Energetske performanse klimatizovanih objekata na bazi kratkoročne vremenske prognoze

Today, most sophisticated numerical methods for predicting building energy consumption are implemented in building energy performance simulation tools. One of the possible ways to improve balance between building energy consumption and occupant thermal comfort in existing buildings is to use simulation-assisted operation of HVAC systems. Simulation-assisted operation can be formulated as a type of operation that implements knowledge of future disturbance acting on the building and that enables operating the systems in such a way to fulfill given goals, which in nature can often be contradictory. The most important future conditions on building energy consumption are weather parameters and occupant behavior and expectations of thermal environment. In order to achieve this type of operation, optimization methods must be applied, i.e. optimal daily operation strategies must be defined for HVAC systems. Methodology to create HVAC system operation strategies on a daily basis is presented in this doctoral dissertation. Methodology is based on using building energy performance simulation software EnergyPlus, data available in short-term weather forecasts, global sensitivity analysis, and for the purpose of this research, developed software. The developed software includes particle swarm optimization method, applied over the moving horizon (planning horizon) thus enabling the use of short-term weather forecasts, with necessary calculations being performed by the chosen simulation tool. Global sensitivity analysis, also performed with the same tool, is used in order to reduce number of input variables for the optimization process. The methodology is applied to real combined-type building in Niš. Objective function of the research is to reduce building energy consumption while satisfying constraints set on thermal comfort in one part of the building. Planning horizon is set to two days, while the resulting strategies are being implemented only on the first day of this horizon. The process repeats for every new planning horizon. The results of the methodology are experimentally verified in real building. The results show that applying this methodology leads to improvement in thermal comfort in most of the premises by using more energy, compared to usual building operation, so it offers a possibility to balance between building energy consumption and thermal comfort. Use of sensitivity analysis as a first step in determining daily building operation strategies, showed that the reduced number of input variables for the optimization would lead to similar thermal comfort and building energy consumption. Since the research was performed for the real building, building energy model calibration was performed in order to make model accurately reproduce the behavior of the real building

Rare earth dual-doped multifunctional hydroxyapatite particles for potential application in preventive medicine

Composite biomaterials based on nano hydroxyapatite (HAp) are the subject of numerous studies in reconstructive medicine. Multifunctional and nanoparticulate systems based on HAp and biodegradable polymers are successfully designed as systems for controlled and systemic drug delivery suitable for use in reconstructive medicine. Thanks to the stability and flexibility of the apatite structure, Ca ions can be replaced with various elements (Zn, Sr, Mg, Co, etc.). Doping the apatite structure enables potential application of this material in preventive medicine, too. Multimodal imaging (MI) is a new and promising technique for improved diagnosis and it is patient-friendly because it saves time. MI has recently attracted much attention due to the advantageous combination of various imaging modalities, such as computer tomography (CT), photoluminescence (PL) and magnetic resonance imaging (MRI). For such a promising approach, we devised new multimodal contrast agents using the doping of a HAp matrix with rare earth (RE) ions. Pure HAp (Ca5(PO4)3(OH)), magnetic HAp:Gd (Ca4.85Gd0.15(PO4)3(OH)), down-converting HAp:Gd,Eu (Ca4.94Gd0.02Eu0.04(PO4)3(OH)) and up-converting HAp:Gd,Yb/Tm (Ca4.85 Gd0.03Yb0.1Tm0.02(PO4)3(OH)) were synthesized using a hydrothermal procedure. Morphological and structural characteristics of the particles were obtained using X-ray powder diffraction (XRPD), scanning and transmission electron microscopy (SEM/TEM), energy dispersive X-ray spectrometry (EDX), photoluminescence (PL), Fourier Transform Infrared (FTIR) and diffuse reflectance spectroscopy (DRS). The results show that needle-like nano- or microparticles were obtained in all systems. Their phase composition and uniform distribution of dopants were confirmed by the structural refinement of the XRPD data, change in the band gap, and luminescence spectra recorded using different excitation sources (λ= 370, 394 and 977 nm).Poster: [https://hdl.handle.net/21.15107/rcub_dais_4064

Rare earth dual-doped multifunctional hydroxyapatite particles for potential application in preventive medicine

Composite biomaterials based on nano hydroxyapatite (HAp) are the subject of numerous studies in reconstructive medicine. Multifunctional and nanoparticulate systems based on HAp and biodegradable polymers are successfully designed as systems for controlled and systemic drug delivery suitable for use in reconstructive medicine [1, 2]. Thanks to the stability and flexibility of the apatite structure, Ca ions can be replaced with various elements (Zn, Sr, Mg, Co, etc.) [3, 4]. Doping the apatite structure enables potential application of this material in preventive medicine, too. Multimodal imaging (MI) is a new and promising technique for improved diagnosis and it is patient-friendly because it saves time. MI has recently attracted much attention due to the advantageous combination of various imaging modalities, such as computer tomography, photoluminescence and magnetic resonance imaging.Poster presented at the Twentieth Annual Conference YUCOMAT 2018, Herceg Novi, September 3-7, 2018Abstract: [https://hdl.handle.net/21.15107/rcub_dais_3663

