Yazarlar
- Ozden, Talat(16)
- Akinoglu, Bulent G.(15)
- Sezer, İsmet(11)
- Basoglu, Mustafa Engin(9)
- Özden, Talat(8)
- Akpinar, Adem(7)
- Terhan, Meryem(7)
- Başoğlu, Mustafa Engin(6)
- Cakmak, Recep(6)
- Erol, Ismail(6)
- Peker, Iskender(6)
- Turan, Rasit(6)
- Akpinar, A.(5)
- Ar, Ilker Murat(5)
- Kömürcü, Murat Ihsan(5)
- Sezer, Ismet(5)
- Altas, Ismail H.(4)
- Altuner, Elif Esra(4)
- Benli, Tolga(4)
- Bozbeyoglu, Pinar(4)
- Kaygusuz, K.(4)
- Tunç, Merve Tuğçe(4)
- Akyol, Mehmet(3)
- Altan, Aytaç(3)
- Barut, Abdulkadir(3)
- Bilgin, Atilla(3)
- Genc, Omer(3)
- Kankal, Murat(3)
- Kaygusuz, Abdullah(3)
- Kaygusuz, Kamil(3)
- Ozden, T.(3)
- Pilatin, Abdulmuttalip(3)
- Saribiyik, Oguz Yunus(3)
- Searcy, Cory(3)
- Timurkutluk, Bora(3)
- Toros, Serkan(3)
- Turan, İsmet(3)
- Yanarates, Cagfer(3)
- Yanarateş, Cağfer(3)
- Çakmak, Recep(3)
Yayınlar
- Derleme MakaleYalnız künye2018A Review Study on the Using of Diethyl Ether in Diesel Engines: Effects on Fuel Properties and Engine Performance
Sezer, İsmet
This study was compiled from the results of various researches performed on using diethyl ether as a fuel or fuel additive in diesel engines. Three different techniques are used the reduction of the harmful exhaust emissions of diesel engines. The first technique for the reduction of harmful emissions is improved the combustion by modification of engine design and fuel injection system, but this process is expensive and time consuming. The second technique is the using various exhaust gas devices like catalytic converter and diesel particulate filter. However, the use of these devices affects negatively diesel engine performance. The final technique to reduce emissions and also improve diesel engine performance is the use of various alternative fuels or fuel additives. The major pollutants of diesel engines are oxides of nitrogen (NOx) and particulate matter (PM). It is very difficult to reduce NOx and PM simultaneously in practice. The most researches declare that the best way to reduce is the use of various alternative fuels i. e. natural gas, biogas, biodiesel or using the additives with alternative fuels or conventional diesel fuel. Therefore, it is very important that the results of various studies on alternative fuels or fuel additives are evaluated together to practice applications. Especially, this study focus on the use diethyl ether in diesel engines as fuel or fuel additive in various diesel engine fuels. This review study investigates the effects of diethyl ether addition on the fuel properties and performance characteristics.
- BildiriAçık Erişim2017Effect of Ambient Conditions on Monthly Performances of Three Different PV Arrays
Özden, Talat; Akinoglu, Bulent G.; Turan, Rasit; Martinez, V; Gonzalez, J
Solar PV cells may be mainly divided into two parts as crystalline and thin film. Mono-crystalline silicon (e.g. Mono-Si) and microcrystalline based amorphous silicon and other thin films (e.g. gc-Si/a-Si and CdTe thin films) are widely used PV cells in the arrays. The outdoor performances of these systems depend on some climatic parameters and conditions, and it is important to understand how the monthly efficiencies vary with these parameters. In the present study, the data obtained from three grid connected PV arrays of Mono Si, a-Si/p.c-Si and CdTe thin film that were operated for 41 months in Ankara-Turkey is analyzed. The results showed that Mono-Si an-ay performance depends on the 5 parameters of outdoor climatic conditions while a-Si/gc-Si and CdTe thin film arrays performances arc not significantly affected by the variation of the climatic parameters. The possible reasons are discussed in details.
