Faculty of Mechanical Engineering

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    ETHICAL DILEMMAS OF RENEWABLE ENERGY
    (University Ss. Cyril and Methodius in Skopje, 2022-12)
    Uler-Zefikj, Monika
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    Manev, Nikola
    The world economic growth leads to increased energy needs that have to be satisfied with higher electricity production from both conventional and renewable energy sources. Due to the reduced fossil fuel stocks as well as environmental pollution caused by conventional power plants priority is given to the expansion of renewable energy sources. Motivated by the need to study the competitiveness, eco-friendliness and reliability of renewable en-ergy, research was conducted on the effect different energy types have on the environment, population, and economy. The aim of this paper is to analyze the ethical dilemmas of renewable energy as constraints for increasing the renewable energy share in the electricity generation and replacement of fossil fuels, considering the production process intensive-ness, noble materials depletion, and climate change caused. The extensive analysis showed that although renewable energy is in principle clean and inexhaustible energy source, it can cause burdens on nature and society.
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    INTEGRATION OF LARGE‐SCALE HEAT PUMPS IN THE DISTRICT HEATING SYSTEM OF SKOPJE
    (University of Banja Luka, Faculty of Mechanical Engineering, 2021-05)
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    Monika Uler-Zefikj
    In the residential sector in EU countries space heating and domestic hot water system participate with more the 80% in the final energy consumption. Cost‐effective and energy efficient option for residential and commercial buildings is DHC which is currently dominated by fossil fuels, such as coal and gas. Upgrading existing systems with integrating renewable technologies can lead to significant benefits regarding climate change mitigation, energy security and human health. The main aim of this paper is analyzing the possibilities for integrating heat pump together with thermal storage in the district heating system in Skopje, R. North Macedonia, considering current network system, growing population, climate conditions and pollution issue. Different scenarios will be analyzed by changing the COP of the heat pump in order to get an overview of the most feasible option taking into consideration the heat production, electricity consumption and payback period. The energy model is developed and analyzed for the part operated by Balkan Energy Group. It tends to provide insight of the benefits provided by the system upgrade and cost analysis for installation, operation and maintenance of the equipment.
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    Exploring the Potential of Biomass Pyrolysis for Renewable and Sustainable Energy Production: A Comparative Study of Corn Cob, Vine Rod, and Sunflower
    (Sustainability, MDPI, 2023-09-11)
    Domazetovska Simona
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    Vladimir Strezov
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    Risto V. Filkoski
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    Tao Kan
    The paper investigates the potential of biomass pyrolysis as a sustainable and renewable energy solution. The study focuses on three biomass types: corn cob, vine rod, and sunflower, which are abundant agricultural residues with potential for biofuel production. The pyrolytic gas, oil, and char produced during pyrolysis at a heating rate of 10 C/min were analyzed. At the pyrolysis temperature of 500 C, the corn cob showed the smallest final residual mass of 24%, while the vine rod exhibited the largest mass loss of 40%. Gas analysis revealed the concentrations of CO2, CO, H2, and CH4 in the pyrolytic gas, indicating its energy potential. Sunflower presented the largest calorific value of the produced biogas, while corn cob was the lowest. The chemical composition of the bio-oils was determined, with aliphatic acids identified as the dominant compounds, suggestin their potential for biodiesel production. Fourier Transform–Infrared Spectroscopy (FT-IR) analysis of raw biomass and char products demonstrated varying extents of decomposition among the biomass samples. A multicriteria assessment approach was employed to evaluate the differences between the selected three biomass feedstock and determined that sunflower biomass ranked the highest among the three, although the overall difference was small, confirming the suitability of all three biomass samples for pyrolysis conversion to higher-value-added fuels.