Yazarlar
- Kankal, Murat(17)
- Şan, Murat(17)
- Akinoglu, Bulent G.(14)
- Ozden, Talat(14)
- Nacar, Sinan(10)
- Barut, Abdulkadir(9)
- Akpinar, Adem(6)
- Akyol, Mehmet(6)
- Akçay, Fatma(6)
- Cakir, Mehmet Ali(6)
- Pilatin, Abdulmuttalip(6)
- Sezer, İsmet(6)
- Terhan, Meryem(6)
- Özden, Talat(6)
- Işık, Fatih(5)
- Kömürcü, Murat Ihsan(5)
- Pala, Fahrettin(5)
- Turan, Rasit(5)
- Akyol, Hikmet(4)
- Artan, Seyfettin(4)
- Hayaloğlu, Pınar(4)
- Peker, Iskender(4)
- Sezer, Ismet(4)
- Özbek, Adem(4)
- Adali, Zafer(3)
- Akpinar, A.(3)
- Akpinar, Muhammet Vefa(3)
- Altuner, Elif Esra(3)
- Ayaydın, Hasan(3)
- Başoğlu, Mustafa Engin(3)
- Bilgic, Abdulbaki(3)
- Bozbeyoglu, Pinar(3)
- Coruh, Emine(3)
- Eraslan, Selim(3)
- Erol, Ismail(3)
- Kaygusuz, Abdullah(3)
- Kaygusuz, Kamil(3)
- Mete, Emrullah(3)
- Nizetic, S(3)
- Okkan, Umut(3)
Yayınlar
- MakaleAçık Erişim2020The Effect of Energy Consumption on Agricultural Added Value: Panel Data Analysis for EU Member Transition Economies
Akyol, Mehmet
Energy plays an important role in maintaining vital activities. Like other sectors, with the developing technology, energy is used in agricultural activities. Therapid and uncontrolled increase in energy consumption in agricultural production,has sometimes led to a decrease in the efficiency of the energy use. Inefficient use of energy, which is a production input, leads to an increase in production costs. The increase in production costs leads to a relative decrease in output and such negativities exposing producers to loss of income.. Within the framework of the analysis, 10 countries who are called as transition economies and EU member as wellwere included in the study. Dynamic panel data method was used in the study which analyzed the period between 2009-2017. As a result of the analysis, it was observed that agricultural energy consumption had a positive effect on agricultural value added.
- MakaleAçık Erişim2020Karadere Çayı Taşkını (Araklı -Trabzon)
Işık, Fatih; Zeybek, Halil İbrahim; Çağlak, Savaş; Bahadir, Muhammet
Taşkınlar ülkemizde son yıllarda değişen iklim şartları ile birlikte daha sık yaşanan doğal afetlerdir. Taşkınlara bağlı olarak birçok can ve mal kaybı yaşanmaktadır. Bu çalışmada taşkınların çok yaşandığı Doğu Karadeniz Bölümü’nde yer alan Trabzon’a bağlı Araklı ilçesinde 18 Haziran 2019 tarihinde meydana gelen taşkının coğrafi nedenleri incelenmiştir. Oluşan taşkın, Araklı ilçesine bağlı Çamlıktepe ve Yüceyurt mahallelerinde 10 kişinin yaşamını yitirmesine, çok sayıda meskenin de yıkılmasına sebep olmuştur. Taşkının yaşandığı Karadere Çayı havzasında yaşanması muhtemel taşkınların risk analizi yapılarak taşkına duyarlı alanlar belirlenmiştir. Çalışmada sahaya yönelik afet raporları, sayısal yükseklik, meteorolojik, akım ve jeolojik verilerden yararlanılmıştır. Çalışmada yöntem olarak Çok Kriterli Karar Verme yönteminin bir metodu olan Analitik Hiyerarşi Süreci kullanılmıştır. Taşkın duyarlılık analizi için mevcut yöntemlere farklı parametreler eklenerek oluşturulan üç ayrı teknik ile haritalar üretilmiştir. Analiz sonuçlarına göre, Karadere Çayı’nın bazı kıyı kesimleri, Haliloğlu ve Gülbekli derelerinin birleştiği yer ve Araklı şehir merkezi taşkına en duyarlı alanlar olarak tespit edilmiştir. Haliloğlu ve Gülbekli derelerinin birleştiği saha 18 Haziran 2019’da yaşanan taşkının ana merkezini oluşturmaktadır. Ayrıca sahada taşkınla birlikte yaşanan heyelan olayları da taşkının etki derecesini artırmış, çamur akıntısı oluşumuna neden olmuştur. Analiz sonuçları ve yaşananlar göstermektedir ki sahada bundan sonrada taşkın olasılığı yüksektir. Bu nedenle çalışmanın, yöneticiler ve karar vericiler tarafından muhtemel olumsuz sonuçların engellenmesi adına dikkate alınması beklenmektedir.
