Person: ÇİFTÇİOĞLU, GÖKÇEN ALEV
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ÇİFTÇİOĞLU
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GÖKÇEN ALEV
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Publication Metadata only Life cycle assessment of power generation alternatives for a stand-alone mobile house(PERGAMON-ELSEVIER SCIENCE LTD, 2013) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Sevencan, Suat; Ciftcioglu, Gokcen A.This paper presents comparative life cycle assessment of nine different hybrid power generation solutions that meet the energy demand of a prototypical mobile home. In these nine solutions, photovoltaic panels and a wind turbine are used as the main energy source. Fuel cell and diesel generator are utilized as backup systems. Batteries, compressed H-2, and H-2 in metal hydrides are employed as backup energy storage. The findings of the study shows that renewable energy sources, although they are carbon-free, are not as environmentally friendly as may generally be thought. The comparative findings of this study indicate that a hybrid system with a wind turbine as a main power source and a diesel engine as backup power system is the most environmentally sound solution among the alternatives. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Publication Metadata only Environmental analysis of different packaging waste collection systems for Istanbul - Turkey case study(ELSEVIER, 2016) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Yildiz-Geyhan, Eren; Yilcan-Ciftci, Gulsah; Altun-Ciftcioglu, Gokcen Alev; Kadirgan, Mehmet Arif NesetSource-separated collection of recyclable packaging wastes has been a huge issue for cities such as Istanbul considering their socially, economically, culturally and environmentally cosmopolite structure. In order to apply an environmentally effective separation and collection, system has to be analyzed with a holistic approach including whole recycled packaging material amounts, source consumptions and related emissions. In this context, the aim of this study is to determine the environmentally optimum source-separated packaging waste collection system applicable in Istanbul, Turkey for the first time in literature. Eight scenarios for separated collection system were defined and all of them were compared with each other and with the existing system. To measure the efficiency of the system, some efficiency indicators were chosen and effectiveness related variables were determined to predict the participation rate. Calculations of the efficiency indicators for alternative scenarios were based on the existing system. The environmental analysis was conducted by using Life Cycle Assessment methodology. The results of this study showed that existing system was still one of the environmentally most promising scenarios. Following advantageous scenarios were Scenarios 5 and 6 which were two and three fractionated curbside collection systems, respectively. It is also seen that more fractionated scenarios were less beneficial than two fractionated scenarios. And finally, it can be concluded that with an increment on participation rate and changing collection material type, collection efficiency of curbside system would increase and be environmentally more beneficial. (C) 2015 Elsevier B.V. All rights reserved.Publication Metadata only Stochastic Modeling and Simulation of Photopolymerization Process(WILEY-BLACKWELL, 2011) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Altun-Ciftcioglu, Gokcen A.; Ersoy-Mericboyu, Aysegul; Henderson, Clifford L.In this study, the effect of photoinitiator concentration on the gelation time of different resins were studied in the absence of oxygen in the reaction volume by using passive microrheology technique. Four different monomers which are ethoxylated pentaerythritol tetraacrylate (SR494), trimethylolpropane triacrylate (SR351), Methylene glycol diacrylate (SR272), and 2(2-ethoxyetoxy) ethyl acrylate (SR256) were used in these experiments. Resins were prepared from these four different monomers by mixing them with various amount of 2,2-dimethoxy 1,2-diphenylethanone photoinitiator molecule with high absorption coefficient at the frequency of UV light used in these experiment. The simulations of the results obtained from microrheology experiments were carried out with the new model based on the stochastic Monte Carlo approach in order to account for the inherently random and discrete nature of the photopolymerization reactions. The model captures the nonlinear decrease of gelation time with increasing photoinitator concentration and number of acrylate fragments on each monomer. POLYM. ENG. SCI., 51:1710-1719, 2011. (C) 2011 Society of Plastics EngineersPublication Metadata only Focal point analysis of torsional isomers of acrylic acid(TAYLOR & FRANCIS LTD, 2010) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Ciftcioglu, Gokcen Alev; Trindle, Carl; Yavuz, IlhanThe thermochemistry of acrylic acid has presented challenges owing to its high reactivity, tendency to dimerize in the gas phase, and the existence of two very nearly equal energy conformational isomers. Well-tested thermochemical schemes including G2, G3, G4, and CBS-QB3 agree in the prediction that the s-cis syn structure is the most stable of the torsional isomers, with the s-cis anti form lying 3 kJ mol-1 or less higher in energy. Microwave spectra suggest a value of 0.63 kJ mol-1. The energy barrier between these forms is in the neighbourhood of 25 kJ mol-1 according to a MP2/cc-pVDZ calculation. We present estimates of the relative energies of all four torsional isomers and the rotational barrier based on a variant of the Focal Point Analysis developed by Csaszar and co-workers. These calculations, extending to the CCSD(T)/cc-pV5Z level, predict that the s-cis anti torsional isomer is the most stable form, in contrast to prior estimates. The s-cis syn form lies about 