- MakaleYalnız künye2017Determination of optimum ejector operating pressures for anodic recirculation in SOFC systems
Genc, Omer; Toros, Serkan; Timurkutluk, Bora
In this study, a numerical analysis of an ejector for micro combined heat and power system based on 18 kW Solid Oxide Fuel Cell (SOFC) using methane as fuel is presented. An ejector design, which reflects the real system conditions in the view of the flow characteristics, is provided and the ejector performance is numerically investigated for various methane pressure to exhaust pressure ratios and methane inlet temperatures. The results show that the fuel inlet temperature and the pressure ratio of the methane to exhaust significantly affect the steam to carbon ratio (STCR) and entrainment ratio. The higher pressure ratio and methane temperature allow a high entrainment ratio and STCR, but as pressure ratio and methane temperature increase, STCR and entrainment ratio remain unchanged after a specific value. 1140 different scenarios related with the inlet and outlet pressures of the ejector and methane temperature are created to determine the optimum operating conditions. The simulations show that the optimum methane inlet pressure is 7 bar and exhaust pressure is 1.159 bar for the ejector geometry of the interest. The entrainment ratio and STCR are determined as 2.05 and 0.92, respectively at this optimum scenario.
- DüzeltmeYalnız künye2017Retraction notice to “Regional sustainable water and energy development projects: A case of Southeastern Anatolia Project (GAP) in Turkey” [Renew Sustain Energy Rev 16/2 (2011) 1146–1156](S136403211100551X)(10.1016/j.rser.2011.11.015)
Akpinar, A.; Kaygusuz, K.
This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief. The authors have plagiarized part of a paper that had already appeared in Renewable Energy, Volume 39 (2012), Pages 17–23, DOI: 10.1016/j.renene.2011.08.006. Although the authors were contacted for a reaction, we were unsuccessful in obtaining a response. One of the conditions of submission of a paper for publication is that authors declare explicitly that the paper is not under consideration for publication elsewhere. Re-use of any data should be appropriately cited. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.
- BildiriYalnız künye2017A day ahead hourly solar radiation forecasting by artificial neural networks: A case study for Trabzon province; [Yapay Sinir Aǧlari ile Gün Öncesi Saatlik Güneş Radyasyonu Tahmini: Trabzon İli Örneǧi]
Çevik, Sibel; Çakmak, Recep; Altaş, Ismail Hakki
The integration of renewable energy sources to the electrical grid leads to some issues in the grid because of intermittent and variable characteristics of renewable energy sources such as wind and solar. It has been predicted that the solar based electricity production will has highest annual increase rate among the other renewable sources. Due to the intermittent and volatile nature of the solar energy in an electricity grid where photovoltaic systems are intensive, load planning is essential. Therefore, day ahead solar radiation forecasting will contribute to the load planning studies. Artificial neural networks are one of the methods that are applied frequently and successfully in forecasting studies. In this study, a cause effect based artificial neural network (ANN) has been designed and performed for day ahead hourly solar radiation forecasting in Trabzon province. A similar day selection algorithm has been utilized to get more accurate forecasting by the ANN. The designed ANN has been trained and tested in MATLAB simulation environment without using ready codes of MATLAB ANN toolbox. The obtained results reveal that the designed ANN forecasts the solar radiation with acceptable error for a place such as Trabzon which has rainy and cloudy weather conditions.
- Kitap BölümüYalnız künye2017Green development: Case of Turkey, Norway, and China
Doğru, Bülent; Beken, Hikmet Gülçin
The focus of this chapter is to assess green or sustainable development concept because of its increased importance throughout the world. Droughts, environmental degradation, air pollution, greenhouse gas emissions are important problems that the humankind have been facing since the Industrial Revolution. Renewable energy sources can be used to overcome these problems. The general tendency of modern-day societies is to transform traditional production techniques and development models to new renewable energy sources and also move towards to sustainable development path. Therefore, this study tries to explain current status of Norway, China and Turkey in terms of their renewable energy sources and policy implementations.
- MakaleAçık Erişim2017Long term outdoor performances of three different on-grid PV arrays in central Anatolia – An extended analysis
Ozden, Talat; Akinoglu, Bulent G.; Turan, Rasit
Long term outdoor testing of the PV systems at different climatic conditions or different systems under the same ambient conditions are extremely important in producing policies for the transition to renewables. The present research is the testing of three different PV systems under the same climatic conditions of central Anatolia, after four years of operation. The systems consist of a mono-Si, an a-Si thin film and a CdTe thin film arrays. Different calculation procedures of the input solar irradiation on tilted surface are used for comparison. Performances together with degradation rates are computed using different procedures and also using the measured solar data of 20 km away from the installed systems. The accuracy is verified using 4 months of simultaneous measurements. The results showed that the aforementioned different input calculation procedures of the performances are important and determinant. The 44-months-average efficiencies of these three systems are calculated to be 11.86%, 6.40% and 5.30%, respectively. The degradation rates of these systems are obtained as 0.40%, 1.88% and 10.60%, respectively. Although the degradation rates that are calculated for the first two systems are quite similar to those appeared in the literature, CdTe system is considerably higher than those given in the literature.
