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Öğe Assessing monthly average solar radiation models: a comparative case study in Turkey(Springer, 2011) Sonmete, Mehmet H.; Ertekin, Can; Mengeş, Hakan O.; Hacıseferoğulları, Haydar; Evrendilek, FatihSolar radiation data are required by solar engineers, architects, agriculturists, and hydrologists for many applications such as solar heating, cooking, drying, and interior illumination of buildings. In order to achieve this, numerous empirical models have been developed all over the world to predict solar radiation. The main objective of this study is to examine and compare 147 solar radiation models available in the literature for the prediction of monthly solar radiation at Ankara (Turkey) based on selected statistical measures such as percentage error, mean percentage error, root mean square error, mean bias error, and correlation coefficient. Our results showed that Ball et al. (Agron J 96:391-397, 2004) model and Chen et al. (Energy Convers Manag 47:2859-2866, 2006) model performed best in the estimation of solar radiation on a horizontal surface for Ankara.Öğe Assessing solar radiation models using multiple variables over Turkey(Springer, 2008) Evrendilek, Fatih; Ertekin, CanSolar radiation drives many environmental processes; however, needs to be estimated indirectly from more commonly measured meteorological variables since these data are not readily available from most climate stations. A geo-referenced dataset from 159 climate stations of 17 variables (maximum possible sunshine duration, mean, minimum and maximum air temperature, soil temperature, mean and maximum relative humidity, precipitation, cloudiness, evapotranspiration, extraterrestrial radiation, day length, declination angle, day of the year, latitude, longitude, and altitude) was used to model spatio-temporal dynamics of solar radiation over Turkey. A total of 78 empirical models of different mathematical functions with a different combination of 17 explanatory variables were compared based on the error statistics of the Jackknifing validation. The empirical models had adjusted coefficient of determination (R(adj)(2)) values of 22.7-96.5% based on the parameterization dataset (P < 0.05). Models 46 and 22.2 provided the most robust performance and were identified as generic models for the estimation of monthly changes in solar radiation over topographically complex terrain of the entire Turkey as a function of maximum possible sunshine hours, extraterrestrial solar radiation, mean temperature, and precipitation. The quadratic and cubic models performed best in terms of the error statistics (P > 0.05), while the performance of the hybrid models was worse than that of the linear, quadratic and cubic models in terms of maximum relative percentage error (e) (P < 0.01). In comparing the interpolation methods of inverse distance weighting and universal co-kriging, anisotropic spherical semi-variogram model of universal co-kriging was found to provide the best description of spatial autocorrelation and variability latent in these data based on the spatial leave-one-out cross-validation.Öğe Emissions Of greenhouse gases from diesel consumption in agricultural production of Turkey(European Center Sustainable Development, 2016) Aday, Beran; Ertekin, Can; Evrendilek, FatihAgricultural sector is both energy consumer in the form of human labor, fossil fuels, electricity, seeds, fertilizer, and pesticides and energy producer in the form of food, feed, and biofuels. High agricultural use of energy inputs results in adverse environmental issues such as global climate change, pollution of water, soil and air, and unsustainable agricultural production. In this study, 35 agricultural crops such as cereals, fruits, and vegetables were evaluated in terms of consumption of diesel fuel during their production process including soil preparation, fertilization, sowing, spraying, harvesting and transportation, based on minimum and maximum values reported in related literature. Greenhouse gas (GHG) emissions from diesel consumption can be expressed as total carbon dioxide equivalent (CO2eq) emissions (2.76 kg per liter). a map showing total CO2eq emissions from diesel consumption for agricultural production. Our estimates showed that minimum and maximum GHG emissions varied between 0.48 and 3.75 Tg CO2eq for wheat, 17.15 and 65.45 Gg CO2eq for chickpea, and 0.088 and 0.153 Tg CO2eq for tomatoes, respectively. In order to reduce diesel-related GHG emissions, there is an urgent need for innovative agricultural practices and technologies to be put into place.