Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Modelling and Simulation of Zinc-Air Batteries(01. Izmir Institute of Technology, 2024) Durak, Ege; Ebil, ÖzgençRenewable energy sources are key components of a sustainable future. However, most of the renewable energy sources have intermittent natures, that can significantly affect the stability of grids. Thus, Energy Storage Systems (ESS) are introduced to store the energy produced for later use. Even though there are various ESS candidates, batteries are superior candidates due to technological readiness. Batteries still suffer from disadvantages that prevent their mass adoption as ESS for grid-scale applications. As an ESS, a battery that can last long cycles, have high power densities, and material availability should be designed and commercialized. Commercial batteries such as lead-acid and Li-ion batteries still suffer from material availability, environmental friendliness, or feasibility. Therefore metal-air batteries, especially zinc-air batteries (ZAB), have significant potential due to their high-power densities, material abundance, and technological readiness. However, ZABs are not ready enough to be commercialized as grid-scale ESS due to their low cycle lives due to aging mechanisms. Therefore, more research should be conducted to improve the rechargeability of a ZAB. However, experimental procedures are time and resource-consuming. To tackle this, accurate mathematical models and simulations should be implemented. In this study, the electrochemical behavior of zinc-air batteries was simulated with Finite Element Analysis (FEM) method. The motivation of the work was to demonstrate the feasibility of a simple 1-D zinc-air battery model to investigate the effect of various phenomena on the battery capacity and charge-discharge cycles. The results were compared to literature and experimental values to evaluate the model's accuracy.Master Thesis Development of Carbon-Free Zinc-Air Batteries(01. Izmir Institute of Technology, 2024) Belet, Yunus Emre; Ebil, ÖzgençZinc-air batteries are thought to be among the greatest substitutes for present energy storage systems because of their high energy densities (~1000 Wh/kg), affordability, and safety. However, zinc-air batteries face several problems, such as carbon corrosion, pore-clogging, and electrode passivation. The main cause of these problems is carbon in the air electrode. Therefore, carbon should be eliminated from the air electrode to enhance its performance. This thesis aims to synthesize an electrocatalyst for air electrodes for secondary carbon-free zinc-air batteries within the scope of the M-Era.NET 'AMAZE' project. Initially, manganese oxide was selected as an electrocatalyst and synthesized using a co-precipitation method with different parameters such as concentration, pH, temperature, and precursor materials. The best MnxOy was obtained with a solution pH and temperature of 9.5 and 60°C, respectively. The main precursor for the catalyst was KMnO4, with a ratio of KMnO4:HCl as 20:4 by volume. α-MnO2 with a surface area of 85.68 m2g-1 was obtained. In addition, onset overpotentials for oxygen reduction and oxygen evolution reactions with 650mV and 271mV, respectively, and a maximum current density of 10.5 mA.cm-2 were obtained. Nickel and cobalt additions were evaluated to improve ORR and OER activity. Catalyst with MnxNiyCozOt(1:0.5:0.5) composition performed better than other samples and had the highest surface area (172.06 m2g-1), ORR and OER potentials of 463mV and 700mV, respectively, and current density of 96 mA.cm-2.Master Thesis Recovery of Lithium From Aqueous System Using Manganese Oxide Adsorbent With Developed Electrospun Mat Substrate(01. Izmir Institute of Technology, 2023) Akgün, Berk; Ebil, Özgenç; Demir, Mustafa MuammerLithium is used in many fields due to its high energy density and unique electrochemical properties. Recently, there has been a strong increase in demand for lithium, so the extraction of lithium from natural water resources has become a remarkable research topic. One of the most effective methods of separating lithium from natural water sources is adsorption using lithium ion-sieve adsorbents. However, the powdered nature of the adsorbents makes them challenging to process and less recyclable. Recent studies have focused on developing adsorbents using different polymeric materials as substrates or binders. In the thesis, as a new approach, flexible and free-standing polyurethane electrospun mat substrates were produced and combined with λ-MnO2 to extract lithium from aqueous systems, and their lithium removal performance was investigated. After the fabricated mats and λ-MnO2 