- MakaleYalnız künye2016Therotical investigation of the effects of diesel fuel, biodiesel fuel and their blends on internal combsution engines
Sezer, Ismet
In this study; the effects of diesel fuel, the soybean oil methyl ester (SOME) biodiesel fuel and their blends at various percentages on the spray and combustion characteristics and engine performance and exhaust emissions of diesel engines investigated as theoretically. For this purpose, a model has been built for a direct injection diesel engine in a commercial vehicle by the Diesel-RK software program that can be used liberally on the net. The obtained values for diesel (D) and biodiesel (BD) fuels and D-BD fuel blends via the constructed model were compared. The results of the study show that BD fuel generally provides a close brake thermal efficiency values to diesel fuel. Additionally, BD fuel causes decrements in engine power and particulate matter (PM-soot) emission and increments in specific fuel consumption and nitric oxides (NOx) emission. On the other hand, D-BD fuel blends at various blend ratios have usually given the spray, combustion, performance, and emission values between those of diesel and biodiesel fuels.
- Kitap BölümüYalnız künye2016Green development: Case of Turkey, Norway, and China
Doğru, Bülent; Beken, Hikmet Gülçin
The focus of this chapter is to assess green or sustainable development concept because of its increased importance throughout the world. Droughts, environmental degradation, air pollution, greenhouse gas emissions are important problems that the humankind have been facing since the Industrial Revolution. Renewable energy sources can be used to overcome these problems. The general tendency of modern-day societies is to transform traditional production techniques and development models to new renewable energy sources and also move towards to sustainable development path. Therefore, this study tries to explain current status of Norway, China and Turkey in terms of their renewable energy sources and policy implementations.
- BildiriYalnız künye2016Scheduling of domestic shiftable loads via Cuckoo search optimization algorithm
Cakmak, Recep; Altas, Ismail H.; Cetin, A.; Camurcu, A.Y.
Electrical power systems have been developed to more advanced structures called as smart grids. Among many other issues, demand side management (DSM) is one of the important instruments of the smart grids. DSM techniques increase the efficiency of the grid, and modify consumer's electrical demand via demand response (DR) programs using financial incentives. In this study, shiftable domestic loads scheduled by Cuckoo search algorithm (CSA) to ensure balanced load curve as much as possible while considering the consumers' preferences. The main motivation of this paper is scheduling the usage hours of the shiftable household appliances in a neighborhood by applying the recently developed metaheuristic CSA. This paper proposes an approach to increase the efficiency and lifetime of utility network by scheduling and operating shiftable domestic loads while considering consumer's demand in terms of financial benefits. Proposed CSA based scheduling mechanism is compared with that of Genetic algorithm (GA). The results reveal positive effects of the scheduling and the performance of the CSA over GA.
- MakaleAçık Erişim2015Outdoor efficiency analyses and comparison of on-grid CdTe and μc-Si/a-Si thin-film PV systems for three years in Ankara - Turkey
Ozden, Talat; Yardim, Ugur; Akinoglu, Bulent G.; Turan, Rasit; Turan, R; Gunes, M; Sariciftci, NS; Varlikli, C
The present paper is mainly a comparison of the performances of two PV systems under outdoor conditions in Ankara. The systems are grid connected and consist of two PV arrays. The types of these PV arrays are CdTe thin film and amorphous silicon/micro-crystalline-based (μc-Si/a-Si) arrays. They are operated for 3 years; 2012-2014. Yearly averages of monthly efficiencies of these two systems working under the same ambient conditions are 6.88%, 6.65%, 6.80% and 6.64%, 5.86%, 5.25% for μc-Si/a-Si and CdTe, respectively. Using these values, simple calculation results for the degradation rates per year are about 0.39%/year and 6.98%/year, respectively for these two types of systems.
- MakaleYalnız künye2015Organic maturity and hydrocarbon potential of liassic coals from the eastern Pontides, NE Turkey
Eker, C.S.; Sipahi, F.; Akpnar, I.
Organic matter content, type of organic material, and thermal maturity of Lias-aged coals of the Gumushane and Bayburt areas were investigated. The total organic carbon contents of coals in the Gumushane area range from 0.39-35.46 wt%, and in the Bayburt area range from 0.02-50.64 wt%. The Gumushane (except Güvercinlik field) and Bayburt areas coals have low hydrogen index values. The coal samples contain a mixture of Type II and Type III kerogens. Based on average Tmax values Liassic coals in the Gumushane and Bayburt (except Cerci field) areas are mature, and potential yields are low.