2.9 kJ mol-1 higher, while the s-trans syn and anti forms lie at about 21.7 and 23.3 kJ mol-1, respectively. We estimate the rotational barrier between the s-cis trans and s-cis anti structures to be about 23.9 kJ mol-1. Error ranges derived from the fit to extrapolation forms suggest that our estimates have an uncertainty of about 0.1 kJ mol-1.Publication Metadata only Simulation of Models for Multifunctional Photopolymerization Kinetics(WILEY-BLACKWELL, 2014) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Altun-Ciftcioglu, Gokcen A.; Ersoy-Mericboyu, Aysegul; Henderson, Clifford L.In this study, two different models of photopolymerization of multifunctional monomers are developed. The first is a kinetic model and is based on first order nonlinear ordinary differential equations describing the rates of photoinitiator, monomer, and live and dead radicals of different chain lengths. In the second model, a stochastic Monte Carlo approach is used to predict the time evolution of the photopolymerization process. In this model the chain affects are incorporated both in the propagation and termination rate constants. The simulations of these models for the predictions of gelation times are compared with the experimental values measured in the absence of oxygen in the reaction volume by using passive microrheology technique. The nonlinear decrease of gelation time with increasing photoinitator concentration and number of acrylate fragments on each monomer is best captured with the second model. Furthermore, the second model is successfully verified with kinetic data generated from FTIR and DSC experiments. (C) 2013 Society of Plastics EngineersPublication Open Access Comparison of Conventional and Modified Burners in Performance with Different Fuels using a Linear and a Non-linear Eddy-viscosity Turbulence Model(ISFAHAN UNIV TECHNOLOGY, 2019-11-01) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Yangaz, M. U.; Ciftcioglu, G. A.; Kadirgan, M. A. N.Energy sources must be used efficiently to provide the sufficient amount of energy for the still-growing population in the world, already threatened by the effects of global warming. The significant increase in the use of natural resources causes serious problems due to its unsustainable situation. Therefore, exhaust gases/emissions must be reduced to prevent more damage on the environment. This study aims to provide solutions for a sustainable ecosystem by lowering emissions such as CO, unburnt HC, NOx, and enhancing the combustion efficiency in a certain type/scale industrial burner. In that way, some geometric modifications (on furnace design and the connected burner) have been applied on the conventional type burners to benefit the effects of preheating of combustion air. Modified geometries have been analyzed numerically and compared with the conventional design's results. Moreover, the comparison between a linear and non-linear turbulence model has been given in terms of simulation results. Major findings indicate that Burner-1 has significantly lower emissions compared to the others. Preheating effect coupled with the flue gas recirculation (FGR) seems to work well in terms of performance and emissions. Also, a significant difference between linear and non-linear turbulence model appeared on the emission characteristics for the same simulations.Publication Open Access Kimya Endüstrilerinde Patlama ve Yangınların Önlenmesi ve İlgili Vaka Çalışması(2019-03-31) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Ufuk MEVLEVİOĞLU;M.A. Neşet KADIRGAN;GÖKÇEN ALEV ÇİFTÇİOĞLUBu çalışmada, iş yerlerinde karşılaşılabilen patlama ve yangın risklerini değerlendirmek ve bu risklere karşı alınabilecek önlemleri belirlemek için Türkiye’nin ulusal mevzuatı ve TSE standartlarında belirtilen yöntemler incelenmekte ve hayali bir kimya tesisine uygulanmaktadır. Hayali tesisteki solvent tankı ve solvent pompası için yapılan değerlendirmede, tank içerisinin “Bölge 0” patlayıcı ortam olarak sınıflandırılabileceği, pompa etrafında ise çeşitli mühendislik yaklaşımlarıyla farklı patlayıcı ortam değerlendirmeleri yapılabileceği sonuçlarına varılmıştır. Ayrıca hayali tesisteki polimer toz besleme hunisi için yapılan değerlendirmede, huni içerisinin “Bölge 20” patlayıcı ortam olarak sınıflandırılabileceği, huni etrafında oluşabilecek patlayıcı ortamın tehlike mesafesinin ise, ilgili standartta verilen nitel yöntemlere dayanarak tahmini olarak yapılabileceği gösterilmiştir. Sınıflandırılmış olan bu tehlikeli bölgelerin dahilinde kullanılabilecek cihazların kategorileri ve diğer özellikleri belirlenmiş, bu bölgelerde patlama ve yangınlara karşı alınabilecek önlemlere çeşitli örnekler verilmiştir. Sonuç olarak kimya endüstrisinde sıkça rastlanabilecek tanklar, pompalar, solventler vb. etkenlerle ilgili deneysel veriler üretilmesine ve yanıcı tozlarla ilgili standart testleri yapabilecek akredite laboratuvarlara ihtiyaç duyulduğu vurgulanmıştır.Publication Metadata only Social life cycle assessment of different packaging waste collection system(ELSEVIER SCIENCE BV, 2017) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Yildiz-Geyhan, Eren; Altun-Ciftcioglu, Gokcen Alev; Kadirgan, Mehmet Arif NesetRecycling is one of the most preferable tools of the sustainability concept considering its economic benefits and environmental effects. However, environmental and economic benefits are not always enough to accomplish a sustainable life concept. Social impacts, which basically focus on issues such as the well-being of humans, should be also considered. Regarding this concept; in this study we aimed to analyze the social impacts of different packaging waste management systems. In this context, we proposed eleven scenarios, which consisted of hypothetical formal and informal collection scenarios. All these scenarios were compared with the currently applied collection system in Istanbul, Turkey. The social analysis was conducted