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Öğe Analysis of Energy Supply, Installed Power and Renewable Capacity in the World, the EU and Turkey(2021) Çelik, Ali NaciIn the present study, a review of energy structure of the world, the European Union and Turkey are carried out, by giving a specific emphasis to the development of renewable energy. The global primary energy use reached 13865 Mtoe as of 2018. Today, more than 80% of the energy currently used in the world is still provided from fossil based non-renewable energy resources, the main energy resources being oil, coal and natural gas, with the shares 32%, 27% and 22%, respectively. In the years after 1973 oil crisis, renewable energy emerged as a potential source for contributing to the global energy production. The installed capacity of renewable energy (excluding hydro) reached 1180 GW globally as of 2018 that corresponds to an increase of 8% compared to the previous year. Amongst the renewable resources, wind holds the largest share with 563.7 GW, corresponding to 47.8% of the installed renewable capacity. Wind is closely followed by solar PV with 480.4 GW, constituting 40.7% of the total installed power of renewable energy. The total installed capacity of bioenergy (biomass, biofuels, and biogas) is 103.1 GW, corresponding to 8.7%. The global capacity of hydroelectric power was realized as 1127 GW as of 2018. Total of 1668.1 TWh electricity was generated in the world in 2018 by the renewable resources including wind, solar, geothermal, tide, wave and ocean.Öğe Artificial neural network modelling and experimental verification of the operating current of mono-crystalline photovoltaic modules(Pergamon-Elsevier Science Ltd, 2011) Çelik, Ali NaciThis article presents the artificial neural network modelling of the operating current of a 120 Wp of mono-crystalline photovoltaic module. As an alternative method to analytical modelling approaches, this study uses the advantages of neural networks such as no required knowledge of internal system parameters, less computational effort and a compact solution for multivariable problems. Generalised regression neural network model is used in the present article to predict the operating current of the photovoltaic module. To show its merit, the current predicted from the artificial neural network modelling is compared to that from the analytical model. The five-parameter analytical model is drawn from the equivalent electrical circuit that includes light-generated current, diode reverse saturation current, and series and shunt resistances. The operating current predicted from both the neural and analytical models are compared to the measured current. Results have shown that the artificial neural network modelling provides a better prediction of the current than the five-parameter analytical model. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Critical evaluation of wind speed frequency distribution functions(Amer Inst Physics, 2010) Çelik, Ali Naci; Makkawi, A.; Muneer, T.Over the past few years a number of new mathematical functions have been proposed for wind speed probability density distributions. The most commonly used function that has been cited in literature has been the two-parameter Weibull function. However, in recent years studies have shown that the two-parameter Weibull function might be inadequate in modeling the wind speed probability density distributions or independent of whether the distribution is of unimodal or bimodal nature. For the unimodal distributions, the inadequacy may be due to the intricate behavior of the distribution, which prevents it to be satisfyingly modeled by a two-parameter model. For the bimodal behavior, the two-parameter Weibull function, which produces only a unimodal distribution, is simply inadequate to model it appropriately. Therefore, in recent years, alternative functions have been suggested for both unimodal and bimodal distributions, seeking more involved functions to better model these distributions. This article involves the modeling of observed wind speed probability density distributions using the main body of models found in the literature, namely, Rayleigh, Lognormal, two-parameter Weibull, three-parameter Weibull, and bimodal Weibull probability distribution functions. One of the important steps in the evaluation of different functions is the interpretation of the statistical parameters, namely, slope, R(2), mean bias error, and root mean squared error, as are presently used in this article. A novel statistical tool is developed in the present article using these four statistical parameters. The novel tool can be used to evaluate the relative performance of models when more than one model is involved or to determine the overall accuracy of a particular model for a specific site. The calculations are made based on the long term wind speed data collected at 4-s interval at the experimental site at Edinburgh Napier University. