Modeling and analysis of influence of spatial and temporal wind power profile on the design and exploitation of wind farms in electric power system

Predmet istraživanja doktorske disertacije je modelovanje i analiza uticaja prostornog i vremenskog profila snage vetra u projektovanju i eksploataciji vetroelektrana u elektroenergetskom sistemu (EES). Osnovni doprinosi radu su: 1. Razvijen je model za visinsku ekstrapolaciju merenih podataka o brzini vetra za procenu proizvodnje vetroelektrana. Model se bazira na metodi minimuma sume kvadrata odstupanja. Primenom ovog modela na set merenih podataka o brzini vetra sa najmanje tri visine dobija se sintetički set mernih podataka o brzini vetra na željenoj visini postavljanja vetroturbine. Estimirana baza mernih podataka se može koristiti kao ulazni set podataka za profesionalne softvere za regionalnu analizu resursa vetra, kao i procenu proizvodnje vetroelektrana. Algoritam je testiran korišćenjem realnih merenih podataka o brzini vetra sa tri lokacije koje karakterišu različiti topografski i klimatski uslovi. Sprovedene analize pokazuju da visinska ekstrapolacija merenih podataka o brzini vetra, prema predloženom modelu, daje bolje rezultate u proceni resursa energije vetra i smanjuje grešku u proceni proizvodnje vetroelektrana u odnosu na klasičnu primenu programa WAsP, koji standardno koristi podatke samo sa jedne merne visine. 2. Razvijen je model dinamičkog koeficijenta smicanja vetra. Visinski profil brzine vetra se u vetroenergetici opisuje sa dva modela i to stepenim zakonom i logaritamskim zakonom. Oba modela se praktično podjednako koriste u inženjerskoj praksi. Nedostatak oba modela je što u sebi sadrže fiksne parametre, koji ne omogućavaju dinamičko sagledavanje profila brzine vetra. Kombinujući ova dva pristupa u tezi je analitički raspregnut uticaj dominantnih faktora koji utiču na visinski profil brzine vetra. U razvijenom modelu visinski profil brzine vetra se modeluje sa koeficijentom smicanja vetra koji ima dve komponente: jednu statičku, koja je posledica hrapavosti terena, i drugu, vremenski promenljivu komponentu, koja uvažava dijabatske promene visinskog profila brzine vetra. Razvijeni model ima značajnu praktičnu 5 primenu u regionalnoj analizi potencijala energije vetra, kao i u proceni prosečne višegodišnje proizvodnje vetroelektrane na osnovu kratkoročnih merenja. Praktična primenljivost modela je testirana na realnim projektima vetroelektrana u regionu Banata i Pešterske visoravni...The research subject in this dissertation is the modeling and analysis of the effects of spatial and temporal profiles of wind power in the design and operation of wind farms in power systems. The main contributions of this work are: 1. A new mathematical model for vertical extrapolation of the measurement data for wind speed taken at several measurement heights. The model is based on the method of least squares (LES). By applying the proposed model on the sets of measured data taken at least at three measurement heights, one can obtain a synthetic set of data at a desired height where the wind power potential is analyzed. The basic idea is that during the process of estimation of the wind power potential, the measurement data are first extrapolated by the proposed method, and then by using program WAsP the spatial extrapolation is carried out. The algorithm is tested by one year wind speed measurement data taken at three locations characterized by different topographies of the terrain and different climatic conditions. The performed analyses show that preprocessing of measurement data by the proposed method results in a better estimate of the wind power potential at a height which is greater than the measurement heights compared to that obtained by the standard application of WAsP program which makes use of measurement data taken at one measurement height. 2. A new model for dynamic wind shear coefficient. In wind energy, the height profile of the wind speed is usually described by two models based on exponential and logarithmic law. Both models are almost equally used in engineering practice. The principle lack of both models is that they contain fixed parameters, which do not allow the dynamic consideration of wind speed profiles. Combining these two approaches, the analytical decoupling of the dominant factors affecting the height profile of the wind speed is provided. In the developed model, height profile of the wind speed is modelled with two parameters, one static, which is a consequence of the terrain roughness, and other time-varying parameter, which is the consequence of atmospheric stability. The developed model has important practical applications in 8 regional analysis of wind energy potential, as well as in long term wind resource assessment. The practical applicability of the model was tested on real projects of wind farms in the region of Banat and the Pester plateau..

