Enerji Bilimi ve Teknolojileri

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https://hdl.handle.net/20.500.12846/488

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Solar-hydrogen coupling hybrid systems for green energy
(Wiley, 2023) Coşkuner, Filiz Bilge; Balkanlı Ünlü, Esra; Civelek Yörüklü, Hülya; Elibol, Meltem Karaismailoğlu
Green hydrogen production coupled with solar energy became a universal concept to provide more efficient energy caring for the environment within the 2030 sustainable development goals target. The green energy concept provides energy systems without negative impact on the environment, economy, and society. At this point, hydrogen became a suitable energy and energy carrier for the green to green (G2G) concept, which evaluates green resources and green systems together. Producing hydrogen energy using solar radiation lowers greenhouse emissions. It allows people to participate in environmental improvements actively, makes the energy supplied cycles more sustainable, and protects the right to life of future generations. Solar energy is a primer source that can be directly adapted to provide steady power for the G2G system. Nowadays, recent trends on fuel cell, electrolyzer, and photovoltaic and photoelectrochemical technology within solar energy systems as a hybrid combination have a critical approach to realize G2G systems based on hydrogen and solar energy. This chapter focuses on G2G system, the combination of solar energy – hydrogen, fundamentals on electrolysis, photovoltaic panel, fuel cell, and electrolyzer or their hybrid combinations used for green hydrogen production from solar energy; also, thermochemical, photobiological, and photoelectrochemical production methods have been briefly introduced compared and outlined the future remarks.
Environmental issues and social issues with renewable energy
(Elsevier Science, 2022) Baykara, Zeynep Sema; Figen, Halit Eren; Elibol, Meltem Karaismailoğlu
[Özet yok]
Investigation of a novel & integrated simulation model for hydrogen production from lignocellulosic biomass
(2018) Ersöz, A.; Baykara, Zeynep Sema; Elibol, Meltem Karaismailoğlu; Güldal, N. Ö.; Figen, Halit Eren; Yüksel, F.; Turan, A. Z.; Sarıoğlan, A.; Durak Çetin, Y.
Process simulation and modeling works are very important to determine novel design and operation conditions. In this study; hydrogen production from synthesis gas obtained by gasification of lignocellulosic biomass is investigated. The main motivation of this work is to understand how biomass is converted to hydrogen rich synthesis gas and its environmentally friendly impact. Hydrogen market development in several energy production units such as fuel cells is another motivation to realize these kinds of activities. The initial results can help to contribute to the literature and widen our experience on utilization of the CO2 neutral biomass sources and gasification technology which can develop the design of hydrogen production processes. The raw syngas is obtained via staged gasification of biomass, using bubbling fluidized bed technology with secondary agents; then it is cleaned, its hydrocarbon content is reformed, CO content is shifted (WGS) and finally H2 content is separated by the PSA (Pressure Swing Adsorption) unit. According to the preliminary results of the ASPEN HYSYS conceptual process simulation model; the composition of hydrogen rich gas (0.62% H2O, 38.83% H2, 1.65% CO, 26.13% CO2, 0.08% CH4, and 32.69% N2) has been determined. The first simulation results show that the hydrogen purity of the product gas after PSA unit is 99.999% approximately. The mass lower heating value (LHVmass) of the product gas before PSA unit is expected to be about 4500 kJ/kg and the overall fuel processor efficiency has been calculated as ?93%.
title Fe sub2/sub O sub3/sub /Y sub2/sub O sub3/sub catalystsupported on alumina and halloysite/title
(2018) Elibol, Meltem Karaismailoğlu; Figen, Halit Eren; Baykara, Zeynep Sema
[Özet yok]
Photocatalytic water oxidation with a Prussian blue modified brown TiO2
(2021) Gündoğdu, Gülsüm; Ulusoy Ghobadi, T. Gamze; Sadigh Akbari, Sina; Özbay, Ekmel; Karadaş, Ferdi
A recently emerging visible light-absorbing semiconductor, brown TiO2 (b-TiO2), was coupled with a CoFe Prussian blue (PB) analogue to prepare an entirely earth-abundant semiconductor/water oxidation catalyst hybrid assembly. PB/b-TiO2 exhibits a sevenfold higher photocatalytic water oxidation activity compared to b-TiO2. An elegant band alignment unified with the optical absorption of b-TiO2 and excellent electronic dynamics of PB yield a high-performance photocatalytic system.