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3294127]Öğe Design and analysis of kinetic energy recovery system for automobiles: Case study for commuters in Edinburgh(Amer Inst Physics, 2011) Walsh, John; Muneer, Tariq; Çelik, Ali NaciTransport and its energetic and environmental impacts affect our daily lives. The transport sector is the backbone of the United Kingdom's economy with 2.3 million people being employed in this sector. With a high dependency on transport for passengers and freight and with the knowledge that oil reserves are rapidly decreasing a solution has to be identified for conserving fuel. Passenger vehicles account for 61% of the transport fuel consumed in the U. K. and should be seen as a key area to tackle. Despite the introduction and development of electric powered cars, the widespread infrastructure that is required is not in place and has attributed to their slow uptake, as well as the fact that the electric car's performance is not yet comparable with the conventional internal combustion engine. The benefits of the introduction of kinetic energy recovery systems to be used in conjunction with internal combustion engines and designed such that the system could easily be fitted into future passenger vehicles are examined. In this article, a review of automobile kinetic energy recovery system is presented. It has been argued that the ultracapacitor technology offers a sustainable solution. An optimum design for the urban driving cycle experienced in the city of Edinburgh has been introduced. The potential for fuel savings is also presented. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3549152]Öğe Experimental investigation into efficiency of SiO2/water-based nanofluids in photovoltaic thermal systems using response surface methodology(Pergamon-Elsevier Science Ltd, 2022) Geliş, Kadir; Çelik, Ali Naci; Özbek, Kadir; Özyurt, ÖmerPhotovoltaic thermal systems (PVT) are systems that can convert solar energy into electricity and thermal energy simultaneously. In this study, the effect of nanofluids on the electrical and thermal efficiency of PVTs was investigated using the Response Surface Methodology (RSM). In the experimental study presently undertaken, SiO2 nanoparticles were suspended in deionized water, which was used as base fluid in 3 different volumetric ratios (0.1-0.2-0.3). A mathematical model has been developed to calculate the thermal and electrical efficiency of the PVT system using the RSM approach. In the RSM method, the flow rate of the nanofluid, the nanofluid volumetric concentration, and the solar radiation were determined as independent variables, and their effects on the thermal and electrical efficiency of PV/Ts were statistically investigated. The model presently developed was validated based on the analysis of variance (ANOVA). The most influential parameters affecting the electrical and thermal efficiencies have been found as radiation, flow rate and volumetric concentration, respectively. The variance between the mathematical models developed and the experimental results was measured in terms of the coefficient of determination (R-2), which was between 0.85% and 1.91% for the electrical efficiency and between -6.34% and 1.06%. for the thermal efficiency. As a result, the mathematical models developed for the electrical and thermal efficiencies of the PV/T system has been successfully verified based on the experimental outcomes.Öğe Generalized feed-forward based method for wind energy prediction(Elsevier Sci Ltd, 2013) Çelik, Ali Naci; Kolhe, MohanEven though a number of new mathematical functions have been proposed for modeling wind speed probability density distributions, still the Weibull function continues to be the most commonly used model in the literature. Therefore, the parameters of this function are still widely used to obtain typical wind probability density distributions for finding the wind energy potential by researchers, engineers and designers. Once long-term average of Weibull function's parameters are known, then the probability density distributions can easily be obtained. Artificial neural network (ANN) can be used as alternative to analytical approach as ANN offers advantages such as no required knowledge of internal system parameters, compact solution for multi-variable problems. In this work, a generalized feed-forward type of neural network is used to predict an annual wind speed probability density distribution by using the Weibull function's parameters as inputs. For verifying its validity and merits, the annual wind speed probability density distribution is also predicted by using the Weibull function. The wind speed distribution predicted from the ANN modeling is compared with the analytical model's results. Total 9 year long hourly wind speed data, belonging to one of the windiest locations in Turkey with mean wind speed of over 6 m/s, are used in this study. It is observed that ANN based wind speed distribution estimation gives better results for calculating the energy output from some commercial wind turbine generators. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Modeling and experimental verification of solar radiation on a sloped surface, photovoltaic cell temperature, and photovoltaic efficiency(Asce-Amer Soc Civil Engineers, 2013) Aldali, Yasser; Çelik, Ali Naci; Müneer, TariqThis article presents modeling and experimental verification of conversion of solar irradiation from horizontal to sloped surfaces and photovoltaic cell temperature and an analysis of photovoltaic conversion efficiency. Modeling and validation of the models are carried out on the basis of measurements conducted using the experimental system set in a city in southern Turkey. In addition to current, voltage, and cell temperature of the photovoltaic module, environmental variables such as ambient temperature and solar irradiance were measured and used for validation purposes. Correlation of conversion of solar irradiation from horizontal to sloped surfaces indicated that the presently used model is highly successful because of the fitting parameters: the coefficient of determination (R-2) = 0.97, and themean bias error (MBE) = -2.2. Similarly, the cell temperature model used in the present article is validated by the following correlation parameters: (R-2) = 0.97, MBE = 0.7, and root-mean-square error (RMSE) = 2.1. DOI: 10.1061/(ASCE)EY.1943-7897.0000082. (C) 2013 American Society of Civil Engineers.Öğe Multi-objective optimization of a photovoltaic thermal system with different water based nanofluids using Taguchi approach(Pergamon-Elsevier Science Ltd, 2023) Geliş, Kadir; Özbek, Kadir; Özyurt, Ömer; Çelik, Ali NaciIn this study, the effect of different nanofluids on the electrical and thermal efficiencies of photovoltaic thermal (PVT) systems was investigated experimentally and the variables affecting the efficiency were optimized by the Taguchi method. Experiments were carried out under laboratory conditions on the PVT system presently developed. In this study, a novel partitioned cooler block in the form of a rectangular prism was designed and used. Thus, the contact between the cooler block and the back surface of the PV panel and the associated PVT efficiency were increased. The following physical characteristics have been identified as the independent vari-ables for the experiments carried out: SiO2/Water, Al2O3/Water and CuO/Water as different types of nanofluid, 0.1, 0.2 and 0.3 as volumetric concentration, 0.55, 1.1 and 1.65 lpm as volumetric flow rate and 300, 600 and 900 W/m2 as irradiance level. The reliability of the measurements made during the experiments was ascertained through the uncertainty analysis performed. The maximum electrical efficiencies of the PVT system for SiO2/ Water, Al2O3/Water, and CuO/Water nanofluids were found to be 20.69 %, 21.18 %, and 20.77 %, and the maximum thermal efficiencies to be 57.06 %, 63.01 %, and 66.49 %, respectively. As the optimization method for determining the most optimum combination of variables, Taguchi analysis has been employed. As a result of this analysis, it has been shown that the most effective variables on the electrical efficiency of the PVT system are the irradiance, flow rate, volumetric concentration, and nanofluid type, respectively. On the other hand, regarding the thermal efficiency of the PVT system, the most effective variables are the irradiance, flow rate, nanofluid type, and volumetric concentration, respectively.Öğe Neural network based method for conversion of solar radiation data(Pergamon-Elsevier Science Ltd, 2013) Çelik, Ali Naci; Muneer, TariqThe receiving ends of the solar energy conversion systems that generate heat or electricity from radiation is usually tilted at an optimum angle to increase the solar incident on the surface. Solar irradiation data measured on horizontal surfaces is readily available for many locations where such solar energy conversion systems are installed. Various equations have been developed to convert solar irradiation data measured on horizontal surface to that on tilted one. These equations constitute the conventional approach. In this article, an alternative approach, generalized regression type of neural network, is used to predict the solar irradiation on tilted surfaces, using the minimum number of variables involved