Measurement of solar energy radiation in Abu Dhabi,UAE

This paper presents data on measurement of actual solar radiation in Abu Dhabi (24.43°N, 54.45°E). Global solar radiation and surface temperatures were measured and analyzed for one complete year. High resolution, real-time solar radiation and other meteorological data were collected and processed. Daily and monthly average solar radiation values were calculated from the one-minute average recorded values. The highest daily and monthly mean solar radiation values were 369 and 290 W/m², respectively. The highest one-minute average daily solar radiation was 1041 W/m². Yearly average daily energy input was 18.48 MJ/m²/day. Besides the global solar radiation, the daily and monthly average clearness indexes along with temperature variations are discussed. When possible, global solar energy radiation and some meteorological data are compared with corresponding data in other Arab state capitals. The data collected indicate that Abu Dhabi has a strong potential for solar energy capture.     

SOLAR GLOBAL AND ULTRAVIOLET RADIATION MEASUREMENTS OVER KUWAIT

Data presented here for continuous measurements of global (285-2800?nm) and ultraviolet solar radiation (295-385?nm) are on horizontal level, which have been carried out for three years in Kuwait from January 96 to December 98. The ratio of monthly daily ultraviolet to global solar radiation was found to lie between 4.07% and 5.4%. The highest and lowest intensity monthly-daily recorded values for global radiation were 9.29 and 0.45?Kwh/m² but for ultraviolet 445 and 31?Wh/m² respectively. Dependence of the global and ultraviolet solar radiation on the atmospheric humidity was investigated. Linear regression functions were obtained with coefficient of determination R²> 0.7. The decrease in ultraviolet solar radiation from 270 to 240?Wh/m² justifiably as a result of increasing the chemical pollutants SO₂ and NO₂.     

Global solar radiation estimation from measurements of visibility and air temperature extremes

Solar radiation is the main source of energy for the survival of life and its associated activities. It is important to know accurate solar radiation value in areas such as agricultural activities, solar energy systems, heating, and meteorology. In this study, we present a model for the estimation of solar radiation value with other meteorological parameters in cases where solar radiation cannot be measured or not available. This model is based on the relationship between solar radiation and measured air temperature and visibility extremes. As is known, the incident global solar radiation is attenuated by clouds, aerosols, ozone layer, water vapor, etc.. In the model, the attenuation of the solar radiation is expressed by dew point temperature, visibility, and the maximum and minimum air temperatures. Dew-point temperature refers to the effect of water vapor on solar radiation, air temperature extremes are used to signify cloudiness. Visibility also gives the effect on the attenuation of solar radiation by air pollutants and aerosols in the model. The model was applied to the data taken from meteorological stations in Turkey. Error analysis was performed and compared with the models in the literature and satisfactory results were obtained.

Abbreviations H: Daily total global solar radiation, units of MJ ? m^?2 ? day^?1; H₀: Extraterrestrial solar radiation, units of MJ ? m^?2 ? day^?1; H_m: Measured daily total global solar radiation, units of MJ ? m^?2 ? day^?1; H_c: Calculated daily total global solar radiation, units of MJ ? m^?2 ? day^?1; T_min: Daily minimum temperature, units of °C; T_max: Daily maximum temperature, units of °C; RH: T_dew: Relative humidity, units of %rh; Dew-point temperature, units of °C     

Some aspects of solar radiation climatology of Iraq

Study of the climatology of global solar radiation is considered very useful for assessing the potential efficiency of systems designed for solar energy utilization. This paper explores some aspects of solar radiation climatology in Iraq. Analysis of the monthly averages global solar radiation and the general atmospheric transparency for the period 1971–1985 for three different climatological zones (Mosul, Baghdad, Nasiriyah) are discussed. The frequency distribution of daily clearness index for each station is determined using histograms of frequencies. The percentage number of days with solar radiation and sunshine duration values below a certain value is analyzed and discussed. The period of successive days having radiation less than 5 MJ/m² · day⁻¹ and 10 MJ/m² · day⁻¹ is examined and presented graphically.     