- MakaleAçık Erişim2020One-year performance evaluation of two newly developed back-contact solar modules in two different climates
Ozden, Talat; Carr, Anna J.; Geerligs, Bart (L.J.); Turan, Rasit; Akinoglu, Bulent G.
To a certain extent, the photovoltaics industry is well developed, and the performance and expected yield of standard photovoltaic modules are well documented and researched. However, newer more efficient photovoltaic cell and module technologies are being developed all over the world. Outdoor testing of new photovoltaic technologies is very important to understand and validate their reliability and performance under different environmental conditions. For the first time, one year of monitored performance data is presented and analyzed for two high efficiencies interdigitated back contact prototype mini-modules at different locations, having different climates. The test results of a commercial heterojunction with intrinsic thin-layer” module are also presented for comparison. The results showed that the two mini-modules remained stable for the duration of the test period, and showed no signs of degradation. They did perform significantly differently due to the different climatic conditions. The results also show that the combination of ambient temperature difference together with relative humidity impacts the performance of the modules. Calculated outdoor yearly efficiencies are 19.05% and 18.36% for two integrated back contact mini-modules tested in Petten-Netherland and Ankara-Turkey, respectively. The temperature coefficients of the modules are also calculated and compared with two commercial photovoltaic modules.
- MakaleAçık Erişim2020Effects of elevation on the aboveground biomass and carbon stock in the oriental beech (Fagus orientalis lipsky) forests of the Sinop region, Turkey
Kahyaoğlu, N.; Kara, Ö.; Güvendi, E.
In this study it was our aim to assess the amount of aboveground biomass and carbon stock of beech stands based on elevation. To achieve this, in the research area, 55 trial sites were chosen by selective sampling method depending on elevation climatic zones (400–600 m, 600–800 m, 800–1000 m). In these trial areas, 55 trees were cut down and the weights of their bark, leaves, stem and branches were determined. The carbon content of each component was calculated. The results of the study showed that, in all elevation zones, the stem wood had the highest average biomass and carbon stock values of all the tree components (for the 400–600 m, biomass was 199.19 kg and carbon stock was 95.82 kg; for the 600–800 m, biomass was 378.75 kg and carbon stock was 182.49 kg; for the 800–1000 m, biomass was 372.56 kg and carbon stock was 183.39 kg). This was followed by the branches, bark and leaves in descending order. The aboveground biomass in the single tree components of leaves, branches, stem and total biomass, all except the biomass of their bark varied with elevation in oriental beech stands, which are economically significant species in Turkey.
- MakaleAçık Erişim2020Historical aurora borealis catalog for Anatolia and Constantinople (hABcAC) during the Eastern Roman Empire period: Implications for past solar activity
Maden, Nafiz
Herein, Anatolian aurorae are reviewed based on the existing catalogs to establish a relationship between the aurora observations and past solar activity during the Medieval period. For this purpose, historical aurora catalogs for Constantinople and Anatolia are compiled based on the existing catalogs and compared with those in the Middle East region. The available catalogs in the literature are mostly related to the records observed in Europe, Japan, China, Russia, and the Middle East. There is no study dealing only with the historical aurora observations recorded in Anatolia and Constantinople. The data of the catalog show that there is a considerable relationship between the aurora activity and past strong solar activity. High auroral activity around the extreme solar particle storm in 774/775 and the Medieval grand maximum in the 1100s in Anatolia and the Middle East is quite consistent with the past solar variability reported in other scientific literature.
