Estimation Of Global Solar Radiation Research Articles

Estimation of Global Solar Radiation on Horizontal Surface Using Routine Meteorological Measurements for Different Cities in Iraq

Estimation of Global Solar Radiation on Horizontal Surface Using Routine Meteorological Measurements for Different Cities in Iraq

Quality control and estimation of global solar radiation in China

Measurements of surface radiation in China are too sparse to meet demand for scientific research and engineering applications. Moreover, the radiation data often include erroneous and questionable values though preliminary quality-check has been done before the data release. Therefore, quality control of radiation data is often a prerequisite for using these data. In this study, a set of quality-check procedures were implemented to control the quality of the solar radiation measurements at 97 stations in China. A hybrid model for estimating global solar radiation was then evaluated against the controlled data. The results show that the model can estimate the global radiation with accuracy of MBE less than 1.5 MJ m −2 and RMSE less than 2.8 MJ m −2 for daily radiation and RMSE less than 2.0 MJ m −2 for monthly-mean daily radiation at individual stations over most of China except at a few stations where unsatisfactory estimates were possibly caused by severe air pollution or too dense clouds. The MBE averaged over all stations are about 0.7 MJ m −2 and RMSE about 2.0 MJ m −2 for daily radiation and RMSE about 1.3 MJ m −2 for monthly-mean daily radiation. Finally, this model was used to fill data gaps and to expand solar radiation data set using routine meteorological station data in China. This data set would substantially contribute to some radiation-related scientific studies and engineering applications in China.

Application of Sayigh “Universal Formula” for global solar radiation estimation in the Niger Delta region of Nigeria

In recent years, renewable energy utilisation in various applications has increased significantly. Applications involving solar thermal energy include air and water heating whilst solar photovoltaic systems have been installed to provide electricity for households in urban and rural areas of the developing economies. The solar radiation data are not easily available for many countries and is therefore estimated most of the times. In this work is presented the results of evaluating the Sayighr “Universal formula” for estimating the global solar radiation in the Niger Delta region of Nigeria with Umudike (longitude 7.33°E, latitude 5.29°N) as a case study. The levels of the global solar radiation which ranged from 1.99 kWh to 6.75 kWh, computed with the method are in agreement with those of earlier authors indicating that the method can be used for reproducing signatures of global solar radiation in the region when actual measurements are not available.

Evaluation of temperature-based global solar radiation models in China

Estimation of global solar radiation ( R s ) from the daily range of air temperature (Δ T) offers an important alternative in the absence of measured R s or sunshine duration because of the wide availability of air temperature data. In this paper, we assessed 16 R s models including modified versions of the Bristow and Campbell (B–C) and the Hargreaves (Harg) models across a wide range of agro-ecological conditions in China. Using long-term data from 15 sites in Northeast, North China Plain and Northwest China, we explored the main factors affecting model parameters and the predictive accuracy and proposed empirical equations to estimate these parameters. Two schemes in calculating Δ T were employed: Δ T 1 (based on single day T min) used in the Harg and Δ T 2 (based on 2-day average of T min) used in the B–C model. Results showed that the original B–C model performed similarly to the best performing modified Harg model, but significantly outperformed the original Harg model with a 4–7% higher accuracy. The common practice of fixing some parameters in the B–C model caused the most significant effect and resulted in a 3–9% lower accuracy than that of the original model. In contrast, modifications had the smallest effect and yielded little improvement and are thus unnecessary. The Δ T scheme had a moderate effect, with Δ T 1 generally resulting in a higher accuracy especially in high altitude areas. This indicates that the effect of cold or warm air advection is negligible in the B–C model even in a temperate climate. The accuracy of the temperature-based models was affected mainly by the magnitude of Δ T, with larger Δ T resulting in higher accuracy. Parameters of the B–C model correlated significantly with many commonly used geographical and meteorological factors, meaning that they are more easily obtainable without the need for calibration and consequently R s measurement. The parameter of the original Harg model correlated insignificantly with all the examined factors, meaning that it has to be calibrated. Main findings in this study are valuable in clarifying the relative impact of different approaches in applications on model accuracy, in demonstrating the advection effect, in identifying the dominant factors of model parameters and thus in increasing their availability.