The fluctuation of solar radiation in Thailand

Fluctuations in the daily solar radiation are examined in an unbroken 5-yr sequence of measurements at Bangkok, and are also estimated from daily sunshine measurements at Bangkok and 3 other stations in Thailand. Seasonal effects are shown by separate studies for eight $\text{1}\text{1}\text{2}$ month periods of the year defined by standard solar declination values.During the dry season in winter and spring the frequency distribution of daily totals of global solar radiation at Bangkok has a peak near 20 MJ m^?2 d^?1 and is skewed towards low values. During the wet season in summer and autumn the distribution is more dispersed. Elsewhere the distributions are similar to those at Bangkok.The time series of daily totals of global solar radiation at Bangkok is analysed as a second order random process. The observed annual frequencies of runs of consecutive days with low radiation at Bangkok are given. There are 32.0 isolated days, 9.4 pairs of days, and 3.4 runs of 3 days per year with radiation less than 12.57 MJ m^?2 d^?1. These results are adequately described by the second order theory. The runs are most likely to occur in summer and autumn. Elsewhere in Thailand the annual frequencies of the runs and their seasonal distributions are almost the same as at Bangkok, except that in the south the runs are more likely to occur later in the year.     

A study of solar ultraviolet radiation at Makkah solar station

Analysis of solar ultraviolet radiation (295–385 nm) and total global radiation (290–3000 nm), continuously recorded at a station in Makkah (21.5°N, 39.8°E) for 17 months in 1987–1988, has shown that the monthly average daily UV was 200 Wh m⁻². The ratio of UV to total global radiation varied from a maximum of 0.043 to a minimum of 0.028. A drop of 25% below the average 0.036, detected in the summer months, is attributed to scattering and absorption by dust and low tropospheric ozone. Comparison with Dhahran and Kuwait has shown that the effect was localised. A study of diurnal variation and clear, midday hourly radiation and the ratio of UV to global radiation, , also revealed an overall depletion in the summer months, despite the relative decrease in attenuation of Iv during cloudy days and at low solar altitudes. Multiple regressions of Hv and Iv on relevant variables with coefficients of determination exceeding 90% have been performed. Frequency distribution of daily UV is briefly discussed.     

The solar radiation climate of Thailand

Geographical, seasonal, and diurnal variations of global solar radiation in Thailand are surveyed. Seasonal effects are shown by separate studies for eight 1.5 month periods of the year defined by standard solar declination values. Detailed maps are given of the geographical distribution of solar radiation prepared from data on cloudiness at 44 stations, duration of sunshine at 18 stations, and linear regressions relating radiation to sunshine at Chiang Mai and Bangkok. The highest mean values are above 19.5 MJ m⁻² d⁻¹ and are widespread in spring. The lowest values are below 15.0 MJ m⁻² d⁻¹ in restricted localities with heavy rainfall in autumn.Rough estimates of diffuse solar radiation and atmospheric turbidity are made from the radiation-sunshine regression parameters. Diffuse radiation averages 8.4 MJ m⁻² d⁻¹. Turbidity at Chiang Mai is high in spring and low in summer and autumn; at Bangkok it is high throughout the year.The diurnal variation of global solar radiation determined from hourly measurements at Chiang Mai and Bangkok is analysed. The mean midday radiation fluxes range from 0.80 kW m⁻² in spring to 0.60 kW m⁻² in autumn. On the average the radiation received in the afternoon is slightly less than that received in the morning.     

Survey of the incident solar radiation in Brazil by use of meteosat satellite data

Meteosat-2 satellite data in the visible band were used to calculate monthly averages from daily mean incident solar radiation over Brazil, using the IGMK physical model for the period 1985–1986. Satellite estimates are compared with ground data from 22 national stations. The global root mean square error between model and ground results for all data points was 13%, and the mean bias error was 1.23 MJ m⁻². About 68% of the individual errors were below 10% and clustered around 8%. Global radiation estimated by the model ranged from 9.0 to 27 MJ m⁻² with the diffuse to global ratio falling into the 0.2–0.5 interval. Enhanced inverted zonal trends were found for both satellite predictions and the ground station results.     

