WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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Article Effects of a Period and a Contact Angle on Absorption Performance of Hemispherical-Shell-Shaped Organic Photovoltaic Cells(SPIE-Soc Photo-Optical Instrumentation Engineers, 2026-02-17) Hah, DooyoungFor wearable electronics applications, organic photovoltaic (OPV) cells are good candidates as sources of renewable energy. Many efforts have been devoted to increasing energy conversion efficiency in OPV cells, and improvement in light retention has been one of the main research directions. Within this context, our group recently proposed an OPV cell structure with a hemispherical-shell-shaped (HSS) active layer and discovered that it has high potential for substantial enhancement in absorption performance. As a continuation of the study, this paper reports an in-depth investigation of the proposed device, examining the effects of several design parameters on its absorption performance. Using finite element analysis, it is found that the absorption performance depends on the periodicity type, and that a hexagonal type results in higher absorption than a square one due to its closer shape resemblance to a circular cross-section. The absorption performance is also affected by a contact angle, i.e., the angle made between a sphere and a flat part of the structure. It is learned that the average integrated absorption generally increases along with the contact angle, which saturates at around 80 deg of contact angle. Lastly, the effects of a cell period are studied, and it turns out that the average integrated absorption decreases as the period increases. It is also observed that at high incidence angles (>similar to 75 deg ), an array with a shorter period results in lower absorption than one with a longer period owing to a partial obstruction issue. All of these results support the understanding that the primary contribution of absorption enhancement in the proposed HSS structure comes from improved light retention rather than from a simple advantage in active layer volume. It is envisaged that these study outcomes will provide important guidelines in the design of HSS OPV cells.Article Citation - WoS: 190Citation - Scopus: 203The Role of Economic Policy Uncertainty in the Energy-Environment Nexus for China: Evidence From the Novel Dynamic Simulations Method(Academic Press Ltd- Elsevier Science Ltd, 2021-08) Amin, Azka; Dogan, EyupEven though a great number of researches have explored the determinants of carbon emissions, the impact of economic policy uncertainty (EPU) on the environment has not been fully investigated in the energy-environment literature. Since recent studies show a strong relationship between the external environment and uncertainty, the present study for the first time in the literature aims to explore the function of EPU in the energy-environment nexus for China by using the novel bounds testing with dynamic simulations. The empirical results indicate that increases in the real income and energy intensity contribute to environmental pollution while increases in renewable energy lower the level of emissions. Besides, an increase in EPU causes an increase in the volume of carbon emissions. As EPU increases, the government's attention to implement environmental protection policies decreases, and the execution of the environment-related strategies is likely directed in an expected way. The empirical findings suggest that the government should establish consistency in economic and environmental policies to mitigate environmental pollution and thus to reach environmental sustainability.Article Citation - WoS: 347Citation - Scopus: 388The Influence of Renewable and Non-Renewable Energy Consumption and Real Income on CO2 Emissions in the USA: Evidence From Structural Break Tests(Springer Heidelberg, 2017-03-14) Dogan, Eyup; Ozturk, IlhanThe objective of this study is to explore the influence of the real income (GDP), renewable energy consumption and non-renewable energy consumption on carbon dioxide (CO2) emissions for the United States of America (USA) in the environmental Kuznets curve (EKC) model for the period 1980-2014. The Zivot-Andrews unit root test with a structural break and the Clemente-Montanes-Reyes unit root test with a structural break report that the analyzed variables become stationary at first-differences. The Gregory-Hansen cointegration test with a structural break and the bounds testing for cointegration in the presence of a structural break show CO2 emissions, the real income, the quadratic real income, renewable and non-renewable energy consumption are cointegrated. The long-run estimates obtained from the ARDL model indicate that increases in renewable energy consumption mitigate environmental degradation whereas increases in non-renewable energy consumption contribute to CO2 emissions. In addition, the EKC hypothesis is not valid for the USA. Since we use time-series econometric approaches that account for structural break in the data, findings of this study are robust, reliable and accurate. The US government is advised to put more weights on renewable sources in energy mix, to support and encourage the use and adoption of renewable energy and clean technologies, and to increase the public awareness of renewable energy for lower levels of emissions.Article Citation - WoS: 810Citation - Scopus: 926The Influence of Real Output, Renewable and Non-Renewable Energy, Trade and Financial Development on Carbon Emissions in the Top Renewable Energy Countries(Pergamon-Elsevier Science Ltd, 2016-07) Dogan, Eyup; Seker, FahriDue to tremendous increase in the level of carbon