Correlations for estimation of daily global solar radiation with hours of bright sunshine in Turkey

In this study, seven different empirical equations are employed to estimate the monthly average daily global solar radiation on a horizontal surface for provinces in the different regions of Turkey, using only the relative duration of sunshine. Daily global solar radiation and sunshine measurement data collected for the provinces of Turkey are obtained from the Turkish State Meteorological Service. The regression constants of the new models developed in this study are found for the provinces of Turkey, as well as that of some models given in the literature. In order to indicate the performance of the models, the statistical test methods of the mean bias error (MBE), mean absolute bias error (MABE), mean relative error (MRE), root mean square error (RMSE) and correlation coefficient (r) are used.

Estimation of daily global solar radiation in Vietnamese Mekong Delta area: A combinational application of statistical downscaling method and Bayesian inference

Estimation of daily global solar radiation in Vietnamese Mekong Delta area: A combinational application of statistical downscaling method and Bayesian inference

Atmospheric Turbidity Estimation from Hourly Global Solar Radiation Data under Cloudless Skies

We estimated monthly atmospheric turbidity from hourly observation data of global solar radiation under cloudless skies at 67 stations all over Japan. Using an empirical formula for calculating global solar radiation, we determined atmospheric turbidity as the best-fit parameter. The estimated turbidity is consistent with the observation by the Japan Meteorological Agency. Sub-nationwide increases in atmospheric turbidity, caused by forest fires or Asian dust events, are detected in time series. Some temporal changes in atmospheric turbidity are also found in a small area. Such local phenomena are hardly detectable by sparse distribution of the stations for direct solar radiation observation. The accuracy of the global solar radiation estimation can be improved by considering the seasonal variation of the turbidity. Since Angstrom’s turbidity coefficient is directly linked with the volumetric aerosol content, the present method is useful for monitoring the spatial distribution of aerosols. In addition, the present method using the densely distributed observation network of global solar radiation has an advantage in compensating for the sparseness of the current atmospheric turbidity observation in Japan.

Artificial neural network estimation of global solar radiation using air temperature and relative humidity

Measured air temperature and relative humidity values between 1998 and 2002 for Abha city in Saudi Arabia were used for the estimation of global solar radiation (GSR) in future time domain using artificial neural network method. The estimations of GSR were made using three combinations of data sets namely: (i) day of the year and daily maximum air temperature as inputs and GSR as output, (ii) day of the year and daily mean air temperature as inputs and GSR as output and (iii) time day of the year, daily mean air temperature and relative humidity as inputs and GSR as output. The measured data between 1998 and 2001 were used for training the neural networks while the remaining 240 days’ data from 2002 as testing data. The testing data were not used in training the neural networks. Obtained results show that neural networks are well capable of estimating GSR from temperature and relative humidity. This can be used for estimating GSR for locations where only temperature and humidity data are available.

Climatic influences on solar modelling in China

Correlation between clearness index and sunshine duration is useful to the estimation of the solar radiation for areas where measured solar radiation data are not available. Regression techniques were used to investigate the correlations between daily global solar radiation and sunshine duration for different climates in China. Measurements made during the 30-year period (1971–2000) from 40 measuring stations covering major thermal and solar climatic zones across China have been gathered and analysed. The correlations were developed for each individual station as well as for each of the major climates. It was found that the Angstrom–Prescott equation tended to give a good estimation of global solar radiation based on the corresponding measured sunshine hours. A simple two-parameter linear regression equation was proposed for each of the major thermal and solar climatic zones.

General Formula for Estimation of Monthly Mean Global Solar Radiation in Different Climates on the South and North Coasts of Iran

Using sunshine duration, cloud cover, relative humidity, average of maximum temperature, and ground albedo as the input of several radiation models, the monthly average daily solar radiation on horizontal surface in various coastal cities of the South (25.23∘N) and the North (38.42∘N) of Iran are estimated. Several radiation models are tested and further are revised by taking into consideration the effects of relative humidity, ground albedo, and Sun-Earth distance. Model validation is performed by using up to 13 years (1988–2000) of daily solar observations. Errors are calculated using MBE, MABE, MPE, and RMSE statistical criteria (see nomenclature) and further a general formula which estimates the global radiation in different climates of coastal regions is suggested. The proposed method shows a good agreement (less than7%deviation) with the long-term pyranometric data. In comparison with other works done so far, the suggested method performs a higher degree of accuracy for those of two regions. The model results can be extended to other locations in coastal regions where solar data are not available.