in the physical process, namely the global solar irradiation on horizontal surface, declination and hour angles. Artificial neural networks have been successfully used in recent years for optimization, prediction and modeling in energy systems as alternative to conventional modeling approaches. To show the merit of the presently developed neural network, the solar irradiation data predicted from the novel model was compared to that from the conventional approach (isotropic and anisotropic models), with strict reference to the irradiation data measured in the same location. The present neural network model was found to provide closer solar irradiation values to the measured than the conventional approach, with a mean absolute error value of 14.9 Wh/m(2). The other statistical values of coefficient of determination and relative mean absolute error also indicate the advantage of the neural network approach over the conventional one. In terms of the coefficient of determination, the neural network model results in a value of 0.987 whereas the isotropic and anisotropic approaches result in values of 0.959 and 0.966, respectively. On the other hand, the isotropic and anisotropic approaches give relative mean absolute error values of 11.4% and 11.5%, respectively, while that of the neural network model is 9.1%. (C) 2012 Elsevier Ltd. All rights reserved.Öğe A novel cooler block design for photovoltaic thermal systems and performance evaluation using factorial design(Elseiver, 2022) Geliş, Kadir; Özbek, Kadir; Çelik, Ali Naci; Özyurt, ÖmerPhotovoltaic (PV) cells have the capacity to absorb up to 80% of incoming solar radiation, converting a part of this radiation into electricity. The power output of PV panels are rated at 25 C and an increase over this nominal operating cell temperature causes a decrease in the energy conversion efficiency of PV panels when compared to the rated power. With photovoltaic thermal (PVT) systems, it is possible to reduce the panel temperature and thus increase the electrical efficiency, and simultaneously obtain electrical and thermal energy. Various thermal collector designs used in PVTs have been studied experimentally and numerically in the literature. In the present study, a detailed literature review for such thermal collector designs was carried out and then a novel cooler design that is different from the designs existing in the literature was developed, manufactured and tested. The effect of the present design on the efficiency of the PVT system was analyzed experimentally and statistically. Experiments were designed by factorial design approach and carried out in laboratory conditions. Furthermore, a mathematical model was developed for the electrical and thermal efficiencies of the PVT system presently studied. Experiments were carried out at volumetric flow rates of 0.55 L/min, 1.1 L/min and 1.65 L/min and radiation values of 300 W/m(2), 600 W/m(2), and 900 W/m(2). The highest electrical efficiency of the PVT system was 17.69% at 900 W/m(2) and 1.65 L/min and the thermal efficiency 58.5% at 900 W/m(2) and 0.55 L/min. When compared with the electrical efficiency of the conventional PV panel at 900 W/m(2) radiation, it was observed that the electrical efficiency of the novel design increased by 4.67%. In addition, it was observed that the electrical efficiency decreased and the thermal efficiency increased with the increase of the panel temperature.Öğe Polikristal tür bir Fotovoltaik panelin I-V karakteristiğinin analitik modellenmesi ve deneysel doğrulanması(2020) Çelik, Ali Naci; Koç, FatihFotovoltaik hücreler, güneşten gelen elektromanyetik enerjiyi elektrik enerjisine dönüştüren enerji dönüşüm sistemleridir. Bu çalışmada 40°42’52.2”K, 31°31’29.8”D koordinatlarında kurulu bulunan 36 hücreli polikristal tür bir güneş paneli, çeşitli sensörler ve veri kaydedici cihazlar kullanılarak hazırlanan deney düzeneği temelinde; i) güneş ışınım şiddetinin fotovoltaik panel üzerindeki etkisinin incelenmesi, ii) fotovoltaik panelin akım-voltaj (I-V) karakteristiğinin incelenmesi, iii) fotovoltaik panelden elde edilen akım-voltaj eğrilerinin literatürdeki modeller ile karşılaştırılması ve doğrulanması amaçlanmıştır. Söz konusu fotovoltaik panel için farklı güneş ışınım şiddetinde ve farklı sıcaklıklarda ölçülen I-V karakteristikleri; 4-değişkenli, 5-değişkenli, geliştirilmiş 4-değişkenli ve 2-diyotlu model olmak üzere toplam 4 farklı analitik model kullanılarak modellenmiş ve doğrulanmıştır. I-V ilişkisini tanımlayan analitik denklemler Visual Basic programlama dili kullanılarak çözümlenmiştir. Modellerden elde edilen sonuçlar ile ölçülen değerler arasındaki karşılaştırma R² ve RMSE olmak üzere 2 istatistiksel parametre üzerinden gerçekleştirilmiştir. Farklı ışınım değerleri ve sıcaklıklar için modellerden elde edilen sonuçlar ile ölçüm değerleri karşılaştırıldığında ?? 