Browsing by Author "Albostan, Ayhan"

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Citation Count: 13
BIOETHANOL PRODUCTION AND POTENTIAL OF TURKEY
(Gazi Univ, Fac Engineering Architecture, 2011) Melikoglu, Mehmet; Albostan, Ayhan; Energy Systems Engineering
The ever increasing demand in global energy consumption makes it inevitable for the development of new energy resources. Turkey imports nearly all of its petroleum and this causes major economical problems. In Turkey, a major cereal producer, production of energy crops will decrease the dependence of petroleum and greenhouse gas emissions. In this context, bioethanol production in Turkey becomes a major alternative to petroleum. According to the results find in this study, with the current agricultural output, none of the crops can be adequate for bioethanol production even 100% of crop harvests were utilized. However, with 4% and 7% of current wheat harvest bioethanol required for the production of E5 and E10 can be achieved. In addition, by utilizing the unused land available for agriculture and planting potato, sugar beet, and wheat (each 100%), 5.8, 8.7 and 13.7 billion litres of bioethanol can be produced and this production will be more than enough to supply Turkey's current demand for gasoline.
Citation Count: 15
Bioethanol production and potential of Turkey;
(2011) Melikoǧlu,M.; Albostan,A.; Energy Systems Engineering
The ever increasing demand in global energy consumption makes it inevitable for the development of new energy resources. Turkey imports nearly all of its petroleum and this causes major economical problems. In Turkey, a major cereal producer, production of energy crops will decrease the dependence of petroleum and greenhouse gas emissions. In this context, bioethanol production in Turkey becomes a major alternative to petroleum. According to the results find in this study, with the current agricultural output, none of the crops can be adequate for bioethanol production even 100% of crop harvests were utilized. However, with 4% and 7% of current wheat harvest bioethanol required for the production of E5 and E10 can be achieved. In addition, by utilizing the unused land available for agriculture and planting potato, sugar beet, and wheat (each 100%), 5.8, 8.7 and 13.7 billion litres of bioethanol can be produced and this production will be more than enough to supply Turkey's current demand for gasoline.
Citation Count: 78
Enhancement of PEM fuel cell performance at higher temperatures and lower humidities by high performance membrane electrode assembly based on Nafion/zeolite membrane
(Pergamon-elsevier Science Ltd, 2015) Devrim, Yilser; Albostan, Ayhan; Energy Systems Engineering
This work reports the preparation of Nafion/zeolite composite membranes with different zeolite loading. The structure of the Nafion/zeolite composite membranes are investigated by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and by thermogravimetric analysis (TGA). The introduction of zeolite particles into the Nafion matrix helps to improve the water uptake, proton conductivity and thermal stability of the nanocomposite membranes compared to the virgin Nafion membrane. The SEM analyses have proved the uniform and homogeneous distribution of zeolite in composite membranes. The composite membranes are tested in a single PEMFC with a 5 cm(2) active area operating at the temperature range of 75-120 degrees C and in humidified under 50% relative humidity (RH) and fully humidified conditions. Single PEMFC tests show that Nafion/zeolite composite membrane is more stable and also performed better than virgin Nafion membrane at low humidity condition. The results indicate the Nafion/zeolite composite membranes could be utilized as the proton exchange membranes for PEMFC. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Citation Count: 80
Experimental investigation of CO tolerance in high temperature PEM fuel cells
(Pergamon-elsevier Science Ltd, 2018) Devrim, Yilser; Albostan, Ayhan; Devrim, Huseyin; Energy Systems Engineering