- MakaleAçık Erişim2015A low cost outdoor testing facility for detailed photovoltaic device performance characterization
Ogulgonen, Guvenc; Ozden, Talat; Yardim, Ugur; Turan, Rasit; Kincal, Serkan; Turan, R; Gunes, M; Sariciftci, NS; Varlikli, C
Long term outdoor performance monitoring is the ultimate method to capture the long term performance characteristics of PV devices. As time consuming as this process might be, it is the only way in which the local environmental condition versus PV device characteristics may be captured when making investment decisions. This data needs to be captured at least once through the seasonal cycle. It needs to be correlated to the environmental conditions, this monitoring climatic conditions is a requirement. Solar irradiation conditions must be monitored over a range of inclination angles - direct, diffuse and reflected components must be ideally captured separately. The panels must be held at maximum power generating point through the varying illumination conditions. Periodic IV traces must be captured, in addition to the power output to understand mechanisms of degradation, if present. Furthermore, the IV curves must be summarized in terms of relevant performance metrics. This work describes an outdoor testing facility that addresses all the aforementioned requirements. Reliable equipment selections coupled with adequate modelling strategies allow for the generation of a robust and accessible database of performance data.
- MakaleYalnız künye2014Exergetic analysis of using the gaseous fuels in spark ignition engines
Sezer, Ismet; Bilgin, Atilla
This paper aims to investigate the use of alternative gaseous fuels in spark ignition engines via an exergy analysis. A quasi-dimensional two-zone thermodynamic cycle model is used for this purpose. The intake and exhaust processes are computed by a simple approximation method, and the processes (that is, compression, combustion, and expansion) are simulated in detail. The turbulent flame propagation process is used for the combustion simulation. The second law of thermodynamics is applied to the cycle model to perform the exergy analysis. The exergy transfers associated with heat, work, and exhaust; the irreversibilities, thermomechanical exergy, fuel chemical exergy, and total exergy have been computed in the exergy analysis. A distribution of the fuel exergy, the energy-based (the first law) efficiency, and the exergetic (the second law) efficiency were also calculated during the exergy analysis. Thus, the effects of using natural gas and liquefied petroleum gas on the exergetic terms and the efficiencies are investigated. The results of the study show that investigated alternative gaseous fuels have affected the variations in the exergy transfers, irreversibilities, and efficiencies. The gaseous fuels are suitable from the exergy point of view because of the lessened exergy destruction rate, but they suffer from the engine performance reduction.
- MakaleYalnız künye2013The contribution of hydropower in meeting electric energy needs: The case of Turkey
Akpinar, Adem
In this article, an attempt is made to better understand the contribution of hydropower in meeting electric energy needs of Turkey. Thus, a comparison between Turkey and other countries, which have some similarities with Turkey or which are more developed nations compared to Turkey, for evaluating from different aspects the contribution of hydropower in meeting electric energy needs is performed. The producers of electricity and hydroelectricity in the world, and the electric sectors of all the selected countries are firstly examined. Thereafter, Turkey's water resources and its potential, hydropower potential, and current status of hydropower in Turkey are investigated in detail. A detailed discussion regarding economic and energy indicators, hydroelectricity versus thermal electricity, the contributions of hydroelectricity to the total and renewable electricity generation, and the usage status of hydro potential of each selected nation is also made. Finally, it is found that hydropower is the second largest contributor in meeting Turkey's electric energy needs after thermal, mainly natural gas. It is also estimated that the contribution of hydropower will continue because a vast amount of its economically feasible hydro potential (about 64%) is undeveloped. Besides, it is determined that the contribution of hydropower in the total electricity generation in Turkey is greater than that of China and India, but it is lower than that of Norway, Brazil, and Canada.
- MakaleYalnız künye2013Evaluation of wind energy potentiality at coastal locations along the north eastern coasts of Turkey
Akpinar, Adem
This study aims to determine and evaluate wind energy potentiality along coastal locations at the North Eastern of Turkey. For this purpose, the present study has statistically analysed wind power potentials and wind characteristics from six meteorological stations (Sinop, Samsun, Ordu, Giresun, Trabzon, and Hopa) along the North Eastern (NE) geo-political coastal region of Turkey using the hourly or 3-hourly wind speed data measured at 10 m height during 9 years. The diurnal, monthly, and seasonal mean wind speed and wind power density at all the stations are assessed to have remarkable variations. The annual and seasonal frequency distributions and dominant wind directions of the all locations are determined. It is observed that the monthly mean wind speed in this region ranges from 1.53 m/s to 4.06 m/s. The maximum annual mean wind power density was found to be 59.96 W/m2 at Sinop while the maximum annual mean wind energy density was obtained to be 525.25 kWh/m2/year at the same station. It is further shown that Sinop, Hopa, and Trabzon have the higher wind power potential than other locations and their potential are close to each other.