- BildiriYalnız künye2020Nine Years Long Term Performance and Degradation Assessment of Two On-Grid PV Systems
Ozden, Talat; Ozgun, Ensar Mesut; Keles, Bedirhan; Akinoglu, Bulent G.
Nine years outdoor testing of the two on-grid PV systems at Central Anatolia under the same ambient conditions is very important to be discovered toward transition to renewables. The systems consist of a monocrystalline silicon and micro-crystalline silicon based amorphous thin film PV technologies. The analyses are carried out on monthly based using the outdoor efficiencies. In addition, degradation rates of these systems are calculated and compared with each other and also with international literature. It is also compared the results using the degradation rates of an earlier study carried out using measurements of a shorter period of time.
- MakaleAçık Erişim2020AN EXTENDED ANALYSIS OF THE MODELS TO ESTIMATE PHOTOVOLTAIC MODULE TEMPERATURE
Ozden, Talat; Tolgay, Doga; Yakut, M. Samet; Akinoglu, Bulent G.
To estimate the performance of the photovoltaic power systems is the key issue in their techno-economic feasibility analysis. Performances, on the other hand, strongly depends on the module temperatures of the photovoltaic systems. In this study, we evaluated the performance of ten different module temperature estimation models using the measured outdoor data of five different modules. The modules are installed at the rooftop of a building located at Central Anatolia where the climate is cold and semi-arid. The results showed that the models having smaller number of parameters perform better than the others. We concluded that such analysis should be carried out at different ambient conditions so that the best performing models for the site can be obtained. Another outcome of the study is that the seasonal evaluation of the performance of the models should be carried out.
- MakaleAçık Erişim2020Forest Biodiversity, Carbon Sequestration, and Wood Production: Modeling Synergies and Trade-Offs for Ten Forest Landscapes Across Europe
Biber, Peter; Felton, Adam; Nieuwenhuis, Maarten; Lindbladh, Matts; Black, Kevin; Bahyl, Jan; Bingöl, Ozkan; Borges, Jose G.; Botequim, Brigite; Brukas, Vilis
Europe's forests provide vital habitat for biodiversity and essential ecosystem services whose provision must be sustained or enhanced over the coming century. However, the potential to secure or increase forest ecosystem services, while securing the habitat requirements of taxa remains unclear, especially within the context of uncertain climate and socio-economic developments. To tease out the associated trade-offs and synergies, we used 10 case study landscapes within nine countries throughout Europe. Starting with the current status of the forests in the case study landscapes, we simulated forest development 100 years into the future. Simulations were embedded in three combined climate and socio-economic frame scenarios based on global and European policies which varied in their climate change mitigation efficiency. Scenarios were translated into country specific projections of climate variables, and resultant demands for wood products. Forest management regimes were projected to vary in response to these scenarios at local scales. The specific combinations of alternative forest management practices were based on parallel research and input from local forest stakeholders. For each case study, a specific forest growth simulator was used. In general, the climate scenarios applied did not cause fundamentally different ecosystem service outputs at the case study level. Our results revealed almost no reduction in outcomes for biodiversity indicators with an increase in wood production, and in some cases synergistic results occurred when diversity was actively promoted as part of the management concept. Net carbon uptake was not strongly correlated with biodiversity, indicating that biodiversity-friendly forest management doesn't need to curtail carbon sequestration. Notably, we obtained heterogeneous results for the relation between sustainable wood production and net carbon uptake. Most scenarios resulted in a more or less reduced net carbon uptake over the long term, often due to stand age class distribution shifts. Levels of sustainable wood production varied widely during the simulation period, from significant increases (Sweden, Lithuania) to minor changes (Slovakia, Turkey) and slight decreases (Ireland, Netherlands). We place our results within the larger context of European forest policy and the challenges of simulating and contrasting forest biodiversity and the ecosystem services that societies depend on.