Parameterization of a simple model to estimate monthly global solar radiation based on meteorological variables, and evaluation of existing solar radiation models for Tabouk, Saudi Arabia

Using 9 years of solar radiation data, we established a simple model to calculate the monthly mean global solar radiation on a horizontal surface in Tabouk (28.38° N, 36.6° E, Saudi Arabia). The model correlates the global solar radiation with five meteorological parameters. These parameters are the perceptible water vapor, air temperature, relative humidity, atmospheric pressure, and the mean monthly daily fraction of possible sunshine hours. The estimated global radiation from the model was compared with the measured values using the mean bias error (MBE), coefficient of correlation (R), root mean square error (RMSE), and mean percentage error (MPE). The t statistics were also applied as another indication of suitability. The model has a high coefficient of correlation (R = 0.99), MBE = −14 × 10⁻⁴ kW h/m², RMSE = 0.10 kW h/m², and MPE = −0.03%. It is believed that the model developed in this work is applicable for estimating, with great accuracy. The monthly mean daily global radiation at any site having similar conditions to those found in Tabouk.Furthermore, 29 regression models available in the literature were used to estimate the global solar radiation data for Tabouk. The selected models were different in terms of the variables they use and in the number of the variables they contained. The models were compared on the basis of the statistical errors considered above. Apart from Abdall’s model, which showed a reasonable estimate (MPE = −2.04%, MBE = −0.22 kW h/m², and RMSE = 0.59 kW h/m²), all the models under or overestimate the measured solar radiation values. Comparisons between these models and the produced model, from this study, were also considered. According to the statistical results, the model of Abdall showed the prediction closest to those estimated using the developed model.     

Solar radiation data for Beer Sheva, Israel

A number of years of data on the global irradiation incident on a horizontal surface in Beer Sheva, Israel (lat. = 31°15′N, long. = 34°48′E, elevation 240 m) have been correlated. It is apparent from these data that this locale possesses a relatively high abundance of sunshine. The average cumulative annual irradiation is 6722MJ/m² and the average daily irradiation is 18.43 MJ/m². The percentage frequency of days possessing irradiation rates greater than 20 MJ/m² is 46 per cent, whereas that possessing less than 10 MJ/m²d is 11.9 per cent. The percentage frequency of cloudy days (K_T < 0.34) is low, 7.5 per cent, whereas that for clear days (K_T > 0.65) is 29.2 per cent.     

Analysis of solar radiation measurements at Athens Observatory and estimates of solar radiation in Greece

In this paper measurements of Global (G) Solar Radiation on a horizontal surface at Athens during the 16 yr period 1960-75 are analysed. Mean annual, monthly and daily totals, the diurnal variation, frequency distribution of daily totals, frequency of occurrence of daily totals of Global Radiation less than 8.5, 17, and 34 MJ/m² for 2, 3, 4 and 5 successive days are computed and discussed.Direct Solar Radiation at normal incidence (I) is computed and analysed in a similar manner to that of Global Radiation, for the same period. Components of direct radiation of normal incidence have been computed from spot value observations at times when sky conditions permitted.Annual values of global radiation were estimated from sunshine measurements (1960-73) widely distributed throughout Greece. It is considered that this analysis of measurements should closely represent the radiation climatology of Greece.     

Contribution to the study of solar radiation in Burgos, Spain

A series of daily measurements of global solar radiation on horizontal surface realized during the period 1978–1982, in Burgos, Spain, is analysed. The mean decadic values show fluctuations, in the spring and at the beginning of the summer especially. The absolute maximums generally appear in July with values that oscillate between 23 and 26 MJ m⁻², and the minimums in January or December with values between 4 and 5 MJ m⁻². Averaging the analogous months we obtain the maximums in July with a value of 23 MJ m⁻². We have studied the elemental statistic characteristics and we remark that the interquartile range is small in the winter months and increases in the spring and summer. The number of the days in which the radiation has remained inferior to a given value, has been calculated in the frequency analysis, remarking that in the days corresponding to the period of the winter appear radiation values inferior to 10 MJ m⁻² and only 3% of July days are below this value. We have defined and determined the potential radiation and have calculated the extraterrestrial radiation in order to know the attenuation of global radiation in its passage through the atmosphere. We remark that the energy percentage transmitted by the atmosphere increases from winter to summer, a maximum value of 59% is obtained in July and a minimum of 30% in December. The atmospheric transparency without clouds oscillates between 71% in the spring and 62% in the winter.     