powder were characterized, the deposition process was performed, and filtration studies were carried out in synthetic lithium solution. Optimum conditions for lithium removal were found as an adsorbent amount of 200 mg, and 200 ppm initial [Li+], and pH 12. In addition, lithium removal performances have been improved by stacking mats and multi-stage filtration processes. Lithium removal reached 76.6% when a 400 ppm lithium solution and an 8-step filtration were used. Lithium removal experiments were performed with salt-lake brine containing high concentrations of various ions and showed that these ions reduced the lithium removal. In the study, PU electrospun mats for λ-MnO2 powder were found to be a promising substrate for lithium removal from aqueous systems.Master Thesis Design and Techno-Economic Analysis of a Smart Solar Greenhouse(01. Izmir Institute of Technology, 2022) İçöz, Didem; Ebil, Özgenç; Dindaroğlu, BurakThe aim of this study is to examine the combination of agriculture and energy, which are two indispensable concepts for the existence of humanity, more efficiently. Energy, which is an indispensable part of human life, is at the top of the issues discussed in the world agenda today as it was in the past. Energy continues to be an indispensable factor in the economic and social development of countries, and therefore in increasing social welfare. With the developments in the agricultural sector, the energy need of the sector is increasing and energy diversity is important. In parallel with the world population, the demand for foodstuffs is increasing day by day. In order to meet this increasing food demand, greenhouse cultivation, where high efficiency is obtained from the unit area, is gaining more and more importance all over the world. Providing optimum conditions according to the location and seasonal characteristics of the location is essential for greenhouse efficiency. The need to heat greenhouses to provide these conditions constitutes a substantial energy cost. However, it is a known fact that fossil fuels, which are one of the energy sources, cause global climate changes, as they are an important source of CO2, known as a greenhouse gas. In this context, approaches to the use of renewable energy sources in agricultural activities are of great importance for the development of the sector. This study was prepared to examine the use and techno-economic analysis of photovoltaic panels for the energy needs of greenhouses. The solar greenhouse, where optimum conditions are provided with the automation system, will generate income from electricity sales as well as agricultural income in the months when it produces more electricity than its self-consumption.Master Thesis Grid-Connected Photovoltaic Systems for Fuel Stations: a Complete Techno-Economic Analysis(01. Izmir Institute of Technology, 2022) Kılınç, Mehmet Emin; Ebil, Özgenç; Dindaroğlu, BurakThe purpose of this study, beyond being an engineering practice, is an attempt to overcome a bottleneck that has not been overcome so far with scientific methods and to use the power of science for the benefit of the environment, the public, fuel distribution companies, petrol stations and almost every part of the society. Due to rapid changes in in terms of technology, efficiency, environmental sensitivity, consumer preferences, cost structure and legal base, this study is investigating and making suggestions for oil station companies regarding on-grid photovoltaic applications. Successful management of the process depends on effective calculation including, system requirements considering local solar radiation and financials from many aspects. Considering that, many fuel station owners cannot effectively approach the technical, bureaucratic, and financial aspects of photovoltaic applications and that academic studies that will guide the interested parties in a package form are not sufficient, the importance of this study will be more clearly demonstrated. Information obtained through the literature review, applying the engineering economics models and also with a widespread field study including petrol stations, solar material supply and installation companies, health and safety company and bank. It has been tried to set a user’s manual for concerned parties both in, academia, oil & solar sector and financial system in Turkey.Master Thesis Sintering and Densification Behavior of Gdc Infiltrated Porous Gdc Electrolyte(01. Izmir Institute of Technology, 2021) Tekin, Sinem; Akkurt, Sedat; Ebil, ÖzgençIt is desired that the electrolytes used in solid oxide fuel cells have a dense structure. Ceria-based electrolytes require temperatures of 1400-1500oC to densify. High