rapeseed biodiesel fuel and its blends with mineral diesel are discussed and compared to that of mineral diesel. Then the injection, fuel spray, and engine characteristics for various considered fuel blends are compared at various ambient conditions, with special emphasis on the influence of low temperature on fueling. Furthermore, for each tested fuel the optimal injection pump timing is determined. The obtained optimal injection pump timings for individual fuels are then used to determine and discuss the most important injection and combustion characteristics, engine performance, as well as the emission, economy, and tribology characteristics of the engine at all modes of emission test cycles test. The results show that for each tested fuel it is possible to find the optimized injection pump timing, which enables acceptable engine characteristics at all modes of the emission test cycles test.
Keywords: bus diesel engine, fuel injection, fuel spray, combustion, emission, engine performance, tribology characteristics, optimized injection pump timing
Published in DKUM: 07.07.2017; Views: 1550; Downloads: 403
.pdf Full text (3,81 MB)
This document has many files! More...

Search done in 3.93 sec.
Back to top
Logos of partners University of Maribor University of Ljubljana University of Primorska University of Nova Gorica