In the present work, the effect of operating a high temperature proton exchange membrane fuel cell (HT-PEMFC) with different reactant gases has been investigated throughout performance tests. Also, the effects of temperature on the performance of a HT-PEMFC were analyzed at varying temperatures, ranging from 140 degrees C to 200 degrees C. Increasing the operating temperature of the cell increases the performance of the HT-PEMFC. The optimum operating temperature was determined to be 160 degrees C due to the deformations occurring in the cell components at high working temperatures. To investigate the effects of CO on the performance of HT-PEMFC, the CO concentration ranged from 1 to 5 vol %. The current density at 0.6 V decreases from 0.33 A/cm(2) for H-2 to 0.31 A/cm(2) for H-2 containing 1 vol % CO, to 0.29 A/cm(2) for 3 vol % CO, and 0.25 A/cm(2) for 5 vol % CO, respectively. The experimental results show that the presence of 25 vol % CO2 or N-2 has only a dilution effect and therefore, there is a minor impact on the HT-PEMFC performance. However, the addition of CO to H-2/N-2 or H-2/CO2 mixtures increased the performance loss. After longterm performance test for 500 h, the observed voltage drop at constant current density was obtained as similar to 14.8% for H-2/CO2/CO (75/22/3) mixture. The overall results suggest that the anode side gas mixture with up to 5 vol % CO can be supplied to the HT-PEMFC stack directly from the reformer. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Citation Count: 65
Graphene based catalyst supports for high temperature PEM fuel cell application
(Pergamon-elsevier Science Ltd, 2018) Devrim, Yilser; Arica, Elif Damla; Albostan, Ayhan; Energy Systems Engineering
In this study, the effect of graphene nanoplatelet (GNP) and graphene oxide (GO) based carbon supports on polybenzimidazole (PBI) based high temperature proton exchange membrane fuel cells (HT-PEMFCs) performances were investigated. Pt/GNP and Pt/GO catalysts were synthesized by microwave assisted chemical reduction support. X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Brauner, Emmet and Teller (BET) analysis and high resolution transmission electron microscopy (HRTEM) were used to investigate the microstructure and morphology of the as-prepared catalysts. The electrochemical surface area (ESA) was studied by cyclic voltammetry (CV). The results showed deposition of smaller Pt nanoparticles with uniform distribution and higher ECSA for Pt/GNP compared to Pt/GO. The Pt/GNP and Pt/GO catalysts were tested in 25 cm(2) active area single HT-PEMFC with H-2/air at 160 degrees C without humidification. Performance evaluation in HT-PEMFC shows current densities of 0.28, 0.17 and 0.22 A/cm(2) for the Pt/GNP, Pt/C and Pt/GO catalysts based MEAs at 160 degrees C, respectively. The maximum power density was obtained for MEA prepared by Pt/GNP catalyst with H-2/Air dry reactant gases as 0.34, 0.40 and 0.46 W/cm(2) at 160 degrees C, 175 degrees C and 190 degrees C, respectively. Graphene based catalyst supports exhibits an enhanced HT-PEMFC performance in both low and high current density regions. The results indicate the graphene catalyst support could be utilized as the catalyst support for HT-PEMFC application. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Citation Count: 40
Graphene-Supported Platinum Catalyst-Based Membrane Electrode Assembly for PEM Fuel Cell
(Springer, 2016) Devrim, Yilser; Albostan, Ayhan; Energy Systems Engineering
The aim of this study is the preparation and characterization of a graphene-supported platinum (Pt) catalyst for proton exchange membrane fuel cell (PEMFC) applications. The graphene-supported Pt catalysts were prepared by chemical reduction of graphene and chloroplatinic acid (H2PtCl6) in ethylene glycol. X-ray powder diffraction, thermogravimetric analysis (TGA) and scanning electron microscopy have been used to analyze structure and surface morphology of the graphene-supported catalyst. The TGA results showed that the Pt loading of the graphene-supported catalyst was 31%. The proof of the Pt particles on the support surfaces was also verified by energy-dispersive x-ray spectroscopy analysis. The commercial carbon-supported catalyst and prepared Pt/graphene catalysts were used as both anode and cathode electrodes for PEMFC at ambient pressure and 70 degrees C. The maximum power density was obtained for the Pt/graphene-based membrane electrode assembly (MEA) with H-2/O-2 reactant gases as 0.925 W cm(2). The maximum current density of the Pt/graphene-based MEA can reach 1.267 and 0.43 A/cm(2) at 0.6 V with H-2/O-2 and H-2/air, respectively. The MEA prepared by the Pt/graphene catalyst shows good stability in long-term PEMFC durability tests. The PEMFC cell voltage was maintained at 0.6 V without apparent voltage drop when operated at 0.43 A/cm(2) constant current density and 70 degrees C for 400 h. As a result, PEMFC performance was found to be superlative for the graphene-supported Pt catalyst compared with the Pt/C commercial catalyst. The results indicate the graphene-supported Pt catalyst could be utilized as the electrocatalyst for PEMFC applications.