densification temperatures make this material less in demand despite its good ionic conductivity. In this study, it was aimed to sinter and densify porous GDC scaffolds made of GDC (Gd0.10Ce0.90O1.95) material at low temperatures using infiltration technique. A porous GDC scaffold is first produced by sintering the GDC pellet around 1000oC to obtain an intermediate product ready to be infiltrated by a GDC-bearing solution. Multiple infiltration and drying cycles were intended to fill the pores by GDC nanoparticles which are expected to densify at lower temperatures. Two different groups (infiltrated and non-infiltrated) were formed and their densification behaviors with temperature and infiltration repetition cycles were investigated using a vertical dilatometer. The porous GDC scaffold was infiltrated with a polymeric solution prepared from Ce(NO3)3.6H2O and Gd(NO3)3.6H2O. The prepared samples were sintered at 1400oC. As a result of the experiments, it was observed that the densification decreased with the increase in temperature and infiltration cycles. This is thought to be because the porous scaffold could not be completely dried during the infiltration cycles. This led to the formation of a dense outer layer of GDC and porous inner layer. This dense layer inhibited shrinkage of the pellet during dilatometric analysis. Further studies need to be conducted to fully evaporate the solvent during drying of the infiltrated pellets.Master Thesis Effects of Grid Design on Lead-Acid Battery Performance(Izmir Institute of Technology, 2017) İşler, Tuğçe; Ebil, Özgenç; Top, AybenIn today’s world, approximately 88 percent of the total energy demand is supplied by fossil fuels; however, it has become clear that; other energy sources are needed due to limited fossil fuels. The demand for energy can most effectively be filled by renewable energy sources as installed energy storage capacity is growing rapidly. If renewable energy sources advance enough to fulfill the high demand, earth-friendly, clean and sustainable energy will help to protect the environment, thus ensuring a healthier life for future generations. Energy storage systems are essential in this endeavor, and in order to become more prevalent, storage systems for renewable energy sources must supply electricity without interruption as much as possible. As an electrochemical storage, a battery with a high level of performance, high energy density and life cycle could offer a viable solution for electricity storage provided that battery cost should be economically viable. This thesis aims to improve the geometry of the grid used in lead acid batteries in order to obtain a more uniform current and potential distribution, and minimize the potential drop for improved battery performance. A 3D mathematical model was developed using finite element method to evaluate the behavior of the grid under various conditions. Five different porous grid geometries were simulated under different loads and optimum grid geometry was identified. The 3D mathematical model of the lead-acid battery based on finite element method was simulated under certain conditions in order to evaluate the effect of grid geometry on battery performance.Master Thesis 3d-Printed Multiprobe Analysis System for Solar Fuel Research; Design, Fabrication and Testing(Izmir Institute of Technology, 2016) Harmanlı, İpek; Karabudak, Engin; Ebil, ÖzgençMethods of generating electricity with unlimited, clean and cheap energy from solar energy are tried to be investigated and developed in practical and theoretical academic fields. Especially, photocatalytic water splitting (PWS) systems have been identified as the main method in this study as well as in many studies due to the advantages provided by production of solar fuels from water. In this research, a study was carried out on the alternatives of the both used experimental set-up and used photocatalytic material for PWS systems. A study has been carried out on both the used experimental setup and the used photocatalytic material alternatives in PWS systems. As an alternative experimental setup that allows small volume analysis for PWS by Unisense gas microsensors, a mini photoreactor was designed using 3-D drawing and printing techniques and its usability was tested for PWS applications. Moreover, some characterization results for the electronic band structure and the band gap of the lead (II) trioxovanadate (V) chloride [PbVO3Cl] crystal, which was discovered by Eanes and co-workers in 2007 at IZTECH, was introduced in this study by not only theoretical (DFT approximations; LDA, GGA and HSE06) but also experimental (XRD, Diffuse Reflectance Method- Tauc Plot, Raman