A genetic algorithm based multi-objective optimization of squealer tip geometry in axial flow turbines: A constant tip gap approach
(2020) Maral, Hıdır; Şenel, Cem Berk; Deveci, Kaan; Alpman, Emre; Kavurmacıoğlu, Levent Ali; Camci, Cengiz
Tip clearance is a crucial aspect of turbomachines in terms of aerodynamic and thermal performance. A gap between the blade tip surface and the stationary casing must be maintained to allow the relative motion of the blade. The leakage flow through the tip gap measurably reduces turbine performance and causes high thermal loads near the blade tip region. Several studies focused on the tip leakage flow to clarify the flow-physics in the past. The “squealer” design is one of the most common designs to reduce the adverse effects of tip leakage flow. In this paper, a genetic-algorithm-based optimization approach was applied to the conventional squealer tip design to enhance aerothermal performance. A multi-objective optimization method integrated with a meta-model was utilized to determine the optimum squealer geometry. Squealer height and width represent the design parameters which are aimed to be optimized. The objective functions for the genetic-algorithm-based optimization are the total pressure loss coefficient and Nusselt number calculated over the blade tip surface. The initial database is then enlarged iteratively using a coarse-to-fine approach to improve the prediction capability of the meta-models used. The procedure ends once the prediction errors are smaller than a prescribed level. This study indicates that squealer height and width have complex effects on the aerothermal performance, and optimization study allows to determine the optimum squealer dimensions.
Aerothermal optimizaiton of squealer geometry in axial flow turbines using genetic algorithm
(2018) Deveci, Kaan; Maral, Hıdır; Şenel, Cem Berk; Alpman, Emre; Kavurmacıoğlu, Levent Ali
In turbomachines, a tip gap is required in order to allow the relative motion of the blade and to prevent the blade tip surface from rubbing. This gap which lay out between the blade tip surface and the casing, results in fluid leakage due to the pressure difference between the pressure side and the suction side of the blade. The tip leakage flow causes almost one third of the aerodynamic loss and unsteady thermal loads over the blade tip. Previous experimental and numerical studies revealed that the squealer blade tip arrangements are one of the effective solutions in increasing the aerothermal performance of the axial flow turbines. In this paper the tip leakage flow is examined and optimized with the squealer geometry as a means to control those losses related with the tip clearance. The squealer height and width have been selected as design parameters and the corresponding computational domain was obtained parametrically. Numerical experiments with such parametrically generated multizone structured grid topologies paved the way for the aerothermal optimization of the high pressure turbine blade tip region. Flow within the linear cascade model has been numerically simulated by solving Reynolds Averaged Navier-Stokes (RANS) equations in order to produce a database. For the numerical validation a well-known test case, Durham cascade is investigated in end wall profiling studies has been used. Sixteen different squealer tip geometries have been modeled parametrically and their performance have been compared in terms of both aerodynamic loss and convective heat transfer coefficient at blade tip. Also, these two values have been introduced as objective functions in the optimization studies. A state of the art multi-objective optimization algorithm, NSGA-II, coupled with an Artificial Neural Network is used to obtain the optimized squealer blade tip geometries for reduced aerodynamic loss and minimum heat transfer coefficient. Optimization results are verified using CFD.