Long-term variability of solar direct and global radiation derived from ISCCP data and comparison with reanalysis data

Annual variations of solar radiation at the Earth’s surface may be strong and could seriously harm the return of investment for solar energy projects. This paper analyzes the long-term variability of broadband surface solar radiation based on 18 years of three-hourly satellite observations from the International Satellite Cloud Climatology Project (ISCCP). Direct normal irradiance (DNI) and global horizontal irradiance (GHI) at the surface are derived through radiative transfer calculations, using different physical input parameters describing the actual composition of the atmosphere. Validation of DNI is performed with two years of high resolution Meteosat-derived irradiance. Monthly averages show an average mean bias deviation of −1.7%. Results for DNI from the 18-year time series indicate strong and significant increases for several regions in the subtropics up to +4 W/m² per year, with exception of Australia, where a small decrease in DNI of -1 W/m² per year is observed. Inter-annual variability for DNI is very strong and sometimes exceeds 20%. Comparisons of calculations with and without volcanic aerosol reveal a decrease of up to 16% in annual averages due to volcano eruptions. Changes in GHI are much smaller and less significant. Results show a maximum increase of 0.8 W/m² per year and an annual variability of less than 4%. Volcano eruptions reduce annual averages of GHI by less than 2.2%. The two reanalysis data sets investigated differ strongly from each other and are far off the validated results derived from satellite data. Trends are weaker and less significant or even of opposite sign.     

Analysis of the solar radiation data for Beer Sheva, Israel, and its environs

The solar radiation climate of Beer Sheva, Israel, is reported upon in detail. The database utilized in this analysis consisted of global radiation on a horizontal surface, normal incidence beam radiation, and global radiation on a south-facing surface tilted at 40°. Monthly-average hourly and daily values are reported for each of these three types of measured radiations, together with the calculated monthly-average daily values for the components of the global radiation, viz. the horizontal beam and diffuse radiations. The monthly-average hourly and daily clearness index values have also been calculated and analyzed. Monthly-average daily frequency distributions of the clearness index values are reported for each month. The solar radiation climate of Beer Sheva has also been compared to those reported for a number of countries in this region. The annual-average daily global radiation incident on a horizontal surface is 18.91 MJ/m² and that for normal incidence beam radiation is 21.17 MJ/m². The annual-average daily fraction of the horizontal global radiation that is beam is 0.72. The annual-average daily value for the clearness index is 0.587 and the average frequency of clear days annually is 58.6%. We conclude, based upon the above analysis, that Beer Sheva and its environs are characterized by relatively high, average-daily irradiation rates, both global and beam, and a relatively high frequency of clear days.     

城市大气污染对到达地表的太阳辐射的影响研究

在晴空（无云）的条件下,大气污染是影响到达地球表面太阳辐射的重要因素之一。选择中国6个典型城市（北京、沈阳、上海、武汉、广州和成都）,利用2014年1月—2020年12月的空气质量日监测数据以及地面太阳辐射、日照时数等逐日观测数据,定量分析晴空条件下大气污染指数（AQI）与地表太阳总辐射、散射辐射的关系。结果表明：1）大气污染会降低清晰度指数,增加散射系数,对于地表太阳总辐射有衰减作用,对于散射辐射有增强作用。2）2014—2020年,大气污染（AQI>100）使得晴天地表太阳总辐射的年衰减总量和相对衰减量（共7 a）较大的是北京（212.40 MJ/m²,4.01%）、沈阳（184.16 MJ/m²,3.00%）、上海（123.80 MJ/m²,4.37%）和武汉（106.36 MJ/m²,3.04%）,而成都（58.03 MJ/m²,3.82%）和广州（18.76MJ/m²,0.96%）的衰减总量较小。3）大气污染（AQI>100）使得晴天散射辐射的年增加总量和相对衰减量分别是北京256.64 MJ/m²（12.96%）、沈阳134.45 MJ/m²（7.10%）、武汉22.62 MJ/m²（1.36%）、成都43.40 MJ/m²（9.71%）、上海94.74 MJ/m²（8.25%）和广州37.79 MJ/m²（5.90%）。     