by using Life Cycle Assessment methodology. The results of this study showed that existing system and informal collection scenarios had socially fewer score than the formal scenarios in almost all impacts. Between the formal collection systems, there were slight differences caused by especially working conditions and socio-economic repercussion. However, formal collection scenarios showed more negative social impacts than formal-informal system integration. The result of this study showed that it was crucial to consider an amelioration on the informal collection system. In the integrated scenario (S11), some of the critical subcategories were idealized and improved taking into consideration to the long term modification issues. Although we couldn't minimize all negative social impacts; it was obvious that this scenario was still the best option. Finally, we may conclude that application of an ameliorated informal collection system would be socially more beneficial than formal and informal collection systems.Publication Metadata only Life cycle assessment (LCA) of a solar selective surface produced by continuous process and solar flat collectors(PERGAMON-ELSEVIER SCIENCE LTD, 2016) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Altun-Ciftcioglu, G. A.; Gokulu, O.; Kadirgan, F.; Kadirgan, M. A. N.Roll to roll (R2R) continuous production of solar selective surface, is a cost benefit method from the energy dispenses and investment point of view, therefore it is an innovative production way. Before innovative energy systems are introduced into the market, a thorough investigation of ecological aspect is necessary. Therefore, the purpose of this study is not only to perform a life cycle assessment (LCA) and demonstrate the advantage of the life cycle thinking selective surface production process, but also as to show the effect of this production method on the manufacturing process of solar flat collectors. LCA calculations for the continuous selective surface production process and a complete solar collector were performed with using the Ecoinvent database and the build in methods in SimaPro7.3: (1) Cumulative Energy Demand (CED); (2) Greenhouse Gas Protocol (GHG); (3) the Eco-indicator 99. To reflect the total quantity of primary energy needed to produce, use, and recycle/dispose of the produced selective surface including transportation, CED was used. CED reflects the energy demand over its entire lifecycle, and makes it possible to determine which phase consumes the most energy. In order to quantify the greenhouse gas amount, the GHG was chosen since it is the most widely used and trusted international accounting tool. At last, the environmental impact of the system in study was calculated using Eco-indicator 99 method. The CED analysis estimated a yearly demand of 7.91 TJ for 200,000 square meter net selective surface production. Further calculations also showed that the energy payback time for the innovative production is as short as 3-4 days. Cu sheet production showed the highest impact and resulted in having the highest energy demand. The coating process only requires 32% of the primary energy demand. It was found that the energy demand of the plant and the building were as low as 2%, whereas it had 20% of GHG emissions. Further the total CO2 equivalent was shown to be 0.3245 kg/m(2). At last, the LCA for a complete solar collector having 4 m(2) of solar surface produced by conventional batch system and continuous roll to roll selective surface system was compared. The results also showed that using the roll to roll production technology caused reductions on the environmental burden. The results of LCA for the production of a continuous selective surface and comparison of solar flat collectors using two different selective surface production technology were presented. The energy payback time for the roll to roll selective surface production was found to be 3-4 days. The continuous process technology was shown to have a lower impact than the conventional batch selective surface production. (C) 2016 Elsevier Ltd. All rights reserved.Publication Metadata only Environmental and social life cycle sustainability assessment of different packaging waste collection systems(ELSEVIER, 2019) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Yildiz-Geyhan, Eren; Yilan, Gulsah; Altun-Ciftcioglu, Gokcen Alev; Kadirgan, Mehmet Arif NesetConsidering the social, cultural, economic and environmental structure, source-separated collection of recyclable packaging wastes has been a huge issue for cosmopolite cities like Istanbul. To provide an effective recycling system; all source separation, collection and recycling activities should be analyzed environmentally and socially. In the scope of this study, existing and alternative municipal packaging waste management systems are analyzed and compared in terms of environmental and social impacts. The research is mainly based on a long term site observation, data collection and existing system analysis. Environmental performances of alternative scenarios are calculated based on the existing system data, whereas more site observations and interviews with stakeholders are conducted for the determination of social impacts. In the analysis of both environmental and social impacts of the scenarios, life cycle assessment used as a methodological approach. Results of the study show that informal collection systems are environmentally more effective than the formal collection systems. Even the resource consumption is high in these systems; they are still environmentally beneficial because of the high material collection rate. On the other hand, social impact assessment results indicate that informal collection system has serious social disadvantages compared to the formal systems. And finally, it is found that environmental and social weaknesses of the system could be minimized with integrated system applications.