- MakaleAçık Erişim2020Dynamic thermal modelling of PV performance and effect of heat capacity on the module temperature
Tuncel, B.; Ozden, T.; Balog, R. S.; Akinoglu, B. G.
One of the main weaknesses of Si-based Photovoltaic (PV) solar modules is the sensitivity of their efficiency to module (cell) temperature. Especially in locations with long hot seasons, the efficiency loss of PVs due to high temperatures should be considered carefully. Thermal modelling is a method to predict the performance of a PV module using essentially the 1st law of thermodynamics and available data. In this paper, a transient thermal model is described, which considers hourly meteorological data, including wind speed and direction, module parameters, and locational information. In transient analysis, the heat capacity value of PV panel is required, but it is not a parameter specified in the manufacturer's datasheet. Experiments on the heat capacity of PV modules are missing in the literature. The thermal model provides verified performance analysis for a poly-c-Si PV module installed in Ankara, Turkey, with a calculated heat capacity value. And a sensitivity analysis for the heat capacity of the transient thermal model is performed. It is found that the model results are almost invariant under changing module heat capacity values.
- Derleme MakaleAçık Erişim2019A Review Study on the Using of Diethyl Ether in Diesel Engines: Effects on CO2 Emissions
Sezer, İsmet
Vehicle and other fuel combustion emissions can change the composition of the atmosphere, increasing its ability to trap heat. Gases that are effective in trapping heat are called greenhouse gases and include all of the gases in vehicle emissions. The major component of greenhouse gases emissions is carbon dioxide (CO2). Reduction of CO2 emissions has become a concern worldwide. Introduction of biofuels to fueling of automotive engines is the one method to decrease emissions of greenhouse gases. The CO2 from biofuels, is emitted during combustion and absorbed during growth of tree end plants. These biofuels can be applied as blends or sole fuels. The most researches declare that the best way to reduce greenhouse emissions is the use of various biofuels. Therefore, it is very important that the results of various studies on alternative fuels or fuel additives are evaluated together to practice applications. On the other hand, diesel cars are also helping to reduce CO2 emissions. For these reasons, this study especially focuses 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 CO2 emissions.
- BildiriYalnız künye2019Design of a MATLAB GUI for Day Ahead Forecasting of PV Panel Power
Bektas, Sibel Cevik; Cakmak, Recep; Altas, Ismail H.
This paper introduces design and utilization of a MATLAB graphical user interface (GUI) platform to forecast day ahead hourly Photovoltaic (PV) panel power by using forecasted day ahead global horizontal solar radiation. This platform, which would be a useful and practical tool for researchers who are study on energy management, planning and forecasting studies, consists of three parts. The first part predicts day ahead global horizontal solar radiation by trained artificial neural network (ANN) model. The second part performs the calculation of solar irradiation on the module, which has a tilted angle according to forecasting solar radiation data. The last part estimates the power generated by PV panel according to the calculated incident radiation. In this study, the solar irradiation forecasting, the calculation of incident radiation to tilted module and prediction of the solar power to be generated by the PV module are done. The designed GUI has been utilized to forecast solar radiation and PV output power for test days. Then obtained forecasted data have been evaluated with mean absolute percentage error (MAPE) and correlation coefficient (R).
- MakaleAçık Erişim2019The impact of economic globalization on CO2 emissions: The case of NAFTA countries
Kalaycı, Cemalettin; Hayaloğlu, Pınar
International trade with the economic globalization gaining wide currency has brought along the environmental problems. Transition to environment-friendly high-tech products and schemes in developed countries alleviated the impacts of these problems whereas underdeveloped environmental standards in developing countries still cause deterioration in the environmental quality. For this reason, there are different views on the environmental impacts of globalization. The study investigates the impact of globalization and trade openness on CO2 emissions with reference to the NAFTA countries. Employing panel-data analysis, the study relies on the annual data for a period of 1990–2015. The findings reveal that there is a positive relationship between economic globalization and trade openness, and CO2 emissions. The study further tests the validity of Environmental Kuznets Curve for the target countries. To this end, the research identifies a positive-direction relationship in both linear and square forms between CO2 emissions and economic growth.