Estimation of global solar radiation in arid and semi-arid climates of East and West Iran

Abstract In Iran, most of the models used so far, have provided solar estimation for a few specific locations based on the short-term solar observations. Using different radiation models, (e.g. Sabbagh, Paltridge–Proctor, Daneshyar) and various input parameters (e.g. cloud cover, sunshine duration, relative humidity, temperature, and altitude) we developed a general height-depended formula for the prediction of the direct and diffuse monthly average daily solar radiation for 64 mountainous arid and semi-arid locations in West and East Iran. The models mentioned are modified and new coefficients are defined for the diffuse component based on the long-term observed diffuse data. Model results are validated against up to 13-year daily solar observations at 10 solar radiation sites. In comparison with the previous studies, the newly developed method performs more accurate estimation (less than 3% MPE error) in the arid and semi-arid regions. Comparison of the model results indicates that calibration of the coefficients made to the diffuse formula against the longer period experimental data can improve the estimations of global solar radiation.

A new simple parameterization of daily clear-sky global solar radiation including horizon effects

Estimation of clear-sky global solar radiation is usually an important previous stage for calculating global solar radiation under all sky conditions. This is, for instance, a common procedure to derive incoming solar radiation from remote sensing or by using digital elevation models. In this work, we present a new model to calculate daily values of clear-sky global solar irradiation. The main goal is the simple parameterization in terms of atmospheric temperature and relative humidity, Angstrom's turbidity coefficient, ground albedo and site elevation, including a factor to take into account horizon obstructions. This allows us to obtain estimates even though a free horizon is not present as is the case of mountainous locations. Comparisons of calculated daily values with measured data show that this model is able to provide a good level of accurate estimates using either daily or mean monthly values of the input parameters. This new model has also been shown to improve daily estimates against those obtained using the clear-sky model from the European Solar Radiation Atlas and other accurate parameterized daily irradiation models. The introduction of Angstrom's turbidity coefficient and ground albedo should allow us to use the increasing worldwide aerosol information available and to consider those sites affected by snow covers in an easy and fast way. In addition, the proposed model is intended to be a useful tool to select clear-sky conditions.

A critical review on the estimation of daily global solar radiation from sunshine duration

Abstract Models such as the Angstrom–Prescott equation are used to estimate global solar radiation from sunshine duration. In the literature, researchers investigate either the goodness of the model itself or the goodness of the estimation of global solar radiation based on a set of statistical parameters such as R2, RMSE, MBE, MABE, MPE and MAPE. If the former is the objective, then the statistical analysis should naturally be based on H/Ho − S/So (the ratio of daily solar radiation to extraterrestrial daily solar radiation vs. the ratio of sunshine duration to day length). If the latter is investigated, then the statistical analysis should be based on Hc − Hm (calculated daily solar radiation vs. measured daily solar radiation). A literature survey undertaken in the present article showed that these two data sets are apt to be confused, drawing the statistical parameters to be used in assessment of the estimation model from the latter data set or the vice versa set. The statistical parameters are clearly derived from the basics for both of the data sets, and the inconsistencies caused by this confusion and other factors are exposed. A case study of the estimation models and global solar radiation estimation from sunshine duration is presented using five different models (linear, quadratic, cubic, logarithmic and exponential), which are the most common models used in the literature, based on 6 years long measured hourly global solar radiation data.

05/02615 Statistical validation of daylength definitions for estimation of global solar radiation in Toledo, Spain

05/02615 Statistical validation of daylength definitions for estimation of global solar radiation in Toledo, Spain

Sunshine and global solar radiation estimation at different sites in Egypt

A simple non-linear method is proposed for estimating relative sunshine duration based on monthly mean daily maximum and minimum air temperatures and cloud cover fraction at six sites in Egypt, where long-term period (9–15 years) data were recorded. This method gives low errors (mean bias error is about −0.4% and root mean square is about 2.3% for pooled data), so it can be used in case of unavailability of sunshine duration data. Also, a non-linear equation has been proposed at the same sites to estimate monthly mean daily global radiation based on observed and estimated values of relative sunshine duration. This method was compared with linear Ångström–Prescott and double linear of Garg–Garg equation. These methods were tested seasonally and at different sky conditions (clear, partially cloudy and overcast skies). Also they have been tested against 32 stations dataset, at worldwide sites. The results show that the bias error for the proposed method is low, average values to mean bias error and root mean square error are around 0.1% and 6%, respectively, while they are around 3% and 7% to the other methods at pooled data. Generally, the proposed method preformed better than the others.