Spectroscopy, Four Probe) methods. Also, its estimated theoretical price and its potential for future application in tandem solar fuel device as a photoanode in combination with Si photocathode was calculated and discussed. The results showed that the designed mini photoreactor system is an open to development apparatus that is suitable for PWS, besides, PbVO3Cl has an "indirect transition" band structure and a band energy of ~ 2.2 eV. Although it did not give an effective result in PWS applications done by the designed mini photoreactor, it can be said that it is a semiconductor which is worth studying and developing in detail for other researches in this field due to the compatibility of its band energy amount and optical properties for PWS.Master Thesis Fabrication of Polymeric Nano-Coatings Via Chemical Vapor Deposition(Izmir Institute of Technology, 2016) Kırköse, Sema; Ebil, ÖzgençThin film coatings are used to provide protection to the substrate of interest against physical and chemical elements. Coating can also be applied to modify the surface properties of the substrate. One of the most important aspects of coating processes is controlling the thickness of coating material over the substrate. As a subset of a family of chemical vapor deposition methods, iCVD relies on vapor-to-surface reactions to form solid ultrathin polymer films. Unlike other CVD methods, iCVD is unique in that a polymerization reaction is induced by a thermally or chemically activated initiator molecule, much like in liquid-based thermal polymerization except without the use of a liquid solvent medium. The aim of the study is to fabricate polymeric protective nano-coatings via iCVD on flat surfaces at low or ambient temperatures. A variety of polymers, including homopolymers of glycidyl methacrylate (GMA), cyclo hexyl methacrylate (CHMA) and 1H, 1H, 2H, 2H,-Perfluorodecyl acrylate (PFDA) and P(GMA-PFDA) copolymers were fabricated via iCVD. The surface roughness and contact angle values were measured. Smooth hydrophobic surfaces having high contact angle (approximately 130˚) were obtained with PPFDA and PGMA-co-PPFDA thin films. Chemical compositions of the homo and co-polymer films were also evaluated confirming the retention of functional groups during polymerization, thus opening possibility of using iCVD produced films in various sensor applications.Master Thesis Development of protective nano-coatings for electro-optical systems(01. Izmir Institute of Technology, 2016) Karabıyık, Merve; Ebil, ÖzgençElectro-optical (EO) systems have wide range of applications and in recent years, especially the use of EO imaging systems in military and civil aviation applications have substantially increased. In these applications, EO systems are exposed to quite harsh and unstable operating conditions like sudden changes in temperature and humidity, dust, fog, physical shock, vibration and radiation. If their optical surfaces such as prisms, lenses and mirrors are damaged due to these conditions, their repair usually is not possible. To overcome these problems, it is necessary to develop special protective coating layers for optical surfaces. The main goal of this study is to produce protective, self-cleaning and super-hydrophobic polymeric thin films for optical surfaces of the electro-optical (EO) systems. Initiated chemical vapor deposition (iCVD) is a novel method for the fabrication of thin film coatings and it has many advantages such as low production cost, very low deposition temperature, 3D geometry coating performance and high deposition rate. Therefore, iCVD was employed to fabricate homopolymers of poly (glycidyl methacrylate) (PGMA) and poly (1H, 1H, 2H, 2H-Perfluorodecyl acrylate) (PPFDA) and P(GMA-PFDA) copolymer thin-films as protective coatings for EO systems. Optical modeling and simulations were performed to determine the effect of film thickness and refractive index on optical performance of substrates to be coated. Optical performance of fabricated coatings was also measured between 400 and 1000 nm range to confirm that protective coatings do not have any measureable impact on optical performance provided that the protective film thickness is kept between 50 nm to 1 μm. The surface morphology of the protective coatings was evaluated using a variety of analytical tools such as Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Contact Angle measurements. Optical tests were performed by following MIL-F-48616 Military Standard (MIL-STD). The best protective coatings were obtained by using P(GMA-PFDA) copolymer which yields good mechanical properties due to epoxy pendant group and super hydrophobicity due to incorporation of fluoro monomer.