Osetljivost sojeva Candida spp. izolovanih kod čoveka i psa sa stomatitisom na etarsko ulje timijana

Candida spp. form a part of human and animal oral cavity flora. However Candida spp. is the main cause of dental related stomatitis in humans and stomatitis in dogs. Stomatitis treatment implies the use of azoles and polyenes to which yeasts build up resistance. The research is directed to the use of natural compounds such as essential oils. The aim of this paper is to define the antifungal activity of thyme oil on 15 clinical strains of Candida spp., isolated from humans and dogs and to determine if there is a difference in susceptibility between human and dog isolates. Sampling in patients with stomatitis was done by swabbing the denture or oral mucosa swab while sampling in dogs was done by swabbing the oral cavity mucosa after stomatitis has been diagnosed. In order to investigate the antifungal activity of thyme oil in vitro, microdilution method was used. Thyme oil expressed antifungal effects on all investigated strains. Also, our data show that the values of minimum fungicide concentration (MFC) and minimum inhibitory concentration (MIC) are lower in human strains. Explanation is that in most cases, stomatitis in humans is asymptomatic and thus not treated, so Candida strains have not developed resistance. On the other hand, stomatitis in dogs is followed by a marked clinical picture and treated is by antimicotics (mostly by azoles), therefore resistant Candida strains are more likely to occur.Candida spp. je sastavni deo mikrobioma usne duplje čoveka i psa. Međutim Candida spp. predstavlja glavni uzročnik proteznog stomatitisa kod čoveka i stomatitisa kod psa. Terapija stomatitisa podrazumeva korišćenje azola i poliena na koje poslednjih godina gljivice razvijaju otpornost. Istrživanja se usmeravaju ka primeni prirodnih preparata kao što su etarska ulja. Cilj rada je utvrdi antifungalnu aktivnost ulja timijana na kliničke izolate Candida spp. čoveka i psa, i utvrdi da li postoji razlika u osetljivosti sojeva Candide spp. izolovanih kod čoveka i psa. Uzorkovanje kod pacijenata sa stomatitisom je vršeno brisom proteze ili brisom sluzokože. Kod pasa je uzrokovanje vršeno brisom sluzokože usne duplje kada je dijagnostikovan stomatitis. Zasejani sojevi su in vitro tretirani korišćenjem mikrodilucione metode da bi se utvrdilo da li ulje timijana deluje na kliničke izolate Candida spp. čoveka i psa. Rezultati pokazuju da su vrednosti minimalne fungicidne koncentracije (MFC) i minimalne inhibitorne koncentracije (MIC) manje kod čoveka. Stomatitis je kod ljudi najčešće je asimptomatski, pacijenti se ne podvrgavaju lečenju, pa sojevi Candida spp. nisu razvili rezistenciju na antifungicidne preparate. Kod pasa stomatitis je praćen burnijom kliničkom slikom, leči se antimikoticima (uglavnom azolima) pa je verovatnoća pojave rezistentnih sojeva Candida spp. veća

Long cycle life of CoMn2O4 lithium ion battery anodes with high crystallinity

CoMn2O4 nanomaterials are prepared by a low temperature precipitation route employing metal acetates and NaOH. Structural changes, induced by different annealing temperatures, are comprehensively analyzed by X-ray powder diffraction and Raman spectroscopy. With rising annealing temperature the crystal lattice of CoMn2O4 undergoes changes ; AO4 tetrahedra expand due to thermally induced substitution of Co2+ by larger Mn2+ metal ions on the A-site of the spinel structure, while in contrast, BO6 octahedra shrink since the B-site becomes partially occupied by smaller Co3+ metal ions on account of the migrated Mn ions. CoMn2O4 particle sizes are easily fine-tuned by applying different annealing temperatures ; the particle size increases with increasing annealing temperature. During the battery operation, pulverization and reduction of particle sizes occurs regardless of the initial size of the particles, but the degree of division of the particles during the operation is dependent on the initial particle properties. Thus, contrary to the common assumption that nanostructuring of the anode material improves the battery performance, samples with the largest particle sizes exhibit excellent performance with a capacity retention of 104% after 1000 cycles (compared to the 2nd cycle)

Развојни концепти вишепородичног пасивног стамбеног објекта са елементима аутоматизације

Опис: Приказано технико решење представља сублимацију модерних знања из архитектуре, машинства, електротехнике и грађевинарства, као и економије. Различити су концепти енергетски ефикасних објеката. Приказано техничко решење представља изузетно енергетски ефикасан, пасиван стамбени вишепородичан објекат, по први пут, на овај начин, повезујући значајан број области примењених наука у целину, која има свој научно-стручни, али и друштвено-економски значај.Реализатор: Машински факултет у Београду Корисник: Агенција за инвестиције и становање Града Београда Научни пројекат Министарства за науку и технолошки развој Републике Србије: ев. број 391-00-00027/2009-02/164 Подтип решења: ново техничко решење са техничко-технолошким и друштвеним иновацијама, категориј

Развојни концепти вишепородичног пасивног стамбеног објекта са елементима аутоматизације

