The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Zekai Şen - One of the best experts on this subject based on the ideXlab platform.
-
Probabilistic innovative Solar Irradiation estimation
International Journal of Energy Research, 2016Co-Authors: Zekai ŞenAbstract:Summary Often, Solar Irradiation estimation from simply measureable sunshine duration data is achieved by linear and nonlinear regression expressions, which depicts the statistical regression equation between the sunshine duration and Solar Irradiation data. These models are based on statistical parameters only, and therefore, the estimations do not take into consideration deviations from the averages. In this paper, an innovative probability methodology is proposed for Solar Irradiation estimation, which is based on the cumulative probability distribution functions (CDFs) of the sunshine duration and Solar Irradiation data. For this purpose, the sunshine duration data are converted to match the Solar Irradiation data cumulative distribution (CDF), which is then employed for the Solar Irradiation estimation. Hence, the CDFs of sunshine duration and Solar Irradiation data are preserved, and rather than global average, pointwise Solar Irradiation estimations are achieved. The application of the innovative probabilistic methodology is presented for seven Solar Irradiation measurements stations from different climate regions in Turkey. It is shown that the suggested method over performs other methodologies with very high improvements. Copyright © 2016 John Wiley & Sons, Ltd.
-
HARmonic–LINear (HarLin) model for Solar Irradiation estimation
Renewable Energy, 2015Co-Authors: Yavuz Selim Güçlü, İsmail Dabanlı, Eyüp Şişman, Zekai ŞenAbstract:Abstract The Solar energy has potential future effectiveness in a variety of areas and it helps to decrease the dominance of fossil fuels, which cause atmospheric pollution, global warming and climate change impacts. In the literature, there are different methodologies for its modeling, but this study suggests the harmonic analysis application to Solar Irradiation and sunshine duration data for more refined relevant prediction of Solar Irradiation. The basis of the methodology is combined application of the HARmonic and the classical LINear regression analyses, and therefore, it is referred to as the HarLin model. It isolates first the periodicity from the daily averages of records and then the linear regression analysis is applied elegantly to first order stationary data. The results are tested and compared with the Adaptive-Neuro Fuzzy Inference System (ANFIS) model based on the Sugeno fuzzy logic inference system and Angstrom–Prescott model in the form of a linear regression analysis. In the application, three Solar Irradiation sites are considered from different Solar energy potential locations in Turkey, namely, at Adana, Gaziantep and Silifke cities. The predictions by the HarLin model appear more successful than ANFIS and the classical Angstrom–Prescott approaches.
-
Solar Irradiation estimation by monthly principal component analysis
Energy Conversion and Management, 2008Co-Authors: Zekai Şen, Şükrü Murat CebeciAbstract:Simple Solar Irradiation estimation models most often use classical regression analysis with a set of restrictive assumptions. They work with actual measurements on Cartesian coordinate systems, and given the predictor as sunshine duration, the Solar Irradiation amount is estimated through a regression model. The variances of Solar Irradiation and sunshine data are not considered explicitly whereas they are physically significant in representing diffusion, absorption and reflection of the Solar Irradiation depending on the atmospheric composition and weather situation, especially, in terms of cloudiness, which is directly related to sunshine duration during day light. This paper proposes more efficient approach in terms of physical interpretations and mathematical convenience in modeling Solar Irradiation and sunshine duration relationship. For this purpose, two dimensional principal component analysis is employed and the Solar Irradiation estimations are found more reliably than the classical approaches. The application of the methodology is presented for five sunshine duration and Irradiation record stations in Turkey.
-
Simple nonlinear Solar Irradiation estimation model
Renewable Energy, 2007Co-Authors: Zekai ŞenAbstract:A simple nonlinear model with three parameters is proposed for global Solar Irradiation estimation from sunshine duration ratio measurements. Two of the parameters have almost the same interpretations for extreme weather conditions as in the classical Angstrom model but the third parameter appears as the power of the sunshine duration ratio. This model reduces to the classical Angstrom equation when power is equal to one. It contains the possible nonlinear effects in Solar Irradiation and sunshine duration relationship as a first-order mathematical approximation to the linear Angstrom equation. Power values different than one imply nonlinear models. The model parameter estimates are achieved through the nonlinear least-squares analysis. The application of the methodology is performed for eight Irradiation measurement stations in Turkey.