2 değerlerinin %95,86 ile %99,86 arasında, RMSE değerlerinin ise 0,093 ile 0,861 değiştiği gözlenmektedir. Elde edilen sonuçların istatistiksel analizi; bu çalışma kapsamında kullanılan 4 farklı model içerisinde, geliştirilmiş 4-değişkenli modelin diğer modellere göre daha başarılı tahmin sonuçlarına yol açtığını göstermektedir.Öğe Review of Turkey's current energy status: A case study for wind energy potential of Canakkale province(Pergamon-Elsevier Science Ltd, 2011) Çelik, Ali NaciTurkey is a free market economy that is oriented towards Western markets. It also has strong ambitions to join the European Union and this factor has been beneficial but also taxing with respect to its changing economic situation. Turkey imports nearly 70% of its energy requirements. The country spends 40-50% of its total export income to import fuel, mainly crude oil and natural gas. On the other hand, Turkey has significant wind energy potential because of its geographical characteristics, such as its shoreline and mountain-valley structures. The sea fronts of the Agean, Marmara, Mediterranean, and Black Seas, and some places of the Southeast Anatolian belt have a high wind potential, with an average speed of 4.5-10 m/s. Studies put wind-energy potential in terms of the technical aspects in the region of 80 GW. Canakkale province that has more than 10% of the country's total installed wind power has been presently chosen for the case study. In the present study, hourly time-series wind data recorded from the year 2000 to 2005 at a height of 10 m in Canakkale city centre and Bozcaada, an island in the Aegean Sea belonging to the Canakkale province, has been statistically analysed. Overall, Bozcaada, with an annual mean density value higher than 350 W/m(2), offers a much higher wind potential than the former location, indicating sufficient wind potential for large scale electricity generation. The mean power density value in the northeastern direction is highest for the typical year in Bozcaada with a value of 901.6 W/m(2), while the directional power density distribution shows that over 60% of the wind energy comes from the band between northern and northeastern directions. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Review of Turkey's photovoltaic energy status: Legal structure, existing installed power and comparative analysis(Pergamon-Elsevier Science Ltd, 2020) Çelik, Ali Naci; Özgür, EvrenEnergy is defined as the ability to do work and can be converted through variety of processes and used in various applications. Primary energy sources such as petroleum, natural gas, coal, wood, solar etc. can be directly used without being converted to another type of energy. Secondary energy sources, of which electricity and fuel oil are typical examples, are form of energies that are transformed from primary energy sources and are more expensive because of the conversion process and the losses associated. Starting especially with the industrial revolution, meeting the energy demand has been one of the most important concerns of countries. Starting from 1970's, enforced in particular by the energy crisis, humankind have turned to renewable energy since the production of petroleum, which was the main energy source then, faced an unprecedented shortage and thus increased prices. As one of the main renewable energy sources, solar energy has made a rapid progress in the past decades, with variety of technologies, such as photovoltaics, thermal converters, passive architectural systems and so on. Photovoltaics, which convert solar energy directly into electrical energy, presently play an important role in energy policies of countries. As a developing country, Turkey is experiencing a rapid annual growth of energy demand, including electricity. However, Turkey is extensively dependent on the imported fossil fuel for meeting the increasing demand, with a limited domestic reserve. Therefore, the present energy policy of Turkey is based on cutting down the amount of fossil fuel imported. Solar and wind energies are two of the main candidates to play a major role in cutting down the amount of fossil fuel presently used. In the present study, Turkey's solar energy potential and photovoltaic development are analyzed. With a relatively high solar energy potential, Turkey's installed photovoltaic capacity and photovoltaic electricity generation are analyzed in comparison to 5 selected European Union countries (EU-5). In addition, the ratio of installed photovoltaic capacity per capita to solar potential has been analyzed as a function of gross national product. The results indicate that the installed capacities and power generation of countries are not in direct proportion with their solar energy potential. It has also been concluded that Turkey's photovoltaic development is not sufficient in comparison to the EU-5 countries and effective incentive policies are required to be implemented rapidly in order for Turkey to reach their level.