- MakaleYalnız künye2013Effects of charge properties on exergy balance in spark ignition engines
Sezer, Ismet; Bilgin, Atilla
This study investigates the effects of the air-fuel mixture (charge) properties on the exergy balance in spark ignition engines. A thermodynamic cycle model including compression, combustion and expansion processes is used. The principles of the second law are applied to the cycle model to perform an exergy analysis. Variation of the exergetic variables during the investigated portion of the cycle are examined as a function of the charge properties, i.e., fuel-air equivalence ratio, residual gas fraction and initial charge temperature. The results show that increasing fuel-air equivalence ratio causes an increase in irreversibilities and also exergy losses with heat transfer and exhaust gases, but enriching the air-fuel mixture beyond the stoichiometric ratio makes no significant contribution to the exergy transfer with work transfer. A slightly lean mixture also gives the best first and second law efficiencies. It is observed that there is a linear relation between the residual gas fraction and the exergetic variables. An increase in the residual gas fraction decreases the irreversibilities and exergy losses aside from the exergy transfer with work transfer. However, increasing the residual gas fraction positively affects the first and second law efficiencies because of the diluting of the charge. Increase of initial charge temperature creates a reduction in the irreversibilities and the exergy losses and, it also results in a lower exergy output by work transfer. Further, increase of initial charge temperature negatively influences the first and second law efficiencies.
- MakaleYalnız künye2013Assessment of wave energy resource of the Black Sea based on 15-year numerical hindcast data
Akpinar, Adem; Kömürcü, Murat I.hsan
In this study, the existence and variability of wave energy resource potential of the Black Sea based on 15-year hindcast data is described in detail. The hindcasts of wave parameters were carried out by using the third generation wave prediction model (Simulated WAves Nearshore - SWAN), which is one of the most popular numerical wave models and has been widely used for estimating ocean waves. The model was forced with the ECMWF ERA Interim wind fields and applied with a spatial resolution of about 0.0167°. ×. 0.0167° and a model time step of 6. h to resolve efficiently offshore and nearshore wave conditions. The results were presented in the form of charts of the spatial distribution of significant wave height and wave power, on a monthly, seasonal and annual basis. Annual energy was calculated in the study region with the hindcast data set covering 15. years (1995-2009). The areas with the highest wave energy resource were determined and the south west coasts of the Black Sea are suggested as the best site for the installation of a wave farm. It was determined the western parts of the Black Sea (especially the south-west) are exposed to energetic waves more than the eastern parts.
- BildiriYalnız künye2013The effect of integration types on FLC based MPPT systems
Cakmak, Recep; Altas, Ismail H.
Operating the photovoltaic (PV) array at its maximum power available is important to increase system efficiency. In order to operate PV systems at their maximum power point, many maximum power point tracking (MPPT) methods have been proposed. Fuzzy logic controller (FLC) based MPPT methods have some advantages over classical MPPT methods. The way of using the FLC outputs has an effective role in obtaining the desired results. In this study, the effect of a discrete-time integration method investigated in MPPT including FLC whose output is subjected to integration operation. The system has been designed and simulated in MATLAB/Simulink software. The results were given as a comparison.
- Derleme MakaleYalnız künye2012RETRACTED: Regional sustainable water and energy development projects: A case of Southeastern Anatolia Project (GAP) in Turkey (Retracted article. See vol. 83, pg. 173, 2018)
Akpinar, A.; Kaygusuz, K.
Southeastern Anatolia Project (GAP) region in Turkey is rich in water for irrigation and hydroelectric power. The Euphrates and Tigris Rivers represent over 28% of the nation's water supply by rivers, and the economically irrigable areas in the region make up 20% of those for the entry country. Turkey has a total gross hydropower potential of 433 GWh/yr, but only 125 GWh/yr of the total hydroelectric potential of Turkey can be economically used. By the construction of new hydropower plants, 36% of the economically usable potential of the country would be tapped. The GAP region has a 22% share of the country's total hydroelectric potential, with plans for 22 dams and 19 hydroelectric power plants. Once completed, 27 billion kWh of electricity will be generated annually. (C) 2011 Elsevier Ltd. All rights reserved.