Öğe Long-term spatiotemporal patterns of CH4 and N2O emissions from livestock and poultry production in Turkey(Springer, 2010) Külcü, Recep; Ekinci, Kamil; Evrendilek, Fatih; Ertekin, CanThis study quantified spatiotemporal patterns of CH4 and N2O emissions from livestock and poultry production in Turkey between 1961 and 2007. CH4(enteric) (from enteric fermentation), CH4(manure) (from manure management), and N2O(AWM) (from animal waste management) emissions in Turkey were estimated at 1,164, 216, and 55 Gg in 1961 and decreased to 844, 187, and 39 Gg in 2007, contributing a share of roughly 2% to the global livestock-related CH4 emissions and %1.5 to the global N2O(AWM) emissions, respectively. Total CO2-eq emissions were estimated at 50.7 Tg in 1961 and declined from a maximum value of 60.7 Tg in 1982 to a minimum value of 34.5 Tg in 2003, with a mean emission rate of 48 Tg year (-aEuro parts per thousand 1) due to a significant reduction in the number of ruminant livestock. The highest mean share of emissions belonged to West Black Sea (14% and 16%) for CH4(enteric) and CH4(manure) and to North East Anatolia (12% and %13) for N2O(AWM) and total CO2-eq emissions, respectively. The highest emission density was 1.7 Mg km (-aEuro parts per thousand 2) year (-aEuro parts per thousand 1) for CH4(enteric), 0.3 Mg km (-aEuro parts per thousand 2) year (-aEuro parts per thousand 1) for CH4(manure), and 0.07 Mg km (-aEuro parts per thousand 2) year (-aEuro parts per thousand 1) for the total CO2-eq emissions in the West and North East Anatolia regions and 0.09 Mg km (-aEuro parts per thousand 2) year (-aEuro parts per thousand 1) for N2O(AWM) in the East Marmara region. Temporal and spatial variations in CH4(enteric), CH4(manure), and N2O(AWM) emissions in Turkey were estimated using regression models and ordinary kriging at a 500-m resolution, respectively.Öğe Modeling potential distribution and carbon dynamics of natural terrestrial ecosystems : a case study of Turkey(Mdpi, 2007) Evrendilek, Fatih; Berberoğlu, Süha; Gülbeyaz, Önder; Ertekin, CanWe derived a simple model that relates the classification of biogeoclimate zones, (co) existence and fractional coverage of plant functional types (PFTs), and patterns of ecosystem carbon (C) stocks to long-term average values of biogeoclimatic indices in a time-and space-varying fashion from climate-vegetation equilibrium models. Proposed Dynamic Ecosystem Classification and Productivity (DECP) model is based on the spatial interpolation of annual biogeoclimatic variables through multiple linear regression (MLR) models and inverse distance weighting (IDW) and was applied to the entire Turkey of 780,595 km(2) on a 500 m x 500 m grid resolution. Estimated total net primary production (TNPP) values of mutually exclusive PFTs ranged from 108 +/- 26 to 891 +/- 207 Tg C yr(-1) under the optimal conditions and from 16 +/- 7 to 58 +/- 23 Tg C yr(-1) under the growthlimiting conditions for all the natural ecosystems in Turkey. Total NPP values of coexisting PFTs ranged from 178 +/- 36 to 1231 +/- 253 Tg C yr(-1) under the optimal conditions and from 23 +/- 8 to 92 +/- 31 Tg C yr(-1) under the growth-limiting conditions. The national steady state soil organic carbon (SOC) storage in the surface one meter of soil was estimated to range from 7.5 +/- 1.8 to 36.7 +/- 7.8 Pg C yr(-1) under the optimal conditions and from 1.3 +/- 0.7 to 5.8 +/- 2.6 Pg C yr(-1) under the limiting conditions, with the national range of 1.3 to 36.7 Pg C elucidating 0.1% and 2.8% of the global SOC value (1272.4 Pg C), respectively. Our comparisons with literature compilations indicate that estimated patterns of biogeoclimate zones, PFTs, TNPP and SOC storage by the DECP model agree reasonably well with measurements from field and remotely sensed data.