- MakaleYalnız künye2018CO2 emisyonu- enerji tüketimi ve ekonomik büyüme arasındaki nedensellik ilişkisi: G7 ülkeleri üzerine ekonometrik bir analiz
Polat, Melike Atay; Özkök, Canan Sancar
Günümüzde çevre kirliliğinin artan boyutlara ulaşması ve küresel ısınmanın olumsuz etkilerinin hafifletilmesi yönündeki çabalar CO2 salınımına neden olan enerji kaynaklarının kullanımı sorununu gündeme getirmiştir. Ekonomik büyüme ve daha ileriki bir aşama olan ekonomik kalkınma enerji kaynaklarının kullanımını hızlandırır. Bu süreç enerji rezervlerinin tükenmesi yanında CO2 emisyonu düzeyinde de artışa neden olur. Bu nedenle de CO2 emisyonunun azalması, enerji tasarrufu sağlanması ve ekonomik performansın ayarlanması açısından bu üç değişkenin optimal düzeyinin birlikte formüle edilmesi gerektirmektedir. Bu çalışmada, G7 ülkelerinde CO2 emisyonu, enerji tüketimi ve ekonomik büyüme arasında ilişki olup olmadığını araştırılmıştır. Bu amaçla, G7 ülkelerinin 1980-2011 dönemi verileri kullanılarak panel birim kök, panel eş bütünleşme ve panel nedensellik testleri kullanılmıştır. Birim kök testi sonuçlarına göre düzeyde durağan olmayan değişkenler uzun dönemde eş bütünleşiktir. Çalışmanın panel nedensellik testi sonuçları, G7 ülkelerinde CO2 emisyonu ile GSYH ve enerji tüketimi ile GSYH arasında çift yönlü nedensellik ilişkisi olduğunu göstermiştir. Bu çalışmanın sonuçları politika yapıcılar için G7 ülkelerinde enerji verimliliğindeki artışın teknolojik açıdan önceliklendirilmesini ve çevre dostu politikalarda ortak hareket planları uygulamalarını öncelikli kılmaktadır.
- BildiriYalnız künye2018Reducing Urban Heat Islands by Developing Cool Pavements
Akpinar, Muhammet Vefa; Sevin, Sedat; Nizetic, S; Papadopoulos, A
- BildiriYalnız künye2018Comparison of Asphalt and Concrete Pavement Solar Reflectance
Akpinar, Muhammet Vefa; Sevin, Sedat; Nizetic, S; Papadopoulos, A
- BildiriYalnız künye2018Urban Heat Island Effects of Concrete Road and Asphalt Pavement Roads
Akpinar, Muhammet Vefa; Sevin, Sedat; Nizetic, S; Papadopoulos, A
- BildiriAçık Erişim2018Thermal modeling and verification of pv module temperature and energy yield using outdoor measurements for Ankara, Turkey
Tuncel, Bilge; Akinoglu, Bulent G.; Ozden, Talat; Balog, Robert S.
Ankara is in the Central Anatolia region of Turkey where the climate is dry-continental with an annual solar insolation of around 1750 kWh/m 2 . In the transition to renewable energy, detailed analyses are required to ensure effective and economic utilization of the available solar resource. An essential part of these analyses is to calculate expected energy yield. For photovoltaic (PV) systems, this includes the effect of temperature on the PV efficiency, which determines the power yield of the PV modules. In this study, a first-principles thermal modeling approach is improved by adding the speed and direction of wind across the PV module into a forced convection term as well as including the temperature dependency of the module conversion efficiency. The analytical model is based on the principle of conservation of energy and uses meteorological data that are readily available from most state meteorological services. The mathematical analysis is suitable to predict the performance of a proposed PV installation without the time and expense of installing and monitoring a pilot system. The mathematical model is compared against measured data from the METU-GUNAM Outdoor Test Facility in Ankara to validate the methodology. Preliminary analyses showed that the model performs well especially during sunrise and sunsets shoulders of the diurnal cycle with a deviation of only a few W/m 2 for the electrical power yield and about 2°C for the module temperature. However, these deviations could become as large as 12 W/m 2 and 8°C at solar noon which suggests that the model still requires further improvement. In general, this error was found to be less that obtained by using basic explicit correlation methods and offers the advantage that it can be used for other geographical environments for which insolation and meteorological data is available without needing to construct a test-site.
