Primary energy savings using heat storage for biomass heating systems

District heating is an efficient way to provide heat to residential, tertiary and industrial users. The heat storage unit is an insulated water tank that absorbs surplus heat from the boiler. The stored heat in the heat storage unit makes it possible to heat even when the boiler is not working, thus increasing the heating efficiency. In order to save primary energy (fuel), the boiler operates on nominal load every time it is in operation (for the purpose of this research). The aim of this paper is to analyze the water temperature variation in the heat storage, depending on the heat load and the heat storage volume. Heat load is calculated for three reference days, with average daily temperatures from -5 to 5°C. The primary energy savings are also calculated for those days in the case of using heat storage in district heating.[Projekat Ministarstva nauke Republike Srbije, br. TR 33051: The concept of sustainable energy supply of settlements with energy efficient buildings

Coal-fired power plants energy efficiency and climate change: Current state and future trends

Termoelektrane na fosilna goriva, pre svega ugalj, emituju velike količine ugljen dioksida, koji se smatra glavnim uzročnikom fenomena globalnog zagrevanja. Smanjenje emisije CO2 u energetskom sektoru je postalo jedan od osnovnih prioriteta svih nacionalnih vlada. Sa druge strane, globalno zagrevanje direktno utiče na proizvodnju energije. Ovaj uticaj se pre svega ogleda u mogućnosti odvođenja otpadne toplote, neophodnog za rad postrojenja. U doglednoj budućnosti efikasnost rada postojećih termoenergetskih postrojenja opadati, ukoliko se ne ulože dodatni napori kako bi se unapredio njihov rad, posebno imajući u vidu optimizaciju rada kondenzacionog dela postrojenja, a ovo opet vodi povećanoj emisiji CO2. Predviđeni porast potrošnje energije dodatno podvlači ovaj problem.U radu je dat pregled današnjih metoda za smanjenje emisije CO2 u atmosferu, ali je osnovni cilj rada da ukaže na mogućnosti povećanja energetske efikasnosti postojećih postrojenja, uz relativno mala ekonomska ulaganja, čime bi se smanjili i ekološki problemi. Prikazan je uticaj porasta temperature rashladne vode i vazduha na energetsku efikasnost termoelektrana u Srbiji sa protočnim i povratnim sistemom hlađenja. Rezultati su dobijeni na osnovu originalnih matematičkih modela i numeričkih simulacija, koje su autori predstavili u drugim radovima. Dobijeni rezultati mogu biti od koristi kako pri revitalizaciji postojećih, tako i pri projektovanju novih termoenergetskih kapaciteta.Coal-fired power plants emit large amounts of CO2, which constitutes one of the largest causes of global warming. Reducing CO2 emissions in the energy sector has become a top priority for national governments. On the other hand, fossil energy production is also affected by air and water temperatures. Local weather conditions affect the capacity of cooling towers and natural water bodies to transfer waste heat from steam condensers to the atmosphere. Without technology-based improvements in cooling system efficiency, the steam-cycle energy efficiency would decrease. This again leads to increased consumption of fossil fuels and thus increasing emissions of CO2. Increasing in global energy demand aggravates this issue. In this paper, the overview of currently actual methods for CO2 reduction is given. The main objective, however, is to find a cost-effective solution for increasing the energy efficiency of existing plants in Serbia. The overview of cooling water temperature increase impact on the energy efficiency in Serbian power plants is given, based on meteorological data and numerical simulation. This study is done for both, power plants with once-through and with closed cycle cooling system. Obtained results could be used as useful guidelines in design of the new power plants and also in improving existing power plants performances

Coal-fired power plants energy efficiency and climate change: Current state and future trends

