Numerical methods applied to global solar radiation modeling - comparison with measured data

摘要

Purpose - The purpose of this paper is to predict the global solar radiation intensity in areas wherernmeteorological stations do not exist and information on solar radiation cannot be obtainedrnexperimentally.rnDesign/methodology/approach - The approach to achieve the objective of the paper isrndeveloping multiple regression relations between the global solar radiation intensity (the dependentrnvariable) rind geographical, geometrical, astronomical and meteorological parameters (thernindependent variables). The independent variables used for this purpose were selected based onrntheir ease of measurability outside the meteorological station and without expensive equipment. Thernnumber of independent variables is arbitrarily chosen and directly affects the accuracy of predictions.rnFindings - Linear regression relations using one, two, three, four, five, six, and seven independentrnvariables were developed to predict the global solar radiation intensity on horizontal surfaces. Anrnadvanced computer program based on least square analysis was used to obtain the regressionrncoefficients. The relations having the highest correlation coefficients were selected. The study showsrneven when only one independent variable (declination angle) is used, the one variable regressionrnrelation predicts the global solar radiation with an accuracy that is satisfactory in most engineeringrnapplications.rnOriginality/value - The diversity of regression relations introduced in this paper gives the engineerrnsuch a broad freedom of choice, that knowing only an astronomical parameter of the site makes himrncapable of estimating the global solar radiation intensity within acceptable margins. The predictedrnvalues of global solar radiation intensity by this approach can be used for the design andrnperformance estimation in solar applications. The statistical model developed in this research wasrnvalidated when compared with the measured data in Yazd airport. The measured data used tornanalyze the model equations were collected in a 13-year period. No investigation of this type existsrnhaving such degree of accuracy in geographical, geometrical, astronomical and meteorologicalrnparameters in Iran.