Hydroxyapatite nano particles doped with Gd3+, Yb3+/Tm3+ and Eu3+ as lumino-magnetic multimodal contrast agents

Hydroxyapatite (HAp) has been widely used as bone reconstruction materials due to their similarity to bone tissue. The improvement of HAp properties was achieved by doping its crystal lattice with different ions. Lanthanides, i.e. Rare Earth Elements (RE) are also suitable for doping HAp. The aim of the presented research was to investigate the possibility of creating lumino-magnetic particles of HAp doped with gadolinium (Gd3+) ions and co-doped with ytterbium/thulium (Yb3+/Tm3+) or europium (Eu3+) ions for potential use in multimodal imaging (MI). Pure HAp (Ca5(PO4)3(OH)), magnetic HAp:Gd (Ca4.85Gd0.15(PO4)3(OH)), and lumino-magnetic HAp:Gd/Yb/Tm (Ca4.85Gd0.03Yb0.1Tm0.02(PO4)3(OH)) and HAp:Gd/Eu (Ca4.94Gd0.02Eu0.04(PO4)3(OH)) particles were synthesized using emulsification process and hydrothermal processing. All synthesized particles had an elongated shape and exhibited a paramagnetic behavior. Reduction of the unit cell volume as a result of replacement of Ca2+ ions by ions with a smaller ionic radius (Gd3+, Yb3+, Tm3+, Eu3+) confirmed by using XRD and Rietveld refined plots. The energy band gap values of the synthesized samples range from 4.93 to 3.18 eV and decrease in the following order: HAp:Gd >HAp>HAp:Gd/Eu>HAp:Gd/Yb/Tm. The results of photoluminescence emission spectra of HAp:Gd/Yb/Tm and HAp:Gd/Eu particles showed characteristic transitions of Tm3+ and Eu3+, respectively

Hydroxyapatite nano particles doped with Gd3+, Yb3+/Tm3+ and Eu3+ as lumino-magnetic multimodal contrast agents

Hydroxyapatite (HAp) has been widely used as bone reconstruction materials due to their similarity to bone tissue. The improvement of HAp properties was achieved by doping its crystal lattice with different ions. Lanthanides, i.e. Rare Earth Elements (RE) are also suitable for doping HAp. The aim of the presented research was to investigate the possibility of creating lumino-magnetic particles of HAp doped with gadolinium (Gd3+) ions and co-doped with ytterbium/thulium (Yb3+/Tm3+) or europium (Eu3+) ions for potential use in multimodal imaging (MI). Pure HAp (Ca5(PO4)3(OH)), magnetic HAp:Gd (Ca4.85Gd0.15(PO4)3(OH)), and lumino-magnetic HAp:Gd/Yb/Tm (Ca4.85Gd0.03Yb0.1Tm0.02(PO4)3(OH)) and HAp:Gd/Eu (Ca4.94Gd0.02Eu0.04(PO4)3(OH)) particles were synthesized using emulsification process and hydrothermal processing. All synthesized particles had an elongated shape and exhibited a paramagnetic behavior. Reduction of the unit cell volume as a result of replacement of Ca2+ ions by ions with a smaller ionic radius (Gd3+, Yb3+, Tm3+, Eu3+) confirmed by using XRD and Rietveld refined plots. The energy band gap values of the synthesized samples range from 4.93 to 3.18 eV and decrease in the following order: HAp:Gd >HAp>HAp:Gd/Eu>HAp:Gd/Yb/Tm. The results of photoluminescence emission spectra of HAp:Gd/Yb/Tm and HAp:Gd/Eu particles showed characteristic transitions of Tm3+ and Eu3+, respectively

Rare-earth (Gd3+,Yb3+/Tm3+, Eu3+) co-doped hydroxyapatite as magnetic, up-conversion and down-conversion materials for multimodal imaging

Taking advantage of the flexibility of the apatite structure, nano- and micro-particles of hydroxyapatite (HAp) were doped with different combinations of rare earth ions (RE3+ = Gd, Eu, Yb, Tm) to achieve a synergy among their magnetic and optical properties and to enable their application in preventive medicine, particularly diagnostics based on multimodal imaging. All powders were synthesized through hydrothermal processing at T ≤ 200 °C. An X-ray powder diffraction analysis showed that all powders crystallized in P63/m space group of the hexagonal crystal structure. The refined unit-cell parameters reflected a decrease in the unit cell volume as a result of the partial substitution of Ca2+ with smaller RE3+ ions at both cation positions. The FTIR analysis additionally suggested that a synergy may exist solely in the triply doped system, where the lattice symmetry and vibration modes become more coherent than in the singly or doubly doped systems. HAp:RE3+ optical characterization revealed a change in the energy band gap and the appearance of a weak blue luminescence (λex = 370 nm) due to an increased concentration of defects. The "up"- and the "down"-conversion spectra of HAp:Gd/Yb/Tm and HAp:Gd/Eu powders showed characteristic transitions of Tm3+ and Eu3+, respectively. Furthermore, in contrast to diamagnetic HAp, all HAp:RE3+ powders exhibited paramagnetic behavior. Cell viability tests of HAp:Gd/Yb/Tm and HAp:Gd/Eu powders in human dental pulp stem cell cultures indicated their good biocompatibility