Öğe Modeling spatio-temporal dynamics of optimum tilt angles for solar collectors in Turkey(Mdpi Ag, 2008) Ertekin, Can; Evrendilek, Fatih; Külcü, RecepQuantifying spatial and temporal variations in optimal tilt angle of a solar collector relative to a horizontal position assists in maximizing its performance for energy collection depending on changes in time and space. In this study, optimal tilt angles were quantified for solar collectors based on the monthly global and diffuse solar radiation on a horizontal surface across Turkey. The dataset of monthly average daily global solar radiation was obtained from 158 places, and monthly diffuse radiation data were estimated using an empirical model in the related literature. Our results showed that high tilt angles during the autumn (September to November) and winter (December to February) and low tilt angles during the summer (March to August) enabled the solar collector surface to absorb the maximum amount of solar radiation. Monthly optimum tilt angles were estimated devising a sinusoidal function of latitude and day of the year, and their validation resulted in a high R-2 value of 98.8%, with root mean square error (RMSE) of 2.06 degrees..Öğe Quantifying spatio-temporal dynamics of solar radiation exergy over Turkey(Pergamon-Elsevier Science Ltd, 2010) Alta, D.; Ertekin, Can; Evrendilek, FatihThe insensitivity to energy quality is one of the disadvantages of an energy analysis when compared to an exergy analysis. It is only the exergy analysis that clearly reveals the degradation of energy quality in the processes of absorption and emission of solar radiation. The national spatial distribution of mean monthly exergy values of solar radiation over Turkey was mapped at 500-m resolution using universal kriging based on solar radiation data from 152 geo-referenced locations. Mean exergy value of solar radiation in Turkey was estimated at 13.5 +/- 1.74MJm(-2)day(-1), with a mean annual exergy-to-energy ratio of 0.93. (C) 2010 Elsevier Ltd. All rights reserved.Öğe Spatial viability analysis of grid-connected photovoltaic power systems for Turkey(Elsevier Sci Ltd, 2014) Çağlayan, Nuri; Ertekin, Can; Evrendilek, FatihThis paper investigates viability of 0.2, 0.5, 1, 3, 5 and 10 MW grid-connected photovoltaic (PV) power plants using 22-year data for 135 locations across Turkey and RETScreen model to predict energy production. Mean annual global solar radiation (GSR), sunshine duration (SSD), and ambient air temperature (Tair) were spatially interpolated over Turkey based on universal kriging method. The technical renewable energy potential of grid-connected solar PV in Turkey estimated for a 0.2-10 MW power plant, on average, ranged from 0.31 to 15.56 GW h m(-2) yr(-1) for a fixed system, and from 0.41 to 20.81 GW h m(-2) yr(-1) for a dual-axis tracker in direct alignment with the sun. The use of the proposed PV grid-connected power plants was found to provide the highest energy production in Osmaniye, Dalaman, and Koycegiz and the lowest energy production in Tosya, Gumushane, and Artvin. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Statistical modeling of spatio-temporal variability in monthly average daily solar radiation over Turkey(Molecular Diversity Preservation Int, 2007) Evrendilek, Fatih; Ertekin, CanThough one of the most significant driving forces behind ecological processes such as biogeochemical cycles and energy flows, solar radiation data are limited or nonexistent by conventional ground-based measurements, and thus, often estimated from other meteorological data through (geo) statistical models. In this study, spatial and temporal patterns of monthly average daily solar radiation on a horizontal surface at the ground level were quantified using 130 climate stations for the entire Turkey and its conventionally-accepted seven geographical regions through multiple linear regression (MLR) models as a function of latitude, longitude, altitude, aspect, distance to sea; minimum, maximum and mean air temperature and relative humidity, soil temperature, cloudiness, precipitation, pan evapotranspiration, day length, maximum possible sunshine duration, monthly average daily extraterrestrial solar radiation, and time (month), and universal kriging method. The resulting 20 regional best- fit MLR models (three MLR models for each region) based on parameterization datasets had R-adj(2) values of 91.5% for the Central Anatolia region to 98.0% for the Southeast Anatolia region. Validation of the best-fit MLR models for each region led to R-2 values of 87.7% for the Mediterranean region to 98.5% for the Southeast Anatolia region. The best-fit anisotropic semi-variogram models for universal kriging as a result of one-leave-out cross-validation gave rise to R-2 values of 10.9% in July to 52.4% in November. Surface maps of monthly average daily solar radiation were generated over Turkey, with a grid resolution of 500 m x 500 m.