Опис: Приказано технико решење представља сублимацију модерних знања из архитектуре, машинства, електротехнике и грађевинарства, као и економије. Различити су концепти енергетски ефикасних објеката. Приказано техничко решење представља изузетно енергетски ефикасан, пасиван стамбени вишепородичан објекат, по први пут, на овај начин, повезујући значајан број области примењених наука у целину, која има свој научно-стручни, али и друштвено-економски значај.Реализатор: Машински факултет у Београду Корисник: Агенција за инвестиције и становање Града Београда Научни пројекат Министарства за науку и технолошки развој Републике Србије: ев. број 391-00-00027/2009-02/164 Подтип решења: ново техничко решење са техничко-технолошким и друштвеним иновацијама, категориј

Analysis of the Potential for Use of Floating PV Power Plant on the Skadar Lake for Electricity Supply of Aluminium Plant in Montenegro

This paper deals with a conceptual solution for the supply of a part of electrical energy for the needs of Aluminium Plant Podgorica (KAP) in Montenegro from a large Floating Photovoltaic Power Plant (FPPP), that would be installed on the nearby lake. The recommended FPPP, with an innovative azimuth angle control method and total installed power of 90 MWp, would consist of 18 power plants having an installed power of 5 MWp each. An analysis using the NREL solar insolation database ascertained that the recommended FPPP power plant can achieve a significantly higher production in comparison with previous solutions. An economic analysis has shown that the recommended power plant would yield positive economic indicators. Additionally, such a power plant would significantly contribute to the reduction of CO2 emissions

Advanced Flexibility Support through DSO-Coordinated Participation of DER Aggregators in the Balancing Market

Future power systems with a high share of intermittent renewable energy sources (RES) in the energy portfolio will have an increasing need for active power balancing. The integration of controllable and more flexible distributed energy resources (DERs) at the distribution-grid level represents a new solution and a sustainable alternative to conventional generation units for providing balancing services to the transmission system operator (TSO). Considering that the extensive participation of DERs in ancillary services may lead to the violation of limits in the distribution network, the distribution system operator (DSO) needs to have a more active role in this process. In this paper, a framework is presented that allows the DSO, as the central coordinator of the aggregators, to participate in the balancing market (BM) as a balancing service provider (BSP). The developed mathematical model is based on the mixed-integer second-order cone programming (MISOCP) approach and allows for determination of the limits of active power flexibility at the point of the TSO–DSO connection, formation of the dependence of the price/quantity curve, and achievement of the optimal dispatch of each DER after clearing the balancing market. The simulation results are presented and verified on modified IEEE distribution networks

Analysis of the impact of connecting a larger number of small hydroelectric power plants to the short-circuit currents values and relay protection system of distribution network

In this paper the influence of a large number of small hydro power plants on the short-circuit currents is analysed, as well as the operation of the relay protection system within the real distribution network in Serbia. The necessary modification of the existing protection functions, as well as the implementation of the new proposed protection functions, are presented and discussed. Network modeling and analysis are performed using the program tool DIgSILENT PowerFactory

Hibridni solarno-električni sistemi za unapređenje energetske efikasnosti u pripremi i korišćenju sanitarne tople vode u domaćinstvima

Hot water consumption in households is an essential component in the energy consumption structure and represents a significant potential for improving the energy efficiency of this category of consumers. In this paper a hybrid solar-electric system for obtaining hot water is proposed. The basic idea is the primary use of roof-integrated solar thermal systems for the preparation of hot water used by domestic sanitary appliances. Classic electrical heaters in sanitary facilities would be a secondary system that would ensure reliability of the system in conditions of insufficient insolation.This paper presents basic elements of improvement of existing installations of sanitary devices and energy balance calculations and savings that are made in relation to standard solutions. In addition to significantly improving energy efficiency, very significant effects have been achieved in terms of increasing the speed of work processes performed by individual domestic appliances, such as washing machines and dishwashers. Hybrid solarelectric systems for improving energy efficiency in the preparation and use of domestic hot water in householdsu strukturi potrošnje energije i predstavlja značajan potencijal za unapređenje energetske efikasnosti ove kategorije potrošača. U ovom radu je predložen hibridni solarnoelektrični sistem za dobijanje tople vode. Osnovna ideja je primarno korišćenje krovno integrisanih solarno-termalnih sistema za pripremu tople vode koju koriste sanitarni uređaji u domaćinstvu. Klasični električni grejači u sanitarnim uređajima bi bili sekundarni sistem koji bi obezbeđivao pouzdanost rada sistema u uslovima nedovoljne insolacije. U ovom radu prikazani su osnovni elementi unapređenja postojećih instalacija sanitarnih uređaja i izvršeni proračuni energetskog bilansa i ušteda koje se ostvaruju u odnosu na standardna rešenja. Pored značajnog unapređenja energetske efiksanosti postignuti su i veoma značajni efekti u pogledu povećanja brzine radnih procesa koje obavljaju pojedini sanitarni uređaji u domaćinstvu, kao što su veš mašine i mašine za pranje suđa