- BildiriAçık Erişim2018Performance and degradation analyses of two different pv modules in central anatolia
Ozden, Talat; Akinoglu, Bulent G.; Kurtz, Sarah
Ankara (latitude: around 40°N) is in Central Anatolia and the climate is dry continental. Due to the rapid transition to renewable energy policies of Turkey it is now a must to complete truthful feasibility analyses for solar power systems countrywide. Long term performance and degradation analyses have been carried out by the authors for three different arrays and many research results appearing in the literature are summarized. Present research analyzes the outdoor testing results of two PV modules monthly data. One of the modules has multi crystalline silicon (Poly-Si) cells and the other is thin film silicon (amorphous Si / microcrystalline Si tandem structure - a-Si/μc-Si) cells. The results showed that in five years the average yearly efficiency decreases from 14% to 11% for Poly-Si (14.72% is the nameplate Standard Test Condition (STC) efficiency) and from 8% to 6% for thin film modules (9.15% is STC efficiency). Our calculations are based on measured solar global-horizontal irradiance from which we calculated plane-of-array irradiation using an anisotropic sky model. We present the details of these analyses and degradation rates for the two types of modules to be used in long term feasibility analyses.
- BildiriAçık Erişim2018Daily and monthly module temperature variation for 9 different modules
Özden, Talat; Tolgay, Doga; Akinoglu, Bulent G.
One of the main parameter affecting the efficiency of PV modules is the module temperature. In this respect, outdoor testing of modules is very important to determine the temperature dependent performances and degradation rates. In this work, we analyzed the module temperatures of 9 different modules tested in the outdoor testing facility of METU-GUNAM, Ankara (latitude ∼40°N, in Central Anatolia and the climate is dry continental). The tested module types are two CIS (identical), one μc-Si/a-Si, one Poly-Si, three Mono-Si (two identical), one HIT and one bifacial. The module temperatures can reach up to 76°C while the ambient is around 39 °C during summer days. Monthly average module temperatures can reach up to 33.7°C (CIS) while the monthly average ambient is at 26.0°C and drops down to 1 °C while average ambient temperature is about the same as average module temperature. The results showed that the monthly averages of module temperatures differences are maximum during summer (∼3.5°C) and minimum during winter (1.1°C). It is interesting that the two CIS modules have the highest monthly average module temperature and although they are supposed to be identical their temperatures differ significantly. Bifacial and HIT module temperatures are lower than the Mono-Si modules. One of the two identical Mono-Si modules was not cleaned and its module temperature is always lower than the one that was cleaned periodically, as expected. In this work, we also present the results and discussions on the spatial variations of measured module temperatures of PV panels.
- BildiriYalnız künye2018On the Yearly Performance of a Bifacial PV Module in Central Anatolia - Turkey
Özden, Talat; Turan, Raşit; Aklnoǧlu, Bülent Gültekin; Zaz, Y.; Essaaidi, M.
With the tremendous increase in the photovoltaic (PV) power plants world-wide remarkable decreases in their installation prices per watt are attained mainly due to economic scale effect. This brings questioning to increase their energy yields by considering any possible way like fabricating bifacial solar modules. Present study is on the performance analysis of a bifacial PV module using one-year outdoor testing results in Ankara-Turkey. The module performed very well and reached a specific yield value of 1750 kWh/kWp. This value for Central Anatolia region is well above the values predicted (and suggested) by the local authorities. The efficiency and performance ratio variation with respect to ambient and module temperature are obtained. The calculated dependence of efficiency on the module temperature is found to be η=-0.073Tmod+18.05, and the maximum measured module temperature is about 70 °C. The results show that the bifacial modules have the potential to replace the mono facial modules that are now dominating the PV market.