Termoelektrane na fosilna goriva, pre svega ugalj, emituju velike količine ugljen dioksida, koji se smatra glavnim uzročnikom fenomena globalnog zagrevanja. Smanjenje emisije CO2 u energetskom sektoru je postalo jedan od osnovnih prioriteta svih nacionalnih vlada. Sa druge strane, globalno zagrevanje direktno utiče na proizvodnju energije. Ovaj uticaj se pre svega ogleda u mogućnosti odvođenja otpadne toplote, neophodnog za rad postrojenja. U doglednoj budućnosti efikasnost rada postojećih termoenergetskih postrojenja opadati, ukoliko se ne ulože dodatni napori kako bi se unapredio njihov rad, posebno imajući u vidu optimizaciju rada kondenzacionog dela postrojenja, a ovo opet vodi povećanoj emisiji CO2. Predviđeni porast potrošnje energije dodatno podvlači ovaj problem.U radu je dat pregled današnjih metoda za smanjenje emisije CO2 u atmosferu, ali je osnovni cilj rada da ukaže na mogućnosti povećanja energetske efikasnosti postojećih postrojenja, uz relativno mala ekonomska ulaganja, čime bi se smanjili i ekološki problemi. Prikazan je uticaj porasta temperature rashladne vode i vazduha na energetsku efikasnost termoelektrana u Srbiji sa protočnim i povratnim sistemom hlađenja. Rezultati su dobijeni na osnovu originalnih matematičkih modela i numeričkih simulacija, koje su autori predstavili u drugim radovima. Dobijeni rezultati mogu biti od koristi kako pri revitalizaciji postojećih, tako i pri projektovanju novih termoenergetskih kapaciteta.Coal-fired power plants emit large amounts of CO2, which constitutes one of the largest causes of global warming. Reducing CO2 emissions in the energy sector has become a top priority for national governments. On the other hand, fossil energy production is also affected by air and water temperatures. Local weather conditions affect the capacity of cooling towers and natural water bodies to transfer waste heat from steam condensers to the atmosphere. Without technology-based improvements in cooling system efficiency, the steam-cycle energy efficiency would decrease. This again leads to increased consumption of fossil fuels and thus increasing emissions of CO2. Increasing in global energy demand aggravates this issue. In this paper, the overview of currently actual methods for CO2 reduction is given. The main objective, however, is to find a cost-effective solution for increasing the energy efficiency of existing plants in Serbia. The overview of cooling water temperature increase impact on the energy efficiency in Serbian power plants is given, based on meteorological data and numerical simulation. This study is done for both, power plants with once-through and with closed cycle cooling system. Obtained results could be used as useful guidelines in design of the new power plants and also in improving existing power plants performances

DETERMINATION OF CRITICAL SIZE OF CORROSION PIT ON MECHANICAL ELEMENTS IN HYDRO POWER PLANTS

Researchers in the field of fracture mechanics, predominantly developing appropriate solution algorithms for problems of solid bodies with cracks. Problems in mechanics generally, related with fracture and fatigue for solid bodies with various geometries of sharp notches, are studied to a much lesser extent. This situation can be explained by analytical difficulties arising in solving problems of elasticity theory for bodies with rounded notches. To solve problems of such class, starting from data on stress concentration in the rounded notch tip with a significant radius of curvature, simplified solutions with are therefore of great importance. Recent years, due to constant rise of computing power and development of numerical methods, re-evaluation of stress concentration factors from a viewpoint of theory of elasticity is present. This is mainly as a feedback from industry, which have requirements toward mega and nanostructures. Corrosion represents an important limitation to the safe and reliable use of many alloys in various industries. Pitting corrosion is a form of serious damage on metals surface such as high-strength aluminum alloys and stainless steel, which are susceptible to pitting when exposed to a corrosive attack in aggressive environments. This is particularly valid for dynamic loaded structures. The basic idea behind this paper is finding links between different scientific and engineering disciplines, which will enable useful level of applicability of existing knowledge. The subject of this paper is application of new method of determine length scale parameter for estimating the mechanistic aspect of corrosion pit under uniaxial/multiaxial high-cycle fatigue loadin

Karakterizacija sirodezmina izolovanih iz fitopatogene gljive Leptosphaeria maculans

The pathogenicity of phytopathogenic fungi is associated with phytotoxins, especially with their chemical nature and quantity. Sirodesmins are phytotoxins from the epipolythiodioxopiperazines group, produced by the fungus Leptosphaeria maculans, which are a cause of blackleg and stem canker in oilseed rape (Brassica napus L.). The aim of this work was to obtain a detailed chemical profile of sirodesmins in five fungal isolates (four from Vojvodina, Serbia, and one from the Centre for Agricultural Research, Rothamsted, UK). Sirodesmins showing different phytotoxicity on treated cotyledons of cv. Quinta were separated and detected by thin layer chromatography in all analysed isolates (L.m, C-3, St-5 and S-11) except K-113, which neither contained sirodesmin congeners nor did it exhibit activity. By use of high performance liquid chromatography coupled with tandem mass spectrometer, it was possible to identify total of 10 sirodesmins, together with their precursor-phomamide. It was found that the dominant epipolythiodioxopiperazines of the investigated L. maculans isolates were sirodesmin PL, sirodesmin C, and their de-acetylated derivatives.Patogenost fitopatogenih gljiva povezana je sa fitotoksinima, a naročito sa njihovom hemijskom prirodom i količinom. Sirodezmini su fitotoksini iz grupe epipolitiodioksopiperazina, koje proizvodi gljiva Leptosphaeria maculans, uzročnik suve truleži korena i raka stabla uljane repice. Cilj ovog rada bila je detaljna hemijska karakterizacija sirodezmina u pet izolata gljiva (četiri iz Vojvodine i jedan iz Velike Britanije, Centar za poljoprivredna istraživanja, Rothamsted). Kod svih ispitivanih izolata (L. maculans, C-3, St-3, S-11), osim K-113 (koji nije sadržao sirodezmine niti pokazivao aktivnost) tankoslojnom hromatografijom su razdvojeni i detektovani sirodezmini koji su pokazali različitu fitotoksičnost na tretiranim kotiledonima sorte Quinta. Primenom tečne hromatografije visoke efikasnosti, kuplovane sa tandemskim masenim spektrometrom, bilo je moguće identifikovati ukupno 10 sirodezmina, kao i njihov prekursor - fomamid. Utvrđeno je da su dominantni epipolitio-dioksopiperazini ispitivanih izolata L. maculans sirodezmin PL, sirodezmin C i njihovi deacetilovani derivati