EFFECTS OF IMPLEMENTATION OF CO-GENERATION IN THE DISTRICT HEATING SYSTEM OF THE FACULTY OF MECHANICAL ENGINEERING IN NIŠ

Implementation of co-generation of thermal and electrical energy in district heating systems often results with higher overall energy efficiency of the systems, primary energy savings and environmental benefits. Financial results depend on number of parameters, some of which are very difficult to predict. After introduction of feed-in tariffs for generation of electrical energy in Serbia, better conditions for implementation of co-generation are created, although in district heating systems barriers are still present. In this paper, possibilities and effects of implementation of natural gas fired co-generation engines are examined and presented for the boiler house that is a part of the district heating system owned and operated by the Faculty of Mechanical Engineering in Niš. At the moment, in this boiler house only thermal energy is produced. The boilers are natural gas fired and often operate in low part load regimes. The plant is working only during the heating season. For estimation of effects of implementation of co-generation, referent values are taken from literature or are based on the results of measurements performed on site. Results are presented in the form of primary energy savings and greenhouse gasses emission reduction potentials. Financial aspects are also considered and triangle of costs is shown

Comparative exergetic performance analysis for certain thermal power plants in Serbia

Traditional methods of analysis and calculation of complex thermal systems are based on the first law of thermodynamics. These methods use energy balance for a system. In general, energy balances do not provide any information about internal losses. In contrast, the second law of thermodynamics introduces the concept of exergy, which is useful in the analysis of thermal systems. Exergy is a measure for assessing the quality of energy, and allows one to determine the location, cause, and real size of losses incurred as well as residues in a thermal process. The purpose of this study is to comparatively analyze the performance of four thermal power plants from the energetic and exergetic viewpoint. Thermodynamic models of the plants are developed based on the first and second law of thermodynamics. The primary objectives of this paper are to analyze the system components separately and to identify and quantify the sites having largest energy and exergy losses. Finally, by means of these analyses, the main sources of thermodynamic inefficiencies as well as a reasonable comparison of each plant to others are identified and discussed. As a result, the outcomes of this study can provide a basis for the improvement of plant performance for the considered thermal power plants

Exergy and exergoeconomic analysis of a steam boiler

Relying on coal as primary fuel in thermal power plants represents an unsustainable concept due to limited coal reserves and a negative environmental impact. Efficient utilization of coal reserves and a request for minimization of irreversibilities are imperative for thermal power plants operation. Numerous studies have shown that a steam boiler is a thermal power plant component with the highest irreversibility. The idea of this paper is to quantify the amounts and sources of irreversibilities within a steam boiler and its components, serving a 348.5MWe thermal power plant. Having this in mind, exergy and exergoeconomic analysis of a steam boiler is presented in this paper. Exergy destruction and exergy efficiency of all boiler components and of the boiler as a whole were calculated. Based on exergy flows and economic parameters (cost of the boiler, annual operation hours of the unit, maintenance factor, interest rate, operating period of the boiler), exergy analysis resulted in the cost of produced steam. The obtained results show that the boiler exergy efficiency is at 47.4%, with the largest exergy destruction occurring in the combustion chamber with a value of 288.07 MW (60.04%), and the smallest in the air heater with a value of 4.57 MW (0.95%). The cost of produced steam is calculated at 49,356.7 $/h by applying exergoeconomic analysis

Impact of orientation and building envelope characteristics on energy consumption case study of office building in city of Nis

Buildings are one of the biggest energy consumers in urban environments, so its efficient use represents a constant challenge. In public objects and households, a large part of the energy is used for heating and cooling. The orientation of the object, as well as the overall heat transfer coefficient (U-value) of transparent and non-transparent parts of the envelope, can have a significant impact on building energy needs. In this paper, analysis of the influence of different orientations, U-values of envelope elements, and size of windows on annual heating and cooling energy for an office building in city of Nis, Serbia, is presented. Model of the building was made in the Google SketchUp software, while the results of energy performance were obtained using EnergyPlus and jEplus, taking into ac-count the parameters of thermal comfort and climatic data for the area of city of Nis. Obtained results showed that, for varied parameters, the maximum difference in annual heating energy is 15129.4 kWh, i. e per m2 27.75 kWh/m2, while the maximum difference in annual cooling energy is 14356.1 kWh, i. e per m2 26.33 kWh/m2. Considering that differences in energy consumption are significant, analysis of these parameters in the early stage of design process can affect on increase of building energy efficiency. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR36037: Construction of Student hostels in Serbia at the beginning of 21st century