Citation Count: 85
An investigation on wind energy potential and small scale wind turbine performance at Incek region - Ankara, Turkey
(Pergamon-elsevier Science Ltd, 2015) Bilir, Levent; Imir, Mehmet; Devrim, Yilser; Albostan, Ayhan; Energy Systems Engineering
Renewable energy resources increased their importance in the last decades due to environmental pollution problems. Additionally, the fact that fossil fuels such as oil, coal, and natural gas will be depleted in near future encourages researchers to make investigations on alternative energy resources. Wind energy, which is one of the most used alternative resources, has a great potential. In this study, Weibull parameters at Incek region of Ankara (the capital city of Turkey), where /intim University campus is located, were determined for four different seasons and for twelve months in order to accomplish wind speed characterization at the region. Wind speed data at 20 m and 30 m heights were collected from. a measurement station installed at Atilim University campus area. The data were taken as 1 min average values for a one year period between June 2012 and June 2013. Hourly average wind speed values for each height were derived using the collected wind data. Weibull parameters were calculated with five different methods using the derived hourly average wind speed values. According to root mean square error analyses, the best methods for which Weibull distribution fits the actual wind data were determined as power density and empirical methods. The power and energy density values for the region were also calculated for each season and each month. It was revealed that the maximum power density is encountered in March with about 98 (W/m(2)). Since this power density indicates that large scale wind turbine use is not a good option at the region, the performances of three different small scale wind turbines were evaluated. According to the results, two of the investigated wind turbines were found to be capable to generate all yearly energy need of an average household in Turkey. (C) 2015 Elsevier Ltd. All rights reserved.
Citation Count: 67
Modeling and simulation of a hybrid photovoltaic (PV) module-electrolyzer-PEM fuel cell system for micro-cogeneration applications
(Pergamon-elsevier Science Ltd, 2015) Ozgirgin, Ekin; Devrim, Yilser; Albostan, Ayhan; Energy Systems Engineering
The rising cost of energy and power, depreciation of natural resources like fossil fuels and the global warming issues have all led the need for developing advanced clean energy systems. Hydrogen, which is clean energy carrier, can be produced by using solar electric energy from photovoltaic (PV) modules for the water electrolysis without emitting carbon dioxide. Modeling of PV module-electrolyzer hydrogen system is important for their planning and control strategies in many applications. In this respect, high-efficiency cogeneration systems for producing both heat and electricity coupled with clean energy sources such as PVs and fuel cells are gaining more attention, due to their advantages in terms of increasing efficiency and power quality, reducing harmful emissions and flexibility of operation. This study describes the analysis of the PV module-fuel cell hybrid system for house-hold micro co-generation applications. The system consists of PV modules, batteries, proton exchange membrane type water electrolyzer and proton exchange membrane fuel cell (PEMFC). The excess heat of PEMFC was used to supply hot water and/or heating energy of the house. Electrical energy was stored in the batteries. The analysis of the PV-electrolyzer-PEMFC system can be further used for designing co-generation systems for various application optimizing the PV module, electrolyzer and PEMFC sizes. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Citation Count: 67
Modelling and simulation of a hybrid solar heating system for greenhouse applications using Matlab/Simulink
(Pergamon-elsevier Science Ltd, 2013) Kiyan, Metin; Bingol, Ekin; Melikoglu, Mehmet; Albostan, Ayhan; Energy Systems Engineering; Department of Mechanical Engineering
Solar energy is a major renewable energy source and hybrid solar systems are gaining increased academic and industrial attention due to the unique advantages they offer. In this paper, a mathematical model has been developed to investigate the thermal behavior of a greenhouse heated by a hybrid solar collector system. This hybrid system contains an evacuated tube solar heat collector unit, an auxiliary fossil fuel heating unit, a hot water storage unit, control and piping units. A Matlab/Simulink based model and software has been developed to predict the storage water temperature, greenhouse indoor temperature and the amount of auxiliary fuel, as a function of various design parameters of the greenhouse such as location, dimensions, and meteorological data of the region. As a case study, a greenhouse located in Sanhurfa/Turkey has been simulated based on recent meteorological data and aforementioned hybrid system. The results of simulations performed on an annual basis indicate that revising the existing fossil fuel system with the proposed hybrid system, is economically feasible for most cases, however it requires a slightly longer payback period than expected. On the other hand, by reducing the greenhouse gas emissions significantly, it has a considerable positive environmental impact. The developed dynamic simulation method can be further used for designing heating systems for various solar greenhouses and optimizing the solar collector and thermal storage sizes. (C) 2013 Elsevier Ltd. All rights reserved.