Öğe Sustainable transport solution for a medium-sized town in Turkey-A case study(Elsevier Science Bv, 2011) Muneer, T.; Çelik, Ali Naci; Çalışkan, N.The United Nations projects that 60% of the world's population will be living in urban areas by 2030. Cities account for 2% of the world's area but 75% of the world's energy consumption. For over a century, the automobile has offered affordable freedom of movement within urban areas. However, with the current vehicle population exceeding 850 million, almost all of which are powered by internal combustion engines this situation is becoming unsustainable. In this article a critical review of the present energy budget of Turkey and its over dependence on imported fuel oil to support the transport sector is carried out. By way of having a closer examination of the energy needs for the private vehicle fleet, experimental work was undertaken for one town in western Turkey-Bolu. The latter town represents a typical municipality in Turkey with the possibility of replication of the present work to other similar conurbations. The work entailed determination of the driving cycle. A software program that has been expressly developed for this type of exercise was then used to ascertain the savings in fossil fuel that may be achieved via use of solar PV-electric vehicles. It has been presently argued that the use of electricity-propelled, two-and four-wheelers offers a sustainable solution. (C) 2010 Elsevier B.V. All rights reserved.Öğe A sustainable transport solution for a Slovenia town(Oxford Univ Press, 2015) Knez, Matjaz; Çelik, Ali Naci; Muneer, TariqAuthorities in Slovenia and other EU member states are confronted with problems of city transportation. Fossil-fuel-based transport poses two chief problems-local and global pollution, and dwindling supplies and ever-increasing costs. An elegant solution is to gradually replace the present automobile fleet with electric vehicles (EVs). This article explores the economics and practical viability of the provision of solar electricity for the charging of EVs by installation of economical available Photovoltaic modules. A steep decline in the module, inverter and installation costs is reported herein. Present estimates indicate that for the prevailing solar climate of Celje-a medium-sized Slovenian town-the cost would be only 2 euros and 11 cents per kWh of generated solar electricity.Öğe Three-dimensional multiphysics model of a planar solid oxide fuel cell using computational fluid dynamics approach(Pergamon-Elsevier Science Ltd, 2018) Çelik, Ali NaciA multiphysics model of a planar solid oxide fuel cell has been developed based on computational fluid dynamics approach and validated by cell level experiment in the present article. The three-dimensional model of multiphysics nature includes the full-field computational fluid dynamics solutions coupled with the electrochemical model for a planar type of solid oxide fuel cell developed in the Technical University of Denmark. The software COMSOL Multiphysics was used to solve the equations in three-dimensions. With the employment of appropriate boundary conditions at respective parts and through solving the fluid dynamics, heat transfer and electrochemical equations, pressure, velocity, temperature and current density fields were established for a given cell voltage. It is shown that the spatial variation of mole fractions of species are determined by the rate of electrochemical reactions, while that of hydrogen reaching maximum at locations beneath the interconnect ribs and that of oxygen reducing to the fractional level of 2.3 x 10(-4) within the active cathode layer due to the mass flow resistance. The variation of temperature increases as the flow proceeds along the main flow direction due to the electrochemical reactions as well as the ohmic and activation overpotentials. It was shown that the exchange current density field for the anode is determined by the temperature distribution caused by the highly exothermic process of formation of water, and also by the partial pressures of hydrogen and water. It was further established that the variation of over potential at the anode/electrolyte interface are justified by the mechanisms of irreversible ohmic and activation losses taking place within the cell, a high electronic conductivity in certain locations and the relatively higher ohmic overpotential in respective regions. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