-
Spatial interpolation and estimation of Solar Irradiation by cumulative semivariograms
Solar Energy, 2001Co-Authors: Zekai Şen, Ahmet Duran ŞahinAbstract:The main purpose of this paper is to find a regional procedure for estimating the Solar Irradiation value of any point from sites where measurements of Solar global Irradiation already exist. The spatial weights are deduced through the regionalized variables theory and the cumulative semivariogram (CSV) approach. The CSV helps to find the change of spatial variability with distance from a set of given Solar Irradiation data. It is then employed in the estimation of Solar Irradiation value at any desired point through a weighted average procedure. The number of adjacent sites considered in this weighting scheme is based on the least squares technique which is applied spatially by incrementing nearest site numbers successively from one up to the total site number. The validity of the methodology is first checked with the cross validation technique prior to its application to sites with no Solar Irradiation records. Hence, after the cross-validation each site will have different number of nearest adjacent sites for spatial interpolation. The application is achieved for monthly Solar Irradiation records over Turkey by considering 29 measurements stations. It has been shown that the procedure presented in this paper is better than the classical techniques such as the inverse distance or inverse distance square approaches.
Ahmet Duran Şahin - One of the best experts on this subject based on the ideXlab platform.
-
Vertically Solar Irradiation exergy changes in the different layers of atmosphere
International Journal of Exergy, 2011Co-Authors: Mustafa Kemal Kaymak, Ahmet Duran ŞahinAbstract:The thermodynamic characteristics of Solar Irradiation in the different layers of atmosphere are investigated from a perspective based on exergy. It is known that the main energy source of photovoltaic (PV) cells, Solar power satellites and Solar thermal devices is the Solar irradiance incident on modules. To evaluate the exergy efficiency of PV cells, therefore, firstly we need the exergy of the total Solar Irradiation for considered locations. In this paper, firstly changes of temperature and Solar Irradiation in the vertical structure of the atmosphere would be considered and after that Solar exergy values for different altitudes are estimated. Especially on the upper layers of the atmosphere, Solar Irradiation potential is higher than in the lower levels, but considering, higher temperature gradient between stratosphere and thermosphere causes important heat losses in PVs along with efficiency decreasing. In addition, vertically temperature gradient decreasing in the troposphere causes increasing Solar exergy values.
-
Relationship between drought and Solar Irradiation variables
Hydrological Processes, 2008Co-Authors: Sevinc Sirdas, Ahmet Duran ŞahinAbstract:Drought prediction for in many regions of the world has critical importance for strategic planning agriculture and water management. The occurrence of droughts cannot be predicted with certainty and thus must be treated as random variables. It is the main purpose of this paper to develop a new concept of drought features assessments based on triple drought related hydrometeorological and meteorological variables, namely, rainfall, Solar Irradiation and sunshine duration. Equal standard rainfall lines are drawn as a map with two reference variables as Solar Irradiation and sunshine duration. These are referred to as the triple graphical method (TGM) approach. It furnishes rich features of drought behaviour variation based on the rainfall, Solar Irradiation and sunshine duration. This analysis and the Solar Irradiation estimation method are applied to seven climatologically different stations in the Republic of Turkey for the monthly data period 1982-1991. The linear relations between drought and the variables of the Angstrom equation are found between 55% and 94% without Trabzon. Drought and Angstrom equation parameters are estimated by the proposed methodology. Relations between monthly drought and Angstrom equation variables are presented by the triple Solar-drought graphical method. TGM provides information about the drought occurrences for different combinations of Solar Irradiation and sunshine duration. TGM graphs help to identify not only precipitation surplus (wet spells) or deficits (dry spells droughts) but also their variations with two more meteorological variables as Solar Irradiation and sunshine duration.
-
A new formulation for Solar Irradiation and sunshine duration estimation
International Journal of Energy Research, 2007Co-Authors: Ahmet Duran ŞahinAbstract:In Solar engineering and atmospheric sciences Solar Irradiation and sunshine duration estimations are very important for different problems. Classical approaches that based on Angstrom equation for estimating global Solar Irradiation in terms of sunshine duration are abundant in the literature. Most of them include linear and lesser extent slightly nonlinear relationships between these two variables. Parameters are determined invariably by the least squares technique leading to regression lines or curves as models. None of these models provides within year variations in the parameters and they are all very rigid in applications yielding single global Solar Irradiation estimation for a given data set. In this paper, relation between extraterrestrial variables (length of day and Solar Irradiation) ratio and terrestrial variables (measured sunshine duration and Solar Irradiation) ratio is taken into account. This is a novel approach and has no restrictive assumptions. Decreasing amount of extraterrestrial variables ratio can be evaluated by subtracting measured terrestrial variables ratio (sunshine duration/total Solar Irradiation) from theoretical variables ratio. Differences between these ratios give atmospheric effects on length of day and extraterrestrial Solar Irradiation. The differences are represented by a parameter which helps to estimate easily the seasonal average parameter values without the application of the least square method. The main idea of this paper is to suggest not only a novel but also a practical formulation for Solar Irradiation and sunshine duration estimations. Its application is presented for three stations in Turkey and it is seen that better estimations are evaluated by proposed method than Angstrom method. Copyright © 2006 John Wiley & Sons, Ltd.