Demand response in grid operations
(Springer, 2023) Kocaarslan, İlhan; Ünal, Berkan Berat; Durmuşoğlu, Oğulcan; Çakmak, Adil; Özden, Alper Emre; Akay, Simay; Daim, Tuğrul
[Özet yok]
Techno-economic analysis of off-grid PV/wind/fuel cell hybrid system combinations with a comparison of regularly and seasonally occupied households
(2018) Duman, A. Can; Güler, Önder
In Turkey, it is common to move to seasonal vacation homes/second homes during summer months. Electrical energy demand of these homes, which are usually located in the coastal regions where solar radiation is high, can be met by renewable energy sources. In this study, meeting electrical energy demand of off-grid vacation homes via photovoltaic/wind/fuel cell hybrid energy systems is investigated from a techno-economical perspective. 24 different simulations were performed in the HOMER software under geographic and climatic conditions of Çeşme, İzmir that has relatively high solar and wind energy potential for Turkey conditions and is a place where seasonal vacation homes are located. Two occupancy scenarios (seasonal and regular) of the households were investigated under two storage options (hydrogen and battery) and each storage option consisted of six hybrid system configurations (three 100% renewable?+?three minimum 95% renewable). As a result, the levelized cost of electricity (COE) of off-grid renewable energy systems are found to be above the cost of grid electricity, however, a lot less when compared to previous years. The techno-economic analysis showed that, battery storage, which is a more mature technology, is still economically superior to hydrogen storage.
Techno-economic analysis of off-grid photovoltaic LED road lighting systems: A case study for northern, central and southern regions of Turkey
(2019) Duman, A. Can; Güler, Önder
Street lighting is one of the sectors where off-grid energy systems are used, and in the past decade interest in these systems has increased due to recent developments occurred both in LED and PV technology. This paper presents a techno-economic analysis of off-grid PV LED road lighting systems for northern, central and southern regions of Turkey. Road lighting calculations are conducted using DIALux software for M4 and M5 road lighting classes to obtain optimal LED luminaires, pole sizes, and spacings. Among the obtained LED powers, load profiles are created using real lighting hours of operation of the selected regions. And then, the required PV-battery systems are optimized using HOMER software. Finally, sensitivity analysis is performed for future projections considering possible increases in electricity prices and decreases in component cost of the PV systems. The results showed that the levelized COE of the off-grid PV LED road lighting systems vary between 0.229 and 0.362 $/kWh for M4, and 0.254–0.359 $/kWh for M5 road lighting class, depending on the solar potential of the region. And, the total NPC of the entire lighting installation per km vary between 24296 and 29123 $ for M5, and 33225–44318 $ for M4 road lighting class. According to the results, the systems are infeasible under current conditions in Turkey. Nonetheless, they have the added benefits of contributing to the reduction of CO2 emissions. Moreover, future projections show that the systems can be feasible if the declining trend in PV system costs continues and electricity prices increase
Techno-economic analysis of off-grid PV LED road lighting systems for Antalya province of Turkey
(2019) Duman, A. Can; Güler, Önder
In this study, a techno-economic analysis of offgrid PV LED road lighting systems is made for Antalya province of Turkey. DIALux software is used for road lighting calculations and HOMER software is used in modelling, sizing, and optimization of the energy systems. Calculations are made to determine whether maximum or minimum pole spacing options for both twin-bracket central and opposite lighting arrangements provide the optimal system design for off-grid PV LED road lighting systems under the M3 lighting class in Antalya. The techno-economic analysis of the energy system in case of dimming LED luminaires after midnight is made. Since the payback periods of the systems are found to be above the system lifetime (20 years) with and without dimming, in addition to the current case, future projections, in which electricity unit prices increase and cost of PV system component and battery costs decrease, are examined.