Citation Count: 61
Seasonal and yearly wind speed distribution and wind power density analysis based on Weibull distribution function
(Pergamon-elsevier Science Ltd, 2015) Bilir, Levent; Imir, Mehmet; Devrim, Yilser; Albostan, Ayhan; Energy Systems Engineering
Wind energy, which is among the most promising renewable energy resources, is used throughout the world as an alternative to fossil fuels. In the assessment of wind energy for a region, the use of two-parameter Weibull distribution is an important tool. In this study, wind speed data, collected for a one year period between June 2012 and June 2013, were evaluated. Wind speed data, collected for two different heights (20 m and 30 m) from a measurement station installed in Atihm University campus area (Ankara, Turkey), were recorded using a data logger as one minute average values. Yearly average hourly wind speed values for 20 m and 30 m heights were determined as 2.9859 m/s and 3.3216 m/s, respectively. Yearly and seasonal shape (k) and scale (c) parameter of Weibull distribution for wind speed were calculated for each height using five different methods. Additionally, since the hub height of many wind turbines is higher than these measurement heights, Weibull parameters were also calculated for 50 m height. Root mean square error values of Weibull distribution functions for each height, derived using five different methods, show that a satisfactory representation of wind data is achieved for all methods. Yearly and seasonal wind power density values of the region were calculated using the best Weibull parameters for each case. As a conclusion, the highest wind power density value was found to be in winter season while the lowest value was encountered in autumn season. Yearly wind power densities were calculated as 39.955 (W/m(2)), 51.282 (W/m(2)) and 72.615 (W/m(2)) for 20 m, 30 m and 50 m height, respectively. The prevailing wind direction was also determined as southeast for the region. It can be concluded that the wind power density value at the region is considerable and can be exploited using small scale wind turbines. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
YARININ ENERJİSİ-HİDROJEN
(2013) Devrim, Yılser; Albostan, Ayhan; Energy Systems Engineering
Günümüzde hızla ilerleyen teknolojik gelişme enerji kullanımını körüklemiş ve enerji olmaksızın yaşamak olanaksız bir hal almıştır. Özellikle ulaşım ve taşımacılıkta kullanılan benzin ve mazotun hammaddesi olan ham petrolun tükenmeye başladığı yaygın olarak kabul görmüştür. Dünyamızın her yıl artan % 4-5 oranındaki enerji ihtiyacına karşılık, bu ihtiyacı karşılayan fosil-yakıt rezervleri çok daha hızlı bir şekilde azalmaktadır. En iyimser tahminler bile, en geç 2030-2050 yılları arasında petrol rezervlerinin büyük ölçüde tükeneceğini ve ihtiyacı karşılayamayacağını göstermektedir. Kömür ve doğal gaz için de benzer bir durum söz konusudur. Ayrıca fosil yakıtların kullanımı dünya ortalama sıcaklığını son bin yılın en yüksek değerlerine ulaştırmıştır. Bu durum ise, yoğun hava kirliliğinin yanı sıra milyonlarca liralık zarara yol açan sel, fırtına gibi doğal felaketlerin gözle görülür şekilde artmasına neden olmaktadır. Ayrıca, ham petrol ve doğalgaz fiyatlarının son yıllardaki hızlı artışı ülkelerin ve tüketicilerin bu alandaki harcamalarını önemli ölçüde artırmıştır.