dioxide (CO2) emissions in the last several decades, a number of studies in the energy-growth-environment literature have attempted to identify the determinants of CO2 emissions. A major criticism related to the existing studies, we realize, is the selection of panel estimation techniques. Almost all studies use panel methods that ignore the issue of cross-sectional dependence even though countries in the panel are most likely heterogeneous and cross-sectionally dependent In addition, the majority of existing studies use aggregate energy consumption, and thus fail to identify the impacts of energy consumption by sources on the environment In order to fulfill the mentioned gaps in the literature, this empirical study analyzes the influence of the real income, renewable energy consumption, non-renewable energy consumption, trade openness and financial development on CO2 emissions in the EKC model for the top countries listed in the Renewable Energy Country Attractiveness Index by employing heterogeneous panel estimation techniques with cross-section dependence. We find that the analyzed variables become stationary at their first-differences by using the CADF and the CIPS unit root tests, and the analyzed variables are cointegrated by employing the LM bootstrap cointegration test By using the FMOLS and the DOLS, we also find that increases in renewable energy consumption, trade openness and financial development decrease carbon emissions while increases in non-renewable energy consumption contribute to the level of emissions, and the EKC hypothesis is supported for the top renewable energy countries. (C) 2016 Elsevier Ltd. All rights reserved.Article Citation - WoS: 194Citation - Scopus: 217The Impact of Renewable Energy Consumption to Economic Growth: A Replication and Extension of Inglesi-Lotz (2016)(Elsevier, 2020-08) Dogan, Eyup; Altinoz, Buket; Madaleno, Mara; Taskin, DilvinThis study replicates and extends the results presented in a top-cited article in this journal, Inglesi-Lotz (2016), which analyzes the impact of renewable energy consumption to economic growth for the OECD countries by applying the ordinary least squares with fixed effect estimator on the data from 1990 to 2010. By using the same data and methods, this study first produces and compare empirical results with those reported in the original article. Then, it applies a set of new econometric methods on the same data to address heterogeneity in renewable energy and economic growth across the analyzed group of countries. The panel quantile regression estimation shows that the effect of renewable energy consumption on economic growth is positive for lower and lowmiddle quantiles; however, its effect becomes negative for middle, high-middle, and higher quantiles when renewable energy consumption is proxied by the absolute value. Furthermore, a negative impact of renewable energy on economic growth is observed in almost all quantiles when it is proxied by the share of renewable energy consumption to total energy consumption. These results greatly differ from those of the original study (C) 2020 Elsevier B.V. All rights reserved.Article Tapered Curved-Beam Hinges for Electret-Based Vibration Energy Harvesting Devices(IOP Publishing Ltd, 2024-12-01) Hah, DooyoungInterest in vibration energy harvesting have been growing recently for various applications. One of the major development goals for vibration energy harvesters has been improvement in energy conversion efficiency. To pursue that goal, one of the main approaches has been to broaden the spectra of harvesters. Employment of nonlinear springs, such as curved-beam hinges, has proven to be effective for that purpose. The main contribution of the current study is to introduce a lateral taper to the curved beam so as to further optimize the harvester performances. Via numerical analysis by using stochastic differential equations, the study shows that at 0.05g of vibration strength, tapered curved-beam hinges can result in higher electric power output than the non-tapered ones. Deformation-induced stress was taken into consideration as well, in reference to the fracture strength of the material (single-crystal silicon). At lower vibration strength (0.02g), spring nonlinearity becomes weaker, and as a result, the narrowest curved-beam hinge produces the highest output power. Overall, the current study demonstrates that tapering of the curved beam can be a useful addition in the vibration energy harvester design.Article Citation - WoS: 75Citation - Scopus: 89Revisiting the Nexus of Ecological Footprint, Unemployment, and Renewable and Non-Renewable Energy for South Asian Economies: Evidence From Novel Research Methods(Pergamon-Elsevier Science Ltd, 2022-07) Dogan, Eyup; Majeed, Muhammad Tariq; Luni, TaniaGiven the need to employ novel research methods in the energy-environment nexus, the objective of the present research is to investigate the impacts of real output, unemployment, and renewable and nonrenewable energy on ecological footprint under a STIRPAT theoretical framework by applying the second-generation unit root, cointegration, Granger-causality, and long-run estimation methods on the annual data from 1990 to 2017 for South Asian economies. Empirical results show that increases in unemployment and renewable energy decrease ecological footprint while increases in real income and non-renewable energy hurt the environment. This study confirms the adverse effect of renewable energy on environmental degradation as well as the trade-off between unemployment and pollution through multiple robustness and sensitivity checks. In addition, the causality test supports unidirectional causality from income, renewable energy, and non-renewable energy to ecological footprint. Regarding policy perspectives, the governments of the South Asian region should support the deployment of renewable energy through various channels and regulations. The development of technologies that promote sustainable production and consumption play critical roles for reducing the trade-off unemployment and ecological footprint. Further policy suggestions are discussed in the study.