-
Spatial interpolation and estimation of Solar Irradiation by cumulative semivariograms
Solar Energy, 2001Co-Authors: Zekai Şen, Ahmet Duran ŞahinAbstract:The main purpose of this paper is to find a regional procedure for estimating the Solar Irradiation value of any point from sites where measurements of Solar global Irradiation already exist. The spatial weights are deduced through the regionalized variables theory and the cumulative semivariogram (CSV) approach. The CSV helps to find the change of spatial variability with distance from a set of given Solar Irradiation data. It is then employed in the estimation of Solar Irradiation value at any desired point through a weighted average procedure. The number of adjacent sites considered in this weighting scheme is based on the least squares technique which is applied spatially by incrementing nearest site numbers successively from one up to the total site number. The validity of the methodology is first checked with the cross validation technique prior to its application to sites with no Solar Irradiation records. Hence, after the cross-validation each site will have different number of nearest adjacent sites for spatial interpolation. The application is achieved for monthly Solar Irradiation records over Turkey by considering 29 measurements stations. It has been shown that the procedure presented in this paper is better than the classical techniques such as the inverse distance or inverse distance square approaches.
K. Afshar - One of the best experts on this subject based on the ideXlab platform.
-
Time series analysis and short-term forecasting of Solar Irradiation, a new hybrid approach
Swarm and Evolutionary Computation, 2017Co-Authors: N. Bigdeli, M. Salehi Borujeni, K. AfsharAbstract:Abstract In this paper, nonlinear time series analysis and short-term prediction of Solar Irradiation were considered, simultaneously. The proposed methodology is to employ time series analysis methods as well as swarm and evolutionary algorithms in conjunction with well-known regression, fuzzy and neural network model structures to develop a simple but efficient and applicable model for Solar Irradiation forecasting. The employed experimental data was the hourly Solar Irradiation of Qazvin city in Iran for five years. At first, the Solar Irradiation data was normalized using the daily clear sky Irradiation data which is an annually periodic time series. Then, the properties of normalized Solar Irradiation were characterized via time series analysis methods such as recurrence plots, autocorrelation and mutual information analysis. Based on these analyses, each year was divided into two seasons, the sunny and cloudy seasons which are noticeably different in dynamics. Next, a hybrid but simple model was developed to predict the Solar Irradiation in different seasons. For the sunny season, an optimized multivariate regression model was proposed; and for the cloudy season a bi-level model consisting of an optimized regression model and ANFIS was developed. The model parameters were tuned optimally by various evolutionary algorithms being GA, PSO, ABC, COA, and flower pollination algorithm (FPA). A Fourier-type model was also developed for modeling of the clear sky data. The results showed the out-performance of FPA method in tuning of the model parameters and convergence time. Besides, the performance of the proposed bi-level model was evaluated in comparison with some other model structures such as artificial neural networks, ANFIS networks, LSE-regression models, LS-support vector machines model, etc. The results showed that the proposed method performs considerably better than the other methods in forecasting the Solar Irradiation time series in both sunny and cloudy seasons.
Edward M. Lungu - One of the best experts on this subject based on the ideXlab platform.