Öğe Techno-economic analysis of solar water heating systems in Turkey(Mdpi Ag, 2008) Ertekin, Can; Külcü, Recep; Evrendilek, FatihIn this study, solar water heater was investigated using meteorological and geographical data of 129 sites over Turkey. Three different collector types were compared in terms of absorber material ( copper, galvanized sheet and selective absorber). Energy requirement for water heating, collector performances, and economical indicators were calculated with formulations using observed data. Results showed that selective absorbers were most appropriate in terms of coverage rate of energy requirement for water-heating all over Turkey. The prices of selective, copper and galvanized absorber type's heating systems in Turkey were 740.49, 615.69 and 490.89 USD, respectively. While payback periods (PBPs) of the galvanized absorber were lower, net present values (NPVs) of the selective absorber were higher than the rest. Copper absorber type collectors did not appear to be appropriate based on economical indicators.Öğe Total CO2-equivalent GHG emissions from agricultural human labour in Turkey(Italian Association of Chemical Engineering - AIDIC, 2017) Adaya, Beran; Ertekin, Can; Evrendilek, FatihCarbon dioxide (CO2) is one of the most important greenhouse gases (GHG) whose increased emissions have significantly enhanced greenhouse effect, thus changing global climate. To keep up with the rising growth rates of human population and consumption in spite of decreasing agricultural human labour, finding ways to boost sustainable agricultural production through mechanization has gained importance instead of relying solely on human efforts. The present study aims at the quantification of total CO2-equivalent GHG emissions (CO2eq) from agricultural human labour required in tillage, cultivation, maintenance, harvesting, and transportation for 58 agricultural crops cultivated in Turkey. Our quantification was based on minimum and maximum values of human labour energy reported in related literature and the coefficient of 0.36 kg CO2eq per MJ. Our results showed that GHG emissions varied between 49.41 and 1232.66 Gg CO2eq for wheat, 1.44 and 72.68 Gg CO2eq for chickpea, and 49.50 and 154.43 Gg CO2eq for tomatoes. There is a pressing need for agricultural GHG emissions from human efforts and mechanization to be reduced and balanced. Copyright © 2017, AIDIC Servizi S.r.l.Öğe Türkiye'deki karasal ekosistemlerin birincil verimliliklerinin zamansal ve mekansal değişimlerinin modellenmesi(2009) Evrendilek, Fatih; Berberoğlu, Süha; Ertekin, Can; Kiliç, Şeref; Ödemiş, Berkant; Demirkesen, Ali Can-Öğe Using eddy covariance sensors to quantify carbon metabolism of peatlands: A case study in Turkey(Mdpi Ag, 2011) Evrendilek, Fatih; Karakaya, Nusret; Aslan, Güler; Ertekin, CanNet ecosystem exchange (NEE) of carbon dioxide (CO2) was measured in a cool temperate peatland in northwestern Turkey on a continuous basis using eddy covariance (EC) sensors and multiple (non-)linear regression-M(N)LR-models. Our results showed that hourly NEE varied between -1.26 and 1.06 mg CO2 m(-2) s(-1), with a mean value of 0.11 mg CO2 m(-2) s(-1). Nighttime ecosystem respiration (R-E) was on average measured as 0.23 +/- 0.09 mg CO2 m(-2) s(-1). Two best-fit M(N)LR models estimated daytime R-E as 0.64 +/- 0.31 and 0.24 +/- 0.05 mg CO2 m(-2) s(-1). Total R-E as the sum of nighttime and daytime RE ranged from 0.47 to 0.87 mg CO2 m(-2) s(-1), thus yielding estimates of gross primary productivity (GPP) at -0.35 +/- 0.18 and -0.74 +/- 0.43 mg CO2 m(-2) s(-1). Use of EC sensors and M(N) LR models is one of the most direct ways to quantify turbulent CO2 exchanges among the soil, vegetation and atmosphere within the atmospheric boundary layer, as well as source and sink behaviors of ecosystems.