Fifth European Dirofilaria and Angiostrongylus Days (FiEDAD) 2016

Peer reviewe

The influence of corrosion on stress concentration factor at shaft to flange radius

This paper describes the influence of corrosion on stress concentration factor and crack initiation at shaft-flange transition section. The real turbine shaft failure case study is used for research. This case study and numerical calculations show that the seal box solution led to constant leakage of river water in the zone of critical radius and resulted in corrosion fatigue cracks and turbine shaft failure. Thus, the Finite Element Analysis is performed to calculate the stress concentration factor increase as a result of corrosion occurrence. The corrosion at shaft-flange transition section is modelled in the zone with maximum stresses with a corrosion pit dimensioned to comply with real in situ dimension of pits. The presented research points new trends in stress concentration factor calculation. The obtained numerical results for maximum stress and stress concentration factor in critical zone confirmed failure analysis study outcome

Effects of operation temperature on thermal expansion and main parameters of radial ball bearings

The research of influence of operation temperature on the thermal expansion and main parameters of radial ball bearings is presented in this paper. The main bearing parameters are identified in accordance with the increasing requests concerning stability and load capacity. A series of Finite Element Analyses is performed for quasi-static analysis of all identified bearing parameters during contact period in referent temperature. Then, the dependence of bearing material characteristics on the operation temperature is discussed. Few series of Finite Element Analyses are performed for a particular radial ball bearing type, with characteristics in accordance with manufacturer specifications, for several operation temperatures. These two problems analyses include consideration of relation between the initial radial clearance, thermal expansion strains and contact deformations of the parts of the bearing assembly. The results for radial ball bearing parameters are monitored during a ball contact period for different temperatures and the appropriate discussion and conclusions are given. The conclusions about the contribution of developed procedure in defining the optimum operation temperature range are shown. [Projekat Ministarstva nauke Republike Srbije, br. TR 35029 i br. OI 174001

IMPACT OF THE COLD END OPERATING CONDITIONS ON ENERGY EFFICIENCY OF THE STEAM POWER PLANTS

The conventional steam power plant working under the Rankine Cycle and the steam condenser as a heat sink and the steam boiler as a heat source have the same importance for the power plant operating process. Energy efficiency of the coal fired power plant strongly depends on its turbine-condenser system operation mode. For the given thermal power plant configuration, cooling water temperature or/and flow rate change generate alterations in the condenser pressure. Those changes have great influence on the energy efficiency of the plant. This paper focuses on the influence of the cooling water temperature and flow rate on the condenser performance, and thus on the specific heat rate of the coal fired plant and its energy efficiency. Reference plant is working under turbine-follow mode with an open cycle cooling system. Analysis is done using thermodynamic theory, in order to define heat load dependence on the cooling water temperature and flow rate. Having these correlations, for given cooling water temperature it is possible to determine optimal flow rate of the cooling water in order to achieve an optimal condensing pressure, and thus, optimal energy efficiency of the plant. Obtained results could be used as useful guidelines in improving existing power plants performances and also in design of the new power plants

Investigation of thermostability of Mo6S3I6 nanowires using Raman spectroscopy

The thermostability (phase stability) of Mo6S3I6 nanowires was investigated by Raman spectroscopy, varying the incident laser power (1-9 mW) or by gradual heating of the sample from room temperature to 600°C. We have noticed 18 Raman modes in the room temperature Raman spectra, which is in good agreement with the factor group analysis prediction for P1 space group. We confirmed that the vibrations of Mo6S8 clusters dominate in vibrational properties of the Mo6S3I6 nanostructure, since nanowires Raman spectra are similar to Chevrel phase Raman spectra. During the temperature treatment, it was established that in the temperature range between 300 and 400°C a new Raman mode appeares. This mode can be ascribed to molybdenum oxide (MoO3). With further temperature increase, the intensity of this mode increases, drawing a conclusion that at temperature above 300°C the phase separation takes place in this system followed by a formation of oxide layer