Estimating solar radiation for crop modeling using temperature data from urban and rural stations

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 29:233-243 (2005) - doi:10.3354/cr029233 Estimating solar radiation for crop modeling using temperature data from urban and rural stations T. Mavromatis1,*, S. S. Jagtap2 1Department of Meteorology–Climatology, School of Geology, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece2Department of Agricultural and Biological Engineering, University of Florida, Gainesville, Florida 32611, USA *Email: thmavrom@geo.auth.gr ABSTRACT: Lack of site-specific global solar radiation (GSR) data is a significant impediment for most crop model applications. First, several empirical methods for estimating GSR from observed maximum and minimum temperature were evaluated using data from urban (National Climatic Data Center [NCDC] data set) and rural (Florida Automated Weather Network [FAWN] data set) sites in Florida. Next, the spatial structure of empirical model parameters was investigated and the possibility of employing spatially interpolated coefficients developed at urban or rural sites to predict solar radiation at rural locations, where most crops are grown and often crop modeling is required to address various issues, was assessed. Finally, the effects of observed and estimated GSR on simulated potential yield and evapotranspiration with CROPGRO-Peanut and CERES-Maize models at 6 crop–location combinations were evaluated. The model developed by Donatelli and Bellocchi (DB) achieved the most accurate estimations of GSR across Florida. The quality of those predictions varied with environment setting (urban-rural) and latitude. RMSE (root mean square error) between observed and fitted daily GSR were in the range of 3.1–4.1 and 3.2–4.9 MJ m–2 d–1 for FAWN and NCDC evaluation sub-sets, respectively. Radiation for FAWN sites was efficiently estimated by the coefficients interpolated from rural sites but was substantially overestimated by 17.6%, on monthly basis, when urban sites supplied the model empirical parameters. NCDC sites were site specific and suitable sources of solar radiation at urban environments only. Input of estimated with the DB model GSR into a crop model would be a realistic option at sites where only temperature and precipitation are available. KEY WORDS: Solar radiation estimation · Air temperature · RadEst · Crop simulation models · Urban–rural stations · Florida Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 29, No. 3. Online publication date: October 17, 2005 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2005 Inter-Research.

04/02894 Global solar radiation estimation using sunshineduration in Spain: Almorox, J. and Hontoria, C. Energy Conversion and Management, 2004, 45, (9–10), 1529–1535

04/02894 Global solar radiation estimation using sunshineduration in Spain: Almorox, J. and Hontoria, C. Energy Conversion and Management, 2004, 45, (9–10), 1529–1535

Statistical validation of daylength definitions for estimation of global solar radiation in Toledo, Spain

The different daylength calculation procedures that can be employed to estimate solar radiation using an Angstrom–Prescott regression have not been sufficiently evaluated. In this study, daily global solar radiation data measured in Toledo (Spain) during the period 1986–1995 were used to test five daylength estimation models using different definitions of sunrise/sunset and twilight. Models were compared using the root mean square error (RMSE), the mean bias error (MBE) and the t-statistic. In the first two cases, the differences found between the results from the different models were small. Analysis using the t-statistic, on the other hand, showed that the use of civil twilight to calculate daylength produced the best estimates of global solar radiation for Toledo.

On the estimation of global and diffuse solar radiation over Egypt

Measurements of global, H, diffuse, D, solar radiation on a horizontal surface and sunshine duration, n, at nine meteorological stations have been used to examine the validity of some methods of the estimate global and diffuse solar radiation. In order to improve the obtained results, for prediction purposes, the investigated area of Egypt has been divided into five regions represented by the nine selected stations (in cold and hot seasons). An appropriate regional parameter, K, of an empirical relation of Barbaro et al. has been determined for each region. The agreement between measurement and estimated values is remarkable. The maximum possible error of estimated values does not exceed 9.6%. It is seen that the modified formula gives precise estimations for global solar radiation at any Egyptian locality. Relation between the diffuse fraction, D/H, and the relative duration of sunshine, n/N, are also determined for each region. Good agreement between the measured and estimated values applying the obtained relations has been found. Therefore, the relations are recommended for use at any location in Egypt. A comparative study for the global and diffuse solar radiation over different sites in Egypt has been made.

Generation of typical solar radiation data for ?stanbul, Turkey

Typical solar radiation data are very important as input in modelling, designing and performance evaluation of solar energy applications. In this study, typical solar radiation data were obtained for İstanbul, Turkey both from measured data and synthetic generation. Firstly, a test reference year for daily global solar radiation on a horizontal surface was generated using 19 years measured data. The daily global solar radiation as typical data for İstanbul was presented throughout a year in a tabular form. Secondly, the daily global solar radiation for İstanbul was expressed with a trigonometric equation using long-term measured data. It is expected that the typical data and the equation derived will be useful to the designers of solar energy systems as well as those who need to have fairly good estimates of daily global solar radiation for İstanbul. Copyright © 2003 John Wiley & Sons, Ltd.