A comparative techno-economic assessment of manually adjustable tilt mechanisms and automatic solar trackers for behind-the-meter PV applications
(2022) Gönül, Ömer; Yazar, Fatih; Duman, A. Can; Güler, Önder
Many studies in the literature aim to increase the amount of solar radiation falling on photovoltaic (PV) panel surface to improve its performance. Most of these studies concentrate on solar tracking systems and few studies focus on manually adjustable tilt mechanisms. However, no studies in the literature compare these two methods techno-economically. Therefore, as its main contribution, this study makes a techno-economic comparison of solar trackers and manually adjustable tilt mechanisms. First, the electricity production of fixed-tilt, manually adjustable tilt mechanisms (monthly and seasonal adjustment), and automatic solar trackers (single-axis east-west (SA-EWT), single-axis south-north (SA-SNT), and dual-axis (DAT)) systems are technically analyzed for three provinces in Turkey with different solar characteristics. After that, the systems are compared economically and evaluated over levelized cost of electricity (LCoE), discounted payback period (DPBP), and internal rate of return (IRR). Finally, a detailed sensitivity analysis is made and the impact of changes in initial investment costs and real interest rates is examined. Eventually, the payback period of fixed-tilt systems is found to be 10.3–13.3 years in Turkey. Dual-axis solar trackers provide the highest electricity production increase (30.4–34.6%) compared to fixed-tilt but with the highest payback period (16.7–24 years) among all alternatives. Monthly manual tilt adjustment provides the most feasible solution by decreasing the payback period of fixed-tilt systems by around 8 months to 9.6–12.6 years and with an electricity production increase of 3.6–5%.
A comprehensive framework for electric vehicle charging station siting along highways using weighted sum method
(2024) Gönül, Ömer; Duman, A. Can; Güler, Önder
The proliferation of electric vehicles (EVs) has led to an increased demand for strategically located EV charging stations (EVCSs) to ensure a balanced and accessible charging network. The siting of EVCS involves a multifaceted process that includes technological, economic, social, geographical, and environmental factors. An EVCS network should deliver high-quality service, alleviate drivers' range anxiety, and be compatible with renewable energy system integration, while also accounting for technical infrastructure and future expansion expectations. Resting areas along highways, equipped with amenities and grid connections, emerge as potential sites for EVCS installation. Accordingly, this study presents an EVCS siting framework along highways, integrating expert opinions from diverse disciplines. The proposed method employs expert opinions to weigh site selection criteria and then uses a clustering-based approach to identify suitable locations for EVCS siting, utilizing the weighted sum method. According to the experts, the most important criterion is determined as the service level of the candidate point with a weight of 0.375, followed by traffic density (0.218), and proximity to connection roads (0.215). The method is tested both on a test highway and the Edirne-Ankara highway, which is the most heavily used in Türkiye. The results demonstrate that the test highway identifies 13 out of 18 optimal locations using the clustering strategy. Similarly, the siting method identifies 18 out of 31 optimal EVCS locations along the Edirne-Ankara highway ensuring the distance constraints. This approach is scalable and adaptable for application on highways in various countries where EVCS infrastructure is still developing.
Investigation of the physicochemical properties of Bi,Ca-doped BaZrO3 perovskites
(Mew Journal of Chemistry, 2023) Elibol, Meltem Karaismailoğlu; Akyüz, Serra Melek; Figen, Halit Eren
Perovskite oxides, primarily the ones based on BaZrO3, hold significant interest for diverse applications in a variety of disciplines, such as electrocatalysts or electrolytes in fuel cell technologies. This study outlines the synthesis of BaZrO3 perovskite powders via a sol–gel route, and explores the incorporation of bismuth and calcium cations through single doping. Extensive characterization, encompassing X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller analysis, oxygen/hydrogen temperature-programmed desorption/reduction, and scanning electron microscopy/energy-dispersive X-ray spectroscopy, reveals the impact of the metal cation incorporation on physicochemical properties, enhancing oxygen vacancies and lattice oxygen species within the BaZrO3 perovskite structure.