-
Bivarate models: relationships between Solar Irradiation and either sunshine duration or extremum temperatures
Renewable Energy, 2003Co-Authors: Pushpendra Kumar Jain, Edward M. Lungu, Jagdish PrakashAbstract:Abstract The Republic of Botswana is one of the sunniest countries in Southern Africa. It has very little cloud cover, insufficient rainfall, very low humidity, and very low wind speed throughout the year for most parts of the country. The daily extremum temperatures appear to be very much related to Solar Irradiation which in turn depends on sunshine duration. In Botswana, Solar Irradiation on a horizontal surface is measured only at Sebele, but sunshine duration and extremum temperatures are measured at several locations throughout the country. This paper presents bivariate models that relate Solar Irradiation to sunshine duration, and Solar Irradiation to extremum temperatures for Sebele, Botswana. Autocorrelation analysis revealed that the Solar Irradiation series is stationary for d=2 and D=0, sunshine duration series is stationary for d=0 and D=0, while the extremum temperatures series are stationary for either d=0 and D=N where N=1, 2, . . . or d=1 and D=1. It is found that there is a lag of three months between the peaks of the differenced series of fractional sunshine duration and fractional Solar Irradiation. On the other hand it is found that there is at most a lag of one month between the peaks of the differenced series of maximum temperature and Solar Irradiation, and that there is no lag between the peaks of the differenced series of minimum temperature and Solar Irradiation. Analysis of the noise component revealed that the bivariate processes under consideration behaved either as a purely seasonal MA processes of order (0,1,1) or as ARIMA processes of order (0, 1, 1)×(0, 1, 1)12 or as a purely nonseasonal, autoregressive process of order 2. We claim that the relationships found for Sebele can be applied to estimate Solar Irradiation at other locations with climatic conditions similar to Botswana.
-
Stochastic models for sunshine duration and Solar Irradiation
Renewable Energy, 2002Co-Authors: Pushpendra Kumar Jain, Edward M. LunguAbstract:Harmonic analysis of sunshine duration and Solar Irradiation measured at Sebele, Botswana is carried out. The data used consists of the monthly averages and the Julian-days averages of sunshine duration and Solar Irradiation sequences. This study involves splitting the time series into deterministic and stochastic components, and determining the proportion of the variance explained by each component. The stochastic component is analyzed for persistence using the Box and Jenkins technique. It is found that the stochastic component for monthly averages Solar radiation series is best described by the second-order autoregressive Markov process, while that for Julian-days averages series has no memory.
Antonio F. Miguel - One of the best experts on this subject based on the ideXlab platform.
-
Solar Irradiation in diffusely enclosures with partitions
Applied Energy, 2010Co-Authors: Antonio F. Miguel, Ana Maria SilvaAbstract:This paper presents an approach to obtain the income of Solar Irradiation within partitioned enclosures partially transparent to Solar radiation. This model is mathematically exact and it is function of the outside Solar Irradiation, the orientation of the enclosure, the properties of the enclosure envelope, the geometry and properties of partitions. From the physical point of view it is founded on the assumption that the envelope and partitions surfaces are fully diffusive and that the radiation diffused through the atmosphere is fully isotropic. The model was applied to assess the Solar Irradiation at the ground of a hemicylindrical tunnel fitted with inclined partitions. The results of this study demonstrate, among other things, that: (i) the Solar Irradiation inside the enclosure, with any cladding material and with any orientation, is mainly determined by the transmittance of the partitions and to a lesser extent by its reflectance, (ii) the Solar radiation inside an enclosure with highly transparent partitions (i.e., transmittance > 0.5) is noticeable influenced by its orientation, but for a lower transmittance the influence of orientation becomes negligible; and (iii) to prevent the overheating within the enclosure it is advisable to install partitions with a low transmittance and a high absorptance on their surface facing downward
-
Solar Irradiation Inside a Single-span Greenhouse with Shading Screens
Journal of Agricultural Engineering Research, 1994Co-Authors: Antonio F. Miguel, Ana Maria Silva, Rui RosaAbstract:Abstract A model is offered which yields the Solar Irradiation at the ground of a single-span greenhouse fitted with screens, in terms of the outside Solar Irradiation, the position of the sun, the optical properties of the cladding and screening surfaces, the geometry of the screening surface and orientation of the axis of the greenhouse. The model is mathematically exact. From the physical point of view it is founded on the assumption that both the cladding and the screening surfaces are fully diffusive and the radiation diffused through the atmosphere and by the ground is fully isotropic. The importance of the geometry and of the optical properties of the screen in blocking the admission of Solar Irradiation inside are indicated. It is found that the Solar Irradiation inside a greenhouse, with any given cladding material, with any orientation and fitted with shading screens, is mainly determined by the transmittance of the screening surface and to a lesser extent by its reflectance. The collected radiation increases with the transmittance of the screening surface and for a given transmittance, with the reflectance of both the bottom side and topside of the screen. It is also found that a screening surface forming a closed cavity with the inside ground is always more efficient in blocking the admission of Solar Irradiation than any other shape.