(c) 2022 Elsevier Ltd. All rights reserved.Article Citation - WoS: 4Citation - Scopus: 5Predicting Potential of Pressure Retarded Osmosis Power for Different Estuaries in Turkey(Wiley, 2018-11-29) Saki, Seda; Uzal, Nigmet; Gokcek, Murat; Ates, NurayPressure retarded osmosis (PRO) is an alternative renewable energy source recovered from the salinity gradient between the fresh water (feed solution) and salty water (draw solution). In order to implement osmotic power, the site-specific characteristics including the river and sea salinity, annual flow rates, ecological restrictions were taken into account. This study revealed a comprehensive analysis for a theoretical potential of PRO process for different estuaries in Turkey. In this study, the power potential prediction of PRO process for the Ceyhan, Sakarya, and Meric Rivers were analyzed via Gibbs free energy calculations. The net annual energy production is projected to be 167, 164, and 208 GWh/y for Ceyhan, Sakarya, and Meric Rivers, respectively. Meric River has the highest energy production of 208 GWh/yr with 186 m(3)/s mean flow rate and 245 mg/L salinity. These results clearly show that Turkey's rivers having high salinity and flow rate are feasible and applicable for making the osmotic power plant economically. Thereby, it is providing essential direction to the improvement of its design, installation, and operation. The developed methodology for the evaluation of the osmotic power potential of other rivers can be considered as a basis to assess the whole potential on a worldwide level. (c) 2018 American Institute of Chemical Engineers Environ Prog, 38:e13085, 2019Article Citation - WoS: 285Citation - Scopus: 318Potential Ion Exchange Membranes and System Performance in Reverse Electrodialysis for Power Generation: A Review(Elsevier Science Bv, 2015-07) Hong, Jin Gi; Zhang, Bopeng; Glabman, Shira; Uzal, Nigmet; Dou, Xiaomin; Zhang, Hongguo; Chen, YongshengReverse electrodialysis (RED) is an emerging membrane based energy conversion process used to extract electricity by mixing two water streams of different salinities. This technique utilizes transport of cations and anions during controlled mixing of saltwater and freshwater through selective ion exchange membranes. The development of ion exchange membranes and optimization of system performance are crucial for sustainable energy capture from salinity gradients using RED. Recently, increased attention has been given to the preparation of ion exchange membranes and to understanding the factors that determine the RED power performance. This review evaluates potential ion exchange membrane materials, currently available state-of-the-art RED membranes, and their key properties. Discussion will focus on the electrochemical and physical properties of these membranes (e.g., resistance, permselectivity, and swelling) because of their significant role in RED performance throughout the system, Although an interconnected relationship exists between membrane properties, RED requires high quality membranes that are uniquely tailored to have a low resistance and high permselectivity. Moreover, harnessing this potential technology demands not only carefully optimized components but also a novel RED stack design and system optimization. The key findings and advancements needed to assure proper stack design and optimization are also described. This review paper's goal is to elucidate effective energy conversion from salinity gradients and expedite implementation of RED as the next promising renewable source of power for large-scale energy generation. (C) 2015 Elsevier B.V. All rights reserved.Article Citation - WoS: 20Citation - Scopus: 22Multi-Objective Turbine Allocation on a Wind Farm Site(Elsevier Sci Ltd, 2024-02) Dincer, A. E.; Demir, A.; Yilmaz, K.The Multi-Objective Turbine Allocation (MOTA) method is introduced as a novel approach for wind farm layout optimization and site selection. By incorporating Geographic Information System (GIS) tools and the Analytical Hierarchy Process (AHP), the MOTA method offers a comprehensive solution to balance energy production, cost factors, and environmental impacts. In this study, the MOTA method is applied to Go center dot kceada, Turkiye, for wind farm development. Results show that the MOTA method effectively proposes the optimum wind farm layout by selecting the best site for each turbine. The sequential turbine allocation approach, integration of multiple objectives, and use of GIS tools and AHP are the key capabilities and novelties of the MOTA method. The method allows for flexible investment decisions, considering technical and economic aspects. The outcomes from the Go center dot kceada case study highlight the effectiveness of the MOTA method in maximizing energy production while considering cost factors and environmental impacts. The results indicate that for the selected objective functions, the optimal net profit is attained with the installation of 155 turbines on Go center dot kceada. The MOTA method presents a practical and efficient solution for wind farm development, contributing to sustainable and efficient renewable energy generation.
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