Survey- and simulation-based analysis of residential demand response: Appliance use behavior, electricity tariffs, home energy management systems
(Sustainable Cities and Society, 2023) Duman, A. Can; Gönül, Ömer; Erden, Hamza Salih; Güler, Önder
Residential demand response (DR) aims to stabilize the electricity grid by utilizing the flexibility of end-users. To this end, end-users are offered time-varying electricity prices and incentivized for load shifting. End-users can maximize bill reduction through automated load shifting using home energy management systems (HEMSs). Since HEMS is a new technology, the future DR potential of its mass use is unknown. Here, surveys can be very useful for gaining insight into future behaviour and preferences in using HEMS. Therefore, the objective of this study is twofold: (1) to understand appliance use behaviour, electricity tariff perception, and tendency towards HEMS-based DR participation, through a survey. And then, (2) to simulate the DR potential by entering survey responses into a HEMS optimization tool. The results show that 78% of the respondents are willing to engage in HEMS-based DR. This provides the potential to reduce the peak period consumption by 33%. However, the average bill savings achieved by HEMS owners is only 6.7%, which can hinder reaching this potential. Still, 21% of the HEMS owners save more than 10% on their bills. 8% save over 15%, and 3% over 20%. These can be the target audience of the future HEMS market and DR campaigns.
Nickel oxide decorated halloysite nanotubes as sulfur Host materials for lithium–sulfur batteries
(2023) Elibol, Meltem Karaismailoğlu; Jiang, Lihong; Xie, Dongjiu; Cao, Sijia; Pan, Xuefeng; Härk, Eneli; Lu, Yan
Lithium–sulfur batteries with high energy density still confront manychallenges, such as polysulfide dissolution, the large volume change of sulfur,and fast capacity fading in long-term cycling. Herein, a naturally abundantclay material, halloysite, is introduced as a sulfur host material in the cathodeof Li–S batteries. Nickel oxide nanoparticles are embedded into the halloysitenanotubes (NiO@Halloysite) by hydrothermal and calcination treatment toimprove the affinity of halloysite nanotubes to polysulfides. TheNiO@Halloysite composite loaded with sulfur (S/NiO@Halloysite) isemployed as the cathode of Li–S batteries, which combines the physicalconfinements of tubular halloysite particles and good chemical adsorptionability of NiO. The S/NiO@Halloysite electrode exhibits a high dischargecapacity of 1205.47 mAh g?1at 0.1 C. In addition, it demonstrates enhancedcycling stability, retaining?60% of initial capacity after 450 cycles at 0.5 C.The synthesized NiO@Halloysite can provide a promising prospect andvaluable insight into applying natural clay materials in Li–S batteries
Boundary layer stability impact on wind power
(Turkish-German University, 2020) Sirdaş, Asilhan Sevinç; Gül, Furkan Berke
Turbulence calculation is important in terms of the amount of energy the turbines will produce and the resistance of the turbines to extreme loads. Turbulence is the deviations of regular flow. Friction faced by flow and chaotic changes in velocity and pressure cause turbulence. There are many theorems and methods used for turbulence calculation. Some of these are K-theory (Eddy Diffusivity) and Power Law Expression. Calculation of turbulence is of great importance in order to improve wind forecasts. Thus, the amount of energy obtained from the wind can be calculated with higher accuracy and the regions where the wind energy farm will be established can be determined more precisely. Along with this study, wind turbulence calculation was carried out by wind data obtained from MILRES (National Wind Power Plant) turbine in Terkos, Istanbul region at different heights. In the light of these data, the distribution of energy output, wind speed, and wind direction was calculated both mathematically and by simulation. Based on the National Wind Power Plant (MILRES) turbine data, turbulence calculation was performed using Eddy Diffusivity and Power Law Expression methods. The results obtained were compared and the atmospheric stability of the region was examined using these results. During the considering period, each month was examined separately and the relationship between seasonal anomalies and turbulence was observed. Daily, monthly and seasonal deviations and changes were determined.