Modeling of solar radiation using remote sensing and artificial neural network in Turkey

Artificial neural networks (ANNs) were used to estimate solar radiation in Turkey (26–45°E, 36–42°N) using geographical and satellite-estimated data. In order to train the Generalized regression neural network (GRNN) geographical and satellite-estimated data for the period from January 2002 to December 2002 from 19 stations spread over Turkey were used in training (ten stations) and testing (nine stations) data. Latitude, longitude, altitude, surface emissivity for ?_4, surface emissivity for ?_5, and land surface temperature are used in the input layer of the network. Solar radiation is the output. Root Mean Square Error (RMSE) and correlation coefficient (R²) between the estimated and measured values for monthly mean daily sum with ANN values have been found as 0.1630 MJ/m² and 95.34% (training stations), 0.3200 MJ/m² and 93.41% (testing stations), respectively. Since these results are good enough it was concluded that the developed GRNN tool can be used to predict the solar radiation in Turkey.     

Predicting total solar irradiation values using artificial neural networks

This study explores the possibility of developing an artificial neural networks model that could be used to predict monthly average daily total solar irradiation on a horizontal surface for locations in Uganda based on geographical and meteorological data: latitude, longitude, altitude, sunshine duration, relative humidity and maximum temperature. Results have shown good agreement between the predicted and measured values of total solar irradiation. A correlation coefficient of 0.997 was obtained with mean bias error of 0.018 MJ/m² and root mean square error of 0.131 MJ/m². Overall, the artificial neural networks model predicted with an accuracy of 0.1% of the mean absolute percentage error.     

Empirical regression models for weather data measured in Kuwait during the years 1985, 1986, and 1987

Monthly average daily measurements over a three-year period (1985–1987) for eight weather parameters are reported. The computed three-year averages of total yearly global radiation, diffuse radiation, hemispherical global infrared radiation, and global UV radiation were 1,939.08, 696.82, 3,144.30, and 87.78 kWh/m², respectively. Further, employing least-squares linear regression analysis, empirical fits expressing the monthly average daily measurements as a function of month of the year were developed for seven weather parameters.     

Monthly mean solar radiation statistics for Australia

Tables of monthly mean solar radiation parameters are computed from detailed cloud cover information. The parameters include direct and global daily total energy inputs to horizontal, inclined and “sun-tracking” surfaces. Comparison with measured global radiation at 12 stations reveals virtually no systematic error in the computation scheme, and an error of 2MJ m⁻² day⁻¹ in the worst case month of any station.     

Global,direct and diffuse solar radiation on horizontal and tilted surfaces in Jeddah,Saudi Arabia

The measured data of global and diffuse solar radiation on a horizontal surface, the number of bright sunshine hours, mean daily ambient temperature, maximum and minimum ambient temperatures, relative humidity and amount of cloud cover for Jeddah (lat. 21°42′37′′N, long. 39°11′12′′E), Saudi Arabia, during the period (1996–2007) are analyzed. The monthly averages of daily values for these meteorological variables have been calculated. The data are then divided into two sets. The sub-data set I (1996–2004) are employed to develop empirical correlations between the monthly average of daily global solar radiation fraction (H/H₀) and the various weather parameters. The sub-data set II (2005–2007) are then used to evaluate the derived correlations. Furthermore, the total solar radiation on horizontal surfaces is separated into the beam and diffuses components. Empirical correlations for estimating the diffuse solar radiation incident on horizontal surfaces have been proposed. The total solar radiation incident on a tilted surface facing south H_t with different tilt angles is then calculated using both Liu and Jordan isotropic model and Klucher’s anisotropic model. It is inferred that the isotropic model is able to estimate H_t more accurate than the anisotropic one. At the optimum tilt angle, the maximum value of H_t is obtained as ∼36 (MJ/m² day) during January. Comparisons with 22 years average data of NASA SSE Model showed that the proposed correlations are able to predict the total annual energy on horizontal and tilted surfaces in Jeddah with a reasonable accuracy. It is also found that at Jeddah, the solar energy devices have to be tilted to face south with a tilt angle equals the latitude of the place in order to achieve the best performance all year round.