Synthesis of Poly (methyl methacrylate) with Borax Decahydrate Addition for Energy Applications
(Turkish-German University, 2020) Gül, Furkan Berke; Baydoğan, Nilgün
The modified polymer composites can be included as the substrate for the utilization at the photovoltaic-thermal collectors to generate solar electricity and heat in solar energy systems. Poly (methyl methacrylate) seems a suitable thermoplastic polymer due to high strength, high heat and abrasion resistance, and good mechanical properties. Chemical and physical properties of the poly (methyl methacrylate) can be improved by adding different filler materials. Borax decahydrate known as sodium tetraborate decahydrate is a soft, alkaline salt with excellent buffering and flow properties. In this study, the synthesis of polymer composite was performed by Atom Transfer Radical Polymerization for its use as a substrate at solar energy systems. Two different types of borax decahydrate (Na2B4O7.10H2O) (refined in both powder and crystal form from tincal ore) were used to increase the usage area of borax decahydrate in this study. Hence, borax decahydrate was added in poly (methyl methacrylate) as the filler material to improve surface properties with the enhancement of self-cleaning feature at composite surfaces, disposal of heavy contamination, removal of oil stains on polymer composite surface.
Investigation of the elastic properties of poly (methylmethacrylate) reinforced with graphene nanoplatelets
(Journal of Applied Polymer Science, 2021) Gül, Furkan Berke; Muhammettursun, Mahmut; Kocacinar, Elif; Erman, Ecem; Augousti, Andy; Baydoğan, Nilgün; Bel, Tayfun
The technique for synthesis of poly (methyl methacrylate) (PMMA) by atomtransfer radical polymerization has been strengthened by using graphenenanoplatelets (GNPs) to enhance the elastic properties of the polymer. In orderto improve practical, economical and mechanical performance, the requirementsfor effective implementation of production control as a smart bulk polymernanocomposite were determined for cost-effective bulk production. Three-dimensional inspection (using an ultrasound interrogation method for the wholevolume under test) confirmed the synthesis of the nanocomposite to be free ofagglomeration and bubbles. As a result of this elimination of defects, anenhancement in compressive strengthof 42.7% was achieved and the Rock-well hardness was increased by 19.9% through the addition of GNPs at 2 wt%by mass. The deformation and mechanical failure properties have been char-acterized in the mechanical enhancement of the polymer nanocomposite.Elastic parameters determined using ultrasound testing identified thatchanges in the structural features following the addition of these GNPs wereuniquely connected to the enhancements in these elastic parameters (such asYoung's modulus, Poisson's ratio, shear modulus, and microhardness) of thePMMA/GNPs nanocomposite.
Effect of the improved bulk modulus on dielectric properties of poly (methyl methacrylate)/borax hybrid composite at radar frequencies
(Materials Today Communications, 2022) Gül, Furkan Berke; Danacı, Erkan; Baydoğan, Nilgün
A cross-linkable thermoplastic has been synthesized by the Atom Transfer Radical Polymerization method for the development of PMMA/Borax composite with broadband radio-absorbing properties. The radio-physical characteristics were examined by means of measuring the changes of several features such as the transmission coefficient of electromagnetic wave, the reflection coefficient of electromagnetic wave, and permittivity. The dielectric (microwave) permittivity of this composite has been improved with the change in the borax concentration. The modified chemical composition by borax addition has provided for the synthesis of hybrid polymeric composite material with the development of insulation resistance. This modification has enhanced the functional properties of the composite with higher dielectric properties. The structural, mechanical, thermal, and electromagnetic behaviour of the composite against Ka-band radar were determined at four different borax amounts (such as in 2, 7.5, and 10 wt%). The borax additive on PMMA has provided an enhancement of mechanical performance (with respect to the results of the Shore-D and Ultrasound tests) of the composite (synthesized by the Atom Transfer Radical Polymerization method which was the effective method) for the development of the mechanical performance.

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